(4,4-DIFLUOROBUT-3-ENYLTHIO)-SUBSTITUTED HETEROCYCLIC OR CARBOCYCLIC RING COMPOUNDS HAVING PESTICIDAL ACTIVITY

Abstract: A compound of formula (I), or a salt thereof, wherein n is 0, 1 or 2; and R is a group of formulae (II) to (XXI), wherein: the S(O)nCH2CH2CH=CF2 group is at least one of R1 (when attached to a carbon atom), R2, R3, R4, R5 or R6; R1 (when attached to a carbon atom), R2, R3, R4, R5 and R6 are each independently hydrogen, optionally substituted alkyl, optionally substituted alkenyl, alkynyl, cycloalkyl, alkylcycloalkyl, alkoxy, alkenyloxy, alkynyloxy, hydroxyalkyl, alkoxyalkyl, optionally substituted aryl, optionally substituted arylalkyl, optionally substituted heteroaryl, optionally substituted heteroarylalkyl, optionally substituted aryloxy, optionally substituted arylalkoxy, optionally substituted aryloxyalkyl, optionally substituted heteroaryloxy, optionally substituted heteroarylalkoxy, optionally substituted heteroaryloxyalkyl, haloalkyl, haloalkenyl, haloalkynyl, haloalkoxy, haloalkenyloxy, haloalkynyloxy, halogen, hydroxy, cyano, nitro, -NR7R8, -NR7COR8, -NR7CSR8, -NR7SO2R8, -N(SO2R7)(SO2R8), -COR7, -CONR7R8, -alkylCONR7R8, CR7NR8, -COOR7, -OCOR7, -SR7, -SOR7, SO2R7, -alkylSR7, -alkylSOR7, -alkylSO2R7, -OSO2R7, -SO2NR7R8, -CSNR7R8, SiR7R8R9, -OCH2CO2R7, -OCH2CH2CO2R7, -CONR7SO2R8, -alkylCONR7SO2R8, -NHCONR7R8, -NHCSNR7R8, or an adjacent pair of R1, R2, R3, R4, R5 and R6 when taken together form a fused 5- or 6-membered carbocyclic or heterocyclic ring; R1 (when attached to a nitrogen atom) is hydrogen, optionally substituted alkyl, cycloalkyl, alkylcycloalkyl, hydroxyalkyl, alkoxyalkyl, optionally substituted aryl, optionally substituted arylalkyl, optionally substituted aryloxyalkyl, optionally substituted heteroaryl, optionally substituted heteroarylakyl, optionally substituted heteroaryloxyalkyl, haloalkyl, hydroxy, cyano, nitro, -NR7R8, -NR7COR8, NR7CSR8, -NR7COOR8, -NR7SO2R8, -N(SO2R7)(SO2R8), -COR7, -CONR7R8, -alkylCONR7R8, -CR7NR8, -COOR7, -OCOR7, -SOR7, -SO2R7, -alkylSR7, -alkylSOR7, -alkylSO2R7, -OSO2R7, -SO2NR7NR8, -SR7, -SOR7, -SO2R7, -CSNR7R8, -SiR7R8R7, -OCH2CO2R7, -OCH2CH2CO2R7, -CONR7SO2R8, -alkylCONR7SO2R8, -NHCOR7R8, or -NHCSR7R8; and R7, R8 and R9 are each independently hydrogen, optionally substituted alkyl, optionally substituted alkenyl, alkynyl, optionally substituted aryl or optionally substituted arylalkyl, haloalkyl, haloalkenyl, haloalkynyl, halogen, or hydroxy.

Description: (4, 4-D1 fl uorobut-3-eny1 t 1 o)-subst1 tuted heterocycl i c or carbocycl l c ri ng compounds havi ng pestl cldal activity The present invention relates to novel heterocyclic and phenyl derivatives having nematicidal. insecticidal and acaricidal activity, to processes for their preparation, to compositions containing them, and to methods for killing or controlling nematode. insect or acarid pests using them. According to the present invention there is provided a compound of formula (I), or a salt thereof, wherein n is 0, 1 or 2; and R is a group of formula (II) to (XXI), wherein: the S(0)nCH2CH2CH=CF2 group is at least one of Rl (when attached to a carbon atom), Rl R3, R4, R5 or R6; Rl (when attached to a carbon atom), R2, R3, R4, R5 and R6 are each independently hydrogen, optionally substituted alkyl, optionally substituted alkenyl, alkynyl, cycloalkyl, alkylcycloalkyl, alkoxy, alkenyloxy, alkynyloxy, hydroxyalkyl, alkoxyalkyl, optionally substituted aryl, optionally substituted arylalkyl, optionally substituted heteroaryl, optionally substituted heteroarylalkyl, optionally substituted aryloxy, optionally substituted arylalkoxy, optionally substituted aryloxyalkyl, optionally substituted heteroaryloxy, optionally substituted heteroarylalkoxy, optionally substituted heteroaryloxyalkyl, haloalkyl, haloalkenyl, haloalkynyl, haloalkoxy, haloalkenyloxy, haloalkynyloxy, halogen, hydroxy, cyano, nitro, -NR7R8, -NR7COR8, - R7CSR8, -NR7S02R8, -N(S02R7)(S02R8), -COR7, -CONR7R8, -alkylCONR7R8, -CR7NR8, -COOR7, -OCOR7, -SR7, -SOR7, -S02R7, -alkylSR7, -alkylSOR7, -alkylS02R7, -OS02R7, -S02NR7R8, -CSNR7R8, -SiR7R8R9, -OCH2C02R7, -OCH2CH2C02R7, -CONR7S02R8, -alkylCONR7S02R8, -NHCONR7R8, -NHCSNR7R8, or an adjacent pair of Rl, R2, R3. R4, R5 and R6 when taken together form a fused 5- or ^ 6-membered carbocyclic or heterocyclic ring; Rl (when attached to a nitrogen atom) is hydrogen, optionally substituted alkyl, cycloalkyl, alkylcycloalkyl, hydroxyalkyl, alkoxyalkyl, optionally substituted aryl, optionally substituted arylalkyl, optionally substituted aryloxyalkyl, optionally substituted heteroaryl, optionally substituted heteroarylalkyl, optionally substituted heteroaryloxyalkyl, haloalkyl, hydroxy, cyano. nitro. -NR7R8, -NR7COR8. NR7CSR8, -NR7COOR8. -NR7S02R8. -N(S02R7)(S02R8), -COR7, -CONR7R8, -alkylCONR7R8, -CR7NR8, -COOR7, -OCOR7, -SOR7. -S02R7, -alkylSR7, -alkylSOR7, -alkylS02R7, -OS02R7, -S02NR7NR8, -SR7. -SOR7, -S02R7, -CSNR7R8. -SiR7R8R7, -OCH2C02R7, -OCH2CH2C02R7, -CONR7S02R8. -alkylCONR7S02R8. - NHCOR7R8, or -NHCSR7R8: and R7, R8 and R9 are each independently hydrogen, optionally substituted alkyl, optionally substituted alkenyl, alkynyl, optionally substituted aryl, optionally substituted arylalkyl, haloalkyl, haloalkenyl, haloalkynyl, halogen, or hydroxy. We would explain that, for ease of reference only, the substituents on the R group have been named in accordance with their position on this R group. For example, when R has the formula (II), substituents R2, R3, R4 and R5 are in positions 2, 3, 4, and 5, respectively, on the ring. For the avoidance of doubt, the -S(0)nCH2CH2CH=CF2 group can be at any of the substituent positions indicated by Rl (when attached to a carbon atom) to R6. When any one of Rl to R9 is an alkyl group, or contains an alkyl moiety, it may be straight or branched chain and is preferably Cl-6 alkyl, even more preferably Cl-4 alkyl, for example methyl, ethyl, propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl or t-butyl. When the alkyl group is acting as a "linking" group, ie R-alkyl- , for example in R-alkylSR7, Cl-4 alkyl or C 1-2 alkyl are particularly preferred. When any one of Rl to R8 is a substituted alkyl group, or contains a substituted alkyl moiety, it may comprise one or more subsitutents chosen from halogen, nitro, cyano, - COOR7 or a salt thereof, hydroxy, alkoxy, alkoxyimino, alkoxycarbonyl, carbamoyl, mono- or di-alkylcarbamoyl, amino, mono- or di-alkylamino, acylamido (preferably Cl-6 acylamido), alkanesulfonyl, and arylsulfonyl, which may itself be substituted with halogen, alkoxy or nitro. When any one of Rl to R8 is an alkenyl or alkynyl group, or contains an alkenyl or alkynyl moiety, it may be straight or branched chain and is preferably C2-6 alkenyl or C2-6 alkynyl, even more preferably C2-4 alkenyl or C2-4 alkynyl, for example vinyl, allyl, but-3-enyl, 3-methyl-but-3-enyl, ethynyl or propargyl. When any one of Rl to R8 is a substituted alkenyl group, or contains a substituted alkenyl moiety, it may comprise one or more subsitutents chosen from halogen, COOR7 or a salt thereof, hydroxy, nitro and cyano. When any one of Rl to R6 is a cycloalkyl or alkylcycloalkyl group, or contains a cycloalkyl or alkylcycloalkyl moiety, it is preferably C3-6 cycloalkyl or C4-7 alkylcycloalkyl, for example, cyclopropyl, cyclopentyl, cyclohexyl or methylcyclopropyl. When any one of Rl to R6 is an alkoxy, alkenyloxy, alkynyloxy or alkoxyalkyl group, or contains such a moiety, it is preferably Cl-6 alkoxy, for example, methoxy, ethoxy, n-propoxy, iso-propoxy, n-butoxy, iso-butoxy, sec-butoxy and t-butoxy; C2-6 alkenyloxy, for example, vinyloxy, allyloxy, but-3-enyloxy and 3-methylbut-3-enyloxy; C2-6 alkynyloxy, for example, propargyloxy; C2-6 monoalkoxyalkyl, for example, methoxymethyl, methoxyethyl and ethoxymethyl; or C3-6 dialkoxyalkyl, for example, dimethoxymethyl and diethoxymethyl. When any one of Rl to R9 is aryl, or contains an aryl moiety, it is preferably C6-10 aryl, more preferably it is phenyl. When any one of Rl to R9 is arylalkyl, it is preferably C6- 10 aryl-methyl or C6-10 aryl-ethyl, even more preferably benzyl or phenethyl. When any one of Rl to R6 is heteroaryl, or contains a heteroaryl moiety, it is preferably a 5 or 6 membered ring containing at least one O, N or S atom as the heteroatom, for example, pyridine, pyrrole, pyrazine, furan or thiophene. When any one of Rl to R6 is heteroarylalkyl, it is preferably heteroaryl-Cl-2 alkyl. When any one of Rl to R9 is a substituted aiyl, arylalkyl, heteroaryl, or heteroarylalkyl group, it may comprise one or more substituents chosen from alkyl, alkoxy, haloalkyl, halogen, hydroxy, COOR7 (or a salt thereof), aminosulfonyl, cyano or nitro. Examples of these groups are 4-methylphenyl, 4-chlorophenyl, 4-fluorophenyl, 4-nitrophenyl, 3-trifluoromethylphenyl, 4-trifluoromethylphenyl, 4-aminosulfonylphenyl, 4-chlorobenzyl, 4-fluorobenzyl, 3-trifluoromethylbenzyl, 4-trifluoromethylbenzyl, 4-nitrobenzyl and 4-methylbenzyl. When any one of Rl to R6 is a aryloxy or arylalkoxy group, it is preferably phenoxy, benzyloxy or phenethoxy. When any one of Rl to R6 is a substituted aryloxy, arylalkoxy, heteroaryloxy or heteroarylalkoxy group, it may comprise one or more substituents chosen from alkyl, alkoxy, haloalkyl, hydroxy, cyano or nitro. Examples of these groiφs are 4-methylphenoxy, 4-chlorophenoxy, 4-fluorophenoxy, 4-nitrophenoxy, 3-rtfluoromethylphenoxy, 4-trifluoromethylphenoxy 4-chlorobenzyloxy, 4-fluorobenzyloxy, 3-trifluoromethylbenzyloxy, 4-trifluoromethylbenzyloxy, 4-nitrobenzyloxy and 4-methylbenzyloxy. When any one of Rl to R9 is halogen, or contains a halogen moiety, it is preferably fluorine, chlorine, bromine or iodine. Even more preferably, it is fluorine, chlorine or bromine. When any one of Rl to R9 is a haloalkyl, haloalkenyl or haloalkynyl group, it may contain one or more halogen atoms, preferably chlorine, fluorine or bromine. Examples of these groiφs are fluoromethyl, difluoromethyl, trifluoromethyl, chloromethyl, dichloromethyl, trichloromethyl, 2-fluoroethyl, 2,2,2-trifluoroethyl, pentafluoroethyl, 2,2-difluoroethenyl, 3,3-dichloroprop-2-enyl, 2-chloroprop-2-enyl, 3,4,4-trifluorobut-3-enyl, 4-fluorobut-3-enyl, 4,4-difluorobut-3-enyl and 3-methyl-4,4-difluorobut-3-enyl. When any one of Rl to R6 is a haloalkoxy group, a haloalkenyloxy group or a haloalkynyloxy group, it may contain one or more halogen atoms, preferably chlorine, fluorine or bromine. Examples of the preferred Cl-6 alkoxy, C2-6 alkenyloxy and C2-6 alkynyloxy groups are trichloromethoxy, fluoromethoxy, difluoromethoxy, trifluoromethoxy, 2-fluoroethoxy, 2,2,2-trifluoroethoxy, pentafluoroethoxy, 1,1,2,2-tetrafluoroethoxy, 2,2-difluoroethenyloxy, 3,4,4-trifluorobut-3-enyloxy, 4-fluorobut-3-enyloxy, 4,4-difluorobut-3-enyloxy, 3-methyl-4,4-difluorobut-3-enyloxy, 2-chloroprop-2-enyloxy and 3,3-dichloroprop-2-enyloxy. When any one of Rl to R6 is the group -NR7R8, it is preferably -NH2; a mono- alkylamino group, for exanφle, methylamino and ethylamino; or a di-alkylamino group, for example, dimethylamino and diethylamino. When any one of Rl to R6 is the group -NR7COR8, it is preferably -NHCHO; a C2-6 acylamino groiφ, for example -NHCOCH3, -NHCOC2H5; or benzamido, which may be substituted with one or more substituents chosen from halogen, for example, chlorine, fluorine and bromine; alkyl, for example, methyl and ethyl; alkoxy, for example, methoxy and ethoxy; haloalkyl, for example, chloromethyl, fluoromethyl, trifluoromethyl and 2,2,2-trifluoroethyl; haloalkoxy, for example, trifluoromethoxy and 2,2,2-trifluoroethoxy; hydroxy; cyano and nitro. When any one of Rl to R6 is -NR7CSR8, R7 and R8 are preferably alkyl, for example methyl and ethyl. When any one of Rl to R6 is the group -NR7S02R8, it is preferably an alkanesulfonamido group, for example, -NHS02CH3 and -NHS02C2H5. When any one of Rl to R6 is the group -N(S02R7χS02R8), it is preferably a di-(alkanesulfonyl)amino group, for example, -N(S02CH3)2 and -N(S02C2H5)2. When any one of Rl to R6 is the group -COR7, it is preferably a Cl-6 acyl group; or an optionally substituted benzoyl group. The benzoyl may be substituted with one or more substituents chosen from halogen, for example, chlorine, fluorine and bromine; alkyl, for example, methyl and ethyl; alkoxy. for exanφle, methoxy and ethoxy; haloalkyl, for example, chloromethyl, fluoromethyl, trifluoromethyl and 2,2,2-trifluoroethyl; haloalkoxy, for example, trifluoromethoxy and 2,2,2-trifluoroethoxy; hydroxy; cyano and nitro. Examples of preferred -COR7 groiφs are acetyl, propionyl, n-butanoyl, 4-chlorobenzoyl, 4-fluorobenzoyl, 4-bromobenzoyl, 4-methylbenzoyl and 4-trifluoromethylbenzoyl. When any one of Rl to R6 is the group -CONR7R8, it is preferably -CONH2; an N-alkyl-carboxamido group, for example -CONHCH3, -CONHC2H5 and -CONHCH2CH2CH3; or an N,N-dialkyl-car »oxamido group, for example -CON(CH3)2, -C0N(CH3XC2H5) and -CON(C2H5)2. When any one of Rl to R6 is the group -alkylCONR7R8, it is preferably -Cl-4 alkylCONR7R8. When any one of more of Rl to R6 is the group -CR7NR8, it is preferably -CH=NOR When any one of Rl to R6 is the group -COOR7, it is preferably -COOH; an alkoxycarbonyl group, for example methoxycarbonyl and ethoxycarbonyl; or a haloalkenyloxycarbonyl group, for exanφle 3,4,4-trifluorobut-3-enyloxycarbonyl, 4-fluorobut-3-enyloxycarbonyl, 4,4-difluorobut-3-enyloxycarbonyl and 3-methyl- ,4-difluorobut-3-enyloxycarbonyl. When any one of Rl to R6 is the group -OCOR7, it is preferably a C2-6 acyloxy group, for example -OCOCH3 and -OCOC2H5; or an optionally substituted benzoyloxy group. The benzoyloxy group may comprise one or more substituents chosen from halogen, for example, chlorine, fluorine and bromine; alkyl, for example, methyl and ethyl; alkoxy, for example, methoxy and ethoxy; haloalkyl, for example, chloromethyl, fluoromethyl, trifluoromethyl and 2,2,2-trifluoroethyl; haloalkoxy, for exanφle, trifluoromethoxy and 2,2,2-trifluoroethoxy; hydroxy; cyano; and nitro. When any one of Rl to R6 is the group -SR7, R7 is preferably hydrogen, optionally subsituted alkyl, optionally substituted alkenyl, alkynyl, haloalkyl, haloalkenyl, haloalkynyl, optionally substiuted aryl, or optionally substituted arylalkyl. Examples of the preferred Cl-6 alkylthio (Cl-4 alkyl being especially preferred), C2-6 alkenylthio or C2-6 alkynylthio groiφs are methylthio, ethylthio, n-propylthio, iso-propylthio, n-butylthio, iso-butylthio, sec-butylthio, t-butylthio, allylthio, but-3-enylthio, 3-methylbut-3-enylthio and propargylthio. Examples of the preferred Cl-6 haloalkylthio (Cl-4 alkyl being especially preferred), C2-6 haloalkenylthio or C2-6 halbalkynylthio groiφs are fluoromethylthio, difluoromethylthio, trifiuoromethylthio, trichloromethylthio, 2-fluoroethylthio, 2,2,2-trifluoroethylthio, 3-fluoro-n-propylfhio, pentafluoroethylthio, 2-chloroprop-2-enylthio, 3,3-dichloroprop-2-enylthio, 3,4,4-trifluorobut-3-enylthio, 4-fluorobut-3-enylthio, 4,4-difluorobut-3-enylthio and 3-methyl-4,4-difluorobut-3-enylthio. An exanφle of the preferred C6-10 arylthio and C6-10 aryl-Cl-2alkylthio groiφs is 3-trifluoromethylbenzylthio. When any one of Rl to R6 is the group -SOR7, it is preferably an alkanesulfinyl, alkenylsulfinyl or alkynylsulflnyl group, for example methanesulfinyl or ethanesulfinyl; or a haloalkanesulfinyl, haloalkenylsulfinyl or haloalkynylsulfinyl group, for exanφle trifluoromethanesulfinyl. In another preferred embodiment -SOR7 is preferably -SOF, -SOBr or -SOC1. When any one of Rl to R6 is the group -S02R7, it is preferably an alkanesulfonyl, alkenylsulfonyl, alkynylsulfonyl, a haloalkanesulfonyl, haloalkenylsulfonyl, haloalkynylsulfonyl group; or an optionally substituted benzenesulfonyl group. The benzenesulfonyl groiφ may comprise one or more substituents chosen from halogen, for example, chlorine, fluorine and bromine; alkyl, for example, methyl and ethyl; alkoxy, for example, methoxy and ethoxy; haloalkyl, for example, chloromethyl, fluoromethyl, trifluoromethyl and 2,2,2-trifluoroethyl; haloalkoxy such as trifluoromethoxy and 2,2,2-trifluoroethoxy; hydroxy; cyano and nitro. Examples of such groiφs are methanesulfonyl, ethanesulfonyl, trifluoromethanesulfonyl, and 4-methylbenzenesulfonyl. In another preferred embodiment -S02R7 is preferably -S02F, -S02Br or -S02C1. It will thus be appreciated that the R group of formula (II) to (XXI) can comprise more than one -S(0)nCH2CH2CH=CF2 group. Preferably the R group contains one or two such substituents. When any one of Rl to R6 is the group -0S02R7, it is preferably an alkanesulfonyloxy group or an optionally substituted benzenesulfonyloxy group. The benzenesulfonyl may be substituted with one or more substituents chosen from halogen, for example, chlorine, fluorine and bromine; alkyl, for exanφle, methyl and ethyl; alkoxy, for example, methoxy and ethoxy; haloalkyl, for example, chloromethyl, fluoromethyl, trifluoromethyl and 2,2,2-trifluoroethyl; haloalkoxy, for example, trifluoromethoxy and 2,2,2-trifluoroethoxy; hydroxy; cyano; and nitro. When any one of Rl to R6 is the group -S02NR7R8, it is preferably -S02NH2; an alkylaminosulfonyl group, for example, -S02NHCH3 and -S02 HC2H5; or a dialkylaminosulfonyl group, for example, -S02N(CH3)2 and -S02N(C2H5)2. When any one of Rl to R6 is the group -CSNR7R8 it is preferably -CSNH2, -CS HCH3 or -CSN(CH3)2. When any one of Rl to R6 is the group -SiR7R8R9, it is preferably a trialkylsilyl group, for example, trimethylsilyl and triethylsilyl. When any one of Rl to R6 is the group -OCH2C02R7, it is preferably an alkoxycarbonylmethoxy group, for exanφle, methoxycarbonylmethoxy and ethoxycarbonylmethoxy. When any one of Rl to R6 is the group -OCH2CH2C02R7, it is preferably a alkoxycarbonylethoxy group, for example, methoxycarbonylethoxy and ethoxycarbonylethoxy. When any one of Rl to R6 is the group -CONR7S02R8, it is preferably an N-alkanesulfonylcarboxamido group or an N- alkyl-N-alkanesulfonylcarboxamido group, for example, N-(methanesulfonyl)-carboxamido and N-methyl-N-(methanesulfonyl)carboxamido. When any one or more of Rl to R6 is the group -alkylCONR7S02R8, R7 and R8 are preferably alkyl groiφs, for exanφle, ethyl and methyl. When any one of Rl to R6 is -NHC0 R7R8, R7 and R8 are preferably alkyl groiφs, for example, ethyl and methyl. When any one of Rl to R6 is -NHCSNR7R8, R7 and R8 are preferably alkyl groiφs, for example, ethyl and methyl. When an adjacent pair of Rl, R2, R3, R4, R5 and R6 taken together form a fused 5- or 6-membered carbocyclic or heterocyclic ring, preferably containing two oxygen atoms, the pair of substituents taken together is preferably -(CH2)3-, -(CH2)4-, -CH=CH-CH=CH-, -0-CH2-0-, optionally substituted with one or two halogen atoms or methyl groiφs, for example -0-CHF-O- or -0-CF2-0-, -0-CH(CH3)-0-, -0-C(CH3)2-0- or -0-(CH2)2-0-. According to an especially preferred embodiment of the present invention Rl (when attached to a carbon atom) to R6 are each independently hydrogen; nitro; halogen; cyano; -CH=NOH; Cl-4 alkyl; Cl-4 haloalkyl; Cl-4 alkenyl; Cl-4 haloalkenyl; cyclopropyl; hydroxy; Cl-4 alkoxy; C2-4 alkoxyalkyl; -COOH; C2-4 alkoxycarbonyl; C2-4 Iialoalkenyloxycarbonyl; -CONH2; mono or di-Cl-2 alkylaminocarbonyl; C2-4 alkanecaπ onyl; -CONHS02 Cl-4 alkyl, preferably -CONHS02CH3; phenyl optionally mono- or di- substituted with groiφs independently chosen from halogen, nitro, Cl-4 alkyl, Cl-4 alkoxy or aminosulfonyl; beri2yl optionally mono- or di- substituted with groiφs independently chosen from halogen, nitro, Cl-4 alkyl or Cl-4 alkoxy; phenoxy optionally mono- or di- substituted with groups independently chosen from halogen, cyano, Cl-4 alkyl or Cl-4 alkoxy; amino optionally mono- or di- substituted with Cl-4 alkyl groiφs; -SH; Cl-4 alkylthio; benzylthio optionally mono- or di- substituted with groiφs independently chosen from halogen or Cl-4 haloalkyl; Cl-4 alkenylthio; C2-4 haloalkenylthio; a second S(0)nCH2CH2CH=CF2 group; Cl-4 alkanesulfonyl; Cl-4 haloalkanesulfonyl; fluorosulfonyl; mono- or di- Cl-4 alkylsulfamoyl; a 5 or 6 membered heteroaryl group, for example, furyl, pyrazinyl, pyridinyl or thienyl, optionally substituted with halogen; or any adjacent pair forms a fused 5- or 6- carbocyclic or heterocyclic ring; and Rl (when attached to a nitrogen atom) is hydrogen; nitro; cyano; -CH=NOH; Cl-4 alkyl; Cl-4 haloalkyl; cyclopropyl; hydroxy; -COOH; C2-4 alkoxycarbonyl; C2-4 haloalkenyloxycarbonyl; -CONH2; mono or di-Cl-2 alkylaminocarbonyl; C2-4 alkanecarbonyl; -CONHS02 Cl-4 alkyl, preferably -CONHS02CH3; phenyl optionally mono- or di- substituted with groups independently chosen from halogen, nitro, Cl-4 alkyl, Cl-4 alkoxy or aminosulfonyl; benzyl optionally mono- or di- substituted with groiφs independently chosen from halogen, nitro, Cl-4 alkyl or Cl-4 alkoxy; phenoxy optionally mono- or di- substituted with groiφs independently chosen from halogen, cyano, Cl-4 alkyl or Cl-4 alkoxy; amino optionally mono- or di- substituted with Cl-4 alkyl groups; -SH; Cl-4 alkylthio; benzylthio optionally mono- or di- substituted with groiφs independently chosen from halogen or Cl-4 haloalkyl; Cl-4 alkenylthio; C2-4 haloalkenylthio; a second S(0)nCH2CH2CH=CF2 group; Cl-4 alkanesulfonyl; Cl-4 haloalkanesulfonyl; fluorosulfonyl; mono- or di- Cl-4 alkylsulfamoyl; a 5 or 6 membered heteroaryl group, for example, furyl, pyrazinyl, pyridinyl or thienyl, optionally substituted with halogen. The following Tables give examples of compounds according to the invention. Examples of compounds of Formula (II) according to the invention are set out in Table π. TABLE π Examples of compounds of Formula (HI) according to the invention are set out in Table HI. Examples of compounds of Formula (TV) according to the invention are set out in Table IV. R5 5-SCH2CH2CH=CF2 5-SOCH2CH2CH=CF2 5-S02CH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2. 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 Examples of compounds of Formula (V) according to the invention are set out in Table V. 4-SCH2CH2CH=CF2 5-CF3 4-SOCH2CH2CH=CF2 5-CF3 4-SCH2CH2CH=CF2 5-Cl 4-SOCH2CH2CH=CF2 5-Cl 4-S02CH2CH2CH=CF2 5-Cl 4-SCH2CH2CH F2 5-CN 4-SCH2CH2CH=CF2 5-CN 4-SOCH2CH2CH=CF2 5-CN 4-S02CH2CH2CH=CF2 5-CN 4-SCH2CH2CH=CF2 5-CONH2 4-SCH2CH2CH=CF2 5-CONH2 4-SCH2CH2CH=CF2 5-COOCH2CH3 4-SCH2CH2CH=CF2 5-COOCH3 4-S02CH2CH2CH=CF2 5-COOCH3 4-SCH2CH2CH=CF2 5-COOH 4-SCH2CH2CH=CF2 5-F 4-SCH2CH2CH F2 5-H 4-SOCH2CH2CH=CF2 5-H 4-S02CH2CH2CH=CF2 5-H 4-SCH2CH2CH=CF2 5-N02 4-SCH2CH2CH=CF2 5-S02F 4-SCH2CH2CH=CF2 5-S02NH2 4-Br 5-SCH2CH2CH=CF2 4-C6H5 5-SCH2CH2CH=CF2 4-CF3 5-SCH2CH2CH=CF2 4-CF3 5-S02CH2CH2CH=CF2 4-C1 5-SCH2CH2CH=CF2 4-CN 5-SCH2CH2CH=CF2 4-CN 5-SOCH2CH2CH=CF2 4-CN 5-S02CH2CH2CH=CF2 4-CN 5-SCH2CH2CH=CF2 4-CONH2 5-SCH2CH2CH=CF2 4-CONH2 5-SOCH2CH2CH=CF2 5-SCH2CH2CH F2 5-SCH2CH2CH=€F2 5-SCH2CH2CH=CF2 Exaπφles of compounds of Formula (VQ) according to the invention are set out in Table VII. 5-Cl 5-Cl 5-Cl 5-Cl 5-Cl 5-CN 5-CN 5-CN 5-CN 5-CN 5-CONH2 5-CONH2 5-CONH2 5-COOCH2CH3 5-COOCH2CH3 5-COOCH2CH3 5-COOCH3 5-COOCH3 5-COOCH3 5-COOH 5-COOH 5-N02 5-N02 5-N02 5-S02F 5-S02F 5-S02F 5-S02NH2 5-S02NH2 5-S02N(CH2CH3)2 Vπ.57 2-H 4-SCH2CH2CH=CF2 5-H Vπ.58 2-H 4-SOCH2CH2CH=CF2 5-H Vπ.60 2-H 4-SCH2CH2CH=CF2 5-Br Vπ.61 2-H 4-SCH2CH2CH=CF2 5-C6H5 Vπ.62 2-H 4-SOCH2CH2CH=CF2 5-C6H5 Vπ.63 2-H 4-SCH2CH2CH=CF2 5-CF3 Vπ.64 2-H 4-SOCH2CH2CH=CF2 5-CF3 Vπ.65 2-H 4-SCH2CH2CH=CF2 5-Cl Vπ.66 2-H 4-SOCH2CH2CH=CF2 5-Cl Vπ.67 2-H 4-S02CH2CH2CH=CF2 5-Cl Vπ.68 2-H 4-SCH2CH2CH=CF2 5-CN Vπ.69 2-CH3 4-SCH2CH2CH=CF2 5-CN Vπ.70 2-CH3 4-SOCH2CH2CH=CF2 5-CN Vπ.71 2-CH3 4-S02CH2CH2CH r2 5-CN Vπ.72 2-H 4-SCH2CH2CH=CF2 5-CONH2 Vπ.73 2-CH3 4-SCH2CH2CH=CF2 5-CONH2 Vπ.74 2-H 4-SCH2CH2CH=CF2 5-COOCH2CH3 Vπ.75 2-CH3 4-SCH2CH2CH=CF2 5-COOCH3 Vπ.76 2-CH3 4-S02CH2CH2CH=CF2 5-COOCH3 Vπ.77 2-H 4-SCH2CH2CH=CF2 5-COOH Vπ.78 2-H 4-SCH2CH2CH=CF2 5-F Vπ.79 2-H 4-SCH2CH2CH=CF2 5-N02 Vπ.80 2-H 4-SCH2CH2CH=CF2 5-S02F Vπ.81 2-H 4-SCH2CH2CH=CF2 5-S02NH2 Vπ.82 2-H 4-H 5-SCH2CH2CH=CF2 Vπ.83 2-H 4-H 5-SOCH2CH2CH=CF2 Vπ.84 2-H 4-H 5-S02CH2CH2CH=€F2 Vπ.85 2-H 4-Br 5-SCH2CH2CH=CF2 Vπ.86 2-H 4-C6H5 5-SCH2CH2CH=CF2 Vπ.87 2-H 4-CF3 5-SCH2CH2CH=CF2 Vπ.88 2-H 4-CF3 5-S02CH2CH2CH=CF2 Vπ.89 2-H 4-C1 5-SCH2CH2CH=CF2 Vπ.123 2-COOCH2CH3 4-H 5-SCH2CH2CH=CF2 Vπ.124 2-COOCH3 4-CH3 5-SCH2CH2CH=CF2 Vπ.125 2-COOH 4-H 5-SCH2CH2CH=CF2 Vπ.126 2-F 4-H 5-SCH2CH2CH=CF2 Vπ.127 2-F 4-H 5-SOCH2CH2CH=CF2 Vπ.128 2-NH2 4-H 5-SCH2CH2CH=CF2 Vπ.129 2-N02 4-H 5-SCH2CH2CH=CF2 Vπ.130 2-0(4-CN-C6H4) 4-H 5-SCH2CH2CH=CF2 Vπ.131 2-S02F 4-H 5-SCH2CH2CH=CF2 Vπ.132 2-S02NH2 4-H 5-SCH2CH2CH=CF2 Vπ.133 2-S-(2)-(5-Cl ' azole) 4-H 5-SCH2CH2CH=CF2 Vπ.134 2-SCH2CH2CH=€F2 4-dihydro 5-dihydro Examples of compounds of Formula (VIII) according to the invention are set out in Table VIII. TABLE VIII R4 R5 4-H 5-H 4-H 5-H 4-H 5-H 4-H 5-H 4-H 5-H 4-H 5-H 4-H 5-H 4-H 5-H 4-H 5-H 4-H 5-H 4-H 5-H 4-H 5-H 4-H 5-H 4-H 5-H 4-H 5-H 4-H 5-H 4-H 5-H ■ oo '-Λ j-. » t >-- oo >~α σ t ι -p-. ) N) -- , oo E K E E ffi Q Q Ω X X Ω Ω Ω Ω Ω Q X X ώ Xώ Xώ ώX ώX Xώ gX gX 2 g 2 g 2 g 232 g 2 g δ δ 5 OOtOO/SόaO/lD COf-fZ/Sό OΛ\ 5-Cl 5-CN 5-CN 5-CN 5-CN 5-CN 5-CN 5-CONH2 5-CONH2 5-CONH2 5-COOCH2CH3 5-COOCH2CH3 5-COOCH2CH3 5-COOCH2CH3 5-COOH 5-COOCH3 5-COOCH3 5-F 5-H 5-H 5-H 5-H a a a a I a I u I o I a I a I o I a I a I a I a I I N CN aCN a I CN a I I CN aCN a I CN a I a I CN CN a I CN CN CN CN CN CN CN C CN a I CN a I CN a I CN CN CN u 3u3 3u3 3u3 3u3 3u3 3u3 3u3 3u3 3u3 HuU 3u3 3u3 u33 3u3 3u3 u33 3u3 3u3 3u3 3u3 u33 OO OO OO OO OO OO O O^ ON ON O^ OS O O^ O O -^ o—; o'—; -©^ —© ^o 4-CN 5-S02CH2CH2CH=CF2 4-CN 5-SCH2CH2CH=CF2 4-C6H5 5-SCH2CH2CH=CF2 4-C00CH2CH3 5-SCH2CH2CH=CF2 4-C00CH2CH3 5-S0CH2CH2CH=CF2 4-C00CH2CH3 5-S02CH2CH2CH=CF2 4-C00CH3 5-SCH2CH2CH=CF2 4-C00H 5-SCH2CH2CH=CF2 4-C0NH2 5-SCH2CH2CH=CF2 4-C0NH2 5-SOCH2CH2CH=CF2 4-C0NH2 5-S02CH2CH2CH=CF2 4-C0NH2 5-SCH2CH2CH=CF2 4-C1 5-SCH2CH2CH=CF2 4-F 5-SCH2CH2CH=CF2 4-Br 5-SCH2CH2CH=€F2 4-S02NH2 5-SCH2CH2CH=CF2 4-S02F 5-SCH2CH2CH=CF2 4-N02 5-SCH2CH2CH=CF2 4-N02 5-S0CH2CH2CH=CF2 4-CF3 5-SCH2CH2CH=CF2 4-CF3 5-S02CH2CH2CH=CF2 4-H 5-SCH2CH2CH=CF2 4-H 5-S0CH2CH2CH=CF2 4-H 5-S02CH2CH2CH=CF2 4-H 5-SCH2CH2CH=CF2 4-CH3 5-SCH2CH2CH=CF2 4-H 5-SCH2CH2CH=CF2 4-H 5-SOCH2CH2CH=CF2 4-H 5-S02CH2CH2CH=€F2 4-H 5-SCH2CH2CH=CF2 4-CH3 5-SCH2CH2CH=CF2 4-H 5-SCH2CH2CH=CF2 4-H 5-SCH2CH2CH=CF2 4-H 5-S0CH2CH2CH=CF2 4-H 5-S02CH2CH2CH=CF2 4-CH3 5-S02CH2CH2CH=€F2 4-H 5-SCH2CH2CH=CF2 4-H 5-SCH2CH2CH=CF2 4-H 5-SOCH2CH2CH=CF2 4-H 5-SCH2CH2CH F2 4-H 5-SCH2CH2CH=CF2 4-H 5-SCH2CH2CH=CF2 4-H 5-SCH2CH2CH=CF2 4-H 5-SCH2CH2CH=CF2 5-S02CH2CH2CH=€F2 -CH=CH-CH=CH- -CH=CH-CH=CH- Examples of compounds of Formula (IX) according to the invention are set out in Table IX 5-SCH2CH2CH :F2 5-S0CH2CH2CH F2 5-S02CH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SOCH2CH2CH=€F2 5-S02CH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SOCH2CH2CH-CF2 5-S02CH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SOCH2CH2CH=CF2 5-S02CH2CH2CH=CF2 5-SCH2CH2CH=CF2 4-H 5-SOCH2CH2CH=€F2 4-H 5-S02CH2CH2CH=CF2 4-H 5-SCH2CH2CH F2 4-H 5-S0CH2CH2CH :F2 4-H 5-S02CH2CH2CH-CF2 4-H 5-SCH2CH2CH=€F2 4-H 5-SOCH2CH2CH-CF2 4-H 5-S02CH2CH2CH=€F2 4-H 5-SCH2CH2CH=CF2 4-H 5-SOCH2CH2CH=CF2 4-H 5-S02CH2CH2CH=CF2 4-H 5-SCH2CH2CH=CF2 4-H 5-SOCH2CH2CH=CF2 4-H 5-S02CH2CH=CF2 4-C1 5-SCH2CH2CH=CF2 4-C1 5-S0CH2CH2CH=€F2 4-C1 5-S02CH2CH2CH=CF2 4-Br 5-SCH2CH2CH=€F2 4-Br 5-SOCH2CH2CH=CF2 4-Br 5-S02CH2CH2CH=€F2 4-C00C2H5 5-SCH2CH2CH=CF2 4-C00C2H5 5-S0CH2CH2CH=CF2 4-C00C2H5 5-S02CH2CH2CH=CF2 4-COOCH(CH3)2 5-SCH2CH2CH=CF2 4-COOCH(CH3)2 5-S0CH2CH2CH=€F2 4-C00CH(CH3)2 5-S02CH2CH2CH=CF2 4-COOH 5-SCH2CH2CH-CF2 4-COOH 5-S0CH2CH2CH=CF2 4-C00H 5-S02CH2CH2CH=CF2 4-C0NH2 5-SCH2CH2CH=CF2 4-C0NH2 5-S0CH2CH2CH=CF2 4-C0NH2 5-S02CH2CH2CH=CF2 4-CN 5-SCH2CH2CH=CF2 4-CN 5-S0CH2CH2CH=CF2 4-CN 5-S02CH2CH2CH-CF2 4-S02F 5-SCH2CH2CH=CF2 4-S02F 5-S0CH2CH2CH=CF2 4-S02F 5-S02CH2CH2CH=CF2 4-S02NH2 5-SCH2CH2CH=€F2 4-S02NH2 5-S0CH2CH2CHKΪ2 4-S02NH2 5-S02CH2CH2CH=CF2 4-H 5-SCH2CH2CH=€F2 4-H 5-SOCH2CH2CH=CF2 4-H 5-S02CH2CH2CH=CF2 4-C1 5-SCH2CH2CH-CF2 4-C1 5-S0CH2CH2CH=CF2 4-C1 5-S02CH2CH2CH=CF2 4-1 5-SCH2CH2CH=CF2 4-1 5-SOCH2CH2CH=CF2 4-1 5-S02CH2CH2CH=CF2 4-C00C2H5 5-SCH2CH2CH=CF2 4-C00C2H5 5-SOCH2CH2CH=CF2 4-COOC2H5 5-S02CH2CH2CH=CF2 4-COOH 5-SCH2CH2CH=CF2 4-COOH 5-S0CH2CH2CH=CF2 4-COOH 5-S02CH2CH2CH=CF2 4-C0NH2 5-SCH2CH2CH=CF2 4-C0NH2 5-S0CH2CH2CH-CF2 4-C0NH2 5-S02CH2CH2CH=CF2 4-CN 5-SCH2CH2CH=CF2 4-CN 5-S0CH2CH2CH=CF2 4-CN 5-S02CH2CH2CH=CF2 4-S02F 5-SCH2CH2CH=CF2 4-S02F 5-S0CH2CH2CH=€F2 4-S02F 5-S02CH2CH2CH=€F2 4-S02NH2 5-SCH2CH2CH=CF2 5-SOCH2CH2CH=CF2 5-S02CH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-S0CH2CH2CH=CF2 5-S02CH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-S0CH2CH2CH=CF2 5-S02CH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-S0CH2CH2CH=CF2 5-S02CH2CH2CH=CF2 5-SCH2CH2CH-CF2 5-SOCH2CH2CH-CF2 5-S02CH2CH2CHOF2 5-H 5-H 5-H 5-Cl 5-Cl 5-Cl 5-CN 5-CN 5-CN 5-C00C2H5 5-C00C2H5 5-COOC2H5 5-CF3 5-CF3 5-CF3 5-CH3 5-CH3 5-CH3 5-C6H5 5-C6H5 5-C6H5 5-(2-Thienyl) 5-(2-Thienyl) 5-(2-Thienyl) 5-SCH2CH2CH=€F2 5-SOCH2CH2CH=CF2 5-S02CH2CH2CH=CF2 5-SCH2CH2CH=€F2 5-SOCH2CH2CH=CF2 5-S02CH2CH2CH=CF2 4-C00C2H5 5-SCH2CH2CH=CF2 4-COOC2H5 5-SOCH2CH2CH-CF2 4-COOC2H5 5-S02CH2CH2CH=CF2 4-COOH 5-SCH2CH2CH=CF2 4-COOH 5-SOCH2CH2CH=CF2 4-COOH 5-S02CH2CH2CH=CF2 4-C1 5-SCH2CH2CH=CF2 4-C1 5-SOCH2CH2CH=CF2 4-C1 5-S02CH2CH2CH=CF2 4-S02F 5-SCH2CH2CH=CF2 4-S02F 5-SOCH2CH2CH=€F2 4-S02F 5-S02CH2CH2CH=CF2 4-H 5-SCH2CH2CH=CF2 4-H 5-SOCH2CH2CH=CF2 4-H 5-S02CH2CH2CH=CF2 4-CN 5-SCH2CH2CH=€F2 4-CN 5-SOCH2CH2CH=CF2 4-CN 5-S02CH2CH2CH=CF2 4-COOC2H5 5-SCH2CH2CH=CF2 4-COOC2H5 5-SOCH2CH2CH=CF2 4-COOC2H5 5-S02CH2CH2CH F2 4-COOH 5-SCH2CH2CH=CF2 ϊ MM yI yI ro ro S S MM ϊ K MM MM H Ml \J^i r^ ≠^ MM MM K MM S MM H MM S MM u u u u u u u u u u u u u u u u u u u u u u 4-H 5-S02CH2CH2CH=CF2 4-H 5-SCH2CH2CH=CF2 4-H 5-S0CH2CH2CH=CF2 4-H 5-S02CH2CH2CH=CF2 4-H 5-SCH2CH2CH=CF2 4-H 5-S0CH2CH2CH=CF2 4-H 5-S02CH2CH2CHOF2 4-SCH2CH2CH=€F2 5-CN 4-SOCH2CH2CH=CF2 5-CN 4-S02CH2CH2C=CF2 5-CN 4-SCH2CH2CH=CF2 5-C00C2H5 4-SOCH2CH2CH=CF2 5-C00C2H5 4-S02CH2CH2C=€F2 5-C00C2H5 4-SCH2CH2CH=CF2 5-CF3 4-SOCH2CH2CH=CF2 5-CF3 4-S02CH2CH2CH=CF2 5-CF3 4-SCH2CH2CH=CF2 5-H 4-SOCH2CH2CH=CF2 5-H 4-S02CH2CH2CH=CF2 5-H 4-SCH2CH2CH=CF2 5-H 4-SOCH2CH2CH=CF2 5-H 4-S02CH2CH2CH=CF2 5-H 1X190 1-CH3 3-CF3 4-SCH2CH2CH=CF2 5-H 1X191 1-CH3 3-CF3 4-S0CH2CH2CH=CF2 5-H 1X192 1-CH3 3-CF3 4-S02CH2CH2CH-CF2 5-H Examples of compounds of Formula (X) according to the invention are set )r N . 