IL33966A - O,s'-dialkyl s-hydrocarbylthioalkyl dithiophosphates and oxidized derivatives thereof,their preparation and pesticidal compositions containing them - Google Patents

Description

SO ftBSKAUtilJ At¾ G-IIBSttljiG ΟΟΗΡΑ Υ - 2 - 33966/2 Z This invention relates to novel process for preparing 0,S'-dialkyl S-hydrocarbylthioalkyl dithiophosphates, to certain new products of this process, to formulations or compositions containing these new products and to processes or methods of usin, them. More particularly, this invention relates to the preparation of 0,S' -dialkyl S-hydrocarbylthioalkyl dithiophosphates by means of a selective two-step process comprising the dealkylation of a corresponding 0,0*-dialkyl S-hydrocarbylthioalkyl dithio-phosphate or an Ο,Ο'-dialkyl-S-alkenyl dithiophosphate followed by alkylation. The particular novel products of this process have been found to be surprisingly superior pesticides to related known compounds. » 0 ,0 ' -dialkyl S-hydrocarbylthioalkyl dithiophosphates represent a commercially important cla^ss of insecticides.

Their synthesis and pesticidal action is described by Gerhard Schrader on pages 338-M-27 of his monograph, entitled "Die Ent-wicklung Neuer Insektizider Phosphors&ure-Ester", which was published by Verlag Chemie Gmbh., in Weinheim, W. Germany in 1963. Some of the isomeric 0,S' -dialkyl S-hydrocarbyl thio-alkyl dithiophosphates are also known in the prior art. For example, the synthesis of 0,S' -diethyl S-2-ethylthioethyl dl-thiophosphate has been described by Gerhard Schrader in German Patents 1,032,247 and 1, 136, 328. In these patents, 0,S-diethyl thiophosphoric acid chloride and 0,S-diethyl dithiophosphoric acid potassium salt were the respective phosphorus reactants for the syntheses. German Patent 1 , 136, 328 also describes the synthesis of an unsymmetrically substituted dialkyl ester of S-2-ethylthioethyl dithiophosphoric acid, i.e. of 0-ethyl S'-methyl S-2-ethylthioethyl dithiophosphate. A comparison of the insecticidal activity of this unsymmetrical compound with those of the corresponding 0,S' -dimethyl and 0,S' -diethyl di- 33966/2 - 3 - dithiophosphate esters were not known in the prior art. It was, however, generally assumed that higher dialkyl dithiophos-phate esters are less effective, economically useless pesti-cides.

Organic dlthiophosphates in general possess proper-ties which make them suitable as pesticides, particularly as insecticides. The importance of selected members of such di-thiophosphates, particularly of the 0,0' -dialkyl dithiophos-1 phate esters, has stimulated great interest in organic dithio-phosphate chemistry and encouraged further work toward develop-ment of novel organophosphorus compounds having desirable bio-logical activity and in methods of producing them.

In the present invention, new types of dialkyl di-thiophosphate esters, i.e., novel 0,Sh -dialkyl S-hydrocarbyl-thioalkyl dithiophosphates, are disclosed. Their synthesis via a new process involving selective dealkylation-alkylatlon is described. It is also disclosed herein that the new unsym-metrically substituted 0,S' -dialkyl dithiophosphate esters are unusually active and safe pesticides. in accordance with this invention, 0,S' -dialkyl S-hydrocarbylthioalkyl dithiophosphates are prepared from dithio-phosphate esters selected from the group consisting of S-hydro- carbylthioalkyl and S-alkenyl esters of 0,0' -dialkyl dithio-phosphoric acids. Said preparations comprise a combination of dealkylation and alkylation reactions both in the liquid phase. Most generally, this combination of reactions can be schemat- ically represented in the following manner: - wherein and pre the same or different alkyl groups? Rj^ls a hydrocarbylthioalkyl radical or an aUcenyl group; ia a hydrocsrbyl group optionally substituted with halogen, alkoxy, alkylthiOj lkylsulphonyl, cyano and/or nitro; Q is an n-substituted or eyano-and/or halo-substituted alkylene group; D is a dealkylating agent, oreferably a nitrcgen or phosphorus base or a thiiate or inorganic salt; A is an alkylation agent preferably an alkyl halide, alkyl sulfonate, dialkyl sulfate, alkyl phosphate, trialkyl phosphite or the combination of such an alkylating egent with a second alkylating agent which is a thiol.

If R* is a hydrocarbylthloalkyl radical of the formula -J-bR only one alkylating ag mt is used according to the following scheme: wherein all the symbols are as previously defined and the additional RgX symbol represents an alkylating agent such as an alkyl halide, alkyl sulfonate, alkyl phosphate, etc.

If R* is an alkenyl group of the formula -LCiI,-Jn-ClieCH-R^ wherein is a hydrogen atom or an alkyl group optionally substituted with cyano and/or halogen and n is zero, 1 or 2, a combination of two types of alkylating ents is used according to the following scheme: therein all the symbols rre as previously defined, R^SH representing an aliphatic or aromatic thiol.

Although the present process is operative independent 33966/2 - 5 - of the carbon number of the aliphatic and aromatic groups in the reactants, it is nevertheless preferred to use reactants limited in molecular weight and structure. Particularly, stringent limitations are necessary with regard to the reac-tants of the present process, if the superior novel pesticidal compositions are to be prepared.

The dithiophosphate reactants of the present process have molecular weights preferably below 800, most preferably below 400. Furthermore, it is preferred that be a to c^5 primary or secondary alkyl group. More preferably, is a C to Cg primary alkyl group. Most preferably R.^ is ethyl and methylj most specifically, R^ is ethyl.

The R' group of the phosphorus reactant can be an unsubstituted or substituted (as specified above) hydrocarbyl-thioalkyl radical -Q-S-R-j having 1 to 30 carbon atoms, i.e., having a molecular weight, preferably below 400, moet preferably below 200, or R' can be an alkenyl group -[CH2]n-CH=CH-R4 having 1 to 8 carbon atoms, i.e., having molecular weights below 100, most preferably below 60.

In case the dithiophosphate ester reactant has the general formula the preferred meaning of 1 is as previously defined. -j is preferably a C^-C^. alkyl radical, phenyl, or a Cg to Cg substituted phenyl radical, more preferably the alkyl radicals are C^ to Cg alkyl radicals, and most preferably they are C^ to C^ alkyl groups; Q is preferably a C^ to C.^subs i uted 33966/2 - 6 - Non-limiting examples of suitable 0,0' -dialkyl S- , hydrocarbylthioalkyl dithiophosphate reactants having the above the following: 4 Diethyl methylthiomethyl dithiophosphate, dihexadecy.i ethylthiopropyl dithiophosphate, diethylhexyl propylthioethyl 6 dithiophosphate, dimethyl phenylthiometh l dithiophosphate, di- 7 ethyl chlorophenylthiomethyl dithiophosphate, diethyl cyano.- 8 tolylthioethyl dithiophosphate, 'diethyl trichlorophenylthio- 9 propyl dithiophosphate, diethyl methylthio luoropropyl dithio-0 phosphate, diethyl propylthiocyanobutyl dithiophosphate, I methyl ethyl propylthiobutyl dithiophosphate, etc. 2 in case the dithiophosphate ester reactant has the 3 general formula: 6 the preferred meaning of R^ is a ¾ to C^g primary or second7 ary alkyl radical, R^ is preferably hydrogen or a ¾ to C^g 8 alkyl radical, the alkyl radical more preferably being in the 9 C;L to range. Nonllmiting examples of suitable CO^dlalkyl S-alkenyl dithiophonphnte renctants of the formula (Ila) above include the fol.lowj.np;: Dimethyl propenyl dithiophosphate, dioctyl butenyl 2 dithiophosphate, dihexadecyl octenyl dithiophosphate, diethyl hexadecenyl dithiophosphate, diethyl vinyl dithiophosphate, 4 dlpropyl pentenyl dithiophosphate, methyl ethyl hexenyl phos-5 phate, dicyclohexyl allyl dithiophosphate, diethyl cyanocrotyl i dithiophosphate, diethyl methylthiopropenyl dithiophosphate, 7 .dimethyl dimethylcarboxamidovinyl dithiophosphate, etc. 8 The dealkylating agents for the 0,0' -dialkyl dit io-9 phosphate esters are preferably selected from the following 0 groups : * (Rlf )3G R*5SM XM 33966/2 - 7 - 1 wherein R¾. is hydrogen, a Ci to C8 alkyl or monosubstituted 2 alkyl, preferably hydrogen and C]_ to C¾ alkyl, most preferably 3 methyl; G is a nitrogen or phosphorus base; is a to Cg 4 hydrocarbyl, preferably to ¾ alkyl; M is an alkali or alka- 5 line earth metal, or tetraalkyl ammoniumj X is chlorine, bro- 6 mine or iodine. 7 Nonlimiting, suitable dealkylating reagents for the 8 Ο,Ο'-dialkyl dithiophosphate esters are exemplified by the fol- 9 lowing compounds: I. Ammonia, propylamine, diethylamine, trimethyl- 11 amine, tetramethylethylenediamine, N-methyl pyrrolidine, hy- '2 droxyethylamine, benzyldimethylamlne, trlethylenediamine, tri-13 methylphosphine, trlbutylphosphlne, phosphine and other nitro- gen and phosphorus bases.

