GB2140808A

GB2140808A - S-Alkyl alkylphosphonothioc halides

Info

Publication number: GB2140808A
Application number: GB08332398A
Authority: GB
Inventors: Mohamed Abdel Hamid Fahmy
Original assignee: Rhone Poulenc Agrochimie SA
Current assignee: Bayer CropScience SA
Priority date: 1980-11-21
Filing date: 1983-12-05
Publication date: 1984-12-05
Also published as: RO85049A; CH651575A5; MA19336A1; AT380885B; PH18262A; RO90683B; OA06955A; IL64186A0; BG36349A3; LU83780A1; ATA501181A; BR8107581A; GB2087891A; DD202167A5; AU553581B2; RO87258A; CA1224474A; AU7763181A; ES507318A0; CH650002A5

Abstract

The invention relates to compounds having the formula <IMAGE> in which R is alkyl of 1 to 8 carbon atoms, haloalkyl of 1 to 8 carbon atoms, alkenyl of 2 to 8 carbon atoms, haloalkenyl of 2 to 8 carbon atoms, alkynyl of 2 to 8 carbon atoms or haloalkynyl of 2 to 8 carbon atoms; R2 is tertiary alkyl of 4 to 8 carbon atoms; and X is a halogen atom which are useful as intermediates in the preparation of alkylphosphonothioate insecticides and nematocides.

Description

1 GB2140808A 1

SPECIFICATION

Alkylphosphonothioate insecticides and nernatocides and intermediates therefor This invention relates to O-alkyl and O-aryl S-(tertiary alkyl) alkylphosphonothioate compounds, 5 their preparation, insecticidal and nematocidal compositions containing them and intermediates for their preparation.

Certain alkylphosphonothioate insecticides are described in the prior art, for example, in U.S.

Patent No. 3,209,020. However, none of the species described in that patent or in other known prior art possess a tertiary alkyl group attached to the sulphur atom.

It has now been found that certain S-tertiary alkyl compounds possess particularly useful insecticidal or nematocidal activity.

The present invention accordingly provides compounds of the general formula:- R - P 0 OR 11.111 1 R 2 (1) wherein R represents alkyl of 1 to 8 carbon atoms, haloalkyl of 1 to 8 carbon atoms, alkenyl of 2 to 8 carbon atoms, haloalkenyl of 2 to 8 carbon atoms, alkynyl of 2 to 8 carbon atoms, or haloalkynyl of 2 to 8 carbon atoms, R, represents alkyl of 1 to 8 carbon atoms or aryl and R2 represents tertiary alkyl of 4 to 8 carbon atoms, which exhibit a wide range of insecticidal and nematocidal activity and are of particular interest in controlling corn rootworm (Diabrotica sp) 25 because of their excellent activity against this pest and their long residual soil activity.

It is to be understood that, in this specification and the accompanying claims, unless otherwise indicated, alkyl groups and moieties may be straight- or branched-chain.

In general formula 1:

R preferably represents alkyl of 1 to 4 carbon atoms, especially methyl or ethyl; R, preferably represents alkyl of 1 to 4 carbon atoms (compounds in which R, represents phenyl or phenyl substituted by one or more (preferably one) atoms or radicals selected from the group consisting of alkyl of 1 to 4 carbon atoms (preferably methyl), alkoxy of 1 to 4 carbon atoms (preferably methoxy), alkyllhio of 1 to 4 carbon atoms, alkylsulphinyl of 1 to 4 carbon atoms, alkylsulphonyl of 1 to 4 carbon atoms, chlorine, bromine, fluorine, nitro, cyano and trif 1 uoro methyl, are also preferred); and R, preferably represents tert-butyl or tert-amyi.

Particularly preferred compounds of general formula 1 are those in which R represents methyl or ethyl, R, represents alkyl of 1 to 4 carbon atoms and R, represents t-butyl or t-amyi. Other particularly preferred compounds are those in which R represents methyl or ethyl, R, represents 40 phenyl or phenyl substituted by a chlorine or fluorine atom, or by a methyl, methoxy or trifluoromethyl group and R2 represents t-butyl or t-amyl.

