GB2034703A - 2,6-dihalobenzyl esters - Google Patents

Abstract

This invention relates to 2,6- dihalobenzyl esters. There are provided 2,6-dihalobenzyl esters of formula I: <IMAGE> where R<1> and R<2> are independently selected from fluoro, chloro and bromo, Y<1> is chloro, and Y<2> is fluoro or chloro, provided that when R<1> and R<2> are both bromo Y<2> is fluoro and when neither of R<1> and R<2> is bromo, at least one of R<1> and R<2> is the same as at least one of Y<1> and Y<2>; methods for their manufacture; pesticidal compositions containing them and their use as pesticides. Compounds of formula I exhibit pesticidal, e.g. insecticidal and acaricidal, activity.

Description

SPECIFICATION 2,6-Dihalobenzyl esters and their use as pesticides This invention relates to 2,6-dihalobenzyl esters, to their preparation, and to compositions containing them for use as pesticides, especially as insecticides and acaricides.

Belgian Patent Specification No. 862,109 (Bayer A.G.) relates to a general class of compounds of formula

where the R moieties, which may be the same or different, are selected from fluoro, chloro and bromo, and when R is fluoro or bromo, m is O to 5 and n is O to 5 provided that m and n cannot both be 0; when R is chloro, m is 0 to 4 and n is 1 to 5; and when m isO and n is 5, R may be methyl in addition to the other moieties. This Belgian Patent also mentions generally the existence in the prior art of similar compounds in which the benzyl moiety is substituted exclusively with chlorine atoms.

It has now surprisingly been discovered that a novel group of compounds falling within the broad group of compounds discussed above has especially useful pesticidal activity, in particular surprising miticidal activity in addition to insecticidal activity.

According to the invention therefore there are provided 2,6-dihalobenzyl esters of formula I:

where R1 and R2 are independently selected from fluoro, chloro and bromo, Y' is chloro, and Y2 iS fluoro or chloro, provided that when R1 and R2 are both bromo Y2 is fluoro and when neither of R1 and R2 is bromo, at least one of R' and R2 is the same as at least one of Y' and2.

The compounds of formula I may exist as geometrical and optical isomers, mixtures of isomers and racemates, there being two centres of asymmetry in the substituted cyclopropyl ring system, as will be readily apparent to those skilled in the art.The preferred compounds of the invention are the ciscompounds of formula I, those which are conventionally designated 1 ,R-cis-compounds being the most preferred.

Advantageously in the compounds of formula I, R', R2 andY2 are each fluoro or chloro, and Y' is chloro, at least one of R1 and R2 being the same as at least one of Y1 and2. The compounds wherein at least two of R1, R2 and Y2 are chloro, the other being fluoro and chloro, are particularly advantageous.

The 2,6-dihalobenzyl ester of formula I may be prepared by analogous methods to those used for known compounds. A convenient process comprises reaction of a compound of formula Il:-

with a compound of formula Ill:-

where R1, R2, Y' and y2 are as defined above, one of Q and Z represents a halogen atom, preferably a chlorine or bromine atom, and the other represents a hydroxy group. The reaction is preferably carried out in the presence of a suitable base, for example a tertiary amine such as triethylamine or an alkali metal carbonate such as potassium or sodium carbonate, in the presence of an inert solvent.

Conveniently Z represents a hydroxy group and Q represents a chlorine or bromine atom.

The cqmpounds of formula II above and their individual isomers are conveniently prepared in known manner, for example as described in U.K. Patent Specifications Nos. 1,413,491 and 1,448,228.

The compounds of formula Ill above are readily prepared from 2,6-dichlorotoluene and 2-chloro6-fluoro-toluene, which are known compounds, by conventional halogenating techniques e.g. reaction with N-bromo-succinimide, and subsequent hydrolysis if desired.

