GB2276379A - Herbicidal compounds having a pentafluorosulphanyl group - Google Patents

Abstract

Herbicidal dinitroaniline, arylurea, 2-phenylpyridazin-3-one, diphenylether, phenoxyphenoxypropionate, heteroaryloxyphenoxypropionate, arylanilide or substituted phenyl pyrrolidone derivatives have a phenyl or pyridyl group which carries a pentafluorosulphanyl group. Novel intermediates have the formula: <IMAGE> where R<26> and R<27> are both halogen, or R<26> is amino and R<27> is halogen, or R<26> is halogen and R<27> is nitro.

Description

NOVEL COMPOUNDS The present invention relates to herbicidal compounds having a phenyl group having a pentafluorosulphanyl substitutent.

Numerous examples are known of herbicidal compounds containing a trifluoromethyl phenyl or pyridyl group wherein the phenyl or pyridyl group optionally contains further substituents. Examples of such groups can be found in the following classes of herbicides; A. dinitroaniline herbicides such as N' ,N'-diethyl-2,6-dinitro-4-trifluoromethyl- m-phenylenediamine (dinitramine), 2,6-dinitro-N,N-dipropyl-4-trifluoromethylaniline (trifluralin), N-ethyl-N-(2-methylallyl)-2,6-dinitro-4 trifluoromethylaniline (ethalflurolin), B. arylurea herbicides such as N,N-dimethyl-N'-[3-(trifluoromethyl) phenyl]urea (fluometuron), C. 2-phenylpyridazin-3-ones such as and 4-chloro-5-methylamino-2-(a,a,a-trifluoro-m- tolyl) pyridazin-3(2H)-one (norflurazon);; D. diphenylether herbicides such as ethyl 2-[5 (2-chloro-trifluoro-p-tolyloxy)-2- nitrobenzoyloxy propionate (lactofen), D-[5-(2- chloro-a,a,a-trifluoro-p-tolyloxy)-2 nitrobenzoyl] glycolic acid (fluroglycofen) or salts or ester thereof, 2-nitro-5- (2-chl oro-4-tri fl uoromethyl -phenoxy) benzoic acid (acifluorfen) and salts and esters thereof, 2-chloro-4-trifluoromethylphenyl 3-ethoxy- 4-nitrophenyl ether (oxyfluorfen) and 5-(2- chloro-4-(trifluoromethyl)phenoxy)-N (methylsulfonyl)-2-nitrobenzamide (fomesafen);; E. aryloxy or heteroaryl oxyphenoxypropionate herbicides such as trifluoromethyl)-2-(pyridinyl)oxy) phenoxypropanoic acid (fluazifop) and esters thereof, 2-(4-(3-chloro-5-trifluoromethyl)-2 pyridinyl)oxy)phenoxy)propanoic acid (haloxyfop) and esters thereof, F. arylanilide herbicides such as N-(2,4-difluorophenyl)-2-(3 trifluoromethyl)phenoxy)-3-pyridinecarboxamide (diflufenican); G. (3RS,4RS; 3RS,4SR)-3-chloro-4-chloromethyl-1-a, a,a-trifluro-m-tolyl)-2-pyrrolidone (in the ratio 3:1) (fluorodichloridone), Examples of these compounds are also found in USP 3257190, USP3617252, DE 2361463, USP 3134665, USP 3644355, USP 4311515, DE 2753900, NL 7303590, EP-A-3416, EP-A-483, EP-A-1473, USP 4270946, GB 2087887 and GB 1522869.

The applicants have found that replacement of the trifluoromethyl group with a pentafluorosulphanyl group also leads to compounds which are herbicidally active.

According to the present invention there is provided a herbicidal dinitroaniline, arylurea, 2-phenylpyridazin-3-one, diphenylether, phenoxyphenoxypropionate, heteroaryloxyphenoxypropionate, arylanilide or substituted phenyl pyrrolidone derivative in which a phenyl or pyridyl group carries a pentafluorosulphanyl group.

As used herein the term "heteroaryl" refers to aromatic heterocylic groups such as pyridyl.

Preferred examples of the compounds of the invention are diphenylether, phenoxyphenoxypropionate, heteroaryloxyphenoxy and arylanilide herbicide derivatives.

In particular the invention provides herbicidal compounds of formula (I); where X is N or CR ; R1 and R3 are independently selected from hydrogen, halogen, or nitro; and R2 is a group YR4 where Y is oxygen or NR5 where R5 is hydrogen or alkyl, and R4 is substituted phenyl or substituted pyridyl.

As used herein the term "alkyl" includes straight or branched carbon chains containing up to six carbon atoms.

Suitable substituents for phenyl groups R4 include nitro, halo, haloalkyl, carboxy and salts, esters and amides thereof, acylsulphonamides, and oxypropionic acid or esters thereof.

Suitable substituents for pyridyl groups R4 include carboxy or salts, esters and amides particularly optionally substituted N-arylamides thereof.

Particular examples of such groups are pyridine carboxamides such as N-aryl nicotinamides.

The salts, esters and amides referred to above are suitably agriculturally acceptable salts, esters or amides. Examples of agriculturally acceptable salts are alkali metal salts such as sodium or potassium, alkaline earth metal salts such as calcium, or quaternary ammonium salts. Suitable agriculturally acceptable esters or amides are well known in the art and include optionally substituted alkyl, alkenyl or alkynyl or aryl esters and amides.

Particular examples of compounds of formula (I) are compounds of formula (II); where R6 and R7 are independently hydrogen or halogen such as fluorine or chlorine; R8 is halo such as chloro or nitro; and R9 is a group OR10 or NRR where R10 is hydrogen, or optionally substituted alkl; R is hydrogen or alkyl and R is hydrogen, alkyl or alkylsulphonyl.

A suitable substituent for alkyl groups R10 is carboxy or alkyl esters thereof.

Preferably R6 is chloro and R7 is hydrogen or fluoro, preferably hydrogen.

R8 is preferably nitro.

R9 is preferably hydroxy, methoxy or OCR13R14CO2R15 where R13 and R14 are independently hydrogen or alkyl such as methyl and R15 is alkyl such as ethyl.

Further examples of compounds of formula (I) are compounds of formula (III); where X is as defined in relation to formula (I): R17 is hydrogen or halogen such as fluorine or chlorine; A is oxygen or NR19 where R19 is hydrogen or optionally substituted alkyl; and R18 is alkyl.

Preferably in compounds of formula (III), X is N or C-Cl or C-NO2.

Preferred compounds of formula (III) are those where R17 is hydrogen or chlorine, most preferably hydrogen.

Suitably A is oxygen, NH or NCH3.

Where A is NH or NCH3, X is preferably C-NO2. 19 Suitable optional substituents for alkyl groups R include alkoxy groups.