II. Sodium methanethiolate, potassium ethanethio- 16 late, potassium ethylxanthate, tetramethylammonium propane- 17 thlolate, sodium hydrogen sulfide, and other thiolate salts. 18 III. Lithium chloride, sodium iodide, calcium chlo- 1 ride, tetrabutylammonium iodide, tetrahexylphosphonium bromide, xu and similar metal and ammonium salts. 21 The dealkylation reaction of Ο,Ο'-dialkyl S-hydro-22 carbylthioalkyl dithiophosphates by nitrogen and phosphorus 23 bases is shown by the following shceme: ( +) wherein ^, ^, R^, G and Q are as previously defined. ( A similar dealkylation by thiolates is shown below: 33966/2 - 8 - If the dealk lating reagent is a salt, a trialkyl amine or a trialkylphosphine, the resulting products of dealkylation are phosphate salts of ionic character. However, in the case of not completely substituted amines and phosphines the product is partly hydrogen bonded: dialkyl dithiophosphates, in general occur in the manner scribed in our previous application, Israel 3266 .

Such reactions are a part of the present multistep proces The dealkylation of alkylthioalkyl Ο,Ο'-dialkyl di-thiophosphates also occurs selectively with the removal of an O-alkyl group. It is surprising to observe that the dealkyla-tion of 2-alkylthioethyl 0,0' -dialkyl dithiophosphates does not result in the removal of alkylthioethyl groups which are be-lieved to be stabilized in the form of the corresponding epi-sulfonium ions".

The alkylation of S-alkylthioalkyl O-alkyl dithiophos phate salts and complexes is also a highly selective process. It occurs exclusively on the sulfur atom to yield the corre- · sponding S-alkylthioalkyl 0,S' -dialkyl dithiophosphates. With metal salts, for example, the following reaction occurs: wherein is a ^ to Clo- primary or secondary alkyl group, preferably a to Cg primary alkyl group, more preferably a to Cjj, primary alkyl group, and most preferably the n-propyl groupj X is the leaving group in the alkylating process, repre- 33966/2 - 9 - phate, sulfonate, etc.

Suitable, nonlimiting examples of the alkylating agents include methyl bromide, ethyl chloride, isopropyl iodide hexadecyl chloride, methyl tosylate, trimethyl phosphite, tri- methyl phosphate, tripropyl phosphite, etc.

The net result of the dealkylation-alkylation pro- cesses from the viewpoint of the types of chemical structures involved is the isomerization of a thionothiolphosphate to a dithiolphosphate ester. In the case of the hydrocarbylthio- alkyl dithiophosphates, these processes provide the final pes- ticidal products of this invention.. Starting with unsaturated dithiophosphates, however, necessitates the use of an addi- tional process step, i.e., the addition of a thiol to the un- saturated dithiolphosphate: (III) wherein all of the above symbols are as previously defined. Examples of useful thiols are: methanethiol, hexadecanethiol propanethiol, octanethiol, benzenethiol, toluenethlol, chloro benzenethiol trichlorobenzenethiol, cyclohexanethiol, methyl- sulfonylbenzenethiol, cyanobenzenethiol, etc.

The addition of thiols to the unsaturated dithiol- phosphates can result in the attachment of the thiol sulfur a ' either of the olefinic carbons. In the case of terminally un saturated dithiolphosphates, a free radical type thiol additi ¾n results in primary sulfide derivatives, i.e., addition occur? - k ikov 33966/2 Radical type addition to vinylic dithiolphosphates, in general, occurs in a highly selective manner In contrast, radical addition to internally allylie compounds yields dithiolphosphate adducts " having sulfur substitution mainly on the unsaturated carbon closer to the phosphorus; e.g.

The unsaturated dithiophosphate reactants of the present invention can be advantageously prepared by the mono-addition of Ο, Ο'-dialkyl dithiophosphoric acids to dienes and acetylenes. The hydrocarbylthioalkyl dithiophosphate reac-tants can be prepared by displacement reactions described in the Schrader monograph quoted earlier and by selective thiol additions.

The process conditions for the dealkylation and al-kylation of unsaturated dlthiophosphates are described in our above-mentioned earlier application. The dealkylation and al-kylation of hydrocarbylthioalkyl dlthiophosphates can be car-ried out in a similar manner.

For the dealkylation, preferably equimolar reactants are used. However, an excess of the base reactant may be em-ployed with advantage. The dealkylation can be carried out with or without solvent. The use of a solvent is, however, usually preferred. The utilization of strongly polar, neutral organic solvents such as acetonitrile, ethanol, and acetone is particularly advantageous. 33966/2 - 11 - , about +150°C, preferably from about 25 to about 120°C. The 2 pressure employed is usually atmospheric. In the case of vola- 3 tile dealkylating agents, however, superatmospheric pressures 4 up to 50 atmospheres can be used to keep the reactants in the liquid reaction phase. 6 The dealkylation reaction is carried out for a time 7 sufficient to substantially convert the starting dithiophos- 8 phate ester to the corresponding salt. Reaction times ranging 9 from 1 to 100 hours are common, periods ranging from 3 to 24 hours are preferred. Unduly prolonged reaction time, too sel l vere conditions and excess dealkylating agent may result in 12 undesirable double dealkylation. After the dealkylation, the 13 excess dealkylating agent is removed since it usually inter- 14 feres with the formation of neutral phosphate esters in the subsequent alkylation stage. 16 In the alkylation process, the use of equimolar re- 17 actants is again preferred. Especially, in the case of amine- 18 and phosphine- dithiophosphate complexes, additional amounts 19 of the alkylating agent can be used to react with the base 0 component of the complex: 26 The alkylation can be carried out with or without a 27 solvent. It is usually advantageous to use a solvent. The 28 preferred solvents are polar organic compounds such as ni- 29 triles, ketones, alcohols, etc. Hydrocarbons and their chlo- 30 rinated derivatives such as xylene, chlorobenzene , etc., a,re 31 also suitable. An excess of the alkyl halide reactant can be 33966/2 The alkylating temperatures can vary from about 0 to 150° , preferably from about 25 to about 120°C The temperature of the reaction mixture can be brought up to a point where the alkylation occurs at an advantageous rate. It is often pref-erable, however, to heat up one reactant to the desired reac-tion temperature and then to add the other.

The pressure of the alkyla ions is usually atmos-pheric. In the case of volatile alk l halide reactants, how-ever, the use of superatmospheric pressures can be preferable in order to keep them in the liquid reaction phase. Pressures up to about 50 atmospheres can be used.

