PROCESS FOR PREPARING TRICHLOROALKANE DERIVATIVES

Abstract: According to the present invention there is provided a process for the production of a trichloroalkane derivative comprising reacting an alkene derivative with chloroform, characterised in that the process is initiated by photochemical cleavage of an initiator of formula (I), wherein Z is chloro or fluoro; X is hydrogen, C1-6 alkyl, C1-6 haloalkyl, -O-O-C(O)-Y or -O-O-Y; and Y is hydrogen, C1-6 alkyl or C1-6 haloalkyl. The process is of particular use for the production of 4,4,4-trichlorobutane derivatives.

Description: PROCESS FOR PREPARING TRICHLOROALKANE DERIVATIVES The present invention relates to a process for preparing trichloroalkane derivatives by the photochemically initiated addition of chloroform to an alkene derivative. The process is of particular use for the production of 4,4,4-trichlorobutane derivatives which are important intermediates and products in the chemical industry. As an example, 4,4,4-trichlorobutane derivatives are useful as intermediates in the manufacture of pesticidal compounds of the type described in, for example, WO 95/24403. 4,4,4-Trichlorobutane derivatives may also be used as intermediates in the manufacture of compounds having useful solvent properties. According to the present invention there is provided a process for the production of a trichloroalkane derivative comprising reacting an alkene derivative with chloroform, characterised in that the process is initiated by photochemical cleavage of an initiator of formula (I): wherein Z is chloro or fluoro; X is hydrogen, C,^ alkyl, C,_ 6 haloalkyl, -O-O-C(O)-Y or -O-O-Y; and Y is hydrogen, C w alkyl or C^ haloalkyl. Alkyl is straight or branched chain and is, for example, methyl, ethyl, w-propyl, w-butyl, H-pentyl, w-hexyl, .sO-propyl, /7-butyl, sec-butyl, wo-butyl, tert-butyl or «eø-pentyl. Haloalkyl groups are alkyl groups which are optionally substituted with one or more of the same or different halogen atoms. Halogen is fluorine, chlorine, bromine or iodine. The photochemical cleavage of the initiator of formula (I), which is the result of absorption of an appropriate photon, results in the direct or indirect formation of the radical Z 3 C » . The process of the invention may provide higher yields of the trichloroalkane derivative and fewer by-products than corresponding processes, for example, those using thermal initiation, or photochemical processes performed in the absence of an initiator or with an initiator not having a trihalocarbonyl group. The three Z groups in the initiator of formula (I) may be the same or different. CZ 3 may be, for example, CF 2 C1, however CZ 3 is preferably CC1 3 . X is preferably C w haloalkyl or -O-O-Y, wherein Y is C w haloalkyl. C,. 6 Haloalkyl is preferably CF 2 C1, more preferably CC1 3 . Preferred examples of initiators of formula (I) include 1,3-dichloro-l, 1,3,3- tetrafluoroacetone, chloral and, especially, hexachloroacetone. The alkene derivative used in the process of the invention preferably has a terminal double bond. The process of the invention is of particular use for the production of 4,4,4-trichlorobutane derivatives, as illustrated in Scheme I below, wherein Z and X are as described above for formula (I); W is C,^ alkyl, C w alkenyl, OR 1 or NR 2 R 3 ; R 1 is hydrogen, C,^ alkyl, C 2 . 6 alkenyl, C 6 . l0 aryl or R 4 C(O); R 2 and R 3 are, independently, hydrogen, C,. 6 alkyl, C^ alkenyl or C 6 . 10 aryl; and R 4 is C,. 6 alkyl, C 2.6 alkenyl, C 6.I0 aryl, C,^ alkyloxy, C 2 . 6 alkenyloxy or C 6 . I0 aryloxy. (I) CHC1 3 z 3 c- (II) Scheme I Alkenyl moieties may be in the form of straight or branched chains and, where appropriate, may be of either (E)- or (Z)-confιguration. Examples include vinyl and allyl. Aryl is phenyl or naphthyl. Therefore, in a preferred aspect of the invention the alkene derivative is a compound of formula (II): ,W (II) wherein W is C^ alkyl, C 2 . 6 alkenyl, OR 1 or NR 2 R 3 ; R 1 is hydrogen, C,. 6 alkyl, C 2.6 alkenyl, C 6 ., 0 aryl or R C(O); R 2 and R 3 are, independently, hydrogen, C,. 6 alkyl, C 2 ^ alkenyl or C 6.|0 aryl; and R 4 is C,. 6 alkyl, C 2 . 6 alkenyl, C 6 . 10 aryl, C,^ alkyloxy, C 2.6 alkenyloxy or C 6 ., 0 aryloxy. Initiation of the process of the invention is preferably achieved by irradiating the reaction mixture with light of a wavelength of from about 200 to about 600nm, more preferably 200 to 350nm, for example a wavelength of 254nm. The light may be supplied by a low, medium or high pressure mercury lamp. The reaction is preferably conducted at a temperature of about 0 to about 150°C and a temperature of from 25 to 150°C (such as 25 to 70°C) is particularly preferred. The period of the reaction may be from about 30minutes to about 24hours, depending upon the volume of reactants and the temperature used. Generally a period of from about lhour to 12hours is sufficient. Various further preferred features and embodiments of the present invention will now be described with reference to the following non-limiting example: EXAMPLE 1 This Example illustrates various preparations of 4,4,4-trichlorobutanol and the tabulated results show the increased 'yield on conversion' obtained when using the process of the invention compared to the corresponding process in the absence of an initiator. The general procedure used in each case was the same: Chloroform was degassed for lhour with nitrogen immediately prior to use. A photochemical cell fitted with a condenser was charged with chloroform, allyl alcohol and (where appropriate) an initiator. The reaction mass was then degassed with nitrogen for a further 15minutes. The vessel was covered in aluminium foil and a uv screen was fitted. The reaction mixture was heated to the stated temperature using an oil bath, whereupon irradiation was carried out for the stated period of time, using light of the stated wavelength. Analysis of the reaction mixture was carried out by GC analysis. The tables show the 'yield' of 4,4,4-trichlorobutanol (based upon the amount of allyl alcohol which was present as starting material); the 'conversion' of allyl alcohol (that is the percentage of allyl alcohol which was used up during the reaction); and the 'yield on conversion' (that is the yield of 4,4,4-trichlorobutanol when based upon the amount of allyl alcohol which was used up during the reaction): (% Yield on conversion) = (% yield of 4,4,4-trichlorobutanol) ÷ [(% conversion of allyl alcohol) ÷ 100] Yield on conversion' is an important parameter since the larger its value, the smaller is the amount of unwanted by-products obtained from the reaction. Results a) Reaction of chloroform with allyl alcohol (in the absence of an initiator). b) Reaction of chloroform with allyl alcohol (using hexachloroacetone as initiator'). c) Reaction of chloroform with allyl alcohol (using 1, 3-dichloro-h 1,3.3- tetrafluoroacetone as initiator^

