This invention relates to chemical compounds useful as herbicides, to processes for preparing them, and to herbicidal compositions and processes utilising them.

Herbicidal compounds based upon aryl pyrazoles are known for example from J0372460, US 5,032,165 and PCT application No W092/06962.

The applicants have found a group of compounds which have a particular substituent pattern and which are active as herbicides.

According to the present invention there is provided a compound of formula (I) : where

R is alkyl, alkenyl, alkynyl, benzyl, cycloalkyl or cycloalkenyl all of which may be optionally substituted; 2 R is haloalkoxy;

R ³ is halo;

X is CN; each Y is independently halo, CN, N0 ₂ , OH, NR ^a R ^b , S0 ₂ -halo, S0 ₂ NR ^a R ^b

C0NR ^a R , NR ^c S0 ₂ R ^d or heterocyclyl ; or alkyl, 0-alkyl, S-alkyl, alkyl-0-alkyl , S0 ₂ -alkyl ,C0 ₂ R ^a , alkyl-C0 ₂ R ^a , 0-alkyl-C0 ₂ R ^a or

S-alkyl-C0 ₂ R , any of which may optionally be substituted; or two Y groups together form a further ring; m is 0-4

R ^a , R and R ^c are each independently H or optionally substituted lower alkyl; and

R is optionally substituted lower alkyl.

As used herein, the term "alkyl" refers to straight or branched alkyl chains having up to 10 carbon atoms. The terms "lower" used in relation to "alkyl" means that the chains have from 1 to 4 carbon atoms.

The term "halogen" used herein includes fluorine, chlorine, bromine and iodine. The term "halo" includes fluoro, chloro, bromo and iodo.

Suitable optional substituents for alkyl, alkenyl, alkynyl, benzyl, cycloalkyl and cycloalkenyl, groups described herein include halogen such as chlorine, fluorine and bromine; haloalkyl such as trifluoromethyl; haloalkoxy such as trifluoromethoxy; aryl such as phenyl or naphthyl; cycloalkyl for examples containing up to 7 ring atoms; or heterocyclyl

containing for example up to 10 ring atoms up to three of which are selected from oxygen, nitrogen and sulphur, such as tetrahydrofuryl . The group X is preferably attached to the phenyl ring at the 4-position.

Preferred values for are zero or 1. When m is other than zero, suitable examples of Y are fluorine and chlorine, preferably fluorine. When m is 1, Y is preferably attached to the phenyl ring at the 2-position.

A preferred group R is C,_ ₄ alkyl, especially methyl or ethyl.

Preferably R is a halomethoxy group in particular a dihalomethoxy group such as dichloromethoxy or difluoromethoxy, most preferably difluoro ethoxy.

3 Preferred examples of R include chlorine or bromine, particularly chlorine.

Specific examples of compounds of formula (I) are contained in Table I.

The formula (I) given above is intended to include tautomeric forms of the structure drawn, as well as physically distinguishable modifications of the compounds which may arise, for example, from different ways in which the molecules are arranged in a crystal lattice, or from the inability of parts of the molecule to rotate freely in relation to other parts, or from geometrical isomerism, or from intra- olecular or inter-molecular hydrogen bonding, or otherwise.

Particular examples of compounds of the invention one listed in Table I.

TABLE I

Comp No

1 CH ₃ 0CHF ₂ Cl 4-CN 2-F 1

2 CH ₃ 0CHF ₂ Br 4-CN 2-F 1

3 CH ₃ 0CHF ₂ Cl 4-CN 2-F, 5-N0 ₂ 2

4 CH ₃ 0CHF ₂ Cl 4-CN 2-F, 5-NHS0 ₂ Et 2

D CH ₃ 0CHF ₂ Cl 4-CN 2-F, 5-0CH ₂ C0 ₂ Et 2

6 CH ₃ 0CHF ₂ Cl 4-CN 2-C1 1

7 CH ₃ 0CHF ₂ Cl 4-CN 2-F, 5-SMe 2

8 CH ₃ 0CHF ₂ Cl 4-CN 2-F, 5-NH ₂ 2

9 CH ₃ 0CHF ₂ Cl 4-CN 2-F, 5-0H 2

10 CH ₃ 0CHF ₂ Cl 4-CN 2-F, 5-C1 2

11 CH ₃ 0CHF ₂ Cl 4-CN 2-F, 5-S0 ₂ NH ₂ 2

12 CH ₃ 0CHF ₂ Cl 4-CN 2-F, 5-S0 ₂ F 2

Compounds of formula (I) may be prepared by similar routes to those set out in J0372360.