Besides a possible change of elemental composition, dealkylation followed by alkylation leads, to a structural isom-erization of the phosphate ester. The combination of the two processes, for the isomerization of S-alkenyl Ο,Ο'-dialkyl thionothiolphosphates to the corresponding 0,S' -dithiolphos-phates is described in our above-mentioned earlier application. Other olefinic'ally unsaturated thionothiolphosphates can be isomerized in a similar manner. For the synthesis of the pes-ticidal hydrocarbylthloalkyl 0,S'-dialkyl dithiophosphates of the present invention, such an isomerization is followed by thiol addition. Starting with hydrocarbylthloalkyl Ο,Ο'-dial-kyi dithiophosphates, isomerization can provide the desired compositions in one step, by combining the following reactions: 33966/2 - 13 - wherein = R2« Such an isomerization reaction can be carried out catalytically since either the metal or the tetraalkyl am-monium or the tetraalkyl phosphonium halide salt is regener-ated.

The amount of the salt catalysts is from 0.5 to 20$, preferably from 1 to $· The temperature and pressure limits are the same as in the stepwise alkylation and dealkylation processes. It is important, however, to use a solvent in which the catalyst is soluble under the reaction conditions. Such solvents include ether alcohols such as ethoxyethanol. The use of higher temperatures between about 60° and about l40°C and superatmospheric pressures up to 50 atmospheres is preferred to achieve practical conversion rates with a small amount of the salt reactant, i.e., catalyst.

The S-organothioalkyl 0,S|-dlalkyl dithiophosphate products of the present invention can be readily oxidized to the corresponding sulfoxides and sulfones: It is preferred to use chemical pxidants such as peroxides, particularly aqueous hydrogen peroxide, for these oxidations. Other suitable oxidants include nitric acid, per- manganates, bromine, etc. The oxidations occur under condi- tions known for similar reactions of simple sulfides. Acetic acid and acetic anhydride can be used with advantage for hydro- gen peroxide oxidation because their application leads to the 33966/5 14 - The first oxidation step yielding the sulfoxide compound is relatively fast. Consequently, the sulfoxide can be readily produced under mild conditions without the concurrent formation of significant amounts of the sulfone. Using peroxide, the sulfoxide is preferably prepared at temperatures between about 0 and 40°C. For the preparation of the sulfone, temperatures preferably between 25° and 80°C. are used* The oxidation of S-alkylthioalkyl 0,S'-dialkyl di- thiophosphates can be advantageous with respect to their pes- ticidal use since the sulfoxide and sulfone derivatives are ordinarily expected to be more stable towards hydrolysis as described in the earlier quoted Schrader monograph, Schrader also describes that there is evidence that such oxidation also occurs in plants and animals and leads to highly active, systemic insecticides.

The new products of the process claimed in the present invention are O-methyl or .-ethyl S'-propyl or-«butyl hydrocarbylthioalkyl dithiophosphates. The new compounds are represented by the following general formula: wherein: R' is a methyl or ethyl group; R' is an alkyl group having \ three or four carbon atoms, e.g., n-propyl and secondary butyl; is a to C10 alkyl group, n phenyl group or a mono- or poly-halo-substituted phenyl group; Q* is a to alkylene group; ond is 0, 1 or 2; provided that when Q' is methylene, y is 0, and thnt when Q' is ethylene, R is a primary or secondary to alkyl.

In particular ^ may be preferably a CL to CQ alkyl, phenyl or chlorinated phenyl, most preferably C. to 0. alkyl, 4-chlorophenyl. 33966/5 - 15 The preferred compounds of the present invention include those having the following general etruoturea: wherein j is 1 to 4· wherein R is primary or secondary to C4 alkyl and X is a hydrogen or halogen atom, preferably a chlorine atom. wherein k is 1 to 4, provided that when k is 1, y is 0 and that when k is 2, g is primary o eeoondary Oj to alkyl* wherein R' ie primary or eeoondary to alkyl and x is 1 or 2. 33966/3 - 15a - wherein R£ ie primary or secondary to alkyl. wherein Rg is primary or secondary to alkyl, provided •that when ie 0, R ie -C-j to alkyl. wherein x is 1 or 2. (m) wherein j is 1 to 3; k ie 1 or 2, and y ie 0 to 2, provided thai when k ie 1, y is 0. 33966/2 ; - 16 - I j j Non-limiting examples of the S-hydrocarbylthioalkyl 0,S ' -dialkyl dithiophosphate compounds also include, e.g.: Mejthylthiomethyl O-methyl S' -propyl dithiophosphate, methylthioethyl O-ethyl S' -propyl dithiophosphate, ethylthioethyl O-ethyl S' -propyl dithiophosphate, methylthiopropyl O-ethyl S' -propyl dithiophosphate, ethylthiopropyl O-ethyl S1 -propyl dithiophosphate, propylthiopropyl O-ethyl S1 -propyl dithiophosphate, methylthiobutyl O-ethyl S' -propyl dithiophosphate, p-Jchlorophenylthiomethyl O-ethyl S' -propyl dithiophosphate xylylthiomethyl O-ethyl S' -butyl dithiophosphate, trichlorophenylthiomethyl O-ethyl S1 -propyl dithiophosphate, mejthylsulfonylphenylthiomethyl O-ethyl S' -propyl dithiophosphate, ethylsulfonylethyl O-ethyl S' -propyl dithiophosphate, ethylsulfonylpropyl O-ethyl S1 -butyl dithiophosphate, ethylsulfonylbutyl O-ethyl S1 -propyl dithiophosphate, and p-chlorophenylsulfonyl ethyl O-ethyl S' -propyl dithiophosphate.

Although the above compounds are believed to be all novel and can be prepared by the process of this invention, they have widely different properties with respect to pesticidal activity. For economical pesticidal uses, certain novel com- I positions are preferred, although in general all possess some measure of pesticidal activity.

The novel S-hydrocarbylthioalkyl O-alkyl ε'-ζθ^ to alkyl) dithiophosphate pesticides preferably have a molecular weight of less than 800, more preferably less than 400. For high activity, the O-alkyl group should be methyl 33966 /3 wherein R is methyl or ethyl, preferably ethyl; R is alkyl, preferably n-propyl J y is 0-2, preferably 0; R is 0χ to C_, alkyl, phenyl or mono- or poly-halo-substituted phenyl containing 6 to 8 carbon ntorna; rind Q' io a to alkylene group, j Although many of the preferred pesticidal dlthio- phosphates of the present invention have the well known lower 0-alkoxy and S-hydrocarbylthioalkyl esterifying groups, their Cg to S' -alkyl group is believed to be novel. Most specifically these unsymmetrical compositions exhibit the presence of S-n-propyl or S-prlmary-i-butyl groups. Unexpectedly, these groups contribute very desirable, superior pesticidal properties to these pesticidal compositions, whereas similar known unsymmetrical 0,S*-dialkyl esters having S-methyl or S-ethyl groups, show an insecticidal activity markedly inferior to that of the corresponding symmetrical esters.

/ Among the desirable pesticidal properties, the a.c-tivity of the novel compositions against the army worm is par-ticularly outstanding. In view of the very high resistance of the army worm against most of the known pest control chemicals, this activity is very important.

It is similarly unexpected and important that the novel compositions have low toxicities against warm blooded animals and are therefore safe to use. The appearance of the low toxicity is again specifically associated with the presence of the S-n-propyl or S-primary isobutyl groups in these mole-cules. This low toxicity coupled with high pesticidal activ-ity, i.e., high therapeutical index, is essential for animal health applications.

As previously noted, the esters of this invention are useful as pesticides, particularly as insecticides. When used as insecticides, they are preferably formulated with a suitable carrier or diluent or combinations thereof such as those described in our above-mentioned earlier application.

The present invention Is further illustrated in greater detail by the following examples.

Synthesis of S-Hydrocarbylthioalkyl 0,S'-Dialkyl Dithiophosphates from their Ο,Ο'-Dialkyl Isomers Example 1 0,S-Diethyl S 1 -2-Ethylthiopropyl Dithiophosphate 0,0' -Diethyl S-l- (2-ethylthiopropyl) dithiophosphat (11.6 g., 0.04 mole) and 4.5 g. (0.04 mole) of l,4-diaz4picyclo [2.2.2] octane, i.e., triethylenediamine, were stirred at am-bient temperature for 24 hours. The resultant viscous liquid Was dissolved in 100 ml. of acetonitrile and 8.7 g- (0.08 mole) of bromoethane were added. The solution was heated to 70°C in 50 ml. of water. The water phase then was separated and washed with 250 ml. of ether. The combined organic layers were washed with 50 ml. of 5 aqueous NaEKX^, dried over an-hydrous MgSO^, and the solvent removed under vacuum under pres-sures down to 0.1 mm Hg. The liquid residue weighed 8.7 g« (δ7# pure by gas liquid chromatography, i.e., glc).

