GB2282539A - Normonylmethylethers and thioethers as herbicides - Google Patents

Abstract

A herbicial composition comprising a compound of formula (I) in admixture with a herbicidally acceptable carrier or diluent <IMAGE> wherein X is O or S and R<1> is an alkyl, alkenyl, alkynyl, cycloalkyl, aryl, aralkyl or heterocyclyl group, each group being optionally substituted.

Description

HERBICIDAL COMPOSITIONS This invention relates to herbicidal compositions and processes utilising them.

A number of derivatives of monic acid are known to have utility as biologically active compounds for use in human and veterinary medicine.

Such compounds are described inter alia in J. Med. Chem., 1989, 32, 151, the disclosure of which is incorporated by reference.

We have now found that compounds such as those disclosed in the above references have herbicidal activity.

Thus according to the present invention there is provided a herbicial composition comprising a compound of formula (I) in admixture with a herbicidally acceptable carrier or diluent, wherein X is O or S and R1 is an optionally substituted alkyl, optionally substituted cycloalkyl, optionally substituted aryl, optionally substituted aralkyl or optionally substituted heterocyclyl group.

Optionally substituted C1-10 alkyl groups, optionally substituted C37 cycloakyl groups, optionally substituted C2-10 alkenyl groups and optionally substituted C2-10 alkynyl groups are preferred. Optional substituents which may be present in optionally substituted alkyl, alkenyl or alkynyl groups include C37 cycloalkyl, C1 lO alkoxy, C1~lO alkylthio, C28 alkenyloxy, C2 8 alkenylthio, C2-8 alkynyloxy, C2-8 alkynylthio, halogen, halo-C1-10 alkoxy, halo-C28 alkenyloxy, halo-C28 alkynyloxy, carboxy, C1-6 alkoxycarbonyl, carbamoyl, aryl (which may itself be optionally substituted), aryloxy (which may itself be optionally substituted), aralkyl (which may itself be optionally substituted), aralkyloxy (which may itself be optionally substituted), heterocyclyl (which may itself be optionally substituted), heterocyclyloxy (which may itself be optionally substituted), hydroxy, cyano, nitro, C1-6 alkanoyloxy, amino, mono- and di-(C1 6) alkylamino.

The term aryl as used herein includes phenyl and naphthyl each of which may be optionally substituted with up to five substituents independently selected from halogen, C16 alkyl, C1-6 alkoxy, C16 alkylthio, halo-(C1 6) alkyl, hydroxy-(C1 6) alkyl, halo-(C1 6) alkoxy, C2-8 alkenyl, C28 alkenyloxy, C2-8 alkenylthio, C28 alkynyl, C2-8 alkynyloxy, C2-8 alkynylthio, hydroxy, cyano, nitro, amino, mono- and di (C1.6) alkylamino, C16 alkanesulphinyl, C1 6 alkanesulphonyl, carboxy, C16 alkoxycarbonyl, C1 6 alkoxycarbonyl(C1 6)alkyl, methylenedioxy, aryl (which may itself be substituted), aryloxy (which may itself be substituted), C14 aralkyloxy (which may itself be substituted), heterocyclyl (which may itself be substituted), or heterocyclyloxy (which may itself be substituted).

The term "aralkyl" as used herein includes groups in which the aryl moiety is a phenyl group which may be optionally substituted as hereinbefore defined for aryl and in which the alkylene radical has from 1 to 4 carbon atoms. A preferred aralkyl group is optionally substituted benzyl.

The term heterocyclyl as used herein includes aliphatic or aromatic single or fused rings, each ring containing a total of from 3 to 8 ring atoms and containing up to four hetero atoms in the ring selected from oxygen, nitrogen and sulphur and optionally substituted with aryl (which may itself be substituted), with another heterocyclic ring (which may itself be substituted) or with one or more of those substituents mentioned above as optional substituents for aryl. Examples of suitable heterocyclyl rings for use in the present invention include fur-3-yl, thienyl, pyrrolyl, benzofuranyl, benzthienyl, indolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, pyrazolyl, benzimidazolyl, oxadiazolyl, thiadiazolyl, triazolyl, tetrazolyl, thiatriazolyl, pyrid-3-yl, pyrid-4-yl, qunolinyl, isoquinolinyl, pyrazinyl, pyrimidinyl, pyridazinyl and triazinyl.

Compounds which are preferred for use in the compositions of the present invention are those in which R1 is a C1-10 alkyl group, particularly when substituted with a C1-10 alkoxy, C1-10 alkylthio, C16 alkoxycarbonyl or aralkyloxy group.

Examples of particularly suitable compounds for use in compositions of the present invention are listed in Table I.