In particular compounds of formula (I) may be prepared by

1 2 halogenation of compounds of formula (II) in which R , R , X, Y and are as defined in relation to formula (I). This may be done using conventional techniques as described in the prior art. In particular the reaction may be effected in a solvent such as a halogenated hydrocarbon (for example dichloromethane, chloroform and carbon tetrachloride); an aromatic hydrocarbon (such as benzene, toluene and xylene); esters such as ethyl acetate; nitriles such as acetonitrile and benzonitrile; chain-like ethers such as diethyl ether and ethylcellosolve; cyclic ethers such as dioxane and tetrahydrofuran; dimethylsulphoxide and dimethylformamide.

These solvents may be used individually, or they can be used in the form of mixtures.

A particularly preferred solvent is acetonitrile.

Suitable halogenating agents include chlorinating agents such as chlorine, phosphorus trichloride, phosphorus pentachloride and sulphuryl chloride, as well as other halogenating agents such as bromine and iodine.

The reaction temperature should be selected in the range from -30°C to 150°C, preferably from 10°C to 30°C, often room temperature, which may be maintained by either the controlled addition of the chlorinating agent or cooling or both.

Compounds of formula (II) may be prepared from compounds of formula (III) in which R , X, Y and m are as defined in relation to formula (I) by reaction with compounds of formula (R ^C Z) , where R ^c is a lower haloalkyl group and Z is a leaving group, in the presence of a base as described in the art. Examples of suitable leaving groups include chlorine. A particularly preferred compound of formula (R ^C Z) is chlorodifluoromethane.

The reaction is suitably effected in the presence of a solvent or mixtures of solvents, in the presence or absence of a base and optionally in the presence of a catalyst at a temperature between -10 and 100°C.

The applicants have found that this reaction is preferably undertaken as a stirred biphasic phase transfer reaction in the presence of an organic solvent and aqueous base solution in the presence of a phase transfer catalyst, preferably at room temperature. Suitable organic solvents are not miscible with water and include chlorinated solvents, for example, dichloromethane and chloroform, aromatic solvents, for example, toluene, ethers, for example, diethyl ether and esters, for example, ethyl acetate. Dichloromethane is a preferred solvent.

Suitable phase transfer catalysts include tetraalkylammonium or tetraalklylphosphonium, salts, in particular tetrabutylphosphonium bromide. Suitable bases are water soluble and include, but are not limited to, alkali and alkaline earth carbonates, bicarbonates and hydroxides, for example, sodium hydroxide.

In particular, the compound of formula (III) is dissolved in an organic solvent such as dichloromethane with the phase transfer catalyst and the solution is saturated with compound of formula (R ^C Z) , usually by bubbling this compound in the form of a gas through the solution. The reaction is then initiated by the addition of an aqueous solution of base

such as a 50% solution of aqueous sodium hydroxide and the mixture stirred vigorously at room temperature.

Compounds of formula (III) may be prepared from compounds of formula

4 (IV) in which X, Y and m are as defined in relation to formula (I) and R is lower alkyl (preferably ethyl) by reaction with compounds of formula (X) where R is as defined in relation to formula (I). The reaction is carried out in the presence or absence of solvent, and optionally in the presence of a catalyst at temperatures of from -10°C to 150°C in particular the reflux temperature of any solvent present. Suitable solvents are those which dissolve both reactants and include alcohols, in particular the alcohol corresponding to the group R in the compound of formula (II). For

4 instance, when R is ethyl, a preferred solvent would be ethanol .

The applicants have found that the reaction may be carried out in the absence of any solvent. Thus the compound of formula (IV) is reacted directly with a appropriate alkyl hydrazine, such as methyl hydrazine, at elevated temperature, for example at about 70°C.

Compounds of formula (IV), where X, Y and m are as defined in relation to formula (I) and R is lower alkyl, may be prepared by reacting a compound of formula (V), wherein X, Y and m are defined in relation to c formula (I) and R is a hydroxy or a leaving group, with a compound of formula (IX), where R is a group R as defined above, and R is an activating group, or R and R together form a cyclic activating group.

5 Suitable leaving groups R include halogen, in particular chlorine.

As used herein, the term 'activating' group means a group which increases the acidity of the hydrogen atoms on the adjacent carbon and is removable by acid catalysed hydrolysis, or by base catalysed hydrolysis, or by alcoholysis.