Analyses. Calculated for C^I^O PS^: C, 37 -47; H, 7 - 28; P, IO.77. Found: C, 37 - 28; H, 7 - 20; P, 10. 56.

Example 2 0,Ethyl-S-l-Propyl S 1 -2-Ethylthioethyl Dithiophosphate According to the procedure of Example 1, 27 -4 g. ( 0. 1 mole) of 0, 0 ' -diethyl S-l- (2-ethylthioethyl) dithiophos-phate, 11.2 g. (0.1 mole) of triethylene diamine and 12.3 g. (0.1 mole) of 1-bromopropane were reacted to give 16.0 g. of a 79$ pure product by glc.

Analyses. Calculated for C9H21O2PS3 : C, 37 ·47; H, 7.28 p, IO.77. Found: c, 36.92 ; H, 7 - 27; P, 10.61.

Example 3 0-Ethyl S-l-Propyl S ' -Ethylthiomethyl Dithiophosphate According to the procedure of Example 1, 26.0 g. (0 .1 mole) of 0,0 ' -diethyl S-ethylthiomethyl dithiophosphate, 11.2 g. (0. 1 mole) of triethylenediamine and 24.6 g. (0.2 mole) of 1-bromopropane were reacted to give 10.0 g. of a residual product whose structure was confirmed by nuclear magnetic resonance spectroscopy (nmr) .

Analyses. Calculated for C^H-j^^PS^: C, 35 - 03; H, 6 - 92 ; P, II.3I . Found; C, 36.09; H, 6.92; P, 11. .

Example 4 0-Ethyl S-l-Propyl S' -4 Chlorophenylthiomethyl Dithiophosphate According to the procedure of Example 1, 68. 5 g- (0.4 mole) of 1-bromopropane were reacted to give 52 g. of a residual product whose structure was confirmed by nmr.

Analyses. Calculated for : C, 40.41; H, 5.05; P, 8. 69 - Found: C, 40.23 ; H, 5 - 12 ; P, 8.49.

Example 5 O-Hexadecyl S-Dodecylthio S ' -4-Octylthiobutyl Dithiophosphate 0, 01 -Dihexadecyl S-4-octylthiobutyl dithiophosphate is reacted with a 10 mole excess of trimeth lamine at 70° C. in a closed, effectively stirred pressure vessel to yield sub-stantially pure 0-hexadecyl S-4-octylthiobutyl dithiophosphoric acid hexadecyl trimethyl ammonium salt. After the removal of the excess trimethylamine, the salt is reacted with dodecyl bromide to give the desired product, whose structure can be confirmed by nmr.

Synthesis of S-Hydrocarbylthioalkyl 0,S'-Dialkyl Dithiophosphates from S-Olefinic Dithiophosphates As was disclosed earlier in the specification, this method of synthesis involves (1) the dealkylation of S-olefinic Ο,Ο'-dialkyl dithiophosphates, (2) the reaction of the result-ing salts with alkylating agents to yield the corresponding S'-olefinic 0,S-dialkyl dithiophosphates, and ( 3) the reaction of the latter with thiols to yield the desired compositions of this invention.

Several examples for steps ( 1) and (2) of this syn-thetic approach were given in our above-mentioned earlier ap-plication. The following examples 6-20 are set forth essen-tially to illustrate the carrying out of foregoing step ( 3) · Example 6 - Preparation of 0-Ethyl S-l-Propyl S' -2-Methylthio- propyl Dithiophosphate A quartz tube was charged with 48.0 g. (0.2 mole) of isopropanol bath and l8.1 g. (0 .37 mole) of methanthlol were added. The tube was sealed and irradiated in a water bath with ultraviolet (UV) radiation from three 100 Watt Hanau immersion lamps at 15° from a distance of 6 cm. After 24 hours, the re-action was complete, as determined by gas chromatography (glc), and the excess methanethiol was removed under vacuum (0 .1 mm). The residue was dissolved in 500 ml. of ether and washed with 50 ml. of 5 aqueous sodium bicarbonate. The ether solution was dried over anhydrous magnesium sulfate, and the solvent was removed under reduced pressure. The yield of 0-ethyl S-l-propyl S ' -l- ( 2-methylthiopropyl) dithiophosphate was 53 · 7 g-( 85 pure by glc). The boiling point of the product was 127-129°C at 0.08 mm Hg.

Analyses. Calculated for C9H21O2PS3: C, 37.^7; H, 7 - 28 ; P, IO. 77. Found: C, 37- 53; H, 7 - 28 P, 11.3 .

Example 7 0-Ethyl S-l-Propyl S' -2-Ethylthiopropyl Dithiophosphate This compound was prepared from 48.0 g. (0.2 mole) of 0-ethyl S-l-propyl S'-propenyl dithiophosphate and 21.0 g. (O. 33 mole) of ethanethiol under UV radiation according to the procedure of Example 6. The yield was 58.0 g. ( 82$ pure by glc). The boiling point of product was 128-129°C at 0.17 mm Hg.

Analyses. Calculated for C^i^C-gPS-^ : C, 39 « 76; H, 7 * 68; P, IO.27. Pound: C, 39- 1; H, 8.01; P, 9 - 73 · Example 8 0-Ethyl S-l-Propyl S ' -2-n-Propylthi0propyl Dithiophosphate This compound was prepared from 48.0 g. (0.2 mole) of 0-ethyl S-l-propyl S'-propenyl dithiophosphate and 23 .3 g-(0 . 3 mole) of i-propanethiol under UV radiation according to Analyses. Calculated for C-j^Hg^OgPS^ : C, 41.77; H, 7.89; P, 9-81. Found: G, 41.96; H, 7·75; P, 9- 7· Example 9 O-Ethyl S-l-Propyl S-2-i-Propylthiopropyl Dithlophosphate O-Ethyl S-l-propyl S'-propenyl dithiophosphate (24.0 g., 0.1 mole) and 11.4 g. (0.15 mole) 1-propanethiol were re-acted according to the procedure of Example 6 to give 16.0 g. of product (50$ yield).

Analyses. Calculated for C11H2502PS3: C, 41.77; H, 7-89; P, 9-81. Found: C, 42.18; H, 7-84; P, 9-35-Example 10 0-Ethyl S-l-Propyl S 1 -2-n-Hexylthiopropyl Dithiophosphate 0-Ethyl S-l-propyl S'-propenyl dithiophosphate (24.0 g*> 0.1 mole) and 17· 5 g* (.0.15 mole) 1-hexanethiol were reac-ted according to the procedure of Example 6 to give 3 .7 g« of a residual product whose structure was confirmed by nmr.

Analyses. Calculated for C^H-^-^PS^ : C, 46.77; H, 9-14; P, 8.69- Found: C, 49.53; H, 8.66; P, 7-40.

Example 11 0-Ethyl S-2-Methylpropyl S' -2-Methylthiopropyl Dithiophosphate This compound was prepared by reacting ·θ8 g. (0.02 mole) of 0-ethyl S-l-(2-methylpropyl) S'-propenyl dithiophos-phate and excess methanethiol according to Example 6 to give 2.6 g. of a residual product, whose structure was confirmed by nmr.

Analyses. Calculated for 010Η23θ2Ρ33 : C, 39·76; H, 7-68; P, IO.27. Found: C, 38.22; H, 6-95; P, 10.28.

Example 12 0-Ethyl S-l-Propyl S ' -2-Methylthiobutyl Dithiophosphate This compound was prepared by reacting 8.6 g. (0.034 give 5·6 g. of a residual product whose structure was confirmed by nmr.