The compounds of general formula 1 can be prepared by the application of known methods. By the expression -known methods- as used in this specification is meant methods heretofore used or described in the literature.

According to a feature of the invention the compounds of general formula 1 are prepared by the process which comprises reacting an S-alkyl alkylphosphonothioic halide of the general formula:- 0 X 11 R - P "' SR 2 (11) wherein R and R2 are as hereinbefore defined and X represents a halogen atom, preferably chlorine, with an alcohol or phenol of the general formula R,OH, wherein R, is as hereinbefore defined, in the presence of a base.

The process proceeds in accordance with the reaction scheme:

2 GB2140808A 2 0 X 0 OR R - P + R OH 11Rgf:z R - P + base. HX (li) 'SR 2 "'SR 2 5 wherein R, R, R2 and X are as hereinbefore defined.

The reaction is advantageously carried out at a temperature of about OC to 1 00C in an organic solvent in the presence of a tertiary amine, or an alkali metal salt of the alcohol or the 10 phenol RjOH, prepared from the alcohol or phenol and an alkali metal such as sodium.

Suitable organic solvents are, for example, benzene, toluene, cyclohexane and 2-butanone, or an alcohol R,OH.

Suitable tertiary amines include trimethylamine, triethylamine, dimethylaniline, diethylaniline and pyridine.

The S-alkyl phosphonothioic halides of general formula 11 wherein R, R2 and X are as hereinbefore defined also constitute a feature of the present invention.

The synthesis of S-alkyl alkylphosphonothioic halides is usually accomplished by methods other than the direct addition of thiols to alkylphosphonic dihalides because direct reaction is normally accompanied by an undesirable side reaction in which both halogen atoms in the phosphonic dihalide are substituted by an alkyl thiol. The side reaction is a particular problem when normal alkyl thiols are used. Thus, when the synthesis of normal S-alkyl alkylphosphonothioic chlorides is desired, alternative routes are selected.

It has been discovered that tertiary alkylthiols react smoothly with alkylphosphonic dihalides to give mono addition of one thiol in good yield, according to the following equation:

4 L',' X solvent 0 X 11 11 RP + HSR 2 + base + base.HX 30 X SR 2 ill wherein R, R2 and X are as hereinbefore defined. According to a feature of the present invention, the compounds of general formula 11 are prepared by reacting a compound of the general formula Ill wherein R and X are as hereinbefore defined with a compound of the general formula R2SH, wherein R2 is as hereinbefore defined, in a solvent, in the presence of a base, at a temperature of about WC to 1 OWC. In the compounds of general formula 11, preferably R represents alkyl of 1 to 4 carbon atoms, particularly methyl or ethyl; preferably R2 represents 40 tert-butyl or tert-amyi, and preferably X represents chlorine. - Suitably the reaction is carried out in an organic solvent, in the presence of a tertiary amine such as trimethylamine, triethylamine, pyridine, dimethylanifine or diethylaniline.

Suitable organic solvents, which are preferred, incl ude benzene, toluene, cyclohexane, acetone and 2-butanone.

Generally, the reaction is conducted at a temperature of abot 20C to 1 OWC, but the temperature is not critical except insofar as it is sufficient to make the reaction proceed at a reasonable rate and is not excessive. It has been. found advantageous to add the tertiary amine to the other reactants at a temperature of about 2WC to 30C and then to heat the entire reaction mixture to a temperature of about 7WC to WC to complete the reaction.

The reaction is normally carried out with an approximately equal molar ratio of the alkyl phosphonic dihalide, thiol and the base. An excess of about 10 to 20% of the alkylphosphonic dihalide can be used relative to the other reactants. However, the use of a slight excess of the thiol and the base relative to the alkylphosphonic dihalide (5-10% excess) did not appreciably affect the yield.

