WO1994001411A1

WO1994001411A1 - Benzimidazole derivatives as microbicides

Info

Publication number: WO1994001411A1
Application number: PCT/EP1993/001660
Authority: WO
Inventors: Marius Sutter; Adolf Hubele
Original assignee: Ciba-Geigy Ag
Priority date: 1992-07-10
Filing date: 1993-06-29
Publication date: 1994-01-20
Also published as: CZ4895A3; IL106268A0; CN1083057A; CA2137686A1; SK2795A3; PL307123A1; MX9304131A; BR9306708A; JPH07508738A; AU4560593A; EP0650479A1

Abstract

Compounds of formula (I) in which R1 is CN or -CS(=O)nNH2, R2 is C1-C4alkyl, C3-C6cycloalkyl or -N(R')2, in which R' radicals are different or identical C1-C3alkyl radicals and n is 0 or 1, are suitable for controlling and preventing infestation of plants by microorganisms. They can be used in the form of commercially available formulations.

Description

BENZDCTOAZOLE DERIVATIVES AS MICROBICTDES

The present invention relates to novel benzimidazolesulfonic acid derivatives of the formula I below. It furthermore relates to the preparation of these substances and to agrochemicals comprising at least one of these compounds as active ingredient. The invention also relates to the preparation of the abovementioned compositions and to the use of the active ingredients or of the compositions for controlling or preventing infestation of plants by phytopathogenic microorganisms, preferably fungi.

The compounds according to the invention are those of the general formula I

in which the R₂SO₂ group is in the 1- or 3-position and causes the formation of pure or mixed positional isomers relative to the CF₃ substituents and in which the substituents are as defined below:

R₁ is CN or -CS(=O)_nNH₂,

R is C_rC₄al yl, C₃-C₆cycloalkyl or -N(R')₂, in which R' substituents are different or identical C C₃alkyl radicals, and n is 0 or 1.

The term al yl itself or as a component of another substituent is to be understood as meaning the following straight-chain or branched groups, depending on the number of the carbon atoms indicated: methyl, ethyl, propyl, butyl and their isomers isopropyl, isobutyl, sec-butyl and tert-butyl.

At room temperature, the compounds of the formula I are stable solids which are distinguished by valuable microbicidal properties. Their particularly advantageous activity is based mainly on the specific substitution pattern in the fused benzene ring. They can be used in a preventive and curative fashion in the field of agriculture or related fields for controlling phytopathogenic microorganisms. Used at low concentrations, the active ingredients of the formula I according to the invention are distinguished not only by an outstanding microbicidal, in particular fungicidal, activity, but also by the fact that they are particularly well tolerated by plants.

Important compounds within the scope of the formula I are those in which R₂ is C₁-C₂al yl, cyclopropyl or N(R')₂, R' is methyl or ethyl and n is 0 or 1.

One of the particularly important substance groups within this scope is the group in which R₂ is methyl or N(R')₂, R¹ is methyl and n is 0 or 1. Particularly preferred compounds from amongst this group are those in which R₂ is dimethylamino and n is 0 or 1.

A group of preferred compounds of the formula I embraces the compounds in which the R₂SO₂ group is in the 1- or 3-position and causes the formation of pure or mixed positional isomers relative to the CF₃ substituents and in which Rj is -CSNH₂ ^an-ⁱ ^₂ ^ιs C_rC₄alkyl, C₃-C₆cycloalkyl or -N(R')₂, in which R' substituents are different or identical Cj-Csalkyl radicals. Particularly preferred from amongst these substituents are those in which R₂ is methyl or -N(CH₃)₂.

Preferred individual compounds are l(3)-dimethylaminosulfonyl-2-carbothioamido-4,6-bistrifluoromethylbenzimidazole, l(3)-dimethylaminosulfonyl-2-carbothioamido-4,6-bistrifluoromethylbenzimidazole- S-oxide and 1 (3)-dimethylaminosulfonyl-2-cyano-4,6-bistrifluoromethylbenzimidazole.