Examples of activating groups R include carboxylic ester groups in particular alkyl ester groups, salts of carboxylate groups, nitriles and optionally N-substituted amides. In particular R is either a carboxylate

8 - 9+ ester of formula C0 ₉ R or a carboxylate salt of formula C0_ R . Suitable

8 8 groups R are optionally substituted alkyl groups such as ethyl, or R together with R may be joined to form a cyclic structure. Suitable

9+ 9+ cations for R are organic or inorganic cations. Preferably R is an inorganic cation such as an alkali metal cation, suitably potassium.

Particularly preferred compounds of formula (IX) are malonate half ester

salts where R is lower alkyl, in particular ethyl, and R is a group

- 9+ 9+ CO-, R where R is an inorganic cation, in particular potassium.

^L 7

Examples of cyclic activating groups include compounds where R is a ft ft τ group of formula C0 ₂ R and R with R together form a group >C(CH,) ₂ - In this case, the compound of formula (IX) is Meldrum's acid.

The reaction may be carried out in the presence or absence of solvents or mixtures of solvents. Suitable solvents include chlorinated solvents such as dichloromethane, aromatic solvents such as toluene, ether solvents such as diethyl ether and tetrahydrofuran or nitriles such as acetonitrile. A preferred solvent is acetonitrile.

Furthermore, the reaction is carried out optionally in the presence of a base, and in the presence or absence of a nucleophilic catalyst. An inert atmosphere such as nitrogen or argon may be employed. Temperatures of from -70° to 200°C, preferably from -10° to 100°C, and most preferably from 0 to 100 C, are suitably employed. The reaction conditions which give optimal results will vary depending upon the specific nature of the compounds of formulae (V) and (IX). However the skilled chemist would be able to determine these readily.

Suitable bases for use in the reaction include inorganic bases such as alkali or alkaline earth metal hydroxides, bicarbonates, carbonates, hydrides or alcoholates, in particular potassium carbonate, sodium hydroxide or sodium ethoxide. Alternatively organic bases such as tertiary amines, pyridine, optionally substituted pyridines, Hunig's base and diazobicycloundecane may be used.

Suitable nucleophilic catalysts include pyridine, optionally substituted pyridine, imidazole, tertiary amines such as trialkylamines, N-hydroxysuccinimide and optionally substituted imidazoles.

The reaction may also require the presence of a non basic inorganic salt. Suitable salts include but are not limited to magnesium salts, in particular magnesium halides such as magnesium chloride.

When R is hydroxy, (i.e. the compound of formula (V) is a compound of formula (VI)), the compound of formula (IV) is preferably prepared using a base mediated reaction as described above but additionally in the presence of a dehydrating agent such as carbonyldiimidazole or a carbodiimide, for example N,N'-dicyclohexylcarbodiimide. In this reaction, preferred temperatures are from -60° to 150°C, typically from 20° to 40°C; a

preferred solvent is dichloromethane and a preferred base is triethylamine. Dimethylaminopyridine is a typical catalyst for this reaction.

When the compound of formula (IX) is Meldrum's acid, the reaction is suitably effected in the presence of a base, in particular Hunig's base. Temperatures of from -60° to 100°C, in particular about 0°C, are preferred in these circumstances, and dichloromethane is a preferred solvent.

When the compound of formula (IX) is a malonate half ester salt, in particular potassium ethyl malonate, compound (V) is typically an acid chloride (i.e. R is chloride).

A typical process comprises the pre-formation of a slurry of the malonate half ester _alt, a magnesium salt, preferably magnesium chloride, and a base, preferably triethylamine. The process is effected in an inert solvent, for example acetonitrile or ethyl acetate, under an inert atmosphere of, for example, nitrogen, with vigorous stirring and cooling typically to about 10°C. The reaction is typically initiated by the careful addition of the compound of formula (V) to the cooled reaction mixture, usually at about 0°C. The mixture is then stirred at a temperature between 0°C to 100°C, generally at room temperature, for an extended period, conveniently overnight.

Compounds of formula (V) may be readily prepared from the corresponding acid of formula (VI) by conventional techniques. For example, the acid of formula (VI) is reacted with thionyl chloride in the presence or absence of a solvent or mixture of inert solvents, in the presence or absence of a base and in the presence or absence of an inert atmosphere such as nitrogen or argon. Suitably the reaction is effected at temperatures of between -60 C and 150 C, typically at the reflux temperature of the solvent. Examples of solvents which can be employed include ethers such as diethyl ether, or aromatics such as toluene, or chlorinated solvents such as dichloromethane, or nitriles such as acetonitrile.

