GB2257702A - Insecticidal and acaricidal compounds - Google Patents

Abstract

Compounds of formula (I): <IMAGE> or a stereoisomer thereof [wherein R<1> is C1-8 alkyl, C2-8 alkenyl, C3-6 cycloalkyl (optionally substituted with one or more methyl groups), C1-4haloalkyl, halo or tri-(C1-3 alkyl)silyl; R<2> is C4-8 alkyl (in which the carbon atom at the point of attachment exhibits tertiary substitution ie is a quaternary carbon atom), C2-8 alkenyl or 1-methyl-(C3-6 cycloalkyl); R<3> is hydrogen, fluoro, C1-4 alkyl, C1-4 alkoxy or C1-4 alkylthio; and R<4> is hydrogen, fluoro, C1-4 alkyl, C2-4 alkenyl, C1-4 alkynyl, C1-4 alkoxy, C1-4 alkylthio, C2-8 alkoxyalkyl, C2-8 alkylthioalkyl or C2-4 haloalkenyl] exhibit insecticidal and acaricidal activity.

Description

INSECTICIDAL AND ACARICIDAL COMPOUNDS This invention relates to novel insecticidally and acaricidally active esters, to methods for their preparation, to compositions comprising them, and to methods of controlling insect and acarine pests therewith.

In a first aspect the invention provides novel compounds of formula (I); and stereoisomers thereof, wherein R1 is C18 alkyl, C2-8 alkenyl, C3-6 cycloalkyl optionally substituted with one or more methyl groups, C1-4 haloalkyl, halo or tri-(C1 3 alkyl)silyl; R2 is C48 alkyl in which the carbon atom at the point of attachment exhibits tertiary substitution, C2-8 alkenyl or 1-methyl-(C3-6cycloalkyl); R3 is hydrogen, fluoro, C1-4 alkyl, C1-4 alkoxy or C1-4 alkylthio and R4 is hydrogen, fluoro, C1-4 alkyl, C24 alkenyl, C24 alkynyl, C14 alkoxy, C14 alkylthio, C28 alkoxyalkyl, C2-8 alkylthioalkyl or C24 haloalkenyl.

Preferred compounds according to the invention are those of formula (I), or stereoisomers thereof, wherein R1 is C16 alkyl, C2-6 alkenyl, cyclopropyl optionally substituted with a methyl group, cyclohexyl optionally substituted with a methyl group, C1-2 fluoroalkyl or tri-(C1-2 alkyl)silyl and R2 is C46 alkyl, C2-6 alkenyl or 1.methyl-(C3-6cycloalkyl).

Preferred values of R in the compounds of formula (I) and stereoisomers thereof are i-propyl, t-butyl, t-pentyl (1,1-dimethylpropyl), cyclopropyl, 1-methylcyclopropyl, 1-methylcyclohexyl, cyclohexyl, trifluoromethyl and trimethylsilyl.

Preferred values of R2 in the compounds of formula (I) and stereoisomers thereof are t-butyl, t-pentyl, 1-methylcyclopropyl and - 1-methylcyclohexyl.

Preffered values of R in the compounds of formula (I) and stereoisomers thereof are fluorine, hydrogen, methoxy, ethoxy, methylthio and ethylthio.

Preferred values of R4 in the compounds of formula (I) and stereoisomers thereof are hydrogen, fluorine, methoxy, ethoxy, methoxymethyl, ethoxymethyl, methyl, methylthiomethyl, prop-2-en-1-yl, prop-2-yn-1-yl, 3-chloroprop-2-en-l-yl, 2-chloroprop-2-en-1-yl, methylthio and ethylthio.

Particularly preferred compounds according to the invention are those wherein R1 and R2 are independently selected from t-butyl, t-pentyl and 1 -methylcyclopropyl, for example esters of 3,3-dimethyl-2-(4-t-butylphenyl) -butanoic acid and stereoisomers thereof.

Particular examples of compounds according to the invention are those of formula (I), and stereoisomers thereof, having the combinations of values of R1, R2, R3 and R4 as indicated in Table I.

