GB2192877A

GB2192877A - Herbicidal imidazolinyl compounds

Info

Publication number: GB2192877A
Application number: GB08617898A
Authority: GB
Inventors: David Phillip Astles; Andrew Flood
Original assignee: Shell Internationale Research Maatschappij BV
Current assignee: Shell Internationale Research Maatschappij BV
Priority date: 1986-07-22
Filing date: 1986-07-22
Publication date: 1988-01-27
Also published as: GB8617898D0

Abstract

Compounds of formula I <IMAGE> in which W is nitrogen or CH; one of L and M is a carbonyl group and the other is a group CR<6>R<7> wherein R<6> is alkyl or cycloalkyl and R<7> is an optionally substituted alkyl, cycloalkyl, alkenyl, phenyl or benzyl group; or R<6>, R<7> and the interadjacent carbon atom together form a cycloalkyl group, R<1> is a group -OR<8> where R<8> is hydrogen or a salt-forming cation, or an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, phenyl, furyl or benzyl group; R<2> is hydrogen or acyl; or R<1> and R<2> together represent a single bond between the carbon and nitrogen atoms; R<4> is hydrogen, halogen, hydroxy, nitro group or a group Q, of formula <IMAGE> in which X is cyano, thiol, amino or oximino, or a group -SR<9>, -S(O)R<9>, -S(O)2R<9> or -OR<9>, in which R<9> is cyano, acyl, alkyl, alkenyl, cycloalkyl, amino or phenyl, Y is hydrogen, halogen, alkyl or one of the groups specified for X, and Z is hydrogen or alkyl and each of R<3> and R<5> is hydrogen, halogen, nitro or cyano, or a group Q, provided that at least one of R<3>, R<4> and R<5> is a group Q. Also, processes for the preparation of such compounds, their use as herbicides, and certain diamide intermediates.

Description

SPECIFICATION Herbicidal heterocyclic compounds This invention relates to certain imidazolinyl nicotinic and benzoic acids, and derivatives thereof, the preparation of such compounds, herbicidal compositions containing them, and to their use in controlling undesired plant growth.

European Patent Nos. 41623 and 41624 and US Patent No. 4518980 describe imidazolinyl benzoic and nicotinic acids and derivatives thereof, and their use as herbicides and plant growth regulants. It has now been found that useful herbicidal activity is present in a novel class of imidazolinyl compounds.

Accordingly, the present invention provides imidazolinyl compounds of formula I

in which W represents a nitrogen atom or a CH group; one of L and M represents a carbonyl group and the other represents a group of formula CR6R7 wherein R6 represents an alkyl or cycloalkyl group and R7 represents an optionally substituted alkyl, cycloalkyl, alkenyl, phenyl or benzyl group; or R6, R7 and the interadjacent carbon atom together represent a cycloalkyl group, optionally substituted by an alkyl group; R' represents a group of formula -OR8 where R8 represents a hydrogen atom or a salt-forming cation, or an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, phenyl, furyl or benzyl group;R2 represents a hydrogen atom or an acyl group; or R1 and R2 together represent a single bond between the carbon and nitrogen atoms; R4 represents a hydrogen or halogen atom or a hydroxy or nitro group or a group Q, of formula

in which X represents a cyano or thiol group or an optionally substituted amino or oximino group or a group of formula -SR9, -S(O)R9, -S(0)2R9 or -OR9, in which R9 represents a cyano or acyl group or an optionally substituted alkyl, alkenyl, cycloalkyl, amino or phenyl group, Y represents a hydrogen or halogen atom or an alkyl group or one of the groups specified for X, and Z represents a hydrogen atom or an alkyl group; and each of R3 and R5 independently represents a hydrogen or halogen atom or a nitro or cyano group, or a group of formula 0 as defined above; provided that at least one of the groups R3, R4 and R5 is a group of formula 0 as defined above.

Included within the scope of the invention are such compounds in the form of their N-oxides and acid addition salts.

The term "acyl" is used to denote the radical derived from an organic acid by the removal of a hydroxyl group; the organic acid may be a carboxylic acid (including carbamic acid derivatives) or a sulphonic acid, examples of suitable acyl groups being groups of the formula -COR6 or -SO2R6 wherein R6 represents a hydrogen atom or an alkyl, haloalkyl, cycloalkyl, alkoxyalkyl, alkoxy, alkylthio, alkylamino, or phenylamino group, or a phenyl or furyl group optionally substituted by a halogen atom or an alkyl, haloalkyl or nitro group.

Unless otherwise specified in this specification, an alkyl, alkenyl or alkynyl group may be linear or branched and may contain up to 10, preferably up to 6, carbon atoms, suitable examples being methyl, ethyl and propyl. A cycloalkyl group may contain from 3 to 10, preferably 3 to 8, carbon atoms, and is suitably cyclopropyl. When any groups are designated as being optionally substituted, the substituent groups which are optionally present may be any of those customarily employed in the development of pesticidal compounds, and/or the modification of such compounds to influence their structure/activity, persistence, penetration or other property.In relation to alkyl, alkenyl and alkynyl groups, specific examples of such substituents include halogen, especially fluorine, chlorine or bromine atoms, and nitro, cyano, hydroxyl, C14 alkyl, C14 haloalkyl, C14 alkoxy, C14 haloalkoxy and (C14 alkoxy)-carbonyl groups and amino and oximino groups themselves optionally substituted by 1 or 2 C14 alkyl groups. It is preferred, however, that alkyl, alkenyl and alkynyl moieties in compounds of formula I are unsubstituted.In relation to a phenyl moiety, optional substituents include halogen, especially fluorine, chlorine and bromine atoms, and nitro, cyano, amino, hydroxyl, C1-4 alkyl, C1-4 haloalkyl (especially CF3) and C14 alkoxy groups. 1 to 3 substituents may suitably be employed. In the case of optionally substituted amino or oximino groups as X, Y or R9, substituents are preferably selected from C14 alkyl, phenyl and amino groups.

