GB2182327A - Imidazoles, their preparation and their use as fungicides - Google Patents

Abstract

The invention provides imidazoles of general formula <IMAGE> or an acid-addition salt thereof, wherein R represents an optionally substituted phenyl group, R<1> represents an optionally substituted alkyl, cycloalkyl, alkenyl, aryl or aralkyl group, R<2> represents a hydrogen atom, a cyano group or an optionally substituted alkyl group, each of R<3> and R<4> independently represents a hydrogen atom or an optionally substituted alkyl or alkenyl group, each moiety Z represents an oxygen atom, or each represents a sulphur atom, and p is 0 or 1, together with a process for their preparation, and their use as fungicides.

Description

SPECIFICATION Imidazoles,their preparation and their use as fungicides This invention relates two imidazoles, to a process for their preparation, and to their use as fungicides.

Various classes of imidazole fungicides are known, in which the imidazole ring is attached to the remainder of the molecule via a nitrogen atom. For example, US Patent No.3575999 (Janssen Pharmaceutica N.V.), discloses a class of compounds of the general formula

where Z represents, for example, a group-(CH2)2- or-(CH2)3- and Ar represents a phenyl group optionally substituted by certain moieties, ora 2-thienyl group.

There has now been discovered a novel class of 5-substituted imidazole derivatives having useful fungicidal activity.

According to the present invention there is provided an imidazole of general formula

or an acid-addition salt thereof, wherein R represents an optionally substituted phenyl group, R1 represents an optionally substituted alkyl, cycloalkyl, alkenyl, aryl or alkyl group, R2 represents a hydrogen atom, a cyano group or an optionally substituted alkyl group, each of R3 and R4 independently represents a hydrogen atom or an optionally substituted alkyl or alkenyl group, each moiety Z represents an oxygen atom, or each represents a sulphur atom, and p isO or 1.

Optional substituents includefor example halogen atoms and alkyl, alkoxy, haloalkyl, haloalkoxy, hydroxy, cyano, nitro, amino, carboxy, alkoxycarbonyl, phenyl, phenoxy, phenylthio, alkylthio and alkylsulphonyl groups, any alkyl moiety present preferably having up to 4 carbon atoms.

R is preferably a phenyl group optionally substituted by 1 to 5 halogen atoms. Advantageously R is a phenyl group substituted by 1 to 3 halogen, preferably chlorine, atoms.

R1 is preferably a C1 10 alkyl, conveniently a Ci.e alkyl, group; a C3-8 cycloalkyl group, aC2.6 alkenyl group, a phenyl group ora benzyl group.

R2 is preferably at1.6 alkyl group, or, more preferably, a hydrogen atom.

Preferably each of R3 and R4 independently represents a hydrogen atom or an optionally substituted C1-6 alkyl or phenyl group. In preferred embodiments R3 represents a hydrogen atom ora 01.4 alkyl group, and R4 represents a hydrogen atom or a C, 4 alkyl or phenyl group. In certain preferred embodiments R3 represents a hydrogen atom and R4 represents a hydrogen atom or a C1-4 alkyl group.

Whilst in some embodiments ofthis invention one or both of R3 and R4 may be a substituted alkyl group, unsubstituted alkyl groups, for example n-propyl groups are in general preferred.

The present invention also provides a process for the preparation of an imidazole of formula I which comprises reacting a compound ofthe general formula

with a compound of the general formula

wherein R, R1, R2, R3, R4, Z and pare as defined above.

The reaction between the compounds of general formulae II and Ill may conveniently be effected in an inert solvent, preferably a high boiling point solventwhich can form an azeotropic mixture, such astoluene, ben- zene orxylene, preferably in the presence of an acid, such as p-toluene sulphonic acid, and conveniently at the refluxtemperature. Water is preferably removed from the reaction mixture as the reaction proceeds. This is preferably effected by azeotropic distillation employing a Dean and Stark apparatus, any water collecting in atrap beneath the refluxcondenser.