TABLE I COMPOUND R1 R2 R3 R4 NO 1 -C(CH3)3 -C(CH3)3 F CH20CH3 2 " " F CH2CH=CH2 3 " " F CH3 4 " " F CH2C#CH 5 " " F CH2SCH3 6 II lv F CH2CH=CHC1 7 " " F H 8 II " F F 9 lv lv OC2H5 CH20CH3 10 " " OCH3 CH2OCH3 11 " " F SCH3 12 " " CH3 F 13 -C(CH3)2CH2CH3 " F CH2OCH3 14 " lv OCH3 CH2OCH3 15 1 " F CH3 16 " " F CH2C#CH 17 " " F F 18 -C(CH3)3 -C(CH3)2- F CH3 CH2CH3 19 " " F CH2OCH3 20 " lv OCH3 CH2OCH3 21 " " F CH2C#CH TABLE I (continued) COMPOUND R1 R2 R3 R4 NO 22 -C(CH3)3 1-methyl- F CH3 cyclopropyl 23 " F CH20CH3 24 " " OCH3 CH2OCH3 25 vi II F CH2CeCH 26 1-methyl- -C(CH3)3 F CH3 cyclopropyl 27 " " F CH20CH3 28 " vi F CH2CeCH 29 lv OCH3 CH2OCH3 It will be appreciated that compounds of formula (I) exhibit at least one asymmetrically substituted carbon atom, and may exist in more than one isomeric form, such isomers exhibiting differing levels of insecticidal and acaricidal activity. All such isomers, and mixtures thereof, are within the scope of this invention, as are those arising from geometrical isomerism where a compound of the invention exhibits one or more alkenyl groups.

The insecticidally and acaricidally active compounds of the invention according to formula (I) are esters, and may be prepared from the corresponding alkyl esters, acids and acid chlorides by conventional esterification processes, such as those described in (a) to (d) below, by way of example.

(a) An acid of formula (II), where Q represents the hydroxy group and R1 and R2 have any of the meanings given hereinabove, may be reacted directly with an alcohol of formula (III), where R3 and R4 have any of the meanings given hereinabove, the reaction preferably taking place in the presence of an acid catalyst, for example, dry hydrogen chloride, or a dehydrating agent, for example, dicyclohexylcarbodiimide or N-ethyl-N-(3 -dimethylaminopropyl)carbodiimide, the latter being particularly suitable in those cases where R1 represents t-butyl;; (b) An acid halide of formula (II), where Q represents a halogen atom, preferably a chlorine atom, and R1 and R2 have any of the meanings given hereinabove, may be reacted with an alcohol of formula (III), the reaction preferably taking place in the presence of a base, for example, pyridine, alkali metal hydroxide or carbonate, or alkali metal alkoxide;; (c) An acid of formula (II) where Q represents the hydroxy group or, preferably, an alkali metal salt thereof, may be reacted with either (i) a halide of formula (IV), wherein Q represents a halogen atom, preferably the chlorine atom, or with a quaternary ammonium salt derived by reaction of such a halide with a tertiary amine, for example pyridine or trialkylamines such as triethylamine, or (ii) with a compound of formula (IV) wherein Q1 represents a displaceable leaving group, such as the mesylate or tosylate group, and R3 and R4 have any of the meanings given hereinabove.

(d) A lower alkyl ester of formula (II), where Q represents a lower alkoxy group containing up to six carbon atoms, preferably the methoxy or ethoxy group, and R1 and R2 have any of the meanings given hereinabove, is heated with an alcohol of formula (III) to effect a transesterification reaction.

Preferably the process is performed in the presence of a suitable catalyst, for example, an alkali metal alkoxide, such as sodium methoxide, or an alkylated titanium derivative, such as tetramethyl titanate or tetraethyl titanate.

All of these conventional processes for the preparation of esters may be carried out using solvents and diluents for the various reactants where appropriate, and may be accelerated or lead to higher yields of product when performed at elevated temperatures or in the presence of appropriate catalysts, for example phase-transfer catalysts.

Similarly the interconversion of the acid, acid chloride and lower alkyl esters of formula II may be performed using conventional chemical procedures for chlorination, esterification and hydrolysis.

Many of the alcohols of formula (III) are well known in the literature and may be prepared by methods described therein; many others may be prepared by closely analogous procedures.

Thus, for example, the preparation of alkyl-tetrafluorobenzyl alcohols, alkenyl-tetrafluorobenzyl alcohols, alkoxy-tetrafluorobenzyl alcohols, alkylthio-tetrafluorobenzyl alcohols and analogues thereof is described in European Patent Application No. 31199; the preparation of alkynyl-tetrafluorobenzyl alcohols is described in European Patent Application No. 196156; the preparation of alkoxyalkyl-tetrafluoro-benzyl alcohols is described in European Patent Application No. 54360; the preparation of alkoxy-alkoxyalkyl-trifluorobenzyl alcohols is described in UK Patent Application No. 2197317; the preparation of other fluorinated benzylacohols is described in UK Patent Application No. 8726875.