Compounds of formula (VI) may be prepared by the hydrolysis of esters of formula (VII), where m, X and Y are as defined in formula (I) and R is optionally substituted alkyl, for example methyl. The hydroylsis may be effected in the presence or absence of an organic solvent by either aqueous acid or aqueous base. Typical solvents include alcohols for example methanol, ethers, for example tetrahydrofuran, nitriles for example

acetonitrile, amides, for example dimethylforma ide, and dimethylsulphoxide. Typical acids include mineral acids, for example hydrochloric acid, and organic acids, for example toluenesulphonic acid and acetic acid. Typical bases include alkali and alkaline earth, hydroxides, hydrides, carbonates and bicarbonate for example sodium hydroxide and potassium carbonate. The reaction may be undertaken at temperatures between 0°C to boiling point of the solvent, typically in the range 0°C to 100°C.

Compounds of formula (VII) may be prepared from compounds of formula (VIII), where m and Y are as defined in formula (I), R is as defined in formula (VII) and Z is a leaving group, by reacting with a cyanide salt in the presence or absence of a catalyst in an inert solvent under an optional inert atmosphere. Typical leaving groups include sulphonate esters, sulphones and halides, for example chloride. Suitable catalysts are complexes of transition metals in appropriate oxidation states, for example nickel and palladium. Typical cyanide salts are inorganic, typically alkali or alkaline earth cyanides for example potassium cyanides. Suitable solvents include ethers, for example diethyl ether, tetrahydrofuran; aromatics, for example toluene; chlorinated solvents for example dichloromethane; nitriles for example acetonitrile; amides for example dimethylformamide or dimethylsulphoxide. Suitable inert atmospheres include argon and nitrogen. Reaction temperatures may be in the range of 0°C to 250°C. The reactions may be undertaken in an autoclave and at elevated temperatures. When undertaken without an autoclave a typical reaction temperature is reflux.

Alternatively compound of formula (I) may be prepared from a compound

1 2 3 of formula (XX) where R , R , R , Y and m are as defined in relation to formula (I) by reaction with a cyanide salt by a method chosen from standard literature procedures known to those skilled in the art. Typical procedures use the Sandmeyer reaction and may be undertaken on an aqueous solution of compounds of formula (XX) or a suspension of an isolated salt of compounds of formula (XX).

A copper or nickel cyanide, typically a copper cyanide, for example cuprous cyanide, is added to a cooled reaction mixture at typically less than 10°C. An inorganic cyanide, typically an alkali metal cyanide, for example sodium cyanide, may also be added with stirring as a solid or in

aqueous solution. The mixture is then warmed to a temperature between 30°C to 100°C, typically 50°C-70°C, until the reaction goes to completion. Compounds of formula (XX) may be formed from compounds of formula

(XXI) by diazotisation of the amino group attached to the phenyl ring by standard literature procedures involving treatment with either an inorganic nitrite in acid or an organic nitrite.

For example, the amine may be suspended in water acidified by the addition of an inorganic acids, typically aqueous hydrochloric acid, and the suspension cooled to 0-10°C, typically 0°C. An aqueous solution of an inorganic nitrite, typically an alkali metal nitrite, for example sodium nitrite, is added drdpwise to the stirred cold suspension.

On completion of the addition of the nitrite solution the reaction mixture is cooled and stirred for a further period, typically 20-30 minutes. The aqueous solution may be used directly. Alternatively, after the addition of an aqueous solution of hydrotetrafluoroboric acid, the reaction mixture is allowed to warm to room temperature with occasional stirring. A precipitate of compound of formula (XX) as its tetrahydrofluorborate salt may be collected by filtration.

Compounds of formula (XXI) may be produced from compounds of formula

(XXII) by reduction of the nitro group attached to the phenyl ring by a method chosen from standard literature procedures by those skilled in the art.

Typical procedures include, but are not limited to, catalytic hydrogenation, or hydride donor reagents, or metal in acid, or a metal salt in acid, or redox active transition metal compounds.

For example compounds of formula (XXII) maybe reduced by titanium trichloride, in an inert organic solvent, for example acetone, at a reduced temperature from 20°C to -78°C, typically less than 10°C.