Particularly preferred compounds of general formula 11 are S-tert-butyl ethylphosphonothioic chloride, S-tert-amyl ethyl phosphonoth ioic chloride, S-tert-butyl methylphosphonothioic chloride, and S-tert-amy] methyl-phosphonothioic chloride which are used as intermediates in the following Examples 1 to 16.

The following Examples illustrate the preparation of compounds of general formulae 1 and 11 60 and the pesticidal properties of the former.

EXAMPLE 1 S-tert-Butyl ethylphosphonothioic chloride z 3 GB 2 140 808A 3 0 cl CH 3 CH 2- P CH 3 '1 1 5 3 Un 3 To a solution of ethylphosphonic dichloride (32.0 g, 0.22 mol) in 300 ml toluene, was added 2-10 methyl-2-propanethiol (18 g, 0.2 mol). While stirring, triethylamine (22 g, 0.22 mol) was added dropwise; the temperature of the reaction mixture was maintained at 30-35C during the addition of the amine. After addition of the amine the mixture was stirred overnight at room temperature. The amine hydrochloride which precipitated was filtered off and the toluene solution was concentrated under vacuum. Hexane (200 ml) was added and the solution 15 obtained was filtered.

The solvents were stripped off under vacuum and the residual liquid was distilled. The product (25 g, 72.5% yield) distilled at 72-73C/0.7 mmHg. Proton magnetic resonance spectroscopy in deuterochloroforrh (CDC13) With Si(Me)4 as reference confirmed the structure of 20 the title compound.

EXAMPLE 2

Preparation of O-ethyl-S-tert-butyl ethylphosphonothioate To a solution of S-tert-butyl ethylphosphonothioic chloride (obtained as described in Example 1) (8.0 g, 0.048 mol) in toluene (50 ml) was added a solution of sodium ethoxide (0.04 mol) in 25 ethanol (40 ml). The addition was carried out dropwise, with stirring under a nitrogen atmosphere. Stirring was continued overnight at room temperature, and then approximately 80% of the solvents were removed under vacuum. Toluene (100 ml) was added and the sodium chloride formed from the reaction was filtered off. Toluene was stripped off under vacuum and the residual liquid was distilled. The product (5.8 g, 69.6% yield) distilled at 69-72C/0.2 30 mmHg.

Analysis of the proton magnetic resonance spectrum of this product confirmed the structure of the title compound.

EXAMPLE 3 to 6 In a manner analogous to that of Example 2, the following compounds were prepared.

0 OR 1 N 1/11, R - P SR 2 45 Example R R, R2 B.p. ClmmHg 3 C2H5 CH3 t-butyl 64-67/0.7 4 C2H, C3H7 t-butyl 61 63/0.05 C21-1, (CHICH t-butyl 42-43/0.05 6 C21-1, C21-1, t-amy] 5658/0.07 50 EXAMPLE 7 Preparation of 0-phenyi-S-tert-butyl ethylphosphonothioate 0 IL--0-0 c 2 k-F CH 3 1 S k 1 -k.;11 3 t;ri 3 To a solution of S-tert-butyl ethyl phosphonoth ioic chloride (5 g, 0.025 mol), and phenol 65 4 GB 2 140 808A 4 (2.35 9, 0.025 mol) in acetone (20 mi), was added, in one portion, triethylamine (2.5 g, 0.025 mol); the mixture was stirred overnight under nitrogen at room temperature. The reaction mixture was then diluted with toluene (100 m[) and washed once with 5% w/v sodium hydroxide solution, and twice with water. The solution was dried over anhydrous sodium sulphate and the solvent was stripped off under vacuum. The residual liquid was subjected to 5 high vacuum (0.2 mmHg) at 6WC for 15 minutes to yield the desired product as confirmed by its proton magnetic resonance spectrum in deutero-chloroform (CDCI,) with Si(Me), as reference.