Claims: CLAIMS 1. A process for the production of a trichloroalkane derivative comprising reacting an alkene derivative with chloroform, characterised in that the process is initiated by photochemical cleavage of an initiator of formula (I): z 3 c X X 0) wherein Z is chloro or fluoro; X is hydrogen, C,^ alkyl, C,. 6 haloalkyl, -O-O-C(O)-Y or -O-O-Y; and Y is hydrogen, C alkyl or C,^ haloalkyl. 2. A process according to claim 1, wherein CZ 3 is CC1 3 . 3. A process according to claim 1 or claim 2, wherein X is CC1 3 . 4. A process according to any one of claims 1 to 3, wherein the alkene derivative has a terminal double bond. 5. A process according to claim 4, wherein the alkene derivative is a compound of formula (II): ,W (ID wherein W is C w alkyl, C M alkenyl, OR 1 or NR 2 R 3 ; R' is hydrogen, C w alkyl, C 2.6 alkenyl, C 6.10 aryl or R 4 C(O); R 2 and R 3 are, independently, hydrogen, C w alkyl, C 2.6 alkenyl or C 6 . 10 aryl; and R 4 is C,. 6 alkyl, C 2 . 6 alkenyl, C 6 . 10 aryl, C,. 6 alkyloxy, C 2.6 alkenyloxy or C 6 . 10 aryloxy. 6. A process according to any one of the preceding claims which is initiated by irradiating the reaction mixture with light of a wavelength of from about 200 to about 600nm. 7. A process according to claim 6, where the light is of a wavelength of from 200 to 350nm. 8. A process according to any one of the preceding claims, which is conducted at a temperature of about 0 to about 150°C. 9. A process according to claim 8, which is conducted at a temperature of from 25 to 150°C.

Inventors: BARKS JENNY MARIE, JACKSON DAVID ANTHONY, BARKS, JENNY, MARIE, JACKSON, DAVID, ANTHONY
Applicants: BARKS JENNY MARIE, JACKSON DAVID ANTHONY, ZENECA LTD, BARKS, JENNY, MARIE, JACKSON, DAVID, ANTHONY, ZENECA LIMITED
Application year: 1999
Main classification: C07C17
IPC codes: C07C17, C07C19, C07C29