The 2,6-dihalobenzyl esters according to the invention are of interest as pesticides especially as insecticides and acaricides for domestic and agricultural outlets. The invention therefore includes within its scope pesticidal compositions comprising a carrier and/or a surface-active agent together with, as active ingredient, a 2,6-dihalobenzyl ester of formula I. The invention also includes a method of combating insect, tick and/or acarid pests, particularly mites, at a locus which comprises applying to the locus a pesticidally effective amount of a 2,6-dihalobenzyl ester of the invention or composition containing such a compound.

The term "carrier" as used herein means a material, which may be inorganic or organic and of synthetic or natural origin, with which the active compound is mixed or formulated to facilitate its application to the plant, seed, soil or other object to be treated, or its storage, transport or handling. The carrier may be a solid or a liquid. Any of the materials usually applied in formulating pesticides.

herbicides, or fungicides may be used as the carrier.

Suitable solid carriers are 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 vermiculites; aluminium silicates, for example, kaolinites, montmorillinites and micas; calcium carbonates; calcium sulphate; synthetic hydrated silicon oxides and synthetic calcium or aluminium silicates; elements for example, carbon and sulphur; natural and synthetic resins such as, for example coumarone resins, polyvinyl chloride and styrene polymers; solid polychlorophenols; bitumen; waxes such as for example, beeswax, paraffin wax, and chlorinated mineral waxes; and solid fertilisers, for example superphosphates.

Suitable liquid carriers are water, alcohols, for example, isopropanol and glycols; ketones for example, acetone, methyl ethyl ketone, and cyclohexanone; ethers; aromatic hydrocarbons, for example benzene, toluene and xylene; petroleum fractions, for example kerosine and light mineral oils; chlorinated hydrocarbons, for example carbon tetrachloride perchloroethylene, trichloroethane; and liquefied normally vaporous, gaseous compounds. Mixtures of different liquids are often suitable.

The surface-active agent may be an emulsifying agent or a dispersing agent or a wetting agent; it may be nonionic or ionic. Any of the surface-active agents usually applied in formulating pesticides, herbicides or fungicides, may be used. Examples of suitable surface active agents are the sodium or calcium salts of polyacrylic acids and lignin sulphonic acids; the condensation products of fatty acids or aliphatic amines or amides containing at least 12 carbon atoms 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 alcohols or alkyl phenols for example p-octylphenol orp-octylcresol, with ethylene oxide and/or propylene oxide; sulphates or sulphonates of these condensation products; alkali or alkaline earth metal salts, preferably sodium salts, or sulphuric or suiphonic 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 sodium dodecyl benzene sulphate; and polymers of ethylene oxide and copolymers of ethylene oxide and propylene oxide.

The compositions of the invention may be formulates as wettable powders, dusts, granules, solutions, emulsifiable concentrates, emulsions, suspension concentrates and aerosols. Wettable powders are usually compounded to contain 25, 60 and 75% of toxicant and usually contain, in addition, to solid carrier, 310% w of a dispersing agent and, where necessary, 0-1 0% w of stabiliser(s) and/or other additives such as penetrants or stickers. Dusts are usually formulated as a dust concentrate having a similar composition 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 1 0% w of toxicant. 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 -25% w toxicant and 0-10% w of additives such as stabilisers, slow release modifiers and binding agents. Emulsifiable concentrates usually contain, in addition to the solvent and, when necessary, co-solvent, 10-50% w toxicant, 2-20% w/v emulsifiers and 0-20% w/v of appropriate additives such as stabilisers, penetrants and corrosion inhibitors.Suspension concentrates are compounded so as to obtain a stable, non-sedimenting flowable product and usually contain 1075% w toxicant, 0.5-1 5% w of dispersing agents, 0.1-1 0% w of suspending agents such as protective colloids and thixotropic agents, 0-10% w af appropriate additives such as defoamers, corrosion inhibitors, stabilisers, penetrants and stickers, and as carrier, water or an organic liquid in which the toxicant is substantially insoluble; certain organic solids or inorganic salts may be dissolved in the carrier 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 present invention. The said emulsions may be of the water-in-oil or of the oil-in-water type, and may have a thick "mayonnaise"-like consistency.