EXAMPLES 8 to 15 In a manner analogous to that of Example 7, the following compounds were prepared. 10 0 OR 11 R - p '11-1 SR A Example R R, R, 8 C2H5 o-methyl-phenyl tert-butyl 20 9 C21-1, p-chloro-phenyl tert-butyl C21-1, phenyl tert-arnyl 11 C21-1, rn-trifluoromethyl- tert-amy] phenyl 12 C21-1, p-fluoro-phenyl tert-arnyl 25 13 C2H5 p-chloro-phenyl tert-arnyl 14 C21-1, o-chloro-phenyl tert-arnyl CH3 phenyl tert-amyl 30 EXAMPLE 16

Meta-cresol (4.6 g) was dissolved in acetone (100 mi) and potassium carbonate was added. The mixture was stirred at room temperature for 30 minutes, and S-tert-butyl methylphosphonothioic chloride (7.5 g) was then added.

Stirring was continued overnight, and the solution was then filtered and the solvent evaporated. Water (100 mi) was added and the mixture extracted with diethyl ether (100 mi). The ethereal extract was washed once with 5% w/v potassium hydroxide solution, then with water and was finally dried and evaporated to give 4.0 9 of 0-3-toly]-S-tert-butyl methylphosphonothioate. The product was identified by its proton magnetic resonance spectrum. Its purity is higher than 90%.

EXAMPLE 17

Testing for corn rootworm intrinisic activity, and activity against Southern Armyworm.

A- Com Rootworm, Intrinsic Activity (CRW) The test compound is prepared as a one percent w/v stock solution with acetone or ethanol. The stock solution is then diluted with an aqueous solution of Tween-20 (500 ppm) and water to the appropriate concentration (i.e. 500, 100, 1, 0.1 or 0.05 ppm of test compound). Two ml of the test solution is pipetted into a 9 cm petri dish containing two layers of filter paper.

Second instar larvae are introduced and the dish closed. Observations for mortality and moribund larvae are made after two days (48 hours) exposure. Insecticidal activity is primarily by contact and vapour action with minimal ingestion.

-1 B. Southern Armyworm Intrinsic Activity (SAW) Stock solution (1 % w/v) of test compound in acetone was prepared and diluted to the desired 5 5 concentration using a 500 ppm Tween-20 aqueous solution. Lima bean leaves are dipped into the solution and transferred to petri dishes (100 X 15 mm) each containing two filter papers moistened with 2 mi water. Each petri dish contained one leaf and was left open to dry out the solution on the leaf. Five third instar larvae of Southern Armyworm (Spodoptera eridania) were 60 added to the leaf and the dish was finally covered.

The dishes were kept at 78'F for 72 hours and percentage kill was recorded.

The results of Tests A and B are tabulated in Table 1 which shows the perecentage kill obtained using compounds prepared in the indicated Examples.

GB2140808A 5 TABLE 1 % Kill CRW SAW rate in ppm 1 0.1 0.05 500 100 Example No - 10 2 100 95 75 100 100 3 100 100 100 100 90 4 100 70 - 100 15 80 45 80 15 6 100 95 100 100 50 15 7 100 100 90 100 95 8 100 100 15 100 100 9 100 35 40 100 95 100 100 70 100 80 11 100 100 85 100 80 20 12 100 100 90 100 60 13 100 85 55 100 75 14 95 95 15 -, 100 80 16 100 100 100 - These results show the excellent insecticidal activity of the compourlds according to the invention which can be used for combatting numerous insects such as coleoptera (e.g. Diabrotica sp) or corn rootworm and lepidoptera.

For use in practice, the compounds of general formula I are generally employed in the form of 30 compositions, which also constitute a feature of the invention, and which generally comprise, in addition to the active compound of general formula 1, at least one agriculturally acceptable carrier and/or surface-active agent. The proportion of active -ingredient in these compositions is generally from 0.001 % to about 95% by weight: the proportion of surface active agent is generally from 0 to 20% by weight.