Preferably R4 represents a group of formula 0, as defined above. R3 and R5 may then also represent, independently of each other, an identical group Q or a different group Q or one of the other moieties specified above. Preferably, however, each of R3 and R5 represents a hydrogen atom.

In the or each group Q, it is preferred that each of Y and Z independently represents a hydrogen atom or a C1~4, suitably C1~2, alkyl group. Especially suitable are Y as hydrogen and Z as hydrogen or methyl. As for the group X, it preferably represents a group of formula -SR9, -SOR9, -SO2R9 or -OR9 in which R9 represents a C16 alkyl group, optionally substituted by one to three halogen atoms or represents a (C1 6alkyl)-carbonyl, phenyl, phenylcarbonyl or cyano group, or represents an amino group optionally substituted by one or two C14 alkyl groups; or X represents a thiol or cyano group or an oximino group which is optionally substituted by one or two C14 alkyl groups, or an amino group which is optionally substituted by one or two C14 alkyl groups or by an amino group which is optionally substituted by one or two C14 alkyl groups. More preferred still are compounds in which X represents a group of formula -SR9 or -OR9, where R9 represents a C14 alkyl group or a phenyl group, especially a methyl, ethyl or phenyl group.

In the group R'(-OR3), R8 preferably represents a halogen atom or a C16 alkyl group or a saltforming cation. The latter may be derived from any suitable base; convenient cation species including alkali metal atoms and ammonium groups, or alkylammonium groups in which the or each alkyl group contains up to 6 carbon atoms.

R2 preferably represents a hydrogen atom or a (C1 6 alkyl)-carbonyl group or a phenylcarbonyl group which is optionally substituted by a chlorine atom or a nitro or methoxy group.

The compounds of formula I in which R1 and R2 together represent a bond between the carbon and nitrogen atoms are also a preferred class.

It is preferred that R6 represents a C14 alkyl group and R7 represents a C1-4 alkyl or C36 cycloalkyl group, or R6 and R7, together with the interadjacent carbon atom, represent a C36 cycloalkyl group optionally substituted by a methyl group. C14 alkyl groups are particularly suitable for both R6 and R7, R6 preferably being a methyl group and R7 being a methyl, ethyl, or, especially, an isopropyl group.

In summary it may thus be stated that preferred compounds are those wherein W represents a nitrogen atom or a CH group; one of L and M represents a carbonyl group and the other represents the alkylidene group =CR6R7 in which R6 and R7 each independently represents an alkyl group of 1-4 carbon atoms, in particular in which R6 is methyl and R7 is isopropyl;R2 represents a hydrogen atom or an acyl group of formula COR6 in which R6 represents an alkyl group of 1-6 carbon atoms, especially a methyl group; R1 represents a group of formula -OR8 in which R8 represents a hydrogen atom, an alkyl group of 1-6 carbon atoms, especially methyl, or an alkali metal cation such as sodium; or R' and R2 together represent a bond; each of R3 and R5 represents a hydrogen atom and R4 represents a group 0 of formula

in which each of Y and Z independently represents a hydrogen atom or a C1-4 alkyl group and X represents a group of formula-SR9 or -OR9 in which R9 represents a C1-4 alkyl group or a phenyl group.

It will be appreciated that compounds of formula I wherein R2 represents a hydrogen atom can, of course, exist in tautomeric forms (represented by the alternative representations for L and M). Both tautomers fall within the scope of this invention. When R2 is an acyl group, the alternative configurations (again represented by the alternatives for L and M) represent different isomers, which again fall within the scope of this invention. Further, when the moieties Rs and R7 differ from each other, and/or moieties X, Y and Z differ from each other the compounds of formula I could be resolved into distinct enantiomers which also fall within the scope of the invention. As is well known, it is frequently the case that one such isomer will have greater biological activity than the other isomer or isomers.

In another aspect the invention provides a process for the preparation of a compound of formula I, as defined above, which comprises cyclising a compound of formula

and, when the desired compound of formula I differs from the cyclisation product, converting the product into the desired compound.

This process is preferably applied to compounds of formula Il in which R8 is a hydrogen atom, the compounds of formula I in which R8 is other than hydrogen, or in which R1 and R2 together represent a bond, then being prepared from the resulting compounds of formula I in which R8 is a hydrogen atom.

Preferably the cyclisation employs a base. Various bases may be employed, for example 1,5diazabicyclo-[5.4.0]undec-5-ene (DBU), preferably in an inert organic solvent such as xylene or toluene, or, preferably, an alkali metal hydroxide such as sodium hydroxide. An aqueous hydroxide of about 1 to 5 molar concentration is preferably employed. An organic solvent, suitably an alcohol such as methanol or ethanol, may optionally be present. The temperature is preferably from 25"C to the reflux temperature, suitably 700C to the reflux temperature.

The initial product of the reaction described above, when it employs a base, is a compound of formula I wherein R1 is a cation and R2 is a hydrogen atom. Conversion to the corresponding acid is readily effected by acidifying the salt, preferably to a pH of between 2 and 4, using a strong mineral acid, for example sulphuric or hydrochloric acid. Moreover certain reaction conditions may allow said initial product to be converted to a further compound of formula I in situ.

For example, when a strong base, for example DBU, is used in an inert solvent, for example xylene, at an elevated temperature, suitably 75 to 150"C, with removal of water essentially as soon as it forms, the main end product may be a further compound of formula I in which R1 and R2 together represent a single bond.

It is not essential that the reaction described above involves a base. Thus, when R1 is a group of formula -OR8 where B6 is other than hydrogen or a salt forming cation, cyclisation can be effected in the presence of phosphorus pentachloride, at an elevated temperature, generally between about 60"C and 100"C. The reaction is suitably conducted in the presence of an inert organic solvent, such as toluene or benzene. The product is the hydrochloride salt. Alternatively, a mixture of PCls and POCI3 may be employed, the reaction mixture being stirred at ambient temperature for several hours; commonly 2 to 8, and then the POCI3 being removed in vacuo.