The compositions of the invention may also contain other ingredients, for example, other compounds possessing pesticidal, herbicidal or fungicidal properties.

The invention will be better understood from the following Examples.

EXAMPLE 1 -- Preparation of 1 .R-cis-2-chloro-6-fluoro-benzyl 2-(2,2-dichlorovinyl)-3,3-dimethylcyclopropane carboxylate (a) Preparation of 2-chloro-6-fluorobenzylbromide 2-chloro-6-fluorotoluene (14.45g) and N-bromo-succinimide (19.6g) were stirred together with azo-bis-isobutyronitrile (0.1 g) in anhydrous carbon tetrachloride under reflux for 18 hours exposure to radiation from an infra-red lamp. The resulting solution was cooled in ice, filtered and evaporated to leave a pale orange liquid which was distilled under reduced pressure of nitrogen to yield the title product (20.1g, 90%) b.p. 740C/3.00 mm Hg.

(b) Preparation of 1 ,R-cis-2-chloro-6-fluorobenzyl 2-(2,2-dichlorovinyl)-3,3-dimethylcyclopropane carboxylate 1 ,R-cis-2-(2,2-dich lorovi nyl)-3.3-dimethylcyclo-propa ne carboxylic acid (1 , 1 g), 2-chloro-6- fluorobenzyl-bromide (1 ,lg) and anhydrous potassium carbonate (0.7g) were stirred together in acetone under reflux for 2 hours. The reaction mixture was cooled, diluted with water and extracted 3 times with 50 ml portions of diethyl ether. The combined extracts were washed with aqueous sodium bicarbonate solution, dried over magnesium sulphate, evaporated and purified on an SiO2 column, eluting with toluene and evaporating to yield 1.89 (100%) of the title product.

Refractive index n 19 - = 1.5420 D [a] 24 = - 22.40 (C2,CHCL3) D EXAMPLE 2 - Preparation of 1 ,R-cis-2,6-d ich lo robenzyl 2-(2,2-dichlorovinyl)-3,3-dimethylcyclopropane carboxylate 1 ,R-cis-2(2,2-dichlorovinyl)-3,3-dimethyl carboxylic acid (3.5g), 2,6dichlorobenzylchloride (3.0g), potassium iodide (0.5g) and potassium carbonate (2.3g) were stirred together in acetone under reflux for 2 hours. The reaction mixture was treated as in Example 1 to yield 5.6g (1 00%) of the title product.

Refractive index n 2D3 1.5638 D [a] 2D5 = - 26.50 (C2, CHCl3) EXAMPLES 3 TO 11 The following compounds were prepared in similar manner to those of Examples 1 and 2:cis-2,6-dich lorobenzyl 2-(2-chloro-2-fluorovinyl)-3,3-dimethylcyclopropanecarboxylate (86% yield) n D =1.541 D cis-2-chloro-6-fluorobenzyl 2-(2,2-dichlorovinyl)-3,3-dimethylcyclopropanecarboxylate (98% yield) n D =1.5401 trans-2-chloro-6-fluorobenzyl 2-(2,2-dichlorovinyl)-3,3-dimethylcyclopropane carboxylate (98% yield) n 19 = 1.5360 D cis-2-chloro-6-fluorobenzyl 2-(2 ,2-dibromovinyl)-3,3-dinethylcyclopropa ne carboxylate 23 (98% yield) n D = 1.5664 cis-2,6-dichlorobenzyl 2-(2,2-dichlorovinyl)-3,3-dimethylcyclopropane carboxylate (87% yield) m.p.

