PESTICIDAL PHOSPHORODITHIOIC COMPOUNDS

Abstract: Compounds of the general formula in which R is a hydrogen atom, a methyl group or an ethyl group; R¹ is a methyl, ethyl, monochloromethyl or monobro­ momethyl group; R² is a methyl or ethyl group; or R¹ and R² together with the carbon atom to which they are attached form a cyclopropyl group; and each of R³ and R⁴ indepen­ dently is an alkyl, alkoxy, monoalkylamino or dialkylamino group, in which the or each alkyl moiety has 1 to 4 carbon atoms; provided that if R¹ represents a monochloromethyl or monobromomethyl group, then R represents a methyl or ethyl group; have useful pesticidal properties.

Description: PESTICIDAL PHOSPHORODITHIOIC COMPOUNDS The present invention to novel phosphorodithioc compounds, their preparation, their use as pesticides and pesticidal compositions containing than. Certain cyano substituted phosphoric, phosphonic and phosphinic esters are knawn broadly as pesticides. For example U.S. patents 2,908,504 and 3,706,280 and German patent 1,196,188 disclose various phosphorus compounds useful against insects and sanetimes other pests, such as mites. It has now been discovered that certain new phosphorodithioio compounds have high pesticidal activity. The present invention therefore provides a compound of the general fonrrula EMI1.1 in which R is a hydrogen atom, a methyl group or an ethyl group; R1 is a methyl, ethyl, monochloromethyl or monobromomethyl group; Rê is a methyl or ethyl group; or RÚ and Rê together with the carbon atom to which they are attached form a cyclopropyl group; and each of R d R independently is an alkyl, alkoxy, monoalkylamino or dialkylamino group, in which the or each alkyl moiety has 1 to 4 carbon atoms; provided that if RI represents a monochloromethyl or monobromoethyl group, then R represents a methyl or ethyl group. Preferably R is a methyl group. Preferably RÚ is a methyl or a monochloromethyl group, and preferably Rê is a methyl group, or RÚ and Rê together with the carbon atan to which they are attached represent a cyclopropyl group. Preferably each of R3 and R4 independently represents an group having 1 or 2 carbon atoms. Preferably both of R3 and R4 are ethoxy groups. Typical compounds of the invention are those named in the Examples herein and also the following: S-(1-(1-cyano-1-(chloromethyl)ethylthio)ethyl 0-ethyl N-isopropylphosphoramidodithioate, S-(1-(1-cyano-1-(chloromethyl)propylthio)ethyl) 0,0-diethyl phosphorodithioate, S-(1-(1-cyano-1-(bromomethyl)ethylthio)ethyl) 0-ethyl N,N-diethylphosphoramidodithioate, S-(1-(1-cyanocyclopropylthio)ethyl 0-ethyl N-isopropyl phosphoramidodithioate, S-(1-(1-cyano-1-ethylpropylthio)ethyl 0,0-diethyl phosphorodithioate, S-(1-(1-cyano-1-methylethylthio)ethyl 0-ethyl N,N-diethylphosphoramidodithioate, 0,0-diethyl S-(1-(1-cyano-1-(chloromethyl)ethylthio) propyl) phosphorodithioate, 0,0-diethyl S(1-(1-cyano-1-(bromomethyl)ethylthio) ethyl) phosphorodithioate. The invention further prides a process for the preparation of a compound according to the invention, which canprises reacting a campound of the general formula EMI2.1 with a salt of an acid of the general formula EMI3.1 in which R, R1, R , R and R4 have the meanings given for the general formula I; or, when R3 represents a C(1-4) alkoxy group or a mcno- or dialkylamino group and R4 represents a mono- or dialkylamino group, reacting a compound of the general formula EMI3.2 where R, R1 and R2 have the meanings given for the formula I and X represents a C(1-4) alkoxy group or a chlorine atan, with a compound of the formula R4H followed by alkaline hydrogen sulphide. The compounds of general formula II may be prepared by chlorination of corresponding compounds of the general formula EMI3.3 using any suitable chlorinating agent, for example N-chlorosuccinimide or sulphuryl chloride, by methods analogous to knawn methods. The compounds of the invention have useful pesticidal activity, for example against