The residue is dispersed in an inert organic solvent, such as toluene, the solvent removed, and the residue dispersed in water and heated to an elevated temperature, such as 80 to 100"C, thereby producing the desired product as the hydrochloride salt.

Compounds of formula I may be converted into other compounds of formula I in various further ways.

Compounds of formula I in which R1 and R2 together represent a bond may be prepared by treating compounds of formula I in which B6 and R2 are both hydrogen with a suitable dehydrating agent such as acetic anhydride or dicyclohexylcarbodiimide (DCC). The DDC reaction is preferably effected in the presence of an organic solvent, for example an ether, such as tetrahydrofuran, or a chlorinated hydrocarbon, at a temperature between about 0 and 35 C, conveniently at ambient temperature. The acetic anhydride reaction is preferably carried out without a solvent.

Compounds of formula I in which R1 and R2 are independent moieties but B6 is not hydrogen or a salt forming cation, that is esters, are conveniently produced from the compounds of formula I in which R1 and R2 together represent a bond by reaction with an appropriate alcohol R30H in the presence of its alkali metal alkoxide and/or an organic amine, such as triethylamine.

Additionally, an organic solvent, suitably an aprotic solvent such as diethyl ether, tetrahydrofuran or dioxane may be present. The reaction temperature is suitably from 10"C to the reflux temperature, ambient temperature being particularly convenient. The reaction also proceeds efficiently in the presence of an alkali metal hydride, suitably sodium hydride in the temperature range - 10 to 30"C, preferably at ambient temperature. Aprotic solvents such as diethyl ether, tetrahydrofuran or dioxane may optionally be present. The reaction is preferably effected under an inert atmosphere.

Esters of formula I may also be formed directly from the acids in standard manner, by reaction with the appropriate alcohol in the presence of a catalytic amount of a strong mineral acid such as hydrochloric or sulphuric acid, at a temperature of 50 to 100"C. In a further method the methyl ester is formed by reacting the acid with diazomethane in a suitable solvent, for example diethyl ether or tetrahydrofuran, at 0 to 250C. The methyl group may be replaced on reaction with an appropriate alkali metal alkoxide, for example R8ONa.

Compounds of formula I in which R2 is an acyl group are readily prepared by N-acylation of esters of formula I. Appropriate acylating agents are acyl halides and anhydrides, for example compounds of formula R COCI, (R10CO)2O, and R SO2CI. An organic solvent such as benzene, toluene and pyridine may be present. A base may be present to assist the acylation. Suitable reaction temperatures are in the range O"C to the reflux temperature. The N-acylated esters may then be converted, if required, into the other compounds of formula I.

Compounds of formula I in which R8 represents a salt forming cation such as an alkali metal, alkaline earth metal or ammonium ion may be prepared from the corresponding acid by dissolving the acid in an organic solvent and then adding to the solution an equivalent amount of the cation.

The invention relates.in a further aspect to the compounds of formula II per se.

The compounds of formula II are preferably prepared by reacting an anhydride of formula III with a 2-amino amide of formula IV.

The reaction preferably takes place in the presence of an organic solvent, preferably polar, such as acetonitrile or tetrahydrofuran. Desirably, an elevated temperature is employed, suitably 40"C to the reflux temperature, especially 50 to 80"C. If the reaction is effected in the presence of a strong base such as DBU and an inert solvent such as xylene, at a temperature of 75 to 150"C, with removal of water as the reaction proceeds, the compound of formula II reacts further in situ so that the end product is a compound of formula I in which R' and R2 together represent a single bond.

The compounds of formula III are suitably prepared by a series of steps. Thus a compound of formula V,

wherein each group R" is an alkyl, preferably methyl group, group and R3, R4 and R5 are as defined above, except that the or each group Q is an alkyl group, is halogenated such that the or each group 0 becomes a 1-haloalkyl or 1,1-dihaloalkyl group (depending on the quantity of the halogenating agent employed) preferably a 1-bromoalkyl or 1,1-dibromoalkyl group. Standard reaction conditions for halogenation reactions may be employed, for example conditions for halogenation reactions may be employed, for example using reagents such as N-bromosuccinimide (NBS), N-chlorosuccinimide or bromine.Preferred conditions employ NBS in a halogenated hydrocarbon, for example carbon tetrachloride, at an elevated temperature, for example 50"C to the reflux temperature, and preferably at the reflux temperature.

The thus-halogenated pyridine or benzene derivative is then reacted with a nucleophile so that the halogen atom is replaced by the group X or, where there is more than one halogen atom, one or more halogen atoms is so replaced (depending on the quantity of the nucleophile employed). Any halogen atoms which remain after the reaction with the nucleophile may be retained, and so be present in the final compound of formula I, or may be replaced in further nucleophilic reaction(s).

Standard reaction conditions may be employed for reaction with a nucleophile. Thus, the reaction preferably takes place in polar aprotic solvent, for example tetrahydrofuran, acetonitrile or dimethylformamide, at an elevated temperature, suitably 50"C to the reflux temperature, preferably the latter.

The dicarboxylic acid is then prepared from the diester by heating it, preferably at the reflux temperature, with aqueous alkali, preferably sodium hydroxide. The corresponding acid anhydride, (formula Ill) above, is then prepared from the diacid by heating it with a dicarboxylic anhydride, suitably acetic anhydride, preferably at the reflux temperature.

A compound of formula I wherein a group 0 contains a group of formula -SOR9 or -SO2R9 is preferably prepared by oxidation of the diester precursor, containing a group -SR9. Various oxidising agents can be used, for example hydrogen peroxide and peracids, suitably peroxycarboxylic acids such as metachloroperbenzoic acid. The reaction preferably takes place in the range 10 to 300C, conveniently at ambient temperature. A low boiling-point solvent, suitably a halogenated lower alkane such as dichloromethane, is preferably present. This technique, effected at a higher temperature, may also be used to prepare compounds of formula I wherein W represents an oxidised nitrogen atom.