91-950C cis-2-chloro-6-fluorobenzyl 2-12-ch loro-2-fl uorovinyl)-3,3-dimethylcyclopropane carboxylate 19 (72% yield) n D 1.521 1,R-cis-2-ch loro-6-fluorobenzyl 2-(2,2-difluorovinyl)-3,3-dimethylcyclopropane carboxylate 22 (91% yield) n D = 1.4987, [cr] 2D = -- 9.500 (C2 CHCIB) b 1,R-cis-2-ch loro-6-fluorobenzyl 2-(2,2-dibromovinyl)-3,3-dimethylcyclopropa ne carboxylate 19 (63% yield) n D = 1.565, [a] 2D5 D = - 7.69o (C2 CHCl3) 1::1 -cis/trans-2,6,-d ichlorobenzyl 2-(2,2-dichlorovinyl)-3,3-dimethylcyclopripa ne carboxylate (70% yield) Pesticidal Tests The insecticidal and tickicidal activity of the compounds according to the present invention was assessed employing the following pests: Insects: Musca domestica (M.d.) Spodoptera littoralis (S.l.) Aphis fabae (A.f.) Heliothis zea (H.z.) Mites: Tetranychus urticae (T.u.) Ticks: Boophilus microplus (B.m.) The test methods employed for each species appear bejowl (i) Musca domestica (M.d.) A 0.4% by weight solution in acetone of the compound to be tested was prepared and taken up in a micrometer syringe.Two or three day old adult female houseflies (Musca domestica) were anaesthetised with carbon dioxide, and 1 yl of the test solution was applied to the ventral side of the abdomen of each fly, 20 flies being tested. The treated flies were held in glass jars covered with paper tissue held by an elastic band. Cotton-wool pads soaked in dilute sugar solution were placed on top of the tissue as food. After 24 hours the percentage of dead and moribund flies were recorded.

(ii) Spodoptera littoralis (S.l.) Pairs of leaves were removed from broad bean plants and placed on filter paper inside plastic petri dishes. The leaves were sprayed on the undersurface with an aqueous formulation containing 20% by weight of acetone. 0.05% by weight of TRITON X-100 (Trade Mark) as wetting agent and 0.4% by weight of the compound to be tested. Varying concentrations were obtained by diluting the formulation.

After spraying the leaves were left to 1 hour drying period and then each leaf pair was infested with ten larvae of the Egyptian cotton leafworm (Spodoptera littoralis). After 24 hours the percentage of dead and moribund larvae were recorded.

(iii) Aphis fabae (A.f.) Tests were carried out on adult aphids (Aphis fabae) by similar methods to that used for Spodoptera littoralis in (ii) above.

(iv) Heliothiszea (H.z.) The compounds to be tested were incorporated in aqueous solutions containing 20% by weight of acetone, 0.04% by weight of Atlox 1 045A (Trade Mark) and 0.2% by weight of the test compound, more dilute solutions for dosage-mortality curves being made by diluting the 0.2% solution with an aqueous solution of 0.05% by weight of Atlox 1 045A. Cut Windsor broad bean plants were placed on a turntable and sprayed with 4 ml of test solution.Immediately after spraying, 5 corn earworm larvae (Heliothis zea) were transferred to each plant which was inserted into water through a hole in a test board and the environment was maintained at a temperature of 270C and 4050% relative humidity.

Mortality was assessed after 44 and 56 hours.

(v) Tetranychus urticae (T.u.) Discs were cut from the leaves of French bean plants and were placed on filter paper kept moist by a cotton-wool wick dipping into water. Each disc was infested with ten adult mites, and the discs were then sprayed with a solution or suspension of the test compound in acetone-water (20:80) containing 0.05% of TRITON X-1 00 (Trade Mark) as wetting agent. After 24 hours the percentage of dead and moribund mites was assessed.

(vi) Boophilus microplus (B.m.) A 0.1% by weight solution of the compound to be tested was prepared in acetone containing 10% by weight of polyethylene glycol. Varying concentrations were obtained by diluting this solution. 1 ml of test solution was applied evenly to a filter paper inside a petri dish. When sufficiently dry, the filter paper was folded in half and crimped along part of its outer edge to form a packet. About 80-100 two or three week old one-host cattle tick larvae (Boophilus microplus) were transferred into the packet, which was then competely sealed. The packet was then placed in an incubator at 270C and 80% relative humidity. After 24 hours the packet was opened and the percentage of dead and moribund larvae was assessed.