Analyses. Calculated for C^I^O PS^: C, 39 «76; H, 7-68; P, 10.27- Pound: C, 39·72; H, 7.6Ο; P, 9.75-Example 13 - O-Ethyl S-l-Propyl S'-2-Meth lthio-3j3-dimethyl- butyl Dithlophosphate This compound was prepared by reacting 6-9 g* (0.025 mole) of 0-ethyl S-l-propyl S1 -l-(3,3-dimethyl-butenyl) dithio-phosphate and excess methane thiol according to the procedure of Example 6 to give -3 g. of a liquid residual product whose structure was confirmed by nmr.

Analyses. Calculated for C12H27°2PS3: c* ^3· 90; H, 8.23; P, 9. 5. Found: C, 44.79; H, 7-49; P, 7-25· Example 14 O-Methyl S-l-Propyl S '— 2-Methylthiopropyl Dithiophosphate O-Methyl S-l-propyl S'-propenyl dithiophosphate (2.26 g., 0.01 mole) and excess methanethiol were reacted according to the procedure of Example 6 to give 2.0 g. of a residual product whose structure was confirmed by nmr.

Analyses. Calculated for CgH^OgPS^: C, 35-25; H, 6.9½. Found: C, 31.15; H, 6.4l.

Example 15 O-Ethyl S-l-Butyl S' -2-Methylthiopropyl Dithiophosphate 0-Ethyl S-l-butyl S'-propenyl dithiophosphate (7«62 g.^ 0.03 mole) and excess methanethiol were reacted according to the procedure of Example 6 to give 6.2 g. of a liquid resid-ual product whose structure was confirmed by nmr.

Analyses. Calculated for C10H2302PS3: C, 39*76; H, 7.68; P, IO.27. Found: C, 40.53; H, 7-58; P, 9-50.

Example l6 g., O.03 mole) and excess methanethiol were reacted according to the procedure of Example 6 to give 6.0 g. of a residual product whose structure of compound was confirmed by nmr.

Analyses. Calculated for C, 37. 7; H, 7.28. Found: C, 36-61; H, 7.Ο3.

Example 17 0,S-n-Dipropyl S ' -2-Methylthiopropyl Dithiophosphate 0, -S-Dipropyl S'-propenyl dithiophosphate (10.0 g., O.039 mole) and excess methanethiol were reacted according to the procedure of Example 6 to give 10.1 g. of 84$ pure product (72$ yield). | Analyses. Calculated for C10¾3°2I>S3: c* 39·76; H, 7-68; P, IO.27. Pound: C, 39·99; H, 7.75] P, 10.28.

Example l8 - 0-Octyl S-Hexadecyl S' -2-Trichlorophenylthiohexyl Dithiophosphate Ο,Ο'-Dioctyl S-hexenyl dithiophosphate is dealkylated at 80°C, with trimethylamine to yield O-octyl S-hexenyl di-thiophosphoric acid octyltrimethyl ammonium salt. The latter compound is alkylated with hexadecyl chloride also at 80° to give 0-octyl S-hexadecyl S'-hexenyl dithiophosphate. Subse-quent addition of trichlorobenzenethiol with UV initiation pro- \ vides the desired final product, whose structure can be con-firmed by nmr.

Example 19 0-Methyl S-Octyl S-2-Hexadecylthiobutyl Dithiophosphate 0,0-Dimethyl S-crotyl dithiophosphate is dealkylated with ammonia, and the resulting 0-methyl S'-crotyl dithiophos-phoric acid methylammonium salt is reacted with octyl chloride to yield 0-methyl S-octyl S'-crotyl dithiophosphate. Biz-azobutyronitrile catalyzed addition of hexadecanethiol to the nating. The structure of these isomers can be confirmed by nmr .

Example 20 0-Ethyl S-n-Propyl S' -3-n-Propylthiopropyl Dithiophosphate 0-Ethyl S-n-propyl S' -allyldithiophosphate is reacted with a ten molar excess of n-propanethiol under the effect of UY at 15°· The progress of the reaction is estimated by nmr spectroscopy. After the reaction is substantially complete the excess thiol is stripped in vacuo. The liquid residual product is mostly the desired dithiolphosphate ester.

General Experimental Procedure for Biological Testing of S-Hydrocarbylthioalkyl 0,S'-Dialkyl Dithiophosphates In Examples 21-26 which follow, the new dithiophosphate compositions of the present invention were tested in the greenhouse and in the laboratory to determine their biological activity. Structurally related, known compounds, usually leading commercial compounds, were also tested side-by-side to determine the relative pesticidal effectiveness of the new compounds .

In the insecticidal and miticidal tests, the experimental compounds were tested as aqueous emulsions. These emulsions were prepared by dissolving the compound in acetone and dispersing it in distilled water with Triton X-100, an alkyl-aryl polyether alcohol derived by the reaction of i-octylphenol with ethylene oxide, to give spray emulsions containing the desired concentrations of the compound. These emulsions were then used in standard laboratory tests described below.

Mexican Bean Beetle: Bean leaves were dipped in the emulsion of the test chemical and allowed to dry. Individual treated leaves were placed in Petri dishes and four Mexican bean beetle ■V Southern Army Worm; Bean leaves were dipped in a formulation of the test chemical and allowed to dry. Individual treated leaves were placed in Petri dishes and four Southern Army Worm larvae introduced into each of two replicate dishes.

Mites, Contact: Potted bean plants infested with the two-spotted spider mite were placed on a turntable and sprayed with a formulation of the test chemical. The plants were held for five days and the degree of mite control was rated after two days.

Mites, Systemic; Bean plants infested with the two-spotted mites were treated by applying 20 ml. of the formulated test chemical to the soil.

Aphid, Contact; Potted nasturtium plants infested with the bean aphids were placed on a turntable and sprayed with a for-mulation of the test chemical. The plants were held for two days and the degree of aphid control was rated.

Aphid, Systemic; Nasturtium plants infested with the bean aphid were treated by applying 20 ml. of the formulated test chemical to the soil. The degree of aphid control was rated after two days.

House ly ; Caged houseflies are sprayed with the formulated test chemical. After two days the degree of housefly control was rated.

Corn Root Worm; This test was done in the soil with larvae 7-10 days old in the following manner. 75 ml. ( 90-100 grams) of an air dried soil-sand (2 : 1) mixture was placed in an 8-ounce plasticized cup. 10 ml. of a 55 ppm. stock equivalent to 5 ppm. in soil or 10 pounds in a 6-inch deep acre, was pipetted onto the surface of the soil. The cup was capped and one hour later it was shaken vigorously 30 times. The cap was Root-knot Nematode; An air-dried 2:1 soil-rsand mixture (125 ml.) in an 8-ounce plasticized container was infested with a ; stock of root-knot nematode prepared 7-10 days previously (at the rate of 6-7 grams of chopped galls per gallon of soil) . Ten ml. of the formulated test chemical at 231 ppm. was poured onto the surface of the soil-sand mixture to give a rate equivalent to 25 pounds per 6 inch acre. The container was then capped and shaken vigorously one hour latei The con- tainer was kept for 5-7 days, then shaken again, and seeded with four cucumber seeds by placing the seeds on the surface ; and covering with 1/2 inch of sand. After 3-4 weeks the roots were examined for galls and the degree of control determined. Cholinesterase Inhibition To a solution of 0.2 unit of bovine cholinesterase in 2.97 ml. of a buffer solution containing 11.15 grams of dl- sodium hydrogen phosphate dodecahydrate and 1.8l grams of po- tassium dihydrogen phosphate per liter of water, 0.03 ml. of a solution of the test chemical in acetone was added. This mix- ture was then incubated in a water bath at 35°C. for 30 minutes one ml. of a solution containing 100 milligrams of 5,5'-dithio- bis-(2-nitrobenzoic acid), 100 milligrams of acetylthiocholine iodide, and 75 ml. of the above buffer solution in sufficient water to make 200 ml. was then added and the mixture again in- cubated in a water bath at 35°C. for 30 minutes more. The amount of inhibition of bovine cholinesterase was then deter- mined from the absorbance of this solution at 420 m^(mili- micron) . By using a series of solutions of the test chemical at various concentrations in acetone, the concentration needed for 50$ inhibition was determined.