Other techniques, analogous to those described in EP-41623, may be used with appropriate modification in respect of the starting materials, to prepare compounds of the present invention.

One suitable process for preparing compounds according to the invention may comprise cyclising a compound of formula VI

in the presence of a strong base, for example DBU, at elevated ternperature with azeotropic removal of water, to form a compound of formula I wherein R' and R2 together represent a single bond, optionally following by converting that compound into a compound of formula I wherein R1 and R2 are separate moieties, as defined above. Techniques available for such conversions are described above.

The compound of formula VI is conveniently prepared by methods analogous to those described in EP-A-41623.

Compounds of formula I have been found to show interesting activity as herbicides. Accordingly, the invention further provides a herbicidal composition comprising a compound of formula I as defined above in association with at least one carrier, and a method of making such composition which comprises bringing a compound of formula I into association with at least one carrier.

The invention also provides the use of such a compound or composition according to the invention as a herbicide. Further, in accordance with the invention there is provided a method of combating undesired plant growth at a locus by treating the locus with a compound or composition according to the invention. Application to the locus may be pre-emergence or postemergence. The dosage of active ingredient used may, for example, be from 0.05 to 4kg/ha. A carrier in a composition according to the invention is any material with which the active ingredient is formulated to facilitate application to the locus to be treated, which may for example be a plant, seed or soil, or to facilitate storage, transport or handling.A carrier may be a solid or a liquid, including a material which is normally gaseous but which has been compressed to form a liquid, and any of the carriers normally used in formulating herbicidal compositions may be used.

Preferably compositions according to the invention contain 0.5 to 95% by weight of active ingredient.

A carrier in a composition according to the invention is any material with which the active ingredient is formulated to facilitate application to the locus to be treated, which may for example be a plant, seed or soil, or to facilitate storage, transport or handling. A carrier may be a solid or a liquid, including a material which is normally gaseous but which has been compressed to form a liquid, and any of the carriers normally used in formulating herbicidal compositions may be used. Preferably compositions according to the invention contain 0.5 to 95% by weight of active ingredient.

Suitable solid carriers include natural and synthetic clays and silicates, for example natural silicas such as diatomaceous earths; magnesium silicates, for example talcs; magnesium aluminium silicates, for example attapulgites and vermiculites; aluminium silicates, for example kaolinites, montomorillonites and micas; calcium carbonate; calcium sulphate; ammonium sulphate; synthetic hydrated silicon oxides and synthetic calcium or aluminium silicates; elements, for example carbon and sulphur; natural and synthetic resins, for example coumarone resins, polyvinyl chloride, and styrene polymers and copolymers; solid polychlorophenols; bitumen; waxes; and solid fertilisers, for example superphosphates.

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

Agricultural compositions are often formulated and transported in a concentrated form which is subsequently diluted by the user before application. The presence of small amounts of a carrier which is a surface-active agent facilitates this process of dilution. Thus preferably at least one carrier in a composition according to the invention is a surface-active agent. For example the composition may contain at least two carriers, at least one of which is a surface-active agent.

A surface-active agent may be an emulsifying agent, a dispersing agent or a wetting agent; it may be nonionic or ionic. Examples of suitable surface-active agents include the sodium or calcium salts of polyacrylic acids and lignin sulphonic acids; the condensation of fatty acids or aliphatic amines or amides containing at least 12 carbon atoms in the molecule with ethylene oxide and/or propylene oxide; fatty acid esters of glycerol, sorbitan, sucrose or pentaerythritol; condensates of these with ethylene oxide and/or propylene oxide; condensation products of fatty alcohol or alkyl phenols, for example p-octylphenol or poctylcresol, with ethylene oxide and/or propylene oxide; sulphates or sulphonates-of these condensation products; alkali or alkaline earth metal salts, preferably sodium salts, of sulphuric or sulphonic acid esters containing at least 10 carbon atoms in the molecule, for example sodium lauryl sulphate, sodium secondary alkyl sulphates, sodium salts of sulphonated castor oil, and sodium alkylaryl sulphonates such as dodecylbenzene sulphonate; and polymers of ethylene oxide and copolymers of ethylene oxide and propylene oxide.

The compositions of the invention may for example be formulated as wettable powders, dusts, granules, solutions, emulsifiable concentrates, emulsions, suspension concentrates and aerosols. Wettable powders usually contain 25, 50 or 75% w of active ingredient and usually contain in addition to solid inert carrier, 3-10% w of a dispersing agent and, where necessary, 0-10% w of stabiliser(s) and/or other additives such as penetrants or stickers. Dusts are usually formulated as a dust concentrate having a similar composition to that of a wettable powder but without a dispersant, and are diluted in the field with further solid carrier to give a composition usually containing 2-10% w of active ingredient. Granules are usually prepared to have a size between 10 and 100 BS mesh (1.676-0.152 mm), and may be manufactured by agglomeration or impregnation techniques.Generally, granules will contain -75% w active ingredient and 0-10% w of additives such as stabilisers, surfactants, slow release modifiers and binding agents. The so-called "dry flowable powders" consist of relatively small granules having a relatively high concentration of active ingredient. Emulsifiable concentrates usually contain, in addition to a solvent and, when necessary, co-solvent, 10-50% w/v active ingredient, 2-20% w/v emulsifiers and 0-20% w/v of other additives such as stabilisers, penetrants and corrosion inhibitors.Suspension concentrates are usually compounded so as to obtain a stable, nonsedimenting flowable product and usually contain 10-75% w active ingredient, 0.5-15% w of dispersing agents, 0.1-10% w of suspending agents such as protective colloids and thixotropic agents, 0-10% w of other additives such as defoamers, corrosion inhibitors, stabilisers, penetrants and stickers, and water or an organic liquid in which the active ingredient is substantially insoluble; certain organic solids or inorganic salts may be present dissolved in the formulation to assist in preventing sedimentation or as anti-freeze agents for water.