In the present specification, the term "carrier" denotes an organic or inorganic, natural or synthetic material with which the active ingredient is associated in order to facilitate its application to the plants or to the soil. The carrier can be solid (e.g. clays, natural or synthetic silicates, silica, resins, waxes and solid fertilisers) or liquid (e.g. water, alcohols, petroleum fractions, aromatic or paraffinic hydrocarbons, chlorohydrocarbons and liquefied gases).

The surface-active agent can be an emulsifying, dispersing, deflocculating or wetting agent of the ionic or non-ionic type. Examples which may be mentioned are salts of polyacrylic acids, salts of lignosulphonic acids, salts of phenolsulphonic or naphthalenesulphonic acids, condensates of ethylene oxide with fatty alcohols, fatty acids or fatty amines, substituted phenols (in particular alkylphenols or arylphenols), salts or sulphosuccinic acid esters, taurine derivatives (in 45 particular alkyltaurates), and phosphoric acid esters of condensates of ethylene oxide with alcohols or with phenols.

The compositions can also contain other ingredients, e.g. thickeners, thixotropic agents, protective colloids, adhesives, penetrating agents and stabilisers, and also other known active ingredients having pesticidal properties (in particular herbicidal, fungicidal and insecticidal properties), properties which assist plant growth (in particular fertilisers) or properties which regulate plant growth. More generally, the compounds according to the invention can be combined with any of the solid or liquid additives used in the customary techniques for the preparation of pesticidal compositions.

The compositions according to the invention can be prepared in the form of wettable powders, dusting powders, granules, solutions, emulsifiable concentrates, emulsions, suspension concentrates and aerosols.

The wettable powders, or spraying powders, usually contain from 20 to 95% by weight of active ingredient and generally contain, in addition to a solid carrier, from 0 to 5% by weight of wetting agent, and from 0 to 10% by weight of one or more stabilisers and/or other additives, 60 such as penetrating agents, adhesives or anti-caking agents and dyestuffs.

They are prepared by mixing the constituents in mixers and by grinding them in mills or other suitable grinders, e.g. air grinders, so as to obtain the desired particle size.

The composition of an 80% w/w wettable powder according to the invention is given below by way of example (in the following Examples percentages are by weight):

GB 2 140 808A 6 EXAMPLE 18 active ingredient 80% sodium a kyl naphthalenesu 1 phonate 2% sodium lignosulphonate 2% 5 anti-caking silica 3% kaolinite 13% Another example of a wettable powder according to the invention is given below:

EXAMPLE 19 active ingredient 50% sodium alkyinaphthalenesulphonate 2% low-viscosity methylcellulose 2% 15 diatomaceous earth 46% Another example of a wettable powder according to the invention is given below:

EXAMPLE 20 active ingredient 90% sodium dioctyisulphosuccinate 0.2% synthetic silica 9.8% Granules, which are intended to be placed on the soil, are usually prepared so that they have dimensions of between 0. 1 and 2 mm, and they can be manufactured by agglomeration or impregnation. In general, the granules will contain from 0.5 to 25% of active ingredient and from 0 to 10% by weight of additives, such as stabilisers, slow-release modifiers, binders and solvents.

Emulsifiable concentrates, which can be applied, after dilution, by spraying, usually contain 30 from 10 to 50% by weight/volume of active ingredient. In addition to the active ingredient and the solvent, they can also contain, if necessary, from 2 to 20% by weight/volume of an emulsifying agent and from 2 to 20% by weight/volume of suitable additives, such as surface active agents, stabilisers, penetrating agents, corrosion inhibitors, dyestuffs and adhesives.

Suspension concentrates, which can also be applied by spraying, are prepared so as to give a 35 stable fluid product which does not settle out, and they usually contain from 10 to 75% by weight of active ingredient, from 0. 5 to 15% by weight of surface-active agent, from 0. 1 to 10% by weight of thixotropic agents, from 0 to 10% of suitable additives, such as anti-foam agents, corrosion inhibitors, stabilisers, penetrating agents and adhesives, and, as the carrier, water or an organic liquid in which the active ingredient is substantially insoluble; certain organic solids, or inorganic salts, can be dissolved in the carrier in order to assist in preventing sedimentation or to act as anti-freeze agents for water.