The preparation of compounds ofthe general formula II, (as well as their utility as fungicides), is described in our co-pending UK patent application No. 8523255 (our ref K 1037 GBR), according to which they are prepared by reacting an imidazole ester ofthe general formula

where R1 is as defined above and R6 is an alkyl group with a compound offormula R7-CH2-R (V) wherein R is as defined above and R7 is-CN or-COOR8 where R8 is an alkyl group, in the presence of a base, followed, optionally when R7 is-CN, by treatment with a strong acid to produce a compound offormula II wherein R2 is hydrogen, optionally followed by reaction with an optionally substituted alkyl halide in the presence ofa base to produce a compound offormula II wherein R2 is an optionally substituted alkyl group.

Reaction of the compounds offormulae IV and V may conveniently be carried out in the presence of an inert solvent such as a C1.3 alkanol e.g. methanol or ethanol. The base may then conveniently be for example an alkali metal C1.3 alkoxide, which may readily be formed by dissolving the alkali metal, e.g. sodium, in the 3 alkanol. Reaction may very conveniently be effected at refluxtemperature.

When needed, thetreatmentwith the strong acid, e.g. sulphuric acid, may also conveniently be effected at refluxtemperature.

When needed, reaction of a compound of formula II wherein R2 is hydrogen with an optionallysubstituted alkyl halide is conveniently achieved in the presence of a base such as an alkali metal hydride oramide, preferably lithium diisopropylamide, advantageously using a dipolaraprotic solvent such astetrahydrofuran ordimethylsulphoxide. Reaction may conveniently be affected atambienttemperature.

Further in accordance with the invention there is provided a fungicidal composition which comprises a carrier and, as active ingredient, an imidazole offormula I ora saltthereofas defined above.

Acomposition according to the invention preferably contains from 0.5to 95% by weight of active in ingredient A carrier in a composition according to the invention is any material with which the active ingredient is formulated to facilitate application to the locus to be treated, which mayforexample be a plant, seed orsoil, orto facilitate storage, transport or handling. A carrier may be a solid ora liquid, including a material which is normally gaseous but which has been compressed to form a liquid, and any ofthe carriers normally used in formulating fungicidal compositions may be used.

Suitable solid carriers include natural silicas such as diatomaceous earths; magnesium silicates, for exampletalcs; magnesium aluminum silicates,forexampleattapulgites and vermiculites; aluminium silicates, for example kaolinites, montmorillonites and micas; calcium carbonate; calcium sulphate; synthetic hydrated silicon oxides and synthetic calcium or aluminium silicates; elements, for example carbon and sulphur; natural and synthetic resins, for example coumarone resins, polyvinyl chloride, and styrene poly mers and copolymers; solid polychlorophenols; bitumen; waxes, for example beeswax, paraffin wax, and chlorinated mineral waxes; and solid fertilisers, for example superphosphates.

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

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

Of particular interest in enhancing the duration ofthe protectant activity of the compounds ofthis invention is the use of a carrier which will provide a slow release of the fungicidal compounds into the environment of the plant which is to be protected. Such slow-release formulations could, for example, be inserted in the soil adjacent to the roots of a vine plant, or could include an adhesive component enabiing them to bye applied directly to the stem of a vine plant.

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

The compositions of the invention may for example be formulated as wettable powders, dusts, granules, solutions, emulsifiable concentrates, emulsions, suspension concentrates and aerosols. Wettable powders usually contain 25,50 or75%w of active ingredient and usually contain, in addition to solid inert carrier, 3-10%w of a dispersing agent and, where necessary, 0-10%w of stabiliser(s) and/or other additives such as penetrants or stickers. Dusts are usually formulated as a dust concentrate having a similar composition to thatof a wettable powder but without a dispersant, and may be diluted in the field with further solid carrierto give a composition usually containing -i O%w of active ingredient.Granules are usually prepared to have a size between 10 and 100 BS mesh (1.676-0.152mm), and may be manufactured by agglomeration or impregn- ation techniques.