Aqueous dispersions and emulsions, for example compositions obtained by diluting a wettable powder or a concentrate according to the invention with water, also lie within the scope of the invention. The said emulsions may be of the water-in-oil or of the oil-in-water type, and may have a thick 'mayonnaise'-like consistency.

The composition of the invention may also contain other ingredients, for example other compounds possessing herbicidal, insecticidal or fungicidai properties.

The invention is illustrated in the following Examples. The identity of compounds was confirmed by appropriate spectral analysis, including NMR and mass spectrometry.

Example 1 2-(5-lsopropyl-6-methyl-4-oXo-2-imidazolin-2-ylJ-511-(methylthioJethyl]nicotinic acid (a) 2,3-Dicarboxy-5-ethylpyridine, dimethyl ester (1g) dissolved in carbon tetrachloride (15ml) was treated with N-bromo succinimide (0.8g). The reaction mixture was refluxed overnight whilst being irradiated with light. When the reaction was complete the solid on the surface was removed by filtration and washed with carbon tetrachloride. The washings were added to the filtrate and the solvent was removed by evaporation, leaving the desired product, 2,3-dicarboxy5-(1-bromoethyl)pyridine, dimethyl ester, as a brown liquid (1.29).

(b) The product of step (a) above was used without purification. It was treated in dry tetrahydrofuran (15ml) with methanethiol sodium salt (0.319). The Ireaction mixture was refluxed for 32 hours. NMR analysis indicated that some starting material remained. Further methanethiol sodium salt (0.05g) was added and the mixture refluxed a further n 21 hours. The reaction mixture was filtered, and solent was removed by evaporation. Flash chromatography on silica yielded a fraction containing the desired product, 2,3-dicarboxy-5-[1-(methylthio)ethyl]-pyridine, dimethyl ester as a yellow oil (0.71g).

(c) The product of step (b) above was treated with 10% aqueous sodium hydroxide (5ml). The reaction mixture was refluxed for 22 hours then cooled, and acidified to a pH of 1 whilst being cooled in an ice-bath. The aqueous phase was extracted twice with ethylacetate. The resulting solution was dried and the solvent removed by evaporation to yield 5-[1-(methylthio)ethyl]pyridine-2,3-dicarboxylic acid (0.569) as an oil which solidified to a fluffy solid on standing.

(d) The product of step (c) above was used, without purification, to prepare the corresponding acid anhydride. The product of step (c) was refluxed in acetic anhydride (5ml) for 12 hours.

Acetic acid was removed by evaporation to yield the anhydride (0.52g) as a dark oil.

(e) The product of step (d) above, without purification, was dissolved in acetonitrile (8ml) and treated with 2-amino-2,3-dimethylbutyramide (0.39). The reaction mixture was heated at 60"C for 2 hours. Solvent was evaporated leaving 2-[(1-carbamoyl-1,2-dimethylpropyl)carbamoyl]-[5-[1- methylthio)ethyl]-nicotinic acid as a glassy brown solid. The solid was dissolved in 3 molar sodium hydroxide (8ml) and heated at 80-85"C for 3 hours. The reaction mixture was cooled, acidified until a pH of 3 was reached, extracted with dichloromethane, and the organic layer dried. Solvent was removed by evaporation leaving the title compound as a glassy yellow solid (0.3g).

Analysis: Calculated: 57.3%C 6.3%H 12.5%N Found: 56.3%C 6.0%H 11.8%N Example 2 5-[1-(Ethylthio)ethyl]2-(5-isopropyl-5-methyl-4-oxo-2-imidazolin-2-yl)nicotinic acid The title compound was prepared by a similar procedure to that of Example 1, but step (b) employed ethanethiol, sodium salt.

The title compound was a glassy beige solid (m.p. 59-60"C).

Analysis Calculated: 58.4%C 6.6%H 1 2.0%N Found: 57.8%C 6.5%H 11.8%N Example 3 2-(5-isopropyl-5-methyl-4-oxo-2-imidazolin-2-yl)-5-[1-(phenylthio)ethyl]nicotinic acid The title compound was prepared by a similar procedure to that of Example 1, but employing thiophenol, sodium salt, in step (b). The thiophenol sodium salt was prepared by stirring sodium hydride (1.06g) with thiophenol (4.4gì overnight at ambient temperature, in dry tetrahydrofuran.

The product was kept dry, under an atmosphere of inert nitrogen. The title compound was a dark brown glassy solid (m.p. 64.5%).

Analysis Calculated: 63.5%C 5.8%H 10.6%N Found: 62.0%C 5.4%H 10.2%N Example 4 2-lsopropyl-2-methyl-711-(methylthio)methyl]-5H-imidazol 12:1, 1,2]pyrrolol3,4-b]-pyridine-3(2H),5- dione The product of Example 1 (2.0gì was dissolved in dry tetrahydrofuran (50ml) and treated with dicyclohexylcarbodiimide (1.239). The reaction mixture was stirred at 0 C for 1 hour, allowed to reach ambient temperature, and stirred overnight. A precipitate which formed was filtered off and then solvent removed by evaporation to leave a brown oil. Flash chromatography on silica using 40:60 (v:v) ethylacetate:hexane as eluant yielded the title compound as an oil (0.66g).

Analysis Calculated: 60.6%C 6.0%H 13.2%N Found: 59.4%C 6.2%H 12.2%N Example 5 Methyl-2-(5-isopropyl-5-methyl-4-oxo-2-imidazolin-2-yl)-5-[ 1-(methylthio)ethyl]nicotinate Sodium hydride (0.003y) was added to dry methanol and stirred for 30 minutes under an atmosphere of dry nitrogen. The product of Example 4 (0.449) in dry methanol (10ml of methanol was used in total) was added and the reaction mixture stirred overnight at ambient temperature. Solvent was removed by evaporation leaving a brown oil. Flash chromatography on silica using 40:60 (v:v) ethylacetate: hexane yielded the title compound as a colourless oil (0.69).

