GB2282538A - Herbicidal compositions - Google Patents

Abstract

A herbicidal composition comprises a compound of formula (I) in admixture with a herbicidally acceptable carrier or diluent <IMAGE> wherein R<1> is an optionally substituted alkyl, cycloalkyl, aryl, aralkyl or heterocyclyl group.

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 reference 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 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 groups1 optionally substituted C37 cycloalkyl 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, C1-10 alkoxy, C1-10 alkylthio, C28 alkenyloxy, C28 alkenylthio, C28 alkynyloxy, C28 alkynylthio, halogen, halo-C1 lO 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, C1-6 alkyl, C1-6 alkoxy, r 6 alkylthio, halo-(C1 6) alkyl, hydroxy-(C16) alkyl, halo-(C1-6) alkoxy, C2-8 alkenyl, C2-8 alkenyloxy, C2 8 alkenylthio, C2-8 alkynyl, C2-8 alkynyloxy, C2-8 alkynylthio, hydroxy, cyano, nitro, amino, mono- and di (C1 6) alkylamino, C1-6 alkanesulphinyl, C1 6 alkanesulphonyl, carboxy, C16 alkoxycarbonyl, C1-6 alkoxycarhonyl(C1,6)alkyl, methylenedioxy, aryl (which may itself be substituted), aryloxy (which may itself be substituted), C1-4 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, benzoxazolyl, thiazolyl, isothiazolyl, pyrazolyl, benzimidazolyl, oxadiazolyl, thiadiazolyl, triazolyl, tetrazolyl, thiatriazolyl, pyrid-3-yl, pyrid-4-yl, quinolinyl, isoquinolinyl, pyrazinyl, pyrimidinyl, pyridazinyl and triazinyl.

Preferred compounds for use in the compositions of the present invention include those in which R1 is optionally substituted C1 10 alkyl, optionally substituted aryl, for example phenyl, and optionally substituted heterocyclyl, for example benzoxazolyl.

Examples of some particularly suitable compounds for use in compositions of the prevent invention are listed in Table 1.

TABLE 1 Compound R1 Number 1 -nButyl 2 -Phenyl 3 Benzoxazol-2-yl 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 the present invention can be prepared using the general route shown in Scheme 1 for the preparation of Compounds 1 to 3. The starting material is Compound 4 which may be prepared by the method described in WO 93/06118. Compound 4 may be reacted with an agent of formula (III) as follows: R S-C142-SiMe3 where R1 is as defined above for formula (I) in the presence of a strong base. The resultant compound (IV) may be deprotected according to methods known in the art, for example using an agent such as tetrabutylammonium fluoride (TBAF).

Compounds of formula (III) are known in the art and are readily available or may be prepared by known methods such as the reaction of a thiol of the formula R1SH, in the presence of a base, with bromomethyltrimethylsilane.

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 severelv .amaging or killing unwanted plants, 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 s lvent 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; anu 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 Atplus 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, methyinaphthalene, the xylenes and trichloroethylene.

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 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. 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 0.18 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-212-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 dimetnylpyrazole 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 dinitraminer trifluralin, ethalflurolin, pendimethalin, oryzalin; ** F. arylurea herbicides such as diuron , flumeturon, metoxuronw 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, bensulide, 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**1 sulphosate (glyphosate trimesium) and bialaphos; Y. organoarsenical herbicides such as monosodium methanearsonate (MSMA); Z. herbicidal amaze derivative such as napropamide, propyzamide, carbetamide, tebutam, bromobutide, isoxaben, naproanilide and naptalam; AA triketones such as sulcotrione; BB. miscellaneous herbicides including ethofumesate, cinmethylin, difenzoquat and salts thereof such as the methyl sulphate salt, clomazone, oxadiazon, bromofenoxim, barban, tridiphane, fl urochloridone, quinchl orac 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 in which Compounds 1 to 3 were prepared according to the route shown in Scheme 1. The formula numbers used in the examples refer to the formula numbers in Scheme 1.

EXAMPLE 1 Prevaration of Compound 1 A.Preparation of Compound 8 The method used for the preparation of Compound 8 is analagous to that described in J. Med. Chem.,1989, 32, 151 although the starting material there is the triethyl silyl derivative of Compound 4.