TABLE 1 Compound X R1 Number 1 0 -CH2CH20CH3 0 O -(CH2)8C(SCH3)3 3 0 -(CH2)8C6H5 4 0 -CH2CH2OCH2C6H5 5 0 -(CH2)8C02CH3 6 S -CH2CH2OCH:CH2 7 5 -CH2CH20CH2C6H5 Compounds for use in the present invention are either known compounds or may be prepared by methods analogous to those used for the preparation of corresponding known compounds. Several suitable methods of preparation of the compounds for use in the composition of the present invention are described in the literature.

Compounds of Formula (I) may be prepared by the the generalised routes set out in Schemes 1 and 2. In general, however, compounds of Formula (I) may be obtained from protected compounds similar to Compounds 11 to 15, 19 and 20 in which the hydroxyl groups of the molecule are protected by a silyl protecting group such as t-butyldimethylsilyl group. Protected compounds of this type may be deprotected by reaction with, for example, tetrabutylammonium fluoride (TBAF).

When X is oxygen, the protected compounds just described may be prepared directly from Compound 10 as shown in Scheme 1 by reaction with a compound R1I wherein R1 is as defined for formula (I). These compounds are readily available or may be prepared by methods known to those skilled in the art.

When X is sulphur, the protected derivative of compound of formula (I) cannot be prepared directly from Compound 10. In this case, it is preferable to react Compound 10 with a halogenating agent such as lithium chloride and/or methanesulfonyl chloride in the presence of a mild base such as tri ethyl amine to give the halogenated derivative exemplified by the chloro derivative, Compound 16. The halogenated compound may then be reacted with a compound of the formula: NaSR1 to give protected compounds such as Compounds 19 and 20.

Compound 10 is known in the art and may be prepared by known methods such as the method described in J. Med. Chem., 1989, 32, 151.

The compounds for use in the compositions of the present invention are active against a broad range of weed species including monocotyledonous and dicotyledonous species. Many compounds show good selectivity in crops, particularly wheat, barley, maize, oil seed rape, sugar beet and rice. The compounds for use in compositions of the present invention are preferably applied directly to unwanted plants (post-emergence application) but they may also be applied to the soil before the unwanted plants emerge (pre-emergence application).

Thus acording to a further aspect of the present invention there is provided a process of severely damaging or killing unwanted plants1 which comprises applying to the plants or the the growth medium of the plants a herbicidally effective amount of a compound of the formula (I) as hereinbefore defined wherein R1 is as hereinbefore defined.

Novel compounds of the present invention are preferably used in the form of a composition comprising a compound of formula (I) in admixture with a carrier comprising a solid or liquid diluent.

Suitable compositions of the present invention include both dilute compositions, which are ready for immediate use, and concentrated compositions, which require to be diluted before use, usually with water.

Preferably the compositions contain from 0.01% to 90% by weight of the active ingredient. Dilute compositions ready for use preferably contain from 0.01 to 2% of active ingredient, while concentrated compositions may contain from 20 to 90% of active ingredient, although from 20 to 70% is usually preferred.

The solid compositions may be in the form of granules, or dusting powders wherein the active ingredient is mixed with a finely divided solid diluent, e.g. kaolin, bentonite, kieselguhr, dolomite, calcium carbonate, talc, powdered magnesia, Fuller's earth and gypsum. They may also be in the form of dispersible powders or grains, comprising a wetting agent to facilitate the dispersion of the powder or grains in liquid. Solid compositions in the form of a powder may be applied as foliar dusts.

Liquid compositions may comprise a solution or dispersion of an active ingredient in water optionally containing a surface-active agent, or may comprise a solution or dispersion of an active ingredient in a water-immiscible organic solvent which is dispersed as droplets in water.

Surface-active agents may be of the cationic, anionic, or non-ionic type or mixtures thereof. The cationic agents are, for example, quaternary ammonium compounds (e.g. cetyltrimethylammonium bromide). Suitable anionic agents are soaps; salts of aliphatic mono ester of sulphuric acid, for example sodium lauryl sulphate; and salts of sulphonated aromatic compounds, for example sodium dodecylbenzenesulphonate, sodium,calcium, and ammonium lignosulphonate, butylnaphthalene sulphonate, and a mixture of the sodium salts of diisopropyl and triisopropylnaphthalenesulphonic acid.

Suitable non-ionic agents are the condensation products of ethylene oxide with fatty alcohols such as oleyl alcohol and cetyl alcohol, or with alkylphenols such as octyl- or nonyl- phenol (e.g. Agral 90) or octyl-cresol. Other non-ionic agents are the partial esters derived from long chain fatty acids and hexitol anhydrides, for example sorbitan monolaurate; the condensation products of the partial ester with ethylene oxide; the lecithins; and silicone surface active agents (water soluble surface active agents having a skeleton which comprises a siloxane chain e.g. Silwet L77). A suitable mixture in mineral oil is Atpius 411F.