Further examples of the preparation of alcohols useful as intermediates in the preparation of the compounds of formula (I) are given in the Examples hereinafter.

The preparation of individual isomers of the compounds of formula (I) may be carried out in the same manner as described above but commencing from the corresponding individual isomers of compounds of formula II.

These may be obtained by conventional isomer separation techniques from mixtures of isomers. Thus the various optically active species may be obtained by fractional crystallisation of salts of the acids with optically active amines, for example (+)- or (-)-alpha-methylbenzylamine, followed by regeneration of the optically pure acid. The optically pure isomeric form of the acid (or its equivalent acid chloride or ester) may then be reacted with the appropriate alcohol to produce a compound of formula (I) in the form of an individually pure isomer thereof. Where one specific isomer is required, there exists the possibility that the residual isomer or isomer mixture may be epimerised and recycled for further isolation of the required form, thereby improving the overall yield of the required isomer.

Where the compounds of Formula (I) are formed as mixtures of diasteroisomers, racemic pairs can be separated by e.g., h.p.l.c.

techniques, or, where the physical properties of the compounds are suitable, by selective crystallisation.

The acids, acid halides and simple esters of formula (II) wherein R2 has any of the meanings given hereinbefore other than 1-methylcyclopropyl or may be prepared by the general process illustrated in Scheme I. Those compounds of formula (II) wherein R2 is 1-methylcyclopropyl may be prepared by the general process in Scheme II.

Alternative routes suitable for specific values of R may be more appropriate than the general routes mentioned hereinbefore. Choice of the most suitable route is within the normal skill of the art. An example of a particular route is shown in Scheme III.

Further details of preparative routes are given in the Examples.

The compounds of formula (I) may be used to combat and control infestations of insect and acarine pests. The insect and acarine pests which may be combated and controlled by the use of the invention compounds include those pests associated with agriculture (which term includes the growing of crops for food and fibre products, horticulture and animal husbandry), forestry, the storage of products of vegetable origin, such as fruit grain and timber, and also those pests associated with the transmission of diseases of man and animals.

In order to apply the compounds to the locus of the pests they are usually formulated into compositions which include in addition to the insecticidally active ingredient or ingredients of formula (I) suitable inert diluent or carrier materials, and/or surface active agents.

The compounds of the invention may be the sole active ingredient of the composition or they may be admixed with one or more additional active ingredients such as insecticides, insecticide synergists, herbicides, fungicides or plant growth regulators where appropriate.

Suitable additonal active ingredients for inclusion in admixture with the compounds of the invention may be compounds which will broaden the spectrum of activity of the compounds of the invention or increase their persistence in the location of the pest. They may synergise the activity of the compounds of the invention or complement the activity, for example by increasing the speed of effect, improving kill or knockdown of target insect pests, or overcoming repellency. Additionally, multi-component mixtures of this type may help to overcome or prevent the development of resistance to individual components.

The particular insecticide, herbicide or fungicide included in the mixture will depend upon its intended utility and the type of complementary action required. Examples of suitable insecticides include the following: (a) natural pyrethrins or pyrethroids such as permethrin, fenvalerate, deltamethrin, cyhalothrin, biphenthrin, fenpropathrin, cyfluthrin, tefluthrin, empenthrin, ethofenprox, tetramethrin, bioallethrin, fenfluthrin, prallethrin, 5-benzyl-3-furylmethyl (E)-(lR,3S)-2,2-dimethyl-3-(2-oxothiolan-3-ylidenemethyl)cyclopropane carboxylate and pentafluorobenzyl (cis )-3- 2-fluoro-2-(methoxycarbonyl)ethenyl]-2, 2-dimethylcyclopropane carboxylate;; (b) organophosphates such as profenofos, sulprofos, dichlorvos, methyl parathion, azinphos-methyl, demeton-s-methyl, heptenophos, thiometon, fenamiphos, monocrotophos, triazophos, methamidophos, dimethoate, phosphamidon, malathion, chlorpyrifos, phosalone, fensulphothion, fonofos, phorate, phoxim, pyrimiphos-methyl, fenitrothion and diazinon; (c) carbamates (including aryl carbamates) such as pirimicarb, cloethocarb, carbofuran, ethiofencarb, aldicarb, thiofurox, carbosulfan, bendiocarb, fenobucarb, propoxur and oxamyl; (d) benzoyl ureas such as triflumuron and chlorofluazuron; (e) organic tin compounds such as cyhexatin, fenbutatin oxide and azocyclotin; (f) macrolides such as avermectins or milbemycins, for example abamectin, avermectin and milbemycin; (g) hormones and synthetic mimics thereof such as juvenile hormone, juvabione, ecdysones, methoprene and hydroprene; (h) pheromones;; (i) organochlorine compounds such as benzene hexachloride, DDT, chlordane, dieldrin and endosulfan.