Specific examples of groups R19 include methyl, ethyl, n-butyl and ethoxyethyl.

Compounds of formula (III) contain an asymmetric carbon atom and may exist in one or more isomeric forms. The inventions include all forms including resolved isomers and mixtures thereof in all proportions including racemic mixtures.

Yet further examples of compounds of formula (I) are compounds of formula (IV); where R20 is selected from optionally substituted phenyl, or CR21R22R23 where R21, R22 and R23 are selected from alkyl, alkenyl or alkynyl.

As used herein the terms "alkenyl" and "alkynyl" refer to unsaturated chains of carbon atoms of up to 6 carbon atoms. The term "aryl" includes phenyl.

Suitable substituents for phenyl groups R20 include halo such as fluoro or chloro, alkyl such as methyl, alkoxy such as methoxy, cyano, haloalkyl such as trifluoromethyl or pentafluorosulphanyl.

Suitably R20 is phenyl, 4-fluorophenyl or 2,4-difluorophenyl.

When R20 is a group CR21R22R23, R21 and R22 are suitably alkyl groups, in particular methyl and R22 is suitably an alkynyl group such as prop-1-ynyl.

Particular examples of compounds of formula (I) are set out in Tables 1, 2 and 3 below.

TABLE I Refer to Formula (II) Compound No. R6 R7 R8 R9 1 Cl H H OH 2 Cl H H OCH3 3 Cl H NO2 OH 4 Cl H NO2 OCH3 5 Cl H N02 OCH(CH3)C02CH2CH3 6 Cl H NO2 OCH2CO2CH2CH3 7 Cl H NO2 NHS02CH3 8 Cl Cl H OH 9 Cl Cl N02 OH TABLE II Refer to Formula (III) Compound No. X A R17 R18 10 C-Cl O H CH2CH3 11 C-Cl O H OH 12 CH 0 H CH2CH3 13 CH O H OH TABLE II (continued) Compound No. X A R17 R18 14 C-NO2 0 H CH2CH3 15 C-NO2 0 H OH 16* C-NO2 NCH3 H CH2CH3 17 C-NO2 NCH3 H OH 18 C-NO2 NH H CH2CH3 19 C-NO2 NH H OH 20 N O Cl CH2CH20CH2CH3 21 N O Cl OH 22 N o H (CH2)3CH3 23 N O H OH * This compound is in the form of the resolved D isomer.

TABLE III Refer to Formula (IV) Compound No. R20 24 2, 4-di fl uorophenyl 25 4-fluorophenyl 26 phenyl 27 C(CH3)2CCCH3 The compounds of the invention can be prepared using routes which are conventional in the art but starting from the appropriate pentafluorosulphanylphenyl or pyridyl derivative.

In particular compounds of formula (I) may be prepared by reacting a compound of formula (V) where X, and R1 are as defined in relation to formula (I), and R24 is as defined hereinafter; with a compound of formula (VI) where R4 is as defined in relation to formula (I) and one of R24 or R25 is a leaving group and the other is a group HY where Y is as defined in relation to formula (I); in the presence of a base; and thereafter if desired converting a group R4 to a different group R4.

The conversion of a group R4 to a different group R4 can be effected by standard chemical manipulations which are not disruptive to other parts of molecule. Examples of such manipulations are given hereinafter.

Suitable reaction conditions, bases etc, will be readily determined by analogy with the herbicidal compounds of the literature. For example, compounds of formula (II) may be prepared using methods analogues to these described in DE 2753900, USP 4311515 and EP-A-3416. Compounds of formula (III) may be prepared by methods analogous to those described in EP 483 and EP 1473. Compounds of formula (IV) may be prepared by methods analogous to those described in GB 2087887 and USP 4270946.

Certain compounds of formula (V) are described in JACS, 84 3064-3072, 1962. Others described and claimed in copending International Patent application No. PCT/GB92/01636. Others are novel and these may form part of the present invention.

In particular the present invention provides compounds of formula (VII); where R26 and R27 are both halogen in particular chlorine or R26 is amino and R27 is halogen in particular chlorine, or R26 is halogen in particular chlorine and R27 is nitro.

Compounds of formula (VII) where R26 is amino and R27 is halogen may be prepared by halogenation of 4-aminopentafluorosulphanylbenzene.

Suitable reaction conditions are exemplified hereinafter.

Compounds of formula (VII) where both R26 and R27 are halogen may be prepared from the 4-amino-3-chloropentafluorosulphanylbenzene by reaction with copper II chloride in the presence of tert-butyl nitrite as exemplified hereinafter.

Compounds of formula (VII) where R26 is halogen and R27 is nitro may be prepared by nitration of a 4-halopentafluorosulphanyl benzene. Again suitable reaction conditions are exemplified hereinafter.

Compounds of formula (V) where X is N may be prepared by methods analogous to those described in JACS 84, 3064-3072, 1962.

The compounds of formula (I) are active as herbicides and therefore, in a further aspect the invention provides 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 monocotyledonous and dicotyledonous species.

The compounds of formula (I) may be applied directly to the plant (post-emergence application) or to the soil before the emergence of the plant (pre-emergence application). They are particularly useful when applied post-emergence.

The compounds of formula (I) may be used on their own to inhibit the growth of, severely damage, or kill plants but are preferably used in the form of a composition comprising a compound of the invention in admixture with a carrier comprising a solid or liquid diluent.

Therefore, in yet a further aspect the invention provides plant growth inhibiting, plant damaging, or plant killing compositions comprising a compound of formula (I) as hereinbefore defined and an inert carrier or 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 triisopropylnaphthalenesulphonic acid.

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

The aqueous solutions or dispersions may be prepared by dissolving the active ingredient in water or an organic solvent optionally containing wetting or dispersing agent(s) and then, when organic solvents are used, adding the mixture so obtained to water optionally containing wetting or dispersing agent(s). Suitable organic solvents include, for example, ethylene di-chloride, 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 comprising the active ingredient which has been finely divided and which has been dispersed in water in the presence of a surface-active agent and a suspending agent.

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

The rate of application of the compounds of the invention will depend on a number of factors including, for example, the compound chosen for use, the identity of the plants whose growth is to be inhibited, the formulations selected for use and whether the compound is to be applied for foliage or root uptake. As a general guide, however, an application rate of from 0.001 to 20 kilograms per hectare is suitable while from 0.025 to 10 kilograms per hectare may be preferred.

The compositions of the invention may comprise, in addition to one or more compounds of the invention, one or more compounds not of the invention but which possess biological activity for example herbicides, fungicides, insecticides (optionally with an insecticide synergist) and plant growth regulators. Accordingly in yet a still further embodiment the invention provides a herbicidal composition comprising a mixture of at least one herbicidal compound of formula (I) as hereinbefore defined with at least one other herbicide.