The aqueous solutions or dispersions may be prepared by dissolving the active ingredient in water or an organic solvent optionally containing wetting or dispersing agent(s) and then, when organic solvents are used, adding the mixture so obtained to water optionally containing wetting or dispersing agent(s). Suitable organic solvents include, for example, ethylene dichloride, isopropyl alcohol, propylene glycol, diacetone alcohol, toluene, kerosene, methylnaphthalene, the xylenes and trichloroethyl ene.

The compositions for use in the form of aqueous solutions or dispersions are generally supplied in the form of a concentrate containing a high proportion of the active ingredient, and the concentrate is then diluted with water before use. The concentrates are usually required to withsta1jd 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. Concentrates conveniently contain 20-90%, preferably 20-70%, by weight of the active ingredient(s). Dilute preparations ready for use may contain varying amounts of the active ingredient(s) depending upon the intended purpose; amounts of 0.01% to 10.0% and preferably 0.1% to 2%, by weight of active ingredient(s) are normally used.

A preferred form of concentrated composition comprises the active ingredient which has been finely divided and which has been dispersed in water in the presence of a surface-active agent and a suspending agent.

Suitable suspending agents are hydrophilic colloids and include, for example, polyvinylpyrrolidone and sodium carboxymethylcellulose, and the vegetable gums, for example gum acacia and gum tragacanth. Preferred suspending agents are those which impart thixotropic properties to, and increase the viscosity of the concentrate. Examples of preferred suspending agents include hydrated colloidal mineral silicates, such as montmorillonite, beidellite, nontronite, hectorite, saponite, and saucorite. Bentonite is especially preferred. Other suspending agents include cellulose derivatives and polyvinyl alcohol.

The rate of application of the compounds of the invention will depend on a number of factors including, for example, the compound chosen for use, the identity of the plants whose growth is to be inhibited, the formulations selected for use and whether the compound is to be applied for foliage or root uptake. As a general guide, however, an application rate of from 0.0001 to 20 kilograms per hectare is suitable while from 0.001 to 10, for example 0.001 to 2 kilograms per hectare may be preferred.

The compositions of the invention may comprise, in addition to one or more compounds of the invention, one or more compounds not of the invention but which possess biological activity. Accordingly in yet a still further embodiment the invention provides a herbicidal composition comprising a mixture of at least one herbicidal compound of formula (I) as hereinbefore defined with at least one other herbicide.

The other herbicide may be any herbicide not having the formula (I).

It will generally be a herbicide having a complementary action in the particular application.

Examples of useful complementary herbicides include: A. benzo-2,1,3-thiadiazin-4-one-2,2-dioxides such as bentazone; B. hormone herbicides, particularly the phenoxy alkanoic acids such as MCPA, MCPA-thioethyl, dichlorprop, 2,4,5-T, MCPB, 2,4-D, 2,4-DB, mecoprop, trichlopyr, clopyralid, and their derivatives (eg. salts, esters and amides); C. 1,3 dimethylpyrazole derivatives such as pyrazoxyfen, pyrazolate and benzofenap; D.Dinitrophenols and their derivatives (eg. acetates) such as dinoterb, dinoseb and its ester, dinoseb acetate; E. dinitroaniline herbicides such as dinitramine, trifluralin, ethalflurolin, pendimethalin, oryzalin; ** F. arylurea herbicides such as diuron , flumeturon, metoxuron, neburon, ** ** isoproturon , chlorotoluron , chloroxuron, linuron, monolinuron, chlorobromuron, daimuron, methabenzthiazuron; G. phenylcarbamoyloxyphenylcarbamates such as phenmedipham and desmedipham; H. 2-phenylpyridazin-3-ones such as chloridazon and norflurazon; ** I. uracil herbicides such as lenacil , bromacil and terbacil; ** J. triazine herbicides such as atrazine , simazine, aziprotryne, cyanazine, prometryn, dimethametryn, simetryne, and terbutryn;; K. phosphorothioate herbicides such as piperophos, bensu;ide, and butamifos; L. thiocarbamate herbicides such as cycloate, vernolate, molinate, * * thiobencarb, butylate , EPTC , tri-allate, di-allate, esprocarb, ** tiocarbazil, pyridate, prosulfocarb and dimepiperate; M. 1,2,4-triazin-5-one herbicides such as metamitron and metribuzin; N. benzoic acid herbicides such as 2,3,6-TBA, dicamba and chloramben; 0. anilide herbicides such as pretilachlor, butachlor, alachlor, ** propachlor, propanil, metazachlor, metolachlor, acetochlor , and dimethachlor; ** P. dihalobenzonitrile herbicides such as dichlobenil, bromoxynil and ioxynil; Q. haloalkanoic herbicides such as dalapon, TCA and salts thereof; ; R. diphenylether herbicides such as lactofen, fluroglycofen or salts or ester thereof, nitrofen, bifenox, aciflurofen and salts and esters thereof, oxyfluorfen, fomesafen, chlornitrofen and chlomethoxyfen; S. phenoxyphenoxypropionate herbicides such as diclofop and esters ** thereof such as the methyl ester, fluazifop and esters thereof, haloxyfop and esters thereof, quizalofop and esters thereof and fenoxaprop and esters thereof such as the ethyl ester; T. cyclohexanedione herbicides such as alloxydim and salts thereof, ** sethoxydim, cycloxydim, tralkoxydim , and clethodim; U. sulfonyl urea herbicides such as chlorsulfuron, sulfometuron, metsulfuron and esters thereof; benzsulfuron and esters thereof such as DPX-M6313, chlorimuron and esters such as the ethyl ester thereof pirimisulfuron and esters such as the methyl ester thereof, 2-[3-(4-methoxy-6-methyl-1,3,5- triazin-2-yl)-3-methylureidosulphonyl) benzoic acid esters such as the methyl ester thereof (DPX-LS300) and pyrazosul furon; V. imidazolidinone herbicides such as imazaquin, imazamethabenz, imazapyr and isopropylammonium salts thereof, imazethapyr; W. arylanilide herbicides such as flamprop and esters thereof, benzoylprop-ethyl, diflufenican X. amino acid herbicides such as glyphosate and glufosinate and their ** ** salts and esters , sulphosate (glyphosate trimesium) and bialaphos; Y. organoarsenical herbicides such as monosodium methanearsonate (MSMA);; Z. herbicidal amide derivative such as napropamide, propyzamide, carbetamide, tebutam, bromobutide, isoxaben, naproanilide and naptal am; AA triketones such as sulcotrion BB. miscellaneous herbicides including ethofumesate, cinmethylin, difenzoquat and salts thereof such as the methyl sulphate salt, clomazone, oxadiazon, bromofenoxim, barban, tridiphane, flurochloridone, quinchlorac and mefanacet; CC. Examples of useful contact herbicides include: bipyridylium herbicides such as those in which the active entity is paraquat and those in which the active entity is diquat; * These compounds are preferably employed in combination with a safener such as dichlormid.