Generally, granules will contain 1/2-25%w active ingredient and 0-1 0%w of additives such as stabilisers, slow release modifiers and binding agents. Emulsifiable concentrates usually contain, in addition to a solvent and, when necessary, co-solvent, 1-50%w/v active ingredient, 2-20%w/v emulsifiers and 0-20%w/v of other additives such as stabilisers, penetrants and corrosion inhibitors.Suspension concentrates are usually compounded so as to obtain a stable, non-sedimenting flowable product and usually contain 10-75%w of active ingredient, 0.5%-I 5%w of dispersing agents, 0.1 -1 -10%w of suspending agents such as protective colloids and thixotropic agents, 0-1 0%w of other additives such as defoamers, corrosion inhibitors, stabilisers, penetrants and stickers, and wateror an organic liquid in which the active ingredient is substantially insoluble; certain organic solids or inorganic salts may be present dissolved in the formulation to assist in preventing sedimentation or as antifreeze agentsforwater.

The compositions may also contain other ingredients, for example other compounds possessing pesticidal, especially insecticidal, acaricidal, herbicidal orfungicidal, properties.

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

The invention still further provides the use as a fungicide of a carboximidate of the general formula las defined above, and a method for combating fungus at a locus, which comprises treating the locus, which may for example be plants subject two or subjected to fungal attack, seeds of such plants or the medium in which such plants are growing or are to be grown, with such a derivative.

The present invention is of wide applicability in the protection of crop plants againstfungal attack. Typical crops which may be protected include vines, grain crops such as wheat and barley, rice, beans, tomatoes and apples. The duration of protection is normally dependent on the individual compound selected, and also a variety of external factors, such as climate, whose impact is normally mitigated by the use of a suitable formulation.

The invention will be further understood from the following examples.

EXAMPLE 1 Preparation of 5-[2(4-chlorophenyl) 1,1-ethylenedioxyethyl]-1-methylimidazole (a) Preparation of5-[2(4-chlorophenyl)-2-cyano- 1-oxoethyl]- 1-methylamidazole Sodium (2.25g) was dissolved in methanol (150ml). The resulting solution was heated under reflux and a solution of 1 -methylimidazole-5-methyl carboxylate (9.0g) and p-chlorophenylacetonitrile (1 0.8g) in methanol (50m I) was added dropwise thereto over 1 hour. The resulting mixture was heated under reflux fora further4 hours and allowed to cool. The methanol was evaporated off and the residue was diluted with water and washed with diethylether.Glacial acetic acid (7.6ml) was added to the aqueous phase and the resulting milky solution was extracted with chloroform (3 x 100ml). The combined chloroform extracts were washed with brine and dried (Mg SO4), and solvent was evaporated offtoyieldthetitle compound asa solid (5.8g, 35%) mp 58-60 C.

Analysis requires: 60.2C; 3.9H; 16.2N C13H10C1N3O found: 61.OC; 4.5H; 15.2N (b) Preparation of5-12-(4-chlorophenyl)- 1-oxoethyl7- 1-methylimidazole 5-[2-(4-Chlorophenyl)-2-cyano-1-oxoethyl]-1-methylimidazole (0.7g)was added portionwiseto sulphuric acid (6ml, 13.5M) and heated under refluxfor 5 hours and allowed to cool. The reaction mixture was poured into water (30ml) and the pH was adjusted to pH9 by addition of concentrated aqueous ammonia.

On cooling and scratching, the title compound precipitated out as a white solid (0.5g,71%) mp 108-1 10'C.

