GB2140417A

GB2140417A - A process for the preparation of N-aryloxybenzoyl sulphonamides

Info

Publication number: GB2140417A
Application number: GB08412495A
Authority: GB
Inventors: Alain Chene
Original assignee: Rhone Poulenc Agrochimie SA
Current assignee: Bayer CropScience SA
Priority date: 1983-05-17
Filing date: 1984-05-16
Publication date: 1984-11-28
Also published as: FR2546165B1; GB8412495D0; BR8402323A; GB2140417B; CA1230593A; FR2546165A1; IL71637A0; IL71637A; HU194539B; HUT34155A

Abstract

Herbicidal N-aryloxybenzoyl sulphonamides are prepared by reacting the aryloxybenzoic acid halide, which may be impure, with a sulphonamide in the presence of a halogenating agent such as P(O)Cl3. The N-aryloxybenzoyl sulphonamides are those of the general formula <IMAGE> in which W is -N= or -C(G)= and A, B, C, D, E and G are various specified groups or halogen atoms or (except D) hydrogen and R<3> is an optionally substituted alkyl, alkenyl, alkynyl, phenyl, pyridyl or thienyl group.

Description

SPECIFICATION Process for the preparation of aryloxybenzoic acids containing a sulphonamide group The present invention relates to an improved process for the preparation of certain aryloxybenzoic acid derivatives containing a sulphonamide group and having herbicidal properties.

Herbicidal phenoxybenzoic acid derivatives containing a sulphonamide group (or N-sulphonylphenoxybenzamides) are known from European Patent Applications Nos. 3,416 and 23,392 and Japanese Patent Application No. 82/106,654.

These patent applications disclose a number of products of this type, and particularly products of the general formula:

and their salts, in which: A is hydrogen; fluorine; chlorine; bromine; iodine; a nitro group; -N = NCF3;H2PO3 and its alkyl esters wherein the alkyl group contains from 1 to 4 carbon atoms; NH2; NHOH; Nt; a carboxy group or one of its functional derivatives (e.g. esters, amides and alkali metal, alkaline earth metal, ammonium and amine salts); a monoalkylamino or dialkylamino group; an NH-CO-R1 group in which R' is an alkyl or alkoxy or morioalkylamino or dialkylamino group; an alkyl group; trialkylammonium;NHS02 in which R2 is an alkyl group or a phenyl group; NHCONHSO2R2, in which R2 is as hereinbefore defined; alkylthio; alkylsulphinyl: alkylsulphonyl; dialkylsulphonium; cyanosulphonyl; hydroxy; alkanoyloxy; alkoxy; alkoxy substituted by an alkoxycarbonyl group; SH; nitroso ; -SCN; an azide group; CF3;

or acyl; B is a hydrogen, fluorine, chlorine, bromine or iodine atom, or an alkyl, alkoxy, alkylsulphinyl.

alkylsulphonyl, CF3, NO2, CN, NH2, NHCOR', wherein R1 is as hereinbefore defined, or CONY, group; C is a hydrogen or halogen atom or an alkyl or dialkylamino group; D is a fluorine, chlorine, bromine or iodine atom or a CF3, alkylthio, alkylsulphinyl, alkylsulphonyl, haloalkyl, sulphamoyl, formyl, alkylcarbonyl, CN or dimethylamino group;E is hydrogen or a haloalkyl, alkoxy, alkylsulphinyl, alkylsulphonyl, CN, CF3, NH2, CONY2, or NH-CO-R1 group, in which R' is as hereinbefore defined; W is a trivalent nitrogen atom or a -C(G) = group in which G has one of the meanings given for B; R3 is a phenyl, pyridyl or thienyl group optionally substituted by one or more halogen atoms, alkyl groups or nitro groups; or an alkenyl or alkynyl radical having 2 to 4 carbon atoms or an alkyl radical containing 1 to 4 carbon atoms optionally substituted by one or more fluorine, chlorine, bromine or iodine atoms, preferably CF3, or by one or more of the following substituents: carboxy, alkoxycarbonyl containing from 2 to 5 carbon atoms, alkylcarbonyl containing from 2 to 5 carbon atoms, monoalkylcarbamoyl or dialkylcarbamoyl in which the alkyl groups contain from 1 to 4 carbon atoms, alkylthio, alkylsulphinyl, alkylsulphonyl, each having from 1 to 4 carbon atoms, alkylcarbonyloxy containing from 2 to 5 carbon atoms, alkylcarbonylamino containing from 2 to 5 carbon atoms, or cyano.

in this specification and the accompanying claims alkyl groups and moieties, unless otherwise specified, are straight- or branched-chain and preferably contain from 1 to 4 carbon atoms.