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SOCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-S02CH2CH2CH=CF2 5-SCH2CH2CH=€F2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SOCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-S02CH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SOCH2CH2CH=CF2 5-S02CH2CH2CH=€F2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SOCH2CH2CH=CF2 5-S02CH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SOCH2CH2CH=CF2 5-S02CH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SOCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-C6H5 5-C6H5 X160 3-(4-OCH3-C6H4) 5-SCH2CH2CH=CF2 Examples of compounds of Formula (XI) according to the invention are set out in Table XI. ) //r N -SCH2CH2CH=CF2 -SCH2CH2CH=CF2 •SCH2CH2CH=CF2 ■SCH2CH2CH=CF2 ■SCH2CH2CH=CF2 ■SCH2CH2CH=CF2 ■SCH2CH2CH=CF2 ■SOCH2CH2CH=CF2 •SCH2CH2CH=CF2 ■SOCH2CH2CH=CF2 ■S02CH2CH2CH=CF2 ■SCH2CH2CH=CF2 ■SCH2CH2CH=CF2 •SCH2CH2CH=CF2 ■SCH2CH2CH=CF2 ■SOCH2CH2CH=CF2 ■S02CH2CH2CH=CF2 ■ SCH2CH2CH=CF2 •S02CH2CH2CH=CF2 ■SCH2CH2CH=CF2 ■SCH2CH2CΗKT2 ■SCH2CH2CH=CF2 ■SCH2CH2CH=CF2 ■SCH2CH2CH T2 •SCH2CH2CH T2 ■SCH2CH2CH=CF2 ■SCH2CH2CH=CF2 ■SCH2CH2CH=CF2 ■SCH2CH2CH=CF2 ■SOCH2CH2CH=CF2 ■S02CH2CH2CH=CF2 -SCH2CH2CH=CF2 -SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=€F2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=€F2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SOCH2CH2CH=CF2 5-S02CH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH= F2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=€F2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SOCH2CH2CH=CF2 5-S02CH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=€F2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-SCH2CH2CH=CF2 5-S0CH2CH2CH=CF2 5-S02CH2CH2CH=CF2 5-SCH2CH2CH=€F2 5-SOCH2CH2CH=CF2 5-S02CH2CH2CH=CF2 TABLE XD No. R2 R5 Xπ.l 2-SCH2CH2CH=CF2 5-C-C3H5 Xπ.2 2-SCH2CH2CH=CF2 5-C≡CH XH.3 2-SCH2CH2CH=CF2 5-C6H5 XQ.4 2-S0CH2CH2CH=CF2 5-C6H5 Xπ.5 2-S02CH2CH2CH=CF2 5-C6H5 XQ.6 2-SCH2CH2CH=CF2 5-CF2H Xπ.7 2-SCH2CH2CH=CF2 5-CF3 Xπ.8 2-SCH2CH2CH=CF2 5-CH(CH3)2 Xπ.9 2-S02CH2CH2CH=CF2 5-CH(CH3)2 XH.10 2-SCH2CH2CH=€F2 5-CH=CH2 XO.11 2-SCH2CH2CH=CF2 5-CH2(2,6-di F -C6H3) XQ.12 2-SCH2CH2CH=CF2 5-CH2(4-N02-C6H4) Xπ.13 2-S02CH2CH2CH=CF2 5-CH2(4-N02-C6H4) XQ.14 2-SOCH2CH2CH=CF2 5-CH2(4-OCH3-C6H4) XQ.15 2-S02CH2CH2CH=CF2 5-CH2(4-OCH3-C6H4) Xπ.16 2-SCH2CH2CH=CF2 5-CH2Br Xπ.17 2-SCH2CH2CH=CF2 5-CH2C6H5 Xπ.l 8 2-SOCH2CH2CH=CF2 5-CH2C6H5 Examples of compounds of Formula (XEQ) according to the invention are N-N // W set out in Table XH TABLE XIV N No. Rl XIV.1 1-CH3 5-SCH2CH2CH=CF2 Examples of compounds of Formula (XV) according to the invention are set out in Table XV. Examples of compounds of Formula (XVI) according to the invention are set out in Table XVI. XVI.17 2-SCN2CH2CH=CF2 3-H 4-H XVI.18 2-SCH2CH2CH=CF2 3-H 4-H XVI.19 2-SCH2CH2CH F2 3-H 4-H XVI.20 2-S02CH2CH2CH=CF2 3-H 4-H XVI.21 2-SCH2CH2CH=€F2 3-H 4-H XVI.22 2-SCH2CH2CH=CF2 3-H 4-H XVI.23 2-SCH2CH2CH< F2 3-H 4-H XV1.24 2-SCII2CH2CH< F2 3-N02 4-H Ul 00 Exaπφles of coπφounds of Formula (XVII) according to the invention are set out in Table XVΗ. R. Exanφles of coπφounds of Formula (XVm) according to the invention are set out in Table XVm. TABLE XVm No. R2 R3 XVm.l 2-SCH2CH2CH=CF2 3-H XVm.2 2-SOCH2CH2CH=CF2 3-H XVm.3 2-S02CH2CH2CH=CF2 3-H XVm.4 2-SCH2CH2CH=CF2 3-H XVm.6 2-S02CH2CH2CH=CF2 3-H XVm.7 2-SCH2CH2CH=CF2 3-H XVffl.8 2-SOCH2CH2CH=CF2 3-H XVm.9 2-S02CH2CH2CH=CF2 3-H XVm.lO 2-SCH2CH2CH=CF2 3-Cl XVm.12 2-S02CH2CH2CH=CF2 3-Cl XVm.13 2-SCH2CH2CH=CF2 3-SCH2CH2CH=CF2 XVm.14 2-SCH2CH2CH F2 3-H 5-H 6-C1 XVm.15 2-SOCH2CH2CH=CF2 3-H 5-H 6-C1 XVm.16 2-S02CH2CH2CH=CF2 3-H 5-H 6-C1 Exanφles of coπφounds of Formula (XIX) according to the invention are set out in Table XIX TABLE XIX No. R4 R5 R6 XIX 1 4-SCH2CH2CH=CF2 -CH=CH-CH=CH- Exaπφles of coπφounds of Formula (XX) according to the invention are set out in Table XX TABLE XX No. R3 R5 R6 XXI 3-SCH2CH2CH=CF2 5-Br 6-H XX2 3-SCH2CH2CH=CF2 5-C-C3H5 6-H XX3 3-SOCH2CH2CH=CF2 5-C-C3H5 6-H XX4 3-SCH2CH2CH=CF2 5-C6H5 6-CH3 XX5 3-SOCH2CH2CH=CF2 5-C6H5 6-CH3 XX6 3-S02CH2CH2CH=CF2 5-C6H5 6-CH3 XX7 3-SOCH2CH2CH=€F2 5-C6H5 6-CN XX8 3-SCH2CH2CH=CF2 5-C6H5 6-H XX9 3-S02CH2CH2CH=€F2 5-C6H5 6-H XX10 3-SCH2CH2CH=CF2 5-(4-F-C6H4) 6-H XX I I 3-SOCH2CH2CH=CF2 5-(4-F-C6H4) 6-H XX 12 3-SCH2CH2CH=CF2 5-CF2H 6-CH3 XX 13 3-SCH2CH2CH=CF2 5-CF3 6-H XX 14 3-SOCH2CH2CH=€F2 5-CF3 6-OC6H5 XX 15 3-SCH2CH2CH=CF2 5-CH(CH3)2 6-H 6-CH2S02C6H5 6-CH3 6-CH3 6-CH3 6-CHO 6-C1 6-C1 6-CN 6-COCH3 6-CON(CH3)2 6-CON(CH3)C2H5 6-CONHCH2C6H5 6-CONHCH2CH2CH=CF2 6-CONHCH2CH2CH3 6-COOC6H5 6-COOCH2CH2CH=CF2 6-COOCH2CH2F 6-COOCH3 6-COOCH3 6-COOH 6-COOH 6-F 6-H 6-NHCH2CH3 6-NHCH2CH3 6-NHCOC2H5 6-NHCOC6H5 6-NHCOCF3 6-NHCOCH3 6-NHCOOCH3 6-NHCSCH2CH3 6-NHCSNHCH2CH3 6-NHS02CH3 X 148 3-SCH2CH2CH=CF2 5-H 6-N02 XX 149 3-SCH2CH2CH=CF2 5-H 6-OC4H9 X 150 3-SOCH2CH2CH=CF2 5-H 6-OC5H11 XX 151 3-SCH2CH2CPXCF2 5-H 6-OC6H5 XX152 3-SOCH2CH2CH=CF2 5-H 6-OC6H5 XX 153 3-SCH2CH2CH=CF2 5-H 6-OCF2CF2H XX 154 3-SCH2CH2CH=CF2 5-H 6-OCF3 XX 155 3-SOCH2CH2CH=CF2 5-H 6-OCF3 XX 156 3-S02CH2CH2CH=CF2 5-H 6-OCH(CH3)C2H5 XX157 3-SCH2CH2CH=CF2 5-H 6-OCH2(4-Cl-C6H4) X 158 3-S02CH2CH2CH=CF2 5-H 6-OCH2(4-Cl-C6H4) XX 159 3-SCH2CH2CH=CF2 5-H 6-OCH2C6H5 X 160 3-SCH2CH2CH=CF2 5-H 6-OCH2CCl=CH2 XX 161 3-SCH2CH2CH=CF2 5-H 6-OCH2CH=CC12 XX162 3-SCH2CH2CH=CF2 5-H 6-OCH2CH=CH2 XX 163 3-S02CH2CH2CH=CF2 5-H 6-OCH2CH=CH2 XX 164 " 3-SCH2CH2CH=CF2 5-H 6-OCH2CH2CH3 XX 165 3-SCH2CH2CH=CF2 5-H 6-OCH2CH2COOCH3 XX 166 3-SOCH2CH2CH=CF2 5-H 6-OOI2CH2COOCH3 XX 167 3-SCH2CH2CH=CF2 5-H 6-OCH2CH2CH=CF2 XX 168 3-SCH2CH2CH=CF2 5-H 6-OCH2CH3 XX 169 3-SCH2CH2CH=CF2 5-H 6-OCH2COOH XX 170 3-SCH2CH2CH=CF2 5-H 6-OCH3 XX171 3-SOCH2CH2CH=CF2 5-H 6-OCH3 X 172 3-SCH2CH2CH=CF2 5-H 6-OCOC2H5 X 173 3-SCH2CH2CH=CF2 5-H 6-OCOC6H5 XX174 3-SCH2CH2CH=CF2 5-H 6-OH X 175 3-SOCH2CH2CH=CF2 5-H 6-OH XX 176 3-SCH2CH2CH=CF2 5-H 6-SCF3 XX 177 3-SOCH2CH2CH=CF2 5-H 6-SCF3 XX 178 3-SCH2CH2CH=CF2 5-H 6-SCH2CH2CH3 XX179 3-SCH2CH2CH=CF2 5-H 6-SCH2CH2CH=CF2 X 180 3-SCH2CH2CH=CF2 5-H 6-SCH3 5-SCH2CH2CH=CF2 6-CH3 5-SCH2CH2CH=CF2 6-H 5-S0CH2CH2CH=CF2 6-CH3 5-S02CH2CH2CH=CF2 6-CH3 -(CH2CH2CH2CH2)- -(CH2CH2CH2CH2> -(CH2CH2CH2CH2> Exanφles of coπφounds of Formula (XXI) according to the invention are set out in Table XXI. TABLE XXI No. R2 R4 R6 XXI.1 2-SCH2CH2CH=CF2 4-H 6-H The compounds of formula (I) wherein n is 0 may be prepared by a variety of methods. They may be prepared, for example, by the reaction of a corresponding thiol compound of formula (XXHI) and an appropriate difluorobut-1-ene alkylating agent of formula (XXTV), where L is a good leaving group. This reaction is preferably conducted in the presence of a mild base such as an alkali metal carbonate, for example sodium or potassium carbonate, in an inert solvent, at a temperature of from 0°C to 200°C. Conveniently the reaction may be conducted at the reflux temperature of a suitable inert solvent, for exanφle acetone, which has a boiling point within this range. In formula (XXTV) the leaving group L is preferably a halogen or an ester of sulfonic acid having the formula OS02Rb, as illustrated by formula (XXV), where Rb is a Cl-4 alkyl group or a phenyl group optionally substituted with a Cl-4 alkyl group. More preferably, L is bromine as shown in formula (XXVI). The sulfonic ester of formula (XXV) may be prepared by reaction of 1,4-dibromo- 1,1,2-trifluorobutane with the silver salt of the chosen sulfonic acid and debromofluorination of the resulting intermediate, 4-toluenesulfonate ester. In copending International Patent Application No. PCT/GB94/01570, we disclose a method for preparing the compound of formula (XXVI), namely 4-bromo-l,l-difluorobut-l- ene. in which hydrogen bromide is reacted with commercially available 4-bromo-l,l,2- trifluorobut-1-ene in an inert solvent to give l,4-dibromo-l,1.2-trifluorobutane. This intermediate can then be treated with a debromofluorinating agent in a suitable solvent, for example acetone or water, to give the compound of formula (XXVI). It will be appreciated by those skilled in the art that coπφounds of Formula (XXm) may exist in tautomeric equilibrium between the equivalent mercapto and thione forms. For the sake of convenience, these compounds are referred to herein in their mercapto form unless otherwise stated. Compounds of Formula (XXIII) are commercially available or may be prepared from commercially available precursors by standard procedures well known in the art. Alternatively, the compounds of formula (I) may be prepared by reacting a corresponding compound of formula (XXVII), where L is again a good leaving group, with a mercapto compound of formula (XXVIII), under conditions well known in the art for such displacement reactions. Preferably, L is halogen or a nitro group. Conveniently the reaction may be carried out using a two phase solvent system, such as water/dichloromethane, in the presence of a phase transfer catalyst, for example tetra-n-butyl ammonium bromide, at ambient-temperature under a nitrogen atmosphere. The mercapto compound of formula (XXVEI) is conveniently reacted in the form of its S-acetyl or its isothiouronium hydrogen bromide salt, which compounds are readily hydrolysed to the mercapto compound of formula (XXVIII). The compounds of formula (ϊ) may also be prepared from the corresponding amino compound of formula (XXIX), -which can be diazotised, for example with an alkylnitrite, such as tert. butyl nitrite, in the presence of the disulfide of formula (XXX), in a- suitable solvent, such as dichloromethane or acetonitrile. The compounds of formula (I) where n is 1 or 2, may be prepared by oxidising the correspondingly substituted compound of formula (I) when n is 0, using conventional methods, for example by treatment with a suitable oxidising agent in an inert organic solvent. In general, oxidation of a compound of Formula (I) with one equivalent of a suitable oxidising agent provides the corresponding compound wherein n is 1, and oxidation using two equivalents of the oxidising agent provides the corresponding compound wherein n is 2. Suitable oxididising agents include organic and inorganic peroxides such as peroxy carboxylic acids, or their salts, for example, meta-chloroperbenzoic acid, perbenzoic acid, magnesium monoperoxy-phthalic acid or potassium peroxymono-sulfate. Thus. according to a further aspect of the present invention there is provided a process for the preparation of coπφounds of formula (I) where n is 1 or 2. which comprises oxidation of the correspondingly substituted compound of formula (I) when n is 0. As well as the coπφounds of formula (I) being prepared from the corresponding substituted compounds of formula (XXffl), (XXW) or (XXIX), it will be appreciated that subsequent functional group transformations may be carried out using known chemistry to obtain the required ring substitution. Exaπφles of such functional group transformations include the reduction of nitro groups to amine groups, halogenation, e.g. chlorination, hydrolysis of an ester to the acid, oxidation of an alcohol to the acid, salt formation. Various further preferred features and embodiments of the present invention will now be described in futher detail with reference to the following illustrative exaπφles in which percentages are by weight and the following abbreviations are used: πφ = melting point; bp = boiling point; g = grammes; gc = gas chromatography; NMR = nuclear magnetic resonance; s = singlet; d = doublet; dd = double doublet; t = triplet; q = quartet; m = multiplet; br = broad; M=mole; mM=millimoles; CDC1 3 = deuteriochloroform. Chemical shifts (δ) are measured in parts per million from tetramethylsilane. CDC1 3 was used as solvent for NMR spectra unless otherwise stated. M* " = molecular ion as determined by mass spectrometry; FAB = fast atom bombardment; tic = thin layer chromatography. The synthesis of a number of intermediate compounds of use in the preparation of compounds according to the invention is given below. Some of these compounds are known in the art. PREPARATION 1 This illustrates a 3-step preparation of 4-bromo-4,4-difluorobutyl methanesulfonate. Stgp 1; 4-bromo-4.4-difluorobutanoic acid. To a stirred solution of acrylic acid (1.44g) and acetonitrile (80cm 3 ) was added sodium dithionite (4.18g), sodium bicarbonate (2.0 lg), water (20cm 3 ) and finally dibromodifluoromethane (5cm 3 ). The biphasic mixture was stirred at the ambient temperature with the inorganic salts gradually dissolving. GC analysis after 4 hours indicated complete consumption of acrylic acid. The aqueous phase was saturated with solid sodium chloride. The organic phase was separated, dried over magnesium sulfate, filtered and evaporated under reduced pressure to give a pale yellow oil with a small amount of a white solid. This mixture was taken up in ethyl acetate, filtered and solvent evaporated under reduced pressure to give a pale yellow oil (2.54g). Η NMR (DMSO-d^): δ 2.45(2H,t); 2.65(2H,m). Step 2: 4-bromo-4.4-difluorobutanol . Under an atmosphere of nitrogen, a solution of lithium aluminium hydride in diethylether (5cm 3 , 5mM) was cooled to 0°C. Maintaining this temperature, 4-bromo-4,4-difluorobutanoic acid (lg) dissolved in dry diethylether (5cm 3 ) was added dropwise with stirring. After an hour at 0°C the reaction mixture was cautiously quenched by the addition of 2M hydrochloric acid The organic phase was separated, washed with saturated sodium bicarbonate solution, dried over magnesium sulfate. filtered and evaporated under reduced pressure to give a colourless oil (0.57g). 'H NMR δ 1.82-1.96(2H,m); 2.40-2.60 (2H,m); 3.74(2H,t). Step 3: 4-bromo-4.4-difluorobutvl methanesulfonate. A stirred solution of 4-bromo-4,4-difluorobutanol (0.57g) in dry diethylether (5cm 3 ) was cooled to 0°C. Maintaining this temperature, triethylamine (1.7cm 3 ) was added. After ten minutes methanesulfonyl chloride (0.3cm 3 ) was added and the mixture stirred for a further hour at 0°C. The reaction mixture was poured into 2M hydrochloric acid (2cm 3 ) and diethylether (20cm 3 ). The organic phase was separated, washed with saturated brine, then passed through a plug of silica gel eluting with further diethylether. The diethylether fractions- were evaporated under reduced pressure to give a light yellow oil (0.705g). Η NMR: δ 2.04-2.18(2H,m); 2.46-2.64(2H,m); 3.04(3H,s); 4.32(2H,t). PREPARATION 2 This illustrates a 3-step preparation of the 4,4-difluorobut-3-enyl ester of 4-methyl- benzenesulfonic acid from commercially available 4-bromo-l,l,2-trifluorobut-l-ene. Step 1 ; Preparation of 1.4-dibromo-l.L2-trifluorobutane. 4-Bromo-l,l,2-trifluorobut-l-ene (Fluorochem Ltd) (240g) was washed with water (300cm 3 ) and then with brine (300cm 3 ) and dried (MgS0 4 ) before use. Benzoyl peroxide (ca. 0.7g) was added in one portion and hydrogen bromide gas was bubbled through the mixture at such a rate that the reaction temperature was maintained at 30 to 40°C. After 2 hours, gc of a sample of the reaction mixture showed that little starting material remained. The reaction mixture was washed with water (300cm 3 ), then with saturated sodium bicarbonate solution and then again with water (300cm 3 ), dried (MgS0 4 ), and filtered to give a pale yellow oil (296.7g) identified as l,4-dibromo-l,l,2-trifluorobutane. The material was shown by gc analysis to be greater than 98% pure. 'H NMR: δ 2.38(2Em); 3.57(2H,m); 4.90(lH,m). Step 2: Preparation of 4-bromo-3.4.4-trifluorobutvl 4-methyl-ben7enesulfonate The product from Step 1 (lg) was added dropwise to a stirred suspension of silver tosylate (1.03g) in acetonitrile (10cm 3 ) at ambient temperature, protected from the light. The reaction was then heated under reflux for 24 hours after which gc analysis indicated conφlete consumption of starting material. The reaction mixture was cooled to the ambient temperature and the precipitate was filtered off and washed with ethyl acetate. The filtrate and ethyl acetate washings were combined and washed with water and the aqueous layer extracted with ethyl acetate. The combined ethyl acetate layers were washed with water and brine, dried over magnesium sulfate and evaporated under reduced pressure to give a brown oil (1.21g). GC analysis showed this material to be > 99% pure. 'H NMR: δ 2.20(2H,m); 2.46(3H,s); 4.19(2H,m); 4.74(lH,m); 7.38(2H,d); 7.80(2H,d). Step 3; Preparation of 4.4-difluorobut-3-enyl 4-methyl-benzenesulfonate To a stirred suspension of powdered zinc (1.41g) and iodine (one grain, catalytic) in methanol (3cm 3 ) was added a solution of 4-bromo-3,4,4-difluorobutyl p-tolylsulfonate (0.71 g) in methanol (2cm 3 ). The reaction mixture was heated under reflux for 214 hours after which gc analysis indicated complete consumption of starting material. The organic phase was pipetted from the zinc suspension and the zinc was washed with 3 portions of ethyl acetate. The combined ethyl acetate portions were washed with 2M hydrochloric acid, dried over magnesium sulfate and evaporated under reduced pressure to give a brown liquid (0.47g). GC analysis showed this material to be > 99% pure. 'H NMR: δ 2.35(2H,m); 2.46(3H,s); 4.01(2H,m); 4.15(lH,m); 7.38(2H,d); 7.79(2H,d). PREPARATION This illustrates a preparation of 4-bromo-l,l-difluorobut-l-ene from 1,4-dibromo- 1 , 1 ,2-trifluorobutane. Zinc powder (0.88g) was added to a stirred solution of l,4-dibromo-l,l,2- trifluorobutane (1.38g) in acetone (6cm 3 ) containing water (1 drop), under an atmosphere of nitrogen. After 45 minutes, gc analysis showed that a large proportion of the starting material had been consumed. The mixture was then added to more zinc powder (3g) in acetone containing a trace of water, which had been preheated to 55°C. After a further 20 minutes at this temperature, gc analysis indicated that all of the starting material had been consumed, showing that the de-bromofluorination reaction had initiated. More starting material (12.34g) was then added to the reaction over a period of 75 minutes while the reaction mixture was kept at 55°C. Heating was then continued for a further 95 minutes. GC analysis of a sample indicated that about 3% of the starting dibromo compound remained unchanged. Further zinc powder (0.16g) was added and heating continued until gc analysis showed all the starting material had been consumed. The acetone solution was decanted from the zinc residues to give a solution of 4-bromo-l,l-difluorobut-l-ene suitable for use in further chemical reactions. PREPARATION 4 This illustrates a preparation of 4,4-difluorobut-3-enyl thioacetate. Potassium thioacetate (1.98g), 4-bromo-l,l-difluorobut-l-ene (3.0g) and tetra-n- butylammonium bromide (0.3g, catalyst) were stirred at the ambient temperature under nitrogen for 5 hours and stored for 18 hours. The mixture was distilled using a Kugelrohr apparatus to give 4,4-difluorobut-3-enyl thioacetate as a colourless liquid (1.12g); *H NMR: δ 2.25(2H,m); 2.30(3H,s); 2.90(2H,t); 4.20(lH,m); (bp 115°C at 120mmHg). PREPARATION 5 This illustrates a preparation of 4,4-difluorobut-3-enylisothiouronium 4-methyl- benzenesulfonate salt. Thiourea (0.29g) and 4,4-difluorobut-3-enyl 4-methyl-benzenesulfonate (lg) were heated together under reflux in ethanol (20cm 3 ) for 24 hours. The reaction mixture was cooled and the solvent evaporated under reduced pressure to give an oil which slowly crystallised. Trituration with hexane gave (4,4-difluorobut-3-enyl)-thiourea as its 4-methyl- benzenesulfonate salt (1.14g). δ 2.48(3H,s); 2.46- 2.58(2H,m); 3.42(2H,t); 4.66-4.84(lH,m); 7.32(2H,d); 7.68(2H,d); 9.10-9.40(3H,br) PREPARATION 6 This illustrates a preparation of 4,4-difluorobut-3-enylisothiouronium hydrobromide. Thiourea (18.5g) was added to a solution of 4-bromo-l,l-difluorobut-l-ene (41.5g) in ethanol (150cm 3 ) and heated to reflux with stirring for 18h. The reaction mixture was cooled to ambient temperature and evaporated under reduced pressure. The waxy solid obtained was washed with diethyl ether, filtered, washed with further diethyl ether and sucked to dryness to give the required product as a colourless solid, (57g). MH + =167; 'H NMRφMSO-cy: δ 2.20(2H,m); 3.20(2H,t); 4.50(lH,m); 8.95(4H,broad signal). • The N-methyl derivative of the foregoing intermediate was prepared by the above procedure but using N-methyl thiourea in place of thiourea. It had MH + =181; 'H NMRODMSO-d ): δ 2.45-2.55(2H,m); 3.0-3.05(3H,d); 3.4-3.5(2H,t); 4.30-4.45(lH,m); (m.p. 74-77.2°C). PRF.PARATION 7 This illustrates a preparation of bis-(4,4-difluorobut-3-enyl)disulfide. A solution of sodium disulfide (previously prepared from sodium sulfide nonahydrate (53 g) and sulfur (7.0g) in ethanol (250cm 3 )) was added to l-bromo-4,4-difluorobut-3-ene (50g) in ethanol (100cm 3 ). The mixture was gradually heated and stirred under reflux for 2 hours, then cooled and evaporated under reduced pressure. The residue was extracted with diethyl ether, the organic phase filtered to remove sodium bromide and the ether evaporated under reduced pressure to give a liquid which was distilled at 16mm Hg, bp 120°C to give the bis-(4,4-difluorobut-3-enyl)disulfide (24g) as a colourless liquid EXAMPLE π.l This Example illustrates a preparation of 2-(4,4-difluorobut-3-enylthio)furan (Compound π.l). Butyllithium (6.5cm 3 , 2.5M in ether) was added dropwise with stirring to a solution of furan (lg) in diethyl ether (40cm 3 ). After 90 minutes, the reaction mixture was heated to reflux for 30 minutes and then cooled to the ambient temperature. Powdered sulfur (0.48g) was added portionwise with stirring. After 2 hours, 4-bromo-l,l-difluorobut-l-ene (3.0g) was added and stirring continued at the ambient temperature for 18 hours. The reaction was quenched with water and the product extracted into diethyl ether. The combined organic extracts were dried, filtered and evaporated to give a dark brown liquid Chromatography on silica (eluant hexane-diethyl ether mixtures) afforded Compound π.l (0.965g). ! H NMR: δ 2.2-2.3(2H,m); 2.7-2.8(2H,t); 4.15-4.35(lH,m); 6.4(lH,dd); 6.53(lH,d); 7.5(lH,d); (oil). EXAMPLE π,2 This Example illustrates a preparation of 2-(4,4-difluorobut-3-enyltlιio)-5-methylfuran (Compound H.4). Butyllithium (5.4cm 3 , 2.5M in ether) was added dropwise with stirring to a solution of fiiran (lg) in diethyl ether (40cm 3 ). After 90 minutes, the reaction mixture was heated under reflux for 30 minutes and then cooled to the ambient temperature. Powdered sulfur (0.38g) was added portionwise with stirring. After 2 hours, 4-bromo-l,l-difluoiObut-l-ene (2.05g) was added and stirring continued for 18 hours. The reaction was quenched with water and the product extracted into diethyl ether. The combined organic extracts were dried, filtered and evaporated. Chromatography on silica (eluant hexane-ether mixtures) afforded Compound II.4 (1.25g). Η NMR: δ 2.2-2.3(2H,m); 2.3(3H,s); 2.7-2.77(2H,t); 4.16- 4.34(lH,m); 5.97(lH,m); 6.43(lH,d); (oil). EXAMPLE π.3 This Example illustrates a preparation of 3-(4,4-difluorobut-3-enyll-hio)-2-memylfuran (Compound H.7). A solution containing 2-methyl-3-furanthiol (2.0g), 4-bromo-l,l-difluorobut-l-ene (3.24g) and potassium carbonate (2.48g) in acetone (50cm 3 ) was heated under reflux for 2 hours and then left to stand for 18 hours. The reaction was quenched with water and the product extracted into diethyl ether. The combined organic extracts were dried, filtered and evaporated. Chromatography on silica (eluant 10% ether in hexane) afforded Compound H.7 (2.338g); ^=204; 'H NMR: δ 2.1-2.25(2H,m); 2.35(3FLs); 2.65(2H,t); 4.1-4.3(lH,m); 6.3 (Hid); 7.3(1H, d); (oil). EXAMPLE TT.4 This Example illustrates a preparation of 2-(4,4-difiuorobιιt-3-enylsulf yl)furan (Compound H.2). 3-Chloroperbenzoic acid (0.54g of a 50% by weight solid, 1.58mM) was added portionwise to a solution of Coπφound H.l (0.30g) in dichloromethane (5cm 3 ) with ice-bath cooling. After stirring for 4 hours, the reaction was partitioned between ethyl acetate and 2M NaOH solution. The organic layer was separated, washed with more 2M NaOH solution, dried over magnesium sulfate, filtered and evaporated to give Coπφound H.2 (0.2 lOg). Η NMR: δ 2.3-2.5(2H,m); 3.1-3.4(2H,m); 4.15-4.35(lH,m); 6.5(lH,dd); 7.0(lH,d); 7.7(lH,d); (oil). The following compounds according to the invention were prepared by the above procedure: (i) 2-(4,4-difluorobut-3-enylsulfonyl)furan (Coπφound U.3); »H NMR: δ 2.4-2.55(2H,m)r 3.25-3.3(2H,t); 4.1-4.3 (lH,m); 6.6(lH,dd); 7.23(lH,d); 7.67(lH,d) (oil) from Coπφound H.l using 2.1 equivalents of oxidant. (ii) 2-(4,4- uorobut-3-enylsulfmyl 5-memylfuran (Compound π.5); Η NMR: δ 2.3- 2.45(5H,m); 3.0-3.15 and 3.3-3.4(total 2H,m); 4.2-4.3(lH,m); 6.1(lH,d); 6.85(lH,d); (oil) from Compound π.4 using 1 equivalent of oxidant. (iii) 2-(4,4-difluorobut-3-enylsulfonyl 5-methylfuran (Compound H.6); 'H NMR: δ 2.4- 2.55(5H,m); 3.2-3.28 (2H,t); 4.15-4.3(lH,m); 6.2(lH,d); 7.1(lH,d); (oil) from . Coπφound H.4 using 2.1 equivalents of oxidant. (iv) 3-(4,4-difluorobut-3-enylsulfinyl 2-methylfuran (Compound π.8); 'H NMR: δ 2.3- 2.45(5H,m); 2.8-2.9 and 3.1-3.2(total 2H, m); 4.2-4.35(lH,m); 6.66(lH,d); 7.4(lH,d) from Compound H.4 using 1 equivalent of oxidant. (v) 3-(4,4-difluorobut-3-enylsulfonyl>2-methylfuran (Compound π.9); 'H NMR: δ 2.42- 2.52(2H,m); 2.6(3Rs); 3.2-3.28(2Ht); 4.1-4.23(lH.m); 6.6(lRd); 7.36(lH.d) mom Coπφound π.4 using 2.1 equivalents of oxidant. EXAMPLE m.l This Example illustrates a preparation of 2-(4,4-difluorobut-3-enylthio)thiophene (Compound in.1). A solution containing 2-mercaptothiophene (lOg), 4-bromo-l,l-difluorobut-l-ene (15.47g) and potassium carbonate (11.87g) in acetone (250cm 3 ) was heated under reflux for 2 hours and then left to stand for 18 hours. The reaction was quenched with water and extracted several times with diethyl ether. The combined organic extracts were dried over magnesium sulfate, filtered and evaporated to give an amber oil. Chromatography on silica (eluant 5% ether in hexane) afforded Compound m.l (9.5g); M + ^206; H NMR: δ 2.2- 2.4(2H,m); 2.8(2H,t); 4.1-4.3(lH,m); 6.95-7.0(1 H,dd); 7.15(lH,d); 7.35(lH.d); (oil). The following compound according to the invention was prepared by the above procedure, (i) 2-(4,4-difluorobut-3-enylthio)benzo[b]thiophene (Coπφound m.10); 'H NMR δ 2.2- 2.3(2H,m); 2.7-2.8(2H,t); 4.15-4.35(lH,m); 6.4(lH,dd); 6.53(lH,d); 7.5(lH,d). from benzthiophene. EXAMPLE TTT.2 This Exanφle illustrates a preparation of 2-(4,4-difluorobut-3-enylthio)-5- formylthiophene (Coπφound ffi.4). Coπφound m.l (l.Og) was added slowly to a solution containing dimethyl formamide (0.48cm 3 ) and phosphoryl chloride (0.56cm 3 ). The reaction mixture was heated at 100°C for 2 hours, cooled in an ice-bath and then neutralised with 2M NaOH solution. The aqueous solution was extracted twice with diethyl ether and the combined organic layers were washed with water and NaHC0 3 solution. The organic extracts were dried over magnesium sulfate, filtered and evaporated to give a dark liquid. Filtration through silica (eluant 20% diethyl ether in hexane) afforded Compound ffl.4 (0.91g). M + =234; Η NMR: δ 2.4(2H,m); 3.0(2H,t); 4.2-4.4(lH,m); 7.1(lH,d); 7.7(lH,d); 9.8(lH,s); (oil). EXAMPLE TTT.3 This Example illustrates a preparation of 2-(4,4-difluorobut-3-enylthio)-5- hydroxymethylthiophene (Compound HT.5). Sodium borohydride (0.065g) was added to a solution of Compound IH.4 (0.75g) in ethanol (21cm 3 ) and water (9cm 3 ). The reaction mixture was stirred at the ambient temperature for 2 hours, quenched with 2M hydrochloric acid and then partitioned between water and diethyl ether. The organic phase was dried over magnesium sulfate, filtered and evaporated to give a greenish liquid. Chromatography on silica (eluant 20% ethyl acetate in hexane) afforded Coπφound m.5 (0.44g). M + =236; Η NMR: δ 1.8-2.0(lH,br s); 2.3(2Rm); 2.8(2H,t); 4.1-4.3(lH,m); 4.8(2H,s); 6.8(lH,d); 7.0(lH,d); (oil). EXAMPLE m,4 This Example illustrates a preparation of (£)- and (Z)-2-(4,4-difluorobut-3-enylthio)-5- hydroximinothiophene (Coπφounds m.6 and UL.T). Hydroxylamine hydrochloride (0.9g) and sodium hydrogen carbonate (1.09g) were stirred together in ethanol (15cm 3 ) and water (15cm 3 ) for 5 minutes. Compound m.4 (3g) was added and the reaction mixture was stirred at the ambient temperature for 2 hours and then left to stand for 18 hours. The reaction mixture was partitioned between water and diethyl ether. The organic phase was dried over magnesium sulfate, filtered and evaporated to give an amber liquid (3.4g). Chromatography on silica (eluant 20% ethyl acetate in hexane)-afforded Compounds ffl.6 (1.5g) and m.7 (1.3g). lvf=249; 'H NMR: δ 2.25- 2.35(2H,m); 2.85(2H,t); 4.14-4.35(lH,m); 7.05(2H,m); 7.52(lH,br s); 8.18(lH,s); (oil) and T =249; δ 2.25-2.38(2H,m); 2.85-2.95(2H,t); 4.18-4.35(lH,m); 7.08(lH,d); 7.25(lH,d); 7.64(lH,s); (oil). EXAMPLE m.5 This Example illustrates a preparation of 5-cyano-2-(4,4-difluorobut-3-enylthio)- thiophene (Coπφound m.8). l, -ωrbonyl-diimidazole (0.326g) was added to a solution of Coπφound m.6 (0.5g) and the reaction mixture was stirred at the ambient temperature for 10 minutes, then heated under reflux for 2 hours and left to stand for 18 hours. A further equivalent of l,r-carbonyl- diimidazole was added and the reaction mixture heated under reflux for 1 hour. The reaction mixture was filtered through celite and then evaporated to give Coπφound m.8 (0.28g). 'H NMR δ 2.27-2.38(2H,m); 2.94(2H,t); 4.15-4.33(lH,m); 7.05(lH,d); 7.5(lH,d); (oil). EXAMPLE m.6 This Example illustrates a preparation of 5-acetyl-2-(4,4-difluorobut-3-enylthio)- thiophene (Compound ffl.9). A solution of methylmagnesium bromide (1.3cm 3 , 3M solution in diethyl ether, 3 equiv.) was added slowly to a solution of Compound ffl.8 (0.3g) in tetrahydrofuran (10cm 3 ). The reaction mixture was stirred at the ambient temperature for 3 hours and then the solvent was evaporated. The residue was partitioned between ammonium hydroxide solution and chloroform. The organic layer was washed with water, dried over Na 2 S0 4 and evaporated. The residue was chromatographed on silica (eluant 10% ethyl acetate in hexane) to give Compound m.9 (0.16g). l H NMR δ 2.30-2.40(2H,m); 2.50(3H,s); 2.97(2H,t); 4.15- 4.33(lH,m); 7.04(lH,d); 7.55(lH,d); (oil). EXAMPLE m.7 This Example illustrates a preparation of 2-(4,4-difluorobut-3-enylsulfinyl)thiophene (Coπφound m.2). Coπφound m.l (0.50g) was stirred at ambient temperature in dichloromethane (5cm 3 ) and 3-chloro perbenzoic acid (0.834g of a 50% by weight solid, 1 equiv.) was added. After tic indicated consumption of starting material the reaction was quenched by the addition of a saturated aqueous solution of sodium bicarbonate and the product was extracted into dichloromethane. The organic phase was separated, washed with saturated brine and dried over magnesium sulfate. After filtration and concentration by evaporation under reduced pressure, there was obtained a liquid (0.584g) which was purified by chromatography on silica gel using 20% ethyl acetate in hexane as eluant, and then diethyl ether to elute Coπφound m.2 (0.29g). Η NMR: δ 2.3-2.55 (2H, m); 2.9-3.2 (2H, m); 4.2-4.5 (1H, m); 7.15 (1H, m); 7.5 (1H, m); 7.7 (1H, m); (oil). The following compounds according to the invention were prepared by the above procedure: (i) 2-(4,4-difluorobut-3-enylsulfonyl)thiophene (Coπφound m.3). 'H NMR: δ 2.4- 2.6(2H,m); 3.2-3.4(2H,t); 4.1-4.3 (1H, m); 7.15(lH,dd); 7.7-7.8(lH,m); (oil) from Coπφound m.l using two equivalents of oxidant. (ii) 2-(4,4-difluorobut-3-enylsulfinyl)benzo[b]thiophene (Coπφound m.11). 'H NMRi δ 2.3-2.4(2H,m); 3.0-3.2(2H,m); 4.2-4.4(lH,m); 7.45(2H,m); 7.9(2H,m); 7.75(lH,s) from Coπφound m.10 using one equivalent of oxidant. (iii) 2-(4,4-difluorobut-3-enylsulfonyl)benzo[b]thiophene (Compound m.12). 'H NMR: δ 2.5(2H,m); 3.3(2H,t); 4.2-4.35(1 H,m); 7.5(2H,m); 7.9(3H,m) from Coπφound m.10 using two equivalents of oxidant. EXAMPLE TV.l This Exanφle illustrates a preparation of ethyl 5-(4,4-difluorobut-3-enylthio)-3- methylisoxazole-4-carboxylate (Compound IV.8). A solution of 4.4-difiuorobut-3-enyl thioacetate (2g) in 50% sodium hydroxide solution (6.7cm 3 ) was stirred vigorously for 30 minutes. A solution of ethyl 5-chloro-4- methylisoxazole (2.2g) in dichloromethane (12cm 3 ) was added followed by tetra-n- butylammonium bromide (catalyst) and the reaction stirred at the ambient temperature under nitrogen. After 3 hours the layers were separated and the organic phase was washed with brine, dried (MgS0 4 ), filtered and evaporated under reduced pressure. The residue was stirred with 880 ammonia resulting in crystallisation. The crystals were isolated by filtration to give Compound IV.8 (2.87g). Η NMR δ 1.35(3H,t); 2.45(3H,s); 2.50(2H,m); 3.20(2H,t); 4.25(lH,m); 4.30(2H,q); (nφ 41-42°C). EXAMPLE IV,2 This Exanφle illustrates a preparation of 5-(4,4-difluorobut-3-enylthio)-3- methylisoxazole-4-carboxylic acid (Compound IV.9). A solution of Coπφound IV.8 (0.5g) in isopropanol (5cm 3 ) and 2M NaOH (1cm 3 ) was stirred for 3 hours. The mixture was then poured into water and washed with ethyl acetate. The aqueous layer was then acidified with 2M HC1 and the product extracted into ethyl acetate.