Analysis requires: 61.1C; 4.6H; 11.7N C12H11C1N2O found: 61.5C; 4.7H; 11.9N (c) Preparation of5-f2(4-chlorophenyl) 1, 1-ethylenedioxyethyl]-1-methylimidazole 5-[2(4-chlorophenyl)-1 -axoethyl]-1 -methylimidazole (1 g), ethane-1,2-diol (2.5g) and p-toluenesulphonic acid (1 .8g) were refluxed in xylene (50 ml) isa Dean-Starkapparatus,for 12 hours.On cooling,the reaction mixture was washed with sodium bicarbonate solution and water, and dried (Mg8O4). The solvent was evaporated offand the residual oil chromatographed on silica using 4% methanol/methylene chloride (v/v) to afford the title compounds as an oil (0.5g,42%) Analysis requires: 60.4C; 5.4H; 10.1N C4H,5CIN202 found: 60.OC; 5.7H; 9.9N EXAMPLE2 Preparation of 5-[2(4-chlorophenyl)1,1-ethylenedithioethyl)-1-isopropylimidazole (a) Preparation of5-J2(4-chlorophenyl)-2-cyano- 1-oxoethyl7- 1-isopropylimidazole Sodium (2.76g) was dissolved in methanol (50m1).The resulting solution was heated under reflux and a solution of 1 -isopropylimidazole-5-methyl carboxylate (9.1 g) and p-chlorophenylacetonitrile (10.6g) in methanol (50ml) was added dropwise thereto over 1 hour. The resulting mixture was heated under reflux for a further4 hours and allowed to cool. The methanol was evaporated off and the residue was diluted with water and washed with diethylether.Glacial acetic acid (6.5ml) was added to the aqueous phase and the resulting milky solution was extracted with chloroform (3 x 100ml). The combined chloroform extracts were washed with brine and dried (MgSO4),and solvent was evaporated offto yield the title compound, in equilibrium with its enol tautomer, as a waxy solid which was used as described belowwithoutfurther purification.

(b) Preparation of5-f2-(4-chlorophenyl)- l-oxoethyU- 1-isopropylimidazole 5-[2-(4-Chlorophenyl)-2-cyano-1-oxoethyl]-1-isopropylimidazole(14g) was added portionwise to sulphuric acid (1 13m1, 27M) and heated underrefluxfor5 hours and allowed to cool. The reaction mixture was poured into water and the pH was adjusted to pH9 by addition of concentrated aqueous ammonia. The aqueous layer was extracted with chloroform (3 x 100ml) and the combined organic extracts washed with water and dried (MgSO4). The solvent was evaporated off and the residual oil chromatographed on aluminia with ether as eluantto afford thetitle compound (8.1 g, 63%) as a white solid, m.p. 57-8'.

Analysis requires: 64.OC; 5.7H; 10.7N C14H15ClN2o found: 63.3C; 5.7H; 10.6N (c) Preparation or of5-f2(4-chlorophenyl) 1, 1,1-ethylenedithioethyl7- 1-isopropylimidazole 5-[2(4-Chlorophenyl)-1 -oxoethyll-1 -isopropylimidazole (1 .5g) was refluxed with p-toluenesulphonic acid (1 .2g) and ethane-1,2-dithiol (2.68g) in xylene (40m1) for36 hours using a Dean-Starkapparatus. On cooling, the reaction mixture was made basic with sodium bicarbonate solution and the organic layer separated.The aqueous phase was extracted with xylene (2 x 20m1) and the combined organic extracts washed with water and dried (MgSO4).The solvent was evaporated off under reduced pressure and the residual oil chromato graphed on silica using 5% methanol/diethylether (v/v) as eluant to afford the title compound (1 .27g, 66%) as a solid, mp 172-3'C.

Analysis requires: 56.7C; 5.6H; 8.3N C16H1sClN2S2 found: 56.7C; 5.6H; 8.3N EXAMPLE3 Preparation of5-f2(chlorophenyl) 1, 1-ethylenedioxypropyl7- 1-methylimidazole (a) Preparation of6-[2(4-chlorophenyl)- 1-oxopropyl7- 1-methylimidazole To a stirred solution of lithium diisopropylamine [3.6ml of 1 .4M solution of butyl lithium in hexane and diisopropylamine (0.5g)j at O"C under nitrogen in dry tetrahydrofuran was added 5-[2(4-chlorophenyl)-1- oxoethyl]-l -methylimidazole (1.0g) in dry tetrahydrofuran and stirring was continued for 1 hour. Methyl iodide (1 g) in tetrahydrofuran (1 OmI) was added dropwise and the reaction mixture was stirred at ambient temperature (20"C) for 12 hours. The reaction mixture was then diluted with water and extracted with methylene chloride. The combined organic extracts were washed with water and dried (MgSO4), and the solvent components were evaporated off under reduced pressure. A residual oil was obtained which was chromatographed on silican using 5%v/v methanol/diethylether as eluantto afford the title product as an oil (1 0.9g, 79%).