** These compounds have been demonstrated to exhibit additive and in several instances synergystic effects when applied in admixture with compounds of the present invention.

It is an advantage of preferred compounds of the present invention that they are compatible with a wide range of co-herbicides such as those listed above and may exhibit additive or synergystic effects in such mixtures.

The invention will now be further described with reference to the following examples. The route to Compounds 1 to 5 is illustrated in Scheme 1 and the compound numbers referred to in Examples 1 to 5 are taken from Scheme 1. Scheme 2 illustrates the route by which Compounds 6 and 7 may be prepared and the Compound numbers mentioned in Examples 6 and 7 are taken from Scheme 2.

EXAMPLE 1 This Example illustrates the preparation of Methoxyethyl allylic ether (Compound No 1 of Table 1).

Stale 1 Preparation of vinyloxyethyl monate A tris-(t-butyldimethylsilyl ether) (Compound No. 9).

To a solution of vinyloxyethyl monate A (1.009, 2.4mmol) (Compound No.

8) in 2,6-lutidine (5.2ml, 4.78g, 44.6mmol) and dichloromethane (2ml), cooled to -15 C, was added dropwise by syringe tert-butyldimethylsilyl triflate (3.009, 11.4mmol, 2.6ml) and the mixture stirred for 25 minutes.

Then saturated ammonium chloride solution (16ml) and diethyl ether (40ml) were added and the mixture stirred at room temperature for 16 hours. The organic layer was separated, dried over anhydrous magnesium sulphate and evaporated under high vacuum to give a colourless oil (2.49). Flash chromatography on silica gel eluting with ethyl acetate/hexane 5:95 afforded the product as a colourless oil (1.41g), slightly contaminated and a pure fraction (351mg) - (Total 1.769, 97%).

1H NMR b(CDCl3) 6.49 (1H, dd), 5.78 (1H, s), 4.33 (2H,br. t), 4.20 (1H, dd), 4.03 (1H, dd), 2.18 (3H, s), 1.19 (3H, d), 0.96-0.83 (30H, m), 0.13-0.02 (18H, m).

Staoe 2 Preparation of tris-(t-butyldimethylsilyl)allylic alcohol (Compound No. 10.

To a solution of vinyloxyethyl moiiute A tris.(t-butyldimethylsilyl ether) (1.65, 2.2mmol) in dry dichloromethane (1Oml) at -78 C was added dropwise by syringe 1M diisobutylaluminium hydride in dichloromethane (1.09g, 7.7mmol, 7.7ml). The mixture was stirred for 55 minutes. Methanol (0.71ml) ard water (1.2ml) were added and the mixture left to warm to room temperature and stirred for 16 hours. The mixture was filtered, evaporated and the residue purified by flash chromatography on silica gel eluting with ethyl acetate/hexane 25:75 to afford starting material (63mg) and product (991mg, 69%) as a colourless oil.