- This extract was dried (MgS0 4 ), filtered and evaporated under reduced pressure to give Compound IV.9 (0.16g). M + =249; Η NMR δ 2.45(3H,s); 2.50(2H,m); 3.20(2H,t); 4.20- 4.40(lH,m); (πφ 132-133°C). EXAMPLE TV.3 This Exanφle illustrates a preparation of 5-(4,4-difluorobut-3-enylthio)-3- methylisoxazole-4-carboxamide (Compound IV.7). Triethylamine (0.33cm 3 ) and ethyl chloroformate (0.24cm 3 ) were added to Compound- rv.9 (0.56g) in dichloromethane (15cm 3 ) at 0°C. The reaction was allowed to warm to the ambient temperature and stirred for 2 hours. Ammonia was bubbled through the solution until it was saturated and the reaction was then stirred for a further 1 hour. Aqueous ammonia was added and the product extracted into dichloromethane. The organic phase was washed with water, dried (MgS0 4 ), filtered and evaporated under reduced pressure. Purification by distillation in a kugelrohr apparatus gave Coπφound IV.7 (0.069g). H NMR δ 2.45(2H,m); 2.50(3Rs); 3.25(2H,t); 4.25(lH,m); (mp 87°C). EXAMPLE TV.4 This Example illustrates a preparation of 3-(5-chlorofur-2-yl)-5-(4,4-difluorobut-3- enylthio)isoxazole (Compound IV.23). Hydrogen sulfide was bubbled through a stirred solution of potassium methoxide (1.9g) in ethanol (10cm 3 ) cooled in an acetone/ice bath. 5-Chloro-3-(5-chlorofur-2- yl)isoxazole (2.2g) was added and the reaction was then heated under reflux for 1 hour during which time the solvent evaporated. Acetone (10cm 3 ) and 4-bromo-l,l-difluorobut-l- ene (2g) were added and the mixture heated under reflux for a further 2 hours. The resulting solution was cooled, poured into diethyl ether and brine and the layers separated The aqueous layer was extracted with ether. The combined organic phases were washed with brine, dried (MgS0 4 ), filtered and evaporated under reduced pressure to give a black solid. Purification by column chromatography on silica gel using 10% ether in hexane as eluant gave Coπφound IV.23 (2g). M + =291; Η NMR δ 2.35-2.50(2Rm); 3.10(2Rt); 4.30(lH,m); 6.30(lH,d); 6.43(lH,s); 6.90(lRd); (mp 80-82°C). The following coπφound according to the invention was prepared by the above procedure: (i) 5-(4,4-difluorobut-3-enylthio 3-phenylisoxazole (Coπφound rV.l). M + =267; 'H NMR: δ 2.43(2H,m); 3.10(2H,t); 4.28(lH,m); 6.50(lH,s); 7.45(3Rm); 7.78(2Rm); (oil) from 5-chloro-3-phenylisoxazole. EXAMPLE TV.5 This Example illustrates a preparation of 2-(4,4-difluorobut-3-enylthio)-3- methylisoxazole (Coπφound IV.10). To a stirred solution of acetone oxime (0.365g) in dry tetrahydrofuran (20cm 3 ) at 0°C under nitrogen was added n-butyl lithium (4.6cm 3 of a 2.5M solution in hexanes) resulting in formation of a pale yellow precipitate. After stirring at 0°C for 30 minutes, carbon disulfide (0.3cm 3 ) was added producing a bright orange solution. After a further 10 minutes, 3M HC1 (20cm 3 ) was added and the reaction was heated under reflux for 3 hours and then cooled. The layers were separated and the aqueous layer was extracted with chloroform. The combined organic layers were dried (MgS0 4 ), filtered and evaporated under reduced pressure to give a brown oil. The oil was then taken up in acetone (11cm 3 ) and l-bromcv4,4- difluorobut-3-ene (0.77g) and potassium carbonate (0.87g) were added and the reaction heated under reflux for 3.5 hours and then cooled. The mixture was then poured into ethyl acetate and 2M HC1 and the layers separated. The aqueous layer was extracted with ethyl acetate and the combined organic phases were dried (MgS0 4 ), filtered and evaporated under reduced pressure to give a brown oil. Purification by column chromatography on silica gel using 1 :9 ethyl acetate : hexane as eluant gave 2-(4,4-difluorobut-3-enylthio)-3- methylisoxazole (0.105g). M =205; 'H NMR δ 2.30(3Rs); 2.40(2Rm); 3.05(2Rt); 4.25(lRm); 6.00(lH,s); (oil). EXAMPTE TV.6 This Example illustrates a preparation of 3-(5-cWorofur-2-yl)-5-(4,4-difluorobut-3- enylsulfonyl)isoxazole (Compound IV.24). To a stirred solution of Coπφound TV.23 (2g) in methanol (40cm 3 ), cooled in an ice/acetone bath was added magnesium monoperoxyphthalate (9.4g). After stirring for 30 minutes the cooling bath was removed and the reaction allowed to warm to the ambient temperature and stirred for 1 hour. The mixture was poured into diethyl ether and brine and the layers separated. The combined organic phases were washed with 2M NaOH, water and brine, dried (MgS04), filtered and evaporated under reduced pressure to give Compound rV.24 (1.9g). M + =323; 'H NMR: δ 2.50-2.60(2H,m); 3.40(2Rt); 4.25(lRm); 6.38(lRd); 7.05(lRd); 7.20(lH,s); (mp 86.5-88.5°C). The following compounds according to the invention were prepared by the above oxidation procedure: (i) 5-(4,4-difluorobut-3-enylsulfinyl 3-ρhenylisoxazole (Compound IV.2). M"=283; 'H NMR: δ 2.53(2H,m); 3.25(2Rt); 4.29(lRm); 7.18(lRs); 7.50(3Rm); 7.80(2H,m); (oil) from Coπφound IV.1 and one equivalent of oxidant. (ii) 5-(4,4-difluorobut-3-enylsulfonyl)-3-phenylisoxazole (Coπφound TV.3). M*=299; Η NMR: δ 2.57(2Rm); 3.43(2Rt); 4.27(lRm); 7.2(lH,s); 7.51(3Rm); 7.80(2Rm); (mp 57-58.5°C) from Coπφound TV.l and two equivalents of oxidant. (iii) 3-(thien-2-yl)-5-(4,4-difluorobut-3-enylsulfonyl)isoxazole (Coπφound TV.26). M =305; 'H NMR: δ 2.50-2.63(2H,m); 3.41(2H,t); 4.27(lH,m); 7.20(lRs); 7.14- 7.23(lH,m); 7.52(2H,m); (mp 55-57°C) from 3-(thien-2-yl>5-(4,4-difluorobut-3- enylthio)isoxazole, Compound IV.25, itself prepared from 5-chloro-3-(thien-2- yl)isoxazole by the procedue of Example IV.4. EXAMPLE V.l The Example illustrates a preparation of 3-chloro-4-cyano-5-(4,4-difluorobut-3- enylthio)isothiazole (Compound V.2). A solution of 4-cyano-3,5-dichloroisothiazole (lg) in methanol (10cm 3 ) was added over 15 min to a solution of sodium sulfide nonahydrate (1.3g) in water (2.6cm 3 ) and methanol (25cm 3 ) heated at 50°C. The reaction was stirred for 1 hour and then the solvent was evaporated under reduced pressure to give a yellow solid This residue was dissolved in acetone (20cm 3 ), 4-bromo-l.l-difluorobut-l-ene (0.68g) was added and the reaction was stirred for 12 hours. The resulting mixure was poured into water and the layers separated. The aqueous layer was extracted with ethyl acetate. The combined organic phases were dried (MgS0 4 ), filtered and evaporated under reduced pressure. Purification by column chromatography on silica gel using 1:1 ethyl acetate : hexane as eluant gave Compound V.2, (0.88g). M ÷ =266; 'H NMR δ 2.50(2Rm); 3.20(2H,t); 4.20-4.40(1 Rm); (oil). The following coπφound according to the invention was prepared by the above procedure but using 2 equivalents of sodium sulfide nonahydrate and 4-bromo-l,l- difluorobut-1-ene: (i) 3,5-bis-(4,4-difluorobut-3-enylthio)-4-cyanoisothiazole (Coπφound V.12). 'H NMR δ 2.40-2.60(4H,m); 3.20(2H,t); 3.30(2H,t); 4.20-4.40(2Rm); (oil). EXAMPLE V.2 The Example illustrates a preparation of 5-(4,4-difluorobut-3-enylsulfonyl 4- cyanoisothiazole (Compound V.6) and 3,5-bis-(4,4-difluorobut-3-enylsulfonyl)-4- cyanoisothiazole (Compound V.15). To a solution of Compound V.12 (O.lg) in dichloromethane (5cm 3 ) was added 3- chloroperbenzoic acid (0.42g) and the reaction mixture was stirred until starting material had disappeared. The reaction mixture was poured into ethyl acetate and water and the layers were separated. The aqueous layer was extracted with ethyl acetate. The combined ethyl acetate phases were washed with sodium hydrogen carbonate, dried (MgS0 4 ), filtered and evaporated under reduced pressure. The residue was taken up in diethyl ether and triethylamine was added causing the solution to become cloudy. The ether solution was then washed with water, dried (MgS0 4 ), filtered and evaporated. Purification of the residue by column chromatography on silica gel using 1:1 ethyl acetate : hexane as eluant gave Compound V.15 (0.01 g); M^lδ; 'H NMR δ 2.60-2.70(4Rm); 3.60(4H,t); 4.30(2H,m); (oil) and Compound V.6 (0.08g); NT=264; 'H NMR δ 2.60(2Rm); 3.60(2Rt); 4.30(lRm); 9.40(lRs); (oil). EXAMPLE VI.1 Oxazoles substituted with a 4,4-difluorobut-3-enylthio group in the 2, 4 or 5-position may be prepared starting from a correspondingly substituted mercapto-oxazole and an appropriate difluorobut-1-ene alkylating agent. This is illustrated by the following preparation of 2-(4,4-difluorobut-3-enylthio)-5-phenyloxazole (Compound VI.18). To a solution of 2-mercapto-5-phenyloxazole (0.44g) in acetone (15cm 3 ) was added 4,4-difluoro-3-butenyl 4-methyl-benzenesulfonate (0.7g) and potassium carbonate (0.369g) and the reaction was heated at reflux for a total of 8 hours after which time some of the starting tosylate remained Further 2-mercapto-5-phenyloxazole (0.05g) was added and the heating continued for 5 hours. The reaction mixture was cooled, poured into diethyl ether and water and the layers separated. The aqueous layer was extracted with ether and the combined organic phases were dried (MgS0 4 ) and evaporated under reduced pressure to give a yellow liquid. Chromatography on silica gel using 5% tert-butyl dimethyl ether in hexane gave Coπφound VI.18; M + =267; 'H NMR (CDC1 3 ) δ 2.51(2Rm); 3.23(2R ); 4.30(lH,m); 7.23-7.47(4Rm); 7.58(2H,d); (oil). The following compounds according to the invention were prepared by the above procedure: (i) 2-(4,4-difluorobut-3-enylthio>oxazole (Compound VI.1). 'H NMR (CDC1 3 ) δ 2.45(2H,m); 3.20(2H,t); 4.25(lH,m); 7.10(lH,s); 7.66(lRs); (oil) from oxazole-2- thione. (ii) 2-(4,4-difluorobut-3-enylthio 4-methyloxazole (Compound VI.6). M + 205; 'H NMR δ : 2.04(3Rs); 2.45(2Rm); 3.18(2H,t); 4.25(lH,m); 7.38(lRq); (oil) from 2- mercapto-4-methyloxazole. EXAMPLE VT.2 This Exanφle illustrates a 3-step preparation of methyl 2-(4,4-difluorobut-3-enylthio)- 4-methyloxazole-5-carboxylate (Conφound VI.32). Step 1 : Methyl 2-amino-4-methyloxa7 )le-5-carhoxylate. Methyl 3-chloroacetoacetate (75g) and urea (90g) in methanol (200cm 3 ) were stirred and heated to reflux for 24 hours. The reaction mixture was cooled to ambient temperature and the precipitate filtered from solution, washed with cold methanol and sucked to dryness. This solid was treated with aqueous 2M sodium hydroxide and the product extracted into ethyl acetate (several portions). Evaporation of solvent under reduced pressure gave a colourless solid (14.5g) which was recrystallised from acetonitrile, mp 225°C (dec.) Η NMR (DMSO-de): δ 2.15(3Rs); 3.75(3Rs); 7.4(2H,br). Step 2: Methyl 2-chloro-4-methyloxazple-5-carboxylate. The product from Step 1 (1.56g) was partially dissolved in dry acetonitrile (40cm 3 ) and added in portions at 8°C to a stirred mixture of copper (Tl) chloride (1.61g) and tertiary butyl nitrite in acetonitrile (dry, 20cm 3 ) under an atmosphere of nitrogen. The resulting brown solution was stirred at 20°C for 2 hours and evaporated under reduced pressure. The residue was treated with aqueous 2M hydrochloric acid, and the product extracted into diethyl ether. The organic phase was dried (MgS0 4 ) and then washed through a short column of silica gel with more ether. The filtrate was evaporated under reduced pressure to give the required intermediate (0.9g) as a yellow solid. M * =175. Step 3: Methyl 2-(4.4-difluorobut-3-enylthioV4-methvloxazole-5-carboxvlate The product from Step 2 (0.176g) and thiourea (0.084g) were stirred in ethanol (5cm 3 ) and heated to reflux under an atmosphere of nitrogen for 5 hours. The reaction was cooled and solvent removed by evaporation under reduced pressure to give a yellow gum which was dissolved in acetone containing 4-bromo-l,l-difluorobut-l-ene (0.17g) and potassium carbonate (0.2g). This mixture was stirred for 1 hour under an atmosphere of nitrogen at ambient teπφerature and stored for 18 hours. The solvent was evaporated under reduced pressure and the residue treated with water and diethyl ether. The organic phase was separated, dried (MgS0 4 ) and evaporated to give Coπφound VI.32 (0.095g); NT =175. 'H NMR: δ 2.45(5H,m); 3.22 (2Rt); 3.90(3Rs); 4.25(lRm); (oil). EXAMPLE VI.3 This Example illustrates a preparation of 2-(4,4-difluorobut-3-enylthio)-4- methyloxazole-5-carboxylic acid (Coπφound VI.37). Compound VI.32 (0.4g) was dissolved in propan-2-ol (10cm 3 ) containing aqueous sodium hydroxide (2cm 3 of 2M solution) and stirred for 5 hours at ambient temperature. The mixture was evaporated under reduced pressure and the residue diluted with water, extracted with ethyl acetate, acidified with dilute hydrochloric acid and re-extracted with ethyl acetate (3x100cm 3 ). The latter extracts were combined, washed with saturated brine, dried (MgS0 4 ) and evaporated under reduced pressure to give the required product as a colourless solid (0.3g). M + =249; Η NMR: δ 2.5(5Rm); 3.27(2H,t); 4.27(lH,m); 6.5(lH,br s); (mp 66-68°C). The sodium salt of this coπφound was prepared by treating a sample (0.7g) with a solution of sodium methoxide in dry methanol (0.06 lg of sodium metal dissolved in methanol (10cm 3 )) at ambient temperature. Evaporation of solvent under reduced pressure gave the sodium salt of Compound VI.37 as a colourless solid; M " (FAB)=271; (mp 211-212°C). The following compound according to the invention was prepared by the above procedure: (i) 2-(4,4-difluorobut-3-enylt o)-4-trifluoromethyloxazole-5-carboxylic acid (Compound VI.36). M + =303; 'H NMR: δ 2.54(2H,m); 3.32(2H,t); 4.28(lRm) 7.65(lH,br s) from Compound VI.31. EXAMPLE VI.4 This example illustrates a preparation of 2-(4.4-difluorobut-3-enylthio)-4- trifluoromethyloxazole (Compound VI.4). 2-Amino-4-trifluoromethyloxazole (0.84g) in dichloromethane (25cm 3 ) containing bis- (4,4-difluorobut-3-enyl)disulfide (2.71 g) at 0°C was stirred and treated dropwise with tert. butyl nitrite (0.62g) under nitrogen. The reaction solution was evaporated under reduced pressure and the residue fractionated by chromatography (silica, eluant hexane) to give Compound VI.4 (0.35g). M + =259; 'H NMR: δ 2.50(2Rm); 3.26(3H,t); 4.28(lH,m); 7.95(lRq); (oil). The following coπφound according to the invention was prepared by the above procedure from the corresponding aminooxazole: (i) Ethyl 2-(4,4-difluorobut-3-enylthio)-4-trifluoromethyloxa2»le-5-carboxylate (Coπφound VI.31). MH + =322; 'H NMR: δ 1.40(3H,t); 2.52(2H,m); 3.30(2H,m); 4.28(1 H,m); 4.43(2H,q); (oil) from ethyl 2-amino-4-trifluoromethyloxazole-5- carboxylate (prepared from ethyl 1,1,1-trifiuoromethylacetoacetate and urea in a procedure analogous to Exanφle VI.2). EXAMPLE VT.5 This Example illustrates a preparation of 2-(4,4-difluorobut-3-enylthio)-5- chlorooxazole (Coπφound VI.13). Compound VI.1 (2.0g) was dissolved in acetonitrile (50cm 3 ) containing N- cWorosuccinirnide (1.50g) and stirred at ambient temperature for 24 hours. The mixture was evaporated under reduced pressure, extracted with hexane (50cm 3 ), filtered and the filtrate evaporated under reduced pressure. The residue was fractionated by chromatography (silica; eluant 20% diethyl ether in hexane) to give Coπφound VI.13 (0.75g). M + =225; 'H NMR: δ 2.46(2Rm); 3.16(2Rt); 4.28(lH,m); 6.86(lH,s); (oil). The following coπφound according to the invention was prepared from Coπφound VI.6 by the above procedure: (i) 2-(4,4-difluorobut-3-enylthio)-4-methyl-5-chlorooxazole (Compound VI.15). M =239; 'H NMR: δ 2.05(3H,s); 2.45(2Rm); 3.15(2H,t); 4.25(lRm); (oil). EXAMPLE VI.6 This Example illustrates a preparation of 2-(4,4-difluorobut-3-enylthio)-4- methyloxazole-5-carboxamide (Compound VI.40). Compound VI.32 (1.5g) was dissolved in methanol (10cm 3 ) and treated with aqueous ammonia (35cm 3 , density 0.88) at ambient temperature. The mixture was stirred for 5 hours, diluted with brine and the product extracted into ethyl acetate (2x100cm 3 ). The combined organic phases were washed with brine (4x50cm 3 ), dried (MgS0 4 ) and evaporated under reduced pressure; the residue was washed with hexane to give Coπφound VI.40 (lg). M"=248; 'H NMR (DMSO-cL): δ 2.50(5Rm); 3.26(2H,t); 3.85(3Rs); 4.28(lRm); 5.6, 6.0 (2Rbr s); (mp 72-73°C). EXAMPLE VI.7 This Example illustrates a preparation of 5-cyano-2-(4,4-difluorobut-3-enylthio)-4- methyloxazole (Coπφound VI.25). Coπφound VI.40 (0.64g) was dissolved in dichloromethane (10cm 3 ) containing dry pyridine (1cm 3 ) at ambient temperature and treated with methane sulfonyl chloride (0.5cm 3 ). The solution was stirred for 5 hours, stored for 72 hours, further methane sulfonyl chloride (0.25cm 3 ) and pyridine (0.5cm 3 ) added, stirred for 8 hours, and stored for 48 hours. The mixture was treated with dilute hydrochloric acid, and the product extracted into ethyl acetate. The combined organic phase was washed with brine and dried (MgS0 4 ). After filtration, the solvent was evaporated under reduced pressure and the residue fractionated by chromatography (silica; eluant 10% ethyl acetate in hexane) to give Coπφound VI.25 (0.46g). M + =230; Η NMR δ 2.32(3Rs); 2.50(2Rm); 2.58(3Rs); 3.25(2Rt); 3.85(3H,s); 4.28(lRm); (oil). EXAMPLE VT.8 This Example illustrates a preparation of N-methylsulfonyl 2-(4,4-difluorobut-3- enylthio)-4-methyl-oxazolecarboxamide (Compound VI.38). The sodium salt of Coπφound VI.37 (0.52g) was stirred in hexane (6.5cm 3 ) and treated with oxalyl chloride (0.275g) at ambient temperature. The mixture was stirred for 6 hours, stored for 18 hours and evaporated under reduced pressure. The residue, containing the oxazole carbonyl chloride derivative, was treated with a solution of methane sulfonamide (0.20g) in dry butan-2-one (5cm 3 ), heated under reflux with stirring for 8 hours, cooled to ambient temperature and stored for 18 hours. The mixture was evaporated under reduced pressure, the residue dissolved in water, acidified with 2M hydrochloric acid and the product extracted into diethyl ether (2x150cm 3 ). The ether extracts were combined, washed with aqueous saturated sodium chloride, dried (MgS0 4 ), evaporated under reduced pressure and the residue purified by chromatography, (silica; eluant acetonitrile), to give Compound VI.38 (0.20g). M"=326; Η NMR: δ 2.50(5H,m); 3.27(2H,t); 3.40(3Rs); 4.28(lRm); (mp 60- 62°C). EXAMPLE VI.9 This Example illustrates a preparation of 2-(4,4-difluorobut-3-enylsulfinyl)-5- phenyloxazole (Compound VI.19). To a solution of Compound VI.18 (lg) in dichloromethane (40cm 3 ) was added 3- chloroperbenzoic acid (1.3g of a 50% by weight solid, (1 eq)) and the reaction was stirred at ambient temperature for 5 hours. The reaction mixture was poured into a mixture of diethyl ether and aqueous sodium bicarbonate and the layers separated The organic layer was dried (MgS0 4 ) and evaporated under reduced pressure to give a white solid which was purified by chromatography on silica gel, eluting with 1 :4 ethyl acetate : hexane to give Coπφound VI.19 (0.567g). M + =283; 'H NMR: δ 2.50(2H,m); 3.41(2H,t); 4.29(lRm); 7.27(lRs); 7.38- 7.55(3H,m); 7.71(2Rd); (oil). The following compounds were prepared from the corresponding thioethers by the general method described above but using 2 equivalents of 3-chloroperbenzoic acid: (i) 2-(4,4-difluorobut-3-enylsulfonyl)-4-trifluoromethyloxazole (Compound VI.5). 'H NMR: δ 2.65(2H,m); 3.58(2H,t); 4.28(lRm); 8.24(lRq); (oil), (ii) 5-chloro-2-(4,4-difluorobut-3-enylsulfonyl)oxazole (Coπφound VI.14). MNR; + =275; 'H NMR: δ 2.60(2H,m); 3.47(2H,t); 4.26(lRm); 7.18(lRs); (oil), (iii) 5-chloro-2-(4,4-difluorobut-3-enylsulfonyl)-4-methyloxazole (Compound VI.16). Η NMR: δ 2.25(3Rs); 2.60(2Rm); 3.45(2H,t); 4.26(lRm); (oil), (iv) 2-(4,4-difluorobut-3-enylsulfonyl 5-phenyloxazole (Compound VI.20). MT=299; 'H NMR: δ 2.62(2H,m); 3.51(2H,t); 4.27(lH,m); 7.26(lRs); 7.42-7.55(3H,m); 7.69- 7.79(2Rd); (mp 55-59°C). EXAMPLE Vπ.l This Example illustrates a general method for the preparation of thiazoles substituted with a 4,4-difluorobut-3-enylthio group in the 2, 4 or 5-position starting from a correspondingly substituted mercapto thiazole and an appropriate difluorobut-1-ene alkylating agent. This is demonstrated by the following preparation of 2-(4,4-difluorobut-3-enylthio)-5- phenylthiazole (Compound Vπ.17). To a solution of 2-mercapto-5-phenylthiazole (0.483g) in acetone (15cm 3 ) was added 4,4-difluoro-3-butenyl 4-methyl-benzenesulfonate (0.7g) and potassium carbonate (0.369g) and the reaction was heated at reflux for a total of 8 hours after which time some of the starting tosylate remained. Further 2-mercapto-5-phenylthiazole (0.05g) was added and the heating continued for 5 hours. The reaction mixture was cooled, poured into diethyl ether and water and the layers separated. The aqueous layer was extracted with ether and the combined organic phases were dried (MgS0 4 ) and evaporated under reduced pressure to give a yellow liquid. Chromatography on silica gel using 5% tert-butyl dimethyl ether in hexane gave Coπφound VH.17 (0.582g). M + =283; 'H NMR: δ 2.51(2Rm); 3.31(2Rt); 4.32(lRm); 7.26(lRs); 7.30-7.48(3H,m); 7.89(2Rd); (oil). The following compounds according to the invention were prepared by the above procedure: (i) 2-(4,4-difluorobut-3-enylthio)-thiazole (Coπφound VH.l). M + =207; 'H NMR: δ 2.47(2Rm); 3.26(2Rt); 4.27(lRm); 7.22(lRd); 7.68(lRd); (oil) from 2- mercaptothiazole. (ii) 2-(4,4-difluorobut-3-enylthio thiazoline (Compound VH.134). M"=209; 'H NMR: δ 2.40(2H,m); 3.15(2H,t); 3.4(2H,t); 4.18-4.3 l(lRm); 4.2(2Rt); (oil) from 2- mercaptothiazoline. EXAMPLE Vπ.2 This Exanφle illustrates a two-step preparation of 2-(4,4-difluorobut-3-enylthio)-4- trifluoromethylthiazole (Compound VH.4). Step 1: Preparation of 2-mercapto-4-trifluoromethylthia7f)le l-Bromo-3,3,3-trifluoropropan-2-one (5.0g) in tert. butanol (20cm 3 ) was treated with ammonium dithiocarbamate (2.9g), the mixture stirred at ambient temperature for 18 hours, poured into water, extracted with ethyl acetate and the organic phase dried (MgS0 4 ). The solvent was evaporated under reduced pressure and the residue fractionated by chromatography (silica; eluant hexane:ethyl acetate 17:3 to 7:3 by volume) to give a hydrate (2.16g) of the required mercaptothiazole. A portion (l.Og) of this material was added to toluene (20cm 3 ) containing para toluene sulfonic acid (0.005g, catalyst) and heated under reflux for 4 hours. The water formed during the reaction was removed using a Dean-Stark apparatus. The solution was cooled to ambient teπφerature, washed with water, dried (MgS0 4 ) and evaporated under reduced pressure to give the required intermediate product (0.37g); 'H NMR: δ 7.10(lH,s); 7.80(lH,s). Step 2: Preparation of Compound VII.4 The product from Step 1 (0.37g) in acetone (15cm 3 ) containing anhydrous potassium carbonate (0.3g) and 4-bromo-l,l-difluorobut-l-ene (0.34g) were stirred and heated under reflux for 4 hours. The mixture was cooled, poured into water, extracted with ethyl acetate, dried (MgS0 4 ) and evaporated under reduced pressure to give Compound VH.4 (0.30g). M * =275; 'H NMR: δ 2.50(2Rm); 3.32(2Rt);4.28(lRm);7.60(lRs); (oil). The following coπφounds according to the invention were prepared from the corresponding mercaptothiazoles using Step 2 of the above procedure: (i) Ethyl 2-(4,4-dfluorobιrt-3-enylthio)thiazole-4-carboxylate (Coπφound Vπ.8). Η NMR: δ 1.40(3H,t); 2.48(2Rm); 3.32(2Rt); 4.28(lRm); 4.40(2H,q); 8.03(lRs); (oil) from ethyl 2-mercaptothiazole-4-carboxylate. (ii) Methyl 2-(4,4-difluorobut-3-enyltWo)-4-memylthia2»le-5-carboxylate (Conφound Vπ.41). 'H NMR: δ 2.48(2Rm); 2.68(3Rs); 3.26(2Rt); 3.85(3Rs); 4.28(lRm); (oil) from methyl 2-mercapto-4-methylthiazole-5-carboxylate. (iii) 2-(4,4-difluorobut-3-enylthio>5-nitrothiazole (Coπφound Vπ.47). M + =252; 'H NMR: δ 2.52(2Rm); 3.35(2Rm); 4.27(lRm); 8.35(lRs); (oil) from 2-mercapto-5- nitrothiazole (obtained from 2-bromo-5-nitrothiazole and thiourea). EXAMPLE .3 This Example illustrates a three-step preparation of 5-cWoro-2-(4,4-difluorobut-3- enylthio)thiazole (Coπφound VH.24). Step 1 ; 2-f4-bromo-3.4.4-trifluorobutylthiolthiazole -Mercaptothiazole (11.7g) in acetone (30cm 3 ) containing l,4-dibromo-l,l,2- trifluorobutane (27.0g) was treated portionwise with anhydrous potassium carbonate (13.8g) under an atmosphere of nitrogen. The reaction was stirred for 1.5 hours, filtered and the insolubles washed with further acetone (4x25cm 3 ). The filtrate was evaporated under reduced pressure and the residue fractionated by chromatography (silica, eluant 10% ethyl acetate in hexane) to give 2-(4-bromo-3,4,4-trifluorobutylthio)thiazole (29.5g). Η NMR: δ 22- 2.5(2H,m); 3.2-3.6(2Rm); 4.7-5.0(lRm); 7.23(lRd); 7.68(lRd). Step 2; 2-r4-bromc 3A4-trifluorobutylthioV5-chlorothiazole The compound from Step 1 (30.6g) in dichloromethane (130cm 3 ) was treated at ambient temperature with sulfuryl chloride (9.6cm 3 ) in dichloromethane (30cm 3 ) over 1 hour with stirring under an atmosphere of nitrogen. The reaction was stirred for a further 1 hour, poured slowly into water (250cm 3 ) and stirred for 0.25 hours. The organic phase was separated, the aqueous phase extracted with dichloromethane (2x75cm 3 ), the combined organic phases washed with aqueous sodium hydrogen carbonate, brine and dried (MgS0 ). The solvent was evaporated under reduced pressure and the residue fractionated by chromatography (silica; eluant 5% diethyl ether in hexane) to give 2-(4-bromo-3.4,4- trifluorobutylthio>5-chlorothiazole (28.0g); Η NMR: δ 2.20-2.45 (2H,m); 3.25-3.50(2H,m); 4.70-5.0(lRm); 7.45(lRs); (oil). Step 3; Compound vπ.24 Zinc powder (33g) in water (600cm 3 ) was stirred with iodine (0.17g, catalyst), heated to 80°C and concentrated hydrochloric acid (0.5cm 3 ) added followed by the compound from Step 2 (125g) in portions over 1.5 hour under an atmosphere of nitrogen. Further zinc (16.6g), iodine (O.lg) and hydrochloric acid (0.6cm 3 ) were added over 4 hours in portions to conφlete the reaction. The mixture was cooled to ambient temperature, filtered through keiselghur using dichloromethane as solvent and the filtrate extracted with dichloromethane (5x250cm 3 ). The combined organic phases were dried (MgS0 4 ), evaporated under reduced pressure and the residue fractionated by chromatography on silica, eluting with hexane to give Coπφound VH.24 (140g). M + =241; 'H NMR: δ 2.42(2H,m); 3.20(2H,t); 4.25(lRm); 7.45(lH,s); (oil). EXAMPLE Vπ.4 This Exanφle illustrates a preparation of 5-bromo-2-(4,4-difluorobut-3- enylthio)thiazole (Coπφound VH.14). 2-Amino-5-bromothiazole hydrobromide (llg) was treated with aqueous sodium hydrogen carbonate, extracted into dichloromethane (2x250cm 3 ) and dried (MgS0 4 ). The mixture was filtered and the filtrate added to bis-(4,4-difluorobut-3-enyl)disulfide (20g). Tert. butyl nitrite (9.6cm 3 ) in dichloromethane (40cm 3 ) was added dropwise to the stirred solution at ambient teπφerature under an atmosphere of nitrogen. The reaction was stirred for 18 hours, evaporated onto silica, the residue added to a short column of silica which was eluted with (1) hexane and (2) hexane : diethyl ether, 20:1 by volume to give Compound Vπ.14 (6.4g). NT=285; 'H NMR: δ 2.46(2H,m); 3.24(3Rt); 4.27(lRm); 7.54(lH,s); (oil). EXAMPLE W5 This Exanφle illustrates a preparation of 2-(4,4-difluorobut-3-enylthio)-4- methylthiazole-5-sulfonyl fluoride (Compound VH.52) using an alternative diazotisation procedure to that given in Exanφle VH.4. 2-Amino-4-methylthiazole sulfonylfluoride (1.5g) in acetonitrile (10cm 3 ) was added dropwise to a stirred mixture of tert. butyl nitrite (1.65cm 3 ) and bis-(4,4-difluorobut-3- enyl)disulfide (2.25g) in acetonitrile (50cm 3 ) at 60°C under an atmosphere of nitrogen. The mixture was heated for 1 hour, evaporated under reduced pressure and the residue fractionated by chromatography (silica; eluant hexane : ethyl acetate 4:1 by volume) to give Coπφound VU.52 (1.84g). Η NMR: δ 2.50(2H,m); 2.68(3H,s); 3.32(2H,t); 4.28(lRm); (oil). The following coπφounds according to the invention were prepared from the corresponding aminothiazoles using the above procedure, (i) 2-(4,4-difluorobut-3-enylthio)-5-methylthiazole (Coπφound VH.21). M * =221; 'H NMR: δ 2.45(5Rm); 3.22(2Rt); 4.26(lRm); 7.30(lRs); (oil) from 2-amino-5- methylthiazole. (ii) 5-chloro-2-(4,4-difluorobut-3-enylthio)thiazole (Compound Vπ.24). =241; 'H NMR: δ 2.45(2H,m); 3.22(2H,t); 4.26(lH,m); 7.45(lH,s); (oil) from 2-amino-5- chlorothiazole in an alternative method to that of Exanφle W.3 above, (iii) 5-cWorc>-2-(4,4-difluorobut-3-enylthio)-4-methylthiazole (Coπφound Vπ.27). M + =255; Η NMR: δ 2.35(3Rs); 2.42(2Rm); 3.18(2Rt); 4.26(lRm); (oil) from 2- amino-5-chloro-4-methylthiazole. EXAMPT Vπ.6 This Example illustrates a two-step preparation of ethyl 5-bromo-2-(4,4-difluorobut-3- enylthio)thiazole-4-carboxylate (Compound VH.ll). Step 1 ; Preparation of ethyl 2-amino-5-hromothiazole^-carboxylate Ethyl 2-aminothiazole-4-carboxylate (5.0g) (prepared from ethyl bromopyruvate and thiourea by the procedure described in J. Med. Chem.. 1971, 14, 1075 for the corresponding oxazole) in concentrated hydrobromic acid (9cm 3 ) was stirred at ambient temperature and treated dropwise with bromine (3.2g), then heated to 60°C for 2 hours, neutralised with sodium carbonate and the product extracted into ethyl acetate. The organic phase was dried (MgS0 4 ) and evaporated under reduced pressure to give ethyl 2-amino-5-bromothiazole-4- caiboxylate (1.54g). MR=251; 'H NMR: δ 1.40(3H,t); 4.40(2H,t); 5.6(2H,br s). Step 2; Preparation of Compound Vπ.l 1 The product from Step 1 was treated in a diazotisation reaction, as described in Example VH.5 above and gave Coπφound VH.l l; M =357; 'H NMR: δ 1.40(3Rt); 2.50(2Rm); 3.30(2H,t); 4.30(lH,m); 4.45(2H,q); (oil). EXAMPLE Vπ.7 This Example illustrates a three-step preparation of N,N-diethyl 2-(4,4-difluorobut-3- enylthio)-4-methylthiazole-5-sulfonamide (Coπφound VH.56). Step 1 : N.N-Piethyl 2-acetamidcv4-methylthiazole-5-sulfonamide 2-Acetamido-4-methylthiazole-5-sulfonyl chloride (5.2g) in tetrahydrofuran (100cm 3 ) was stirred at ambient temperature and treated portionwise with diethylamine (4.5cm 3 ). The mixture was stirred for 4 hours, evaporated under reduced pressure and the residue extracted into ethyl acetate (200cm 3 ). washed with water (2x100cm 3 ), dried (MgS0 4 ) and re-evaporated under reduced pressure to give N,N-diethyl 2-acetamido-4-methylthiazole-5-sulfonamide (4.9g). 'H NMR: δ 1.20(6H,t); 2.28(3H,s); 2.57(3H,s); 3.32(4H,q); 9.7(lRbr s); (solid). Step 2; N.N-Diethyl 2-amino-4-methylthiazole-5-sulfonamide The product from Step 1 (2.5g) was dissolved in methanol (25cm 3 ) and cooled to 5°C with stirring under an atmosphere of nitrogen. Sodium methoxide in methanol (2cm 3 of 25% wt./vol. solution) was added dropwise and the mixture allowed to warm to the ambient temperature for 18 hours. The reaction was heated under reflux for 1 hour, cooled, diluted with water (250cm 3 ), extracted with diethyl ether (2x100cm 3 ), dried (MgS0 4 ) and evaporated under reduced pressure to give N,N-diethyl 2-amino-4-methylthiazole-5-sulfonamide (0.48g). M + 249; 'H NMR: δ 1.20(6H,t); 2.48(3Rs); 3.28(4Rq); 5.25(2H,br s); (solid). Step 3; Preparation of Compound Vπ.56 The product from Step 2 was treated in a diazotisation reaction, as described in Example VH.5 above and gave Coπφound VH.56; M + =356; 'H NMR: δ 1.15(6Rt); 2.45(2Rm); 2.60(3H,s); 3.25(2H,t); 3.26(4Rq); 4.25(lRm); (oil). EXAMPLE .8 This Example illustrates a preparation of 2-amino-5-(4,4-difluorobut-3- enylthio)thiazole (Compound VH.128) 4,4-Difluorobut-3-enylisothiouronium hydrobromide (16.87g) was added to a solution of potassium hydroxide (lδ.Og) in ethanol (150cm 3 ) at ambient teπφerature and stirred for 0.2 hours under an atmosphere of nitrogen. 2-Amino-5-bromothiazole hydrobromide (17.76g) in ethanol (150cm 3 ) was added in portions, the mixture heated to 40°C for 2 hours, neutralised with hydrochloric acid and evaporated under reduced pressure. The residue was dissolved in 2M hydrochloric acid, extracted with diethyl ether, basified with 2M sodium hydroxide and re-extracted with diethyl ether. The latter ether extracts were combined, dried (MgS0 4 ) and evaporated under reduced pressure to give Coπφound Vπ.128 (8.0g). IVf=222; 'H NMR: δ 2.28(2H,m); 2.67(2H,t); 4.24(lRm); 5.3(2Rtwo br s); 7.08(lRs); (mp 34.6- 35.4°C). EXAMPLE Vπ.9 This Example illustrates a preparation of 5-(4,4-difluorobut-3-enylthio)thiazole (Compound W82). Compound Vπ.128 (0.30g) was dissolved in dry tetrahydrofuran (14cm 3 ) and heated under reflux in an atmosphere of nitrogen. Tert. butyl nitrite (0.52cm 3 ) in tetrahydrofuran (8cm 3 ) was added dropwise over 0.25 hours, the mixture heated for 2 hours, further tert. butylnitrite (0.52cm 3 ) added and heating continued for a further 2 hours. The solution was cooled, evaporated under reduced pressure and the residue fractionated by chromatography (silica; eluant hexane : ethyl acetate 1:1 by volume) to give Coπφound VH.128 (0.1 Og) 'H NMR: δ 2.28(2H,m); 2.82(2H,t); 4.24(lH,m); 7.86(lH,s); 8.86(lH,s); (oil). EXAMPLE vπ.10 This Example illustrates a preparation of 2-chloro-5-(4,4-difluorobut-3- enylthio)thiazole (Coπφound VH.114). Compound VH.128 (4.0g) in acetonitrile (50cm 3 ) was added at 0°C to a stirred mixture of copper TI) chloride (5.38g) and tert. butyl nitrite (3.71 g) in acetonitrile (50cm 3 ) and allowed to slowly warm to ambient temperature over 18 hours. The solvent was evaporated under reduced pressure, the product dissolved in diethyl ether, filtered and the filtrate re-evaporated to give a yellow-brown liquid which was fractionated by chromatography (silica; eluant hexane : diethyl ether 4:1 by volume) to give Compound Vπ.114 (2.43g). M + =241; 'H NMR: δ 2.28(2H,m); 2.68(2H,t); 4.22(lH,m); 7.52(lH,s) (oil). EXAMPLE 11 This Exanφle illustrates a preparation of 2-(4-cyanophenoxy)-5-(4,4-difluorobut-3- enylthio) thiazole (Compound VH.130). Compound VH.114 (0.483g), 4-cyanophenol (0.238g), anhydrous potassium carbonate (0.276g) and cesium fluoride (0.304g) in N-methylpyrrolidin-2-one (3cm 3 ) were stirred together under an atmosphere of nitrogen and heated to 90°C for 36 hours. The reaction mixture was diluted with water, the product extracted into diethyl ether, dried (MgS0 4 ), - evaporated under reduced pressure and the residue fractionated by thick layer chromatography (silica; eluted with hexane : diethyl ether 4:1 by volume) to give Coπφound Vπ.130 (0.125g). 