Aqueous dispersions and aqueous emulsions, which are obtained by diluting the abovemen tioned compositions with water, in particular the wettable powders and emulsifiable concentrates according to the invention, are also included in the general scope of the present invention. The 45 emulsions thus obtained can be of the water-in-oil type or of the oil-in- water type and they can - have a thick consistency such as that of a mayonnaise.

All these aqueous dispersions and emulsions, or spraying mixtures, can be applied by any suitable means to the crops in which weeds are to be destroyed, mainly by spraying, at doses which are generally of the order of 500 to 1,000 litres of spraying mixture per hectare.

As indicated above, the invention also relates to a method for the control of insects in crops, which comprises applying an effective amount of at least one of the compounds of general formula 1 to the aerial part of the crops and/or to the soil or incorporating the compound into the soil.

For the control of insects, the compounds of general formula 1 are used at concentrations of 55 from 0.0 1 % to about 1 % by weight of the total formulation. As nematocides, the active component is effective within the range of about 0.5 to 5 kg/hectare. Under ideal conditions, depending on the pest to be controlled, the lower rate may offer adequate protection. On the other hand, adverse weather conditions, resistance of the pest and other factors may require that the active ingredient be used in higher proportions.

When the pest is soil-borne, the formulation containing the active ingredient is distributed evenly over the area to be treated in any convenient manner. The active component can be washed into the soil by spraying with water over the area or can be left to the natural action of rainfall. After application, the formulation can be distributed in the soil by ploughing or disking.

Application can be prior to planting or after planting but before sprouting has taken place or 1 L 7 GB 2 140 808A 7 after sprouting.

Claims

1. A compound of the general formula:

0 X 11 / R - P/ 1 '9R 2 (11) wherein R represents alkyl of 1 to 8 carbon atoms, haloalkyl of 1 to 8 carbon atoms, alkenyl of 2 to 8 carbon atoms, haloalkenyl of 2 to 8 carbon atoms, alkynyl of 2 to 8 carbon atoms, or haloalkynyl of 2 to 8 carbon atoms, R2 represents tertiary alkyl of 4 to 8 carbon atoms, and X represents a halogen atom.

2. A compound according to claim 1 wherein X represents a chlorine atom.

3. A compound according to claim 1 or claim 2 wherein R2 represents tbutyl or t-amy].

4. A compound according to plaim 1, 2 or 3 wherein R represents alkyl of 1 to 4 carbon atoms.

5. S-tert-Butyl ethylphosphonothioic chloride.

6. S-tert-Arnyl ethylphosphonothioic chloride.

7. S-tert-Butyl methyl phosphonothioic chloride.

8. S-tert-Amyl methyl phosphonoth ioic chloride.

9. A process for the preparation of a compound of general formula 11 depicted in claim 1 wherein R, R2and X are as defined in claim 1, which comprises reacting a compound of the 25 general formula:

0 X R R - P "I' X (111) (wherein R and X are as defined in claim 1) with a compound of the general formula R2SH wherein R2 is as defined in claim 1, in a solvent in the presence of a base at a temperature of 35 about 20T to 1 00T.

10. A process according to claim 9 in which the solvent is benzene, toluene, cyclohexane, acetone or 2-butanone.

11. A process according to claim 9 or 10 in which the base is trimethylamine, triethylamine, pyridine, dimethylaniline or diethylaniline.

T2. A process according to claim 9 substantially as hereinbefore described with especial reference to Example 1.

13. A compound of general formula 11 depicted in claim 1 wherein R and X are as defined in claim 1 when prepared by the process claimed in any one of claims 9 to 12.

Printed in the United Kingdom for Her Majesty's Stationery Office, Dd 8818935, 1984, 4235. Published at The Patent Office, 25 Southampton Buildings, London, WC2A 'I AY, from which copies may be obtained.