Example 6 2-(5-isopropyl-5-methyl-4-oxo-2-imidazolin-2-yl)-5-[(methylthio)methyl]nicotinic acid The title compound was prepared in a manner similar to that described in Example 1, but using 2,3-dicarboxy-5-methylpyridine, dimethyl ester as starting material.

Analysis Calculated: 56.1 %C 5.8%H 13.1%N Found: 55.8%C 6.0%H 12.9%N Example 7 2-(5-isopropyl-5-methyl-4-oxo-2-imidazolin-2-yl)-[(methylthio)methyl)]benzoic acid and its 5-(methylthio)methyl isomer The mixture of title compounds was prepared as a yellow glassy solid, by following the procedure described in Example 1, but using 2,3-dimethyltoluene-2,3-dicarboxylate as starting material. The reaction between the aminoamide and the anhydride is not selective, but yields a mixture of 2-[1-carbamoyl-1,2-dimethylpropyl)carbamoyl]-5-[(methylthio)methyl]benzoic acid and 2 [1-carbamoyl-1,2-dimethylpropyl)carbamoyl[-4-[(methylthio)methyl)]benzoic acid, each of which cyclises to yield a respective title compound.

Analysis Calculated: 60.0%C 6.2%H 8.7%N Found: 59.6%C 6.2%H 8.5%N Example 8 Mixture of 4- and 5-[(ethylthio)methyl[-2-(5-isopropyl-5-methyl-4-oxo-2-imidazolin-2-yl) benzoic acid.

The mixture of title compounds was prepared, as a yellow glassy solid, in analagous manner to the compounds of the previous Examples.

Analysis Calculated: 61.1%C 6.6%H 8.4%N Found: 61.0%C 6.5%H 8.5%N Example 9 2-(5-lsopropyl-5-methyl-4-oxo-imidazolin-2-yl)-4-[(phenylthio)methyl] benzoic acid and its 5-(phenylthio)methyl isomer The mixture of the title compounds was prepared, as a yellow glassy solid, in analagous manner to the compounds of the previous Examples.

Analysis Calculated: 66.0%C 5.8%H 7.3%N Found: 64.0%C 5.7%H 7.1 %N Example 10 2-(5-lsopropyl-5-methyl-4-oxo-2-imidazolin-2-yl)-5-(methoxymethyl) nicotinic acid and its 6-methoxy isomer The mixture of title compounds was prepared, as a pale yellow glassy solid, in analogous manner to the compounds of previous Examples. Step (b) employed sodium methoxide in methanol, under reflux condition.

Analysis Calculated: 63.1 %C 6.6%H 9.2%N Found: 61.6%C 6.6%H 8.6%N Example 11 3-isopropyl-3-methyl-7-[(methylthio)methyl]-5H-imidazo[2,1-a]-isoindole-2(3H),5-dione and its 8 (methylthio)methyl isomer The product of Example 7 (1.5g) was dissolved in tetrahydrofuran (50ml) at 0 C and the solution treated with dicyclohexylcarbodiimide (0.979). The reaction mixture was stirred at 0-5"C for 1 hour and then stirred overnight at ambient temperature. The precipitate which formed was filtered off and solvent removed, to leave an oil. Flash chromatography on silica using 40:60 (v:v) ethylacetate: hexane as eluent yielded 4 fractions. The second fraction, an oil which solidified, was the title mixture.

Example 12 Mixture of (2-lsopropyl-2-methyl-7l(methylthio)methyl]-5H-imidazo[2, 1 -a]isoindole-3(2H), 5-dione and its 8-(methylthio)methyl isomer The third and fourth fractions from the chromotagraphic separation described in Example 11 were combined and formed a glassy solid. Further chromatography yielded the resolved 7- and 8- isomers together with the title mixture of them.

Example 13 (2-lsopropyl-2-methyl-7-[(methylthio)methyl]-5H-imidazo-[2, 1 -a]isoindole-3(2H), 5-dione Resolved isomer isolated as described in Example 12.

Example 14 (24sopropyl-2-methyl-8-f(methylthio)methyq-5H-imidazo-f2, 1-a]isoindole-3(2H),5-dione Resolved isomer isolated as described in Example 12.

Example 15 Mixture of methyl 2-(5-isopropyl-5-methyl-4-oxo-2-imidazolTh-2-yl)-4-f(methylthio)methyl]benzoate and its 5-(methylthio)methyl isomer The title mixture, a glassy solid, was prepared by treating the mixed product of Example 12 in the manner as described in Example 5.

Analysis Calculated: 61.6%C 6.6%H 8.4%N Found: 58.7%C 6.4%H 8.1 %N Example 16 Herbicidal Activity To evaluate their herbicidal activity, compounds according to the invention were tested using as representative range of plants: maize, Zea mays (Mz); rice, Oryza sativa (R); barnyard grass, Echinochloa crusgalli (BG); ocat, Avena sativa (0); linseed, Linum usitatissimum (L); mustard, Sinapsis alba (M); sugar beet, Beta vulgaris (SB) and soya bean, Glycine max (S).

The tests fall into two categories, pre-emergence and post-emergence. The pre-emergence tests involved spraying a liquid formulation of the compound onto the soil in which the seeds of the plant species mentioned above had recently been sown. The post-emergence tests involved two types of test, viz., soil drench and foliar spray tests. In the soil drench tests the soil in which the seedling plants of the above species were growing was drenched with a liquid formulation containing a compound of the invention, and in the foliar spray tests the seediing plants were sprayed with such a formulation.

The soil used in the tests was a prepared horticultural loam.

The formulations used in the tests were prepared from solutions of the test compounds in acetone containing 0.4% by weight of an alkylphenol/ethylene oxide condensate available under the trade mark TRITON X-155. These acetone solutions were diluted with water and the resulting formulations applied at dosage levels corresponding to 5 kg or 1 kg of active material per hectare in a volume equivalent to 600 litres per hectare in the soil spray and foliar spray test, and at a dosage of level equivalent to 10 kilograms of active material per hectare in a volume equivalent to approximately 3,000 litres per hectare in the soil drench tests.