Referring to Scheme A compounds of formula (XXII) may be prepared from compounds of formula (VA) or formula (VIA) where Y and m are as described in formula (I) and R is as described in formula (V) by a procedure similar to that described above for the preparation of compounds of formula (I) from compounds of formula (V) or formula (VI).

Alternatively the compounds of formulae (VIA), (VA) , (IVA), (IIIA) and (IIA) may be converted to their corresponding cyano derivatives, compounds of formula (VI), (V), (IV), (III) and (II) respectively by the previously

described procedures for the conversion of compounds of formula (XXII) to compounds of formula (I). Not all of the conditions outlined above will be suitable and effect the conversion of all of the nitro compounds to the corresponding cyano compounds. Suitable conditions will be apparent to those skilled in the art.

The cyano compounds of formula (VII), (VI), (V), (IV), (III) and (II) could be converted to a compound of formula (I) as previously described.

Compounds of formula (I) may also be prepared from other compounds of formula (I) by the addition of Y groups. This may be achieved by derivatisation using standard procedures, for example nitration or sulphonation. Nitrated or sulphonated compounds of formula (I) may, in turn, be further derivatised, again by standard procedures familiar to those skilled in the art. For example, a compound of formula (I) in which

Y is a nitro substituent may be reduced to give a compound in which Y is an amino group, which may, in turn, be derivatised to give compounds in which

Y is an amide or an alkyl sulphonamide. Further amino groups may be converted to diazonium salts which may then be converted, by procedures known to those skilled in the art, into other groups such as halogen, cyano, thioalkyl or hydroxyl. Again, using standard procedures, these substituents may also be derivatised, for example a hydroxyl substituent may be esterified or alkylated to give an ester or an optionally substituted alkyl substituent. Interconversions such as these are described in more detail in the prior art, for example in US 5,032,155.

Variations of the above procedures will be apparent to the skilled person in the art, as well as alternative processes for preparing the compounds of the invention.

The compounds of formula (I) above are active as herbicides, and the invention therefore provides in a further aspect a process for severely damaging or killing unwanted plants, which process comprises applying to the plants, or to the growth medium of the plants, a herbicidally effective amount of a compound of formula (I) as hereinbefore defined.

The compounds of formula (I) are active against a broad range of weed species including onocotyledonous and dicotyledonous species. They show some selectivity towards certain species; they may be used, for example, as selective herbicides in soya crops. The compounds of formula (I) are applied (directly to unwanted plants (post-emergence application) but they

are preferably applied to the soil before the unwanted plants emerge (pre-emergence application).

The compounds of formula (I) may be used on their own to kill or severely damage plants, but 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.

Compositions containing compounds of formula (I) 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 triisopropyl naphthalenesulphonic acid. Suitable non-ionic agents are the condensation products of ethylene oxide with fatty alcohols such as oleyl alcohol and cetyl alcohol, or with alkyl

TM phenols such as octyl- or nonyl- phenol (e.g. Agra! 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 Atplu ^' s 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 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 0.1% 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 carboxy ethylcellulose, 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

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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 0.001 to 20 kilograms per hectare is suitable while from 0.025 to 1 kilograms per hectare may be preferred.

The composition ^' s 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,l,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, peπdimethalin, oryzalin;

F. arylurea herbicides such as diuron, flumeturon, metoxuron, neburon, isoproturon, chlorotoluron, chloroxuron, linuron, onolinuron, chlorobromuron, daimuron, methabenzthiazuron;

G. phenylcarbamoyloxyphenylcarbamates such as phenmedipham and desmedipha ;

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 buta ifos;

L. thiolcarbamate herbicides such as cycloate, vernolate, molinate,

* * thiobencarb, butylate , EPTC , tri-allate, di-allate, esprocarb, tiocarbazil, pyridate, and dimepiperate; M. l,2,4-triazin-5-one herbicides such as metamitron and etribuzin; N. benzoic acid herbicides such as 2,3,6-TBA, dica ba 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 alloxydi and salts thereof, sethoxydim, cycloxydim, tralkoxydim, and clethodim; U. sulfonyl urea herbicides such as chlorosulfuron, 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-methy1-1,3,5- triazin-zyl)-3-methylureidosulphonyl) benzoic acid esters such as the methyl ester thereof (DPX-LS300) and pyrazosulfuron;