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

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

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

The following Examples illustrate the invention.

EXAMPLE 1 This Example illustrates the preparation of compound 1 in Table 1.

Staae 1: Preparation of 4-Aminopentafluorosulphanylbenzene.

4-Nitropentafluorosulphanyl benzene (7.5g), (prepared as described in JACS, 84, 3064-3072, 1962) isopropanol (70mls) and water (12mls), was treated with reduced iron powder (259) and concentrated hydrochloric acid (lmls). The mixture was stirred and gently refluxed for 2 hours, filtered and concentrated in vacuo.

The residual brown oil was partitioned between ether and water. The ether phase was dried (MgS04) and filtered. The ether was evaporated in vacuo and gave the described product as a brown oil, which crystallised on standing, (6.3g). 1H NMR (CDCl3): 4.0(2H,s); 6.6(2H,d); 7.5(2H,d).

Staae 2: Preparation of 4-Amino-3-chloropentafluorosulphanylbenzene.

4-Aminopentafluorosulphanyl benzene (7.25g) from Stage 1, in dry acetonitrile (75mls), was stirred at 450C. N-Chlorosuccinimide (3.95g) was added and stirring continued for 3 hours. The mixture was concentrated in vacuo and the residue was treated with ether and filtered. The filtrate was evaporated in vacuo and gave a brown oil.

The oil was purified by silica gel column chromatography in ether:hexane (50:50) and gave the desired compound as a grey solid (5.95g).

M.pt 56-58"C. 1H NMR (CDC13); 4.4(2H,s); 6.7(1H,s); 7.45(1H,d); 7.65(1H,m).

Stage 3: Preparation of 3,4-dichloropentafluorosulphanylbenzene.

A suspension of copper II chloride (29) in dry acetonitrile (50mls) was stirred under nitrogen, with ice bath cooling and treated with tertbutyl nitrite (2g). After h hour a solution of 4-amino-3-chloropentafluorosulphonyl benzene (III) (3.29) in acetonitrile (5mls), was added dropwise. The dark mixture was left at room temperature overnight.

The mixture was poured slowly into excess 20% hydrochloric acid and extracted with ether. The organic phase was washed with water, dried (MgSO4) and filtered. The ether was evaporated in vacuo and gave the desired product as a brown oil, which crystallised on standing (3.lug).

M.pt 42-430C. 1H NMR (CDCl3): 7.55(2H,m); 7.88(1H,m).

Staae 4: Preparation of 3-(2-chloro-4-pentafluorosulphanylphenoxy) benzoic acid.

3-Hydroxybenzoic acid (1.lug) was added to a stirred solution of potassium hydroxide (0.9lug) in methanol (25mls). The solution was evaporated in vacuo and gave a white solid. This was dispersed in dry DMS0 (20mls) and potassium carbonate (2.89), 3,4-Dichloropentafluorosulphanyl benzene (IV) (2.2g) and caesium fluoride (0.1g) were added. The mixture was stirred at 140"C for 17 hours.

The cool reaction mixture was poured onto excess ice/water and extracted with ether. The organic phase was discarded. The aqueous phase was acidified with 2M hydrochloric acid and extracted with ether. The organic phase was washed with water, dried (MgS04) and filtered. The ether was evaporated in vacuo and gave a brown semi-solid (1.75g).

Purification was carried out by conversion to the methyl ester followed by hydrolysis to the pure acid (see Examples 2 and 3 below).

EXAMPLE 2 This Example illustrates the preparation of methyl 3-(2-chloro-4-pentafluorosulphanylphenoxy)benzoate (Compound 2 in Table 1).

The crude acid from stage 4 of Example 1 (2.8g) was treated with thionyl chloride (40mls). The solution was stirred and refluxed for 2 hours then evaporated in vacuo and gave the crude acid chloride as a brown oil. This was treated with methanol (25mls). After 2 hours the solution was evaporated in vacuo and gave a brown oil.

The oil was purified by column chromatography with silica gel and ether:hexane:acetic acid, (60:40:5) and gave Compound No. 2 as a yellow oil (1.15g). 1H NMR (CDCl3): 3.9(3H,s); 6.9(1H,d); 7.25(1H,m); 7.5(iH,t); 7.6(1H,m); 7.65(1H,m); 7.9(2H,m).

EXAMPLE 3 This Example illustrates the preparation of 3-(2-chloro-4-pentafluorosulphanylphenoxy) benzoic acid (Compound No. 1 in Table 1) in pure form.

Sodium hydroxide (0.15g) in water (5mls) was added dropwise to a stirred solution of the methyl ester from Example 2 (0.95g) in isopropanol (20mls). After 2 hours the red solution was added to excess water and extracted with ether. The organic phase was discarded. The aqueous phase was acidified with 2M hydrochloric acid and extracted with ether. The organic phase was washed with water, dried (MgS04) and filtered. The ether was evaporated in vacuo and gave Compound No. 1 as a beige solid, which was recrystallised from carbon tetrachloride (0.25g). M. pt 151-152"C. 1H NMR (CDCl3): 6.95(1H,d); 7.3(1H,m); 7.55(1H,t); 7.6(1H,m)); 7.75(1H,s); 7.9(1H,m); 8.0(1H,d).

EXAMPLE 4 This Example illustrates the preparation of methyl 5-(2-chloro-4pentafluorosulphanylphenoxy)-2-nitrobenzoate (Compound No. 4 in Table 1).

The methyl ester (1.77g) prepared as described in Example 2 was added with stirring to an ice cold mixture of 1,2-dichloromethane (7.5mls) and concentrated sulphuric acid (llmls). Potassium nitrate (0.7g) was slowly added to the stirred mixture which was then allowed to assume room temperature overnight.

The mixture was poured slowly onto excess ice/water and extracted with ether. The organic phase was washed with water, dried MgS04 and filtered.

The ether was evaporated in vacuo and gave a brown oil (1.75g).

The oil was purified by silica gel preparative plate chromatography in ether:acetic acid, (60:40:5) and gave Compound No. 4 as a pale yellow oil which crystallised on standing (0.15g). M.pt 95-96 C. 1H NMR (CDCl3): 3.9(3H,s); 7.1(1H,m); 7.15(1H,s); 7.2(1H,d); 7.75(1H,m); 7.95(1H,m); 8.05(1H,d).

EXAMPLE 5 This Example illustrates the preparation of 5-(2-chloro-4-pentafluorosulphanylphenoxy)-2-nitro benzoic acid (Compound No. 3 in Table 1).

Sodium hydroxide (O.lg) in water (5mls) was added dropwise to a stirred solution of the Compound No. 4 (0.8g) in isopropanol (25mls).