'H NMR: δ 2.28(2H,m); 2.80(2H,t); 4.20(lRm); 7.40(2Rm); 7.75(2H,m); (oil). EXAMPLE .12 This Example illustrates a preparation of ethyl 5-(4,4-difluorobut-3-enylthio)-thiazole- 4-carboxylate (Compound VΗ.98). Ethyl isocyanoacetate (2.3g) in dry tetrahydrofuran (15cm 3 ) was added to a stirred mixture of potassium tert. butoxide (2.24g) at -40°C under an atmosphere of nitrogen. After 10 minutes the reaction was cooled to -78°C and carbon disulfide (1.52g) in tetrahydrofuran (20cm 3 ) was added slowly. On complete addition the reaction temperature was allowed to rise to -10°C and 4,4-difluorobut-3-enyl 4-methyl-benzenesulfonate (5.24g) in tetrahydrofuran (10cm 3 ) was added The mixture was allowed to warm to ambient temperature and was stirred for 24 hours, heated to reflux for 3 hours and cooled to ambient temperature. The reaction mixture was poured into aqueous 2M hydrochloric acid and product was extracted into ethyl acetate. The organic phase was dried (MgS0 4 ) and solvent removed by evaporation under reduced pressure. Column chromatography of the residue on silica gel, eluting with 1:1 hexane : ethyl acetate gave Coπφound VIL98 (3.15g). 'H NMR δ 1.45(3H,t); 2.50(2H,m); 3.10(2H,t); 4.3-4.4(lRm); 4.50(2H,q); 8.65(lH,s); (oil). EXAMPLE W 13 This Example illustrates a preparation of 5-(4,4-difluorobut-3-enylthio)-thiazole-4- carboxamide (Compound VII.94). Compound VIL98 (0.5g) in methanol (8cm 3 ) was stirred with aqueous ammonia (35cm 3 ; density 0.88) for 4 hours. Compound VEL94 was obtained as a solid which was filtered from solution and sucked to dryness (0.27g). 'H NMR δ 2.50(2Rm); 3.00(2Rt); 4.30-4.41(lH,m); 5.5 and 7.0(2H,broad); 8.55(lH,s); (solid mp 140-141°C). The following compounds according to the invention were prepared from the corresponding esters using the above procedure: (i) 2-(4,4-ώfluorobut-3-enylthio)thiazole-4-carboxamide (Coπφound VII.7). M f =250; 'H NMR: δ 2.50(2H,m); 3.27(2Rt); 4.28(lH,m); 5.9 and 7.1(2H,br s); 8.03(lRs); (mp 57-58°C) from Compound VH.8. (ii) 2-(4,4-difluorobut-3-enyltlu^)-4-methylthiazole-5-<^rboxamide (Coπφound VII.36). 'H NMR: δ 2.48(2H,m); 2.66(3H,s) 3.26(2H,t); 3.85(3H,s); 4.28(lH,m); 5.7(2Rbr s); (mp 99-100°C) from Compound VIL41. EXAMPLE Vπ.14 This Example illustrates a preparation of 4-cyano-5-(4,4-difluorobut-3-enylthio)- thiazole (Compound VH.90). Compound VII.94 (0.27g) in dry dichloromethane (13cm 3 ) was treated with pyridine (lcm 3 ) and methane sulfonyl chloride (0.26cm 3 ) .The mixture was stirred for 5 days, further methane sulfonyl chloride (0.2cm 3 ) added and again stirred for 2 hours. The reaction was then poured into aqueous 2M hydrochloric acid and the product was extracted into ethyl acetate. The organic phase was dried (MgS0 4 ) and evaporated under reduced pressure. Chromatography of the residue on silica gel gave Compound VII.90 (0.142g). 'H NMR δ 2.40(2H,m); 3.20(2Rt); 4.30(lRm); 8.80(lH,s). The following compounds according to the invention were prepared from the corresponding carboxamides using the above procedure: (i) 4-cyano-2-(4,4-difluorobut-3-enylthio)thiazole (Compound VII.6). 'H NMR: δ 2.50(2H,m); 3.32(2Rt); 4.26(lRm); 7.86(lH,s); (oil) from Coπφound Vπ.7. (ii) 5-cyano-2-(4,4-difluorobut-3-enylthio)-4-methylthiazole (Compound VII.32). 'H NMR: δ 2.48(2H,m); 2.58(3H,s) 3.30(2H,t); 3.85(3H,s); 4.28(lH,m); (oil) from Compound VIL36. EXAMPLE Vπ.15 This Exanφle illustrates a preparation of 5-bromo-2-(4,4-difluorobut-3- enylthio)thiazole-4-carboxylic acid (Coπφound VH.13). Compound Vπ.l l (0.30g) in methanol (5cm 3 ) containing aqueous sodium hydroxide (1.2cm 3 of a 2M solution) was stirred at ambient temperature for 18 hours, poured into water and acidified with 2M hydrochloric acid The product was extracted into ethyl acetate, dried (MgS0 4 ) and evaporated under reduced pressure to give Coπφound VII.13 (0.18g). M + =329; 'H NMR δ 2.48(2H,m); 3.30(2H,t); 4.28(lH,m); 7.0(lH,broad signal); (mp 86.5-87.5°C). The following coπφounds according to the invention were prepared from the corresponding esters using the above procedure: (i) 2-(4,4-difluorob -3-enyltlιio)thia2»le-4-carboxylic acid (Coπφound VII.10). M 251; 'H NMR: δ 2.50(2H,m); 3.35(2Rt); 4.28(lRm); 8.18(lH,s); (mp 114-115°C) from Coπφound Vπ.8. (ii) 2-(4,4-difluorobut-3-enylt o)-4-methylthiazole-5-carbo?tylic acid (Compound VII.45). M + =265; 'H NMR δ 2.50(2Rm); 2.70(3Rs); 3.27(2Rt); 4.28(lH,m); 9.8(lRbroad signal); (mp 52.0-53.5°C) from Coπφound VIL41. (iii) 5-(4,4-difluorobut-3-enyltMo)thiazole-4-carboj^lic acid (Conφound VII.102). M + =251; 'H NMR: δ 2.50(2H,m); 3.10(2H,t); 4.28(lH,m); 8.70(lH,s); (mp 128.5°C) from Coπφound VQ.98. EXAMPLE Vπ.16 This Exanφle illustrates methods suitable for the preparation of coπφounds according to the invention in which the sulfur atom of the 4,4-difluorobut-3-enylthio substituent of the corresponding unoxidised compound is oxidised to sulfoxide (sulfinyl) or sulfone (sulfonyl). Method A: Using potassium peroxymonosulfate as oxidant. Preparation of 5-chloro-2-r4.4-difluorobut-3-eny1sulfonynthiazole rCompound VII.26) A stirred solution of Compound VII.24 (4.83g) in methanol (50cm 3 ) at 8°C was treated dropwise with potassium peroxymonosulfate (27.0g) in water (100cm 3 ) with cooling over 0.25 hours, and further methanol (50cm 3 ) added. The reaction was stirred for 18 hours at ambient teπφerature, the insolubles filtered from solution, the filtrate extracted with dichloromethane (4x50cm 3 ) and dried (MgS0 4 ). The solvent was removed under reduced pressure and the residue fractionated by chromatography (silica; eluant hexane : ethyl acetate 4:1 by volume) to give Compound VII.26 (3.91g). M(NH4) + =291; 'H NMR: δ 2.60(2Rm); 3.50(2H,t); 4.25(lH,m); 7.85(lRs); (oil). Method B: Using monomagnesium peroxyphthalic acid Preparation of 5-bromo-2-C4.4-difluorohut-3-enylsulfinyl >thiazole rCompound VII.151 Compound VII.14 (1.50g) was dissolved in dichloromethane (10cm 3 ) and treated with monomagnesium peroxyphthalic acid hexahydrate (1.6g, 80% peracid) and water (15cm 3 ). The mixture was stirred at ambient teπφerature for 1 hour, diluted with dichloromethane (90cm 3 ) and the organic phase washed with aqueous sodium hydrogen carbonate and water. The organic phase was dried (MgS0 4 ), evaporated under reduced pressure and the residue fractionated by chromatography (silica; eluant hexane : ethyl acetate 10:1 by volume) to give Coπφound Vπ.15 (l.Og). M(NH4) + =321; 'H NMR: δ 2.38 (Him); 2.60(lH,m); 3.20(2H,m); 4.20(lH,m); 7.85(lH,s); (oil). The following coπφounds according to the invention were prepared from the corresponding thioethers using the above procedure, Method B. (i) 2-(4,4-difluorobut-3-enylsulfinyl)thiazole (Coπφound W2). MH + =224; 'H NMR: δ 2.36(lH,m); 2.50-2.70(lH,m); 3.20(2H,m); 4.22(lRm); 7.67(lRd); 7.98(lRd); (oil) from Compound Vπ.l and one equivalent of oxidant (ii) 2-(4,4-difluorobut-3-enylsulfonyl)thiazole (Coπφound VII.3). MH + =240; 'H NMR: δ 2.55(2Rm); 3.45(2H,t); 4.24(lH,m); 7.78(lH,d); 8.08(lH,d); (oil) from Compound Vπ.l and two equivalents of oxidant. (iii) 5-bromo-2-(4,4-difluorobut-3-enylsulfonyl)thiazole (Coπφound VII.16). M(NH4) + =335; Η NMR: δ 2.58(2Rm); 3.46(2H,t); 4.25(lRm); 7.96(lH,s); (oil) from Compound VII.14 and two equivalents of oxidant. (iv) 2-(4,4-difluorobut-3-enylsulfinyl 5-methylthiazole (Compound VH.22). 'H NMR: δ 2.38(lRm); 2.50-2.65(4H,m); 3.15(lH,m); 4.23(lH,m); 7.60(lH,q); (oil) from Compound VII.21 and one equivalent of oxidant. (v) 2-(4,4-difluorobut-3-enylsulfonyl)-5-methylthiazole (Coπφound Vπ.23). 'H NMR: δ 2.55(2H,m); 2.60(3H,s); 3.45(2H,t); 4.25(lRm); 7.73(lRq); (oil) from Coπφound Vπ.21 and two equivalents of oxidant. (vi) 5-cWorcπ2-(4,4- fluorobut-3-enylsulfinyl)thiazole (Compound VII.25). M(NH4) + =275; 'H NMR: δ 2.38(lH,m); 2.60(lRm); 3.18(2H,m); 4.25(lRm); 7.74(lH,s); (oil) from Compound VII.24 and one equivalent of oxidant. (vii) 5-(4,4-difluorobut-3-enylsulfinyl)thiazole (Compound VII.83). 'H NMR: δ 2.50(2H,m); 3.05(lRm); 3.20(lH,m); 4.28(lH,m); 8.20(lH,s); 9.12(lRs); (oil) from Compound VD 82 and one equivalent of oxidant. (viii) 5-(4,4-difluorobut-3-enylsulfonyl)thiazole (Coπφound VTI.84). 'H NMR: δ 2.50(2Rm); 3.30(2H,m); 4.25(lH,m); 8.20(lH,s); 9.12(lH,s); (oil) from Compound Vπ.82 and two equivalents of oxidant. (ix) 2-cWoro-5-(4,4-difluorobut-3-enylsulfinyl)thiazole (Coπφound VII.115). 'H NMR: δ 2.50(2H,m); 3.05(lH,m); 3.20(lH,m); 4.28(lRm); 7.85(lRs); (oil) from Coπφound VII.114 and one equivalent of oxidant. (x) 2-cWorc>5-(4,4-dffluorobιιt-3-enylsιιlfonyl)^ 'H NMR: δ 2.52(2H,m); 3.30(2Rm); 4.28(lH,m); 8.08(lH,s); (oil) from Coπφound VH.114 and two equivalents of oxidant. Method C: Using 3-chloroperbenzoic acid The following coπφounds according to the invention were prepared from the corresponding thioethers using the above procedure, Method B, but with 3-chloroperbenzoic acid in place of monomagnesium peroxyphthalic acid hexahydrate. (xi) ethyl 2-(4,4-difluorobut-3-enylsulfonyl)t azole-4-carboxylate (Coπφound VII.9). M-=311; 'H NMR: δ 1.43(3Rt); 2.60(2H,m); 3.56(2Rt); 4.28(lRm); 4.48(2H,q); 8.50(lH,s); (mp 64-65°C) from Compound VII.8 and two equivalents of oxidant. (xii) ethyl 5-bromch2-(4,4-difluorobut-3-enylsi-Ifonyl)thiazole-4-<^rboxylate (Coπφound Vπ.12). M =389; 'H NMR: δ 1.43(3Rt); 2.60(2Rm); 3.56(2H,t); 4.28(lH,m); 4.48(2H,q); ( p 72-73°C) from Coπφound VII.11 and two equivalents of oxidant. (xiii) 5-chloro-2-(4,4-difluorobut-3-enylsulfonyl)-4-methylthiazole (Compound VII.28). 'H NMR: δ 2.55(2H,m); 2.45(3H,s); 3.40(2H,t); 4.25(lH,m); (oil) from Coπφound Vπ.27 and two equivalents of oxidant. (xiv) methyl 2-(4,4-difluorobut-3-enylsulfonyl)-4-methylthiazole-5-carboj^late (Coπφound Vπ.43). 'H NMR: δ 2.60(2H,m); 2.85(3H,s); 3.50(2Rt); 3.95(3H,s); 4.25(lH,m); (oil) from Compound Vϋ.41 and two equivalents of oxidant. (xv) 2-(4,4-difluorobut-3-enylsulfonyl)-4-methylthiazole-5-sulfonyl fluoride (Compound Vπ.53). Η NMR: δ 2.60(2Rm); 2.85(3Rs); 3.55(2H,t); 4.28(lRm); (mp 67°C) from Compound VII.52 and two equivalents of oxidant. EXAMPLE Viπ.1 This Example illustrates a preparation of 2-(4,4-difluorobut-3-enylthio)-l- methylimidazole (Compound Vm.5). To a solution of 2-mercapto-l-methylimidazole (9.78g) in acetone (300cm 3 ) was added potassium carbonate (14.2g) and 4-bromo-l,l-difluorobut-l-ene (16.12g) as a solution in acetone (100cm 3 ). The mixture was heated at reflux for 18 hours and allowed to cool. Inorganic solids were removed by filtering the reaction mixture through a plug of sorbsil-C30 silica, washing with ethyl acetate. The filtrate was evaporated under reduced pressure to give crude Compound VQT.5 (17.8g), which was suitable for further reaction (see Exanφle vm.7). A portion (lg) was purified by chromatography on sorbsil C-30, eluting with ethyl acetate : hexane 3 : 7, and gave pure Compound VHI.5 (0.776g). 'H NMR: δ 2.3-2.4(2H,m); 3.05- 3.15(2H,t); 3.60(3H,s); 4.15-4.35(lH,m); 6.95(lH,s); 7.05(lH,s); (oil). The following coπφounds according to the invention were prepared by the above procedure, using the appropriate mercapto imidazole: (i) 2-(4,4-difluorobut-3-enylthio l-phenylimidazole (Coπφound Vm.3). M"=266; 'H NMR: δ 2.3-2.4(2H,m); 3.1-3.15(2H,t); 4.1-4.25(lH,m); 7.1-7.2(2H,m); 7.3- 7.55(5H,m); (oil), (ii) 2-(4,4-cUfluorobut-3-enylthio l-ethylimidazole (Cornpoιmd Vm.lO). JVT=218; 'H NMR: δ 1.4(3H,t); 2.3-2.4(2H,m); 3.15(2H,t); 4.0(2H,q); 4.2-4.35(lH,m); 6.95(lH,s); 7.1(lH,s); (oil), (iii) 2-(4,4-difluorobώ-3-enylthio)-4-e l-5-methylimidazole (Compound Vm.27). M =232; 'H NMR: δ 1.15(3Rt); 2.15(3H,s); 2.35-2.45(2H,m); 2.5-2.6(2H,q); 2.95(2H,t); 4.1-4.3(lH,m); (m.p. 54-56°C). (iv) 2-(4,4-difluorobut-3-enylthio)-4-methylimidazole (Compound Vm.58). M"=204; 'H NMR: δ 2.25-2.35(5Rm); 3.0(2H,t); 4.15-4.3(lH,m); 6.75(lH,s); (oil), (v) 2-(4,4-difluorobut-3-enylthio)-4-ethoxycarbonylimidazole (Compound Vm.64). ]vf=262; 'H NMR: δ 1.3-1.35(3H,t); 2.25-2.35(2H,m); 3.05-3.15(2H,t); 4.1- 4.25(lH,m); 4.3-4.4(2H,q); 7.8(lRbr s); (mp 57.8-61°C). (vi) 3-(4,4-difluorobut-3-enylthio)imidazo-[l,5a]-pyridine (Compound VHI.151). 'H NMR: δ 2.30 (2Rm); 3.00(2Rt); 4.20(lRm); 6.65(lRm); 6.80(lRm); 7.45(lRdt); 7.55(lRs); 8.15(lRdd); (oil) from 2.3-dihydroimidazo-[1.5a]-pyridine-3-thione. EXAMPLE Vm.2 This Exanφle illustrates a preparation of 2-(4,4-difluorobut-3-enylthio)-imidazole (Coπφound " VTfl.l) and l-(4,4-difluorobut-3-enyl)-2-(4,4-difluorobut-3-enylthio)imidazole (Coπφound Vm.8) as a mixture of products separable by chromatography. To a solution of 2-mercapto-imidazole (lO.Olg) in acetone (400cm 3 ) was added potassium carbonate (20.73 g) and 4-bromo-l,l-difluorobut-l-ene (18.79g). The mixture was heated at reflux for 18 hours and allowed to cool. Inorganic solids were removed by filtering the reaction mixture through a plug of sorbsil-C30 silica, washing with ethyl acetate. The filtrate was evaporated under reduced pressure to give a pale browm oil (19.2g) which was chromatographed on silica, eluting with 15% ethyl acetate in hexane, progressing to 50% ethyl acetate in hexane. Two main fractions were obtained, the first of which (7.4g) was shown by tic to contain two products. The second fraction (10.75g), obtained as a white solid, was shown to be pure Compound Vffl.l. The first fraction was subjected to further chromatography as before to give Coπφound Vm.8 (1.61g); M =280; 'H NMR: δ 2.3- 2.45(4H,m); 3.1-3.15(2Rt); 3.9-4.0(2H,t); 4.05^.3(2Rm); 6.95(lRs); 7.05(lH,s); (oil) and Compound Vm.l (5.3 lg). This sample of Compound Vm.l was recrystallised from ethyl acetate and hexane to provide 4.2g which had M 90; 'H NMR: δ 2.3-2.4(2H,m); 3.0- 3.1(2H,t); 4.15-4.3(lRm); 7.0-7. l(2H,br s); 9.2(lH,br s); (mp. 58.6-59.6°C). F5 AMPLE VTTT.3 This Example illustrates a preparation of 2-(4,4-difluorobut-3-enylthio)-4- phenylimidazole (Compound VEI.19). Phenacyl bromide (1.61 lg) in chloroform (7cm 3 ) was added to 4,4-difluorobut-3- enylisothiouronium hydrobromide (2g) in 84% ethanol/water (20cm 3 ) and sodium bicarbonate (2.72g) was slowly added with stirring. The resultant yellow suspension was heated under reflux for 3 hours. The mixture was cooled and solvent was removed by evaporation under reduced pressure. The residue was washed twice with warm water (2x20cm 3 ) which was decanted off to remove inorganic material. The crude product so obtained was purified by chromatography on silica, eluting with 20% ethyl acetate in hexane, and product-containing fractions were recolumned using 5% ethyl acetate in toluene. This gave Compound VHI.19 (0.78g); M * =266; 'H NMR: δ 2.3-2.4(2H,m); 3.05-3. l(2H,t); 4.15 3(lH,m); 7.2-7.4(4H,m); 7.6-7.75(2H,br s) free of a byproduct, the corresponding N-phenacyl derivative. The following compounds according to the invention were prepared by the above procedure: (i) 2-(4,4-difluorobut-3-enylthio)-l-methyl-4-phenylimidazole (Compound Vm.22). M + =280; 'H NMR: δ 2.35-2.45(2Rm); 3.10-3.18(2R ); 3.65(3Rs); 4.19-4.35(lRm); 7.2-7.25(2Rm); 7.33-7.38(2Rt); 7.72-7.78(2H,d) (oil) using N-methyl 4,4-difluorobut- 3-enylisothiouronium hydrobromide. (ii) 2-(4,4-difluorobut-3-enylthio)-5-ethyl-4-methoxycarbonyl- 1 -methylimidazole (Compound Vffl.68). M * =290; 'H NMR: δ 1.2-1.25(3Rt); 2.35-2.45(2H,m); 2.8- 2.9(2H,q); 3.2-3.25(2H,t); 3.78(3H,s); 3.85(3H,s); 4.16-4.32(lH,m); (oil) using N- methyl 4,4-difluorobut-3-enylisothiouronium hydrobromide and methyl 2-bromo-3- oxopentanoate. EXAMPLE VTTT.4 This Example illustrates a preparation of 2-(4,4-difluorobut-3-enylthio)-4,5- dimethylimidazole (Compound Vm.29). Potassium carbonate (18.9g) and 4,4-difluorobut-3-enylisothiouronium hydrobromide (16.9g) were added to a solution of 3-bromobutan-2-one (10.32g) in dimethyl formamide (100cm 3 ) and the mixture was stirred at 60°C for 90 minutes, then at 80°C for 30 minutes. The resulting mixture was cooled, water (100cm 3 ) added, and the product extracted into diethyl ether. The combined organic phases were washed with water and brine and dried (MgS0 4 ). Concentration by evaporation under reduced pressure gave a pale orange liquid (12.2g), which was purified by chromatography on sorbsil C30 silica, eluting with 30% ethyl acetate in hexane. Three components were obtained. The first eluted was identified as 3- (4,4-difluorobut-3-enylthio)butan-2-one (0.68g); M 94; 'H NMR: δ 1.4(3H,d); 2.15- 2.3(5H,m); 2.45(2H,t); 3.3-3.4(lRq); 4.1-4.35(lH,m). The second coπφound eluted was the desired Compound Vm.29 (4.1g); NT=218; 'H NMR δ 2.15(6Rs) 2.25-2.35(2H,m); 2.9- 3.0(2H,t); 4.15-4.3(lH,m); (mp 81.4-84.4°C). The third compound eluted was identified as the product of a further N-alkylation of Compound Vm.29 with additional 3-bromobutan-2- one, namely N-(l-methylprppan-2-one) 2-(4,4-difluorobut-3-enylthio)-4,5-dimethylimidazole (1.1 lg); 'H NMR: δ 1.55(3H,s); 2.0(3H,s); 2.05(3Rs); 2.15(3Rs); 2.3-2.4(2Rm); 3.0-3.05(2H,t); 4.15-4.35(lH,m); 5.0-5. l(lH,m); (oil). EXAMPLE V .5 This Example illustrates a preparation of 2-(4,4-difluorobut-3-enylthio)-l- propylimidazole (Compound Vffl.12) from the corresponding N-H imidazole, Coπφound Vm.l, by alkylation using propyl iodide. Compound Vffi.l (2g) was added in portions (effervescence) to a suspension of sodium hydride (0.736g of a 60% solid in oil) in dimethyl formamide (20cm 3 ) under a nitrogen atmosphere. After stirring the mixture for 30 minutes, n-propyl iodide (2.68g) was added and the reaction mixture was stirred at the ambient teπφerature for 18 hours. Water and diethyl ether were then added and the product extracted into ether. The combined organic phases were washed with water and saturated brine and dried (MgS0 4 ). After filtration, the solvent was removed by evaporation under reduced pressure to give crude product (2.7g) which was purified by chromatography on sorbsil C-30, eluting with ethyl acetate : hexane 3 : 7 and gave Coπφound Vm.12 (2.15g); M*=232; 'H NMR: δ 0.9- 0.95(3Rt); 1.75-1.85(2H,m); 2.3-2.45(2H,m); 3.1-3.15(2H,t); 3.85-3.95(2H,t); 4.15- 4.35(lRm); 6.9(lRs); 7.1(lRs); (oil). The following coπφounds according to the invention were prepared by the above procedure, using the appropriate alkylating agent and starting N-H imidazole: (i) 2-(4,4-difluorobm-3-enylthio>l-(l-methylethyl irnidazole (Coπφound Vm.14). M * =232; 'H NMR: δ 1.4(6Rd); 2.3-2.4(2Rm); 3.1-3.15(2Rt); 4.15-4.3(lH,m); 4.5- 4.6(lH,m); 7.0(lRs); 7.1(lRs); (oil) from Compound Vm.l. (ii) 2-(4,4-difluorobut-3-enylthio>l,4,5-trimethylimidazole (Coπφound Vm.31). 'H NMR: δ 2.15(6H,two s); 2.25-2.35(2H,m); 2.95(2H,t); 3.5(3H,s); 4.15-4.3(lRm); (oil) from Compound Vm.29. (iii) l-emyl-2-(4,4-difluorobιιt-3-enylthio)-4 5 5-dimethylimidazole (Coπφound Vm.33). 'H NMR: δ 1.25(3H,t); 2.15(6H,br s); 2.3-2.4(2H,m); 3.0(2H,t); 3.9-3.95(2H,q); 4.15- 4.3(lH,m); (oil) from Compound Vm.29. (iv) A mixture of 2-(4,4-difluorobut-3-enylthio)-l,5-dimethylirnidazole (Coπφound Vm.35) and 2-(4,4-difluorobut-3-enyltMo l,4-<iimethylimidazole (Compound Vm.60); 'H NMR: δ 2.15(3H,s); 2.3-2.4(2H,m); 3.0-3.05(2H,t); 3.5 and 3.55(3H,two s); 4.15-4.3(lH,m); 6.65 and 6.80(lH,two s) from Coπφound Vm.58. (v) A mixture of 2-(4,4-difluorobut-3-enylthio)-5-methyl-l-(l-methylethyl)-imidazole (Compound Vm.37) and 2-(4,4-difluorobut-3-enylthio)-4-methyl-l-(l-methylethyl • imidazole (Compound VIIL62); shown to be mainly the latter isomer, 'H NMR: δ 1.35(6H,d); 2.2(3Rs); 2.3-2.4(2Rm); 3.05(2H,t); 4.15-4.3(lRm); 4.5-4.6(lH,m); 6.70(lRs) from Compound VHI.58. (vi) 2-(4,4-difluorobut-3-enylthio 5-ethoxycan onyl-l-methylimidazole (Compound Vπi.52). M + =276; 'H NMR: δ 1.32-1.40(3Rt); 2.37-2.47(2Rm); 3.2-3.3(2Rt); 3.82(3Rs); 4.17-4.32(lRm); 4.25-4.35(2Rq); 7.7(lRs); (oil) from Coπφound Vm.64. This reaction produced a chromatographically separable mixture of Compound Vm.52 and Vm.65, the former eluting first, (vii) 2-(4,4-difluorobut-3-enylthio)-4-ethoxycarbonyl-l-methylimidazole (Compound Vm.65). M + =276; 'H NMR: δ 1.35-1.40(3Rt); 2.35-2.42(2H,m); 3.20-3.27(2H,t); 3.63(3Rs); 4.15-4.30(lRm); 4.3-4.4(2H,q); 7.60(lH,s); (oil) from Coπφound VHI.64. EXAMPLE v .6 This Example illustrates a preparation of 2-(4,4-difluorobut-3-enylthio)-N-(methane sulfonyl)imidazole (Compound Vm.18). A solution of Compound Vm.l (0.49g) in dry tetrahydrofuran (3cm 3 ) was added dropwise to a suspension of sodium hydride (55% in oil, 0.12g, washed with hexane prior to use) in dry tetrahydrofuran (5cm 3 ) cooled in a cold water bath. The reaction mixture was allowed to stir at the ambient temperature for 2 hours and then methanesulfonylchloride (0.3g) was added and the reaction stirred for a further 16 hours. The reaction mixture was poured into ethyl acetate/water and the layers separated The aqueous layer was extracted with ethyl acetate and the combined organic phases were dried (MgS0 4 ), filtered and evaporated under reduced pressure to give a yellow oil. Purification by column chromatography on silica gel using 3:7 ethyl acetate:hexane gave Compound Vm.18 (0.3 lg). ■ H NMR δ 2.40-2.50(2Rm); 3.30 (2Rt); 3.30(3Rs); 4.25(lRm); 7.05(lRd); 7.35(lH,d); (oil). EXAMPLE VTTT.7 This Example illustrates a method suitable for the preparation of coπφounds according to the invention in which the sulfur atom of the 4,4-difluorobut-3-enylthio substituent of the corresponding unoxidised coπφound is oxidised to sulfoxide (sulfinyl) or sulfone (sulfonyl). Preparation of Compound VHI.7 from Compound VTIL5. Compound VIII.5 (18.1g) was cooled to 0°C in dichloromethane (400cm 3 ) and 3- chloroperbenzoic acid (61.2g of water-wet solid, 2 equiv.) was added. The mixture was stirred at the ambient temperature for 18 hours and then poured into saturated aqueous sodium bicarbonate. The product was extracted into dichloromethane, the organic phase washed with water and saturated brine and dried (MgS0 4 ). Evaporation of solvent under reduced pressure gave crude Compound VH1.7 which was chromatographed on silica, eluting with 15% ethyl acetate in hexane, progressing to 50% ethyl acetate in hexane, to give pure Compound Vffl.7. Η NMR: δ 2.55-2.6(2H,m); 3.5-3.55(2R ); 4.0(3Rs); 4.15-4.3(lRm); 7.0(lRs); 7.15(lRs); (oil). The following compounds according to the invention were prepared by the above procedure of Example Vm., using two equivalents of oxidant unless otherwise specified, with the appropriate starting thioether: (i) 2-(4,4-difluorobut-3-enylsulfonyl>imidazole (Compound Vm.2). MR=223; 'H NMR: δ 2.4-2.6(2Rm); 3.4-3.45(2H,t); 4.1-4.3(lH,m); 7.3-7.4(3Rbr s); (white solid, mp. 113-114°C). (ii) 2-(4,4-difluorobut-3-enylsulfonyl l-phenylimidazole (Compound Vm.4). M"=298; 'H NMR δ 2.45-2.55(2H,m); 3.45-3.55(2H,t); 4.15-4.3(lH,m); 7.2(lRd); 7.25(lRd); 7.45-7.55(5H,m); (oil), (iii) 1 -(4,4-difluorobut-3-enyl)-2-(4,4-difluorobut-3-enylsulfonyl)-imidazole (Compound Vm.9). M + =312; 'H NMR: δ 2.5-2.65(4Rm); 3.5-3.6(2H,t); 4.1-4.35(2H,m); 4.4- 4.45(2Rt); 7.05(lRs); 7.15(lH,s); (oil), (iv) 2-(4,4-difluorobut-3-enylsulfonyl>l-ethylimidazole (Conφound Vm.ll). M + =250; 'H NMR: δ 1.5(3H,t); 2.5-2.65(2Rm); 3.5-3.6(2H,t); 4.15-4.35(lH,m); 4.4-4.45(2H,q); 7.05(lH,s); 7.15(lH,s); (oil), (v) 2-(4,4-difluorobut-3-enylsulfonyl)-l-propylimidazole (Compound Vm.13). MH + =265; 'H NMR: δ 0.9-1.0(3Rt); 1.8-2.0(2H,m); 2.5-2.6(2Rm); 3.5-3.6(2Rt); 4.15- 4.35(3H,m); 7.05(lRs); 7.15(lH,s); (oil), (vi) 2-(4,4-difluorobut-3-enylsulfonyl)- 1 -( 1 -methylethyl)-imidazole (Compound Vffl.15). M ÷ =264; 'H NMR: δ 1.5(6H,d); 2.55-2.65(2H,m); 3.5-3.6(2H,m); 4.15^.35(lH,m); 5.15-5.35(lH,m); 7.15(2H,br); (oil), (vii) 2-(4,4-difluorobut-3-enylsulfinyl)-4-phenylimidazole (Compound Vm.20). M f =282; 'H NMR: δ 2.35-2.65(2H,m); 3.25-3.4(2Rt); 4.15-4.3(lH,m); 7.25-7.5(4H,m); 7.6- 7.8(2H,m); (oil) using 1.5 equivalents of oxidant. (viii) 2-(4,4-difluorobut-3-enylsulfonyl)-4-phenylimidazole (Coπφound Vm.21). M^=298; 'H NMR: δ 2.45-2.6(2H,m); 3.4-3.5(2H,t); 4.1-4.28(lRm); 7.3-7.55(4H,m); 7.7- 7.75(2H,d); (m.p. 109.6-110.4°C) using 1.5 equivalents of oxidant. (be) 2-(4,4-difluorobut-3-enylsulfinyl)-l-methyl-4-phenylimidazole (Coπφound Vm.23). M^=296; 'H NMR: δ 2.5-2.65(2Rm); 3.4-3.65(2H,m); 4.0(3H,s); 4.25-4.4(1 H,m); 7.25-7.45(4H,m); 7.7-7.75(2Rdd); (m.p. 106-106.6°C) using 1.5 equivalents of oxidant. (x) 2-(4,4-difluorobut-3-enylsulfonyl)-l-memyl-4-phenylimidazole (Coπφound Vm.24). M + =312; 'H NMR: δ 2.6-2.7(2Rm); 3.58-3.65(2Rt); 4.02(3Rs); 4.2-4.35(lRm); 7.25-7.42(4Rm); 7.7-7.75(2Rdd); (mp. 78.6-79.6°C) using 1.5 equivalents of oxidant. (xi) 2-(4,4-difluorobut-3-enylsulfonyl)-4-ethyl-5-methylimidazole (Compound VHL28). M * =264; 'H NMR: δ 1.15-1.3(3H,q); 2.25(3H,two s (tautomers)); 2.45-2.7(4H,m); 3.35-3.45(2H,t); 4.1-4.3(lRm); 11.3(lRbr s); (oil), (xii) 2-(4,4-difluorobm-3-enylsulfonylH 5 5-dimemylimidazole (Coπφound Vm.30). ^=250; 'H NMR: δ 2.25(6H,two s); 2.45-2.55(2H,m); 3.35(2H,t); 4.1-4.25(lRm); 10.3-10.6(lH,br s); (mp 113.4-114.6°C). (xiii) 2-(4,4-difluorobut-3-enylsιUfonyl)-l,4,5-tιimethylimidazole (Coπφound Vm.32). M^=264; 'H NMR: δ 2.2(6Rbr s); 2.5-2.6(2Rm); 3.4-3.5(2H,t); 3.85(3H,s); 4.15- 4.3(lH,m); (oil), (xiv) l-ethyl-2-(4,4-difluorobut-3-enylsulfonyl)-4,5-α^ethylimidazole (Coπφound VHI.34). ^=278; 'H NMR: δ 1.4(3Rt); 2.15(6H,br s); 2.5-2.6(2H,m); 3.5(2H,t); 4.15- 4.3(lH,m); (oil), (xv) A mixture of 2-(4,4-difluorobut-3-enylsulfonyl)-l,5-dimethylimidazole (Coπφound Vm.36) and 2-(4,4-difluorobut-3-enylsulfonyl)-l,4-dimethylimidazole (Compound Vm.61); 'H NMR: δ 2.20(3H,s)^_2.25(3Rs); 2.5-2.6(4H,m); 3.45-3.55(4H,m); 3.85(3H,s); 3.95(3Rs); 4.15^.3(2H,m); 6.75(lH,s); 6.95(lH,s); from the mixture of Coπφounds VIH.35 and Vm.60 prepared in Example V I.5(iv) above, (xvi) An 18:82 mixture of 2-(4,4-difluorobut-3-enylsulfonyl)-5-methyl-l-(l-methylethyl)- imidazole (Coπφound Vm.38); Η NMR: δ L55(6H,d); 2.4(3H,s); 2.55-2.65(2H,m); 3.6(2H,t); 4.15-4.35(lH,m); 5.15-5.30(lH,m); 6.85(lRs); and 2-(4,4-difluorobut-3- enylsulfonyl 4-methyl-l-(l-methylethyl imidazole (Coπφound Vm.63); 'H NMR: δ 1.45(6H,d); 2.25(3H,s); 2.55-2.65(2H,m); 3.55(2H,t); 4.15-4.35(lH,m); 5.15- 5.30(lH,m); 6.90(lH,s); from the mixture of Compounds Vm.37 and Vm.62 prepared in Exanφle VIII.5(v) above, (xvii) 2-(4,4-difluorobut-3-enylsulfonyl)-5-ethoxycarbonyl- 1 -methylimidazole (Conφound Vm.53). M + =308; 'H NMR: δ 1.37-1.42(3H,t); 2.55-2.67(2Rm); 3.6-3.65(2H,t); 4.2- 4.35(lH,m); 4.25(3Rs); 4.32-4.4(2H,q); 7.7(lH,s); (oil), (xviii) 2-(4,4-difluorobut-3-enylsulfonyl)-4-methylimidazole (Compound Vm.59). ivr=236; Η NMR: δ 2.3-2.4(3Rbr); 2.45-2.55(2Rm): 3.4(2Rt); 4.2-4.4(lRm); 7.0(lRbr); (oil), (xix) 2-(4,4-difluorobut-3-enylsulfinyl)-4-ethoxycarbonyl-l-methylimidazole (Conφound Vm.66). M + =292; 'H NMR: δ 1.35-1.4(3H,t); 2.49-2.7(2Rm); 3.35-3.6(2Rm); 4.02(3H,s); 4.2-4.38(lRm); 4.35-4.42(2H,q); 7.67(lRs); (oil) using 1.5 equivalents of oxidant. (xx) 2-(4,4-difluorobut-3-enylsulfonyl)-4-ethoxycarbonyl-l-methylimidazole (Compound Vm.67). M =308; 'H NMR: δ 1.35-1.4(3H,t); 2.55-2.65(2Rm); 3.65-3.70(2H,t); 4.02(3H,s); 4.2-4.38(lRm); 4.35-4.42(2Rq); 7.65(lH,s); (oil) using 1.5 equivalents of oxidant. (xxi) 3-(4,4-difluorobut-3-enylsulfonyl)imidazo-[l,5a]-pyridine (Conφound Vtπ.152). M *" = 272; 'H NMR: δ 2.50(2Rm); 3.50(2H,t); 4.15(lRm); 6.90(lRm); 7.10(lRm); 7.20(lRs); 7.65(lH,m); 8.95(lH,dd); (oil). EXAMPLE X1 This Example illustrates a preparation of 5- (4,4-difluorobut-3-enylt o l,3-dimethyl-4-nitropyrazole (Conφound 1X82). 4,4-Difluorobut-3-enylisothiouronium hydrobromide (2.46g) was stirred at ambient temperature with aqueous sodium hydroxide (1.2g in 12cm 3 water) for 0.3 hours. 5-Chloro-l,3-dimethyl-4-nitropyrazole (1.76g) in dichloromethane (12cm 3 ) containing tetra-n-butyl ammonium bromide (0.0 lg; catalyst) was added at ambient temperature and the reaction mixture stirred for 18 hours under an atmosphere of nitrogen. The reaction was diluted with water (100cm 3 ) and the product extracted into dichloromethane (100cm 3 ). The organic phases were combined, washed with water, dried (MgS0 4 ) and evaporated under reduced pressure to give a pale yellow liquid (2.6g). A sanφle (0.9g) was fractionated using chromatography (silica; hexane : ethyl acetate 10:1 by volume) to give Compound 1X82 (0.78g). M ÷ =263; Η NMR: δ 2.25(2Rm); 2.55(3H,s); 3.08(2Rt); 3.94(3Rs); 4.20(lRm); (oil). EXAMPLE 1X2 This Example illustrates a preparation of 5- (4,4-difluorobut-3-enylsulfonyl l,3-dimethyl-4-nitropyrazole (Coπφound 1X84). 3-Chloroperbenzoic acid (1.74g of 50% by weight solid) was added to a solution of Compound 1X82 (0.526g) in dichloromethane (10cm 3 ) and the reaction was stirred at ambient temperature for 3 days. The reaction was diluted with dichloromethane (100cm 3 ), washed with aqueous sodium hydrogen carbonate and then water, dried (MgS0 4 ) and evaporated under reduced pressure to give an oily solid The crude product was fractionated using chromotography to give Coπφound 1X84 (0.15g). 'H NMR: δ 2.52(3Rm); 2.60(2Rm); 3.74(2Rt); 4.20(3Rs); 4.25(lRm); (gum). EXAMPLE TX.3 This Example illustrates a 3-step preparation of 5- (4,4-difluorobut-3-enylthio)-l,3-dimethyl-4-iodopyrazole (Conφound 1X61) Step 1; Preparation of 4-amino- - f4.4-difiuorobut-3-envlthioV 1.3-dimethylpyrazole Compound 1X82 (l.Og) was dissolved in propan-2-ol (10cm 3 ) containing water (2cm 3 ) and concentrated hydrochloric acid (catalyst, 0.1cm 3 ) and treated with reduced iron powder (l.Og). The mixture was stirred and heated under reflux for 3 hours, cooled, neutralised with solid sodium hydrogen carbonate and filtered through keiselgel. The insolubles were washed with propan-2-ol, and the filtrate evaporated under reduced pressure to give the amino pyrazole intermediate as a red-brown oil, (l.Og). M =233. Step 2; The product from Step 1 (4.6g) was dissolved in dry dichloromethane (25cm 3 ) and added to a stirred solution of boron trifluororide diethyl etherate (4.26g) in dry dichloromethane (25cm 3 ) at -15°C. Tert. butyl nitrite in dichloromethane (10cm 3 ) was added dropwise to the mixture. The reaction was allowed to warm to 5°C for 0.3 hours, diluted with hexane and the required diazonium tetrafluoroborate salt was filtered from solution as a brown solid (6.7g). Step 3: Compound 1X61 The product from Step 1 (1.33g) was added in portions to a stirred solution of potassium iodide (1.7g) in water (5cm 3 ) at 35°C. The reaction mixture evolved gas during the process and gave a red-brown oil. After 1 hour at 35°C the mixture was cooled, diluted with water, extracted with diethyl ether (100cm 3 ), the organic phase washed successively with aqueous sodium metabisulfite then water and dried (MgS0 4 ). The solvent was removed under reduced pressure and the residual oil fractionated by chromatography (silica hexane : ethyl acetate 10:1 by volume) to give Compound 1X61 as a brown oil (0.2g). ^=344. EXAMPLE 1X4 This Example illustrates a preparation of 5- (4,4-difluorobut-3-enylthio)-l,3-dimethyl-pyrazole (Compound 1X55). The diazonium salt from Exanφle 1X3. Step 2 (2.0g) was stirred in methanol (20cm 3 ) at 0°C and sodium borohydride (powder. 0.25g) was added in portions. Gas was evolved and the solution changed from colourless to orange-brown. The mixture was allowed to warm to 15°C over 0.5 hours, stored at ambient temperature for 18 hours, diluted with water, extracted with diethyl ether, dried (MgS0 4 ) and evaporated under reduced pressure to give a red-brown liquid. The liquid was fractionated using chromatography (silica; hexane : diethyl ether 1:1 by volume) to give Coπφound 1X55 (0.42g). 'H NMR: δ 2.20-2.30(5H,m); 2.74(2Rm); 3.75(3Rs); 4.23(2H,m); 6.12(lRs); (oil). EXAMPLE 1X5 This Example illustrates a preparation of ethyl 5- (4,4-difluorobut-3-enylthio)-l-methylpyrazol-4-yl carboxylate (Coπφound 1X34). Bis-(4,4-difluorobut-3-enyl)disulfide (2.90g) and tert. butyl nitrite (1.22g) in acetonitrile (40cm 3 ) were heated to 60°C under an atmosphere of nitrogen. To the stirred solution was added dropwise ethyl 5-amino-l-methylpyrazol-4-yl carboxylate (l.OOg) in acetonitrile (10cm 3 ). On complete addition the reaction solution was heated for 2 hours at 60°C, evaporated under reduced pressure and fractionated by chromatography (silica; hexane : diethyl ether, 5:1 by volume) to give Coπφound 1X34 (yield 42%). M*=276; 'H NMR: δ 1.38(3Rt); 2.20(2Rm); 3.05(2Rt); 3.97(3H,s); 4.25(lH,m); 4.34(2H,q); 7.98(lRs); (oil). The following compounds according to the invention were prepared using the above procedure and the appropriate amino-pyrazole: (i) 4-bromo-5-(4,4-difluorobut-3-enylthio)-l-methylpyrazole (Coπφound 1X31). M + =282; 'H NMR: δ 2.32(2Rm); 2.95(2H,t); 3.88(3Rs); 4.30(lRm); 7.38(lRs); (oil), (ii) 4-cyanch5-(4,4-difluorobut-3-enylthio)-l,3-dimethylpyrazole (Coπφound 1X73). 