insects, mites, and nematodes. They are especially useful for the control of soil pests, including soil insects and nematodes. The invention therefore also provides a pesticidal composition which comprises as active ingredient a compound of formula I, together with a carrier. The invention also provides a method of combating pests at a locus, which comprises applying to that locus a compound of formula I or a pesticidal composition according to the invention. The compounds of the invention have unusually good larvicidal activity. For use as soil pesticides, the compounds of the invention are suitably applied to the soil at a rate of from about 0.1 to about 10kg/ha, preferably fran about 0.1 to about 5kgtha, especially fran about 0.1 to about 4kg/ha. Especially effective control results when a solid formulation is lightly mixed with the topsoil. The mixing may be preceded or immediately followed by planting seeds which germinate into plants. The compounds of the invention can also be applied as a drench, that is as a solution or dispersion of compounds of the invention. A carrier in a composition according to the invention is any material with which the active ingredient is formulated to facilitate application to the locus to be tested, which may for example be a plant, seed or soil, or to facilitate storage, transport or handling. A carrier may be a solid or a liquid, including a material which is normally gaseous but which has been compressed to form a liquid, and any of the carriers normally used in formulating agrochemical compositions may be used. Preferably oompositions according to the invention contain 0.5 to 95% by weight of active ingredient, Suitable solid carriers include natural and synthetic clays and silicates, for example natural silicas such as diatomaceous earths; magnesium silicates, for example talcs; magnesium aluminium silicates, for example attapulgites and venniculites; aluminium silicates, for example kaolinites, motomorillonites and micas; calcium carbonate; calcium sulphate; ammonium sulphate; synthetic hydrated silicon oxides and synthetic calcium or aluminium silicates; elements, for example carbon and sulphur; natural and synthetic resins, for example coumarone resins, polyvinyl chloride, and styrene polymers and copolymers; solid polychlorophenols; bitumen; waxes; and solid fertilisers, for example superphosphates. Suitable liquid carriers include water; alcohols, for example isopropanol and glycols; ketones, for example acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; ethers; aromatic or araliphatic hydrocarbons, for example benzene, toluene and xylene; petroleum fractions, for example kerosine and light mineral oils; chlorinated hydrocarkons, for example carbon tetrachloride, perchloroethylene and triChlOlAD- ethane. Mixtures of different liquids are often suitable. Agricultural compositions are often formulated and transported in a concentrated form which is subsequently diluted by the user before application. The presence of small amnurts of a carrier which is a surface-active agent facilitates this process of dilution. Thus preferably at least one carrier in a composition according to the invention is a surface-active agent. For example the composition may contain at least two carriers, at least one of which is a surface-active agent. A surface-active agent may be an emulsifying agent, a dispersing agent or a wetting agent; it may be nonionic or ionic. Examples of suitable surface-active agents include the sodium or calcium salts of polyacrylic acids and lignin sulphonic acids; the condensation of fatty acids or aliphatic gamines or asides containing at least 12 carbon arans in the molecule with ethylene oxide and/or propylene oxide; fatty acid esters of glycerol, sorbitan, sucrose or pentaerythritol; condensates of these with ethylene oxide and/or propylene oxide; condensation products of fatty alcohol or alkyl phenols, for example -octylphenol or p-octylcresol, with