After standing overnight the solution was poured onto excess 1M hydrochloric acid. The mixture was extracted with ether. The organic phase was washed with water, dried (MgSO4) and filtered. The ether was evaporated in vacuo and gave Compound No. 3 as a yellow oil (0.7g). This was crystallised from carbon tetrachloride and gave Compound No. 3 as a pale yellow solid (0.359). M.pt 165-1660C. 1H NMR (CDCl3): 7.1(1H,m); 7.2(2H,m); 7.75(1H,m); 7.95(1H,s); 8.04(1H,d).

EXAMPLE 6 This Example illustrates the preparation of 5-(2-chloro-4-pentafluorosulphanylphenoxy)-2-nitrobenzoic acid (Compound No. 3 in Table I).

The crude acid from Example 2 (2.159) was slowly added with stirring, to an ice cold mixture of 1,2-dichloroethane (9.5mls) and concentrated sulphuric acid (14mls). Potassium nitrate (0.569) was slowly added to the stirred mixture which was then allowed to assume room temperature over 2 hours.

The mixture was poured slowly onto excess ice/water and extracted with ether. The organic phase was washed with water, dried (MgSO4) and filtered. The ether was evaporated in vacuo and gave crude Compound No. 3 as a brown oil (2.1g).

The oil was purified by silica gel preparative plate chromatography in ether:hexane:acetic acid (60:40:5) and gave Compound No. 3 as a yellow oil which crystallised on standing (0.16g). 1H NMR (CDCl3): 7.1(1H,d); 7.2(2H,m), 7.75(1H,d); 7.95(1H,s); 8.02(1H,d).

EXAMPLE 7 This Example illustrates the preparation of ethyl 5'-(2-chloro-4-pentafluorosulphanylphenoxy)-2'-nitrobenzoyl-2-oxy propionate (Compound 5 in Table I).

Compound No. 3 (0.3g) in dry DMF (6mls) was treated with anhydrous potassium carbonate (0.5g) and stirred for i hour. Ethyl-2-bromo propionate (0.55g) was added and the mixture left at room temperature overnight.

The mixture was poured onto excess cold water and extracted with ether. The organic phase was washed with water, dried (MgSO4) and filtered. The ether was evaporated in vacuo and gave crude Compound No. 5 as a yellow oil (0.6g).

The oil was purified by silica gel preparative plate chromatography in ether:hexane:acetic acid (60:40:5) and gave Compound No. 5 as a pale yellow oil (0.28g). 1H NMR (CDCl3): 1.3(3H,t); 1.6(3H,d); 4.25(2H,q); 5.35(1H,q); 7.05(1H,d); 7.2(1H,d); 7.3(1H,s,); 7.75(1H,d); 7.95(1H,s); 8.05(1H,d).

EXAMPLE 8 This Example illustrates the preparation of ethyl 5-(2-chloro-4-pentafluorosulphanylphenoxy)-2-nitrobenzoyloxyacetate (Compound No. 6 in Table I).

Compound No. 3 (O.1g), in dry DMF (2mls), was treated with anhydrous potassium carbonate (0.14g) and stirred for i hours. Ethyl bromoacetate (0.167g) was added and the mixture stirred at room temperature for 2 hours.

The mixture was poured onto excess cold water and extracted with ether. The organic phase was washed with water1 dried (MgSO4) and filtered. The ether was evaporated in vacuo and gave crude Compound No. 6 as a yellow oil (0.16g).

The oil was purified by silica gel preparative plate chromatography in ether:hexane:acetic acid (60:40:5) and gave Compound No. 6 as a pale yellow oil (0.08g). 1H NMR (CDCl3): 1.3(3H,t); 4.25(2H,q); 4.85(2H,s); 7.1(1H,d); 7.2(1H,d); 7.3(1H,s); 7.75 (lH,d); 8.95(1H,s); 8.1(1H,d).

EXAMPLE 9 This Example illustrates the preparation of 5-(2-chloro-4-pentafluorosulphanylphenoxy)-2-nitrobenzoyl methane sulphonamide (Compound No. 7 in Table I).

Compound No. 3 (0.3g) and thionyl chloride (5mls) were refluxed for 2 hours then concentrated in vacuo to give the crude acid chloride. This was dissolved in methyl isobutyl ketone (2mls), then added slowly to a stirred mixture of methane sulphonamide (0.105g), anhydrous potassium carbonate (0.135g) and methyl isobutyl ketone (5mls) at 100 "C. The mixture was stirred at 1300C for 2 hours.

After cooling the mixture was treated with excess cold water, acidified with 2M hydrochloric acid and extracted with ethyl acetate. The organic phase was washed with water, dried (MgSO4) and filtered. The ethyl acetate was evaporated in vacuo and gave crude Compound No. 7 as a yellow gum (0.159).

The gum was recrystallised from chloroform and gave Compound No. 7 as a pale yellow solid (0.075g). M.pt. 196-197"C. 1H NMR (CDCl3) + trace D6DMSO): 3.4(3H,s); 7.03(1H,s); 7.15(1H,d); 7.25(1H,d); 7.78(1H,d); 7.95(1H,s); 8.2(1H,d).

EXAMPLE 10 This Example illustrates the preparation of 3-(2,6-dichloro-4-pentafluorosulphanylphenoxy)benzoic acid (Compound No. 8 in Table I).

Staoe 1: Preparation of 3,5-dichloro-4-aminopentafluorosulphanyl benzene.

4-Aminopentafluorosulphanylbenzene (20.09) in dry acetonitrile (150 cm3) was stirred at ambient temperature and treated with N-chlorosuccinimide (26.7g) in portions over 2 hours. The mixture was stirred for 18 hours, heated to reflux for 1h hour and evaporated under reduced pressure. The residue was partitioned between hexane (600 cm3) and aqueous sodium bicarbonate. The hexane fraction was washed twice with water and dried (anhydrous magnesium sulphate) and evaporated under reduced pressure to give the required product as a pale brown solid.

1H NMR b(CDCl3) 4.80(broad,2H), 7.60(s,2H).

Stage 2: Preparation of 3,4,5-trichloropentafluorosulphanylbenzene 4-Amino-3,5-dichloropentafluorosulphahnylbenzene (5.76g) in dry acetonitrile (30 cm ) was added dropwise to a stirred mixture of copper (II) chloride 3.23g) and tertiary butylnitrite (3.1g, 3.56 cm ) in dry acetonitrile (50 cm ) at 60-5 under an atmosphere of nitrogen. On complete addition the reaction was kept at 60-5" for 1 hour, cooled and poured into water (700 cm3). The mixture was acidified with concentrated hydrochloric acid and extracted with hexane (2 x 250 cm3). The hexane fractions were washed with water and dried (anhydrous magnesium sulphate).