According to the known processes, the products of general formula (I) can be prepared by reacting, between 25 and 1 40 C, an acid halide intermediate of the general formula:

in which X is chlorine, bromine or iodine, and A, B, C, D, E and W have the meanings already indicated, with a sulphonamide of the general formula: R 3SO2NH2 (Ill) in which R3 is as hereinbefore defined, generally in the presence of an acid acceptor, especially a tertiary amine such as N,N-dimethylaniline or pyridine, or an alkali metal carbonate such as anhydrous potassium carbonate or an alkali metal fluoride such as caesium fluoride.

The compounds of general formula (I) can then be alkylated in a known manner, for example by reaction with a diazoalkane containing from 1 to 4 carbon atoms, so as to give the corresponding products which are substituted on the nitrogen atom of the sulphonamide group by an alkyl group containing from 1 to 4 carbon atoms; the hydrogen atom of this same nitrogen atom can also be replaced by an alkali metal atom such as, e.g. sodium, for example by reaction with basic alkali metal reagents.

This known process for condensing the compounds of general formulae (Il) (Ill) has various disadvantages, in particular poor yields. It is believed that, in general, it is the presence of an acid acceptor which lowers the yield because it favours the diacylation reaction. Moreover, the use of an acid acceptor makes the isolation and the purification of the final products more difficult and more costly.

An objective of the invention is to remedy these disadvantages of the known processes.

The process of the present invention enables the of general formula (I) to be prepared from reactants of the general formula:

(wherein the various symbols are as hereinbefore defined) of technical or industrial grades.

In practice, the latter problem is all the more important because this type of acid of general formula (IV) is liable to contain a considerable number of impurities as a result of the number and the nature of the reactions used in its manufacture. Thus, by way of a non-limiting example, it may be indicated that acifluorofen of the formula:

i.e. 5-(2'-chloro-4'-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid, can be prepared by coupling an alkali metal meta-cresolate with a 3,4-dihalotrifluoromethylbenzene, followed by oxidation of the CH3 group to a carboxylic acid group and then nitration.During such a sequence of reactions, the number of isomers and other undesirable compounds progressively increases and a large number of acids is often detected in acifluorfen of ordinary quality, and especially the following acids: 2-nitro-3-[2'-chloro-4'-(trifluoromethyl)phenoxy]benzoic acid in an amount which can easily reach 16% by weight, 2-nitro-5-{2'-chloro-5'-(trifluoromethyl)phenoxy]benzoic acid and 4 nitro-5-[2'-chloro-4'-(trifluoromethyl)phenoxy]benzoic acid, it being easily possible for these two acids to be present in quantities of up to 3% by weight, as well as a series of other acids, in amounts which can also range up to 3%, this amount frequently being lower, however, for example less than 0.5%, such as for example the following acids 3-[2'-chloro-5'-(trifluoromethyl)phenoxy]benzoic acid, 3-2'-chlorn-4'-(trifIuornmethyl)phenoxy]benzoic acid and 2,4-dinitro 5-[2'-chloro-4'-(trifluoromethyl)phenoxy]benzoic acid, as well as 4-[2'-chloro-4'-(trifluromethyl)- phenoxyjnitrobenzene and 2-nitro-5-(2'-chloro-4'-(trifluoromethyl)phenoxy]toluene.

The process of the invention permits the preparation of products of general formula (i) having high purity from starting materials of low purity which comprise impurities in addition to the compound of general formula (IV).

The present invention provides a process for the preparation of a compound of general formula (I) wherein the various symbols are as hereinbefore defined which comprises reacting an acid halide of general formula (II) with a sulphonamide of general formula (Ill), wherein, in both, the various symbols are as defined and X is preferably a chlorine atom in the liquid phase, in the presence of a halogenating agent, preferably a phosphorated chlorinating (or chloride-forming) agent and at a temperature which is such that the hydrogen halide which is formed during the reaction is progressively removed from the reaction medium in a gaseous form as it is formed.

According to a preferred embodiment of the process according to the invention, the acid halide of general formula (II) which is used is one which has been prepared by halogenating an acid of general formula (IV) by means of a known halogenating agent.