V. i idazolidinone herbicides such as imazaquin, imazamethabenz, imazapyr and isopropylammonium salts thereof, imazethapyr; W. arylanilide herbicides such as fla prop and esters thereof, benzoylprop-ethyl , diflufenican; X. amino acid herbicides such as glyphosate and glufosinate and their salts and esters, sulphosate and bialaphos; Y. organoarsenical herbicides such as monosodium methanearsonate

(MSMA); Z. herbicidal amide derivative such as napropamide, propyza ide, carbetamide, tebutam, bro obutide, isoxaben, naproanilide and naptalam; AA. miscellaneous herbicides including ethofu esate, cinmethylin, difenzoquat and salts thereof such as the methyl sulphate salt, clomazone, oxadiazon, bromofenoxim, barban, tridiphane, flurochloridone, quinchlorac, mefanacet, and triketone herbicides such as sulcotrione; BB. 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. The invention is illustrated by the following Examples. (The preparation of intermediates is described in the Preparative Examples). The abbreviations used in the Examples have the following meanings:

NMR spectrum: nuclear magnetic resonance spectrum which were recorded at 270 or 400 MHz. (This refers to the proton magnetic resonance spectrum unless otherwise stated). The following abbreviations are used to indicate the multiplicity of the peaks in the NMR spectrum: s (singlet); d (doublet); t (triplet); q (quartet) quin (quintet) m (multiplet; br (broad) .

IR spectrum: infra-red absorption spectrum. MS: mass spectrum

GC: gas chromatography TLC: thin layer chromatography m.p.: melting point b.p: boiling point

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EXAMPLE 1 This example illustrates the preparation of Compound 1 in Table I.

Step a Preparation of methyl 4-chloro-2-fluorobenzoate

3 4-Chloro-2-fluorobenzoic acid (40g) was dissolved in methanol (350cm ).

3 Concentrated sulphuric acid (3cm ) was added and the mixture heated at reflux for 6 hours. After cooling the mixture was concentrated in vacuo and the residue dissolved in chloroform. Insoluble material was removed by filtration and the filtrate was washed with water, dried over anhydrous magnesium sulphate, and filtered. The filtrate was concentrated in vacuo to give a pale orange liquid which slowly solidified on standing (27.4g,

63%). This material was used directly without further purification.

δH (CDC1 ₃ ): 3.95(3H,s); 7.2(1H+1H, ,m) ; 7.90(lH,m).

Step b Preparation of Bistriphenylphosphine nickel (II) bromide complex.

Bistriphenylphosphine nickel (II) bromide was prepared as described by Yamamoto in Chem. Abs. 50:3996i. Triphenylphosphine (24g) and anhydrous nickel (II) bromide (20g) were stirred together in n-butanol (200cm ) and the mixture heated at reflux for 2 hours. On cooling a green crystalline solid was formed. The solid was collected by filtration, washed with n-butanol, dried and used without further purification (43.4g).

Step c Preparation of methyl 4-cyano-2-fluorobenzoate.

A procedure based on those of Sakahibara et a . , Bull. Chem: Soc. Japan, 61 1985-1990 (1988), was used.

A mixture of methyl 4-chloro-2-fluorobenzoate (11.32g), prepared as described in step a, bistriphenylphosphine, nickel (II) bromide (1.48g) prepared as described in step b, zinc powder (400mg) , and triphenylphosphine (1.04g) in acetonitrile was stirred at 58°C under an inert atmosphere of nitrogen for 1 hour. Potassium cyanide (4.30g) was added and a slight exotherm observed. The mixture was stirred for a further 4 hours at 58°C. Further equivalents of bistriphenylphosphine

nickel (II) bromide (1.48g), zinc powder (400mg) and triphenylphosphine (1.04g) were added and the mixture was stirred and heated for a further 5 hours.

TM After cooling the reaction was filtered through HY-FLO and the residue washed with acetonitrile.

TM The filtrate and washings were combined and absorbed on SORBASIL silica gel. The desired product was isolated by eluation with hexane:ethyl acetate. Removal of the solvent from the relevant fractions under vacuo gave a white crystalline solid, (11.92g, 55%) which was used in the next step without further purification δ H (CDC1 ₃ ): 3.95(3H,s); 7.5.1H+1H, m);

8.05(lH,m).