If n is 0 (formula lb), the compounds of the formula I where Rj is -CS(=O)_nNH₂ can be prepared by reacting H₂S with a compound of the formula la,

in which R₂ is as defined in formula I. The reaction which leads to the thioamide is carried out in the presence of inorganic or organic bases. Preferred substances are organic bases, for example sec-amines such as dimethylamine [K. Kindler, Ann. 431, 187 (1923)], diethylamine or tert-amines such as triethanolamine or triethylamine [J.F. Olin and T.B. Johnson, R. 50, 72 (1931); D.W. cCorquodale and T.B. Johnson, R. 51, 483 (1932)]. Equimolar amounts or a slight excess of bases are preferably used. The following act as solvents: polar solvents, for example alcohols (methanol, ethanol, isopropanol etc.), but preferably acid amides, for example dimethylformamide, or else ethers such as diethyl ether, tetrahydrofuran, dioxane, etc.

A further possibility for adding on H₂S is the use of heterocyclic bases as the solvent, for example pyridine, in the presence of a tert-amine, such as trialkylamine (for example triethylamine [A.E.S. FairfuU, J.L. Lowe and D.A. Peak, Soc. 1952, 742]. H₂S is passed in at -20°C to +80°C, in particular -10°C to +40°C. H₂S can be passed in continuously, or the process can be carried out under pressure.

The S-oxide compounds (n = 1, formula Ic) are prepared from the thioamides (n = 0, formula lb) by oxidation with organic peroxides or hydrogen peroxide (preferably in the form of an aqueous 30% solution). Approximately equimolar amounts of oxidant are preferably used. The following act as solvents: polar solvents, for example alcohols (methanol, isopropanol), acid amides (N-methylpyrrolidone), ketones (acetone), pyridine, or aliphatic carboxylic acids. The preferred substance is acetic acid (glacial acetic acid), with or without an addition of a base, for example sodium acetate. The reaction temperature is between -20°C and +60°C, preferably between 0°C and +30°C.

(lb, n = 0) (Ic, n = l)

The invention also relates to 2-cyano-4,6-bistrifluoromethylbenzimidazole of the formula IH and to the preparation thereof. The substance is prepared from l,2-diamino-3,5-bistrifluoromethylbenzene or salts thereof by methods known per se:

■ROH

(Y = anion of an acid; Hal = halogen, preferably Cl; R = C_rC₃alkyl)

HY is an inorganic or organic acid, preferably a hydrohalic acid or sulfuric acid. The o-phenylenediamine derivative can, however, also be used in the form of the free base when reaction step a) is carried out in glacial acetic acid. Preferred solvents other than glacial acetic acid are ethers such as diethyl ether, dioxane, 1,2-dimethoxyethane; esters such ethyl acetate, or alcohols such as methanol and ethanol.

The trihaloimidate (for example methyl trichloromethylimidate or chlorodifluoromethylimidate) is advantageously added to the dissolved or suspended o-phenylenediamine derivative at -20°C to +100°C. In reaction step b), the 2-trihalomethylbenzimidazole derivative obtained is advantageously added to a concentrated aqueous ammonia solution (USP. 3 576 818).

2-Cyano-4,6-bistrifluoromethylbenzimidazole, of the formula III, can also be prepared using the corresponding 2-nitro-4,6-bistrifluoromethylaniline in place of the o-phenylenediamine derivative by reacting it with formaldehyde and KCN in glacial acetic acid with addition of zinc chloride (or a different Lewis acid) as catalyst, giving compounds of the formula

[K. Dimroth et al., Ber. 98, 3902 (1965)], and these are cyclised with K₂CO₃ to give l-hydroxy-2-cyanobenzimidazole derivatives [B. Serafinowa et al. Rocz. Chem. 5J_, 1783 (1977)], which can be reacted with PC1₃ to give compounds of the formula III. This process variant is also an object of the invention.

The products of the formula la can be prepared by reacting the compound of the formula HI or one of the alkali metal salts thereof, preferably a sodium, potassium or lithium salt, with a compound of the formula IV

Q-SO₂-R₂ (IV)

in which R₂ is as defined in formula I and Q is a halogen atom, preferably chlorine or bromine, or the radical O-SO₂-R₂- in an inert solvent in the presence or absence of a base at temperatures from -30° to +180°C, preferably -10° to +80°C.

Suitable solvents are, in particular, polar reaction media such as ketones (for example acetone, methyl ethyl ketone or tert-butyl methyl ketone), ethers (such as diethyl ether, dioxane, tetrahydrofuran or 1,2-dimethoxyethane), amides (for example dimethylformamide) or dimethylsulf oxide or, if appropriate, mixtures of such solvents. The benzimidazole derivative IH is advantageously reacted in the presence of a strong base (such as KOH or NaOH).