According to an embodiment of the invention, there is employed Uor reacting with the sulphonamide of general formula (lIl) an acid halide of general formula (II) of technical or industrial quality, that is to say containing up to 20% by weight and possibly up to, but preferably less than, 30% by weight of impurities. Such impurities are, for example, the impurities derived from the reaction of a halogenating agent with an acid of general formula (IV) of technical or industrial quality, containing up to 20% by weight and possibly up to, but preferably less than, 30% by weight of impurities.These impurities in the acid halide of general formula (II) are, therefore, chiefly products whose formula is similar to that of the compound of general formula (II), but differing particularly in the number and the position of the substituents.

These impurities are therefore essentially compounds containing the group of the formula:

which carries one or more substituents, or specifically the group of the formula:

which carries one or more additional substituents.

The process of the invention comprising the reaction of the compounds of general formulae (II) and (III) is preferably carried out in the absence of an acid acceptor; furthermore, the presence of a solvent is optional.

A sub-group of compounds of general formula (I) for the preparation of which the process according to the invention is especially suitable and advantageous, consists of the compounds of general formula (I) in which A is the NO2 group or a hydrogen or chlorine atom; B is a halogen atom and more particularly a chlorine atom; C and E are hydrogen atoms; D is the CF2 group;R3 is an alkyl group preferably having 1 to 4 carbon atoms, particularly CH3; and W is -CH =, and more especially 5-(2'chloro-4'-(trifluoromethyl)phenoxy].2-nitro-N-methanesulphonylbenzam- ide The preferred reactants of general formula (II) and (III) are naturally chosen so that the symbols which appear in their formula have a meaning which is similar to that just given for the products of general formula (I).

Among the halogenating agents which may be employed there may be mentioned: P(0)CI3, PAL3, P(O)Br3 or PBr3; P(O)CI3 is preferred.

The molar ratio of (II) to (III) is generally between 0.8 and 1.2, preferably btween 0.9 and 1. 1; more especially, these reactants are in stoichiometric proportions.

The molar ratio of the halogenating agent relative to the halide of general formula (II) generally varies between 0.1 and 5. The halogenating agent can be present in large excess, e.g.

the molar ratio relative to the acid halide (II) may exceed 5 and may be as much as 20; it can then serve as a solvent for the reaction. In that case, it can be recovered by distillation from the reaction mixture for the purpose of subsequent recycling.

The reactants can also be dissolved in an inert solvent which has a boiling point above the reaction temperature, for example a liquid aliphatic or aromatic, chlorinated or unchlorinated hydrocarbon such as benzene, toluene, xylenes, mixed xylenes, cumene, 1 ,2ichlornethane, chlorobenzene or, for example, a nitrile such as acetonitrile; a mixture of several solvents can also be employed. The use of an inert solvent has the practical advantage of permitting better heat transfer in a process on an industrial scale; it also makes it possible to avoid local overheating of the reaction medium.

As hereinbefore indicated, the temperature at which the process according to the invention is carried out is such that the hydrogen halide formed during the reaction is removed from the reaction medium in a gaseous form concurrently with its production. This temperature, moreover, lies below the decomposition temperature of the compounds of general formulae (II), (III) and (I) involved in the process; in the case where a solvent is employed, the reaction temperature is advantageously less than or equal to the boiling point of this solvent which can, moreover, consist of an excess of the halogenating agent as has already been indicated.The temperature is therefore generally between 70 and 1 80 C. In the absence of a solvent, the preferred temperature is between 80 and 1 20do; in the presence of a solvent (particularly in the case of cumene which boils at 1 53 C), the temperature is advantageously between 80 and 1 50 C.

At the end of the reaction the product of general formula (I) can be isolated by methods known per se. By the term "methods known per se" as used in the present specification is meant methods heretofore used or described in the chemical literature.

The process according to the invention is distinguished by the simplicity of the method by which the final product is recovered because the latter is insoluble in the halogenating agent with the result that this recovery is usually confined to a filtration. This filtration can also be facilitated by the addition of a non-solvent.

The acid halide of general formula (II) can be prepared by any method known per se from the acid of general formula (IV). In general, the procedure is a reaction of an acid of general formula (IV) with a halogenating agent such as those mentioned hereinbefore. The reaction can, if appropriate, be carried out in situ, and catalysts, e.g. dimethylformamide, can also be employed.