In addition to the major chemical classes of insecticide listed above, other insecticides having particular targets may be employed in the mixture if appropriate for the intended utility of the mixture. For instance selective insecticides for particular crops, for example stem borer specific insecticides for use in rice such as cartap or buprofezin, can be employed. Alternatively, insecticides or acaricides specific for the control of specific insect growth stages, for example ovolarvicides such as clofentezine, amitraz, chlordimeform, flubenzimine, hexythiazox and tetradifon; motilicides such as dicofol or propargite; adulticides such as bromopropylate, chlorobenzilate; or insect growth regulators such as hydramethylnon, cyromazine, methoprene, chlorfluazuron and diflubenzuron may also be included in the compositions.

Examples of suitable insecticide synergists for use in the compositions include piperonyl butoxide, sesamex and dodecyl imidazole.

Suitable herbicides, fungicides and plant growth regulators for inclusion in the compositions will depend upon the intended target and the effect required. An example of a rice-selective herbicide which can be included is propanil; an example of a plant growth regulator for use in cotton is "Pix"; and examples of fungicides for use in rice include blasticides such as blasticidin-S. The choice of other ingredients to be used in admixture with the active ingredient will often be within the normal skill of the formulator, and will be made from known alternatives depending upon the total effect to be achieved.

The ratio of the compound of the invention to any other active ingredient in the composition will depend upon a number of factors including the type of insect pest to be controlled, and the effects required of the mixture. However, in general, the additional active ingredient of the composition will be applied at about the rate at which it would be applied on its own, or at a lower rate if synergy occurs.

The compositions may be in the form of dusting powders wherein the active ingredient is mixed with a solid diluent or carrier, for example kaolin, bentonite, kieselguhr or talc, or they may be in the form of granules wherein the active ingredient is absorbed in a porous granular material, for example pumice.

Alternatively, the compositions may be in the form of liquid preparations to be used as dips, sprays or aerosols. Dips and sprays are generally aqueous dispersions or emulsions of the active ingredient in the presence of one or more known wetting agents (surface active agents).

Aerosol compositions may contain the active ingredient or ingredients, a propellant and an inert diluent, for example odouless kerosene or alkylated benzenes. In a preferred form, aerosol compositions may contain from 0.005% to 4% of active ingredient or ingredients, the remainder of the composition comprising a solvent, selected from odouless kerosene and alkylated benzenes, and a propellant. Aerosol compositions may optionally incorporate other additives, for example perfumes or corrosion inhibitors.

Wetting agents, dispersing agents and emulsifying agents may be of the cationic, anionic or non-ionic type. Suitable agents of the cationic type include, for example, quaternary ammonium compounds, for example cetyltrimethylammonium bromide. Suitable agents of the anionic type include, for example, soaps, salts of aliphatic monoesters of sulphuric acid, for example sodium lauryl sulphate, salts of sulphonated aromatic compounds, for example sodium dodecylbenzenesulphonate, sodium lignosulphonate, calcium lignosulphonate, ammonium lignosulphonate, butylnaphthalenesulphonate and a mixture of the sodium salts of diisopropyl- and triisopropyl naphthalenesulphonates.Suitable agents of the non-ionic type include, for example, the condensation products of ethylene oxide with fatty alcohols such as oleyl alcohol or cetyl alcohol, or with alkyl phenols such as octyl phenol, nonyl phenol and octyl cresol.

Other non-ionic agents are the partial esters derived from long chain fatty acids and hexitol anhydrides, the condensation products of the said partial esters with ethylene oxide, and the lecithins.

The compositions may be prepared by dissolving the active ingredient in a sutiable solvent, for example a ketonic solvent such as diacetone alcohol, or an aromatic solvent such as trimethylbenzene, and optionally adding the mixture so obtained to water which may contain one or more known wetting, dispersing or emulsifying agents.

Other suitable organic solvents are dimethylformamide, ethylene dichloride, isopropyl alcohol, propylene glycol and other glycols, diacetone alcohol, toluene, kerosene, white oil, methylnaphthalene, xylenes, trichloroethylene, N-methyl-2-pyrrolidinone and tetrahydrofurfuryl alcohol (THFA).