Surprisingly, it has been found that compounds which have the specific structural pattern of the formula I have a biocidal spectrum which is highly favourable for practical requirements for controlling phytopathogenic microorganisms, in particular fungi. They have very advantageous curative and preventative properties and are used for the protection of a large number of crop plants. The active ingredients of the formula I allow disease on plants or parts of plants (fruit, flowers, foliage, stalks, tubers or roots) of a range of useful crops to be contained or prevented, and even parts of plants which are formed at a later point in time remain free from, for example, phytopathogenic fungi.

The novel active ingredients of the formula I prove to be effective against specific genera from the fungal classes Fungi imperfecti (for example Cercospora), Basidiomycetes (for example Puccinia) and Ascomycetes (for example Erysiphe and Venturia) but, in particular, against Oomycetes (for example Plasmopara, Peronospora, Pythium, Bremia and Phytophthora). They are therefore a valuable complement of the compositions used in crop protection for controlling phytopathogenic fungi. Advantageously, they have curative as well as preventive properties when used in practice, and they can be used for the protection of a large number of crop plants. Using these active ingredients, the pests found on plants or parts of plants (fruit, flowers, foliage, stalks, tubers or roots) of a wide range of useful crops can be contained or destroyed, and even parts of plants which are formed at a later point in time remain free from, for example, phytopathogenic fungi. The compounds of the formula I can furthermore be used as seed-dressing agents for the treatment of seed (fruit, tubers or grains) and plant cuttings for protecting them against fungal infection and against soil-borne phytopathogenic fungi.

The invention also relates to the compositions which comprise compounds of the formula I as active ingredient and to their use in the field of agriculture or in related fields.

Moreover, the present invention also embraces the preparation of these compositions, which comprises intimately mixing the active ingredient with one or more substances or substance groups described herein. The invention also embraces a method for treating plants, which is distinguished by applying the novel compounds of the formula I, or the novel compositions.

Target crops for the use disclosed herein for the purposes of crop protection are, within the scope of the invention, for example the following plant species: cereals (wheat, barley, rye, triticale, oats, rice, maize, sorghum and related species); beet (sugar beet and fodder beet); palm fruit, stone fruit and soft fruit (apples, pears, plums, peaches, almonds, cherries, strawberries, raspberries and blackberries); leguminous plants (beans, lentils, peas, soya beans); oil crops (oilseed rape, mustard, poppy, olives, sunflowers, coconut, castor-oil plant, cacao, groundnut); cucurbits (pumpkin, cucumbers, melons); fibre plants (cotton, flax, hemp, jute); citrus fruit (oranges, lemons, grapefruit, mandarins); vegetable crops (spinach, lettuce, asparagus, cabbages, carrots, onions, tomatoes, potatoes, bell peppers); Lauraceae (avocado, cinnamon, camphor) or other crop plants such as tobacco, nuts, coffee, sugar cane, tea, pepper and other spice plants, vines, hops, Musaceae and latex plants as well as ornamentals.

Active ingredients of the formula I are customarily used in the form of compositions and can be applied to the area or plant to be treated either simultaneously with other active ingredients or in succession. These other active ingredients can be fertilisers, trace element mediators or other preparations which affect the growth of the plants. Selective herbicides as well as insecticides, fungicides, bactericides, nematicides, molluscicides or mixtures of several of these preparations, together with or without other carriers conventionally used in the art of formulation, surfactants or other application-enhancing additives can also be used.

Suitable carriers and additives can be solid or liquid and are those substances which are expedient in the art of formulation, for example natural or regenerated mineral substances, solvents, dispersants, wetting agents, tackifiers, thickeners, binders or fertilisers.

A preferred process for applying an active ingredient of the formula I, or an agrochemical comprising at least one of these active ingredients, is application to the foliage (foliar application). Frequency and rate of application depend on the risk of infestation with the pathogen in question. The compounds of the formula I can also be applied to seeds (coating), either by soaking the grains in a liquid preparation of the active ingredient or by coating them with a solid preparation.