In the pre-emergence tests untreated sown soil and in the post-emergence tests untreated soil bearing seedling plants were used as controls.

The herbicidal effects of all the test compounds were assessed visually twelve days after spraying the foliage and the soil, and thirteen days after drenching the soil. The results of these assessments in Table I below are indicated in the rows marked 12/13 D.A.T. Additionally, the herbicidal effects of some compounds were assessed 24 to 26 days after treatment. Table I below also indicates the results of such test. Results of all tests are indicated on a 0-9 scale. A rating 0 indicates growth as untreated control, a rating 9 indicates death. An increase of 1 unit on the linear scale approximates to a 10% increase in the level of effect. A symbol '-' indicates that results are not available, because it was not possible to carry out all the tests.

TABLE 1 Compound Assess of ment Soil drench 10/kg/ha Dosage Foliar spray Pre-emergence Ex. No. (D.A.T.) Mz R BG O L M SB S kg/ha Mz R BG O L M SB S Mz R BG O L M SB S 1 12/13 6 7 8 7 6 9 9 2 5 7 7 8 7 6 8 9 3 8 9 9 7 7 7 8 0 1 6 7 7 6 5 8 9 0 6 9 9 7 6 6 8 0 2 12/13 6 5 7 6 5 8 8 2 5 6 7 8 7 6 9 8 6 6 9 9 8 8 6 8 2 1 4 6 7 5 5 8 8 5 4 9 9 6 6 5 8 1 3 12/13 4 6 6 5 3 6 8 0 5 6 5 7 6 6 7 8 0 6 9 8 6 7 7 8 0 1 3 3 4 3 2 6 7 0 4 7 6 3 3 5 7 0 3 24 5 8 8 7 5 7 9 3 5 7 8 8 7 5 8 9 2 7 9 9 7 7 8 9 1 1 3 5 3 2 0 7 7 0 0 7 6 1 4 7 8 0 4 12/13 6 6 8 7 7 8 8 1 5 6 6 8 7 7 8 8 0 8 9 9 8 8 8 8 3 1 4 5 7 6 4 7 8 0 6 8 8 7 6 7 8 1 5 12/13 5 5 6 7 4 7 8 2 5 3 6 6 6 4 7 8 0 6 8 9 7 6 7 7 0 1 1 2 2 3 2 4 7 0 3 6 7 4 1 6 7 0 TABLE 1 Compound Assess of ment Soil drench 10/kg/ha Dosage Foliar spray Pre-emergence Ex.No. (D.A.T.) Mz R BG O L M SB S kg/ha Mz R BG O L M SB S Mz R BG O L M SB S 6 12/13 6 6 7 6 5 8 8 1 5 6 6 6 7 7 8 8 4 8 9 9 7 8 7 8 7 1 4 4 6 5 5 7 8 1 4 9 8 6 7 7 8 2 6 25 8 7 8 8 6 8 9 0 5 6 8 8 8 8 8 9 0 7 9 9 8 8 8 8 6 1 4 6 7 8 6 7 9 0 3 8 7 7 7 8 8 0 7 12/13 5 7 6 5 6 8 8 6 5 4 6 5 6 6 7 8 4 6 9 8 6 8 7 8 6 1 2 4 1 3 4 7 7 2 3 8 7 3 6 6 7 3 8 12/13 5 7 5 5 5 7 8 4 5 4 6 5 5 6 7 7 4 4 9 8 5 8 7 8 4 1 0 4 2 2 3 7 6 2 2 9 5 2 4 6 7 2 9 12/13 1 5 3 5 4 7 8 5 5 1 5 4 5 4 8 6 5 3 9 5 3 5 7 8 4 1 0 2 0 2 2 7 6 2 2 4 0 0 0 4 7 0 TABLE 1 Compound Assess of ment Soil drench 10/kg/ha Dosage Foliar spray Pre-emergence Ex.No. (D.A.T.) Mz R BG O L M SB S kg/ha Mz R Bg O L M SB S Mz R BG O L M SB S 9 26 0 7 0 1 1 8 8 2 5 0 4 0 0 4 8 7 4 0 8 0 0 2 7 8 3 1 0 2 0 0 2 4 5 1 0 2 0 0 1 1 6 1 10 12/13 6 7 6 6 6 7 8 4 5 5 5 7 5 5 7 8 4 7 8 7 5 7 7 8 6 1 1 4 4 4 4 6 8 3 3 8 2 0 1 6 7 0 10 26 - - - - - - - - 5 6 7 8 6 7 9 9 5 7 8 3 6 8 8 8 6 1 0 5 4 5 4 8 9 2 0 4 1 2 4 6 8 0 11 12/13 - - - - - - - - 4 0 3 0 6 5 7 9 4 1 5 1 3 6 6 7 0 1 0 2 0 3 5 7 7 3 0 1 0 1 4 4 6 0 11 26 - - - - - - - - 4 0 0 0 0 5 7 9 9 5 0 0 0 4 4 8 0 1 0 0 0 0 4 6 5 5 3 0 0 0 0 3 6 0 TABLE 1 Compound Assess of ment Soil drench 10/kg/ha Dosage Foliar spray Pre-emergence Ex.No. (D.A.T.) Mz R BG O L M SB S kg/ha Mz R BG O L M SB S Mz R BG O L M SB S 12 12/13 5 6 5 5 4 7 8 7 5 4 6 7 6 6 7 8 7 6 9 8 6 8 7 8 6 1 2 4 4 5 5 7 8 4 4 9 6 3 6 7 8 4 12 26 2 8 4 6 5 8 9 7 5 0 6 5 7 7 8 9 7 7 9 6 7 8 8 9 7 1 0 4 2 4 5 8 9 4 1 8 2 5 6 7 8 4 13 12/13 - - - - - - - - 5 0 6 5 6 6 7 8 6 1 9 7 5 7 7 8 3 1 0 4 3 4 5 7 8 4 0 6 2 2 5 6 7 0 13 26 - - - - - - - - 5 0 4 0 2 6 8 9 6 0 8 3 6 8 8 8 3 1 0 1 0 1 4 8 9 4 0 1 0 4 5 5 6 1 14 12/13 - - - - - - - - 5 3 6 5 6 6 8 8 7 4 9 6 5 6 6 8 3 1 1 4 2 4 5 7 7 4 1 8 2 2 3 3 6 2 Table 1 Compound Assess of ment Soil drench 10/kg/ha Dosage Foliar spray Pre-emergence Ex.No. (D.A.T.) Mz R BG O L M SB S kg/ha Mz R BG O L M SB S Mz R BG O L M SB S 14 26 - - - - - - - - 3 0 6 3 6 6 8 9 6 0 8 2 6 8 8 8 3 1 0 4 1 3 4 8 9 3 0 6 0 4 3 2 6 1 15 12/13 3 6 6 6 3 7 7 4 5 2 5 5 6 5 7 8 5 4 8 7 7 5 7 8 4 1 1 2 2 5 4 6 6 2 0 1 4 6 3 5 6 1 15 26 0 6 4 7 2 8 8 4 5 0 4 3 7 6 8 9 4 0 8 7 8 3 8 8 5 1 0 2 2 6 3 6 3 3 0 3 2 7 2 5 5 1