1 NMR b(CDCl3) 5.49 (1H,br.t), 4.18 (2H, bd), 3.94-3.77 (4H, m), 3.55 (1H, br.d), 3.36 (1H, br.d), 2.74-2.64 (2H, m), 2.49 (1H,br.d), 1.86 (2H, d), 1.70 (3H, s), 1.18 (3H, d), 0.96-0.82 (30H, m), 0.12-0.02 (18H, m).

Stage 3 Preparation of tris.(t.butyldimethylsilyl)methoxyethylether (Compound No. 11).

2-Bromoethylmethyl ether (5.0g, 35.9mmol) and sodium iodide (6.46g, 43.lmmol) were heated at reflux in acetone (40ml) for 2 hours. The mixture was cooled, poured into water and extracted with diethyl ether (3 x 25ml).

The organic layer was dried and combined evaporation-distillation on a rotary evaporator fitted with a splashhead afforded Z.93g of 2-iodoethylmethyl ether. 1H NMR 8 (CDC13): 3.67(2H,t); 3.40(3H,s); 3.27(2H,t). To a suspension of hexane-washed sodium hydride (33mg, 1.38mmol, 55mg of 60% dispersion in oil) in dry N,N-dimethylformamide (3ml) was added the tris-(t-butyldimethylsilyl)allylic alcohol (450mg, 0.69mmol) followed 10 minutes later by 2-iodoethylmethyl ether (275mg, 1.38mmol). The mixture was stirred at room temperature for 14 hours then more sodium hydride (60mg ot 60% oil dispersion) and 2-iodoethylmethyl ether (200mg) added and the mixture stirred for 5 days.The mixture was partitioned between diethyl ether and water and the organic layer separated, dried over anhydrous magnesium sulphate and evaporated to an oily residue which was purified by flash chromatography eluting with ethyl acetate/hexane 15:85 to afford starting material (137mg) and desired methoxyethyl allylic ether product (256mg, 51%) as a colourless oil.

1H NMR b(CDCl3) 5.44 (1H, br.t), 4.06 (2H, t), 3.38 (3H, s), 3.36 (1H, br. d), 2.74-2.64 (2H, m), 2.48 (1H, br. d), 1.69 (3H, s), 1.18 (3H, d), 0.89 (30H, m), 0.05 (18H, m).

Staae 4 Preparation of methoxyethyl allylic ether Compound No. 1) The methoxylethyl [tris (t-butyidimethylsilyl ether)] allyl ether (19Omg, 0.26mmol) was dissolved in tetrahydrofuran (lml) and 1.1M tetrabutylammonium fluoride solution in tetrahydrofuran (238mug1 0.9lmmol, 0.83ml) added. After 20 hours the solvent was evaporated and the residue purified by flash chromatography on silica gel eluting with acetone/hexane 1:1 to afford the product as a colourless oil (50mg, 50%).

1H NMR b(CDCl3) 5.46 (1H, br, t), 4.05 2H,br, d), 3.92-3.68 (4H, m), 3.64-3.45 (6H, m), 3.38 (3H, s), 3.10-2.93 (2H, m), 2.80 (1H, bt), 2.76-2.64 (2H, m), 2.43 (1H, dd), 2.33-2.16 (2H, m), 2.10-1.95 (2H, m), 1.72 (3H, s), 1.42-1.29 (1H, m), 1.21 (3H, d), 0.93 (3H, d).

EXAMPLE 2 Preparation of Compound 2 Stage 1 Preparation of Compound 12 Compound 12 was prepared from Compound 10, which is the product obtained in Stage 2 of Example 1, using a similar method to that described for the production of Compound 11 in Example 1. The method for the preparation of Compound 12 was precisely as described in J. Med. Chem., 1989, 32, 151.

Staae 2 Preparation of Compound 2 Compound 2 was prepared from Compound 12 using the method described in J.

Med. Chem., 1989, 32, 151.

EXAMPLE 3 Preparation of Compound 3 Stage 1 Preparation of 1-iodo-8-phenyl-n-octane 1-chloro-8-phenyloctane (1g, 4.45mmol) and sodium iodide (lug, 6.68mmol) were heated under reflux together in acetone (30ml) for 14 hours. The acetone was evaporated and the residue partitioned between diethyl ether and water. The ether phase was separated and dried (MgS04) and the solvent evaporated to give a pale red oil.

1H NMR (CDCl3): 3 7.32-7.21(2H,m); 7.21-7.13(3H,m); 3.18(2H,t); 2.60(2H,t); 1.90-1.73(2H,m); 1.68-1.52(2H,m); 1.46-1.23(8H,m). Also present is ~68 1-chl oro-8-phenyl octane.