The compounds of the formula I are employed as pure active ingredients or, preferably, together with the auxiliaries conventionally used in the art of formulation. To this end, they are processed advantageously in a known manner to give, for example, emulsion concentrates, spreadable pastes, directly sprayable or dilutable solutions, dilute emulsions, wettable powders, soluble powders, dusts, granules or encapsulations, for example in polymeric substances. The methods of application such as spraying, atomising, dusting, scattering, brushing on or pouring, as well as the nature of the formulation, are selected to suit the intended aims and the prevailing circumstances.

Favourable rates of application are, as a rule, 5 g to 2 kg of active ingredient (A.I.) per hectare (ha), preferably 10 g to 1 kg of A.L/ha, in particular 20 g to 600 g of A.IJha.

The formulations, i.e. the compositions, preparations or combinations comprising the active ingredient of the foraiula I with or without or a solid or liquid additive, are prepared in a known manner, for example by intimately mixing and/or grinding the active ingredient with extenders such as solvents, solid carriers and, if appropriate, surface-active compounds (surfactants).

The following are possible as solvents: aromatic hydrocarbons, preferably the fractions C₈ to Cj₂, such as xylene mixtures or substituted naphthalenes, phthalic esters, such as dibutyl phthalate or dioctyl phthalate, aliphatic hydrocarbons, such as cyclohexane or paraffins, alcohols and glycols as well as their ethers and esters, such as ethanol, ethylene glycol, ethylene glycol monomethyl ether and ethylene glycol monoethyl ether, ketones such as cyclohexanone, strongly polar solvents such as N-methyl-2-pyrrolidone, dimethyl sulfoxide or dimethylformamide, and epoxidised or unepoxidised vegetable oils such as epoxidised coconut oil or soya oil, as well as water.

Solid carriers which are used, as a rule, for example for dusts and dispersible powders, are ground natural minerals such as calcite, talc, kaolin, montmorillonite or attapulgite. To improve the physical properties, it is also possible to add highly-disperse silica or highly-disperse absorptive polymers. Possible particulate, adsorptive carriers for granules are porous types, such as pummice, brick grit, sepiolite or bentonite, and possible non-sorptive carrier materials are, for example, calcite or sand. Moroever, a large number of pregranulated materials of inorganic or organic nature can be used, such as dolomite or comminuted plant residues.

Suitable surface-active compounds are non-ionic, cationic and/or anionic surfactants which have good emulsifying, dispersing and wetting properties, depending on the nature of the active ingredient of the formula I to be formulated. Surfactants are also to be understood as meaning mixtures of surfactants.

Possible anionic surfactants can be so-called water-soluble soaps as well as water-soluble synthetic surface-active compounds.

Examples of non-ionic surfactants which may be mentioned are nonylphenol polyethoxyethanols, castor oil polyglycol ethers, polypropylene oxide/polyethylene oxide adducts, tributylphenoxypolyethylene ethanol, polyethylene glycol and octylphenoxypolyethoxyethanol.

Fatty acid esters of polyoxyethylene sorbitan, such as polyoxyethylene sorbitan trioleate, are also suitable.

The cationic surfactants are, in particular, quaternary ammonium salts which comprise at least an alkyl radical having 8 to 22 carbon atoms as N-substituents and lower, halogenated or free alkyl, benzyl or lower hydroxyalkyl radicals as further substituents. Other surfactants conventionally used in the art of formulation are known to those skilled in the art or can be found in the relevant specialist literature.

As a rule, the agrochemical preparations comprise 0.1 to 99 per cent by weight, in particular 0.1 to 95 per cent by weight, of active ingredient of the formula 1, 99.9 to 1 per cent by weight, in particular 99.8 to 5 per cent by weight, of a solid or liquid additive, and 0 to 25 per cent by weight, in particular 0.1 to 25 per cent by weight, of a surfactant.

While concentrated compositions are more preferred as commercially available goods, the end consumer uses, as a rule, dilute compositions.

The compositions can also comprise further additives such as stabilisers, antifoams, viscosity regulators, binders or tackifiers, as well as fertilisers or other active ingredients to achieve specific effects.

The examples which follow illustrate the above-described invention without restricting the scope of the latter in any way. Temperatures are given in degree centigrade.