Claims

1. An imidazolinyl compound of formula I

in which W represents a nitrogen atom or a CH group; one of L and M represents a carbonyl group and the other represents a group of formula CB6B7 wherein R6 represents an alkyl or cycloalkyl group and R7 represents an optionally substituted alkyl, cycloalkyl, alkenyl, phenyl or benzyl group; or R6, R7 and the interadjacent carbon atom together represent a cycloalkyl group, optionally substituted by an alkyl group; R' represents a group of formula -OR8 where B8 represents a hydrogen atom or a salt-forming cation, or an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, phenyl, furyl or benzyl group;R2 represents a hydrogen atom or an acyl group; or R' and R2 together represent a single bond between the carbon and nitrogen atoms; R4 represents a hydrogen or halogen atom or a hydroxy or nitro group or a group Q, of formula

in which X represents a cyano or thiol group or an optionally substituted amino or oximino group, or a group of formula -SR9, -S(O)R9, -S(O)2B9 or -OR9, in which R9 represents a cyano or acyl group or an optionally substituted alkyl, alkenyl, cycloalkyl, amino or phenyl group, Y represents a hydrogen or halogen atom or an alkyl group or one of the groups specified for X, and Z represents a hydrogen atom or an alkyl group; and each of R3 and R5 independently represents a hydrogen or halogen atom or a nitro or cyano group, or a group of formula Q as defined above; provided that at least one of the groups R3, R4 and R5 is a group of formula Q as defined above.

2. A compound of formula I as claimed in claim 1, in which R4 represents a group of formula Q.

3. A compound of formula I as claimed in claim 2, in which each of R3 and R5 represents a hydrogen atom.

4. A compound of formula I, as claimed in any preceding claim, wherein each of Y and Z independently represents a hydrogen atom or a C14 alkyl group and X represents a group of formula -SR9, -SOR9, -SO2R9 or -OR9 in which R9 represents a C16 alkyl group optionally substituted by one to three halogen atoms or represents a (C1 6alkyl)carbonyl, phenyl, phenylcarbonyl or cyano group; or represents an amino optionally substituted by one or two C14 alkyl groups; or X represents a thil or cyano group or an oximino group which is optionally substituted by one or two C1-4alkyl groups, or an amino group which is optionally subtituted by one or two C14 alkyl groups or by an amino group which is optionally substituted by one or two C14 alkyl groups.

5. A compound of formula I, as claimed in claim 4, in which each of Y and Z independently represents a hydrogen atom or a C1-2 alkyl group and X represents a group of formula -SR9 or -OR9 in which R9 represents a C1-4 alkyl group or a phenyl group.

6. A compound according to claim 5, wherein Y represents a hydrogen atom, Z represents a hydrogen atom or a methyl group and R9 represents a methyl, ethyl or phenyl group.

7. A compound according to any preceding claim, wherein R' represents a group of formula -OR8 where R8 represents a hydrogen atom, a C1-6 alkyl group, an alkali metal cation or an ammonium or alkylammonium cation in which the or each alkyl group contains 1-6 carbon atoms.

8. A compound according to any of claims 1 to 6, wherein R2 represents a hydrogen atom or a (C1 6 alkyl)carbonyl group or a phenylcarbonyl group which is optionally substituted by a chlorine atom or a nitro or methoxy group.

9. A compound according to any one of claims 1 to 6, wherein R' and R2 together represent a single bond between the carbon and nitrogen atoms.

10. A compound according to any preceding claim wherein R6 represents a C1-4 alkyl group and R7 represents a C1-4 alkyl or C38 cycloalkyl group, or B6 and R7, together with the interadjacent carbon atom, represent a C38 cycloalkyl group optionally substituted by a methyl group.

11. A compound according to claim 10, wherein R6 represents a methyl group and R7 represents a methyl, ethyl, isopropyl or cyclopropyl group.

12. A compound as defined in claim 1 and specifically named in any one of Examples 1 to 15 herein.

13. A process for the preparation of a compound of formula I, as claimed in any of claims 1 to 13, which comprises cyclising a compound of formula II

14. A compound as defined in any of claims 1 to 12, whenever preprared by a process as claimed in claim 13 or 14.

15. Herbicidal composition, which comprises a compound as claimed in any of claims 1 to 12 and 14, together with a carrier.

16. A composition as claimed in claim 15, which comprises at least two carriers, at least one of which is a surface-active agent.

17. Method of combating undesired plant growth at a locus, which comprises treating the locus with a compound as claimed in any one of claims 1 to 12 and 14, or a composition as claimed in either of claims 15 or 16.

18. The use of a compound as claimed in any one of claims 1 to 12 and 14 as a herbicide.

19. A compound, process, composition, method or use, substantially as hereinbefore described.

20. A compound of formula II, as defined in claim 13.