'H NMR: δ 1.38(3H,t); 2.20(2Rm); 2.38(3H,s); 3.02(2H,t); 3.97(3H,s); 4.25(lRm); (oil), (iii) ethyl 5-(4,4-difluorobut-3-enylthio)-l-phenylpyrazol-4-yl carboxylate (Compound 1X124). M =338; 'H NMR: δ 1.40(3Rt); 2.05(2H,m); 2.88(2Rt); 3.97(lH,m); 4.37(2H,q); 7.50(5H,m); 8.16(lH,s); (oil). EXAMPLE 1X6 This Example illustrates a preparation of 4-cyano-5-(4,4-difluorobut-3-enylsulfonyl)- 1,3- dimethylpyrazole (Compound 1X75). Compound 1X73 (1.32g) in dichloromethane (120cm 3 ) was treated at ambient temperature with 3-chloroperbenzoic acid (3.94g containing 50% peracid). The mixture was stirred for 18 hours, diluted with further dichloromethane and washed successively with aqueous solutions of sodium carbonate, sodium metabisulfite. Further washing with water, sodium carbonate, and water were performed before the organic phase was dried (MgS0 4 ). The solvent was evaporated under reduced pressure and the residue fractionated by chromatography (silica; hexane : diethyl ether 1:1 by volume) to give Conφound 1X75 (0.47g). M + =275; 'H NMR: δ 2.42(3H,s); 2.30(2Rm); 2.58(3H,s); 3.38(2H,t); 4.14(3Rs); 4.36(lRm); (mp 78-81°C). The following compounds according to the invention were prepared using the above procedure and the appropriate pyrazole: (i) 4-bromo 5-(4,4-difluorobut-3-enylsulfonyl)-l-methylpyrazole (Conφound 1X33). 'H NMR: δ 2.54(2Rm); 3.35(2H,t); 4.00(3H,s); 4.27(lH, ); 7.55(lH,s); (mp 42.6-43.6°C) from Compound 1X31. (ii) ethyl 5-(4,4-difluorobut-3-enylsulfonyl)-l-memylpyrazole-4-carboxylate (Coπφound 1X36). 'H NMR: δ 1.38(3H,t); 2.50(2H,m); 3.78(2H,t); 4.15-4.30(lH,m); 4.36(2Rq); 7.95(lH,s); (oil) from Coπφound 1X34. (iii) ethyl 5-(4,4-difluorobut-3-enylsulfoπyl)-l-phenylpyrazOle-4-carboxylate (Compound 1X126). 'H NMR: δ 1.42(3H,t); 2.45(2H,m); 3.72(2H,t); 4.18(lRm); 4.40(2H,q); 7.35-7.55(5H,m); 8.13(lH,s); (mp 62.5-63.0°C) from Coπφound 1X124. EXAMPLE 1X7 This Exanφle illustrates a preparation of 5- (4,4-difluorobut-3-enylthio)-l-methylpyrazole-4-carboxylic acid (Coπφound 1X40) and propan-2-yl 5-(4,4-difluorobut-3-enylthio)-l-methylpyrazole-4-carbojtylate (Conφound 1X37). Compound 1X34 (1.5g) was dissolved in propan-2-ol (40cm 3 ) and treated with 2M aqueous sodium hydroxide (8cm 3 ) and stirred at ambient teπφerature for 18 hours. The mixture was diluted with water (100cm 3 ), acidified with 2M aqueous hydrochloric acid and extracted with ethyl acetate (3x50cm 3 ). The combined organic phase was dried (MgS0 4 ) and evaporated under reduced pressure to give a yellow oil which solidified on treatment with hexane/diethyl ether. The solid was filtered from solution, washed with hexane and sucked to dryness to give Compound 1X40 (0.76g). Η NMR: δ 2.24(2H,m); 3.06(2H,t); 4.00(3H,s); 4.20(lRm); 8.08(lRs); (mp 59.4-60.0°C). The hexane/diethyl ether filtrate was evaporated under reduced pressure and the oil (containing (Conφound 1X37 with about 10% of the ethyl ester starting material from step 1) was treated with propan-2-ol (20cm 3 ) containing sodium methoxide (transesterification catalyst, lOmg) and the mixture heated under reflux for 5 hours. The reaction was cooled, diluted with water, and product extracted into diethyl ether. The organic phase was dried (MgS0 4 ) and evaporated under reduced pressure to give Compound 1X37 (O.lg). MH + =291; 'H NMR: δ 1.35(6Rd); 2.22(2Rm); 3.05(2H,t); 3.97(3H,s); 4.20(lRm); 5.20(1R septuplet); 7.95(lRs); (oil). EXAMPLE 1X8 This Example illustrates a preparation of 5- (4,4-difluorobut-3-enylsulfonyl)-l-memylpyrazole-4-carboxylic acid (Conφound 1X42). Conφound 1X36 (0.83g) was dissolved in ethanol (35cm 3 ) and treated with lithium hydroxide monohydrate (0.34g) in water (7cm 3 ) at ambient teπφerature. The reaction mixture was stirred for 18 hours, the ethanol evaporated under reduced pressure, the aqueous phase acidified with 2M hydrochloric acid, and product extracted into ethyl acetate. The organic phase was dried (MgS0 4 ) and solvent was removed under reduced pressure to give a gum which was triturated with diethyl etherhexane, giving Coπφound 1X42 (0.43g). M(NH4) + =298; 'H NMR: δ 2.52(2Rm); 3.72(2Rt); 4.10-4.30(3Rm); 8.05(lRs); (πφ 118.4-122.0°C). EXAMPLE X.1 This Example illustrates two related syntheses of mercapto- 1,2,4-oxadiazoles required as intermediates for preparation of compounds of the invention. A general method for synthesis of 5-mercaptol,2,4-oxadiazoles is by cyclisation of an amidoxime and an activated thiocarbonyl conφound such as thiophosgene or 1,1-thiocarbonyldiimidazole. Use of the first of these reagents is illustrated by the preparation of 5-mercapto-3-phenyl-l,2,4-oxadiazole. Benzonitrile (15g), hydroxylamine hydrochloride (lOg), potassium carbonate (lOg), ethanol (150cm 3 ) and water (15cm 3 ) were heated together at reflux for 6 hours and then allowed to cool overnight. The reaction mixture was filtered and the solid residue washed with ethanol. The filtrate and washings were combined and evaporated and the resultant brown residue partitioned between ethyl acetate and water. The organic phase was separated, washed with brine and dried (MgS0 4 ). Evaporation gave a brown oil which crystallised on addition of ethyl acetate and hexane to give a grey solid (10.3g). The solid (4.4g) was stirred in ether (50cm 3 ) and thiophosgene (0.55cm 3 ) was added causing a thick white precipitate to form. The reaction was heated at reflux for 1 hour and then allowed to cool. A solution of sodium hydroxide in water (50cm 3 ) was then added and the reaction heated for a further 4 hours, then allowed to cool to leave a yellow biphasic reaction mixture. The organic phase was separated and the aqueous layer was extracted twice with ether. The aqueous layer was acidified to pH 1 causing formation of a yellow ppt. The aqueous layer was extracted with ethyl acetate and the combined ethyl acetate layers were dried (MgS0 4 ) and evaporated to give 5-mercapto-3-phenyl-l,2,4-oxadiazole as an orange-brown solid (0.554g), which was used without further purification. 'H NMR δ 7.45-7.63(3Rm); 7.70-7.90(2Rm). Use of the alternative reagent, 1,1-thiocarbonyldiimidazole, is illustrated by the preparation of 5-mercapto-3-methoxymethyl-l,2,4-oxadiazole. Methoxyacetonitrile (7.1g), hydroxylamine hydrochloride (7g), potassium carbonate (13.8g), ethanol (90cm 3 ) and water (9cm 3 ) were heated together at 50°C for 9 hours and then allowed to cool. The reaction mixture was filtered and the white solid residue washed with ethyl acetate. The filtrate and washings were combined and evaporated and the resultant residue dissolved in dichloromethane. Insoluble material was removed by filtration and the filtrate evaporated to give a viscous oil (9.2g). The oil was added to toluene (60cm 3 ) and dry dimethylformamide (4cm 3 ) containing 1,1-thiocarbonyldiimidazole (5.655g) and the mixture was stirred at the ambient temperature for 2 hours. After standing for a further 60 hours the beige solid which had formed was recovered by filtration (5.2g obtained) and shown by NMR to be the uncyclised product of reaction between the hydroxy group of the amidoxime and the thiocarbonyl group. A portion of the solid (2g) was added to a suspension of sodium hydride (0.33g) in dry dimethylformamide (30cm 3 ) (frothing) and the mixture was stirred at the ambient temperature for 5 hours and left to stand for 18 hours. The reaction product was poured into water and the product extracted into ethyl acetate. The combined organic phases were separated dried (MgS0 4 ) and evaporated under reduced pressure, finally at high vacuum to remove traces of dimethylformamide. The crude 5-mercapto-3-methoxymethyl- 1,2,4-oxadiazole had Η NMR: δ 3.2(3H,s); 4.10(2H,s); 6.92-6.98(lH,br s) and was used without further purification. EXAMPLE X.2 This Example illustrates a general process for the preparation of 5-(4,4-difluorobut-3- enylthio)-3-substituted-l,2,4-oxadiazoles using the corresponding 5-mercapto intermediate prepared for example as above. This is illustrated by the following preparation of 5-(4,4- difluorobut-3-enylthio)-3-methoxymethyl-l,2,4-oxadiazole, Coπφound X26. To a solution of 5-mercaptc-3-methoxymethyl-l,2,4-oxadiazole (2.78g) in acetone (150 cm 3 ) was added 4-bromo-l,l-difluorobut-l-ene (4.87g) and potassium carbonate (3.15g) and the mixture heated under reflux for 18 hours. Gc indicated that reaction was conφlete. - I l l - Inorganic solids were removed by filtering the reaction mixture through a plug of sorbsil-C30 silica, washing with acetone. The filtrate was evaporated under reduced pressure and the yellow oily residue was chromatographed on sorbsil-C30, eluting with 5% ethyl acetate in hexane, to give Coπφound X26 (1.6g) 'H NMR: δ 2.47-2.58(2H,m); 3.28-3.35(2H,t); 3.49(3H,s); 4.18-4.36(1 H,m); 4.54(2Rs); (oil). The following compounds according to the invention were prepared using the above procedure and the appropriate intermediates indicated: (i) 5-(4,4-difluorobut-3-enylthio)-3-methoxymethyl-l,2,4-oxadiazole (Coπφound X32). 'H NMR: δ 2.37(3H,s); 2.45-2.55(2Rm); 3.22-3.30(2Rt); 4.16-4.35(lRm); (oil) from 5-mercapto-3-methy 1- 1 ,2,4-oxadiazole. (ii) 5-(4,4-difluorobut-3-enylthio)-3-phenyl-l,2,4-oxadiazole (Coπφound I). M + =268; 'H NMR: δ 2.58(2Rm); 3.35(2H,t); 4.31(lRm); 7.45-7.56(3Rm); 8.07(2Rd); (oil) from 5-mercapto-3-phenyl-l,2,4-oxadiazole. EXAMPLE X.3 This Example illustrates a preparation of 5-(4,4-difluorobut-3-enylthio)-3- methoxymethyl-l,2,4-oxadiazole (Compound X27) from Coπφound X26. Conφound X26 (0.6g) was cooled to 0°C in dichloromethane (50cm 3 ) and 3- chloroperbenzoic acid (2.19g, 2.5 equiv.) was added over a period of five minutes. The mixture was stirred at the ambient temperature for 1 hour and stood for 40 hours. The reaction mixture was poured into saturated aqueous sodium bicarbonate and the product was extracted into dichloromethane. The organic layer was washed with saturated aqueous sodium bicarbonate, water and saturated brine and dried (MgS0 4 ). Evaporation of solvent under reduced pressure gave a light brown solid which was chromatographed on silica, eluting with 10% ethyl acetate in hexane, progressing to 20% ethyl acetate in hexane, to give Coπφound X27 having 'H NMR: δ 2.6-2.71 (2H,m); 3.51(3Rs); 3.58-3.65(2H,t); 4.21- 4.37(lH,m); 4.69(2H,s); (oil). This material was found to be unstable and on standing for 60 hours at the ambient temperature had hydrolysed appreciably. EXAVfPI.E I.1A This Example illustrates a general procedures for the preparation of 5-chloro-3- substituted-l,2,4-thiadiazoles as demonstrated by the following preparation of 5-chloro-3- chloromethyl-l,2,4-thiadiazole from chloroacetamidine hydrochloride. A suspension of chloroacetamidine hydrochloride (12.9g) in dichloromethane (100cm 3 ) was cooled to -5°C and perchloromethyl mercaptan (20.44g) was added Sodium hydroxide in water (20g in 30cm 3 ) was added dropwise (exotherm). maintaining the temperature of the reaction mixture below 5°C. After the addition was complete, the reaction was allowed to warm to the ambient temperature and stirred overnight. The mixture was diluted with water and dichloromethane and the whole filtered through a pad of celite to remove insoluble material. The organic phase was separated, washed with saturated brine and dried over magnesium sulfate. The solution of product was then filtered and evaporated under reduced pressure to give a brown oil (9.72g) which was used without further purification. M 68; 'H NMR: δ 4.75(s). The following intermediate compounds were prepared according to the procedure of Example XI.1 The starting materials were known compounds, (i) 5-chloro-3-trifluoromethyl-l,2,4-thiadiazole. M 88 (bp 50°C at 12mmHg). (ii) 5-chloro-3-methylmercapto-l,2,4-thiadiazole. M 66. (iii) 5-chloro-3-methoxy-l,2,4-thiadiazole. MM 50. (iv) 5-chloro-3-(2-pyrazinyl l,2,4-thiadiazole. MM98. A related procedure was used to prepare Conφound XI.102 of the invention, as follows. Preparation of 5-chloro-3-r4.4-difluorohut-3-enylthioV1.2.4-thiadiazole A suspension of 4,4-difluorobut-3-enylisothiouronium hydrobromide (8.68g) in water (200cm 3 ) containing sodium lauryl sulfate (O.lg, catalytic) and perchloromethyl mercaptan (7.17g) was cooled to 0°C and sodium hydroxide in water (5.6g in 200cm 3 ) was added dropwise, maintaining the temperature of the reaction mixture below 5°C. After the addition was complete, the reaction was allowed to warm to the ambient teπφerature and stirred overnight. The mixture was extracted twice with ethyl actetate, the organic phase was separated, washed with saturated brine and dried (MgS0 4 ). The solution of product was then filtered and evaporated under reduced pressure to give a brown oil (8.2g) which was chromatographed on silica gel (Sorbsil C30) using 3% ethyl acetate in hexane as eluant to give Compound XI.102 (2.82g). NT=242; 'H NMR: δ 2.4-2.6(2H,m); 3.2-3.3(3H,t); 4.2- 4.4(lH,m); (oil). EXAMPLE XI.1B A general procedure for the preparation of 5-[(4-methylphenyl)-sulfonyl]-3-substitιιted- 1,2,4-thiadiazoles is illustrated by the following two-step preparation of 3-methoxymethyl-5- [(4-methylphenyl)-sulfonyl]-l,2,4-thiadiazole from methoxyacetamide. Step 1 : Preparation of 5-methoxymethvl- 3.4-oxathia7ol-2-one Chlorocarbonylsulfenyl chloride (7.35g) was added to a suspension of methoxyacetamide (5g) in toluene (30cm 3 ). The reaction mixture was stirred and heated at 90-100°C for 5 hours, then cooled The solvent was removed by evaporation under reduced pressure to give a brown gum (6.6g). M + =147; 'H NMR (DMSO-dβ): δ 3.30(3Rs); 4.30(2H,s) which was used in the next step without further purification. Step 2: Preparation of 3-methoxymethyI-5-[f4-methylphenylVsulfonyl]- 1.2.4- thiadiazole 4-Methylbenzenesulfonyl cyanide (16.26g) was added to an emulsion of 5- methoxymethyl-l,3.4-oxathiazol-2-one (6.6g) in dodecane (60cm 3 ). The reaction mixture was stirred and heated at ι50°C for 18 hours, then cooled. Water was added and the product extracted into ethyl acetate. The combined organic phases were dried (MgS0 4 ) and ethyl acetate was removed by evaporation under reduced pressure. The residue separated into a brown liquid and a clear dodecane layer which was removed and discarded Chromatography of the brown liquid on silica gel (Sorbsil C30) using 3:7 ethyl acetate : hexane as eluant give a pale orange oil which solidified on standing (6.94g). M + =284; 'H NMR: δ 2.40(3Rs); 3.45(3H,s); 4.7(2Rs); 7.4(2H,d); 8.0(2H,d); (mp 43.4-45-4°C). The following intermediate compounds were prepared according to the two-step procedure of Exanφle XI. IB. The starting materials were known coπφounds. (i) • 3-ethyl-5-[(4-methylphenyl)-sulfonyl]-l,2,4-thiadiazole. M =268; 'H NMR: δ 1.3- 1.4(3H,t); 2.45(3H,s); 2.95-3.05(2H,q); 7.4(2H,m); 8.0(2H,m) from propionamide. (ii) 3-(E-prop-l-enyl)-5-[(4-methylphenyl>sulfonyl]-l,2,4-thiadiazole. M =280; 'H NMR: δ 1.95(3Rdd); 2.45(3H,s); 6.5-6.6(lRm); 7.0-7. l(lH,m); 7.4(2H,m); 8.0(2Rm) from crotonamide. EXAMPLE XI.2 This Exanφle illustrates a process for the preparation of 5-(4,4-difluorobut-3- enylthio)-3-substituted-l,2,4-thiadiazoles using either the corresponding 5-chloro- or 5-[(4- methylphenyl)-sulfonyl]-l,2,4-thiadiazole intermediate prepared as above The general procedure is illustrated by the following preparation of 5-(4,4-difluorobut-3-enylthio)-3- methoxymethyl-l,2,4-thiadiazole (Compound XI.34). Sodium hydroxide in water (0.848g in 10cm 3 ) was added to 4,4-difluorobut-3- enylisothiouronium hydrobromide (1.75g) and the mixture stirred at ambient teπφerature for 20 minutes. A solution of 3-methoxymethyl-5-[(4-methylphenyl)-sulfonyl]-l,2,4-thiadiazole (2.0 lg) in dichloromethane (10cm 3 ) and tetrabutylammonium bromide (O.lg, catalyst) were added and the mixture was stirred for 20 minutes. Tic showed that the product had formed. The mixture was diluted with more dichloromethane (10cm 3 ) and the organic phase was separated washed with saturated brine, dried (MgS0 4 ), filtered and evaporated under reduced pressure to give an orange-yellow liquid. Chromatography of the crude product on silica gel (Sorbsil C30) using 1:4 ethyl acetate : hexane as eluant give Conφound XI.34 (1.67g). M * =252; Η NMR: δ 2.45-2.55(2Rm); 3.25-3.35(2Rt); 3.5(3H,s); 4.15-4.35(lRm); 4.65(2Rs); (oil). The following compounds according to the invention were prepared using the above procedure but with the appropriate intermediates, (i) 5-(4,4-difluorobώ-3-enylthio)-3-trifluoromethyl-l,2,4-thiadiazole (Coπφound XI.9). NT=276; 'H NMR: δ 2.5-2.6(2Rm); 3.3-3.4(2H,t); 4.2-4.4(lRm); (oil). (ii) 5-(4,4-difluorobut-3-enylthio 3-(E-prop- 1 -enyl> 1 ,2,4-thiadiazole (Compound XI.11 ). M + =248; 'H NMR: δ 1.95(3Rdd); 2.5-2.6(2Rm); 3.3(2Rt); 4.2-4.4(1 H,m); 6.45- 6.55(lH,m); 6.9-7. l(lRm); (oil), (iii) 3-ethyl-5-(4,4-difluorobut-3-enylthio l,2,4-thiadiazole (Compound XI.23). M=236; 'H NMR: δ 1.3-1.4(3Rt); 2.45-2.55(2Rm); 2.9-3.0(2Rq); 3.3(2H,t); 4.2-4.4(lH,m); (oil), (iv) 3-chloromethyl-5-(4,4-difluorobut-3-enylthio l,2,4-thiadiazole (Coπφound XI.25). M * =256; 'H NMR: δ 2.45-2.55(2H,m); 3.35(2H,t); 4.2-4.35(1 H,m); 4.7(2H,s); (oil). Two further products were produced in this reaction, which were separated during the chromatography and characterised. These were 3-(4,4-difluorobut-3-enylthiomethyl)- 5-(4,4-difluorobut-3-enylthio l,2,4-thiadiazole (Compound XI.38). M * =344; 'H NMR δ 2.25-2.35(2H,m); 2.45-2.55(2H,m); 2.65(2H,t); 3.3(2H,t); 3.9(2H,s); 4.15- 4.35(2Rm); (oil) and 5-chloro-3-(4,4-difluorobut-3-enylthiomethyl)-l,2,4-thiadiazole. M =256; 'H NMR: δ 2.2-2.3(2H,m); 2.65(2H,t); 3.9(2H,s); 4.1-4.3(lH,m); (oil) (v) 5-(4,4-difluorobut-3-enylthio>3-methoxy-l,2,4-thiadiazole (Coπφound XI.87). M * =238; 'H NMR δ 2.45-2.55(2H,m); 3.3(2H,t); 4.1(3Rs); 4.2-4.35(lH,m); (oil) (vi) 3,5-bis-(4,4-difluorobut-3-enylthio l,2,4-thiadiazole (Conφound XI.109). M + =330; 'H NMR: δ 2.45-2.6(4Rm); 3.2-3.35(4H,m); 4.2-4.4(2H,m); (oil) from Compound XI.102. (vii) 5-(4,4-difluorobut-3-enylthio 3-(2-pyrazinyl l,2,4-thiadiazole (Conφound XI.125). M + =286; Η NMR: δ 2.55-2.65(2Rm); 3.35-3.45(2H,t); 4.25-4.40(lH,m); 8.65(lH,d); 8.75(lRdd); 9.55(lRd); (oil) EXAMPLE XI.3 This Example illustrates the preparation of 3-butoxymethyl-5-(4,4-difluorobut-3- enylthio)-l,2,4-thiadiazole (Compound XI.30). Potassium carbonate (0.444g) and n-butanol (0.397g) were added to a solution of Conφound XI.25 (0.275g) in dimethylformamide (2cm 3 ) and the mixture was stirred at ambient temperature for 18 hours. Tic indicated that Coπφound XI.25 was still present in the mixture, so sodium hydride (O.lg) and n-butanol (0.4g) were added and stirring continued for a further 24 hours. Water was added and the product was extracted into diethyl ether. The organic phase was dried (MgS0 4 ), filtered and evaporated under reduced pressure to give an oil (0.442g) which was purified by chromatography on silica gel (Sorbsil C30) using 10% ethyl acetate in hexane as eluant to give Compound XI.30 (0.131g). M + =294; 'H NMR: δ 0.95-1.0(3Rt); 1.4-1.55(2Rm); 1.75-1.9(2H,m); 2.25-2.45(2H,m); 2.6-2.7(2H,t); 3.75(2H,s); 4.15-4.3(lH,m); 4.4-4.5(2H,t); (oil). The following coπφound according to the invention was prepared using the above procedure, with n-propanol in place of n-butanol. (i) 5-(4,4-difluorobut-3-enylthio)-3-propoxymethyl-l,2,4-thiadiazole (Coπφound XI.31). ^=280; 'H NMR: δ 1.0-1. l(3Rt); 1.8-1.95(2H,m); 2.25-2.35(2H,m); 2.6-2.7(2H,t); 3.75(2H,s); 4.15-4.4(lH,m); 4.4-4.45(2Rt); (oil). EXAMPLE XT.4 This Exanφle illustrates a two step process for the preparation of 5-(4,4-difluorobut-3- enylthio)-3-methyl-l,2,4-thiadiazole (Compound XI.40). Step 1; Preparation of 3-methyl-L2.4-thiadiazole-5r4HVthione To a solution of acetamidine (5g) in methanol (100cm 3 ) was added carbon disulfide (4g), sulfur (1.7g), and sodium methoxide (5.7g) and the mixture was heated under reflux for 6 hours. The mixture was cooled filtered through hi-flo filter aid to remove excess sulfur and the filtrate was partitioned between water and ethyl acetate. The ethyl acetate was evaporated to give a brown solid and on acidification of the aqueous layer a red solid was formed and filtered off. Both the solids obtained from the filtrate appeared to be a mixture of 3-methyl-l,2,4-thiadiazole-5(4H)-thione and sulfur. These two solids were combined and used in the next step. Step 2: Preparation of Compound XI.40 To a solution of 3-methyl-l,2,4-thiadiazole-5(4H)-thione (1.2g) in acetone (100 cm 3 ) was added 4.4-difluorobut-3-enyl 4-methylbenzenesulfonate (2.4g) and potassium carbonate (1.2g) and the mixture was refluxed for 4 hours after which tic indicated conφlete consumption of starting material. The reaction was poured into ethyl acetate and water and the layers separated. The aqueous layer was extracted with ethyl acetate and the combined organic layers were dried (MgS0 4 ). The solution of product was then filtered and evaporated under reduced pressure to give a brown oil which was purified by flash chromatography (silica, 7% ethyl acetate in hexane) to give 5-(4,4-difluorobut-3-enylthio)-3-methyl- 1,2,4- thiadiazole as a brown oil (0.645g). M + =222; 'H NMR: δ 2.56(2R br q); 2.63 (3Rs); 3.30(2H,t); 4.30(lH,m). The following coπφound according to the invention was prepared using the above procedure but with 3-phenyl-l,2,4-thiadiazole-5(4H)-thione as starting material, (i) 5-(4,4-difluorobut-3-enylthio>3-phenyl-l,2,4-thiadiazole (Coπφound XI.5). 'H NMR: δ 2.53(2H,q); 3.30(2H,t); 4.24(lRm); 7.38(3H,m); 8.2(2Rm). EXAMPLE XI.5 This Example illustrates the preparation of 3-(4,4-difluorobut-3-enylthio)-5-methoxy- 1,2,4-thiadiazole (Conφound XI.108). Sodium hydroxide (0.182g) was added to a solution of Conφound XI.102 (lg) in methanol (5cm 3 ) and the mixture stirred at the ambient temperature for 45 minutes, when tic indicated consumption of starting material. Water and diethyl ether were added to the mixture and the product was extracted into diethyl ether. The organic phase was dried (MgS0 4 ), filtered and evaporated under reduced pressure to give a yellow oil (0.9g). Purification by flash chromatography (silica, 5% ethyl acetate in hexane) gave Coπφound XI.108 (0.78g). M" =238; 'H NMR δ 2.4-2.5(2Rm); 3.2(2Rt); 4.15(3Rs); 4.2- 4.35(lH,m); (oil). EXAMPLE XI.6 This Example illustrates the preparation of 5-(4,4-difluorobut-3-enylthio)-3-methylthio- 1,2,4-thiadiazole (Compound XI.110). Sodium sulfide nonahydrate (0.555g) was added to 5-chloro-3-methylthio- 1,2,4- thiadiazole (1.5g) in ethanol (10cm 3 ) and the mixture stirred and heated under reflux for 18 hours. The reaction mixture was cooled and solvent removed by evaporation under reduced pressure to give a yellow solid (1.76g) which was dissolved in actetone (30cm 3 ). Potassium carbonate (2.22g) and 4-bromo-l,l-difluorobut-l-ene (1.83g) were added and the mixture stirred and heated under reflux for 18 hours. The reaction mixture was cooled, filtered through hi-flo filter aid to remove inorganic material, washing with ethyl acetate, and solvent removed by evaporation under reduced pressure to give a brown gum which was purified by chromatography on silica gel (Sorbsil C30) using 5% ethyl acetate in hexane as eluant to give Compound XI.110 (0.392g). M + =254: Η NMR: δ 2.45-2.55(2Rm); 2.65(3Rs); 3.25- 3.35(2H,t); 4.2-4.4(lRm); (oil). EXAMPLE XI.7 This Exanφle illustrates the preparation of 5-(4,4-difluorobut-3-enylthio)-3-(3- nitrophenyl)-l,2,4-thiadiazole (Compound XI.127). Hydrogen sulfide gas was bubbled for 40 minutes through a stirred mixture of potassium methoxide (2.2g) and absolute ethanol (25cm 3 ), cooled at ~ -10°C. The flask was removed from the cooling bath, 5-chloro-3-(3-nitrophenyl)-l,2,4-thiadiazole (3g) was added, and the mixture was heated under reflux for 1 hour. The reaction was cooled and poured into ether and the resulting precipitate was filtered off. The filtrate, containing 5-mercapto- 3-(3-nitrophenyl)-l,2,4-thiadiazole, was then placed in a flask and 4,4-difluorobut-3-enyl 4- methylbenzenesulfonate (1.5g) and ~ lg of potassium carbonate were added and the mixture was heated under reflux for 3 hours after which gc indicated virtually conφlete consumption of tosylate. The reaction was poured into ethyl acetate and water and the layers separated The aqueous layer was extracted with ethyl acetate and the combined organic layers were dried (MgS0 4 ). Evaporation under reduced pressure gave a brown liquid which was purified by flash chromatography (silica; eluant 5% ethyl acetate in hexane) to give Coπφound XI.127 (0.901g). M + =329; 'H NMR: δ 2.60(2H,broad q) 3.44(2H,t); 4.34(lH,m); 7.65(lH,t); 8.32(lH,dd); 8.6(lRd); 9.1(lRd) (oil). EXAMPLE XI.8 This Exanφle illustrates a method suitable for the preparation of coπφounds according to the invention in which the sulfur atom of the 4,4-difluorobut-3-enylthio substituent of the corresponding unoxidised compound (prepared according to the procedures of the preceding Examples) is oxidised to sulfoxide (sulfinyl) or sulfone (sulfonyl). Preparation of Compounds XI.35 and XI.36 from Compound XI.34. Compound XI.34 (0.85g) was stirred at ambient temperature in dichloromethane (10cm 3 ) and 3-chloro perbenzoic acid (0.814g, 1.4 equiv.) was added After three and a half hours, tic indicated consumption of starting material, with the formation of two products. The reaction was quenched by the addition of a saturated aqueous solution of sodium bicarbonate and the products were extracted into dichloromethane. The organic phase was separated, washed with saturated brine and dried over magnesium sulfate. After filtration and concentration by evaporation under reduced pressure, there was obtained a white solid (1.2g) which was purified by chromatography on silica gel using 3 : 7 ethyl acetate : hexane as eluant to give first 5-[(4,4-difluorobut-3-enyl)sulfonyl]-3-methoxymethyl-1.2,4-thiadiazole (Compound XI.36) (0.298g). M * =284; Η NMR: δ 2.55-2.65(2Rm); 3.55(3Rs); 3.5- 3.6(2Rt); 4.2-4.35(lRm); 4.80(2H,s); (oil). Futher elution gave 5-[(4,4-difluorobut-3- enyl)sulfinyl]-3-methoxymethyl-l,2,4-thiadiazole (Coπφound XI.35) (0.402g). M =268; 'H NMR δ 2.3-2.75(2Rm); 3.15-3.4(2H,m); 3.55(3Rs); 4.15-4.35(lRm); 4.75(2H,s); (oil). The following compound according to the invention was prepared by the above procedure, using two equivalents of oxidant. (i) 5-[(4,4-difluorobut-3-enyl)sulfonyl]-3-ethyl-l,2,4-thiadiazole (Coπφound XI.24) MM268; 'H NMR: δ 1.4-1.5(3Rt); 2.55-2.65(2H,m); 3.05-3.15(2H,q); 3.5-3.55(2Rt); 4.2-4.4(lRm); (oil). EXAMPLE Xπ.1 Methods for synthesis of the mercapto 1,3,4-oxadiazoles used as intermediates in preparing compounds according to the invention are well known in the art. Two representative methods are illustrated below. Method A Preparation of 2-mercapto-5-methyl-l .3.4-oxadiazole. To a solution of acetic hydrazide (5g) in ethanol (10cm 3 ) was added carbon disulfide (7.7g) followed by a solution of potassium hydroxide in ethanol (5.7g in 20cm 3 ) which caused a white precipitate to form. The reaction was then stirred at ambient temperature for 2 hours and left to stand overnight. The reaction was filtered to give a white solid (1 lg). This salt (5g) was taken up in pyridine (10cm 3 ) and the mixture heated under reflux for a total of 14 hours. After cooling, the reaction was acidified and extracted twice with diethyl ether. The ether layer was dried over magnesium sulfate, filtered and evaporated under reduced pressure to give an orange solid This was recrystallised from ethyl acetate to give 2-mercapto-5-methyl-l,3,4-oxadiazole " (0.655g). MM 16; 'H NMR: δ 2.43(3Rs); 10.9(lH,br Method B Preparation of 5-f4-methoxvbenzyiyi.3.4<)xadiazple-2f3HVthione. Step 1: Preparation of (4-methoxyphenyl)acetic acid hydrazide. Hydrazine hydrate (4.7cm 3 ) was added dropwise to ethyl (4-methoxyphenyl)acetate (3.73g) and then methanol (20cm 3 ) was added to form a homogeneous reaction mixture. This mixture was stirred for 18 hours at ambient temperature during which time a white precipitate formed. The precipitate was isolated by filtration and washed with methanol and water, then air-dried to give (4-methoxyphenyl)acetic acid hydrazide (2g). MM 80; 'H NMR: δ 3.50(2Rs); 3.80(3Rs); 3.85(2Rbr s); 6.70(lRbr s); 6.90(2Rd); 7.20(2Rd); (solid). The following intermediate compounds were made by the above methods: (i) 2-methylpropanoic acid hydrazide. MM 02; (solid), (ii) cyclopropylacetic acid hydrazide. MM 00; (solid), (iii) butanoic acid hydrazide. Η NMR: δ 0.95(3H,t); 1.60-1.75(2Rm); 2.15(2Rt); 3.90(2H,br s); 6.95(lRbr s); (solid), (iv) propanoic acid hydrazide. M + =88; (solid), (v) pentanoic acid hydrazide. 'H NMR: δ 0.90(3Rt); 1.30-1.40(2Rm); 1.60-1.70(2H,m); 2.20(2H,t); 3.90(2Rbr s); 6.80(lRbr s); (solid), (vi) hexanoic acid hydrazide. Η NMR: δ 0.90(3Rt); 1.20-1.35(4H,m); 1.60-1.70(2H,m); 2.15(2H,t); 3.90(2H,br s); 6.70(lRbr s); (solid), (vii) (4-nitroρhenyl)acetic acid hydrazide. 'H NMR: δ (DMSO- y 3.50(2H,s); 7.50(2H,d); 8.10(2Rd); (solid), (viii) (2,6-difluorophenyl)acetic acid hydrazide. MM 86; 'H NMR: δ 3.60(2H,s); 6.90- 7.00(2H,m); 7.20-7.30(lH,m); (solid), (ix) 2-methylbeπzoic acid hydrazide. M + = 150; 'H NMR: δ 2.45(3H,s); 4.10(2Rbr s); 7.00(lH,br s); 7.20-7.40(4Rm); (solid). Step 2: Preparation of 5-(4-methoxybenzyl)-l,3,4-oxadiazole-2(3H)-thione. A solution of potassium hydroxide (0.7g) in water (2cm 3 ) was added to a stirred solution of (4-methoxyphenyl)acetic acid hydrazide (1.99g) in ethanol (30cm 3 ). carbon disulfide (0.7cm 3 ) was added and the reaction was heated to reflux for 6 hours and then left to cool. The reaction mixture was evaporated to dryness under reduced pressure and the solid residue dissolved in water. The pH was adjusted to 1 with concentrated hydrochloric acid, resulting in formation of a white precipitate. The precipitate was isolated by filtration, washed with water and ether and air dried to give 5-(4-methoxybenzyl)-l,3,4-oxadiazole- 2(3H thione (1.96g). M + =222; 'H NMR: δ 3.80(3H,s); 3.95(2Rs); 6.90(2Rd); 7.20(2Rd); (solid). The following compounds were prepared by the above method, using the appropriate intermediate (either known compounds or as prepared in Step 1): (i) l,3,4-t adiazole-2(3H thione-5-carboxamide. MM45; (solid), (ii) 5-thienyl-l,3,4-thiadiazole-2(3H thione. MM84; (solid), (iii) 5-isopropyl-l,3,4-thiadiazole-2(3H)-thione. MM44; (gum), (iv) 5-cyclopropyl-l,3,4-thiadiazole-2(3R)-thione. MM42; (gum). (v) 5-propyl-l,3,4-thiadiazole-2(3H thione. MM44; (oil). (vi) 5-ethyl-l,3.4-thiadiazole-2(3H)-thione. MM 30: (oil). (vii) 5-(4-pyridyl l,3,4-thiadiazole-2(3H thione. NT= 179; 'H NMR: δ 7.75(2Rd); 8.75(2Rd); (solid), (viii) 5-butyl-l,3,4-thiadiazole-2(3H thione. 'H NMR: δ 0.95(3Rt); 1.35-1.50(2H,m); 1.65-1.75(2Rm); 2.70(2H,t); 2.90(1 Rbr s); (oil), ( e) 5-pentyl-l,3,4-thiadiazole-2(3H thione. 'H NMR: δ 0.90(3H,t); 1.25-1.45(4Rm); 1.75(2Rm); 2.70(2Rm); (oil), (x) 5-(4-nitrobenzyl>l,3,4-thiadiazole-2(3H thione. MM237; Η NMR: δ 4.20(2Rs); 7.50(2Rd); 8.25(2Rd); (solid), (xi) 5-(2,6-difluorobenzyl>l,3,4-thiadiazole-2(3H)-thione. 'H NMR: δ 4.10(2Rs); 6.90- 7.00(2Rm); 7.25-7.40(1 Rm); (solid), (xii) 5-(4-methoxyphenyl)-l,3,4-thiadiazOle-2(3R thione. 'H NMR: δ 3.80(3H,s); 7.10(2H,d); 7.75(2Rd); (solid), (xiii) 5-(2-methylphenyl l,3,4-thiadiazole-2(3H thione. 'H NMR: δ (DMSO^) 2.50(3H,s); 7.30-7.40(2H,m); 7.40-7.50(lH,m); 7.55(lH,br d); (solid), (xiv) 5^(2-methoxyphenyl)-l,3,4-thiadiazole-2(3R)-thione. (solid), (xv) 5-(4-nitrophenyl l,3,4-thiadiazole-2(3H thione. M"=223; 'H NMR: δ 8.05(2H,d); 8.30(2H,d); (solid), (xvi) 5-benzyl-l,3,4-oxadiazole-2(3H tiιione. 'H NMR: δ 4.00(2H,s); 7.25-7.40(5H,m); (solid). EXAMPLE XIT.2 This Example illustrates a preparation of 2-(4,4-difluorobut-3-enylthio)-5-phenyl- 1,3,4- oxadiazole (Coπφound XII.3). To a solution of 2-mercapto-5-phenyl-l,3,4-oxadiazole (0.499g) in acetone (15cm 3 ) was added potassium carbonate (0.387g) and 4,4-difluorobut-3-enyl 4-methyl- benzenesulfonate (0.7g) and the mixture was heated under reflux for 1.5 hours after which time all starting material had been consumed. The reaction was poured into diethyl ether and water and the layers separated. The aqueous layer was extracted with ether and the combined organic layers were washed with water and dried (MgS0 4 ). Evaporation of solvent under reduced pressure gave a pale yellow liquid which was purified by flash chromatography to give Compound XII.3 as a colourless oil that solidified on standing (0.293g). ^=268; 'H NMR: δ 2.58(2Rm); 3.32(2Rt); 4.31(lRm); 7.45-7.57(3Rm); 8.01(2H,d); (mp 38-40°C). The following compounds according to the invention were prepared from the appropriate intermediate (either known compounds or prepared as in Exaπφle XII.1) using the above method but with 4-bromo-l,l-difluorobut-l-ene as alkylating agent instead of 4,4-difluorobut-3-enyl 4-methyl-benzenesulfonate. (i) 5-cyclopropyl-2-(4,4-difluorobut-3-enylthio)-l,3,4-oxadiazole (Conφound Xπ.l). 'H NMR: δ 1.10-1.15(4Rm); 2.10-2.20(lRm); 2.45-2.55(2H,m); 3.20(2Rt); 4.30(lH,m); (oil), (ii) 2-(4,4-difluorobut-3-enylthio)-5-isopropyl-l,3,4-oxadiazole (Compound XII.8). NT=234; 'H NMR: δ 1.19(6Rd); 2.50-2.60(2H,m); 3.15(lH,septet); 3.30(2H,t); 4.30(lH,m); (oil), (iii) 5-(2,6-difluorobenzyl)-2-(4,4-difluorobut-3-enylthio)-l,3,4-oxadiazole (Coπφound Xπ.ll). 