The compositions which are to be used in the form of aqueous dispersions or emulsions are generally supplied in the form of a concentrate containing a high proportion of the active ingredient or ingredients, the said concentrate to be diluted with water before use.

These concentrates are often required to withstand storage for prolonged periods and, after such storage, to be capable of dilution with water to form aqueous preparations which remain homogeneous for a sufficient time to enable them to be applied by conventional spray equipment. The concentrates may contain 1-99% by weight of the active ingredient or ingredients. When diluted to form aqueous preparations, such preparations may contain varying amounts of the active ingredient depending upon the purpose for which they are to be used. For agricultural or horticultural purposes, an aqueous preparation containing between 0.0001% and 0.1X by weight of the active ingredient or ingredients is particularly useful.In use, the compositions are applied to the pests, to the locus of the pests, to the habitat of the pests, or to growing plants liable to infestation by the pests, by any of the known means of applying pesticidal compositions, for example by dusting or spraying or in a granular formulation.

The compounds of formula (I) and compositions comprising them are very toxic to a variety of insect, acarine and other invertebrate pests, including, for example, the following: Myzus persicae (aphid) Aphis gossypii (aphid) Aphis fabae (aphid) Megoura viceae (aphid) Aedes aegypti (mosquito) Anopheles spp. (mosquitos) Culex spp. (mosquitos) Dysdercus fasciatus (capsid) Musca domestica (housefly) Pieris brassicae (white butterfly) Plutella maculipennis (diamond back moth) Phaedon cochleariae (mustard beetle) Aonidiella spp. (scale insects) Trialeuroides spp. (white flies) Bemisia tabaci (white fly) Blattella germanica (cockroach) Periplaneta americana (cockroach) Blatta orientalis (cockroach) Spodoptera littoralis (cotton leafworm) Heliothis virescens (tobacco budworm) Chortiocetes terminifera (locust) Diabrotica spp. (rootworms) Agrotis spp. (cutworms) Chilo partellus (maize stem borer) Nilaparvata lugens (planthopper) Nephotettix cincticeps (leafhopper) Panonychus ulmi (European red mite) Panonychus citri (citrus red mite) Tetranychus urticae (two-spotted spider mite) Tetranychus cinnabarinus (carmine spider mite) Phyllcoptruta oleivora (citrus rust mite) Polyphagotarsonemus latus (broad mite) Brevipalpus spp. (mites) Many of the compounds of formula (I) have shown especially high levels of activity towards tetranychid mites, such as Tetranychus species (for Example Tetranychus urticae) and Panonychus species (for Example Panonychus ulmi, in a variety of laboratory test systems. In particular, the compounds show high levels of activity against the egg stage as well as all older life stages of such mites.

All of the compounds which have been tested have shown no cross-resistance to lambda-cyhalothrin or bifenthrin in a strain of Panonychus ulmi tolerant to lambda-cyhalothrin and bifenthrin.

The compounds of formula (I) may also be useful in combating insect and acarine pests which infest domestic animals, such as Lucilia sericata, and ixodid ticks such as Boophilus spp., Ixodes spp., Amblyomma spp., Rhipicephalus spp. and Dermocentor spp. They are effective in combating both susceptible and resistant strains of these pests in their adult, larval and intermediate stages of growth, and may be applied to the infested host animal by topical, oral or parenteral administration.

The following Examples illustrate various aspects of this invention.

In the preparation Examples the products were usually identified and characterised by means of nuclear magnetic reasonance spectroscopy (NMR) and infra red (IR) spectroscopy. In each case where a product is specifically named its spectral characteristics are consistent with the assigned structure. Except where stated otherwise, exemplified compounds having one or more asymmetrically substituted carbon atoms were prepared in racemic form.

In the Examples, Gas Liquid Chromatography (GLC) retention times were determined on a Hewlett Packard 5890 Gas Chromatograph, using a Chromopak, C.P. Sil 5 C.B column of 12.5 m length and 0.2mm internal diameter. Unless otherwise stated, the injection temperature was 1000C, and a temperature gradient of 150C/minute employed, up to a maximum temperature of 2800C, maintained for 4 minutes. The carrier gas was helium at a column head pressure maintained at 11 psi. Alternative injection and maximum temperature are indicated in the Examples where appropriate.

1H Nuclear Magnetic Resonance (NMR) spectrometry was performed at a frequency of 270 MHz on a Jeol FX 270 NMR spectrometer, unless otherwise indicated. 90 MHz, 60 MHz, 250 MHz and 400 MHz 1H NMR spectrometry were performed using Jeol FX 90 Q, Brucker WH90, Jeol PMX 60 SI, Brucker WM250, and Jeol GX 400 spectrometers.