The solvent was evaporated under reduced pressure to give a brown liquid which was distilled at 120-130"/12mm Hg. to give a mixture of the required product (A) and 3,5-dichloropentafluorosulphanylbenzene (B).

(A) H NMR #(CDCl3) 7.80(s) Molecular ion 306; (B) H NMR #(CDCl3) 7.54(d,2H), 7.67.(d,2H).

Stage 3: Preparation of 3,5-dichloro-4-fluoropentafluorosulphanylbenzene.

The mixture from Stage 2 (6.99) in dry sulpholane (21 cm3) was treated with dry potassium fluoride (2.09) and tetraphenylphosphonium bromide (catalyst; 0.18g). The mixture was stirred and heated to 200-205 under an atmosphere of nitrogen for 5 hours. The mixture was cooled to ambient temperature and diluted with water (1 litre) and extracted with hexane (3 x 300 cm3). The hexane fractions were washed with water (2 x 200 cm3), dried (anhydrous magnesium sulphate) and the solvent evaporated under reduced pressure to give a mixture containing the desired product and 3-Chloro-4,5-difluoropentafluorosulphanylbenzene (B) in the ratio 8:1 as a brown liquid, together with unreacted 3,5-dichloropentafluorosulphanylbenzene present in the starting material.

The proportion of the product (B) obtained in repeat preparations-was variable. The minor product (B) was eliminated during subsequent reaction and isolation or purfication of the end-product in Stage 4.

A) Molecular ion 290 (B) Molecular ion 274 1H NMR b(CDCl3) (A) 7.77(d) Staoe 4: Preparation of Compound 8 in Table I.

3-Hydroxy benzoic acid (0.476g) was added to a stirred solution of potassium hydroxide (0.39g) in methanol (louis). The solution was evaporated in vacuo and gave a white solid. This was dispersed in dry DMSO (louis) and potassium carbonate (1.4g) added. The mixture was stirred and 3,5-dichloro-4-fluoropentafluorosulphanylbenzene from Stage 3 (1g), slowly added. Stirring was continued for 3 hours at room temperature then 2 hours at 50"C.

The cool reaction mixture was poured onto excess ice and dilute hydrochloric acid and gave a beige precipitate. This was filtered off then dried in air and gave a beige solid (1.lug).

Part of the solid (0.29) was recrystallised from carbon tetrachloride and gave Compound No. 8 as a cream solid (0.11g). M.pt 215-217"C. 1H NMR (CDCl3 + trace DMSO): 6.4(1H,s); 7.1(1H,d); 7.45(2H,m); 7.84(1H,d); 7.86(2H,s).

EXAMPLE 11 This Example illustrates the preparation of 5-(2,6-dichloro-4-pentafluorosulphanylphenoxy)-2-nitrobenzoic acid (Compound No. 9 in Table I).

Crude 3-(2,6-dichloro-4-pentafluorosulphanylphenoxy) benzoic acid (Compound No. 8) (0.89), was slowly added with stirring, to an ice cold mixture of 1,2-dichloroethane (5mls) and concentrated sulphuric acid (7mls).

Potassium nitrate (0.4g) was slowly added to the stirred mixture, which was then allowed to assume room temperature over 2F hours.

The mixture was poured slowly onto excess ice/water and extracted with ether. The organic phase was washed with water, dried (MgSO4) and filtered.

The ether was evaporated in vacuo and gave a beige solid (0.8g).

The solid was recrystallised from carbon tetrachloride and gave Compound No. 9 as a beige solid (0.55g). M. pt 196-198"C. 1H NMR (CDC13 + trace DMSO): 7.0(1H,d); 7.1(1H,s); 7.85(2H,s); 8.0(1H,d).

EXAMPLE 12 This Example illustrates the preparation of ethyl-2[4-(2-chloro-4-pentafluorosulphanylphenoxy)phenoxy]propionate.

(Compound No. 10 in Table II).

3,4-Dichloropentafluorosulphanylbenzene (0.5g) prepared as described in Example 1 stage 3 in dry DMSO (louis), was treated with Ethyl-2-(4-hydroxy phenoxy)propionate (0.4g) and anhydrous potassium carbonate (lg). The mixture was stirred at 1300C for 7 hours. After cooling the mixture was added to excess cold water and extracted with ether. The organic phase was washed with water, dried (MgSO4) and filtered. The ether was evaporated in vacuo and gave a brown oil (0.45g).

The oil was purified by silica gel preparative plate chromatography, in ether:hexane: acetic acid (60:40:5) and gave Compound No. 10 as a yellow (0.18g). 1H NMR (CDCl3): 1.28(3H,t); 1.65(3H,d); 4.25(2H,q); 4.72(1H,q); 6.75(1H,d); 6.78-7.0(4H,m); 7.53(1H,d); 7.85(1H,s).

EXAMPLE 13 This Example illustrates the preparation of 2-[4-(4-pentafluorosulphanyl phenoxy)phenoxy] propionic acid (Compound No. 13 in Table II) and ethyl 2-[4-(4-pentafluorosulphanyl phenoxy)phenoxy] propionate (Compound No. 12 in Table 2) Stage 1: Preparation of 4-chloropentafluorosulphanylbenzene.

A suspension of copper II chloride (4g) in dry acetonitrile (lOOmls), was stirred under nitrogen with ice bath cooling and treated with tert butyl nitrite (49). After h hour a solution of 4-amino pentafluorosulphanyl benzene (5.4g) in acetonitrile (12mls) was added dropwise. The dark mixture was left at room temperature overnight.

The mixture was poured slowly into excess 20% hydrochloric acid and Extracted with ether. The organic phase was washed with water, dried (MgSO4) and filtered. The ether was evaporated in vacuo and gave a brown oil (4.8g).

The oil (1g) was purified by silica gel preparative plate chromatography in ether:hexane:acetic acid, (60:40:5) and gave the desired compound as an orange oil (0.6g). 1H NMR (CDCl3): 7.45(2H,d); 7.7(2H,d).

Stage 2: Preparation of 2-[4-(4-pentafluorosulphanyl phenoxy)phenoxy] propionic acid (Compound No. 13 in Table II).

4-Chloropentafluorosulphanylbenzene from Stage 1 (lg) in dry DMSO (louis) was treated with ethyl 2-(4-hydroxy phenoxy)propionate (1.2g), anhydrous potassium carbonate (2.5g) and caesium fluoride (lug). The mixture was stirred at 1300C for 18 hours.

The cooled mixture was poured onto excess ice/water and extracted with ether. The organic phase was discarded. The aqueous phase was acidified with 2M hydrochloric acid and extracted with ether. The organic phase was washed with water, dried MgS04 and filtered. The ether was evaporated in vacuo and gave a yellow oil.