Analysis requires: 62.9C; 5.2H; 11.3N C13H13ClN2o found: 61.7C; 5.3H; 11.6N (b) Preparation of 5-[2(4-chlorophenyl)1,1-ethylenedioxypropyl]-1-methylimidazole 5-[2(4-Chlorophenyl)-1 -oxopropyl]-l -methylimidazole (0.5g) was refluxed with ethane-1 ,2-diol (0.5g) and p-toluenesulphonicacid (0.4g) in xylene (50ml) using a Dean-Starkapparatusfor48 hours. On cooling,the reaction mixture was made basic with a saturated sodium bicarbonate solution and the organic layer separated.The aqueous phase was extracted with xylene (2 x 25 ml) and the combined organic extracts washed with water and dried (MgS04). The solvent was evaporated off under reduced pressure and the residual oil chromatographed in silica using 5% methanol/dichloromethane (v/v) as eluantto afford the title compound (0.3g, 44%) as an oil: Analysis requires: 61.6C; 5.3H; 9.6N C15H17CIN202 found: 61.1C; 5.4H; 10.6N EXAMPLES4 TO8 By processes analogous to those of Examples 1 to 3 there were prepared a number of other compounds of the invention, as detailed in Table I following:

TABLE I Example R4 Z X P mp('C) Analysis Found (Theory) 4 n-propyl 0 H O oil 62.8C; 6.8H; 8.5N (63.7C; 6.6H; 8.7N) 5 n-propyl 0 Cl O oil 56.8C; 5.7H; 8.3N (57.5C; 5.6H; 7.9N) 6 H S H 0 120-122 52.7C; 4.9H; 7.9N (54.2C; 4.8H; 9.ON) 7 H O H 1 oil 5.8H; 9.3N; (5.8H; 9.6N;) 8 H S H 1 oil 54.1C; 5.6H; 8.5N (55.5C; 5.2H; 8.6N) EXAMPLE9 The fungicidal activity of compounds of the invention was investigated by means ofthe following tests.

(a) Direct protectantactivity against vine downy mildew {Plasmopara viticola; PvpJ The test is a direct protectant one, using a foliar spray. The lower surfaces of leavesof whole vine plants (cv Cabernet Sauvignon) are sprayed with a solution of active material in 1 v/v water/acetone containing 0.04%w "Triton X-155" (trade mark) (octylphenol polyoxyethylene surfactant), at a dosage of 1 kilogram of active material per hectare using a track sprayer which delivers 620 I/ha, and after a subsequent 24 hours under normal glasshouse conditions the lower surfaces of the leaves are inoculated by spraying with an aqueous solution containing 104zoosporangia/ml.The inoculated plants are keptfor 24 hoursin a high humidity compartment 5 days under normal glasshouse conditions and then returned for a further24 hours to high humidity. Assessment is based on the percentage of leaf area covered by sporulation compared with that on control leaves.

(b) Antisporulantactivity against vine downy mildew (Plasmopara viticola; Pva) The test is a direct antisporulant one using a foliar spray. The lower surfaces of leaves of whole vine plants (cv Cabernet Sauvignon) are inoculated by spraying with an aqueous suspension containing 104zoospor- angia/ml 2 days priorto treatment with thetestcompound. The inoculated plants are keptfor24 hours in a high humidity compartment, and then 24 hours at glasshouse ambient temperature and humidity. When the plants are dry, infected leaves are sprayed on their lower surfaces as described under (a) above.Afterspraying,the plants are returned to normal glasshouse conditionsfor96 hours and arethen transferred to the high humidity compartmentfor24 hours to inducesporulation, priorto assessment. Assessment is visual and is based on the percentage ofthe leaf area covered by sporulation compared with that on control leaves.