19F NMR spectrometry was performed on a Jeol FX90Q spectrometer at a frequency of 84.26 MHz. All NMR shift values () are quoted in ppm relative to a standard (TMS or CFC13). In the NMR data, the following abbreviations are used: - s = singlet, d=doublet, t=triplet, q=quartet, dd=double doublet, m=multiplet, b=broad.

Molecular Ion (M+) peaks were determined on one of three mass spectrometers: Jeol DX 303, Kratos MS80 or Hewlett Packard HP 5992.

EXAMPLE 1 4-(1,1-Dimethylethyl)phenyl acetic acid (4.0g) was dissolved in acetone (50cm3) containing methyl iodide (2cm3) and anhydrous potassium carbonate (3g). The mixture was stirred and heated at the reflux temperature for 4 hours. The reaction mixture was cooled and the acetone and excess methyl iodide evaporated under reduced pressure. The residue was treated with diethyl ether (ca 150cm3) and water (100cm3). The ethereal fraction was separated, dried over anhydrous magnesium sulphate and the solvent evaporated under reduced pressure to yield a red-brown oil.

The oil was distilled at ca 15mm Hg to yield methyl 4-(1,1 dimethylethyl)phenyl acetate as a colourless liquid (3g).

EXAMPLE 2 Methyl 4-(1,1,-dimethylethyl)phenyl acetate (0.92g) was dissolved in dry toluene (5cm3; dried by 4A molecular sieves) containing triethylamine (0.60g; dried by storing over potassium hydroxide) under a dry nitrogen atmosphere. The solution was stirred at OOC and trimethylsilyl trifluoromethanesulphonate (Aldrich Chemical Company; 0.85cm3) was added in portions. On complete addition the reaction mixture was stirred at OOC for 3 hours. The toluene layer was separated and the solvent evaporated under reduced pressure to leave a colourless oil, (ca lg).

The oil was redissolved in dichloromethane (dried by 4A molecular sieves; 5cm3) and treated with 1,1-dimethylethyl chloride (0.41g) and anhydrous zinc chloride (0.30g) at the ambient temperature. The reaction mixture was stirred under a dry nitrogen atmosphere for 3 hours, and stored for a further 18 hours. The mixture was treated with water and extracted with ethyl acetate. The ethyl acetate fraction was dried with anhydrous magnesium sulphate and evaporated under reduced pressure to give a yellow oil, (0.90g). The yellow oil was fractionated using HPLC (Dupont Zorbax SIL 100 25cm x 21mm diameter column; eluting with n hexane/ethyl acetate, 10:1 by volume) to give methyl 2-[4-(1,1-dimethylethyl)phenyl]-3,3 -dimethyl)butanoate as a colourless oil (0.06g).

1H NMR (CDC13) (60MHz) 6 1.0(s,9H); 1.35(s,9H); 3.40(s,1H); 3.65(s,3H); 7.35(s,4H).

GLC retention time: 4.60 minutes MS M+ 262 (weak), M-56 206.

EXAMPLE 3 Methyl 2-[4-(1,1-dimethylethyl)phenyl]-3,3-dimethyl butanoate (0.055g) was dissolved in propan-2-ol (3cm3) containing sodium hydroxide (0.025g).

The mixture was stirred and heated to reflux for 6 hours, cooled, poured into water (10cm3) and acidified to pH2-3 using 2M hydrochloric acid. The acidified mixture was extracted with ethyl acetate (2x25cm3) and the ethyl acetate fraction dried with anhydrous magnesium sulphate. The solvent was evaporated under reduced pressure to yield 2-[4-(1,1-dimethylethyl -phenyl]-3,3-dimethylbutanoic acid as an off-white solid (0.03g).

CLC Retention time: 5.38 minutes.