Staae 2 Preparation of Compound 13 Hexane washed sodium hydride (33mg, 1.38mmol, 55mg of a 60% dispersion in mineral oil) was suspended in dimethyl formamide (DMF) (2.5ml) and Compound 10 from Stage 2 of Example 1 was added, followed 10 minutes later by 1-iodo-8-phenyloctane from Stage 1 (1.37mmol). After 6 days the mixture was partitioned between diethyl ether and saturated ammonium chloride and the ether phase separated, dried (MgS04) and evaporated to an oily residue which was purified by flash column chromatography on SiO2 (ethyl acetate/hexane 15:85, then 3:7) to afford Compound 13 as a colourless oil (294mg, 49%) together with 161mg of recovered starting material.

NMR (CDCl3): a 7.26-7.18(5H,m); 5.43(1H,br,t); 1.70(3H,s); 1.20(3H,d); 0.94-0.87(30H,m); 0.11-0.03(18H,m)ppm.

Stage3 Preparation of Compound 3 Compound 13 (276mg, 0.32mmol) was dissolved in tetrahydrofuran (THF) and tetrabutylammonium fluoride (TBAF) (211mg, 0.81mmol, 0.73ml of a 1.1M solution in THF) added. After 24 hours the solvent was evaporated and the product purified by flash column chromatography on SiO2 (dichloromethane/methanol 94:6) to afford Compound 3 as a colourless amorphous solid.

1H NMR (CDCl3): 8 7.27-7.18(5H,m); 5.49(1H,br.t); 3.97(2H,br.d); 3.41(2H,t); 2.80(1H,dt); 2.69(1H,dd); 1.75(3H,s); 1.22(3H,d); 0.95(3H,d)ppm.

EXAMPLE 4 Preparation of Compound 4 Stage 1 Preparation of 1-benzyloxy-2-iodoethane This compound was prepared according to the method described in J. Med.

Chem. 1991, 34, 2099.

Staoe 2 Preparation of Compound 14 Compound 14 was prepared using the method described in Example 3, Stage 2 from Compound 10 (450mg, 0.69mmol) and 1-benzyloxy-2-iodoethane (358mg, 1.37mmol) in place of the 1-iodo-8-phenyloctane. The product was obtained as a colourless oil (77mg, 14%) and 401mg starting material was recovered.

1H NMR (CDCl3): 8 7.34-7.20(5H,m); 5.42(1H, br.t); 4.57-4.52(2H,m); 4.04(2H,t); 1.66(3H,s); 1.16(3H,d); 0.91-0.80(30H,m); 0.09-0.01(18H,m)ppm.

Stage 3 Preparation of Compound 4 The method used for the preparation of Compound 4 was similar to the method described in Example 1 for the preparation of Compound 1.

1H NMR (CDCl3): 8 7.37-7.23(5H,m); 5.50(1H,br.t); 4.58(2H,s); 4.06(2H,br.d); 3.63(4H,s); 2.80(1H,dt); 2.70(1H,dd); 1.73(3H,s); 1.22(3H,d); 0.94(3H,d)ppm.

EXAMPLE 5 preparation of Compound 5 This compound was prepared exactly as described in J. Med. Chem., 1989, 32, 151., from compound 15 whose preparation is described in the same document.

EXAMPLE 6 Preparation of Compound 6 Stage 1 Preparation of Compound 16 The starting material used was Compound 10 prepared in Stage 2 of Example 1. Compound 16 was prepared from Compound 10 following the method described in J. Med. Chem., 1989, 32, 151.

Staae 2 Preparation of Compound 17 2-Chloroethyl vinyl ether (4,26g, 40mmol), potassium thioacetate (11.31g, 99mmol) and sodium iodide (1.69, 10.7mmol) were stirred together at room temperature in DMF (50ml) for 3 days. The mixture was partitioned between diethyl ether and water and the ether layer separated and evaporated to give an oil which was purified by flash column chromatography on SiO2 (ethyl acetate/hexane 1:9) to an orange oil (4.37g).

1H NMR (CDCl3): 8 6.45(1H,dd); 4.20(1H,dd); 4.04(1H,dd); 3.82(2H,t); 3.16(2H,t); 2.37(3H,s).

The oil (4.30g, 29.4mmol) was then dissolved in ethanol and treated with solid sodium ethoxide (2.00g, 29.4mmol). The mixture was then evaporated to dryness to give Compound 17 as a colourless solid. 1H NMR (D20): no internal reference, 8 6.41(1H,dd); 4.27(1H,dd); 4.05(1H,dd); 3.70(2H,t); 2.60(2H,t).

Staoe 3 Preparation of Compound 19 Compound 16 (200mg, 0.29mmol) and Compound 17 (73mg, 0.58mmol) were stirred together at room temperature in DMF (5ml) for 18 hours. After this time the mixture was partitioned between diethyl ether and water and the ether phase separated and washed three times with water, dried (MgS04) and the solvent removed by evaporation to give a colourless oil (203mg).