'H NMR: δ 2.45-2.55(2Rm); 3.25(2Rt); 4.20(2Rs); 4.25(lRm); 6.90- 7.00(2H,m); 7.25-7.35(lH,m); (oil), (iv) 2-(4,4-difluorobut-3-enylthio)-5-(4-nitrobenzyl l,3,4-oxadiazole (Compound XII.12). 'H NMR: δ 2.50-2.60(2H,m); 3.30(2H,t); 4.20(lH,m); 4.30(2H,s); 7.50(2H,d); 8.20(2H,d); (oil), (v) 2-(4,4-difluorobut-3-enylthio)-5-isobutyl-l,3,4-oxadiazole (Coπφound XII.23). 'H NMR: δ 1.00(6H,d); 2.10-2.20(lH,m); 2.50-2.60(2H,m); 2.70(2H,d); 3.25(2H,t); 4.30(lH,m); (oil), (vi) 2-(4,4-difluorobut-3-enylthio>5-pentyl-l,3,4-oxadiazole (Conφound XH.25). 'H NMR δ 0.90(3Rt); 1.30-1.40(4H,m); 1.70-1.80(2Rm); 2.50-2.55(2H,m); 2.80(2H,t); 3.25(2H,t); 4.30(lRm); (oil), (vii) 5-butyl-2-(4,4-difluorobut-3-enylthioVl,3,4-oxadiazole (Conφound XII.28). 'H NMR: δ 0.95(3H,t); 1.35-1.50(2H,m); 1.70-1.80(2H,m); 2.50-2.60(2H,m); 2.80(2Rt); 3.25(2Rt); 4.30(lH,m); (oil), (viii) 2-(4,4-difluorobut-3-enylthio)-5-propyl-l,3,4-oxadiazole (Conφound XII.31). 'H NMR: δ 1.00(3Rt); 1.75-1.90(2H,m); 2.50-2.60(2H,m); 2.80(2H,t); 3.25(2H,t); 4.30(lH,m); (oil), (ix) 2-(4,4-difluorobut-3-enylthio)-5-ethyl-l,3,4-oxadiazole (Coπφound Xπ.35). 'H NMR: δ 1.40(3Rt); 2.50-2.60(2H,m); 2.85(2H,t); 3.25(2Rt); 4.30(lH,m); (oil), (x) 2-(4,4-difluorobut-3-enylthio 5-methyl-1.3,4-oxadiazole (Conφound XE 49). M + =206; 'H NMR: δ 2.51(2Rm); 2.73(3H,s); 3.27(2Rt); 4.25(lH,m); (oil). (xi) 2-(4.4-difluorobut-3-enyltrύo)-13.4-oxadiazole-5-c^rboxamide (Conφound XE 55). M 235; 'H NMR: δ 2.50-2.60(2Rm); 3.35(2Rt): 4.30(lRm); (mp 113°C). (xii) 2-(4,4-difluorobut-3-enylthio)-5-(2-methylphenyl)- 1 ,3,4-oxadiazole (Conφound Xπ.128). 'H NMR: δ 2.55-2.65(2Rm); 2.70(3Rs); 3.35(2H,t); 4.30(lRm); 7.30- 7.45(3Rm); 7.90(lRd); (oil), (xiii) 2-(4,4-difluorobut-3-enylthio 5-(2-fuιyl 1.3,4-oxadiazole (Coπφound XH.131). M + =258; 'H NMR: δ 2.50-2.60(2Rm); 3.35(2H,t); 4.30(lRm); 6.60(lRm); 7.10(lRd); 7.60(lRd); (oil), (xiv) 2-(4,4-difluorobut-3-enylthio 5-(2-methoxyphenyl)-l,3,4-oxadiazole (Coπφound Xπ.132). Η NMR: δ 2.50-2.60(2Rm); 3.30(2H,t); 3.95(3H,s); 4.30(lRm); 7.10(2Rm); 7.50(lRdt); 7.90(lH,dd); (mp 35-37°C). (xv) 2-(4,4-difluorobut-3-enylthio)-5-(2-thienyl l,3,4-oxadiazole (Conφound XTI.133). MM274; 'H NMR: δ 2.50-2.60(2Rm); 3.30(2Rt); 4.30(lRm); 7.10-7.20(lRm); 7.55(lH,d); 7.70(lH,d); (oil), (xvi) 2-(4,4-difluorobut-3-enylthio 5-(3-fuιyl>l,3,4-oxadiazole (Coπφound XII.134). 'H NMR: δ 2.50-2.60(2H,m); 3.30(2H,t); 4.30(lRm); 6.90(lRm); 7.50-7.55(lH,m); S.05(lRbr s); (oil), (xvii) 2-(4,4-difluorobut-3-enylthio)-5-(4-methoxyphenyl)-l,3,4-oxadiazole (Coπφound Xπ.144). 'H NMR: δ 2.50-2.60(2H,m); 3.30(2H,t); 3.90(3H,s); 4.30(lH,m); 7.00(2Rd); 8.00(2H,d); (oil), (xviii) 2-(4,4-difluorobut-3-enylthio)-5-(4-pyridyl)-l,3,4-oxadiazole (Conφound XII.148). M =269; 'H NMR: δ 2.50-2.65(2Rm); 3.40(2H,t); 4.30(lRm); 7.90(2H,d); 8.80(2Rd); (oil). _ EXAMPLE XTT.3 This Example illustrates a preparation of 2-(4,4-difluorobut-3-enylsulfinyl)-5-phenyl- 1,3,4-oxadiazole (Compound XII.4). To a solution of Compound XII.3 (lg) in dry dichloromethane stirring at 0°C was added 3-chloroperbenzoic acid (1.3g of a 50% by weight solid, 1 equivalent). The reaction was allowed to warm to ambient temperature, stirred for 3 hours and left overnight. Tic indicated complete consumption of starting material. The reaction mixture was filtered and the filtrate partitioned between dichloromethane and sodium bicarbonate solution. The aqueous layer was extracted with dichloromethane and the combined organic phases were dried over magnesium sulfate. Evaporation of solvent under reduced pressure gave a yellow oil which was purified by flash chromatography on silica gel, eluting with 25% ethyl acetate in hexane to give Compound Xπ.4 (0.474g). M + =284; Η NMR: δ 2.67(2H,m): 3.52(2Rm); 4.32(lRm); 7.50(3Rm); 8.12(2Rd); (oil). The following compounds according to the invention were prepared from the appropriate thioether using the above method (i) 2-(4,4-difluorobut-3-enylsulfinyl)-5-(4-methoxybenzyl)-l,3,4-oxadiazole (Conφound Xπ.14). 'H NMR: δ 2.45-2.70(2Rm); 3.30-3.50(2H,m); 3.80(3H,s); 4.25(lH,m); 4.25(2H,s); 6.90(2Rd); 7.25(2Rd); (oil), (ii) 2-(4,4-difluorobut-3-enylsulfιnyl>5-pentyl-l,3,4-oxadiazole (Coπφound XII.26). 'H NMR: δ 0.95(3H,t); 1.30-1.40(4Rm); 1.80-1.90(2H,m); 2.50-2.75(2Rm); 2.95(2Rt); 3.35-3.55(2H,m); 4.30(lRm); (oil), (iii) 5-butyl-2-(4,4-difluorobut-3-enylsulfinyl>l,3,4-oxadiazole (Coπφound Xπ.29). 'H NMR: δ 1.00(3Rt); 1.40-1.50(2H,m); 1.80-1.90(2H,m); 2.50-2.75(2H,m); 3.00(2H,t); 3.35-3.55(2H,m); 4.30(lRm); (oil), (iv) 2-(4,4-difluorobut-3-enylsulfιnyl>5-propyl-l,3,4-oxadiazole (Conφound XII.32). 'H NMR: δ 1.05(3H,t); 1.80-1.95(2H,m); 2.50-2.75(2H,m); 2.95(2H,t); 3.35-3.55(2Rm); 4.30(lH,m); (oil), (v) 2-(4,4-difluorobut-3-enylsulfinyl>5-(2-methylphenyl)-l,3,4-oxadiazole (Coπφound Xπ.129). Η NMR: δ 2.55-2.80(2H,m); 2.70(3H,s); 3.40-3.60(2H,m); 4.30(lH,m); 7.30-7.40(lH,m); 7.45-7.50(lH,m); 8.00(lH,d); (oil), (vi) 2-(4,4-difluorobut-3-enylsulfihyl)-5-(4-nitrophenyl l,3,4-oxadiazole (Compound Xπ.142). Η NMR δ 2.55-2.80(2H,m); 3.45-3.70(2H,m); 4.35(lRm); 8.35(2H,d); 8.45(2H,d); (oil), (vii) 2-(4,4-difluorobut-3-enylsulfinyl)-5-(4-methoxyphenyl)-l,3,4-oxadiazole (Coπφound Xπ.145). Η NMR δ 2.50-2.80(2Rm); 3.40-3.60(2H,m); 3.90(3H,s); 4.30(lH,m); 7.05(2H,d); 8.05(2H,d); (oil). The following compounds according to the invention were prepared from the appropriate thioether using the general method described above but with 2 equivalents of 3- chloroperbenzoic acid as oxidant. (viii) 2-(4,4-difluorobut-3-enylsulfonyl)-5-phenyl-l,3,4-oxadiazole (Coπφound XII.5). M + =300; 'H NMR: δ 2.71(2Rm); 3.67(2Rm); 4.33(lRm); 7.52-7.70(3Rm); 8.25(2H,d); (mp 104-106°C). (ix) 2-(4,4-difluorobut-3-enylsulfonyl 5-isopropyl-l,3,4-oxadiazole (Compound XII.9). Η NMR δ 1.50(6Rd): 2.60-2.70(2Rm); 3.20-3.40(lRm); 3.60(2Rt); 4.30(lRm); (gum), (x) 2-(4,4-difluorobut-3-enylsulfonyl>5-(4-nitrobenzyl)-L3,4-oxadiazole (Compound Xπ.13). 'H NMR: δ 2.60-2.70(2H,m); 3.60(2H,t); 4.30(lRm); 4.40(2H,s); 7.55(2Rd); 8.25(2Rd); (oil), (xi) 2-(4,4-difluorobut-3-enylsulfonyl)-5-(4-methoxybenzyl)-l,3,4-oxadiazole (Coπφound Xπ.15). 'H NMR: δ 2.60-2.70(2Rm); 3.65(2Rt); 3.80(3Rs); 4.20(lRm); 4.25(2H,s); 6.90(2H,d); 7.25(2Rd); (mp 60-63°C). (xii) 5-benzyl-2(4,4-difuorobut-3-enylsulfonyl)-l,3,4-oxadiazole (Coπφound XH.19). 'H NMR δ 2.60(2Rm); 3.60(2Rt); 4.25(lRm); 4.30(2H,s); 7.25-7.40(5H,m); (oil), (xiii) 2-(4,4-difluorobut-3-enylsulfonyl)-5-pentyl-l,3,4-oxadiazole (Conφound XEI.27). 'H NMR: δ 0.95(3H,t); 1.30-1.45(4Rm); 1.80-1.90(2Rm); 2.60-2.70(2Rm); 3.00(2H,t); 3.60(2H,t); 4.30(lRm); (oil), (xiv) 5-butyl-2-(4,4-difluorobut-3-enylsulfonyl)-l,3,4-oxadiazole (Conφound XH.30). 'H NMR: δ 1.00(3Rt); 1.40-1.50(2Rm); 1.80-1.90(2Rm); 2.60-2.70(2H,m); 3.00(2H,t); 3.60(2Rt); 4.30(lRm); (oil), (xv) 2-(4,4-difluorobut-3-enylsulfonyl]-5-propyl-l,3,4-oxadiazole (Coπφound XII.33). 'H NMR: δ 1.10(3H,t); 1.85-2.00(2H,m); 2.60-2.70(2H,m); 2.95(2H,t); 3.60(2H,t); 4.30(lH,m); (oil), (xvi) 2-(4,4-difluorobut-3-enylsulfonyl)-5-methyl-l,3,4-oxadiazole (Conφound XII.51). 'H NMR: δ 2.20-2.30(2H,m); 2.30(3H,s); 3.60(2Rt); 4.30(lH,m); (oil), (xvii) 2-(4,4-difluorobut-3-enylsulfonyl)-5-(2-methylphenyl)- 1 ,3,4-oxadiazole (Coπφound XE 130). 'H NMR: δ 2.70-2.80(2H,m); 2.75(3H,s); 3.70(2H,t); 4.30(lH,m); 7.40(lH,d); 7.50(lH,d); 8.00(lH,d); (mp 90-93°C). (xviii) 2-(4,4-difluorobut-3-enylsulfonyl)-5-(4-nitrophenyl)-l,3,4-oxadiazole (Coπφound Xπ.143). M + =345; Η NMR: δ 2.70-2.80(2H,m); 3.70(2Rt); 4.35(lH,m); 8.35(2H,d); 8.45(2Rd); (oil), (xix) 2-(4,4-difluorobut-3-enylsulfonyl)-5-(4-methoxyphenyl)- 1 ,3,4-oxadiazole (Coπφound XU.146). Η NMR: δ 2.70-2.80(2Rm); 3.65(2H,t); 3.90(3H,s); 4.30(lRm); 7.05(2H,d); 8.10(2Rd); (mp 60°C). EXAMPLE XIII.l This Example illustrates a general procedure for the preparation of 2-(4,4-difluorobut- 3-enylthio)-5-substituted-l,3,4-thiadiazoles from the corresponding thiadiazole-2(3H)-thione, conφounds which are well known in the art. The process is illustrated by the preparation of 2-(4,4-difluorobut-3-enylthio)-5-memylammo-1.3,4-tr-iadiazole (Coπφound XQI.70) from the corresponding thione and 4,4-difluorobut-3-enyl 4-methyl-benzenesulfonate. Other alkylating agents, for example 4-bromo-l.l-difluorobut-l-ene may also be used Preparation of Compound XIIL70. To a solution of 5-methylamino-1.3.4-thiadiazole-2(3H)-thione (0.393g) in acetone (10cm 3 ) was added potassium carbonate (0.369g) and 4,4-difluorobut-3-enyl 4-methyl- benzenesulfonate (0.7g) and the mixture was heated under reflux for 3 hours after which gc analysis indicated complete consumption of starting material. The reaction mixture was filtered through hi-flo filter aid and the pad washed thoroughly with diethyl ether. The filtrate was poured into ether and water and the layers were separated The aqueous layer was extracted twice with ether and the combined organic phases were dried (MgS0 4 ). Evaporation of solvent under reduced pressure gave a brown oil which was purified by flash chromatography on silica gel, eluting with 1:1 ethyl acetate : hexane to give Conφound Xm.70 (0.273g) M ÷ =237; 'H NMR: δ 2.43(2H,m); 3.04(3H,s); 3.15(2H,t); 4.29(lH,m); 5.36(lH,br s); (mp 52.5-53.5°C). The following compounds according to the invention were prepared by the above general method using the appropriate mercapto thiadiazoles and in some cases 4-bromo-l,l- difluorobut-1-ene as alkylating agent, (i) 5-cyclopropyl-2-(4,4-difluorobut-3-enylthio)-l,3,4-thiadiazole (Conφound Xm.6). M + =248; 'H NMR: δ 1.10-1.30(4H,m); 2.30-2.40(lH,m); 2.45-2.55(2H,m); 3.30(2H,t); 4.30(lH,m); (oil), (ii) 2-(4,4-difluorobut-3-enylthio>5-phenyl-l,3,4-thiadiazole (Conφound XHI.9). M"=284; Η NMR: δ 2.50-2.65(2Rm); 3.40(2H,t); 4.50(lH,m); 7.40-7.50(3H,m); 7.85- 7.95(2Rm); (mp 39°C). (iii) 2-(4,4-difluorobut-3-enylthio)-5-isopropyl-l,3,4-thiadiazole (Coπφound XHI.16). NT=250; 'H NMR: δ 1.40(3Rs); 1.45(3Rs); 2.45-2.60(2H,m); 3.35(2H,t); 3.35- 3.50(lH,m); 4.30 (IRm); (oil), (iv) 5-benzyl-2-(4,4-difluorobut-3-enylthio)-l,3,4-thiadiazole (Coπφound Xm.20). MM298; 'H NMR: δ 2.45-2.55(2Rm); 3.30(2H,t); 4.30(lH,m); 4.40(2H,s); 7.25- 7.40(5Rm); (oil), (v) 2-(4,4-difluorobut-3-enylthio>5-methyl-l,3,4-thiadiazole (Conφound Xm.40). M"=222; 'H NMR: δ 2.50(2Rm); 2.73(3H,s); 3.35(2Rt); 4.29(lH,m); (oil). (vi) 2-(4.4-difiuorobut-3-enyluΗθ)-1.3.4-thiadiazole-5-carboxamide (Coπφound XHI.45). M + =151; 'H NMR: δ 2.50-2.60(2Rm): 3.45(2Rt); 4.30(lRm); 6.80(lRbr s); 7.15(lRbr s); (mp 168°C). (vii) 2-(4,4-difluorobut-3-enylthio)-L3.4-thiadiazole (Compound Xffl.63). M =208; 'H NMR: δ 2.54(2Rm); 3.43(2H,t); 4.30(lRm); 9.03(lRs); (oil), (viii) 5-aπιino-2-(4,4-difluorobut-3-enylthio)-L3,4-thiadiazole (Conφound Xm.69). M + =223; 'H NMR δ 2.45(2Rm); 3.20(2H,t); 4.30(lRm); 5.20(2Rbr s); (mp 138°C). (ix) 2-(4,4-difluorobut-3-enylthio)-5-(3-trifluoromethylbenzylthio)- 1 ,3,4-thiadiazole (Coπφound Xm.l 10). M + =304; 'H NMR: δ 2.51 (2Rm); 3.31 (2H,t); 4.27(1 Rm); 4.56(2H,s); 7.42-7.70(4Rm); (oil), (x) 5-cycloρropylmethylthio-2-(4,4-difluorobut-3-enylthio)- 1 ,3,4-thiadiazole (Compound Xm.l 14). M + =294; 'H NMR: δ 0.35(2Rm); 0.65(2H,m); 1.25(lRm); 2.50(2H,m); 3.25(2H,d); 3.30(2Rt); 4.25(lRm); (oil), (xi) 2,5-bis-(4,4-difluorobut-3-enylthio l,3,4-tMadiazole (Conφound Xm.l 17). M + =330; 'H NMR δ 2.51(4H,m); 3.32(4H,t); 4.29(2H,m); (oil), (xii) 2-(4,4-difluorobut-3-enylthio 5-methylthio- 1 ,3,4-thiadiazole (Conφound Xffi.119). JvT=254; 'H NMR δ 2.51(2H,m); 2.77(3Rs); 3.31(2Rt); 4.20(lRm); (oil), (xiii) 2-<4,4-difluorobut-3-enyltWo)-5-(sulfonamidophenyl)-l,3,4-thiadiazole (Coπφound Xm.143). MT=363; 'H NMR: δ 2.55-2.65(2H,m); 3.50(2H,t); 4.30(lH,m); 4.95(2H,br s); 8.05(4H,m); (mp 154°C). EXAVIPLE Xm.2 This Example illustrates a general procedure for the preparation of 2-(4,4-difluorobut- 3-enylthio)-5-substituted-l,3,4-thiadiazoles from 2-amino-5-substituted thiadiazoles. The process is illustrated by the preparation of 2-(4,4-difluorobut-3-enylthio)-5-ethyl-l,3,4- thiadiazole (Compound Xm.27) from 2-amino-5-ethyl-l,3,4-thiadiazole. Preparation of Compound XIIL27. A solution of 2-amino-5-ethyl-l,3,4-thiadiazole (0.786g) and di-4,4-difluorobut-3-enyl disulfide (1.5g) in dichloromethane (25cm 3 ) was stirred and cooled in an ice-water bath. Tert. butyl nitrite (1.2g) was added the cold bath removed and the reaction heated under reflux for 1.3 hours. The mixture was then poured into diethyl ether/water and the layers separated. The aqueous layer was extracted with ether and the combined organic phases were dried (MgS0 4 ), filtered and evaporated under reduced pressure to give a brown oil. Purification by column chromatography on silica gel using 1:9 and 2:8 ethyl acetate : hexane as eluant gave Compound XQI.27 (0.959g). MM.36: Η NMR: δ 1.40(3H,t); 2.45- 2.60(2Rm); 3.10(2Rq); 3.35(2Rt); 4.30(lRm); (oil). The following compounds according to the invention were prepared by the above procedure, using the appropriate intermediates: (i) 5-bromo-2-(4,4-difluorobut-3-enylthio)-l,3.4-thiadiazole (Conφound Xm.l). ^=286; Η NMR: δ 2.45-2.60(2Rm); 3.40(2H,t); 4.30(lRm); (oil), (ii) 2-(4,4-difluorobut-3-enylthio>5-tert.-butyl-l,3,4-thiadiazDle (Conφound Xm.3). M + =264; 'H NMR: δ 1.48(9H,s); 2.45-2.60(2H,m); 3.35(2H,t); 4.30(lH,m); (oil), (iii) 2-(4,4-difluorobut-3-enylthio)-5-trifluoromethyl- 1 ,3,4-thiadiazole (Compound Xm.14). MM276; 'H NMR: δ 2.50-2.60(2Rm); 3.45(2Rt); 4.30(lRm); (oil). EXAMPLE XTTI.3 This Example illustrates a preparation of 2,5-bis-(4,4-difluorobut-3-enylsulfinyl)- 1,3,4-thiadiazole (Compound XIII.133) using 3-chloroperbenzoic acid as the oxidant. A solution of Conφound Xm.117 (0.49g) in dichloromethane (30cm 3 ) was cooled in a methanol ice bath to ~ -10°C, 3-chloroperbenzoic acid (lg of a 50% by weight solid, 2 equivalents) was added and the reaction was allowed to stir and gradually warm to the ambient temperature, then stirred for 7 hours and left to stand for 18 hours. The mixture was then poured into sodium bicarbonate solution and the product extracted into diethyl ether. The combined organic phases were washed with sodium bicarbonate solution and dried (MgS0 4 ). Evaporation of solvent under reduced pressure gave a pale yellow liquid which was purified by flash chromatography on silica gel, eluting with 30% ethyl acetate in hexane to give Conφound Xm.133 (0.168g). 'H NMR: δ 2.58(4H,m); 3.36(4H,m); 4.26(2H,m). (mp 46-48°C). The following conφounds according to the invention were prepared by the above general procedure, using the appropriate number of equivalents of 3-chloroperbenzoic acid as oxidant. (i) 2-(4,4-difluorobut-3-enylsulfinyl)-5-phenyl-l,3,4-thiadiazole (Coπφound Xm.10). M + =300; 'H NMR δ 2.40-2.80(2Rm); 3.30-3.40(2Rm); 4.30(lRm); 7.45- 7.60(3Rm); 7.95-8.00(2Rm); (mp 67°C). (ii) 2-(4,4-difluorobut-3-enylsulfonyl)-5-phenyl- 1 ,3,4-thiadiazole (Coπφound XHI.11 ). M =316; 'H NMR: δ 2.60-2.75(2H,m); 3.65(2Rt); 4.30(lRm); 7.45-7.65(3Rm); 7.95-8.05(2Rm); (mp 80°C). (iii) 2-(4,4-difluorobut-3-enylsulfinyl)-5-methyl-l,3,4-thiadiazole (Conφound XHI.41). M 238; 'H NMR: δ 2.35-2.55(lRm): 2.55-2.75(1 Rm); 2.90(3Rs); 3.20-3.40(2Rm); 4.30(lRm); (oil), (iv) 2-(4,4-difluorobut-3-enylsulfonyl)-5-methyl-1.3,4-thiadiazole (Conφound Xm.42). M + =255; 'H NMR: δ 2.55-2.70(2Rm); 2.95(3Rs); 3.60(2H,t); 4.30(lRm); (oil), (v) 2-(4,4-difluorobut-3-enylsulfinyl>L3,4-thiadiazole (Conφound XHI.64). M 225; 'H NMR δ 2.35-2.50(lRm); 2.60-2.75(lRm); 3.25-3.45(2Rm); 4.30(lRm); 9.35(lH,s); (oil), (vi) 2-(4,4-difluorobut-3-enylsulfonyl)-l,3,4-thiadiazole (Coπφound XHI.65). MH + =241; 'H NMR δ 2.60-2.70(2Rm); 3.70(2Rt); 4.30(lH,m); 9.40(lH,s); (oil), (vii) 2,5-bis-(4,4-difluorobut-3-enylsulfonyl l,3,4-thiadiazole (Coπφound Xffl.124). M + =394; 'H NMR: δ 2.69(4Rm); 3.70(4Rt); 4.30(2Rm); (mp 88-91°C). (viii) 2-(4,4-difluorobut-3-enylsulfonyl)-5-(4,4-difluorobut-3-enylsulfinyl)- 1 ,3,4-thiadiazole (Compound XHI.134). MM78; 'H NMR: δ 2.38-2.55(1 Rm); 2.60-2.79(3H,m); 3.38(2Rm); 3.62-3.74(2H,m); 4.19-4.39(2Rm); (mp 45^7°C). The following compounds according to the invention were prepared by the above general procedure but using the appropriate number of equivalents of magnesium monoperoxyphthalate as oxidant. ( ) 5-bromo-2-(4,4-difluorobut-3-enylsulfonyl)-l,3,4-thiadiazole (Coπφound Xm.2). MH + =319; 'H NMR δ 2.60-2.70(2Rm); 3.65(2H,t); 4.30(lRm); (oil), (x) 2-(4,4-difluorobut-3-enylsulfonyl)-5-tert.-butyl-l,3,4-thiadiazole (Conφound XHI.4). MH + =297; 'H NMR: δ 1.55(9H,s); 2.60-2.70(2H,m); 3.65(2H,t); 4.30(lH,m); (mp 37°C). (xi) 5-cyclopropyl-2-(4,4-difluorobut-3-enylsulfonyl)-l,3,4-thiadiazole (Coπφound Xm.7). MR=281; 'H NMR: δ 1.25-1.45(4Rm); 2.40-2.55(lH,m); 2.55-2.65(2H,m); 3.60(2H,t); 4.30(lH,m); (gum), (xii) 2-(4,4-difluorobut-3-enylsulfonyl)-5-trifluoromethyl- 1 ,3,4-thiadiazole (Coπφound XHI.15). M-S0 2 H + =243; Η NMR: δ 2.60-2.75(2H,m); 3.75(2H,t); 4.20-4.40(lRm); (gum)- (xiii) 2-(4,4-difluorobut-3-enylsulfonyl)-5-isopropyl-l,3,4-thiadiazole (Compound XHI.17). M^=283; 'H NMR δ 1.50(3Rs); 1.55(3H,s); 2.60-2.70(2H,m); 3.50-3.70(3H,m); 4.30(lH,m); (mp 43°C). (xiv) 2-(4,4-difluorobut-3-enylsulfinyl>5-ethyl-l,3,4-thiadiazole (Coπφound Xm.28). 'H NMR: δ 1.50(3Rt); 2.40-2.50(lRm); 2.60-2.70(lH,m); 3.20(2H,q); 3.25-3.35(2H,m); 4.25(lRm); (gum), (xv) 2-(4,4-difluorobut-3-enylsulfonyl)-5-ethyl-1.3..4-thiadiazole (Coπφound Xm.29). M " =269; 'H NMR δ 1.50(3Rt); 2.60-2.70(2Rm); 3.20(2Rq); 3.65(2H,t); 4.30(lRm); (gum). EXAMPLE Xm.4 This Exanφle illustrates a preparation of 2-(4,4-difluorobut-3-enylthio)-5-methoxy- 1,3,4-thiadiazole (Compound XHI.lOl) from Compound Xm.l. To a stirred suspension of sodium hydride (0.030g) in toluene (3cm 3 ) was added methanol (0.022g), resulting in effervescence. After stirring for 10 minutes, Conφound Xm.l (0.20g) was added and the reaction was stirred at the ambient temperature for 18 hours. The reaction was analysed by gc and further portions of sodium hydride and methanol added until complete loss of starting material was observed The reaction was poured into water and the layers separated. The product was extracted into diethyl ether and the combined organic phases were dried (MgS0 4 ) filtered and evaporated under reduced pressure to give a pale yellow oil. Purification by column chromatography on silica gel using 3:17 ether : hexane as the eluant gave Compound Xm.101 (0.069g). M + =238; 'H NMR: δ 2.40- 2.55(2Rm); 3.25(2H,t); 4.20(3H,s); 4.30(lH,m); (oil). EXAMPLE XTV.l This Example illustrates the preparation of 5-(4,4-difluorobut-3-enylthio)-l- methyltetrazole (Compound XTV.l). The sodium salt of 5-mercapto-l-methyltetrazole was alkylated with 4-bromo-l,l- difluorobut-1-ene using the procedure of Exaπφle XHL1 to give Compound XTV.l. M*=206; 'H NMR: δ 2.53(2H,m); 3.38(2H,t); 3.92(3H,s); 4.28(lRm); (oil). EXAMPLE XV.1 This example illustrates a preparation of l-(4,4-difluorobut-3-enylthio)-4-nitrobenzene (Conφound XV.1). 4-Nitro-thiophenol (0.5g), potassium carbonate (0.448g), 4,4-difluorobut-3-enyl 4- methyl-benzenesulfonate (0.846g) and potassium iodide (0.388g) were heated and stirred under reflux in acetone (15cm 3 ) for a total of 6 hours after which none of the starting tosylate was detectable by tic. The reaction mixture was poured into water and extracted with 3 portions of ethyl acetate. The combined organic phases were washed 3 times with 2M NaOR and saturated aqueous brine and then dried (MgS0 4 ). Removal of solvent by evaporation under reduced pressure gave a dark yellow oil which was purified by flash chromatography on silica gel using 5% ethyl acetate in hexane as eluant to give Compound XV.1 (0.474g). MM245; 'H NMR: δ 2.42(2Rm)o3.09(2Rt); 4.30(lRm); 7.35(2H,d); 8.14(2Rd); (oil). EXAMPLE XVI.1 This Exanφle illustrates a preparation of 2-chloro-4-(4,4-difluorobut-3-enylthio)- pyridine (Compound XVI.1). Tert-butyl nitrite (0.442g) in dichloromethane (20cm 3 ) was added dropwise to a solution of 4-amino-2-chloropyridine and bis-(4,4-difluorobut-3-enyl)disulfide (1.9g) in dichloromethane (20cm 3 ) while stirring the mixture at 0°C. The reaction mixture was stirred for 4 hours and then allowed to stand at the ambient temperature for 18 hours. Water was added and the product extracted into ethyl acetate. The combined organic phases were washed with saturated brine, dried (MgS0 4 ), filtered and evaporated under reduced pressure to give an orange-brown gum. Chromatography on sorbsil-C30 using 4% ethyl acetate in hexane as eluant gave Compound XVI.1 (0.134g). M + =235; 'H NMR: δ 2.35-2.46(2Rm); 2.98-3.7(2H,t); 4.18(lH,m); 7.02(lH,d); 7.11(lH,d); 8.14-8.21(lH,d); (oil). EXAMPLE XVI.2 This Exanφle illustrates a 2-step preparation of 4-(4,4-difluorobut-3-enylthio)-2,3,5,6- tetrafluoropyridine (Compound XVI.2). Step 1; Preparation of the sodium salt of 2.3.5.6-tetrafluoropyridine-4-thiol 4-Chloro-2,3,5,6-tetrafluoropyridine (2g) and sodium hydrosulfide dihydrate were stirred and heated under reflux in iso-propanol (40cm 3 ) for 3 hours. The mixture was then stirred at the ambient temperature for 18 hours. The precipitated solid was removed by filtration, washed with diethyl ether and discarded. The combined organic solutions were evaporated under reduced pressure to give 2,3,5,6-tetrafluoropyridine-4-thiol as its sodium salt (2.2 lg), which was used without further purification in the second step. Step 2: Preparation of fCompound XVI.2 The intermediate from step 2 (1.7g), 4-bromo-l,l,-difluorobut-l-ene (1.99g), and potassium carbonate (1.53g), were stirred and heated under reflux in acetone (30cm 3 ) for 18 hours. The inorganic precipitate was removed by filtration and the filtrate evaporated under reduced pressure to give a dark brown oil. Chromatography on sorbsil-C30 using hexane as eluant gave Compound XVI.2 (1.82g). JVT=273; 'H NMR: δ 2.3-2.42(2Rm); 3.15- 3.25(2H,t); 4.15-4.34(lRm); (oil). The following compounds according to the invention were prepared using the procedure of Step 2 above. The alkylating agent was 4-bromo-l,l,-difluorobut-l-ene or 4,4- difluorobut-3-enyl 4-methyl-benzenesulfonate. (i) 4-(4,4-difluorobut-3-enylthio)-pyridine (Compound XVI.5). M + =201; 'H NMR: δ 2.40(2Rm); 3.04(2Rt); 4.30(lRm); 7.11(2H,d); 8.41(2H,d); (oil) from 4- mercaptopyridine. (ii) 4,4-difluorobut-3-enyl 2-(4,4-difluorobut-3-enylthio)pyridine-3-carboxylate (Conφound XVI.10). MM35; Η NMR: δ 2.43(4Rm); 3.22(2Rt); 4.29(2H,m); 4.36(2H,t); 7.09(lH,dd); 8.20(lRdd); 8.57(lH,dd); (oil) from 2-mercaptopyridine-3-carboxylic acid. Potassium iodide was used to convert two equivalents of 4,4-difluorobut-3-enyl 4-methyl-benzenesulfonate to the more reactive 4-iodo-l,l-difluorobut-l-ene in situ in this reaction, (iii) 2-(4,4-difluorobut-3-enylthio)-5-trifluoromethylpyridine (Conφound XVI.11). 'H NMR: δ 2.40(2Rm); 3.25(2H,t); 4.25(lH,m); 7.25(lH,dd); 7.45(lH,dd); 8.40(lH,d); (oil) from 2-mercapto-5-trifluoromethylpyridine. (iv) 2-(4,4-difluorobut-3-enylthio)pyridine (Compound XVI.19). M + =201; 'H NMR: δ 2.40(2Rm); 3.20(2H,t); 4.30(lH,m); 6.90(lH,dd); 7.20(lH,dd); 7.45(lH,td); 8.40(lH,dd); (oil), (v) 2-(4,4-difluorobut-3-enylthio)-5-nitropyridine (Compound XVI.21). M + =246; Η NMR: δ 2.45(2Rm); 3.30(2Rt); 4.28(lRm); 7.30(lRd); 8.23(lH,dd); 9.25(lRd); (oil) from 2-mercapto-5-nitropyridine. EXAMPLE XVI.3 This Example gives a general procedure for the preparation of 2-(4,4-difluorobut-3- enylthio)-5-substituted-pyridines from 2-chloro-5-substituted-pyridines. The method is illustrated by the preparation of 5-chloro-2-(4,4-difluorobut-3-enylthio)pyridine (Coπφound XVI.13) from 2,5-dichloropyridine. Sodium hydrosulfide dihydrate (0.672g) was added to a solution of 2,5- dichloropyridine (1.48g) in dimethylformamide (20cm3), causing the mixture to go blue and then green on heating to 100°C. The reaction was heated for 7 hours and then 4-bromo-l,l- difluorobut-1-ene ( 1.71 g) and potassium carbonate (1.38g) were added The reaction was heated for 2 hours then allowed to cool. The reaction mixture was poured into diethyl ether and 2M HC1 and the layers separated. The aqueous layer was extracted with ether. The combined organic phases were then washed with 2M HC1, water and brine (alternately 3 times each), dried (MgS0 4 ), filtered and evaporated under reduced pressure to give a brown oil. Column chromatography on silica gel using 2% diethyl ether in hexane as eluant gave Conφound XVI.13 (0.805g). M ^ =235: Η NMR: δ 2.40(2Rm); 3.20(2Rt); 4.25(lRm); 7.15(lRdd); 7.45(lRdd); 8.40(lRd); (oil). The following compound according to the invention was prepared using the above procedure: (i) 5-cyano-2-(4,4-difluorobut-3-enylthio)pyridine (Compound XVI.15). Η NMR: δ 2.40(2H,m); 3.25(2Rt); 4.25(lRm); 7.25(lH,dd); 7.70(lH,dd); 8.65(lRd); (mp 34°C). EXAMPLE XVT.4 This Exaπφle gives a general procedure for the preparation of 2-(4,4-difluorobut-3- enylthio)-3-substituted-pyridines from 2-chloro-3-substituted-pyridines and 4,4-difluorobut-3- enylisothiouronium hydrobromide. The method is illustrated by the preparation of 2-(4,4- difluorobut-3-enylthio)-3-nitropyridine (Compound XVI.24) from 2-chloro-3-nitropyridine. 4,4-Difluorobut-3-enylisothiouronium hydrobromide (1.24g) was added to a solution of sodium hydroxide (0.6g) in water (10cm 3 ) and the reaction was stirred vigorously at the ambient temperature for 20 minutes. A solution of 2-chloro-3-nitropyridine (0.795g) in dichloromethane (10cm 3 ) was added to the reaction followed by tetra-n-butylammonium bromide (catalytic). The reaction was stirred vigorously for 3 hours. The mixture was diluted with dichloromethane and the layers separated. The organic layer was washed with brine, dried (MgS0 4 ), filtered, and evaporated under reduced pressure to give a yellow oil. Column chromatography on silica gel using 15% diethyl ether in hexane as eluant gave Coπφound XVI.24 (0.847g). M + =246; 'H NMR δ 2.40(2H,m); 3.25(2Rt); 4.30(lH,m); 7.20(lH,dd); 8.50(lH,dd); 8.70(lH,dd); (oil). The following compound according to the invention was prepared using the above procedure: (i) 3-cyano-2-(4,4-difluorobut-3-enylthio)pyridine (Compound XVI.8). M + =226; 'H NMR: δ 2.40(2Rm); 3.30(2Rt); 4.25(lRm); 7.10(lRdd); 7.80(lRdd); 8.55(lRdd); (oil). EXAMPLE XVT.5 This Example illustrates a method suitable for the preparation of conφounds according to the invention in which the sulfur atom of the 4,4-difluorobut-3-enylthio substituent of the corresponding unoxidised compound (prepared according to the procedures of the preceding Examples) is oxidised to sulfoxide (sulfinyl) or sulfone (sulfonyl). - l j-5 - Preparation of Compound XVI.3 from Compound XVT.2 using one equivalent of ffiri an Coπφound XVI.2 (0.818g) was cooled to 0°C in dichloromethane (30cm 3 ) and 3- chloroperbenzoic acid (0.99g) was added over a period of five minutes. The mixture was stirred at the ambient temperature for 6 hour and stood for 40 hours. The reaction mixture was poured into saturated aqueous sodium bicarbonate and the product was extracted into dichloromethane. The organic layer was washed with water and dried (MgS0 4 ). Evaporation of solvent under reduced pressure gave a yellow oil which was chromatographed on sorbsil- C30, eluting with 15% ethyl acetate in hexane to give 4-(4,4-difluorobut-3-enylsulfinyl)- 2,3,5,6-tetrafluoropyridine (0.71 lg). Η NMR: δ 2.45-2.8(2Rm); 3.15-3.3(lRm); 3.5- 3.65(lH,m); 4.2-4.4(1 Rm); (oil). Preparation of 5-cvano-2-f4.4-difluorobut-3-enylsulfony1 pyridine f Compound XVT.16 from Compound XVI.15 using two equivalents of oxidant. 3-Chloroperbenzoic acid (3.14g of a 50% solid) was added portionwise to a stirred solution of Coπφound XVI.15 (1.03g) in dichloromethane (30cm 3 ) at 0°C. The reaction was then allowed to warm to the ambient temperature and stirred for 4 hours. The mixture was poured into 2M aqueous sodium hydroxide and the layers separated The aqueous layer was extracted with dichloromethane and the combined organic layers were dried over magnesium sulfate, filtered and evaporated under reduced pressure to give a yellow oil which crystallised on standing. Column chromatography on silica gel using 3 : 7 ethyl acetate : hexane as eluant gave Compound XVI.16 (0.785g). 'H NMR: δ 2.40(2Rm); 3.25(2H,t); 4.25(lRm); 7.25(lH,dd); 7.70(lRdd); 8.65(lRd); (mp 34°C) The following compounds according to the invention were prepared using the above procedure: (i) 4-(4,4-difluorobut-3-enylsulfonyl)pyridine (Compound XVI.6). 'H NMR: δ 2.50(2H,m); 3.20(2Rt); 4.25(lH,m); 7.80(2H,d); 8.95(2H,d); (oil), (ii) 2-(4,4-difluorobut-3-enylsulfonyl)-5-trifluoromethylpyridine (Coπφound XVI.12). 'H NMR: δ 2.50(2H,m); 3.50(2H,t); 4.25(lH,m); 8.25(2H,d); 9.00(lRbr s); ( p 60°C). (iii) 2-(4,4-difluorobut-3-enylsulfonyl)pyridine (Compound XVI.20). 'H NMR δ 2.50(2Rm); 3.50(2Rt); 4.25(lRm); 7.55-7.50(lRm); 8.00(lH,dt); 8.10(lRd); 8.75(lH,d); (oil). EXAMPLE XVTT.1 This Example illustrates a 2-step preparation of 3-(4,4-difluorobut-3-enylthio)-6- methylpyridazine (Compound XVII.1). Step 1 : Preparation of 3-mercapto-6-methylp τidazine 3-Chloro-6-methylpyridazine (5g) and thiourea (2.96g) were stirred together and heated under reflux in ethanol (50cm 3 ) for 7.5 hours. The reaction was cooled and allowed to stand for 18 hours. The solid precipitate which had formed was filtered off and washed with diethyl ether to give 3-mercapto-6-methylpyridazine (2.3g), which was used in the next step without further purification. 'H NMR: δ 2.40(3Rs); 7.30(lRd); 7.63(lH,d); 14.5- 14.7(lRbr s). Step 2; Preparation of Compound XVTI.l A mixture of the product from Step 1 (0.337g), 4,4-difluorobut-3-enyl 4- methylbenzenesulfonate (0.70g), potassium iodide (0.444g) and potassium carbonate (0.369g) were stirred together and heated under reflux in acetone (20cm 3 ) for 11 hours. Inorganic solids were removed by filtration and the filtrate evaporated under reduced pressure to give a brown oil. Chromatography on silica gel using 1 :4 ethyl acetate: hexane as eluant gave Coπφound XVHU (0.15g). M + =216; 'H NMR: δ 2.48(2Rm); 2.62(3Rs); 3.36(2H,t); 4.20- 4.40(lRm); 7.10(lH,d); 7.21(lRd); (oil). The following compounds according to the invention and the corresponding intermediate compounds were prepared using the procedure of Steps 1 and 2 above, (i) 3-(4,4-difluorobut-3-enylthio>6-chloropyridazine (Coπφound XVII.2). M"=236; 'H NMR: δ 2.50(2Rm); 3.39(2H,t); 4.20-4.40(lRm); 7.27(2Rs); (oil) from 3,6- dichloropyridazine. (ii) 3-(4,4-difluorobut-3-enylthio 6-methoxypyridazine (Conφound X .3). M + =232; Η NMR: δ 2.47(2Rm); 3.31(2H,t); 4.09(3H,s); 4.20-4.40(lH,m); 6.83(lH,d); 7.20(lH,d); (solid mp 39.3-40.1°C) from 3-chloro-6-methoxypyridazine. (iii) 3-(4,4-difluorobut-3-enylthio 6-phenylpyridazine (Compound XVII.4). M + =278; 'H NMR: δ 2.54(2Rm); 3.46(2H,t); 4.25-4.42(1 H,m); 7.39(lH,d); 7.51(3H,m); 7.69(lH,d); 8.05(2Rm); (solid mp 91.7-92.1°C) from 3-chloro-6-phenylpyridazine. (iv) l-(4,4-difluorobut-3-enylthio>phthalazine (Compound XVΩ..7). M"=252; 'H NMR (CDC1 3 ): δ 2.59(2Rm); 3.55(2Rt); 4.28-4.45(1 H,m); 7.89(3H,m); 8.12(lH,m); 9.25(1 Rs); (oil) from l(2H)-phthalazinthione using the procedure of Step 2 above. EXAMPLE XVπ.2 This Example illustrates a preparation of Compounds XVII.5 and XVII.6 from Compound XVTI.4. Compound XVII .4 (0.5g) was stirred at ambient temperature in iso-propanol (20cm 3 ) and magnesium monoperoxyphthalic acid hexahydrate (0.89g in 10cm 3 water) was added The mixture was stirred at the ambient temperature for 20 hours. The solid which had precipitated was filtered off and washed with water. The filtrate was poured into a saturated aqueous solution of sodium bicarbonate and further product was extracted into ethyl acetate. The combined organic layers were washed with saturated brine and dried (MgS0 4 ). Evaporation of solvent under reduced pressure gave an off-white solid which was combined with the material first precipitated and chromatographed on silica gel, eluting with 30% ethyl acetate in hexane. The first product recovered was 3-(4,4-difluorobut-3-enylsufonyl)-6- phenylpyridazine (Compound XVII.6) (0.2g). M + =310; Η NMR: δ 2.60(2H,m); 3.75(2H,t); 4.20-4.40(lRm); 7.60(3Rm); 8.11(lRd); 8.15(2Rm); 8.22(lH,d); (solid mp 141.7-144.3°C). Further elution gave 3-(4,4-difluorobut-3-enylsufιnyl)-6-phenylpyridazine (Compound XVH.5) (0.25g). M + =294; 'H NMR: δ 2.40 and 2.65(2Rm); 3.20-3.40(2Rm); 4.18-4.32(lRm); 7.59(3Rm); 8.11(lRd); 8.15(2H,m); 8.21(lRd); (mp 133-134°C). EXAMPLE XVm.1 This Exanφle illustrates a 3-step preparation of 2-(4,4-difluorobut-3-enylthio)- quinoxaline (Conφound XVm.l). Step 1 : Preparation of quinoxalin-2-thione 2-Quinoxalinol (lOg), phosphorous pentasulfide (16.72g) and pyridine (200cm 3 ) were stirred together and heated under reflux for 7 hours. The reaction mixture was allowed to cool and most of the pyridine was removed by evaporation under reduced pressure. The residue was partitioned between ethyl acetate and water and the organic layer was separated The aqueous layer was extracted with three further portions of ethyl acetate and the combined organic phases were washed with saturated aqueous brine, dried (MgS0 4 ) and evaporated under reduced pressure to give a brown oily solid which was triturated with hot ethyl acetate : hexane (1:1) to dissolve the product and leave an insoluble residue. The solvent was removed under reduced pressure and gave an orange solid, part of which was used without further purification in Step 2. Step 2: Preparation of 2-r4-bromo-4.4-difluorobutylthioVquinoxaline A mixture of the product from Step 1 (lg), 4-bromo-4,4-difluorobutyl methanesulfonate (1.65g) and potassium carbonate (0.852g) were stirred together in acetone (30cm 3 ) at ambient temperature for 7 hours. Inorganic solids were removed by filtration and the filtrate evaporated under reduced pressure to give a brown oil. Chromatography on silica gel using 1 :4 ethyl acetate: hexane as eluant gave 2-(4-bromo-4,4-difluorobutylthio)- quinoxaline (1.375g). MM32: Η NMR: δ 2.19(2Rm); 2.50-2.70(2Rm); 3.43(2Rt); 7.60- 7.73(2Rm); 7.93(lRdd): 8.03(lRdd); 8.60(lRs); (oil). Step 3: Preparation of Compond XVTII.I 1,8-Diazabicyclo[5.4.0] undec-7-ene (DBU) (1.14cm 3 ) and the product from step 2 (1.275g) were stirred in toluene (30cm 3 ) and heated under reflux for 5 hours. The mixture was cooled, then excess ethyl acetate and 2M aqueous hydrochloric acid were added and the organic phase separated. The aqueous phase was extracted with ethyl acetate and the combined organic phases were washed with saturated brine, dried (MgS0 4 ), filtered and evaporated under reduced pressure to give a brown oil. Chromatography on silica gel using 1:4 ethyl acetate : hexane as eluant gave Compound XVIII.1 (0.65g). Ivf=252; Η NMR: δ 2.51(2Rm); 3.39(2H,t); 4.30-4.40(lH,m); 7.60-7.75(2Rm); 7.90(lRdd); 8.03(lH,dd); 8.60(lRs); (oil). The following compound according to the invention and the corresponding intermediate compound were prepared using the procedure of Steps 2 and 3 above: (i) 6-chloro-2-(4,4-difluorobut-3-enylthio quinoxaline (Coπφound XVm.4). M"=286; 'H NMR: δ 2.50(2H,m); 3.35(2Rt); 4.20-4.40(1 Rm); 7.65(lH,dd); 7.86(lRd); 8.01(lH,d); 8.59(1 Rs); (oil), from 6-chloroquinoxalin-2-thione via 2-(4-bromo-4,4- difluorobutylthio>6-chloroquinoxaline. 