Step d Preparation of 4-cyano-2-fluorobenzoic acid

Sodium hydroxide pellets (4.87g) were added to a solution cooled by an ice bath of methyl 4-cyano-2-fluorobenzoate (19.8g), prepared as described in step c, disolved in ethanol (180cm ). The reaction solution became milky. The mixture was stirred at room temperature overnight, then diluted with water and extracted with diethyl ether. The aqueous solution was cooled with an ice bath and acidified with concentrated hydrochloric acid, and extracted with diethyl ether (3x150cm ). The ether extracts were combined, dried over anhydrous magnesium sulfate and filtered. The filtrate was concentrated under vacuo to give a white solid (15.8g, 86.5%). δH (CDC1- : δ 7.75(lH,dd); 7.95(lH+lH,m) .

Step e. The preparation of ethyl 3-(4-cyano-2-fluorophenyl)-3-oxo- propionate

3 Thionyl chloride (150cm ) was added to 4-cyano-2-fluorobenzoic acid

(15.8g), prepared as described in step d, and the mixture heated at reflux for 3 hours. After cooling excess thionyl chloride and other volatiles were removed under vacuo to give a pale yellow liquid, crude

4-cyano-2-fluorobenzoylchloride, which was used directly without further purification.

Potassium ethyl malonate (32.41g) was added to dry acetonitrile

(120cm ) and the mixture cooled to 10°C under an inert atmosphere of

nitrogen. Triethylamine (17.97g) and magnesium chloroide (19.96g) were added with vigorous stirring and the mixture was allowed to warm to room temperature and then stirred for 23_ hours. The resulting slurry was cooled to 0°C, the crude 4-cyano-2-fluorobenzoyl chloride was added dropwise over approximately 15 minutes, and then further triethylamine (1.797g) was added. The reaction mixture was allowed to warm to room temperature and stirred overnight.

Acetonitrile was removed under vacuo. The residue was mixed with toluene. The mixture was concentrated under vacuo and ethyl acetate added. The mixture was cooled to 10°C, 2N hydrochloric acid (160cm ) was added with vigorous stirring and the mixture temperature maintained at less than 25°C. The two resulting phases were separated and the aqueous phase extracted with further ethyl acetate. The combined ethyl acetate extracts were washed with 2N hydrochloric acid then water, dried over anyhdrous magnesium sulphate, and filtered. The filtrate was concentrated under vacuo to give a semi solid residue. The desired product was isolated

TM by column chromatography on SORBASIL silica gel eluting with hexane:ethyl acetate 3:1. Concentration of the relevant fractions under vacuo gave a pale orange solid, the desired product as a mixture of keto/enol tautomers

(10.65g, 52%).

Step f. Preparation of 1-methyl-3-(4-cyano-2-fluorophenyl)-3-hydroxy- pyrazole

Ethyl 3-(4-cyano-2-fluoprophenyl)-3-oxopropionate (5.2g) was suspended in

3 ethanol (5cm ) . Methylhydrazine (1.12g) was added to the stirred mixture over 10 minutes. The mixture was then stirred overnight at room temperature. Hexane and ethanol were then added to mixture which was stirred for approximately 30 minutes.

The crude desired product was filtered off, washed with hexane, dried, and used without further purification (3.84g, 80%). δH (CDC1 ₃ ):

3.55(3H,s); 5.8(lH,d); 7.6(lH,dd); 7.8(lH,dd); 8.0(lH,t).

Step g The preparation of l-methyl-3-(4-cyano-2-fluorophenyl)-5-difluoro- methoxypyrazole.

Crude l-methyl-3-(4-cyano-2-fluorophenyl)-5-hydroxypyrazole (3.66g) , prepared as described in step f, was suspended in methylene chloride, to which was added tetrabutylphosphonium bromide (1.91g).

Chlorodifluoromethane gas was bubbled through the suspension until the

3 mixture was saturated. 50% Aqueous sodium hydroxide (35cm ) was added dropwise to the vigorously stirred suspension. When the addition was complete, the mixture was stirred at room temperature for a further 1 hour.

The reaction mixture' was then diluted with water and the two phases separated. The aqueous phase was extracted with methylene chloride and the extracts were combined with the organic phase. The combined organic phases were dried over anhydrous magnesium sulphate, filtered and concentrated

TM under vacuo. The residue was absorbed onto SORBASIL silica gel and purified by column chromatography eluting with hexane:diethyl ether 3:1.

The desired product was obtained as a white solid by concentrating under vacuo the relevant fractions (1.56g, 32%). δH (CDC ): 3.8(3H,s);

6.6(lH,t); 6.4(lH,d); 7.45(lH+lH,m) ; 8.15(lH,t).