ethylene oxide and/or propylene oxide; sulphates or sulphonates of these condensation products; alkali or alkaline earth metal salts, preferably sodium salts, of sulphuric or sulphonic acid esters containing at least 10 carbon atoms in the molecule, for example sodium lauryl sulphate, sodium secondary alkyl sulphates, sodium salts of sulphonated castor oil, and sodium alkylaryl sulphonates such as dodecylbenzene sulphonate; and polymers of ethylene oxide and copolymers of ethylene oxide and propylene oxide. The compositions of the invention may for example be formulated as wettable powders, dusts, granules, solutions, emnlsifiable concentrates, emulsions, suspension concentrates and aerosols. Wettable powders usually contain 25, 50 or 75% w of active ingredient and usually contain in addition to solid inert carrier, 3-10% w of a dispersing agent and, where necessary, 0-10% w of stabiliser(s) and/or other additives such as penetrants or stickers. Dusts are usually formulated as a dust concentrate having a similar oaaosition to that of a wettable powder but without a dispersant, and are diluted in the field with further solid carrier to give a composition usually containing %-10% w of active ingredient. Granules are usually prepared to have a size between 10 and 100 BS mesh (1.676 - 0.152 mm), and may be manufactured by agglomeration or impregnation techniques. Generally, granules will contain h-75% w active ingredient and 0-10% w of additives such as stabilisers, surfactants, slow release modifiers and binding agents. The so-called "dry flowable powders" consist of relatively small granules having a relatively high concentration of active ingredient. Emulsifiable concentrates usually contain, in addition to a solvent and, wben neoessaay, co-solvent, 10-50% w/v active ingredient, 2-20% w/v emulsifiers and 0-20% w/v of other additives such as stabilisers, penetrants and corrosion inhibitors. Suspension conentrates are usually compounded so as to obtain a stable, non-sedimenting flowable product and usually contain 10-75% w active ingredient, 0.5-15% w of dispersing agents, 0.1-10% w of suspending agents such as protective colloids and thixotropic agents, 0-10% w of other additives such as defoamers, corrosion inhibitors, stabilisers, penetrants and stickers, and water or an organic liquid in which the active ingredient is substantially insoluble; certain organic solids or inorganic salts may be present dissolved in the formulation to assist in preventing sedimentation or as anti-freeze agents for water. Aqueous dispersions and emulsions, for example compositions obtained by diluting a wettable powder or a concentrate according to the invention with water, also lie within the scope of the invention. The said emulsions may be of the water-in-oil or of the oil-in-water type, @@ may so have a thick 'mayonnaise'-like consistency. The composition of the invention may also contain other ingredients, for example other rompounds possessing pesticidal, herbicidal, or fungicidal properties. The following Examples illustrate the invention. The NMR figures given are # values in ppm relative to tetranethylsilane in CDC13. Exemple 1 0,0-Diethyl S-(1-(1-Cyano-1-methylethylthio) ethyl) Phosphorodithioate Tb 3.6g of sodium hydride (7.2g of a 50% dispersion washed with hexane) suspended in 50ml of dimethylformamide was added a solution of 17.5g of ethyl mercapten in 5ml of dimethyl- formamide. The reaction mixture was stirred for 2Qnin at ambient temperature and then 22. 