1H NMR (CDCl3): 8 6.52-6.40(1H,m); 5.30(1H,br.t); 4.19(1H,dd); 4.02(1H,dd); 1.68(3H,s); 1.29(3H,d); 0.96-0.83(30H,m); 0.11-0.03(18H,m).

Stage 4 Preparation of Compound 6 Compound 19 (190mg, 0.27mmol) was dissolved in THF (lml) and treated with TBAF (244mg, 0.93mmol, 0.85ml of 1.1M solution in THF) and stirred overnight. The solvent was evaporated and the oily residue purified y flash column chromatography on Si02 (acetone/hexane 1:1) to afford Compound 6 as a pale yellow gum (59mg, 53%). 1H NMR (CDC13): a 6.47(1H,dd); 5.38(1H,br.t); 4.20(1H,dd); 4.04(1H,dd); 3.25(2H,d); 1.72(3H,s); 1.22(3H,d); 0.95(3H,d)ppm.

EXAMPLE 7 Preparation of Compound 7 Stave 1 Preparation of Compound 16 This is exactly as aescribed in Example 6.

Stage 2 Preparation of Compound 18 1-Benzyloxy-2-iodoethane (3.00go 11.46mmol) prepared according to the method described in J. Med. Chem., 1991, 34, 2099. was stirred together with potassium thioacetate (3.27g, 28.6mmol) in DMF (50ml) at room temperature for 24 hours. The mixture was mixed with diethyl ether and washed three times with water, dried (MgSO4) and the solvent removed by evaporation to give a colourless oil which was purifed by flash column chromatography on SiO2 (ethyl acetate/hexane 8:92) to afford the intermediate thioacetate as a yellow oil (1.31g).

1H NMR (CDCl3) S 7.39-7.21 (5H, m), 4.53 (2H, s), 3.61 (2H, t), 3.13 (2H, t); 2.35 (3H,s)ppm.

The oil (1.26g, 5.99mmol) was dissolved in ethanol (100ml) and sodium ethoxide (409mg, 5.99mmol) added. The solvent was evaporated to leave a cream solid (799mg), compound 18. 1H NMR, No internal standard, 3 7.35(5H,br.s); 4.51(2H,s); 3.57-3.47(2H,m); 2.61-2.51(2H,m)ppm.

Stage3 Preparation of Compound 20 Compound 20 was prepared by the method described in Example 6 for the preparation of Compound 19 except that Compound 16 was reacted with Compound 18 and that the product, Compound 20, was purified by flash column chromatography (ethyl acetate/hexane 2:8). The product was obtained as a colourless oil.

1H NMR (CDCl3): 3 7.37-7.26(5H,m); 5.29(1H,t); 4.53(2H,s); 3.63(2H,t); 2.70(2H,t); 1.76(3H,s); 1.20(3H,d); 0.96-0.83(30H,m); 0.13-0.02(18H,m).

Staae 4 Preparation of Compound 7 Compound 7 was prepared from compound 20 using the method described in Example 6 except that the product was purified by flash column chromatography using CH2Cl2/methanol, 9:1. The product was obtained as a yellow gum. 1H NMR (OuCl3): 5 7.39-7.25(5H,m); 5.36(1H,t); 4.54(2H,s); 3.64(2H,t); 3.22(2H,d); 1.71(3H,s); 1.18(3H,d); 0.95(3H,d)ppm.

EXAMPLE 8 This Example illustrates the herbicidal properties of compounds according to the invention.

The herbicidal activity of the compounds was tested as follows: Each chemical was formulated by dissolving it in an appropriate amount, dependent on the final spray volume, of a solvent/surfactant blend which comprised 78.2 gm/litre of Tween 20 and 21.8 gm/litre of Span 80 adjusted to 1 litre using methylcyclohexanone. Tween 20 is a Trade Mark for a surface-active agent comprising a condensate of 20 molar proportions of ethylene oxide with sorbitan laurate. Span 80 is a Trade Mark for a surface-active agent comprising sorbitan mono-laurate. If the chemical did not dissolve, the volume was made up to 5cm3 with water, glass beads were added and this mixture was then shaken to effect dissolution or suspension of the chemical, after which the beads were removed. In all cases, the mixture was then diluted with water to the required spray volume.If sprayed independently, volumes of 25cm3 and 30cm3 were required for pre-emergence and post-emergence tests respectively; if sprayed together, 45cm3 was required. The sprayed aqueous emulsion contained 4% of the initial solvent/surfactant mix and the test chemical at an appropriate concentration.