Preparation example

1. Prepration of

[Compound 0.3]

l(3)-Dimethylsulfamoyl-2-cvano-4,6-bistrifluoromethylbenzimidazole 10.0 g (36 mmol) of 2-cyano-4,6-bistrifluoromethylbenzimidazole are dissolved in 100 ml of acetone, 2.6 g of potassium hydroxide (85 %, pulverulent) are added, and the mixture is stirred for 1 hour at 25°C. The solution will now have turned orange. 5.8 ml of N,N-dimethylsulfamoyl chloride are slowly added dropwise. The process is slightly exothermal. The mixture is stirred for 22 hours at room temperature and then filtered, the filtrate is concentrated to dryness on a rotary evaporator, and the residue is dissolved in methylene chloride and silica gel is added. After the mixture has been stirred for 2 hours, it is filtered, the filtrate is concentrated and digested with ether and the product is finally filtered off and dried. Yield 4.6 g. Melting point 166-168°C.

2. Preparation of

[Compound 1.3]

l(3)-Dimethylsulfamoyl-2-carbothioamido-4,6-bistrifluoromethylbenzimidazole 140 g (0.36 mol) of l(3)-dimethylsulfamoyl-2-cyano-4,6-bistrifluoromethylbenzimidazole are dissolved in 1500 ml of dioxane at room temperature with stirring, and 490 ml of tetrahydrofuran and then 53 ml of triethylamine are added. Into this mixture, hydrogen sulfide is passed slowly over 2 hours at room temperature. When the reaction has ended, the mixture is concentrated on a rotary evaporator to approximately half its volume, and this is subsequently poured into ice-water with stirring, and the precipitate which has separated out is filtered off with suction and washed with water. After drying the crystals melt at 212-213°C with decomposition.

3. Preparation of

[Compound 2.2]

l(3)-Dimethylsulfamoyl-2-carbothioamido-4,6-bistrifluoromethylbenzimidazole S-oxide 2.0 g (5 mmol) of l(3)-dimethylsulfamoyl-2-carbothioamido-4,6-bistrifluoromethylbenzimidazole are suspended in 30 ml of glacial acetic acid. 1.87 g of anhydrous sodium acetate are added. A thick, yellow suspension is formed. 0.5 ml of hydrogen peroxide (30 % in water) are added slowly with vigorous stirring, and the mixture is stirred for 3 hours at 20°C. The batch is subsequently poured into ice-water and filtered, and the filtrate is washed with water until neutral and dried at 50°C in a drying cupboard. Yield 1.85 g (88.9 % of theory). Melting point 162-164°C.

Preparation of the intermediates

a) 2-Cyano-4,6-bistrifluoromethylbenzimidazole

12.2 g (50 mmol) of l,2-diamino-3,5-bistrifluoromethylbenzene are dissolved in 50 ml of glacial acetic acid, and 13.3 g (83 mmol) of methyl 2,2,2-trichloroacetamidate are subsequently added dropwise at room temperature. The batch is stirred until the adduct has disappeared. Using tetrahydrofuran, this reaction solution is subsequently flushed into a dropping funnel and added dropwise with ice-cooling to 290 ml of concentrated ammonia solution. After the mixture has been stirred for 1 hour at 25-30°C, it is concentrated on a rotary evaporator, the oily residue is treated with water, and the mixture is acidified using concentrated hydrochloric acid. The product is extracted using ethyl acetate, washed with water, dried over sodium sulfate and concentrated. The oil which remains is chromatographed on silica gel using ethyl acetate. This gives approximately 15 g of oil which is sufficiently pure for use in the subsequent step.

b) 1 ,2-Diamino-3,5-bistrifluoromethylbenzene

13.8 g (50 mmol) of 2-nitro-4,6-bistrifluoromethylaniline are dissolved in 140 ml of tetrahydrofuran, 6 g of Raney nickel are added, and the mixture is hydrogenated under atmospheric pressure at 20-25 °C. When the uptake of hydrogen has ceased, the catalyst is removed by filtration, and the solvent is distilled off on a rotary evaporator. 12.2 g of product are obtained.

c) 2-Nitro-4,6-bistrifluoromethylaniline

19.6 g (58 mmol) of 2-nitro-4,6-bistrifluoromethylbromobenzene are dissolved in 70 ml of ethanol, 15 g of ammonia are injected into the autoclave, and the mixture is heated to 125°C. After 6 hours, the autoclave is discharged, the reaction mixture is concentrated, stirred with water and filtered, and the solids are dried. Yield 14.8 g. Melting point 72-73°C.