2g of 2-bromo-2-methylpropane- nitrile in lOmi of dinethylfo=iainide was added while maintaining the temperature below 23 0C. The reaction mixture was stirred at ambient temperature for 2.5 hours, allowed to stand overnight, then poured into water and extracted with hexane. The extract was dried over MgSO4, the solvent was removed and the residue was vacuum distilled to give 3.4g of 2-ethylthio-2-methylpropanenitrile, b.p. 95 C (35mm). In lOml of carbon tetrachloride were placed 1.4g of this product and 1.5g of N-chlorosuccinimide and the mixture was refluxed with stirring for four hours. Solid was filtered and the filtrate was evaporated to give 1.8g of a yellow liquid. This product was used without purification. To 15ml of acetonitrile were added successively 2.24g of 0,0-diethyl ammonium phosphorodithioate and 1.8g of the above crude 2-(1-chloroethylthio)-2-methylpropanenitrile. The reaction mixture was stirred overnight at ambient temperature, poured into water, and extracted with hexane. The hexane solution was washed with aqueous sodium bicarbonate, and then dried (MsSO4). Removal of the solvent gave 3.0g of a yellow oil, which was chromatographed over silica gel to yield 0.6g of product. NMR Analysis: 1.40, t, 6H; 2.00, m, 9H; 4.10-5.10, m, 5H. Example 2 0, 0-Diethyl S (1- (1-Cyano-1-methylpropylthio)- ethyl Phosphorodithioate In 300ml of tetrahydrofuran under nitrogen was placed 8Oml of 10% lithium diisopropylamide in hexane. me mixture was then cooled to -700C and 6.7g of 2-methylbutanenitrile was added. The reaction mixture was stirred and maintained at this temperature for 1 hour and then 9.9g of diethyldisulphide was slowly added. After 30 minutes, the reaction mixture was allowed to warm to roan temperature. Solid was filtered off and the filtrate was evaporated. The resulting residue was dissolved in ethylene chloride, washed with water, and dried over MgSO4. Solvent removal gave 6.9g of 2-ethylthio-2-methylbutanentrile, b.p. 62-65 C (0.85mm). In 150ml of dichloromethane was placed 4.3g of this product. After cooling to 100C, 4.05g of sulphuryl choride was added dropwise. The reaction mixture was stirred at roan temperature overnight. The e solvent was removed to give 5.33g of product, which was used without purification. In 50ml of dichloromethane were placed 5.59g of 0,0-diethyl hydrogen phosphorodithioate and 3.18g of sodium carbonate. This mixture was stirred at room temperature for 45 minutes and then 5.33g of the above product, 2-(1-chloroethyl- 2-methylbutanenitrile, was added. After stirring for 3 days at roam temperature, the reaction mixture was washed successively with 1M sodium bicarbonate and water, dried (MgSO4) and distilled under reduced pressure to give 6.9g of product, b.p. 135-140 C (0.5mm). NMR Analysis: 1.00-1.50, m, 12H; 1.65-2.10, m, 5H; 4.00-4.40, m, 4H; 4.40-5.00, m, 1H. Example 3 S-(1-(1-Cyano-1-(chloromethyl)ethylthio)ethyl) 0,0-Diethyl Phosphorodithioate In 150ml of dichloromethane were placed 30.5g of diethyl disulphide. After cooling to -50 to -600C, 20.0ml of sulphuryl chloride was added dropwise and then the reaction mixture was stirred at -300C for two hours Then 32.5g of methacrylonitrile was added dropwise and the reaction mixture was allowed to warm to roan temperature. The solvent was removed and the residue was distilled to give 65g of 3-chloro-2-(ethylthio)-2-methylpropanenitrile, b.p. 71.5-72.5 C (O.8mm). In 50 ml of methylene chloride were placed 16.3g of this product. This solution was cooled to 50C and 13.5g of sulphuryl chloride was added dropwise. The reaction mixture was allowed to warm to roan temperature. The solvent was removed and the residue was distilled at 670C (0.07mm) to give 13.5g of 3-chloro-2-(1-chloroethylthio)-2-methylpropanenitrile. In 25ml of nethylene chloride were placed 3.72g of O,O-diethyl phosphorodithioic acid and 1.05g of powdered sodium carbonate. The mixture was stirred for 1 hour and then 1.98g of 3-chloro-2-(1-chloroethylthio)-2-methylpropanenitrile was added. The reaction mixture was stirred for 8 hours at roan temperature and filtered. The e filtrate was dried (NaSO4) and the solvent was removed to give 3.5g of crude material, and volatiles were remaved by heating at 1300C at 0.05mm to give 2.5g of product. NMR Analysis: 1.37, t, 6H; 1.85, m, 6H; 3.80, s, 2H; 4.20-4.70, m, 5H. Examples 4 to 6 By methods analogous to those described in Examples 1 to 3, further compounds