The acid halide of general formula (II) can be: -separated and purified, or -separated in the crude state without purification, or prepared in situ in the reaction solvent, without being separated, before being placed in the presence of the sulphonamide of general formula (III).

The following non-limitative examples illustrate the present invention.

Example 1:

5-[2'-Chloro-4'-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid chloride (16.79; 0.044 mol) and methanesulphonamide (4.2 g; 0 044 mol) are suspended in P(O)C13 i.e. phosphoryl chloride (20 cc). The reaction mixture is heated for 1 hour at 90"C with stirring. After adding toluene (50 cc) the precipitate formed is filtered off and then washed with toluene.

A white solid consisting of 5-[2'-chloro-4'-(trifluoromethyl)phenoxy]-2-nitro-N-methanesulpho- nyl benzamide (16.49; 0.034 mol; yield 85%), of the formula (Vl), m.p. 203"C is thus obtained. The structure of this product is confirmed by infrared and by nuclear magnetic resonance (NMR).

Example 2: 5-[2'-Chloro-4'-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid chloride (19 g; 0.05 mol) and methanesulphonamide (4.759; 0.05 mol) are suspended in a mixture of P(O)C13 (14 cc) and toluene (35 cc). The reaction mixture is heated for 3 hours at 1000"C with stirring. After adding toluene (50 cc) the precipitate formed is filtered off and then washed with toluene.

A white solid consisting of 5-[2'-chloro-4'-(trifluoromethyl)phenoxyj-2-nitro-N-methanesulpho- nyl benzamide (14.7 g; 0.034 mol; yield 67%), of the formula (Vl), m.p. 198"C, is thus obtained. The structure of this product is confirmed by infrared and by NMR.

Example 3: 5-E2'-Chloro-4'-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid chloride (7.6 g; 0.02 mol) and methanesulphonamide (1.9 g; 0.02 mol) are dissolved in a mixture of P(O)CI3 (2 cc) and acetonitrile (20 cc). The reaction mixture is boiled under reflux for 2 hours 30 minutes with stirring, and is then concentrated to dryness. The crude material obtained is recrystallised from a mixture of toluene and ethyl acetate (95/5).

A white solid consisting of 5-[2'-chloro-4'-(trifluoromethyl)phenoxy]-2-nitro-N-methanesulpho- nyl benzamide (7.6 g; 0.0173 mol; yield 87%), of the formula (VI), m.p. 215"C, is thus obtained. The structure of this product is confirmed by infrared and by NMR.

Example 4: 5-[21Chlorn41-(tn'fluornmethyl)phenoxyj2-nitrnbenzoic acid (36.1 g; 0.1 mol) is suspended in a mixture of toluene (60 cc) and dimethylformamide (DMF) (1 cc). The reaction mixture is heated to 55"C with stirring. A solution of thionyl chloride (11.9 g; 0.1 mol) in toluene (15 cc) is then added. When gas ceases to be evolved, the reaction mixture is heated to 90"C, before adding methanesulphonamide (9.5 g; 0.1 mol). P(O)C13 (27 cc) is then run in over a period of 10 minutes, and the reaction mixture is then heated at 105"C for 2 hours. After cooling, the precipitate formed is filtered off and then washed with toluene.

A white solid consisting of 5-[2'-chloro-4'-(trifluoromethyl)phenoxy]-2-nitro-N-methanesulpho- nyl benzamide (23.8 g; 0.054 mol; yield 54%), of the formula (VI), m.p. 200C is thus obtained. The structure of this product is confirmed by infrared and by NMR.

Example 5: This example illustrates the preparation of benzamide of the formula (VI) starting from impure phenoxybenzoic acid. The purity of the starting phenoxybenzoic acid was determined by high performance liquid phase chromatography (abbreviated to HPLC); this HPLC was performed under the following conditions: column 20 cm in length, 4 mm in diameter, -packing of silica on which a stationary phase containing an amine group has been grafted (the chromatography takes place by a partition between the stationary phase and the eluant ---eluant: a mixture of 2,2,4-trimethylpentane, 2-propanol and acetic acid in constant volume proportions of 42/40/18 respectively -flow rate 2 cc/min.

The purity of the reaction product was also determined by HPLC under similar conditions except for varying the proportions of the components of the eluant mixture between the outset and the end of the chromatography, from a ratio of 35/50/5 to 56/20/24 (elution gradient).