The results are shown in Table I in which the test species are identified by the initiais noted above and the activity of the compound is expressed in the form of its Toxicity index (T.I.) which is calculated from the following equation:- LCso of ethyl parathion (standard) Toxicity Index (T.l.) = LC50 of test compound The knockdown activity of the compounds according to the invention was assessed employing the common housefly (Musca domestica) by means of the Kearns-March chamber test.

The Kearns-March chamber consists of a 2 foot x 1 foot transparent glass cylinder into which flies can be introduced through a sliding panel at one end.0.2 ml of a 20% MeCI2/80% Shellsol K solution containing active material was sprayed for 12 seconds into the chamber at 10 psi and the air supply kept on for a further two seconds to facilitate even distribution of the spray. About 70 flies were used in each treatment and knockdown counts made at 1, 2, 3,4, 5, 7 and 10 minutes after spraying.

Compounds are graded into six classes according to the concentration of toxicant required to achieve 90% knockdown after ten minutes. that is to say Class 0 90% at 10 minutes = concentration 0.025% Class 1 90% at 10 minutes = concentration 0.05% Class 2 90% at 10 minutes = concentration 0. 1% Class 3 90% at 10 minutes = concentration 0.2% Class 4 90% at 10 minutes = concentration 0.4% Class 5 < 90% at 10 minutes = concentration 0.4% Class 6 No knockdown at 0.4% The results of these tests are also given in Table TABLE I

Compound Toxicity Index Knock of down Example M.d. S.l . A.f. H.z. T.u. B.m. cdloass 1 44 96 26 30 98 908 0 2 44 98 12 28 33 1110 1 3 13 44 5 + 34 1200 2 4 23 41 22 34 72 400 1 5 32 24 9 25 31 57 1 6 14 35 20 53 20 - 2 7 17 107 26 80 61 381 2 8 12 79 29 + 19 482 0 9 17 121 19 19 4 240 1 10 32 137 75 + 10 343 0 11 -21 77 26 + 17 178 2 + not yet tested.

Claims (10)

1. A 2,6-dihalobenzyl ester of formula I:

where Rr and R2 are independently selected from fluoro, chloro and bromo, Y1 is chloro, andY2 iS fluoro or chloro, provided that when R1 and R2 are both bromo Y2 iS fluoro and when neither of R1 and R2 is bromo, at least one of R' and R2 is the same as at least one of Y' and V2.

2. An ester according to Claim 1 wherein R', R2 and V2 are each fluoro or chloro, and V1 is chloro, at least one of R1 and R2 being the same as at least one of Y' and Y2.

3. An ester according to Claim 1 or 2 wherein at least two of R1, R2 and Y are chloro, the other being chloro or fluoro.

4. An ester according to any one of Claims 1 to 3 in the form of its cis-isomers.

5. An ester according to any one of Claims 1 to 3 in the form of its 1,R-cis-isomer.

6. A 2,6-dihalobenzyl ester according to Claim 1 substantially as hereinbefore described in any one of Examples 1 to 11.

7. A process for preparing a 2,6-dihalobenzyl ester of formula I as defined in any one of Claims 1 to 6, which comprises reaction of a compound of formula II:

with a compound of formula III:

where R1, R2, V1 and YZ are as defined in Claim 1, one of Q and Z represents a halogen atom, and the other represents a hydroxy group.

8. A process according to Claim 7 substantially as hereinbefore described in Examples 1 or 2.

9. A 2,6-dihalobenzyl ester prepared by a process according to Claim 7 or 8.

10. A pesticidal composition which comprises a carrier and/or a surface-active agent together with, as active ingredient, a 2,6-dihalobenzyl ester according to any one of Claims 1 to 6 and 9.

ii. A method of combating pests at a locus which comprises applying to the locus a 2,6 dihalobenzyi ester according to any one of Claims 1 to 6 and 9 or a composition according to Claim 10.