To a solution of (n-butylthio)methyltrimethylsilane (5) (550mg, 3.12mmol) in tetrahydrofuran (THF) (6ml) at OOC was added n-butyl-lithium (200mg, 3.12mmol, 1.6ml of a 1.9M solution in hexane). After stirring for 1 hour, Compound 4 was added1 dissolved in THF (2ml). The mixture was left for 3 days at 40C and then partitioned between diethyl ether and water.

The ether layer was dried (MgS04) and evaporated to an oily residue which was purified by flash column chromatography on SiO2 (ethyl acetate/hexane, 5:95). Compound 8 was obtained as a colourless oil (484mg) which by 1H NMR was an approximately 1:1 mixture of the Z and E isomers.

114 NMR b (CDCl3): 5.73(1H,br.s, Isomer A); 5.69(1H,br.s, Isomer B); 1.83(3H,br.s, Isomer A); 1.77(3H,br.s, Isomer B); 1.20(3H,d); 0.96-0.86 (6H,m); 0.13(27H,m).

B.Preparation of Compound 1 Again, the method used was based on that described in J. Med.

Chem.,1989, 32, 151.

Compound 8 (450mg, 0.74mmol) was treated with TBAF (604mg, 2.3lmmol,2.lml of a 1.1M solution in THF) for 2 hours and then evaporated.

The oily residue was purified by flash column chromatography (dichloromethane/methanol 92:8) to afford Compound 1 as a 1:1 mixture of the Z and E isomers (280mg, 97%), as a pale yellow oil.

1H NMR (CDCl3): 8 5.77(1H,brs, Isomer A); 5.75(1H,brs,Isomer B); 1.87(3H,brs, Isomer B); 1.78(3H,brs, Isomer A); 1.26-1.18(3H,m); 1.00-0.87(6H,m).

EXAMPLE 2 Preparation of Compound 2 A.Preparation of Compound 9 Compound 9 was prepared by the method described for Compound 8 in Example 1. The product was obtained as a yellow oil in 47% yield as a 1:1 mixture of the E and Z isomers.

H NMR (CDC13): a 7.35-7.08(5H,m); 6.00(1H,br.s); 1.93(3H,s, Isomer A); 1.87(3H,s, Isomer B); 1.20(3H,d); 0.90(3H,d); 0.10(27H,m).

B.Preparation of Compound 2 Compound 2 was prepared from Compound 9 using the method described in Example 1 for the preparation of Compound 1. The product was obtained as a pale yellow oil (99%) which was a 1:1 mixture of the E and Z isomers.

114 NMR (CDCl3): 8 7.36-7.13(5H,m); 6.04(1H,br.s); 1.98(3H,s,Isomer A); 1.92(3H,s,Isomer B); 1.22(3H,d); 0.98-0.92(3H,m).

EXAMPLE 3 Preparation of Compound 3 A.Preparat-.on of Compound 7 2-Mercaptobenzoxazole (2.0g, 13.2mmol) was dissolved in ethanol (50ml) and sodium ethoxide (898mg, 13.2mmol) was added. The mixture was evaporated to give a pale yellow solid (2.13g).

A portion of the solid (1.Og) was dissolved in methanol (20ml), bromomethyltrimethylsilane (966mg, 5.8mmol) was added and the mixture was stirred at room temperature overnight and then heated under reflux for 1 hour. The solvent was evaporated and the residue purified by flash column chromatography on SiO2 (ethyl acetate/hexane, 5:95) to afford Compound 7 as a colourless oil 1.25g, 91%. 1H NMR 8 (CDCl3): 7.59(1H,dd); 7.43(1H,dd); 7.32-7.16(2H,m); 2.59(2H,s); 0.26-0.15(9H,m).

B.Preparation of Compound 10 Compound 10 was prepared from Compound 7 and Compound 4 by a method similar to that described for Compound 8 in Example 1 except that lithium di-isopropylamide (LDA) was used instead of n-butyl-lithium. The product was obtained as a colourless oil in 21% yield as a 1:1 mixture of the E and Z isomers.

1H NMR (CDCl3): 5 7.82-7.68(1H,m); 7.49-7.44(1H,m); 7.33-7.21(2H,m); 6.45(1H,br.s); 2.04(3H,br.s,Isomer A); 1.94(3H,br.s,Isomer B); 1.27-1.19(3H,m); 0.96-0.87(3H,m); 0.17(27H,m).