The oil was purified by silica gel preparative plate chromatography in ether:hexane:acetic acid (60:40:5), and gave 2-[4-(4-pentafluorosulphanyl phenoxy)phenoxy] propionic acid (Compound No. 13 in Table II) as a yellow oil (0.15g). 1H NMR (CDCl3): 1.65(3H,d); 4.75(1H,q); 6.8-7.0(6H,m); 7.71(2H,d).

Stage 3: Preparation of ethyl 2-[4-(4-pentafluorosulphanyl phenoxy)phenoxy] propionate (Compound No. 12 in Table II) The acid (0.259) from stage 2 was treated with thionyl chloride (5mls).

The solution was stirred and refluxed for 2 hours then evaporated in vacuo and gave the acid chloride as a yellow oil. The oil was treated with ethanol (5mls) and stirred for 2 hours. The ethanol was removed in vacuo and gave Compound No. 12 as a pale yellow oil (0.259). 1H NMR (CDCl3): 1.25(3H,t); 1.65(3H,d); 4.25(2H,q); 4.7(1H,q); 6.8-7.0(6H,m); 7.7(2H,d).

EXAMPLE 14 This Example illustrates the preparation of ethyl 2-[4-(2-nitro-4-pentafluorosulphanylphenoxy)phenoxy]propionate (Compound No.

14 in Table II).

Staae 1: Preparation of 4-chloro-3-nitropentafluorosulphanylbenzene.

4-Chloropentafluorsulphanylbenzene (2.49) was dissolved in an ice cold mixture of 1,2-dichloroethane (15mls) and concentrated sulphuric acid (22mls) with stirring. Potassium nitrate (2.59) was slowly added and the mixture left at room temperature overnight.

The mixture was poured on to ice/water then extracted with ether. The organic phase was washed with water, dried (MgSO4) and filtered. The ether was evaporated in vacuo and gave brown oil (2 .5go.

The oil (0.759) was purified by silica gel preparative plate chromatography in ether:hexane:acetic acid, (60:40:5) and gave the desired compound as a pale yellow oil (0.69). 1H NMR CDCl3: 7.7(D,1H); 7.9(DM,1H); 8.3(SM,1H).

Stage 2: Preparation of Compound No. 14 in Table II.

4-Chloro-3-nitropentafluorosulphanylbenzene from Stage 1 (0.85g) in dry methyl isobutyl ketone (louis) was treated with ethyl 2-(4-hydroxy phenoxy)propionate (0.65g) and anyhydrous potassium carbonate (2g). The mixture was stirred at 1250C for 5 hours. After cooling it was poured onto ice/water and extracted with ether. The organic phase was washed with water, dried (MgS04) and filtered. The ether was evaporated in vacuo and gave brown oil (1.4g).

The oil was purified by silica gel preparative place chromatography in ether:hexane:acetic acid (60:40:5) and gave Compound No. 14 as an orange oil (0.5g). 1H NMR CDCl3): 1.3(3H,t); 1.65(3H,t); 4.25(2H,q); 4.75(1H,q); 6.95(3H,h); 7.05(2H,d); 7.8(1H,m); 8.35(1H,s).

EXAMPLE 15 This Example illustrates the preparation of ethyl 2-[4-(2-nitro-4-pentafluorosulphanylphenylamino)phenoxy] propionate (Compound No. 18 in Table II).

4-Chloro-3-nitropentafluorosulphanylbenzene (1g) from Example 14 Stage 1 in methyl isobutyl ketone (25mls) was treated with ethyl 2-(4-aminophenoxy)propionate hydrochloride (1g), anhydrous potassium carbonate (2.5g) and dry DMF (20mls). The mixture was stirred at 125"C for 7 hours.

After cooling it was poured onto excess dilute hydrochloric acid and extracted with ether. The organic phase was washed with water, dried (MgS04) and filtered. The ether was evaporated in vacuo and gave a brown oil.

The oil was purified by silica gel preparative plate chromatography in ether:hexane:acetic acid, (60:40:5) and gave Compound No. 14 as an orange oil (0.18g). 1H NMR (CDCl3): 1.3(3H,t); 1.65(1H,d); 4.25(2H,q); 4.78(1H,q); 6.95(3H,m); 7.2(2H,d); 7.65(1H,d); 8.63(1H,s); 9.6(1H,s).

EXAMPLE 16 This Example illustrates the preparation of D(+) Ethyl 2-[4-(N-methyl-2-nitro-4-pentafluorosulphanylphenylamino)phenoxy]propionate (Compound No. 16 in Table II).

4Chloro-3-nitropentafluorosulphanylbenzene (0.25g) from Example 14 Stage 1 in diglyme (20mls) was treated with D(+)-Ethyl 2-(N-methyl-4-amino phenoxy)propionate (0.25g). The solution was stirred at 2200C for 6 hours.

After cooling the diglyme was evaporated in vacuo and gave a dark brown gum. This was extracted with ether, which was decanted and evaporated in vacuo and gave a dark brown oil.

The oil was purified by silica gel preparative plate chromatography in ether:hexane:acetic acid, (60:4-:5) and gave Compound No. 16 as an orange oil (0.329). 1H NMR (CDCl3): 1.25(3H,t); 1.6(3H,d); 3.3 (3H,s); 4.25(2H,q); 4.7(1H,q); 6.8(2H,d); 7.0(2H,d); 7.13(1H,d); 7.73(1H,d); 8.1 (1H,s).

EXAMPLE 17 This Example illustrates the preparation of N-(2,4-difluorophenyl)-2 (3-Pentafluorosulphanylphenoxy)nicotinamide (Compound No. 24 in Table 3).

Stage 1: Preparation of 3-pentafluorosulphanylaniline Reduced iron powder (8.609) was added to a stirred solution of 3pentafluorosulphanylnitrobenzene (2.65g) in a mixture of isopropanol (27ml), water (6ml) and concentrated hydrochloric acid (0.3ml). The resulting mixture was heated under reflux for 1 hour, and was then allowed to cool slightly before being filtered through Hyflo. The Hyflo was washed with more isopropanol, and the combined filtrates were evaporated in vacuo. The residue was dissolved in a little diethyl ether and the solution was treated with solid sodium hydrogen carbonate, then dried over magnesium sulphate. After filtration to remove the inorganics the solution was evaporated in vacuo and the oily residue was distilled in a Kugelrohr apparatus.The title compound was collected as a colourless oil, yield 1.909, bp 1100C (oven temperature) at 12mmHg, which crystallised on standing (mp 32-350C).