(c) Direct protectant activity against vine grey mould {Botrytis cinerea; BcpJ The test is a direct protectant one using a foliar spray and is effected as described under (a), with the difference that the leaves are inoculated by spraying with an aqueous solution containing 1 conidia/ml.

(d) Activity against barleypowdery mildew (Erysiphe graminis f.sp. hordei; EgJ The test is a direct antisporulant one, using a foliar spray. Leaves of barley seedlings, cultivar Golden Promise, are inoculated by dusting with mildewconidia one day priorto treatment with the test compound.

The inoculated plants are kept overnight at glasshouse ambienttemperature and humidity priortotreatment.

The plants are sprayed at a dosage of 1 kg. of active material per hectare using a track sprayer as described under (a).Afterdrying, plants are returned to a compartment at ambient temperature and humidity for upto7 days, followed by assessment. Assessment is based on the percentage of leaf area covered by sporulation compared with that on leaves of control plants.

(e) Activity against apple powdery mildew (Podosphaera leucotricha; PIJ The test is a directanti-sporulantone using a foliarspray. The uppersurfaces of leaves of whole apply seedlings are inoculated by spraying with an aqueous suspension containing 105 conidia/ml 2 days priorto treatmentwith thetestcompound. The inoculated plants are immediately dried and keptatglasshouse ambienttemperatures and humidity prior to treatment The plants are sprayed at a dosage of 1 kilogram of active material per hectare using a track sprayer as described under (a). After drying the plants are returned to a compartment at ambient temperature and humidity for up to 9 days, followed by assessment.Assessment is based on the percentage ofthe leaf area covered by sporulation compared with that on leaves of control plants.

(f) Activity against rice leaf blast rPyricularia oryzae Po) The test is a direct eradicant one using a foliarspray. The leaves of rice seedlings (about30 seedlings per pot) are sprayed with an aqueous suspension containing 105 spores/ml 20-24 hours priorto treatmentwith the test compound. The inoculated plants are kept overnight in high humidity and then allowed to dry before spraying at a dosage of 1 kg of active material per hectare using a track sprayer as described under (a). After treatmentthe plants are kept in a rice compartment at25-30"C and high humidity.Assessments are made4-5 days aftertreatment and are based on the density of necrotic lesions and the degree of withering when compared with control plants.

(g) Activity against tomato early blight (Alternaria solaniAsJ The test is a direct protectant one using a foliar spray. The upper surfaces of leaves of young tomato plants are sprayed with a solution of active material as described in (a) above. After 24hrs under normal glasshouse conditions, the upper surgaces of the leaves are inoculated by spraying with an aqueous suspension contain- ing 104spores/ml. The inoculated plants are keptfor72 hours in a high humidity compartment and arethen removed to lower humidity (50-70% relative humidity). Assessment is made 8 days after inoculation.

(h) Activity against wheat eyespot (Pseudocereosporella herpotrichoides PhJ The test is an in vitro one. Samples are prepared wherein 0.7ml solution containing 2mg active material dissolved in acetone is evenly dispersed in 20ml molten half-strength potato dextrose agar(formed by dissolving 2g potato extract, lOg dextrose and 7.5g agar in 1 litre of water and sterilising for 15 minutes at121'C) and the resulting 20ml portions are allowed to set in 9cm petri dishes. The concentration of active material in the resulting samples is 100ppm.Upon settling, two plugs of 5mm diametertaken from the advancing edge of a stock plate of 3 to 4 week old culture of P. herpotrichoides on full strength potato dextrose agar, incubated at 20-22"C in darkness, are placed, equally spaced on the surface of each sample, mycelial side uppermost.

The samples are incubated for 11 days at 20-22"C in darkness before assessment. Diametric growth is measured with the width ofthe plug subtracted and results compared with growth on a sample wherein 0.7m 1 acetone containing no active material is dispersed in 20ml half-strength potato agar.