EXAMPLE 4 4-Methoxymethyl-2,3,5, 6-tetrafluorobenzyl alcohol (0.033g) was dissolved in dichloromethane (dried by 4A molecular sieves; 1cm3) and treated with triethylamine (dried by storing over potassium hydroxide; 21p1) and methanesulphonyl chloride (12us) at the ambient temperature. The mixture was stored for 18 hours at the ambient temperature and the dichloromethane evaporated under reduced pressure. The residual oil, containing a mixture of 4-methoxymethyl-2,3,5,6-tetrafluorobenzyl chloride and 4-methoxymethyl-2,3,5,6-tetrafluorobenzyl methane sulphonate was dissolved in acetone (2cm ), and 2-[4-(1,1 -dimethylethyl)phenyl]-3,3-dimethyl butanoic acid (0.035g) and anhydrous potassium carbonate (0.05g) added.The mixture was stirred and heated to reflux for 4 hours. To the partially reacted mixture was added potassium iodide (ca 0.05g) and the heating continued for a total of 10 hours. The acetone was evaporated under reduced pressure, and the residue treated with water and extracted with diethyl ether (3x50cm3). The etheral fractions were combined, dried with anhydrous magnesium sulphate, and evaporated under reduced pressure to give an oil. The oil was fractionated by eluting through a short column of silica gel (Merck 7729) using a mixture of n-hexane and ethyl acetate (25:1 by volume), to give 4-methoxymethyl-2,3,5 ,6-tetrafluorobenzyl 2-[4-(1,1-dimethylethyl)phenyl]-3, 3-dimethylbutanoate (0.05g), Compound No. 1.

1H NMR (CDC13) (270MHz) b 0.95(s,9H); 1.30(s,9H); 3.40 (s,3H); 3.42(s,1H); 4.58(m,2H); 5.05-5.30(m,2H); 7.28(s,4H).

MS (Chemical ionisation, NH3) MN+H4 472 EI M+454 (v. weak), (M-56,398).

EXAMPLE 5 This Example illustrates the insecticidal properties of the Products of this invention.

The activity of the Product was determined using a variety of insect pests. The Product was used in the form of liquid preparations containing 500, 250 or 100 parts per million (ppm) by weight of the Product. The preparations were made by dissolving the Product in acetone and diluting the solutions with water containing 0.01% by weight of a wetting agent sold under the trade name "SYNPERONIC" NX until the liquid preparations contained the required concentration of the Product. "SYNPERONIC" is a Registered Trade Mark.

The test procedure adopted with regard to each pest was basically the same and comprised supporting a number of the pests on a medium which was usually a host plant or a foodstuff on which the pests feed, and treating either or both the pests and the medium with the preparations. The mortality of the pests was then assessed at periods usually varying from one to three days after the treatment.

In the case of the species Musca domestica (housefly), additional tests to determine the knockdown effect of the compounds were performed.

Details are given in Table II.

The results of the tests are given in Table III for each of the Products, at the rate in parts per million given in the second column as a grading of mortality designated as A, B or C wherein A indicates 80-100% mortality or knockdown, B indicates 50-79% mortality or knockdown and C indicates less than 50% mortality or knockdown.

In Table III the pest organism used is designated by a letter code and the pests species, the support medium or food, and the type and duration of test is given in Table II.

TABLE II CODE LETTERS TEST SPECIES SUPPORT TYPE OF DURATION (Table III) MEDIUM/FOOD TEST (days) TUa Tetranychus urticae French bean Contact 3 (spider mites - adult) leaf TUe Tetranychus urticae French bean Contact 6 (spider mites - ova) leaf MP Myzus persicae Chinese Contact 3 (aphids) Cabbage leaf NC Nephotettix cincticeps Rice plant Contact 2 (green leaf hopper nymphs) HV Heliothis virescens Cotton leaf Residual 2 (tobacco budworm larvae) DB Diabrotica balteata Filter paper/ Residual 2 (rootworm larvae) maize seed SP Spodoptera exiqua Cotton leaf Residual 2 (lesser army worm larvae TABLE III COMPOUND RATE TUa TUc MP NC HV DB NO ppm 1 100 A C A A C A EXAMPLE 6 This Example illustrates the acaricidal properties of the compounds according to the invention.

French bean plants were grown to the two-leaf stage and the growing tips were then removed. The plants were held in plastic containers and infested with adult Tetranychus urticae by placing pieces of infested culture leaf on the surface of the test plant leaves, onto which the mites move as the culture leaf fragment dries out. 24 hours after infestation, leaf discs were cut from the infested plants, and placed with their lower surfaces uppermost on cooled agar bases contained in plastic monopots. The monopots were immediately transferred to a Potter Tower for spraying with 1 cm3 of each test composition per monopot. Immediately after spraying, netted plastic rings were placed on the leaf discs to retain the mites.

The leaf discs were held at 250C for 3 days, and the mortality of the mites assessed visually.