1H nmr data (CDCl3): 33.65-3.95 (2H, broad s), 6.76(1H, dd), 6.98-7.29 (3H, m) Stage 2: Preparation of 3-pentafluorosulphanylphenol A stirred solution of 3-pentafluorosulphanylaniline (2.56g) in a mixture of concentrated sulphuric acid (6ml) and water (8ml) was cooled to ca 00C and treated dropwise with a solution of sodium nitrite (1.32g) in water (4ml), at such a rate that the reaction temperature did not exceed 40C. The resultant solution was added rapidly to a stirred mixture of concentrated sulphuric acid (16ml) and water (14ml) at 100 C. This mixture was then allowed to cool, and was extracted with diethyl ether (3x25ml).The combined ether extracts were dried over magnesium sulphate, and evaporated in vacuo to leave a red oil, which was separated by chromatography on silica gel eluting with a mixture of ethyl acetate and hexane (9:1). The crude product thus obtained was distilled in a Kugelrohr apparatus to give the title compound as a pale yellow oil.

yield 1.10g bp 70 C (oven temperature) at 0.6mmHg, which crystallised on standing (mp 61-640C).

1H nmr data (CDCl3): 86.10-6.40 (1H, broad s), 6.96 (1H, m), 7.21-7.37 (3H, m) Staae 3: Preparation of 2-(3-pentafluorosulphanylphenoxy)nicotinic Acid A solution of a mixture of 3-pentafluorosulphanylphenol (1.01g) and 2chloronicotinic acid (0. 729) in dry tetrahydrofuran (lOml) was added dropwise, under a dry nitrogen atmosphere, to a 60% suspension of sodium hydride in oil (0.389), with stirring. The resultant yellow suspension was Heated slowly to 180 C, during which time the solvent was removed in a stream of nitrogen. The solid residue was heated at 180 C for a further 2 hours before being allowed to cool, and was then partitioned between water and diethyl ether. The water layer was separated, and acidified to pH 3 with acetic acid. The precipitate was filtered off, washed with water and air dried, and was then recrystallised from ethyl acetate/hexane to give the title compound as an off-white crystalline solid, mp 183-1850C, yield 1.04g.

1H nmr data (CDCl3/d6 DMSO): 87.18 (1H, m), 7.36 (1H, m), 7.51-7.72 (3H, m), 8.15-8.25 (2H, m), 13.27 (1H, broad s) Staae 4: Preparation of Compound No. 24 in Table 1.

A mixture of 2-(3-pentafluorosulphanylphenoxy)nicotinic acid (0.10g) and thionyl chloride (2ml) was heated under reflux for 1 hour, then evaporated in vacuo to leave an off-white solid. This was dissolved in dry chloroform (5ml), and the solution was treated dropwise with a mixture of triethylamine (0.04ml) and 2,4-difluoroaniline (0.04g). The resulting mixture was heated under reflux for 1 hour, and was then cooled and washed with water. The organic phase was separated, dried over magnesium sulphate, and evaporated in vacuo to leave a light brown solid. This was purified by preparative thin layer chromatography on silica gel plates, eluting with methylene chloride, to afford the title compound as an off-white solid, mp 170-171 C, yield 0.09g.

1H nmr data (CDCl3): 36.82-6.97 (2H, m), 7.27 (lah, m), 7.41 (lah, m), 7.57 (1H, m), 7.68-7.76 (2H, m), 8.25 (1H, m), 8.51 (lH, m), 8.72 (1H, m), 9.91 (1H, broad s) EXAMPLE 18 This Example illustrates the preparation of N-(4-fluorophenyl)-2 (3Pentafluorosulphanylphenoxy)nicotinamide (Compound No. 25 in Table 3).

A mixture of 2-(3-pentafluorosulphanylphenoxy)nicotinic acid (0.499) and thionyl chloride (5ml) was heated under reflux for 2 hours, then evaporated in vacuo to leave an off-white solid. This was dissolved in dry tetrahydrofuran (5ml), and triethylamine (0.40ml) was added1 resulting in a white suspension.

This was treated, with stirring, with 4-fluoroaniline (0.16g), and the mixture was left to stand overnight. The resulting light brown suspension was quenched with brine, and the mixture was extracted with diethyl ether (2x25ml). The combined ether extracts were washed with brine, dried over magnesium sulphate, and evaporated in vacuo to leave a light brown solid.

This was recrystallised from carbon tetrachloride to afford the title compound as a buff crystalline solid, mp 142-1430C, yield 0.49g.

1H nmr data (CDCl3): 36.99-7.11 (2H, m), 7.25 (1H, m), 7.39 (1H, m), 7.53-7.79 (5H, m), 8.25 (1H, m), 8.72 (1H, m), 9.49 (1H, broad s) EXAMPLE 19 This Example illustrates the preparation of N-(1,1-dimethyl-2-butynyl)-2 (3-Pentafluorosulphanylphenoxy)nicotinamide (Compound No. 27 in Table III).

A mixture of 2-(3-pentafluorosulphanylphenoxy)nicotinic acid (0.28g) and thionyl chloride (4ml) was heated under reflux for 2 hours, then evaporated in vacuo to leave an off-white solid. This was dissolved in dry tetrahydrofuran (5ml), and triethylamine (0.33ml) was added, resulting in a white suspension.

This was treated, with stirring, with 1-amino-1,1-dimethyl-2-butyne hydrochloride (0.115g), and the mixture was left to stand overnight. The resulting light brown suspension was quenched with brine, and the mixture was extracted with diethyl ether (2x25ml). The combined ether extracts were washed with brine, dried over magnesium sulphate, and evaporated in vacuo to leave a colourless gum. This was purified by preparative thin layer chromatography on silica gel plates, eluting with a mixture of ethyl acetate and hexane (1:1), to afford the title compound as a colourless gum, yield 0.225g.

1H nmr data (CDCl3): 81.74 (6H, s), 1.82 (3H, s), 7.20 (1H, m), 7.38 (1H, m), 7.50-7.73 (3H, m), 7.89 (1H, broad s), 8.20 (1H, m), 8.65 (1H, m) Biological Data The herbicidal activity of the compounds was tested as follows: Each chemical was formulated by dissolving it in an appropriate amount, dependent on the final spray volume, of a solvent/surfactant blend which comprised 78.2 gm/litre of Tween 20 and 21.8 gm/litre of Span 80 adjusted to 1 litre using methylcyclohexanone. Tween 20 is a Trade Mark for a surface-active agent comprising a condensate of 20 molar proportions of ethylene oxide with sorbitan laurate. Span 80 is a Trade Mark for a surface-active agent comprising sorbitan mono-laurate.If the chemical did not dissolve, the volume was made up to 5cm3 with water, glass beads were added and this mixture was then shaken to effect dissolution or suspension of the chemical, after which the beads were removed. In all cases, the mixture was then diluted with water to the required spray volume. If sprayed independently, volumes of 10cm3 and 14cm3 were required for pre-emergence and post-emergence tests respectively; if sprayed together, 20cm3 was required.