The accuracy of these chromatographic methods was checked by the use of standards corresponding to the samples of each of the impurities mentioned, taken separately.

The percentages shown below are percentages by weight. The "technical-grade" acid employed contains: 80.9% of 5-[2'-chloro-4'-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid of the formula (V), -8.2% of 3-[2 '-chloro-4'-(trifl uoromethyl)phenoxy]-2-nitrobenzoic acid, 3.3% of 5-E2 '-chloro-4'-(trif luoromethyl)phenoxyl-4-nitrobenzoic acid, ess than 1 % of 5-[2 '-chloro-5'-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid, and -less than 1 % of 3-t2'-chloro-4'-(trifluoromethyl)phenoxy] benzoic acid.

Technical-grade acid (38 g) of the composition specified above is suspended in a mixture of 1,2-dichloroethane (100 cc), thionyl chloride (10.3 cc; 0.109 mol) and dimethylformamide (1 cc). The reaction mixture is heated gradually with stirring to the boil under reflux. Refluxing is continued for 1 hour after gas evolution has ended, and the material is then concentrated to dryness. The residue (40 g) is dissolved in toluene (75 cc), after which methanesulphonamide (10 g; 0.105 mol) and P(O)CI3 (25 cc) are added. The reaction mixture is then heated to the boil under reflux for 3 hours with stirring. After cooling, the precipitate formed is filtered off and then washed with toluene.

A white solid consisting of 5-[2'-chloro-4'-(trifluoromethyl)phenoxy]-2-nitro-N-methanesulpho- nyl benzamide (28 g) of the formula (Vl), m.p. 200'C, is thus obtained. The structure of this product is confirmed by infrared and by NMR. Its purity, as determined by HPLC, is 90%.

Claims

1. A process for the preparation of a compound of the general formula:

in which: A is hydrogen; fluorine; chlorine; bromine; iodine; a nitro group; -N = NCF3; H2PO3 and its alkyl esters wherein the alkyl group contains from 1 to 4 carbon atoms; NH2; NHOH; N +2; a carboxy group or one of its functional derivatives; a monoalkylamino or dialkylamino group; an NH-CO-R1 group in which R' is an alkyl or alkoxy or monoalkylamino or dialkylamino group; an alkyl group; trialkylammonium; NHSO2R2 in which R2 is an alkyl group or a phenyl group;

NHCONHSO2R2, in which R2 is as hereinbefore defined; alkylthio; alkylsulphinyl; alkylsulphonyl; dialkylsulphonium; cyanosulphonyl, hydroxy; alkanoyloxy; alkoxy, alkoxy substituted by an alkoxycarbonyl group; SH; nitroso; -SCN; azide;CF3;

or acyl; B is a hydrogen, fluorine, chlorine, bromine or iodine atom, or an alkyl, alkoxy, alkylsulphinyl, alkylsulphonyl, CF3, NO2, CN, NH2, NHCOR1 wherein Rl is as hereinbefore defined or CONY, group; C is a hydrogen or halogen atom or an alkyl or dialkylamino group; D is a fluorine, chlorine, bromine or iodine atom or a CF3, alkylthio, alkylsulphinyl, alkylsulphonyl, haloalkyl, sulphamoyl, formyl, alkylcarbonyl, CN or dimethylamino group; E is hydrogen or a haloalkyl, alkoxy, alkylsulphinyl, alkylsulphonyl, CN, CF3, NH2. CONH2, or NH-CO-R1 group, wherein R1 is as hereinbefore defined; W is a trivalent nitrogen atom or a -C(G) = group in which G has one of the meanings given for B;; R3 is a phenyl, pyridyl or thienyl group optionally substituted by one or more halogen atoms, alkyl groups or nitro groups; or an alkenyl or alkynyl radical having 2 to 4 carbon atoms or an alkyl radical containing 1 to 4 carbon atoms optionally substituted by one or more fluorine, chlorine, bromine or iodine atoms, or by one or more of the following substituents: carboxy, alkoxycarbonyl containing from 2 to 5 carbon atoms, alkylcarbonyl containing from 2 to 5 carbon atoms, monoalkylcarbamoyl or dialkylcarbamoyl in which the alkyl groups contain from 1 to 4 carbon atoms, alkylthio, alkylsulphinyl, alkylsulphonyl, each having from 1 to 4 carbon atoms, alkylcarbonyloxy containing from 2 to 5 carbon atoms, alkylcarbonylamino containing from 2 to 5 carbon atoms, or cyano, which comprises reacting an acid halide of the general formula:

with a sulphonamide of the general formula: R3-SO-2-NH2 (111) in which A, B, C, D, E and W are as hereinbefore defined, and X is chlorine, bromine or iodine, in the liquid phase in the presence of a halogenating agent and at a temperature such that the hydrogen halide formed during the reaction is removed progressively from the reaction medium in a gaseous form as it is formed.