of the general formula I were prepared. Details are given in Table I. Table 1 EMI10.1 <tb> Example <SEP> In <SEP> the <SEP> General <SEP> Formula <SEP> I <SEP> NMR <SEP> Analysis <tb> <SEP> No. <SEP> R <SEP> RÚ <SEP> Rê <SEP> R <SEP> R4 <tb> <SEP> 4 <SEP> C2H5 <SEP> CH3 <SEP> CH3 <SEP> C2H5 <SEP> C2H5 <SEP> 1.05-1.65, <SEP> m, <SEP> 9H; <tb> <SEP> 1.80-2.2, <SEP> m, <SEP> 8H; <tb> <SEP> 4.05-4.98, <SEP> m, <SEP> SH. <SEP> <tb> <SEP> 5 <SEP> | <SEP> H <SEP> | <SEP> CH3 <SEP> | <SEP> CH3 <SEP> | <SEP> C2H5 <SEP> | <SEP> C2H5 <SEP> | <SEP> 1.38, <SEP> t, <SEP> 6H; <tb> <SEP> 1.70, <SEP> s, <SEP> 6H; <tb> <SEP> 1 <SEP> | <SEP> 3.90-4.00, <SEP> m, <SEP> 6H. <tb> <SEP> 6 <SEP> CH3 <SEP> -CH2CH2- <SEP> C2H5 <SEP> C2H5 <SEP> 1.08-1.71, <SEP> m, <SEP> 10H; <tb> <SEP> 1.72-1.98, <SEP> d, <SEP> 3H; <tb> <SEP> 3.95-4.95, <SEP> m, <SEP> 5H. <tb> Example 7 Pesticidal Activity Activity of the compounds of this invention with respect to insect and acarine pests was determined as follows. In each test, a solution of the test compound in a acetone containing an emulsifier, was diluted with water to give test solutions of various different dosages. I. Pea aphids (Acyrthosiphon pisum (Harris)) were tested by placing about 100 aphids on broad bean plants. The plants were sprayed with solutions of test compound and held in containers under laboratory conditions for 18 to 20 hours at which tine the living aphids in the containers were counted. II. Adult female two-spotted spider mites (Tetranychus urticae (Koch)) were tested by placing 50-75 mites on the bottom side of leaves of pinto bean plants. The leaves were sprayed with solutions of test compound and kept under laboratory conditions for about 20 hours at which time mortality counts were made. In each instance, the toxicity of the compound of the invention was compared to that of a standard pesticide (Parathion), its relative toxicity then being expressed in terms of the relationship between the amount of compound of the invention and the amount of the standard pesticide required to produce the same percentage (50) of nortality in the test insect or acarine. By assigning the standard pesticide an arbitrary rating of 100, the toxicities of the compounds of the invention were expressed in terms of toxicity indices, which compare the toxicity of the catpounds of the invention with that of the standard pesticide. That is to say, a test compound having a Toxicity Index of 50 would be half as active, while one haivng a Toxicity Index of 200 would be twice as active as the standard pesticide. The Toxicity Indices are given in Table 2. Table 2 Pesticidal activity expressed as toxicity index relative to that of parathion as a standard equal to 100 EMI11.1 <tb> <SEP> of <SEP> Example <SEP> ND. <SEP> Pea <SEP> Aphid <tb> <SEP> Spider <SEP> Mite <tb> 1 <SEP> 66 <SEP> 496 <tb> 2 <SEP> 32 <SEP> 106 <tb> 3 <SEP> | <SEP> 28 <SEP> 112 <tb> 4 <SEP> 56 <SEP> 438 <tb> 5 <SEP> 1750 <SEP> 3192 <tb> 6 <SEP> 318 <SEP> 1708 <tb> Example 8 Soil Activity The test chemical was dissolved in a solvent and thoroughly incorporated into dry soil. After venting traces of solvent, the soil moisture level was brought to 9% by adding water. Sixty grams of the maoist soil was added to a wide-mouthed jar. TWO sweet corn seeds, which had been surface sterilized in 0.2% sodium hypochlorite solution for 15 minutes and rinsed with water, were pressed into the soil perimeter of the jar. A small cavity was opened in the surface of the soil and 20 Diabrotica undecempunctata undecempunctata Mannerheim (western spotted cucneer beetle) eggs were placed in the well, and covered over with finesiieved vermiculite. The jar was then capped with a lid into which two holes had been drilled for ventilation. The jars were held under laws at 270C. After one week, the jar contents were examined for the presence of live larvae and their number was recorded. Compounds showing control at 3ppm 1 or lower in the first week were evaluated at subsequent weeks. Activity at 3ppm indicated useful soil insecticidal activity. Results of these tests were evaluated as follows: Rating larval Count 0 . 