The insecticidal effectiveness of organophosphorus to estimate the insecticidal potential of new organophosphorus compounds.

Fungicidal Tests Bean Powdery Mildew; Eradicant Test in these tests, the experimental compounds were tested as aqueous emulsions, prepared in the same manner as was previously described above with respect to the insecticidal and miticidal tests.

Bean plants with fully expanded primary leaves were inoculated with spores of the powdery mildew fungus (Erysiphe polygoni) . Emulsions of the experimental chemicals were then sprayed on the plants placed on a revolving turntable. The plants were then kept in a greenhouse for 7 to 10 days. The amounts of the mildew on their primary leaves were then rated. Bean Rust: Eradicant Test Pinto bean plants with fully expanded primary leaves were inoculated with spores of the bean rust fungus (Uromyces phaseoli) and incubated for 24 hours. The tests were then car-ried out as described above for Bean Powdery Mildew.

Bean Rust: Systemic Eradicant Test Pinto bean plants were inoculated 24 hours prior to use as above and the soil in the pot was then treated with 20 ml. of an emulsion of the test chemical. The rest of the test and the evaluation were then carried out as above for Bean Powdery Mildew.

Sclerotium: Soil Fungicide Test Sterilized soil was inoculated with Sclerotium and placed into a 4-ounce "Dixie Cup", and drenched with 20 ml. of an emulsion of the test chemical. The cup was then incubated for two days at 70°F. Thereafter, the amount of mycelial 1 Example 21 2 The Effect of the Introduction of S-n-Propyl Group into Commercial 0,0' -Diethyl S-Hydrocarbylthioalkyl 3 Dithiophosphate Pesticides 4 A number of leading commercial 0,0' -diethyl S-hydro- 5 carbylthioalkyl dithiophosphate pesticides were converted to 6 the corresponding 0-ethyl S-n-propyl S' -hydrocarbylthioalkyl 7 dithiophosphates using the present process as described in 8 Examples 2-4. The pesticidal activity of the starting commer- 9 cial compounds was then compared with that of the corresponding •JO OjS-isomers in order to determine the effect of the introduc- H tion of the S-n-propyl group. The data resulting are given in 12 Table I below. 13 The data show that the present process resulted in 14 superior pesticides. The increase of activity on isomerization is believed particularly apparent in the case of the Southern 16 army worm. The increased pesticidal activity, in general, is 17 believed to be apparently related to the increased effective- 18 ness of the isomeric compounds as cholinesterase inhibitors. 19 An increase of the pesticidal activity is considered to be very surprising since a change from the ethyl to the 21 propyl esters of thio- and dithiophosphorus acids is usually 22 accompanied by a decrease of their effectiveness, as discussed 23 in the Schrader monograph previously mentioned on page 1. 24 Example 22 - The Effect of S-Ethyl Versus S-n-Propyl Group on the Pesticidal Activity 26 The 0,S'-dialkyl S-2-alkylthiopropyl dithiophosphates 27 were selected for a study of correlations between chemical 28 structure and biological activity. 29 in Table II below, the effect of S-ethyl versus the s-n-propyl group is shown on the insecticidal, miticidal and TABLE I 2 Effect of the Introduction of the S-Propyl Group 3 Commercial 0,0-Diethyl S-Hydrocarbylthioalkyl Pest 18 ( C2H50) 2P(S)SCH2CH2SC2H5 50 50 30 100 19 (Disyston) ( C2H50)2P(S) SCH2CH2SC2H5 100 100 90 90 26 (Thimet) 100 100 100 100 TABLE 1 (Continued) 2 (Trithion) a I - Spray concentration 50 ppm. > TABLE II 2 The Effect of the S-Ethyl versus the S-n-Propy 3 on the Pesticidal Activity of O-Ethyl S-2-Ethy 4 Propyl Dithlophosphate Esters Pest Control, $ Experimental 11 Compound Routine Insecticidal and Miticidal Tests 12 Example Cone . S.Army Mex.Bean Spider Mites Bean Aphi 13 - No. R" ppm Worm Beetle Contact Systemic Contact Sys 14 1 C2H5 250 0 50 90 50 80 50 0 0 0 0 0 16 7 n-C3H7 250 100 100 100 100 100 1 17 50 100 100 100 100 100 1 S-n-propyl compound is an effective insecticide at 50 ppm 2 while the S-ethyl compound shows no activity at this concen- 3 tration. 4 Table III shows the fungicidal activity of the same two compounds. The data show that the S-n-propyl compound is 6 again active at concentrations where the S-ethyl compound j shows no sign of activity . 8 Example 23 - The Effect of the Structure of the Higher 9 S-Alkyl Groups on the Pesticidal Activity After finding that the substitution of the 0-ethyl H by the S-n-propyl group increases pesticidal activity, the ef- 12 feet of other higher S-alkyl groups was examined. The results 13 are shown in Table IV. 1 The results show that all the C^-C^ S-alkyl com- 15 pounds have superior pesticidal activity to the known C-^-C 16 S-alkyl compounds. The activity of the S-n-propyl compound 17 was found to be the best, followed, in decreasing order of 18 activity, by the S-primary isobutyl, the S-i-propyl and the 19 S-n-butyl compounds. 0 Example 24 - Effect of the Structure of the O-Alkyl 21 Groups on the Pesticidal Activity 2 The effect of the 0-alkyl groups was studied on the 3 S-n-propyl S-methylthiopropyl dithiophosphate esters. The 4 data are shown in Table V below. They indicate that the pres- 5 ence of the 0-ethyl group leads to the best overall activity. 6 Although the systemic effectiveness of the O-methyl derivative 7 is better because of its higher polarity, its general contact 8 activity is lower. The 0-n-propyl derivative shows the least 9 activity both as a contact and as a systemic pesticide.

TABLE III The Effect of the S-Ethyl versus the S-n-Propyl Gro the Fungicidal Activity of O-Ethyl S-2-Ethylthiopr Dithiophosphate Esters Control of Foliar Fungi (After Days) „ (at Experimental Compound Bean Mildew Bean Rust Bean Rust Example No. R" Eradicant Eradicant Erad 0 0 C2H5 7 η^Ηγ 70 80 9 TABLE IV 2 The Effect of the Structure of the Higher S-Alkyl 3 Activity of 0-Ethyl S-Alkyl S 1 -2-Methylthiopropy 4 Phosphate Pesticides 9 Experimental Compound Mortality Produced, 0 Example Cone. S. Arm Mex. Bean Spider Mites 1 No . R ppm Worm Beetle Contact Systemic C 3 50 100 100 100 100 (CH3)2CH 250 100 100 100 100 50 100 100 0 6 15 CH3CH2CH2CH2 250 100 100 100 7 50 8o 100 0 8 11 2CHCH2 250 80 100 100 100 9 50 0 100 6o 100 TABLE V The Effect of the Structure of O-Alkyl Groups on the Pe of O-Alkyl S-n-Propyl S-2-Methylthiopropyl Dithio Experimental Compound Mortality Prod Example Cone S . Army Mex. Bean No. R' Worm Beetle 14 Cft. 250 100 100 100 100 50 100 100 CH CHg 250 100 100 100 100 50 100 100 100 100 17 CH3CH2CH2 250 100 100 100 50 8o 50 0 Example 25 - Effect of the Structure of the S-Alkyl Group of the Thioether Moiety on the Pesticldal Activity The effect of the structure of the S-alkyl thio-ether group was examined on the S-2-alkylthiopropyl esters of O-ethyl S'-n-propyl dithiophosphoric acid esters having opti-mized 0,S'-dialkyl groups.

The data included in Table VT below show that the S-methyl, -ethyl and n-propyl derivatives all have about the same pesticldal activity. Higher S-alkyl derivatives such as the S-n-hexyl compound, however, show a decreased level of activity. Overall, the activity is less sensitive to the alkyl variation in the thioether than in the phosphorus ester groups of the molecule .