2. A process according to claim 1 wherein R3 represents CF3.

3. A process according to claim 1 or 2 in which A is NO2 or a hydrogen or chlorine atom, B is a halogen atom, C and E are hydrogen atoms, D is a trifluoromethyl group, and W is -CH =

4. A process according to claim 1, 2 or 3, in which B is a chlorine atom and R3 is an alkyl group.

5. A process according to any one of claims 1 to 4 in which R3 is an alkyl group containing from 1 to 4 carbon atoms.

6. A process according to any one of claims 1 to 4 in which R3 is CH2.

7. A process according to any one of claims 1 to 6, wherein X in the compound of general formula (II) is a chlorine atom.

8. A process according to any one of claims 1 to 7, in which the starting material comprises, in addition to the acid halide of general formula (II), up to 30% by weight of impurities.

9. A process according to any one of claims 1 to 7 in which the starting material comprises, in addition to the acid halide of general formula (II), up to 20% by weight of impurities.

10. A process according to any one of claims 1 to 9, wherein the starting material comprises, in addition to the acid halide of general formula (II), impurities which are mainly compounds containing a group of the formula: which carries one or more substituents.

11. A process according to claim 10, in which the starting material comprises, in addition to the acid halide of general formula (II), impurities which are mainly compounds containing a group of the formula:

which carries one or more substituents.

1 2. A process according to any one of claims 1 to 11, in which the halogenating agent is P(O)Cl3, PAL3, P(O)Br3, or PBr3.

1 3. A process according to any one of claims 1 to 11, in which the halogenating agent is P(O)Cl3.

1 4. A process according to any one of claims 1 to 13, which is carried out in the absence of an acid acceptor.

1 5. A process according to any one of claims 1 to 14, in which the molar ratio of the sulphonamide of general formula (III) depicted in claim 1 relative to the acid halide of general formula (II) depicted in claim 1 is between 0.8 and 1.2.

1 6. A process according to any one of claims 1 to 14, in which the molar ratio of the sulphonamide of general formula (III) depicted in claim 1 relative to the acid halide of general formula (II) depicted in claim 1 is between 0.9 and 1.1.

1 7. A process according to one of claims 1 to 1 6 in which the molar ratio of the halogenating agent relative to the acid halide of general formula (II) depicted in claim 1 is between 0.1 and 20.

1 8. A process according to any one of claims 1 to 1 6 in which the molar ratio of the halogenating agent relative to the acid halide of general formula (II) depicted in claim 1 is between 0.1 and 5.

1 9. A process according to any one of claims 1 to 18, which is carried out in the presence of an inert solvent.

20. A process according to claim 19, in which the solvent is a liquid aliphatic or aromatic, chlorinated or non-chlorinated hydrocarbon, or a nitrile.

21. A process according to any one of claims 1 to 20, in which the reaction temperature is below the decomposition temperature of the compounds of general formulae (III), (Il) and (I) and, if appropriate, less than or equal to the boiling point of the solvent used.

22. A process according to claim 21, in which the reaction temperature is between 70 and 180"C.

23. A process according to claim 21 in which the reaction is carried out in the absence of a solvent and the reaction temperature is between 80 and 1 20 C.

24. A process according to claim 21 in which the reaction is carried out in the presence of a solvent and the reaction temperature is between 80 and 1 50 C.

25. A process according to claim 1 substantially as hereinbefore described with special reference to Examples 1 to 5.

26. A compound of general formula (I) depicted in claim 1, wherein A, B, C, D, E, Wand R3 are as defined in claim 1, whenever prepared by a process claimed in any one of claims 1 to 25.

27. 5-(2 '-chloro-4'-(trifluoromethyl)-phenoxy]-2-nitro-N-methanesulphonyl benzamide whenever prepared by a process claimed in any one of claims 1 to 25.