B.Preparation of Compound 3 Compound 3 was prepared from Compound 10 using the method described in Example 1 for the preparation of Compound 1. The product was obtained as a yellow gum in 90% yield and was a 1:1 mixture of the E and Z isomers.

1H NMR (CDCl3): 8 7.62-7.52(1H,m); 7.48-7.42(1H,m); 7.34-7.19(2H,m); 6.32(1H br.s, Isomer A); 6.26(1H,br.s,Isomer B); 1.98(3H,d,J"1Hz Isomer A); 1.90(3H,d,J"1Hz, Isomer B); 1.24-1.16(3H,m); 0.90(3H quasi t).

EXAMPLE 4 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% damage1 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 2 below in which the rate of application was 500 g/ha.

Table 2 Test Plant Damage C'd BN GM ZM OS TA P MI CA GA AR PO IH ATXTAFAM LR SH SV BP PD EC CE 1 -2220330222300210200000 2-0232100022000000100000 3-0032000023000010020000 TABLE 3 Abbreviations used for Test Plants BN - Rape GM - Soybean ZM - Maize OS - Rice TA - Winter wheat PA - Polygonum aviculare CA - Chenopodium album GA - Galium aDarine AR - Amaranthus retroflexus PO - Portulaca oleracea IH - Ipomoea hederacea (post-emernence) AT - Ahutilon theophrasti XT - Xanthium strumarium AF - Avena fatua AM - Alonecurus mvosuroides LR - Lolium ripidum SH - Sorohum haleoense SV - Setaria viridis BP - Brachiaria platvphylla EC - Echinochloa crus-qalli CE - Cvoerus esculentus MI - Matricaria perforate LR - Lolium ripidum PD - Panicuum dicotomifirum CHEMICAL FORMULA (as in description)

SCHEME 1

Claims (5)

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

   wherein 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), R1 is C110 alkyl, C37 cycloalkyl, C2 10 alkenyl or C2-10 alkynyl, any of which may optionally be substituted with C37 cycloalkyl, C1 10 alkoxy, C1-10 alkylthio, C2-8 alkenyloxy, C28 alkenylthio, C2-8 alkynyloxy, C2-8 alkynylthio, halogen, halo-C1 10 alkoxy, halo-C2 8 alkenyloxy, halo-C2 8 alkynyloxy, carboxy, C16 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; or R1 is phenyl or naphthyl each of which may be optionally substituted with up to five substituents independently selected from halogen, C1-6 alkyl, C16 alkoxy, C16 alkylthio, halo-(C1 6) alkyl, hydroxy-(C1 6) alkyl, halo-(C1 6) alkoxy, C28 alkenyl, C28 alkenyloxy, C28 alkenylthio, C28 alkynyl, C28 alkynyloxy, C2-8 alkynylthio, hydroxy, cyano, nitro, amino, mono- and di- (C16) ikylamino, C1-6 alkanesulphinyl, C1-6 alkanesulphonyl, carboxy, C1-6 alkoxycarbonyl, C1-6 alkoxycarbonyl(C1 6)alkyl, methylenedioxy, aryl (which may itself be substituted), aryloxy (which may itself be substituted), C1-4 aralkyloxy (which may itself be substituted), heterocyclyl (which may itself be substituted), or heterocyclyloxy (which may itself be substituted); or R1 is fur-3-yl, thienyl, pyrrolyl, benzofuranyl, benzthienyl, indolyl, oxazolyl, isoxazolyl, benzoxazolyl, thiazolyl, isothiazolyl, pyrazolyl, benzimidazolyl, oxadiazolyl, thiadiazolyl, triazolyl, tetrazolyl, thiatriazolyl, pyrid-3-yl, pyrid-4-yl, quinolinyl, isoquinolinyl, pyrazinyl, pyrimidinyl, pyridazinyl and triazinyl.
3. 3. A compound as claimed in claim 1 or claim 2, wherein R1 is C1-10 alkyl, phenyl or benzoxazolyl.
4. 4. A composition as claimed in any one of claims 1 to 3 which further contains a complementary herbicide.
5. 5. 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.