The oxidation of the thioether group to the corres-ponding sulfoxide and sulfone group has also relatively little effect on the activity.

Example 26 - Effect of the Structure of the Alkylene Group on the Pesticldal Activity Known, commercial S-hydrocarbylthioalkyl 0, 0'-dialkyl dithiophosphates have a methylene or an ethylene group for the alkylene part of the molecule . In Example 21, it has previously been shown that the 0-ethyl S'-n-propyl dithio-phosphate ester derivatives of these products are superior, novel pesticides . The effect of higher alkylene groups was also studied, using the present, novel 0-lower alkyl S'-higher alkyl dithiophosphate esters . As an optimized struc-ture type, 0-ethyl S-n-propyl S 1 -methylthioalkyl dithiophos-phate was selected for to Cg alkylene variation. The results are shown in Table VII below.

TABLE VI Effect of the Structure of the S~Alkylthioether Group Activity 0-Ethyl S-n-Propyl S-2-AlkyIthioprop 1 Dith Mexican Bean Experimental Compound , S .Armyworm Beetles Spider Mites Bean Example Mortality,$ Mortality,$ Mortality,$ Morta No. (at 250 ppm) (at 50 ppm) (at 10 ppm) (at 6 CH3 100 100 100 10 7 100 70 100 10 °2H5 8 n-C3H7 100 100 100 10 9 l-C-JBL 100 100 100 5 100 100 90 5 n-°6H13 TABLE VII Effect of the Structure of the Alkylene Group on t Activity of 0=Ethyl S-n-Propyl S' -2-Methylth Experimental Compound Mortality Produced at 50 ppm, Example Mexican Bean Spider Bean No. • Q S •Army orm Beetles Mites Aphids Housef 100 100 100 100 100 6 CH2CH(CH3) 100 100 100 100 100 12 CH2CH(C¾CH3) 8o 10 loo loo 100 13 CH2CH[C(CH3)3] 0 0 100 30 20 The data indicate that in these variations of the alkylene portion, the C3 and alkylene groups and especially the group, lead to highly active compounds. Alkylene groups having more than 4 carbon atoms show a definite drop in activi-ty. For example, the t-butyl ethylene compound shows very little insecticidal activity at 50 ppm.

Example 27 The Effect of the S-n-Propyl Group on the Toxicity Towards Warm Blooded Animals The pesticidally effective novel 0-ethyl S-n-propyl S ' -alkylthioalkyl compounds were also examined for their acute, oral toxicity on rats. Conventional toxicity experiments were designed to determine the effect on toxicity of the S-n-propyl group which is the key group in attributing the pesticidal activity. The data are shown in Table VIII below.

By studying the first three compounds, i.e. S-ethyl-thioethyl 0-ethyl dithiophosphate derivatives, it was found that both the 0,S-isomerization and replacement of an 0-ethyl with an S-n-propyl group result in reduced toxicity. Using the present process, the new S-propyl compound with a median lethal dose, LD.CJQ , OF 318 mg/kg is produced from Disyston hav-ing a median lethal toxicity, LD^ of 25 mg/kg.

The present process similarly yields S-n-propyl de-rivatives of reduced toxicity in the case of S-2-alkylthio-propyl 0-ethyl dithiophosphate derivatives as shown by the co -pounds of Examples 6-8. The S-2-n-propylthiopropyl compound of Example 8 has a particularly low toxicity.

It is most surprising and advantageous that within the present new class of compounds the highly effective pesti-cides have low toxicities.

TABLE VIII The Effect of the S~n=Propyl Group on the Toxicity Towards Warm Blooded Animals Experimental Compound Acute Oral Toxicity on Rats, Example No. Median Lethal Cone · , (Reference ) Structure LDc;ri mg/kg (Disystona) a) - Described in German Patent 1,032,247 In conclusion, it has been found in the present in-vention that novel, useful O-alkyl S1 -higher alkyl S-hydro^ carbylthioalkyl dithiophosphate compositions can be prepared by a combination of selective dealkylation and alkylation re-actions. Although the novel compositions are generally useful as animal and plant pesticides, it has been found that certain compositions are more attractive for economical use, lesser amounts of these compounds being sufficient for pest control. More specifically, O-ethyl S-n-propyl S' -hydrocarbylthioalkyl dithiophosphates represent a pesticidally very highly active but relatively non-toxic, novel class of pesticides. These pesticides are particularly attractive for the control of in-sects, mites, nematodes, foliar and soil fungi. Due to their high insecticidal effectiveness and low toxicity, they have a potentially high therapeutic index for application in animal health control.

It is to be understood that the invention is not limited to the various embodiments and specific examples shown above since these have been offered merely as illustrations.

Other 0,S-dialkyl S 1 -hydrocarbylthioalkyl dithiophosphates can be prepared and used and other modifications can be made thereof without departing from the spirit and purview of this invention. 1 SU- J 43 33966/5

Claims (5)

1. A process for preparing 0, S' -dialkyl S-substituted di thiophosphates of the formula I wherein and represent alkyl group which may be the same or different, represents a hydrocarbyl group optionally substituted with halogen, alkoxy, alkylthio, alkylsulphonyl, cyano and/or nitro; and Q represents an unsubstituted cyano- and/or halo-substituted alkylene group; which process comprises: a) reacting a dithiophosphate ester of the formula II R^O^ S-Q-S-R^ wherein R^> Q, and have the meanings given above, or of the formula Ila wherein R.^ has the meaning given above, R^ represents a hydrogen atom or an unsubstituted cyano- and/or halo-substituted alkyl g*oup and n represents zero or the integer 1 or 2, with a dealkylating agent ; b) reacting the dealkylated product thus obtained with an alkylating agent introducing the alkyl group R2» to obtain an 0,S' -dialkyl 3-hydrocarbylthioalkyl dithiophosphate of the' formula I as defined above, or an 0,S'-dialkyl-3-alkenyl dithiophosphate of the - 44 - 33966/5 wherein R^, R^, R^ and n have the meanings given above, and, i the latter case; c) reacting the said compound of the formula III with an organic thiol of the formula IV R^-SH (IV) wherein R, has the meaning given above to obtain an 0,s'- -dialkyl S-substituted dithiophosphate of the formula and/or wherein R^, Rg, R^, R^ and n hnve the meanings given above.

2. A process for preparing 0,S' -dialkyl .S-hydrocarbylthioalkyl dithiophosphatesof the formula I wherein ^, Rg and Q have the same meaning as in Claim 1 and R-j represents an unsubstituted or cyano- and/or halo-substituted alkyl group c an unsubstituted or cyano-, halo- and/or alkyl-substituted phenyl g-oup which process comprises: a) reacting a dithiophosphate ester of the formula II wherein R^, Q, and ^ have the meanings given above with a dealkylating agent; and b) reacting the dealkylated product thus obtained with an alkylating agent introducing the alkyl group R^.

3. Process according to claim 2 wherein R^ and R^ represent primary or secondary alkyl groups, which may be the same or different and which, individually, contain maximally l6 carbon atoms; R^ represents an unsubstituted or cyano- and/or halo-substituted alkyl group containing maximally l6 carbon atoms; and Q represents an unsubstituted or cyano- and/or halo-substituted alkylene group containing maximally 16 carbon atoms.