The sprayed aqueous emulsion contained 4% of the initial solvent/surfactant mix and the test chemical at an appropriate concentration.

The spray compositions so prepared were sprayed onto young pot plants (post-emergence test and flooded conditions test) at a spray volume equivalent to 400 litres per hectare. The flooded conditions test was used for species which are of relevance to the growth of paddy-rice crops. In this test, the plant species were contained in 4cm diameter Aqua pots which had been kept moist for a minimum of 48 hours before spraying. The tubs were then kept moist for a further 24 hours after spraying and then flooded to a depth of approximately 2cm. This water level was maintained for the duration of the test.Damage to plants was assessed 13 days after spraying for the post-em test and 20 days for the flooded conditions by comparison with untreated plants, on a scale of O to 9 where 0 is 0% damage, 1 is 1-5% damage, 2 is 6-15% damage, 3 is 16-25% damage, 4 is 26-35% damage, 5 is 36-59% damage, 6 is 60-69% damage, 7 is 70-79% damage, 8 is 80-89% damage and 9 is 90-100% damage.

In a test carried out to detect pre-emergence herbicidal activity, crop seeds were sown at 2 cm depth (i.e. sugar beet, cotton, rape, winter wheat, maize, rice, soya) and weed seeds at 1 cm depth beneath compost and sprayed with the compositions at a spray volume equivalent to 400 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 O to 9.

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

TABLE IV Compound Rate of Pre- or TEST PLANTS (Test Plants - see Table 5 No Application Post- (Test Plants - see Table 5 ) g/ha Emergence Application BV BN GM ZM OS TA PA CA GA AR EH IH AT XT AF AM SH SV EC CE 3 125 Pre 0 0 3 0 3 0 0 3 0 0 3 0 0 - 0 0 0 0 2 0 125 Post 5 9 4 3 0 2 6 9 5 7 - 5 4 6 2 2 7 4 5 2 4 250 Pre 3 4 0 0 1 0 8 9 4 9 - 0 2 - 2 0 5 9 2 1 125 Post 7 6 5 6 3 3 8 9 9 9 9 9 9 9 2 5 4 5 5 6 5 125 Post 9 9 6 5 3 4 9 8 9 9 - 9 5 9 5 2 5 8 7 4 125 Pre 0 3 0 0 0 0 0 0 0 0 0 0 0 - 0 0 0 2 0 0 6 125 Pre 2 0 0 0 1 0 0 3 0 0 3 0 0 - 0 0 0 0 0 0 62.5 Post 5 8 6 4 2 3 8 8 9 9 - 7 5 9 3 3 5 5 5 3 7 250 Pre 3 9 0 5 - 0 0 0 2 0 62.5 Post 7 5 2 3 1 2 6 8 5 9 9 6 6 5 1 2 1 5 4 1 10 500 Post 0 0 0 6 0 7 2 0 0 4 2 2 1 3 2 0 0 4 1 0 24 250 Post 6 7 5 3 4 3 6 9 - 9 8 5 7 7 4 3 2 5 3 3 250 Pre 8 8 4 3 0 0 9 9 9 9 - 6 5 0 5 5 5 9 5 0 25 1000 Post 6 7 5 3 0 1 6 8 7 8 5 6 6 2 2 3 6 3 4 1000 Pre 9 9 2 2 2 1 7 8 5 9 - 5 6 - 1 5 8 9 8 1 27 1000 Post 2 2 3 1 - 0 2 5 5 6 - 4 2 2 0 2 0 2 3 1 1000 Pre 3 0 1 1 2 1 0 2 4 5 - 2 0 - 0 0 - 3 0 0 TABLE V Abbreviations used for Test Plants BV - Sugar beet BN - Rape GH - Cotton GM - Soybean ZM - Maize OS - Rice TA - Winter wheat PA - Polvaonum aviculare CA - Chenopodium album AR - Amaranthus retroflexus BP - Bidens pilosa EH - Euphorbia heterophvlla IH - Ipomoea hederacea (post-emeraence) IL - Ipomoea lacunosa (pre-emeraence) AT - Abutilon theophrasti XT - Xanthium strumarium AF - Avena fatua AM - Alopecurus mvosuroides AE - Aoroovron repens SH - Sorahum halepense SV - Setaria viridis DS - Diaitaria sanguinalis EC - Echinochloa crus-aalli CE - CvDerus esculentus CHEMICAL FORMULAE (IN DESCRIPTION)

Claims (10)

1. CLAIMS 1. A herbicidal dinitroaniline, arylurea, 2-phenylpyridazin-3-one, diphenylether, phenoxyphenoxypropionate, heteroaryloxyphenoxypropionate, arylanilide or substituted phenyl pyrrolidone derivative in which a phenyl or pyridyl group carries a pentafluorosulphanyl group.
2. 2. A herbicidal compounds of formula (I);

   where X is N or CR3; R1 and R3 are independently selected from hydrogen, halogen, or nitro; and R2 is a group YR4 where Y is oxygen or NR5 where R5 is hydrogen or alkyl, and R4 is substituted phenyl or substituted pyridyl.
3. 3. A compound according to claim 2 wherein the compound of formula (I) is a compound of formula (II);

   where R6 and R7 are independently hydrogen or halogen; R8 is halo or nitro; and R9 is a group OR10 or NR11R12 where R10 is hydrogen, or optionally substituted alkyl; R11 is hydrogen or alkyl and R12 is hydrogen, alkyl or alkylsulphonyl.
4. 4. A compound according to claim 2 wherein the compound of formula (I) is a compound of formula (III);

   where X is as defined in relation to formula (I): R17 is hydrogen or halogen; A is oxygen or NR19 where R19 is hydrogen or optionally substituted alkyl; and R18 is alkyl.
5. 5. A compound according to claim 2 wherein the compound of formula (I) is a compound of formula (IV)

   where R20 is selected from optionally substituted phenyl, or 21R22R23 where R21 R22 and R23 and selected from alkyl, alkenyl or alkynyl.
6. 6. A herbicial composition comprising a compound according to any one of the preceding claims in combination with an agriculturally acceptable carrier or diluent.
7. 7. A method of killing or controlling unwanted plants which comprises applying to the plants or to a locus thereof, a herbicidally effective amount of a compound according to any one of claims 1 to 5.
8. 8. A compound of formula (VII);

   where R26 and R27 are both halogen; or R26 is amino and R27 is halogen; or R26 is halogen and R27 is nitro.
9. 9. A herbicidal compound sustantially as described herein with reference to any one of the Examples.
10. 10. A herbicidal composition substantially as hereinbefore described.