The test compositions were prepared by dissolving the test chemicals in a solvent comprising a 1:1 mixture of ethanol and acetone, and diluting the solution with deionised water containing a standard wetting agent until the required concentration (i.e. application rate when sprayed) was obtained. Each test chemical was applied at a range of five application rates. Five test compositions containing a standard commercial acaricide (bifenthrin) at a range of application rates were prepared in a similar way. An untreated control was included in the test to monitor background mortality. The relative potency of each test chemical compared to the standard was calculated by comparison of parallel dose response lines fitted to the mortality observations, using a statistical analysis microcomputer programme.By this procedure, the relative potency of Compound No. 1 compared with the standard, bifenthrin was found to be 1.6.

CHEMICAL FORMULAE (in description)

Scheme I

R1/\CH2CO2R (R=lower alkyl, eg methyl or - ethyl, prepared according to the procedure described in Journal CF3C020-Si(CH3)3 of the American Chemical Society, 105 (7), 1986 (1983)).

C2H5)3 1 /0R CH= C - 0Si(CH3)3 1. 1- R2-X/ZnC12 (X=C1 or OCOCH3) 2. H20/H+ R1 z lC2H-C02R R (II, Q=lower alkoxy) Hydrolysis RlRC1HCO2H (11, Q = OH) l SOC12 R1 4 CH-COC1 (II, Q = Cl) Scheme II

Mg/THF 2~CHO | R C2H5 ) R2 -CHO I I I R1 o CH ( . R1 o JH~OH SOC12 (X=OS02CH3 or C1) KCN or NaCN DMSO V R12 H2S04 R2 0 R1 CH-CN I R1C1H- C11-NH2 NaN02/H20/H2S04 or on CF3CO2 R2 Esterify R2 I I R1 9 CH-CO2R ROH (R=lower alkyl) R1 d H-C02H (II, Q = lower alkoxy) / (it, Q = OH) S;Cl2 R2 R1 < H-COC1 (Il, Q = C1) Scheme III

(CH3)2C C(CH3)2 RlseH2~C02R < R1 - C-CO2R ZnCl2 (R = lower alkyl) 1. LiN(i-Pr)2 or LiNSi(CH3)3]2 2. H20/H+ /CH\2 CH - C CH2 CH2I2 C(CH3)2 R1Ci7CH2 Zn/Cu -Co2R N 2 C02R (II, Q = lower alkoxy R = 1-methylcyclopropyl)

Claims (4)

1. CLAIMS 1. A compound of formula (I):

   or a stereoisomer thereof, wherein R1 is C1-8 alkyl, C2-8 alkenyl, C3-6 cycloalkyl optionally substituted with one or more methyl groups, C1-4 haloalkyl, halo or tri-(C1 3 alkyl)silyl; R2 is C48 alkyl in which the carbon atom at the point of attachment exhibits tertiary substitution, C2-8 alkenyl or 1-methyl-(C3 6 cycloalkyl); R3 is hydrogen, fluoro, C1-4 alkyl, C1-4 alkoxy or C1-4 alkylthio; and R4 is hydrogen, fluoro, C1-4 alkyl, C2-4 alkenyl, C24 alkynyl, C14 alkoxy, C1-4 alkylthio, C2-8 alkoxyalkyl, C2-8 alkylthioalkyl or C2-4 haloalkenyl.
2. 2. A process for the preparation of a compound of formula (I) as claimed in claim 1, wherein (a) an acid of formula (II):

   wherein Q is hydroxy and R1 and R2 have any of the meanings given in claim 1, is reacted with an alcohol of formula (III):

   wherin R3 and R4 have any of the meanings given in claim 1, the reaction taking place in the presence of an acid catalyst or a dehydrating agent; or (b) an acid halide of formula (II) wherein Q represents a halogen atom, is reacted with an alcohol of formula (III): or (c) an acid of formula (II) wherein Q represents hydroxy, or an alkali metal salt thereof, is reacted with either (i) a halide of formula (IV)

   wherein Q represents a halogen or a quaternary ammonium salt derived by reaction of such a halide with a tertiary amine, or (ii) a compound of formula (IV) wherein Q represents the mesylate or tosylate group: or (d) a lower alkyl ester of formula (II) wherein Q represents a lower alkoxy group containing up to six carbon atoms is heated with an alcohol of formula (III) to effect a transesterification reaction.
3. 3. An insecticidal or acaricidal composition comprising an insecticidally or acaricidally effective amount of a compound as claimed in claim 1 in association with an inert diluent or carrier.
4. 4. A method of controlling insect or acarine pests at a locus which comprises applying to the locus an insecticidally or acaricidally effective amount of a composition as claimed in claim 3.