4. Process according to claim 3 wherein each of the groups R^, R^, -^ and Q, individually, contains maximally 8 carbon atoms. 5. Process according to claim 4 wherein each of the groups R^, R^ and R-,, individually, contains maximally 3 carbon atoms and the group Q contains maximally carbon atoms. 6. Process according to any one of claims 2 to 5 wherein Rj represents an unsubstituted alkyl group and Q represents an unsubstituted alkylene group. 33966-4 7· Process according to claim 2 wherein PL and R represent primary or secondary alkyl groups, which may be the same or different and which, individually, contain maximally 16 carbon atoms; R^ represents an unsubstituted or cyano-, halo- and/or alkyl-substituted phenyl group containing maximally 8 carbon atoms; and Q, represents an unsubstituted or cyano- and/or halo-substituted alkylene group containing maximally 16 carbon atoms. 8. Process according to claim wherein each of the groups R^, Rg and Q, individually, contains maximally 8 carbon atoms. 9· Process according to claim 8 wherein each of the groups R-^ and Rg, individually, contains maximally 3 carbon atoms and the group Q contains maximally carbon atoms. 10. Process according to any one of claims 2 and 7 to 9 wherein R^ represents an unsubstituted or halo- or alkyl-substituted phenyl group containing maximally 8 carbon atoms and Q represents an unsubstituted alkylene group. 11. Process according to claim 10 wherein R^ represents an unsubstituted or halo-substituted phenyl group. 12. Process according to claim 11 wherein R^ represents an unsubstituted or chloro- substituted phenyl group. 13· Process according to claim 11 wherein R^ represents an unsubstituted or mono- , di- or tri-chloro-substi tuted phenyl group. 4? 33966/6 14. A process for preparing 0, s' -dialkyl S-substituted dithiophosphates of the formula .. and/or wherein R^ R^, ^, n and Q have the same meaning as in Claim 1, and R^ represents an unsubstituted or cyano- and/or halo-substituted alkyl group or an unsubstituted or cyano-, halo- and/or alkyl- substituted phenyl group, which process comprises: a) reacting a dithiophosphate ester of the formula Ila (Ha) wherein R^, R^ and n have the meanings given above, with a dealkylating agent; b) reacting the dealkylated product thus obtained with an alkylating agent introducing the alkyl group Rg, to obtain an 0,3'--dialkyl S-alkenyl dithiophosphate of the formula III wherein ^ Rg, R^ and n have the meanings given above, and; 33966-3 organic thiol of the formula IV R^-SH (IV) wherein has the meaning given above. 15. Process according to claim 14 wherein R.^ and R^ represent primary or secondary alkyl groups, which may be the same or different and which, individually, contain maximaly l6 carbon atoms; the grouping (- [CH^ ]n~CH=CH-R^) contains, in toto maximally 8 carbon atoms; and R^ represents an unsubstituted or cyano- and/or halo-substituted alkyl group containing maximally 16 carbon atoms. 16. Process according to claim 15 wherein each of the groups R^, R2 and R^ , individually, contains maximally 8 carbon atoms. 17. Process according to claim l6 wherein each of the groups R , R and R , individually, contains maximally 3 carbon. atoms and the grouping (-[CH ] -CH=CH-R^) contains, in toto, maximally carbon atoms. l8. Process according to any one of claims 14 to 17 wherein R, and R> represent unsubstituted alkyl groups. 19. Process according to claim 14 wherein R, and R„ represent primary or secondary alkyl groups, which may be the same or different and which, individually, contain maximally l6 carbon atoms; R^ represents an unsubstituted or cyano-, halo- and/or alkyl- substituted phenyl group containing maximally 8 carbon - - - 20. Process according to claim 19 wherein the groups •~"*r and R^, individually, contain maximally 8 carbon atoms. 21. Process according to claim 20 wherein the grouping (- [CH2 ]n-CH=CH-R^) contains, in toto, maximally 4 carbon atoms, and each of the groups R^ and R≥, individually, contains maximally 3 carbon atoms. 22. Process according to any one of claims 1 and 19 to 21 wherein R^ represents an unsubstituted or halo- or alkyl-substi-tuted phenyl group containing maximally 8 carbon atoms, and R^ represents an unsubstituted alkyl group. 23. Process according to claim 22 wherein Ti^ represents an unsubstituted or halo-substituted phenyl group. 24. Process according to claim 23 wherein .-^ represents an unsubstituted or chloro-substituted phenyl group. 25· Process according to claim 2 wherein R^ represents an unsubstituted or mono-, di- or tri-chloro-substituted phenyl group. 26. Process according to any one of the preceeding claims wherein the dealkylating agent employed in step (a) is a nitrogen or phosphorous base, a thiolate salt or an inorganic salt. 27. Process according to any one of the preceeding claims wherein the alkylating agent employed in step (b) is an alkyl halide, alkyl sulphonate, alkyl phosphate, di-alkyl sulphate or 28. Process according to any one of the preceeding claims ~^ wherein the 0, S'-dialkyl S- substituted di thiophosphate obtained is subsequently oxidised to form the corresponding sulphoxide or sulphone. 29. Process according to claim 28 wherein the oxidation is effected by means of a peroxide or permanganate or of nitric acid or bromine. 30. Process according to claim 1 substantially as herein described with reference to any one of the examples 1 to 20. 31. 0, S'-dialkyl S-substi tuted di thiophosphates and their sulphoxides and sulphones whenever prepared by a process as claimed in any one of the preceeding claims. 32. 0, S'-dialkyl S-substi tuted di thiophosphates of the formula I' wherein R' ^ represents a methyl or ethyl group, R1 represents an alkyl group containing 3 or 4 carbon atoms, R'j represents alkyl group containing maximally 10 carbon atoms, a phenyl group or a mono- or po.ly-halo-substi tuted phenyl group, Q' represents an alkylene group containing maximally 4 carbon atoms, and provided that (i) when Q' is methylene, y is zero, and that (ii) when Q,' is ethylene, R'2 is a primary or secondary alkyl group. 33· 0, S'-dialkyl S-substi tuted di thiophosphates of the formula I" wherein R*3 and y nave the meanings given in claim 32, and k represents an integer of from 1 to 4 provided that (i) when k is 1, y is zero, and (ii) when k is 2, R'2 is a primary or secondary alkyl group. 3 . 0, S'-dialkyl S-substi tuted di thiophosphates as defined in claim 33 wherein k is 1. 35. 0, s'-dialkyl S-substi tuted di thiophosphates as defined in claim 33 wherein k is 2. 36. 0, S'-dialkyl S-substi tuted di thiophosphates as defined in claim 33 wherein k is 3· 37. 0, S'-dialkyl S-substi tuted di thiophosphates of the formula I'" - 51 - wherein R' R' 2> and have the meanings given in claim 32, and R^ represents a methyl or ethyl group. 38. 0, S' -dialkyl S-substituted dithiophosphates as defined in claim 37 wherein R,_ represents a methyl group. 39· An 0, sT -dialkyl S-substituted di thiophosphate as defined in any one of claims 3 to 38 wherein R'^ represents an ethyl group . 40.. An 0,S' -dialkyl S-substituted di thiophosphate as defined in any one of claims 32 to 39 wherein R'^ represents an n-propyl group . 41. An 0,S' -dialkyl S-substituted dithiophosphate as defined in any one of claims 32 to 40 wherein R'.-. represents an alkyl group containing maximally 4 carbon atoms. 42. An 0, S' -dialkyl S-substituted di thiophosphate as defined in any one of claims 32 to 40 wherein R'^ represents a phenyl group or a mono- or tri-halo-substituted phenyl group. 43. An 0,S' -dialkyl S-substituted di thiophosphate as defined in claim 42 wherein R'.-. represents a phenyl or para--halo-phenyl group. 44. An 0,s' -dialkyl S-substituted di thiophosphate as defined in claim 43 wherein R1^ represents a phenyl or para-chloro- -phenyl group. 45. An 0,s' -dialkyl S-substituted di thiophosphate as defined in any one of claims 32 to 44 wherein y is zero. compound of the formula compound of the formula P CH^-CH2-CH2-S- S—CH —CH -S—C^H-. d d d > 48. A compound of the formula C H_--0 0 25 \ P / CH^ CH,-CH -CH -S// S-CH -CH-S-C H^ 3 d d d d ) 49. A compound of the formula compound of the formula C2H5-0 0 51 . A compound of the formula S-CH2-CH2-CH3 52 . A pesticidal composition comprising, as active ingredient, a compound as claimed in any one of claims 32 to 51 * together with a liquid, liquid normally gaseous or solid diluent or carrier therefor. 53 · A method of controlling animal and/or plant pests which comprises applying to the locus or natrual habitat of the pest a compound as claimed in any one of claims 32 to 51 ·

5. . A method according to claim 53 wherein the pests are insects of the order LEPIDOPTERA or insects infecting animal livestock. For the Applicants