Step h The preparation of l-methyl-3-(4-cyano-2-fluorophenyl)-4-chloro- -5-difluoromethoxypyrazole, compound (1) of Table I.

l-Methyl-3-(4-cyano-2-fluorophenyl)-5-difluoromethoxypyra zole (540mg) , prepared as described in step g, was suspended in acetonitrile (5cm ) . Sulphuryl chloride (273mg) was added dropwise to the stirred suspension and the internal temperature maintained at less than 25°C. When the addition was complete, the reaction mixture was stirred at room temperature for approximately 1 hour while the reaction was monitored for completetion by GC. The reaction mixture was poured into a saturated aqueous solution of sodium bicarbonate and extracted with diethyl ether (3x20cm ). The combined diethyl ether extracts were washed with a saturated aqueous solution of sodium bicarbonate and then water, dried over anhydrous magnesium sulphate and filtered. The filtrate was concentrated under vacuo to give the desired product as a pale yellow gum which solidified on standing (515mg, 85%). M.pt 90-91°C. δH (CDCI3) : 3.85(3H,s); 6.7(lH,t);

7 .5 ( lH+lH , m) ; 7 .7 ( lH , m) .

EXAMPLE 2

This example illustrates the preparation of Compound 2 in Table I.

3 Anhydrous sodium acetate (700mg) and water (1cm ) were added to a stirred solution of l-methyl-3-(4-cyano-2-fluorophenyl)-5-difluoro- ethoxypyrazole (948mg) , prepared as described in step g of Example 1, in

3 glacial acetic acid (15cm ). Bromine (680mg) was then added dropwise at room temperature to the stirred reaction mixture. On completion of the addition of bromine, ^' the reaction mixture was stirred for a further 12 hours at room temperature and then poured into a mixture of ice and water.

The precipitated solid was collected by filtration, washed with water, and dried to give the desired product as a pale yellow solid (856mg, 55%).

M.pt. 97-98°C. δH (CDCI3) : 3.9(3H,s); 6.7(lH,t); 7.5(2xlH,m); 7.7(lH,m).

Biological Data

The herbicidal activity of the compounds was tested as follows: each chemical was formulated in one of two ways. Either the chemical was dissolved in an appropriate amount of water, dependent on the amount of solvent/surfactant blend required such that the total volume is 5cm . Then

TM a solvent sufficient blend comprised 78.2 gm/litre of TWEEN 20 and 21.8

TM gm/litre of SPAN 80 adjusted to 1 litre using methylcyclohexanone was added to the solution. Alternatively, the chemical was dissolved in water to the required concentration and 0.1% TWEEN added. 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 5cm 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 to the required spray volume. If

3 3 sprayed independently, volumes of 25cm and 30cm were required for

3 post-emergence tests; if sprayed together, 45cm 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 on to young pot plants (post-emergence test) at a spray volume equivalent to 1000 litres per hectare. Damage to plants was assessed 13 days after spraying by comparison with untreated plants, on a scale of 0 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.

In a test carried out to detect pre-emergence herbicidal activity, crop seeds were sown at 2 cm depth and weed seeds at 1 cm depth beneath compost and sprayed with the compositions at the rate of 1000 litres per hectare. 20 days after spraying, the seedlings in the sprayed plastic trays were compared with the seedlings in unsprayed control trays, the damage being assessed on the same scale of 0 to 9.

The results of the tests are given in Table II below.

TABLE I II

Abbreviations used for Test Plants

BV - Sugar beet

BN - Oil seed rape

GM - Soybean

ZM - Maize

OS - Rice

TA - Winter wheat

PA - Polvαonu aviculare

CA - Cheπopodium album

GA - Galiurn aparine

AR - Amaranthus retroflexus

MI - Matricaria inodora

BP - Bidens pilosa

PO - Portulaca oleracea

IH - Ipomoea hederacea

AT - Abutilon theophrasti

XT - Xanthium strumarium

AF - Avena fatua

AM - Alopecurus mvosuroides

LR - Lolium rioidum

SH - Sorαhum halepense

SV - Setaria viridis

PD - Panicum dichotomiflorum

EC - Echinochloa crus-galli

CE - Cvperus esculentus

(VIII) (VII)

(VI) (V)

(IX) (X)

(IV)

(III) (II)

(XXII) (XXI)

(XX)

.

^■ 26-

Scheme A 0 ₂ N

(VIA)

C0 ₂ H

(Y)m

(IIA)