(i) Activity against seedling wheat blight (Fusarium culmorium; Fc) The test is an anti-sporulant one using a soil drench. Surface sterilised wheat seeds (varWaggoner) are inoculated by soaking in an aqueous suspension containing 7 xl 105 spores/ml (60mg seed per80ml suspen- sion) at22'Cfor6 hours. The seeds are then sown in pots (5 per pot) in sand ata depth of 1cm. 1 dayafter inoculation and planting the active material is applied at a rate of 1 Okg/ha by pouring on a soil drench (concentration 0.36gel active material in 12%v/v acetone/water) evenly over the sand. The pots are then transferred to glasshouse, kept at 25"C and watered sparingly. 21 days after inoculation the resulting seedlings are removed from the pots and their roots are gently washed. Visual assessment is made based on lesion development on stem base and upper roots in comparison with control seedlings.

The extent of disease control in all the above tests is expressed as a rating compared with a diluent control according to the criteria: 1 = about 50-80% disease control 2 = greaterthan 80% disease control Results oftheabovetests are given in Table II following: TABLE II Compound Fungicidal Activity Example Pvp Pva Bcp Eg Pl Po As Ph Fc 1 1 2 2 1 2 1 1 3 2 4 2 2 2 1 5 1 1 2 1 6 1 2 1 7 1 2 2 1 8 2 2

Claims (18)

1. An imidazoleofgeneralformula

oran acid-addition saltthereof, wherein R represents an optionally substituted phenyl group, R1 represents an optionally substituted alkyl, cycloalkyl, alkenyl, acryl or art alkyl group, R2 represents a hydrogen atom, a cyano group or an optionally substituted alkyl group, each of R3 and R4 independently represents a hydrogen atom or an optionally substituted alkyl or alkenyl group, each moiety Z represents an oxygen atom, or each represents a sulphur atom, and p isO or 1.

2. An imidazole according to Claim 1 wherein R represents a phenyl group optionally substituted by one to three halogen atoms.

3. An imidazole according to Claim 2, wherein the halogen atoms are chlorine atoms.

4. An imidazole according to any of Claims 1 to 3 wherein R1 is a C,10 alkyl group, a C3.8cycloalkyl group,a C2.6alkenyl group,a phenyl groupora benzyl group.

5. An imidazolegroup according to Claim 4wherein R1 represents a C1.6 alkyl group.

6. An imidazole according to any of Claims 1 to Swherein R2 represents a hydrogen atom ora C1.6alkyl group.

7. An imidazole according to Claim 6wherein R2 represents a hydrogen atom.

8. Aimidazole according to any of Claims 1 to 7,wherein R3 represents a hydrogen atom oran optionally substituted alkyl group and R4 represents a hydrogen atom or an optionally substituted alkyl or phenyl group.

9. A imidazole according to Claim 8, wherein R3 represents a hydrogen atom and R4 represents a hydrogen atom ora C1.4alkyl group.

10. An imidazole according to Claim 1 substantially as hereinbefore described in anyone of Examples 1 to 8.

11. A processforthe preparation of an imidazole offormula las claimed in any of Claims 1 to 10which comprises reacting a compound ofthe general formula

with a compound ofthe general formula

where R, R1, R2, R3, R4, Z and pare as defined in Claim 1.

12. A process according to Claim 11 substantially as hereinbefore described with reference to any of Examples 1 to 8.

13. An imidazole offormula I whenever prepared bya process according to Claim 11 or 12.

14. Afungicidal composition which comprises a carrier and, as active ingredient, an imidazole according to any of Claims 1 to 10 or Claim 13.

15. A composition according to Claim 14, which comprises at leasttwo carriers, at least one of which is a surface-active agent.

16. A method of combating fungus at a locus, which comprises treating the locus with an imidazole ofthe general formula las defined in anyone of Claims 1 to 10OrClaim 13.

17. A method as claimed in Claim 16, in which the locus comprises plants subject or subjected to fungal attack, seeds of such plants orthe medium in which the plants are growing or are to be grown.

18. The use as a fungicide of an imidazole ofthe general formula las defined in anyone of Claims 1 toll or Claim 13.