0 1 > 0 to < 3 4 2 > 3 to < 6 3 > 6 to < 10 4 > 10 Results of tests with compounds of the present invention are shown in Table 3 below. Table 3 Control of Diabrotica Undecempunctata Undecempunctata larvae in soil EMI13.1 <tb> embodiment <SEP> Dosage <SEP> Rate <SEP> WeekS <SEP> after <SEP> Treatment <tb> <SEP> (ppm) <SEP> 0 <SEP> 2 <SEP> 4 <SEP> 8 <tb> <SEP> 1 <SEP> 3.0 <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 0 <tb> <SEP> 1.0 <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 0 <tb> <SEP> 0.3 <SEP> 0 <SEP> 0 <SEP> 1 <SEP> 4 <tb> <SEP> 2 <SEP> 3.0 <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 0 <tb> <SEP> 1.0 <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 0 <tb> <SEP> 0.3 <SEP> 0 <SEP> 4 <SEP> 1 <SEP> 4 <tb> <SEP> 3 <SEP> 3.0 <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 0 <tb> <SEP> 1.0 <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 0 <tb> <SEP> 0.3 <SEP> 2 <SEP> 3 <SEP> 3 <SEP> 3 <tb> <SEP> 4 <SEP> 3.0 <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 0 <tb> <SEP> 1.0 <SEP> 0 <SEP> 0 <SEP> 1 <SEP> 3 <tb> <SEP> 0.3 <SEP> 3 <SEP> 4 <SEP> - <SEP> - <SEP> <tb> <SEP> 5 <SEP> 3.0 <SEP> 0 <SEP> 0 <SEP> 4 <SEP> - <SEP> <tb> <SEP> 1.0 <SEP> 0 <SEP> 4 <SEP> - <SEP> - <SEP> <tb> <SEP> 0.3 <SEP> 0 <SEP> 4 <SEP> - <SEP> - <SEP> <tb> <SEP> 6 <SEP> 3.0 <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 0 <tb> <SEP> 1.0 <SEP> 0 <SEP> 0 <SEP> 1 <SEP> 1 <tb> <SEP> 0.3 <SEP> 1 <SEP> 3 <SEP> 4 <SEP> - <SEP> <tb>

Claims: 1. A compound of the general formula EMI14.1 in which R is a hydrogen atom, a methyl group or an ethyl group; RÚ is a methyl, ethyl, monochloromethyl or monobromomethyl group; Rê is a methyl or ethyl group; or RÚ and Rê together with the carbon atom to which they are attached form a cyclopropyl group; and each of R and R4 independently is an alkyl, alkoxy, monoalkylamino or dialkylamino graup, in which the or each alkyl moiety has 1 to 4 carbon atoms; prodded that if R1 represents a monochloromethyl or monobromomethyl group, then R represents a methyl or ethyl group. 2. A ooupound as claimed in claim 1, in which R is a methyl group. 3. A compound as claimed in either claim 1 or claim 2, in which RÚ is a methyl or monochloromethyl group and Rê is a methyl group, or RÚ and Rê together with the carbon atom to which they are attached represent a cyclopropyl group. 4. A compound as claimed in any one of claims 1 to 3, in which each of R and R4 independently represents an alkoxy group having 1 or 2 carbon atans. 5. A process for the preparation of a compound as claimed in claim 1, which comprises reacting a compound of the general formula EMI15.1 with a salt of an acid of the general formula EMI15.2 in which R, R , R , R3 and R4 have the meanings given for the general formula I; or, when R3 represents a C(1-4) alkoxy group or a mono- or dialkylamino group and R4 represents a none- or dialkylamino group, reacting a compound of the general formula EMI15.3 where R, R1 and R2 have the meanings given for the ft=L I and represents a C(1-4) alkoxy group or a chlorine atan, with a compound of the formula R4H followed by alkaline hydrogen sulphide. 6. A pesticidal composition which comprises a oampcund as claimed in any one of claims 1 to 4 together with a carrier. 7. A oomposition as claimed in claim 6, which comprises at least two carriers, at least one of which is a surface active agent. 8. A method of combating pests at a locus, which comprises applying to that locus a compound nd as claimed in any one of claims 1 to 4, or a composition as claimed in either claim 6 or claim 7. 9. A method as claimed in claim 8, in which the locus is soil.

Inventors: SANBORN, JAMES RUSSELL
Applicants: SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 1984
Main classification: C07F9
IPC codes: A01N57, C07F9