'H NMR: δ 2.08-2.2 l(2Rm); 2.48- 2.68(2H,m); 3.40(2Rt); 7.65(lRdd); 7.88(lRd); 8.00(lH,d); 8.60(lH,s); (oil). EXAMPLE XVm.2 This Example illustrates a 2-step preparation of 2-(4,4-difluorobut-3-enylthio)-pyrazine (Compound XVm.7). Step 1 : Preparation of 2-mercaptopyrazine 2-Chloropyrazine (5g) and thiourea (3.32g) were heated under reflux in ethanol (50cm 3 ) for 8 hours. The reaction mixture was cooled and the ethanol was removed by evaporation under reduced pressure to give a brown gum (8.3 lg) which was stirred with 2M aqueous sodium hydroxide (50cm 3 ) for 16 hours. The solid which precipitated was filtered off and washed with water and acetone and vacuum dried. This gave a yellow solid (0.72g); 'H NMR (DMSO-dg): δ 7.69(lH,d); 7.89(lRd); 8.6(lRs), which was used in the second step without further purification. Step 2: Preparation of Compound XVIII .7 The product from Step 1 (0.213 g), 4,4-difluorobut-3-enyl 4-methyl-benzenesulfonate (0.5g), potassium carbonate (0.263 g) and potassium iodide (0.317g) were mixed in acetone (10cm 3 ) and heated under reflux for 9 hours then allowed to cool over a weekend The precipitate formed was removed by filtration and the filtrate evaporated under reduced pressure to give a brown oil. Chromatography on silica gel using 1:4 ethyl acetate : hexane as eluant gave Coπφound XVTII.7 (0.3g). M + =202; Η NMR: δ 2.40(2Rm); 3.21(2Rt); 4.20-4.40(lRm); 8.20(lRd); 8.38(lH,t); 8.48(lRs); (oil). EXAMPLE XVm,3 This Example illustrates a 2-step preparation of 3-chloro-2-(4,4-difluorobut-3- enylthio)-pyrazine (Compound XVIII.10). Step 1: Preparation of 2-chloro-3-mercaptopyrazine and 2.3-dimercaptnpvt-aτine 2,3-Dichloropyrazine (lg) and sodium hydrosulfide dihydrate (2.5g) were combined in isopropanol (20cm 3 ) and the mixture heated under reflux for 1 hour. The reaction was cooled and allowed to stand for 36 hours. The yellow solid which precipitated was recovered by filtration, washed with diethyl ether and dried under vacuum. The filtrate was discarded The solid was dissolved in hot ethanol and on cooling a small amount of sodium hydrosulfide precipitated and was removed by filtration. The remaining ethanol solution was diluted with diethyl ether wherupon a yellow solid (0.3g) precipitated This was identified as the bis- sodium salt of 2,3-dimercaptopyrazine, MH + (FAB 88; 'H NMR (DMSO-c .): δ 7.35(lRd); 7.50(lRd). Evaporation of the mother liquors gave a yellow solid (0.8g), identified as the sodium salt of 2-chloro-3-mercaptopyrazine, M(FAB)=145; 'H NMR (DMSO-d,-,): δ 7.35(lRd); 7.80(lRd) Step 2: Preparation of 3-chloro-2-( ' 4 r 4-difluorobut-3-enylthioVpyra7ine; The mono-thiolate product from Step 1 (0.8g), 4,4-difluorobut-3-enyl 4-methyl- benzenesulfonate (1.24g) and potassium carbonate (0.655g) were mixed in acetone (25cm 3 ) containing dimethyl formamide (5cm 3 ) and heated under reflux for 15 hours then allowed to cool. The precipitate was removed by filtration and the filtrate evaporated under reduced pressure to give a brown oil. Chromatography on silica gel using a 95:5 mixture of hexane : ethyl acetate as eluant gave Compound XVTII.10 (0.45g). M + =236; 'H NMR: δ 2.41(2H,m); 3.20(2H,t); 4.20-4.40(lRm); 8.05(lRd); 8.30(lRd) (oil). This contained (gc) 5% of Coπφound XVIII.13 as an impurity. Compound XVIII.13 was obtained pure in its own right by treatment of the bis- thiolated product from Step 1 of the above example with two equivalents of 4,4-difluorobut- 3-enyl 4-methyl-benzenesulfonate under the same conditions as Step 2 of this Exaπφle. Chromatography on silica gel using a 4:1 mixture of hexane : ethyl acetate as eluant gave 2.3-bis-(4,4-difluorobut-3-enylthio)-p>τazine. MM24; Η NMR: δ 2.40(4Rm); 3.22(4Rt); 4.20-4.40(2Rm); 8.07(2Rs) (oil). The following compound according to the invention was prepared using the above procedure: (i) 6-chlorc>2-(4,4-difluorobut-3-enylthio)-pyra2 ne (Coπφoιmd XVm.l4). M"=236; 'H NMR: δ 2.42(2Rm); 3.21(2Rt); 4.20-4.40(lRm); 8.20(lRs); 8.35(lRs) (oil) from 2,6-dichloropyrazine. EXAMPLE XVTTI.4 This Example illustrates a preparation of Compounds XVm.2 and XVm.3 from Coπφound XVm.l. Conφound XVm.l (0.25g) was stirred at ambient temperature in ethanol (10cm 3 ) and magnesium monoperoxyphthalic acid hexahydrate (0.589g in 5cm 3 water) was added over a period of five minutes. After 30 minutes, the mixture was heated to 70°C for 1 hour. The reaction mixture was cooled, poured into saturated aqueous sodium bicarbonate and the products were extracted into ethyl acetate. The organic layer was washed with water and dried (MgS0 4 ). Evaporation of solvent under reduced pressure gave an off-white solid (0.15g) which was chromatographed on silica gel, eluting with 10% ethyl acetate in hexane. The main product recovered was 2-(4,4-difluorobut-3-enylsulfonyl)-quinoxaline (Compound XVm.3) (O.lg) mp 86.5-87.5°C. M =284; Η NMR: δ 2.61(2Rm); 3.62(2H,t); 4.20- 4.40(lRm); 8.00(2H,m); 8.25(2Rm); 9.51(lRs). Tic indicated the presence of a lower rf material, 2-(4,4-difluorobut-3-enylsulfinyl)-quinoxaline (Compound XVm.2) in the crude reaction product but this was not isolated pure. The following compounds according to the invention were prepared by the above procedure: (i) 6-chloro-2-(4,4-difluorobut-3-enylsulfιnyl)-pyrazine (Compound XVHI.15). M " =253; 'H NMR: δ 2.30-2.70(2Rm); 3.00-3.30(2Rm); 4.19-4.35(lRm); 8.70(lH,s); 9.10(lRs) (oil) from Compound XVIII.14. (ii) 6-chloro-2-(4,4-difluorobut-3-enylsulfonyl)-pyrazine (Compound XVHI.16). M + =268; 'H NMR: δ 2.55(2Rm); 3.50(2Rt); 4.20-4.35(lRm); 8.90(lRs); 9.19(lRs) (oil) from Compound XVIII.14. EXAMPLE VIII.l This Example illustrates a 3-step preparation of 4-(4,4-difluorobut-3-enylthio]- 1,2,3- benzotriazine (Compound XI 1). Step 1 : Preparation of 4-mercapto-l r 2. -hen7.otria?ine 2-Aminobenzonitrile (5g) was stirred in pyridine (30cm 3 ), triethylamine (6cm 3 ) was added and hydrogen sulfide gas was bubbled into the reaction over 4 hours. The mixture was then poured into water (20cm 3 ) and the oil which separated out on shaking was separated off, and dried by azeotroping with ethanol and toluene. This gave a yellow solid (2- aminothiobenzamide, 3g) which was stirred in 2M hydrochloric acid (30cm 3 ) at 0°C. Sodium nitrite (1.65g) in water (10cm 3 ) was added dropwise and the reaction mixture was stirred cold for 1 hour, then allowed to warm to the ambient temperature and stirred for a further 1 hour. The solid which was produced was filtered off, washed with water and dried by washing with diethyl ether, to give a brown solid (2.15g). Step 2; Preparation of 4-f4.4-difluorobut-3-envlthioV1.2.3-ben7 triazine The product of Step 1 (lg), 4-bromo-4,4-difluorobutyl methanesulfonate (1.65g) and potassium carbonate (0.852g) were stirred together in acetone (30cm 3 ) at ambient teπφerature for 36 hours. Inorganic solids were removed by filtration and the filtrate evaporated under reduced pressure to give a brown oil. Chromatography on silica gel using 1:4 ethyl acetate: hexane as eluant gave two yellow oils (ea 0.5g). The first-eluted oil was identified as N- alkylated material and the second was the desired S-alkyated intermediate 4-(4-bromo-4,4- difluorobutylthio l,2,3-benzotriazine. 'H NMR: δ 2.18-2.3 l(2H,m); 2.58-2.71 (2Rm); 3.63(2Rt); 7.95(lRt); 8.09(2Rm); 8.40(lRd). Step 3: Preparation of Compound XI 1 1,8-Diazabicyclo[5.4.0] undec-7-ene (DBU) (0.45cm 3 ) and the product from step 2 (0.5g) were stirred in toluene (15cm 3 ) and heated under reflux for 6 hours. The mixture was cooled, then excess ethyl acetate and 2M aqueous hydrochloric acid were added and the organic phase separated. The aqueous phase was extracted with ethyl acetate and the combined organic phases were washed with saturated brine, dried over anhydrous magnesium sulfate, filtered and evaporated under reduced pressure to give a yellow oil. Chromatography on silica gel using 1:4 ethyl acetate : hexane as eluant gave Compound XIX1 (0.25g). MH + =254; Η NMR: δ 2.60(2Rm); 3.60(2Rt); 4.30-4.40(1 H,m); 7.93(lRt); 8.09(2Rm); 8.39(lRd); (oil). EXAMPLE XX.1 Two methods (A and B) of preparing mercapto- 1,2,4-triazines required as intermediates for preparation of compounds of the invention are described below. METHQ A A general synthesis of 3-mercapto-1.2.4-triazines is by reaction between thiosemicarbazide and a 1.2 di-carbonyl compound. This is illustrated by the preparation of 3-mercapto-5-methy 1- 1.2.4-triazine. A solution of sodium bicarbonate (8g) in water (100cm 3 ) was added to a suspension of thiosemicarbazide (8g) in water (100cm 3 ). The resulting solution was cooled below 5°C and pyruvic aldehyde (40% weight solution in water, (20cm 3 )) was added The solution was kept at 5°C for 18 hours, then washed with chloroform (10 x 50cm 3 ). The pH of the aqueous layer was adjusted to 2 with concentrated hydrochloric acid. The resulting precipitate was filtered off, washed with copious amounts of water and dried, giving an orange solid (4.036g). The 3-mercapto-5-methyl-l,2,4-triazine was used without further purification in subsequent steps. The following intermediate mercaptotriazines were prepared following the above procedure. In some cases, ethanol was used as solvent in place of water. The starting materials were commercially available, (i) 3-mercapto-l,2,4-triazine from glyoxal. (ii) 3-mercapto-5-propyl-6-methyl-l,2,4-triazine from hexane-2,3-dione. 'H NMR δ 0.98(3H,t); 1.54-1.68(2Rm); 2.08(3Rs); 3.04(2Rt); 8.2(lH,br s). (iii) 3-mercaptCh5-phenyl-6-methyl-l,2,4-triazine from l-phenylpropane-l,2-dione. METHOD B An alternative method for preparing mercapto- 1,2,4-triazines comprises treatment of a corresponding hydroxytriazine (which may exist in various tautomeric forms) with a thiolating reagent such as phosphorous pentasulfide. This following illustrates the preparation " of l,2,4-triazine-3,5(2H,4H)-dithione from l,2,4-triazine-3,5(2H,4H dione (6-azauracil). 6-Azauracil (2g), phosphorous pentasulfide (15.72g) and pyridine 50cm 3 were stirred together and heated under reflux for 56 hours. The reaction mixture was allowed to cool and most of the pyridine was removed by evaporation under reduced pressure. The residue was agitated with diethyl ether and water and the organic layer was separated The aqueous layer was extracted with three further portions of diethyl ether and the combined organic phases were washed with saturated aqueous brine, dried (MgS0 4 ) and evaporated under reduced pressure to give a brown oil which was chromatographed on silica gel. using 1:5 ethyl acetate: hexane as eluant. This gave an orange solid (lg) which was used without further purification. 'H NMR (DMSσd^): δ 7.95(lRs); 13.8-14. l(lRbr s); 14.3-14.6(lH,br s) 3-Mercapto-l,2.4-berizotriazine was prepared from 3-hydroxy-l,2,4-benzotriazine and 6-methyl-l,2,3-triazine-5(4H)-thione from 6-methyl-l,2,3-triazine-5(4H)-one following essentially the above procedure. EXAMPLE XX.2 This Example illustrates the preparation of compounds according to the invention which contain a 1,2,4-triazine substituted with a 4,4-difluorobut-3-enylthio group in the 3, 5 or 6-position, starting from a correspondingly substituted mercaptotriazine and an appropriate difluorobut-1-ene alkylating agent. This is demonstrated by the following preparation of 3- (4,4-difluorobut-3-enylthio)-5-hydroxy-l,2,4-triazine (Compound XX227) from 6-aza-2- thiouracil and 4,4-difluorobut-3-enyl 4-methyl-benzenesulfonate. 4,4-Difluorobut-3-enyl 4-methyl-benzenesulfonate (1.5g) and potassium iodide (0.95g) were stirred in ethanol (5cm 3 ) and heated under reflux for three hours then allowed to cool. This part of the procedure converts the starting material to the more chemically reactive and thio-selective alkylating agent, 4-iodo-l,l-difluorobut-l-ene. 6-Aza-2-thiouracil (0.744g) was added as a solution in 1M aqueous sodium hydroxide (5.73cm 3 ) and the reaction mixture stirred at ambient temperature for 70 hours. The reaction was worked up by addition of an excess of 1M aqueous sodium hydroxide and ethyl acetate. The ethyl acetate layer was separated and the aqueous layer was washed with more ethyl acetate. These extracts were discarded The aqueous layer was then acidified to pH4 with 2M aqueous hydrochloric acid The product was extracted into ethyl acetate (3 portions) and these combined organic layers were washed with water and saturated aqueous brine and dried (MgS0 4 ). The product was recovered from the solution by evaporation under reduced pressure to give a cream solid (0.659g). A portion was redissolved in hot ethyl acetate and some insoluble material removed by filtration. Compound XX227 recovered from solution by evaporation had mp 102-103°C. M + =219; 'H NMR (DMSO-d^): δ 2.41(2Rm); 3.25(2H,t); 4.55-4.75(lH,m); 7.69 and 7.79(total IRea s, tautomeric protons) Coπφound XX247 was prepared using a related procedure, as follows. 6-Methyl-l,2,3-triazine-5(4H)-thione (0.5g), 4-bromo-l,l-difluorobut-l-ene (0.673g) and potassium carbonate (0.543g) were stirred together in acetone (5cm 3 ) for 60 hours at the ambient temperature. Then inorganic material was filtered off and washed with acetone. Solvent was removed from the combined acetone solutions by evaporation under reduced pressure and the residual brown gum was chromatographed on silica, eluting with 20% ethyl acetate in hexane, to give 5-(4,4-difluorobut-3-enylthio 6-methyl-l,2,4-triazine (Coπφound XX247) (0.075g). M 217; Η NMR: δ 2.45(2Rm); 2.60(3Rs); 3.29(2Rt); 4.20- 4.40(lRm); 9.11(lRs); (oil). EXAMPLE XX3 When the mercaptotriazine is fully soluble in acetone and carries no other potentially interfering nucleophilic groups a procedure alternative to that of Exanφle XX2 may be used. This is illustrated by the following preparation of 3,5-bis-(4,4-difluorobut-3-enylthio)- 1,2,4-triazine (Compound XX231) from l,2,4-triazine-3,5(2R4H>dithione and 4,4-difluoro- 3-butenyl 4-methyl-benzenesulfonate. l,2,4-Triazine-3,5(2R4H)-dithione (lg), 4,4-difluorobut-3-enyl 4-methyl- benzenesulfonate (3.6g), potassium iodide (1.14g) and potassium carbonate (0.952g) were stirred and heated under reflux in acetone (20cm 3 ) for 7 hours. The solution was cooled and filtered to remove solids. The filtrate and further acetone washings of the solids were combined and evaporated under reduced pressure to give a brown oil. Chromatography on silica gel using 15:85 ethyl acetate : hexane as eluant gave Coπφound XX231 (lg) as an orange oil. M + =325; 'H NMR: δ 2.40-2.55(4Rm); 3.25(4Rm); 4.15- .40(2H,m); 8.70(lRs). EXAMPLE XX4 This Exanφle illustrates a general procedure for the two-step preparation of conφounds according to the invention by reaction of a mercapto-substituted 1,2,4-triazine with 4-bromo-4,4-difluorobutyl methanesulfonate followed by dehydrobromination of the resulting intermediate as demonstrated by the following preparation of 3-(4,4-difluorobut-3- enylthio)-5-phenyl-6-methyl-l,2,4-triazine (Compound XX4). Step 1; 3-f4-bromo-4.4-difluorobutvlthioV5-phenyl-6-methyl- 2.4-triazine. A mixture of 4-bromo-4,4-difluorobutyl methanesulfonate (0.7g), 3-mercapto-5- phenyl-6-methyl-l,2,4-triazine (0.5g) and potassium carbonate (0.7g) were stirred together and heated under reflux in acetone (40cm 3 ) for 14 hours. Inorganic solids were removed by filtration and the filtrate evaporated under reduced pressure to give a brown oil (1.058g). Chromatography on silica gel using 1 :4 ethyl acetate: hexane as eluant gave an orange oil (0.576g). This was stirred and heated under reflux in trifluoroacetic acid (3cm 3 ) for 6 hours to re-cyclise some material which had undergone partial hydrolysis and ring opening. Product was recovered by evaporation of the solvent under reduced pressure and chromatography on silica gel and gave 3-(4-bromo-4,4-difluorobutylthio)-5-phenyl-6-methyl- 1,2,4-triazine. (0.509g). Η NMR: δ 2.12-2.24(2Rm); 2.48-2.68(2Rm); 2.78(3H,s); 3.36(2H,t); 7.50-7.58(3Rm); 7.68-7.74(2Rm): (oil). Step 2; 3-f4.4-difluorobut-3-enylthioV5-phenyl-6-methyl-1.2.4-triazine 1,8-Diazabicyclo[5.4.0] undec-7-ene (DBU) (1cm 3 ) was added dropwise to a stirred solution of the product from step 1 (0.5g) in toluene (10cm 3 ). The mixture was kept at ambient temperature for 20 hours, then excess ethyl acetate and saturated aqueous ammonium chloride were added and the organic phase separated. The aqueous phase was extracted with ethyl acetate and the combined organic phases were washed with saturated aqueous ammonium chloride, dried (MgS0 4 ), filtered and evaporated under reduced pressure to give an orange oil (0.43 g). Chromatography on silica gel using 1:4 ethyl acetate : hexane as eluant gave Compound XX4 (0.28 lg). M + =293; Η NMR: δ 2.48-2.58(2Rm); 2.76 (3Rs); 3.32(2Rt); 4.22-4.40(lRm); 7.48-7.58(3Rm); 7.68-7.76(2Rm); (oil). EXAMPLE XX.5 This Example illustrates a procedure suitable for the preparation of conφounds according to the invention carrying an alkoxy, or substituted alkoxy, group on the 5-position of the triazine ring from a compound carrying alkenylthio groups in both the 3 and 5- positions, as demonstrated by the preparation of 3-(4,4-difluorobut-3-enylthio)-5-methoxy- 1,2,4-triazine (Coπφound XX221) from Compound XX231. Conφound XX231 (0.5g) was stirred for one hour with sodium methoxide (0.083g) in methanol (15cm 3 ) at ambient temperature. The solvent was removed by evaporation under reduced pressure and the residue was chromatographed on silica gel, eluting with 15:85 ethyl acetate : hexane, and gave 0.12g of Compound XX221. ^=233; 'H NMR: δ 2.50(2H,m); 3.29(2H,t); 4.02(3H,s); 4.22-4.42(1 H,m); 8.55(lRs) as a single isomer whose identity as the 5-methoxy compound was confirmed by nmr. The following compounds according to the invention were prepared using the above procedure with the appropriate alkoxide in the corresponding alcohol as solvent: (i) 3-(4,4-difluorobut-3-enylthio 5-( 1 -methyl-ethoxy> 1 ,2,4-triazine (Conφound XX205). lVf=261; 'H NMR: δ 1.4(6Rd); 2.5(2H,m); 3.25(2H,t); 4.2-4.4(lH,m); 5.4(lRm); 8.45(lH,s). (ii) 3-(4,4-difluorobut-3-enylthio)-5-ethoxy-l,2,4-triazine (Coπφound XX218). MM247; 'H NMR: δ 1.43(3Rt); 2.50(2H,m); 3.26(2Rt); 4.2-4.4(1 H,m); 4.46(2Rq); 8.5(lH,s) EXAMPLE XX6 This Example illustrates a 2-step procedure used for the preparation of Coπφounds XX52 and XX116 as a 1:1 mixture. Step 1 : 3-r4-bromo-4.4-difluorobutvlthioV5-methyl-1.2.4-triazine and 344- bromo-4.4-difluorobutylthioV6-methyl-L2 r 4-triazine 4-bromo-4.4-difluorobutyl methanesulfonate (lg) and thiosemicarbazide (0.475g) were stirred together and heated under reflux in ethanol (20cm 3 ) for 5 hours. GC indicated conφlete consumption of the methanesulfonate. The mixture was allowed to cool and water (3cm 3 ) and sodium bicarbonate (lg) were added (effervescence). A 40% by weight solution of pyruvic aldehyde (1cm 3 ) was then added and the mixture stirred at ambient temperature for 4 hours. TLC showed that product had formed. It was extracted into ethyl acetate and the organic layer was dried (MgS0 4 ), filtered and evaporated to give an oil (1.209g). This intermediate product was purified by chromatography on silica gel, eluting with 1:4 ethyl acetate : hexane and gave a yellow oil (0.464g) which had 'H NMR: δ 2.08-2.20(2H,m); 2.48-2.62(2H,m); 2.52 and 2.66 (total 3Rea s); 3.28-3.38(2H,m); 8.28 and 8.84 (total IR ea s), indicating it to be an approximately 1:1 mixture of the 5- and 6-methyl isomers. Step 2; 3-r4.4-difluorobut-3-envlthioV5-methyM-2.4-triazine and 3-T4.4- difluorobut-3-envlthioV6-methyl-1.2.4-tria7ine The mixture of products from Step 1 (0.46g) were dehydrobrominated using DBU in a procedure analogous to Step 2 of Example XX4 and the product (0.253g) was purified by chromatography on silica gel eluting with dichloromethane. Under these conditions the 5- and 6-methyl isomers were inseparable and 0.232g of a yellow oil was obtained which had NT=217; 'H NMR: δ 2.44-2.54(2Rm); 2.50 and 2.66 (total 3H,ea s); 3.26-3.34(2H,m); 4.22- 4.40(lRm); 8.28 and 8.82 (total IR ea s); this indicated it to be a 1:1 mixture of Compound XX52 and Conφound XX 116. Coπφound XX251 according to the invention was prepared using the above procedure but taking cyclohexane-l,2-dione in Step 1 in place of pyruvic aldehyde. 'H NMR: δ 1.86-1.98(4H,m); 2.42-2.54(2Rm); 2.84-2.92(2H,m); 3.04-3.12(2H,m); 3.28(2H,t); 4.22- 4.38(lH,m); (oil). EXAMPLE XX7 This Example illustrates an alternative procedure used for the preparation of Compounds XX52 and XXI 16 as a chromatographically separable mixture. 4,4-difluorobut-3-enyl 4-methyl-benzenesulfonate (lg) and thiosemicarbazide (0.4g) were stirred together and heated under reflux in ethanol (20cm 3 ) for 6 hours. The mixture was allowed to cool overnight, whereupon a crystalline yellow precipitate of the S-alkylated conφound was evident. This was not isolated but solvent was removed by evaporation at reduced pressure and the residue (1.3g) was treated with sodium bicarbonate (0.928g), water (3cm 3 ) and ethanol (20cm 3 ). A 40% by weight solution of pyruvic aldehyde (0.9cm 3 ) was then added (slight effervescence) and the mixture stirred at ambient teπφerature for 1 hour. The reaction was poured into water and the product was extracted into ethyl acetate (3 portions). The combined organic phases were dried (MgS0 4 ), filtered and evaporated to give a brown gum (0.85g). Chromatography on silica gel, eluting with 10% ethyl acetate in hexane gave a fraction which was identified as Compound XXI 16 (0.05g) (containing 10% of Conφound XX52 by NMR). Continued elution gave a mixed fraction containing an approximately 1:1 mixture of Compounds XX52 and XXI 16 (0.16g) and then a fraction identified as Compound XX52 (O.lg) (containing 15% of Conφound XX116 by NMR). EXAMPLE XX.8 This Example illustrates a general procedure for the two-step preparation of coπφounds according to the invention by reaction of thiosemicarbazide with 4-bromo-l,l- difluorobut-1-ene and then cyclisation of the intermediate with a 1,2-dicarbonyl compound, as demonstrated by the following preparation of 3-(4,4-difluorobut-3-enylthio)-l,2,4-triazine (Coπφound XX 137). Thiosemicarbazide (2.6g) was stirred with 4-bromo-l,l-difluorobut-l-ene in ethanol (75cm 3 ) and the mixture heated under reflux for 7 hours and allowed to cool to the ambient temperature. Glyoxal (4.2g of a 40% aqueous solution) and sodium hydrogen carbonate (7.37g) were added and the resulting mixture was stirred at the ambient teπφerature for 18 hours. Water was added and the product was extracted into three portions of ethyl acetate. The combined organic phases were washed with saturated brine, dried (MgS0 4 ), filtered and evaporated under reduced pressure to give a brown gum. Chromatography on silica gel, eluting with 20% ethyl acetate in hexane gave Coπφound XX 137. M + =203; 'H NMR δ 2.50(2Rm); 3.30(2H,t); 4.20-4.40(1 Rm); 8.39(lH,d); 8.95(lRd) (oil). The following compounds according to the invention were prepared using the above procedure with the appropriate 1,2-dicarbonyl compound in place of glyoxal: (i) 3-(4,4-difluorobut-3-enylthio)-5-propyl-l,2,4-triazine (Compound XX27) from 2-oxo- pentanal. M + =245; 'H NMR: δ 1.0(3Rt); 1.7-1.85(2Rm); 2.45-2.55(2Rm); 2.6(2Rt); 3.3(2Rt); 4.2-4.4(1 H,m); 8.8(lRs) (oil). This preparation also gave the isomeric Compound XX109; M + =245; 'H NMR: δ 1.0(3Rt); 1.75-1.9(2Rm); 2.45- 2.55(2Rm); 2.9(2Rt); 3.3(2Rt); 4.2-4.4(lRm); 8.25(lRs) (oil), the latter faster running isomer in the chromatography being approximately 8% of the mixture which was produced, (ii) 3-(4,4-difluorobut-3-enylthio)-5-ethyl-L2.4-triazine (Compound XX30) from 2-oxo- butanal. MM231: 'H NMR: δ 1.3-1.4(3Rt): 2.45-2.55(2Rm); 2.75-2.85(2Rq); 3.25- 3.35(2Rt); 4.2-4.4(lRm); 8.85(lRs) (oil). The isomeric Compound XXI 10 was detected in the reaction mixture but was not isolated. However, it was the major product of the cyclisation when l,l-diethoxy-butan-2-one was used in place of 2-oxo- butanal. Initial imine formation in water followed by cyclisation in aqueous acetone catalysed with pyridinium tosylate gave Compound XX 110. M * =231; 'H NMR: δ 1.4(3Rt); 2.50(2Rm); 2.95(2Rq); 3.3(2Rt); 4.2-4.4(lRm); 8.29(lRs) (oil), (iii) 3-(4,4-difluorobut-3-enylthio)-6-methyl-l,2,4-triazine-5(4H)-one (Conφound XX226) from pyruvic acid. M + =233; 'H NMR (DMSO-de): δ 2.05(3Rs); 2.30(2Rm); 3.12(2H,t); 4.4-4.6(lRm) (gum). The following compounds according to the invention were prepared using the above procedure with a 2,2-dichloro aldehyde in place of glyoxal: (iv) 3-(4,4-difluorobut-3-enylthio)-5-( 1 -methyl-ethyl)- 1 ,2,4-triazine (Compound XX 15). M + =245; 'H NMR: δ 1.32(6Rd); 2.50(2Rm); 3.0(lRm); 3.3(2Rt); 4.20-4.40(1 Rm); 8 ~ .82(lRs) (oil) and the chromatographically faster-running isomer 3-(4,4-difluorobut- 3-enylthio)-6-(l-methyl-ethyl)-1.2,4-triazine (Compound XX98). M"=245; 'H NMR: δ 1.4(6Rd); 2.50(2Rm); 3.18-3.35(3Rm); 4.20-4.40(1 Rm); 8.30(lRs) (oil) from 2,2-dichloro-3-methyl-butanal. EXAMPLE XX.9 This Example illustrates a preparation of 5-dichloromethyl-3-(4,4-difluorobut-3- enylthio)-l,2,4-triazine (Compound XX65) from Compound XX52. Compound XX52 (3.1g) and N-chlorosuccinimide (2g) were stirred and heated together under reflux in carbon tetrachloride (40cm 3 ) for 1 hour. The mixture was allowed to cool and stirred at the ambient temperature for 4 hours. Solvent was removed by evaporation under reduced pressure and the black tarry residue was suspended in diethyl ether (40cm 3 ) and passed through a bed of hi-flo filter aid. Insoluble material was washed with further diethyl ether and the combined solutions were evaporated under reduced pressure. The residue was purified by chromatography on silica, eluting with diethyl ether : hexane 1 : 1 and the fractions containing product were evaporated under reduced pressure and further purified by preparative tic, eluting with 30% diethyl ether in hexane to give Coπφound XX65 (0.2g). 