The spray compositions so prepared were sprayed onto young pot plants (post-emergence test) at a spray volume equivalent to 400 litres per hectare. Damage to plants was assessed 13 days after spraying by comparison with untreated plants, on a scale of O to 9 where 0 is 0% damage, 1 is 1-5% damage, 2 is 6-15% damage, 3 is 16-25% damage, 4 is 26-35% damage, 5 is 36-59% damage, 6 is 60-69% damage, 7 is 70-79% damage, 8 is 80-89% damage and 9 is 90-100% damage.

The designation "-" indicates that a compound was not tested against the indicated species.

The results of the tests are given in Table II below in which the rate of application was 500 g/ha.

Table 2 Test Plant Comp'd Comp'd Comp'd Comp'd Comp'd Comp'd Comp'd 1 2 3 4 5 6 7 BN 3 - - - - GM 4 5 0 0 0 0 0 ZM 1 0 2 1 2 0 0 OS O 0 0 0 0 0 0 TA O 0 0 0 0 0 0 PA 4 0 0 0 3 0 2 MI 6 1 3 0 0 0 0 CA 7 0 0 5 0 0 0 GA 5 0 0 3 0 0 0 AR 9 0 0 9 2 0 0 PO 8 5 4 7 0 0 0 IH 7 0 0 6 1 0 4 AT 1 0 0 0 0 0 0 XT 4 0 0 5 3 0 0 AF O 0 0 0 0 0 0 AM O 0 0 0 0 0 0 LR O 0 0 0 0 0 0 SH 0 3 0 0 0 0 0 SV 5 1 0 2 0 0 0 BP 2 2 0 0 0 0 3 PD O 0 4 4 0 0 0 EC O 0 0 0 0 0 0 CE 2 4 0 0 3 0 0 TABLE 3 Abbreviations used for Test Plants BN - Rape GM - Soybean ZM - Maize OS - Rice TA - Winter wheat PA - Polvoonum aviculare CA - Chenopodium album GA - Galium aparine AR - Amaranthus retroflexus PO - Portulaca oleracea IH - Ipomoea hederacea (post-emergence) AT - Abutilon theoDhrasti XT - Xanthium strumarium AF - Avena fatua AM - Alopecurus mvosuroides LR - Lolium ripidum SH - Sorghum halepense SV - Setaria viridis BP - Brachiaria platvphvila EC - Echinochloa crus-galli CE - Cvperus esculentus MI - Matricaria perforata LR - Lolium rioidum PD - Panicuum dicotomifirum CHEMICAL FORMULA (as in description)

SCHEME 1

Compound R1 1,11 (CH2)2OCH3 2, 12 (CH2)8C(SCH3)3 3,13 (CH2)8c6H5 4,14 (CH2)20CH2C6H5 5, 15 (CH2)8C02CH3 SCHEME 2

Compound R1 6, 17.19 -CH2CH2OCH=CH2 7,18.20 -(CH2)2OCH2C6H5

Claims (6)

1. CLAIMS 1. A herbicial composition comprising a compound of formula (I) in admixture with a herbicidally acceptable carrier or diluent

   wherein X is O or S and R1 is an optionally substituted alkyl, optionally substituted cycloalkyl, optionally substituted aryl, optionally substituted aralkyl or optionally substituted heterocyclyl group.
2. 2. A composition as claimed in claim 1, wherein, in the compound of formula (I), R1is C1-10 alkyl, C3-7 cycloakyl, C2 10 alkenyl or C2 10 alkynyl, any of which may optionally be substituted with C37 cycloalkyl, C1 10 alkoxy, C1-10 alkylthio, C28 alkenyloxy, C28 alkenylthio, C2-8 alkynyloxy, C2-8 a lkynylthio, halogen, halo-C1-10 alkoxy, halo-C28 alkenyloxy, alo-C2 8 alkynyloxy, carboxy, C1-6 alkoxycarbonyl, carbamoyl, aryl (which may itself be optionally substituted), aryloxy ('.ich may itself be optionally substituted), aralkyl (which may itself be optionally substituted), aralkyloxy (which may itself be optionally substituted), heterocyclyl (which may itself be optionally substituted), heterocyclyloxy (which may itself be optionally substitutea), hydroxy, cyano, nitro, C1-6 alkanoyloxy, amino mono- and di-(C1 6) alkylamino.
3. 3. A composition as claimed in claim 1 or claim 2, wherein R1 is an optionally substituted C1-10 alkyl group.
4. 4. A composition as claimed in any one of claims 1 to 3, wherein R1 is an alkyl, alkenyl, alkynyl or cycloalkyl group substituted with a C1-10 alkoxy, C1-10 alkylthio, C16 alkoxycarbonyl or aralkyloxy group.
5. 5. A composition as claimed in any one of claims 1 to 4 which further contains a complementary herbicide.
6. 6. A process for severely damaging or killing unwanted plants, the process comprising applying to the plants a herbicidally effective amount of a compound of formula (I) as defined in claim 1.