'H NMR: δ 2.50(2Rm); 3.3(2Rt); 4.20-4.40(1 Rm); 6.50(lRs); 9.37(lRs); (oil). EXAMPLE XX.10 This Example illustrates a preparation of 3-(4.4-difluorobut-3-enylsulfonyl)-5-propyl- 1,2,4-triazine (Compound XX28) from Compound XX27. Compound XX27 (0.2g) was stirred at 5°C in dichloromethane (5cm 3 ) and 3-chloro perbenzoic acid (0.282g, 2 equiv.) was added. Stirring continued for 18 hours at the ambient temperature. The reaction was quenched by the addition of a saturated aqueous solution of sodium bicarbonate and the product was extracted into dichloromethane. The organic phase was separated, washed with saturated brine and dried (MgS0 4 ). After filtration and concentration by evaporation under reduced pressure, there was obtained an oil which was purified by chromatography on silica gel using 3 : 7 ethyl acetate : hexane as eluant to give Coπφound XX28 (0.187g). M + =277; 'H NMR: δ 1.0-1. l(3Rt); 1.8-1.95(2Rm); 2.6- 2.7(2Rm); 2.9-3.0(2Rt); 3.7-3.8(2Rt); 4.2-4.4(lRm); 9.3(lRs); (oil). The following compounds according to the invention were prepared by the above procedure, using 1.75 equivalents of oxidant: (i) 3-(4,4-difluorobut-3-enylsulfinyl 5-methyl-l,2,4-triazine (Coπφound XX53); M + =233; 'H NMR: δ 2.35-2.7(2Rm); 2.75(3Rs); 3.2-3.4(2Rm); 4.2^.35(lRm); 9.25(lRs); (oil) and 3-(4,4-difluorobut-3-enylsulfonyl)-5-methyl-l,2,4-triazine (Conφound XX54); MH + =250; 'H NMR: δ 2.6-2.7(2Rm); 2.8(3Rs); 3.7-3.8(2Rt); 4.25-4.4(lRm); 9.35(lRs); (oil) from Compound XX52. (ii) 3-(4,4-difluorobut-3-enylsulfιnyl)-6-methyl- 1 ,2,4-triazine (Conφound XX 117); MH + =234; 'H NMR: δ 2.3-2.75(2Rm); 2.85(3Rs); 3.2-3.4(2Rm); 4.15-4.3(lRm); 8.7(lRs); (oil) and 3-(4,4-difluorobut-3-enylsulfonyl 6-methyl-l,2,4-triazine (Compound XX 118); MH + =250; 'H NMR: δ 2.6-2.7(2Rm); 2.9(3Rs); 3.65- 3.75(2Rt); 4.2-4.4(lRm); 8.75(lRs); (oil) from Compound XXI 16. EXAMPLE XXI, 1 This Example illustrates a preparation of 2-(4,4-difluorobut-3-enylthio)-l,3,5-triazine (Coπφound XXI.l). (4,4-difluorobut-3-enyl)-thiourea (as its 4-methyl-benzenesulfonate salt) (0.9g) and 1,3,5-triazine (0.216g) were heated together under reflux in ethanol (20cm 3 ) for 4 hours. The reaction mixture was cooled and the solvent was removed by evaporation to give a solid which was triturated with hexane. The hexane-soluble material was recovered by evaporation under reduced pressure. This gave Compound XXI (0.4g). =203; 'H NMR: δ 2.45(2Rm); 3.20(2Rt): 4.20-4.40(1 Rm); 8.82(2Rs); (oil). The compounds of formula (I) are nematicidal and can be used to control nematodes in plants. Thus, in a further aspect of the present invention, there is provided a method of killing or controlling nematodes. which comprises applying a compound of formula (I) to the nematode. The term "controlling" extends to non-lethal effects which result in the prevention of damage to the host plant and the limitation of nematode population increase. The effects may be the result of chemical induced disorientation. immobilisation, or hatch prevention or induction. The chemical treatment may also have deleterious effects on nematode development or reproduction. The conφounds of the present invention can be used against both plant parasitic nematodes and nematodes living freely in the soil. Exaπφles of plant-parasitic nematodes are: ectoparasites, for exaπφle, Xiphinema spp., Longidorus spp-, and Trichodorus spp.: semi-parasites, for example, Tylenchulus spp.: migratory endoparasites, for example, Pratylenchus spp.. Radopholus spp. and Scutellonema Spp.; sedentary parasites, for example, Heterodera spp.. Globodera spp. and Meloidogyne spp.; and stem and leaf endoparasites, for example, Ditylenchus spp.. Aphelenchoides spp. and Hirshmaniella spp. The compounds of formula (I) also display activity against different types of nematodes including cyst nematode. The compounds of the present invention also exhibit activity against other pests of growing and stored agronomic crops, forestry, greenhouse crops, ornamentals, nursery crops, stored food and fibre products. These pests include: Heteroptera/Homoptera including Myzαs persicae. Aphis gossypii. Aphis fabae. Rhopalosiphum padi. Aonidiella spp., Trialeurodes spp,. Bemisia tabaci. Nilaparvata lugens. Nephotettix cincticeps. Nezara viridula. Dysdercus suturellus. Dysdercus fasciatus.and Lygus linεo lis. Diptera including Ceratitis capitata. Tipula spp., Oscinella frit Liriomyza spp., Delia spp., and Peromya spp. Lepidoptera including Pieris brassicae. Plutella xylostella. Spodoptera littoralis and other Spodoptera spp., Heliothis virescens and other Heliothis and Helicoverpa spp., and Chilo paπellus. Coleoptera including Phaedon cochleariae. Diabrotica spp., Agrotis spp., and Leptinotarsa decemlineata. Blattodea including Blattella germanica. Periplaneta americana. and Blatta orientalis. Orthoptera including Chortiocetes terminifera. Schistocerca spp., Locusta spp. and Seapteriseus spp.. Acari including Panonvchus ulmi. Panoychus citri. Tetranychus urticae. Tetranychus cinnabarinus. Phyllocoptruta oleivora. and Brevipalpus spp. The compounds can also be used against livestock, household, public and animal health pests such as: Siphonaptera including Qenocephalides felis. Ctenocephalides cards. Xenopsylla cheopis. and Pulex irritans. Mallophaga including Menopon gallinae. and Cuclotogaster heterographus. Anoplura including Pediculus humanus capitis, Pediculus humanus humanus, and Phthirus puhis. Diptera including Musca domestica, Aedes aegypti. Anopheles ga biae. £ulsχ quinquefasciatus. Chrvsops discalis. and Tabanus nigrovittatαs. Sarcophagidae including Sarcophaga haemorrhoidalis and Wohlfahrtia magnifica. Calliphoridae including Lucilia cuprina and Cordylobia anthropophaga . Oestridae including Oestrus ovis. Generally, the compounds may be used to combat and control pests injurious to and/or associated with the transmission of diseases of man and animals. The pests which may be combated and controlled by the use of the compounds of the invention parasitic nematodes of animals, including mammals, which may be found in the gastrointestinal tract, the air passages or blood vessels of the respiratory tract and the heart, together with the associated blood vessels. The compounds of formula (I) may be used to treat vertebrates, such as mammals (for example, man, pigs, sheep, cattle, equines, cats and dogs), birds (for exanφle, chicken, ducks, turkeys, geese, canaries and budgerigars), and fish (for example, salmon, trout and ornamental fish). The nematode and other pests may be killed/controlled by applying an effective amount of one or more of the compounds of the present invention to the environment of the pests, to the area to be protected, as well as directly on the pests. In order to apply the compound to the locus of the nematode, insect or acarid pest, or to a plant susceptible to attack by the nematode, insect or acarid pest, the conφound is usually formulated into a composition which includes in addition to the conφound of formula (I) suitable inert diluent or carrier materials, and/or surface active agents. Thus in two further aspects of the invention there is provided a nematicidal, insecticidal or acaricidal composition comprising an effective amount of a compound of formula (I) as defined herein and an inert diluent or carrier material and optionally a surface active agent. The amount of composition generally applied for the control of nematode pests gives a rate of active ingredient from 0.01 to 10 kg per hectare, preferably from 0.1 to 6 kg per hectare. The compositions can be applied to the soil, plant, seed, or other area to be protected, to the locus of the pests, or to the habitat of the pests, in the form of dusting powders, wettable powders, granules (slow or fast release), emulsion or suspension concentrates, liquid solutions, emulsions, seed dressings, fogging/smoke formulations or controlled release compositions, such as microencapsulated granules or suspensions. Dusting powders are formulated by mixing the active ingredient with one or more finely divided solid carriers and/or diluents, for example natural clays, kaolin, pyrophyllite, bentonite, alumina, montmorillonite, kieselguhr, chalk, diatomaceous earths, calcium phosphates, calcium and magnesium carbonates, sulfur, lime, flours, talc and other organic and inorganic solid carriers. Granules are formed either by absorbing the active ingredient in a porous granular material for example pumice, attapulgite ^ clays, fuller's earth, kieselguhr, diatomaceous earths, ground com cobs, and the like, or on to hard core materials such as sands, silicates, mineral carbonates, sulfates, phosphates, or the like. Agents which are commonly used to aid in impregnation, binding or coating the solid carriers include aliphatic and aromatic petroleum solvents, alcohols, polyvinyl acetates, polyvinyl alcohols, ethers, ketones, esters, dextrins, sugars and vegetable oils, with the active ingredient. Other additives may also be included, such as emulsifying agents, wetting agents or dispersing agents. Microencapsulated formulations (microcapsule suspensions CS) or other controlled release formulations may also be used, particularly for slow release over a period of time, and for seed treatment. Alternatively the compositions may be in the form of liquid preparations to be used as dips, irrigation additives or sprays, which are generally aqueous dispersions or emulsions of the active ingredient in the presence of one or more known wetting agents, dispersing agents or emulsifying agents (surface active agents). The compositions which are to be used in the form of aqueous dispersions or emulsions are generally supplied in the form of an emulsifiable concentrate (EC) or a suspension concentrate (SC) containing a high proportion of the active ingredient or ingredients. An EC is a homogeneous liquid composition, usually containing the active ingredient dissolved in a substantially non-volatile organic solvent. An SC is a fine particle size dispersion of solid active ingredient in water. To apply the concentrates they are diluted in water and are usually applied by means of a spray to the area to be treated For agricultural or horticultural purposes, an aqueous preparation containing between 0.0001% and 0.1% by weight of the active ingredient (approximately equivalent to from 5-2000g ha) is particularly useful. Suitable liquid solvents for ECs include methyl ketone, methyl isobutyl ketone, cyclohexanone, xylenes, toluene, chlorobenzene, paraffins, kerosene, white oil, alcohols, (for exanφle, butanol), methylnaphthalene, trimethylbenzene, trichloroethylene, N-methyl-2-pyrrolidone and tetrahydroiurfuryl alcohol (THFA). Wetting agents, dispersing agents and emulsifying agents may be of the cationic, anionic or non-ionic type. Suitable agents of the cationic type include, for example, quaternary ammonium compounds, for example cetyltrimethyl ammonium bromide. Suitable agents of the anionic type include, for example, soaps, salts of aliphatic monoesters of sulfuric acid, for example sodium lauryl sulfate, salts of sulfonated aromatic compounds, for exanφle sodium dodecylbenzenesulfonate, sodium, calcium or ammonium lignosulfonate, or butylnaphthalene sulfonate, and a mixture of the sodium salts of diisopropyl- and triisopropylnaphthalene sulfonates. Suitable agents of the non-ionic type include, for example, the condensation products of ethylene oxide with fatty alcohols such as oleyl alcohol or cetyl alcohol, or with alkyl phenols such as octyl phenol, nonyl phenol and octyl cresol. Other non-ionic agents are the partial esters derived from long chain fatty acids and hexitol anhydrides, the condensation products of the said partial esters with ethylene oxide, and the lecithins. These concentrates are often required to withstand storage for prolonged periods and after such storage, to be capable of dilution with water to form aqueous preparations which remain homogeneous for a sufficient time to enable them to be applied by conventional spray equipment. The concentrates may contain 1-85% by weight of the active ingredient or ingredients. When diluted to form aqueous preparations such preparations may contain varying amounts of the active ingredient depending upon the purpose for which they are to be used. The compounds of formula (I) may also be formulated as powders (dry seed treatment DS or water dispersible powder WS) or liquids (flowable concentrate FS, liquid seed treatment LS). or miCTocapsule suspensions CS for use in seed treatments. The formulations can be applied to the seed by standard techniques and through conventional seed treaters. In use the compositions are applied to the nematodes. to the locus of the nematodes. to the habitat of the nematodes, or to growing plants liable to infestation by the nematodes, by any of the known means of applying pesticidal compositions, for exanφle, by dusting, spraying, or incorporation of granules. The compounds of the invention may be the sole active ingredient of the composition or they may be admixed with one or more additional active ingredients such as nematicides or agents which modify the behaviour of nematodes such as hatching factors, insecticides, synergists, herbicides, fungicides or plant growth regulators where appropriate. Suitable additional active ingredients for inclusion in admixture with the conφounds of the invention may be compounds which will broaden the spectrum of activity of the coπφounds of the invention or increase their persistence in the location of the pest. They may synergise the activity of the compound of the invention or complement the activity for example by increasing the speed of effect or overcoming repellency. Additionally multi-component mixtures of this type may help to overcome or prevent the development of resistance to individual components. The particular additional active ingredient included will depend upon the intended utility of the mixture and the type of complementary action required. Exaπφles of suitable insecticides include the following: a) Pyrethroids such as permethrin, esfenvalerate, deltamethrin, cyhaJothrin in particular lambda-cyhalothrin. bifenthrin, fenpropathria cyfluthrin, tefluthrin, fish safe pyrethroids for example ethofenprox, natural pyrethrin, tetramethrin, s-bioallethrin, fenfluthrin, prallethrin and 5-benzyl-3-furylmethyl-(E)-(lR,3S)-2,2-dimethyl- 3-(2-oxothiolan-3-ylidenemethyl) cyclopropane carboxylate; b) Organophosphates such as profenofos, sulprofos, methyl parathion, azinphos-methyl, demeton-s-methyl. heptenophos, thiometon, fenamiphos, monocrotophos, triazophos, methamidophos. dimethoate, phosphamidon, malathion, chloropyrifos, phosalone, terbufos. fensulfothion. fonofos, phorate, phoxim. pyrimiphos-methyl, pyrimiphos-ethyl, fenitrothion or diazinon; c) Carbamates (including aryl carbamates) such as pirimicarb, cloethocarb, carbofuran, fiirathiocarb. ethiofencarb. aldicarb. thiofurox carbosulfaa bendiocarb. fenobucarb, propoxur or oxamyl: d) Benzoyl ureas such as triflumuron. or chlorofluazuron; e) Organic tin compounds such as cyhexatin, fenbutatin oxide, azocyclotin; f) Macrolides such as avermectins or milbemycins, for exanφle such as abamectin, ivermectin and milbemycin; g) Hormones and pheromones; h) Organochlorine compounds such as benzene hexachloride, DDT, endosulphan, chlordane or dieldrin; i) Amidines, such as chlordimeform or amitraz j) Fumigant agents; k) Nitromethylenes such as imidacloprid. In addition to the major chemical classes of insecticide listed above, other insecticides having particular targets may be employed in the mixture if appropriate for the intended utility of the mixture. For instance selective insecticides for particular crops, for example stemborer specific insecticides for use in rice such as cartap or buprofezin can be employed Alternatively insecticides specific for particular insect species/stages for example ovo-larvicides such as clofentezine, flubenzimine, hexythiazox and tetradifon, motilicides such as dicofol or propargite, general acaricides such as bromopropylate, chlorobenzilate, or growth regulators such as hydramethylnon, cyromazine, methoprene, chlorfluazuron and diflubenzuron may also be included in the compositions. Exaπφles of suitable synergists for use in the compositions include piperonyl butoxide, sesamax, safroxan and dodecyl imidazole. Suitable herbicides, fungicides and plant-growth regulators for inclusion in the compositions will depend upon the intended target and the effect required An example of a rice selective herbicides which can be included is propanil, an exaπφle of a plant growth regulator for use in cotton is "Pix", and exaπφles of fungicides for use in rice include blasticides such as blasticidin-S. The ratio of the coπφound of the invention to the other active ingredient in the composition will depend upon a number of factors including type of target, effect required from the mixture etc. However in general, the additional active ingredient of the composition will be applied at about the rate as it is usually employed or at a slightly lower rate if synergism occurs. EXAMPLE 1 The activity of compounds of formula (I) according to the invention was determined using a variety of pests. The pests were treated with a liquid composition containing 500 parts per million (ppm) by weight of the compound unless otherwise stated The compositions were made by dissolving the compound in acetone : ethanol (50:50) mixture and diluting the solutions with water containing 0.05% by weight of a wetting agent sold under the trade name "Synperonic" NP8 until the liquid composition contained the required concentration of the compound. "Synperonic" is a Registered Trade Mark. The test procedure adopted with regard to each pest was basically the same and comprised supporting a number of the pests on a medium which was usually a host plant or a foodstuff on which the pests feed and treating either or both the medium and the pests with the compositions. The mortality of the pests was then assessed at periods usually varying from one to three days after the treatment. The results of the tests are presented in Table A for each of the conφounds. The results indicate a grading of mortality designated as A, B or C wherein A indicates less than 40% mortality, B indicates 40-79% mortality and C indicates 80-100% mortality; - indicates that either the compound was not tested or no meaningful result was obtained Information regarding the pest species, the support medium or food, and the type and duration of the test is given in Table B. The pest species is designated by a letter code. DB B C A DB Diabrotica balteata Filter paper/ Residual 2 (banded cucumber beetle maize seed - larva) "Contact" test indicates that both pests and medium were treated and "Residual" indicates that the medium was treated before infestation with the pests. EXAMPLE 2 This Example further illustrates the pesticidal activity of compounds of formula (I) according to the invention. In Table C, further results are given for the activity of test compounds against four species, at various rates of application. The test procedures and details for tests TU (Tetranychus urticae. contact), MPa fMyzus persicae. contact) and DB fDiabrotica balteata. contact) are as described in Example 1 and Table B. Application rates are shown in the Table heading for each test type. The test procedure for test MPb (Myzus persicae. systemic) was as follows: Upward systemicity of the test compounds was evaluated against the peach potato aphid, Myzus persicae by soil drenching 2-3 week old radish plants (cv. Cherrybelle) at lOppm or 2.5ppm. Plants with 1st true leaves approximately 2 x 1 cm were used The cotyledons, growing point and 1 true leaf were removed. The soil was covered with a clear lid. 12-18 mature aphids were added to each plant 1 day before treatment. On the treatment day, each pot was placed in a 250cm 3 plastic pot with a fluon band to prevent aphid escape. Each pot was treated with 10cm 3 of chemical in aqueous solution (prepared in 1% ethanol and acetone (1:1) and 0.01% Synperonic NP8 - ICI Chemicals and Polymers). Each treatment was replicated 3 times. The treated plants were transferred to a constant environment room at 20°C, 60%) relative humidity and a 16 hour photoperiod The mortality was assessed at 3 and 5 days after treatment. Activity against the root knot nematode, Meloidogyne incognita ( ), was evaluated by applying the candidate nematicide as a drench solution to 2 week old cucumber plants (cultivar Telegraph) and infesting the soil with nematodes. 10 cm 3 of an aqueous solution of the test compound, (prepared in 1% ethanol and acetone (1:1) and 0.05% Synperonic NP8 - ICI Chemicals & Polymers) was added to each plant such that the final soil concentration was 2 ppm. Each treatment was replicated twice. The cucumber plants were inoculated 48 hours after treatment with a 2 cm 3 suspension of freshly hatched juveniles at a concentration of 350 nematodes per cm 3 . The test was maintained at 25°C with a 16 hour photoperiod for 9 days. The roots of each plant were assessed for percentage root-knot reduction relative to an untreated infested control and the results are recorded in Table C as % knot reduction compared to the control. The results in Table C for the four species other than MI are expresed as % Control observed. A dash indicates that either the compound was not tested or that no meaningful result was obtained. TABT.F. C MPa MPa MPb MPb DB MI ppm 100 ppm 27 ppm lOppm 2.5ppm 25 ppm 2ppm 1 - 95 100 - 100 0 4 - 96 96 88 98 97 98 93 0 48 0 0 0 0 0 96 100 100 0 0 11 97 - - 99 88 84 - 55 - 0 72 100 - 10 - 0 50 - 100 - 92 2 - - - 99 5 - 98 100 - 100 97 - - 77 22 0 72 55 100 95 100 53 98 88 100 17 97 92 99 0 0 95 98 86 0 96 - - 0 91 100 96 - 100 60 0 76 68 50 - 98 98 - 99 96 - 100 83 66 49 - 97 90 - 92 49 - 96 86 94 66 0 93 - 95 - - - 0 0 - . - - 33 44 - - 66 28 100 98 - 99 18 - - 39 Vm.7 43 90 - - vm.io . . . 42 vm.i9 . . . . vm.2θ . . . 4 vm.22 . . . . vm.27- . . . 0 vm.3i . . . . vm.32 . . . . vm.52 . . . . vm.6i . . . . vm.63 . . . . Vπi.64 29 vm.67 . . . . vπι.151 loo loo 171 0 - . 44 0 - - 94 2 - - 0 61 30 - - 50 9 - - 72 83 86 61 100 - - 72 99 3 100 - 97 65 94 50 100 52 94 82 88 96 100 30 - 13 100 26 - 99 100 - 95 48 - 98 95 - 86 97 4 14 99 - 100 98 - 98 100 - 92 52 - 93 100 100 95 77 100 92 - 100 vj3 >—' +- J >— ■ 4-. >— ■ —) i— » ' i—* -O .— > VO Uι J>. V0 4>. -0 00 Ul OJ Ov © OO O Uι OJ Uι O OJ O Ui -^J OJ OJ OJ ^- VO ~0 © O © © © 1 OO OO ' OO OJ .— ' ' i— . ι_- ι_-ι v ι—. ι_- >— . OJ • — to •—• '—» *. ' O -O -O © © © O OO O O O © © o © © to © o © o o © © © © o to OO to vo vo vo O vo ■ vo O VO vo Q0 ' VO O VO ON VO O O 00 >— > Ui 00 VO Ul .J-. Φ *»• VO O O Vθ J 31 0 0 95 94 97 37 84 89 98 96 97 0 96 94 - 100 91 - 100 73 91 - 99 100 - 93 - 96 92 - 100 61 47 95 - 100 100 - 99 95 - 99 71 - 98 - 96 96 - 100 21 100 94 95 - - - 94 97 79 - 92 - 99 100 - 97 51 100 - - 100 100 - 52 - 100 100 - 94 79 26 - - 0 0 - - - 0 EXAMPLE 3 The spectrum of nematicidal activity of compounds according to the invention was investigated in contact assays in the presence of soil and a host plant. Greatest activity was seen against Meloidogyne incognita. Globodera rostochiensis. Pratylenchus brachyums. Tylenchorhynchus claytoni. Hoplolaimus columbus and Radopholus similis. Adequate activity was seen against Rotylenchulus reniformis. and Belonolaimus longicaudatus. The following examples demonstrate formulations suitable for applying the compounds of the present invention. The amount of ingredient is expressed in parts by weight or grams per litre as indicated. A * indicates a trademark. EXAMPLE 4 This example demonstrates granules suitable for soil application. The granules can be made by standard techniques such as impregnation, coating, extrusion or agglomeration. %w/w Impregnated granule : Active ingredient 5 Wood Rosin 2.5 Gypsum granules 92.5 (20-40 mesh) Coated granule : Active ingredient 0.5 ^ Solvesso'* 200 0.4 Calcium carbonate granules 99.1 (30-60 mesh) Slow release granule : Active ingredient 10 Polyvinylacetate/vinyl 5 chloride copolymer latex Attapulgus granules 85 EXAMPLE 5 This Example demonstrates formulations for use as a spray. The coπφounds can be formulated as wettable powders, water dispersible granules, suspension concentrates, emulsifiable concentrates, emulsions or microcapsule suspensions for application diluted in water. The suspension concentrate and microcapsule suspension of Example 5 can be used as flowable concentrates for seed treatment. EXAMPLE 7 This Example demonstrates the formulation of the compounds for electrostatic spraying. EXAMPTE 1 1 This Example demonstrates a formulation suitable for use as an injectable solution. mg Active ingredient 20 Sodium citrate 6 Citric acid 1 Sodium chloride 7 Chlorcresol 1 Water to 1ml EXAMPLE 12 This Example demonstrates a formulation suitable for use as an oral suspension. g Active ingredient 100.0 Polysorbate 80 2.0 Xanthan gum 5.0 Colloidal silicon dioxide 10.0 Methyl hydroxybenzoate 1.5 Citric acid monohydrate 10.0 Sodium citrate 10.0 Purified water to 1000.0ml CHEMICAL FORMULAE (IN DESCRIPTION) R-S(0) n CH 2 CH 2 CH=CF 2 (I) (II ) (III) (IV) ( VIII ) (IX) (X) (Xi) (xi") (XIII) CHEMICAL FORMULAE (IN DESCRIPTION) (XV) (XVI (XIV) ( XVIII ) (XXI)- CHEMICAL FORMULAE (IN DESCRIPTION) R • SH (XXIII) CF 2 =CHCH 2 CH 2 L (XXIV) CF 2 =CHCH 2 CH 2 Br (XXVI) R - L (XXVII) CF 2 =CHCH 2 CH 2 SH (XXVIII) R - NH 2 (XXIX) (XXX)

Claims: Claims. 1. A compound of formula (I), R-S(0) π CH 2 CH : CH=CF 2 or a salt thereof, wherein n is 0, 1 or 2; and R is a group of formula (II) to (XXI), (H) (iii) (iv) (VIM) (|χ) - ( X) (XIII) (XI) (Xll) (XIV) (XV) (XVI) (XIX) (XX) (XXI) wherein: the S(0)nCH2CH2CH=CF2 group is at least one of Rl (when attached to a carbon atom), R2, R3. R4, R5 or R6; Rl (when attached to a carbon atom), R2, R3, R4, R5 and R6 are each independently hydrogen, optionally substituted alkyl, optionally substituted alkenyl, alkynyl, cycloalkyl, alkylcycloalkyl, alkoxy, alkenyloxy, alkynyloxy, hydroxyalkyl, alkoxyalkyl, optionally substituted aryl, optionally substituted arylalkyl, optionally substituted heteroaryl, optionally substituted heteroarylalkyl. optionally substituted aryloxy. optionally substituted arylalkoxy, optionally substituted aryloxyalkyl, optionally substituted heteroaryloxy, optionally substituted heteroarylalkoxy, optionally substituted heteroaryloxyalkyl, haloalkyl. haloalkenyl, haloalkynyl, haloalkoxy, haloalkenyloxy, haloalkynyloxy, halogen, hydroxy, cyano, nitro, -NR7R8, -NR7COR8, -NR7CSR8, -NR7S02R8. -N(S02R7XS02R8), -COR7, -CONR7R8, - alkylCONR7R8, -CR7NR8, -COOR7. -OCOR7. -SR7, -SOR7, -S02R7, -alkylSR7, - alkylSOR7, -alkylS02R7, -OS02R7, -S02NR7R8, -CSNR7R8, -SiR7R8R9, -OCH2C02R7, -OCH2CH2C02R7, -CONR7S02R8, -alkylCONR7S02R8, -NHCONR7R8, -NHCSNR7R8, or an adjacent pair of Rl. R2, R3, R4, R5 and R6 when taken together form a fused 5- or 6-membered carbocyclic or heterocyclic ring; Rl (when attached to a nitrogen atom) is hydrogen, optionally substituted alkyl, cycloalkyl, alkylcycloalkyl, hydroxyalkyl, alkoxyalkyl, optionally substituted aryl, optionally substituted arylalkyl, optionally substituted aryloxyalkyl, optionally substituted heteroaryl, optionally substituted heteroarylalkyl, optionally substituted heteroaryloxyalkyl, haloalkyl, hydroxy, cyano, nitro, -NR7R8, -NR7COR8, NR7CSR8, -NR7COOR8, -NR7S02R8, - N(S02R7XS02R8), -COR7, -CONR7R8, -alkylCONR7R8, -CR7NR8, -COOR7, -OCOR7, - SOR7, -S02R7, -alkylSR7, -alkylSOR7, -alkylS02R7, -OS02R7, -S02NR7NR8, -SR7, - SOR7, -S02R7, -CSNR7R8, -SiR7R8R7, -OCH2C02R7, -OCH2CH2C02R7, - CONR7S02R8, -alkylCONR7S02R8, - NHCOR7R8, or -NHCSR7R8; and R7, R8 and R9 are each independently hydrogen, optionally substituted alkyl, optionally substituted alkenyl, alkynyl, optionally substituted aryl or optionally substituted arylalkyl, haloalkyl, haloalkenyl, haloalkynyl, halogen, or hydroxy. 2. A compound according to claim 1, wherein: the -S(0)nCH2CH2CH=CF2 group is at least one of Rl (when attached to a carbon atom), R2, R3, R4, R5 or R6; Rl (when attached to a carbon atom), R2, R3, R4, R5 and R6 are each independently hydrogen, optionally substituted Cl-6 alkyl, optionally substituted C2-6 alkenyl, optionally substituted C2-6 alkynyl, C3-6 cycloalkyl, C4-7 alkylcycloalkyl, Cl-6 alkoxy, C2-6 alkenyloxy, C2-6 alkynyloxy, Cl-6 hydroxyalkyl, C2-6 monoalkoxyalkyl, C3-6 dialkoxyalkyl, optionally substituted C6-10 aryl, optionally substituted C6-10 aryl-Cl-2 alkyl group, optionally substituted 5 or 6 membered heteroaryl, optionally substituted 5 or 6 membered heteroaryl-Cl-6 alkyl, optionally substituted C6-10 aryloxy, optionally substituted C6-10 aryl- Cl-2 alkoxy, C6-10 aryloxy-Cl-6 alkyl. optionally substituted 5 or 6 membered heteroaryloxy. optionally substituted 5 or 6 membered heteroaryl-Cl-6 alkoxy, 5 or 6 membered heteroaryloxy-Cl-2 alkyl, Cl-6 haloalkyl, C2-6 haloalkenyl, C2-6 haloalkynyl, Cl-6 haloalkoxy, C2-6 haloalkenyloxy. C2-6 haloalkynyloxy, halogen, hydroxy, cyano, nitro, -NR7R8, -NR7COR8. -NR7CSR8, -NR7S02R8. -N(S02-R7)(S02-R8), -COR7, -CONR7R8, -Cl-6 alkylCONR7R8, -CR7NR8, -COOR7, -OCOR7, -SR7, -SOR7, -S02R7, -Cl-6 alkylSR7, -Cl-6 alkylSOR7, -Cl-6 alkyl-S02R7-OS02R7, -S02NR7R8, -CSNR7R8, -SiR7R8R9, -OCH2C02R7, -OCH2CH2C02R7, -CONR7S02R8, -Cl-6 alkylCONR7S02R8, -NHCONR7R8. -NHCSNR7R8 or an adjacent pair of Rl, R2, R3 and R4 when taken together form a fused 5- or 6-membered carbocyclic or heterocyclic ring; Rl (when attached to a nitrogen atom) is hydrogen, optionally substituted Cl-6 alkyl, C3-6 cycloalkyl, C4-6 alkylcycloalkyl, Cl-6 hydroxyalkyl, C2-6 monoalkoxyalkyl, C3-6 dialkoxyalkyl, optionally substituted C6-10 aryl, optionally substituted C6-10 aryl-Cl-2 alkyl, optionally substituted C6-10 aιyloxy-Cl-6 alkyl, optionally substituted 5 or 6 membered heteroaryl, optionally substituted 5 or 6 membered heteroaryl-Cl-2 alkyl, optionally substituted 5 or 6 membered heteroaryloxy-Cl-2 alkyl, Cl-6 haloalkyl, hydroxy, cyano, nitro, -CONR7R8, -Cl-6 alkylCONR7R8, - NHCOR7R8, -NHCSR7R8, -NR7R8, -NR7COR8, NR7CSR8, -NR7COOR8, -NR7S02R8, -N(S02R7)(S02R8), -COR7, -COOR7, -OCOR7, - OS02R7, -S02NR7N6, -S02R7, -SOR7, -CSNR7R8, -SiR7R8R7, -OCH2C02R7, - OCH2CH2C02R7, -CONR7S02R8, or -Cl-6 alkylCONR7S02R8; and R7, R8 and R9 are each independently hydrogen, optionally substituted Cl-6 alkyl, optionally substituted C2-6 alkenyl, C2-6 alkynyl, Cl-6 haloalkyl, C2-6 haloalkenyl, C2-6 haloalkynyl, optionally substituted C4-6 aryl or optionally substitututed C4-6 aryl-Cl-6 alkyl, halogen or hydroxy. 3. A compound according to claim 2, wherein when any one of Rl to R6 is: - substituted alkyl, or contains a substituted alkyl moiety, it comprises one or more substituents chosen from halogen, nitro, cyano, -COOR7 or a salt thereof, hydroxy, alkoxy, alkoxyimino. alkoxycarbonyl, carbomyl, mono- or di-alkylcarbamoyl, amino, mono- or di- alkylamino, acylamido, alkanesulfonyl and arylsulfonyl; - substituted alkenyl, or contains a substituted alkenyl moiety, it comprises one or more substituents chosen from halogen, COOR7 or a salt thereof, hydroxy, nitro and cyano; - substituted aryl or heteroaryl, or contains a substituted sryl or heteroaryl moiety, it comprises one or more substituents chosen from alkyl, alkoxy, haloalkyl, halogen, hydroxy, ROOR7 or a salt thereof, aminosulfonyl. cyano and nitro. 4. A compound according to either of claims 2 and 3 wherein when any one of Rl to R6 is -SR7, it is preferably optionally substituted Cl-6 alkylthio, C2-6 alkenylthio, C2-6 alkynylthio, Cl-6 haloalkyl, C2-6 haloalkenylthio, C2-6 haloalkynylthio or C6-10 arylthio. 5. A compound according to claim 1 wherein: at least one of Rl (when attached to a carbon atom) is the -S(0)nCH2CH2CH=CF2 group; Rl (when attached to a carbon atom) to R6 are each independently hydrogen; nitro; halogen; cyano; -CH=NOH; Cl-4 alkyl; Cl-4 haloalkyl; Cl-4 alkenyl; Cl-4 haloalkenyl; cyclopropyl; hydroxy; Cl-4 alkoxy; C2-4 alkoxyalkyl; -COOH; C2-4 alkoxycarbonyl; C2-4 haloalkenyloxycarbonyl; -CONH2; mono or di-Cl-2 alkylaminocarbonyl; C2- alkanecarbonyl; phenyl optionally mono- or di- substituted with groups independently chosen from halogen, nitro, Cl-4 alkyl, Cl-4 alkoxy or aminosulfonyl; -CONHS02-C1-4 alkyl; benzyl optionally mono- or di- substituted with groiφs independently chosen from halogen, nitro, Cl-4 alkyl or Cl-4 alkoxy; phenoxy optionally mono- or di- substituted with groiφs independently chosen from halogen, cyano, Cl-4 alkyl or Cl-4 alkoxy; amino optionally mono- or di- substituted with Cl-4 alkyl groups; -SH; Cl-4 alkylthio; benzylthio optionally mono- or di- substituted with groups independently chosen from halogen or Cl-4 haloalkyl; Cl-4 alkenylthio; C2-4 haloalkenylthio; a second S(0)nCH2CH2CH=CF2 group; Cl-4 alkanesulfonyl; Cl-4 haloalkanesulfonyl; fluorosulfonyl; mono- or di- Cl-4 alkylsulfamoyl; a 5 or 6 membered heteroaryl group optionally substituted with halogen; or any adjacent pair forms a fused 5- or 6- carbocyclic or heterocyclic ring; and Rl (when attached to a nitrogen atom) is hydrogen; nitro; cyano; -CH=NOH; Cl-4 alkyl; Cl-4 haloalkyl; cyclopropyl; hydroxy; -COOH; C2-4 alkoxycarbonyl; C2-4 haloalkenyloxycarbonyl; -CONH2; mono or di-Cl-2 alkylaminocarbonyl; C2-4 alkanecarbonyl; phenyl optionally mono- or di- substituted with groups independently chosen from halogen, nitro, Cl-4 alkyl, Cl-4 alkoxy or aminosulfonyl; -CONHS02-C1-4 alkyl; benzyl optionally mono- or di- substituted with groups independently chosen from halogen, nitro, Cl-4 alkyl or Cl-4 alkoxy; phenoxy optionally mono- or di- substituted with groiφs independently chosen from halogen, cyano, Cl-4 alkyl or Cl-4 alkoxy; amino optionally mono- or di- substituted with Cl-4 alkyl groups; -SH; Cl-4 alkylthio; benzylthio optionally mono- or di- substituted with groups independently chosen from halogen or Cl-4 haloalkyl; Cl-4 alkenylthio; C2-4 haloalkenylthio; Cl-4 alkanesulfonyl; Cl-4 haloalkanesulfonyl; fluorosulfonyl; mono- or di- Cl-4 alkylsulfamoyl; a 5 or 6 membered heteroaryl group optionally substituted with halogen. 6. A process for the preparation of a compound of any one of claims 1 to 3, where n is 0, comprising reacting a compound of formula (XXIII) R-SH (XXHI) with a compound of formula (XXTV) CF 2 =CHCH 2 CH 2 L (XXTV) where R is as defined in any one of claims 1 to 3, and L is a good leaving group. 7. A process for the preparation of a compound of any one of claims 1 to 3, where n is 0, comprising reacting a compound of formula (XXVTI) R-L (XXVII) with a compound of formula (XXVTH) CF 2 =CHCH 2 CH 2 SH (XXVIII) where R is as defined in any one of claims 1 to 3, and L is a good leaving group. 8. A process for the preparation of a compound of any one of claims 1 to 3. when n is 1 or 2, which comprises oxidation of the correspondingly substituted compound of formula (I) when n is 0. 9. An agricultural composition comprising a compound of any one of claims 1 to 3 as the active ingredient in admixture with an agriculturally acceptable diluent or carrier. 10. An agricultural composition according to claim 9, further comprising a surface active material. 11. An agricultural composition according to either of claims 9 and 10, further comprising at least one other active ingredient which is an insecticide, fungicide, bactericide, acaricide or other biologically active compound. 12. A process for preparing an agricultural composition of any one of claims 9 to 11, comprising admixing the compound of any one of claims 1 to 3 and the agriculturally acceptable diluent or carrier. 13. A method for killing or controlling nematode, insect or acarid pests comprising applying a coπφound of any one of claims 1 to 3, or a composition of any one of claims 9 to 11, to the pests, their habitat or a plant susceptible to attack by the pests.

Inventors: BANSAL HARJINDER SINGH, DOWLING ALAN JOHN, FITZJOHN STEVEN, GODFREY CHRISTOPHER RICHARD AY, HOTSON MATTHEW BRIAN, SALMON ROGER, SILLARS NAN CATHERINE, SMITH ALISON MARY, TURNBULL MICHAEL DRYSDALE, BANSAL, HARJINDER, SINGH, DOWLING, ALAN, JOHN, FITZJOHN, STEVEN, GODFREY, CHRISTOPHER, RICHARD, AYLES, HOTSON, MATTHEW, BRIAN, SALMON, ROGER, SILLARS, NAN, CATHERINE, SMITH, ALISON, MARY, TURNBULL, MICHAEL, DRYSDALE
Applicants: BANSAL HARJINDER SINGH, DOWLING ALAN JOHN, FITZJOHN STEVEN, GODFREY CHRISTOPHER RICHARD AY, HOTSON MATTHEW BRIAN, SALMON ROGER, SILLARS NAN CATHERINE, SMITH ALISON MARY, TURNBULL MICHAEL DRYSDALE, ZENECA LTD, BANSAL, HARJINDER, SINGH, DOWLING, ALAN, JOHN, FITZJOHN, STEVEN, GODFREY, CHRISTOPHER, RICHARD, AYLES, HOTSON, MATTHEW, BRIAN, SALMON, ROGER, SILLARS, NAN, CATHERINE, SMITH, ALISON, MARY, TURNBULL, MICHAEL, DRYSDALE, ZENECA LIMITED
Application year: 1995
Main classification: C07D307
IPC codes: A01N33, A01N41, A01N43, A01P5, A01P7, C07C17, C07C317, C07C323, C07D213, C07D231, C07D233, C07D237, C07D241, C07D251, C07D253, C07D257, C07D261, C07D263, C07D271, C07D275, C07D277, C07D285, C07D307, C07D333, C07D409, C07D413, C07D417, C07D471