d) 2-Nitro-4,6-bistrifluoromethylbromobenzene

19.5 g (66 mmol) of 2,4-bistrifluoromethylbromobenzene are heated at approximately 95°C. 80 ml of a mixture of concentrated sulfuric acid and fuming nitric acid (ratio 1:1) are added dropwise with stirring. When the addition has ended, stirring is continued for 2 hours at 95-100°C. When cold, the mixture is poured into ice- water, and the product is extracted using ethyl acetate and washed with water, dilute sodium hydroxide solution and saline, dried over sodium sulfate and concentrated. The oil which remains is chromatographed on silica gel using a short column and hexane. Yield 20.6 g of oil.

Here and hereinafter, the l(3)-dimethylsulfamoyl group can also be termed 1 (3)-dimethylarninosulfonyl.

Examples of other compounds which can be prepared in this manner or following one of the methods indicated further above are the following.

Table 0

Compound No. R₂ M.p.

Table 1

Compound No. R₂ M.p.

Table 2

Compound No. R₂ M.p.

Formulation examples of active ingredients of the formula I (% = per cent by weight)

2.1. Wettable powders

Active ingredient from the tables

Sodium ligninsulfonate

Sodium lauryl sulfate

Sodium diisobutylnaphthalene- sulfonate

Octylphenol polyethylene glycol ether (7-8 mol of ethylene oxide)

Highly-disperse silica

Kaolin

The active ingredient is mixed thoroughly with the additives, and the mixture is ground thoroughly in a suitable mill. This gives wettable powders which can be diluted with water to give suspensions of any desired concentration. 2.2. Emulsion concentrate

Emulsions of any desired concentration can be prepared by diluting this concentrate with water.

2.3. Dusts a) b) Active ingredient from the tables 5 % 8 % Talc 95 %

Kaolin - 92 %

Ready-to- use dusts are obtained by mixing the active ingredient with the carrier and grinding the mixture on a suitable mill.

2.4. Extruder granules

Active ingredient from the tables 10 %

N-Ligninsulfonate 2 %

Carboxymethyl cellulose 1 %

Kaolin 87 %

The active ingredient is mixed with the additives, and the mixture is ground and moistened with water. This mixture is extruded and subsequently dried in a stream of air.

2.5. Coated granules

Active ingredient from the tables 3 %

Polyethylene glycol (MW 200) 3 %

Kaolin 94 % (MW = molecular weight) In a mixer, the finely-ground active ingredient is applied uniformly to the kaolin which has been moistened with polyethylene glycol. In this manner, dust-free coated granules are obtained.

2.6. Suspension concentrate

Active ingredient from the tables 40 %

Ethylene glycol 10 %

Nonylphenol polyethylene glycol ether 6 % (15 mol of ethylene oxide)

Sodium ligninsulfonate 10 %

Carboxymethylcellulose 1 %

37% aqueous formaldehyde solution 0.2 %

Silicone oil in the form of a 75 % aqueous emulsion 0.8 %

Water 32 %

The finely-ground active ingredient is mixed intimately with the additives. This gives a suspension concentrate from which suspensions of any desired concentration can be prepared by dilution with water.

3. Biological examples

Example 3.1: Action against Plasmopara viticola on vines a) Residual-protective action

Vine seedlings in the 4-5-leaf stage are sprayed with a spray mixture (0.02 % of active ingredient) prepared with a wettable powder of the active ingredient After 24 hours, the treated plants are infected with a sporangia suspension of the fungus. Fungus infestation is assessed after incubation for 6 days at a relative atmospheric humidity of 95-100 % and at 20°C.

b) Residual-curative action

Vine seedlings in the 4-5-leaf stage are infected with a sporangia suspension of the fungus. The infected plants are incubated in a humid chamber for 24 hours at a relative atmospheric humidity of 95-100 % and at 20°C and then dried and sprayed with a spray mixture (0.02 % of active ingredient) prepared with a wettable powder of the active ingredient. After the spray coating has dried on, the treated plants are returned to the humid chamber. The fungus infestation is assessed 6 days after the infection.

A good to very good activity against Plasmopara viticola on vines is achieved by using the compounds of Tables 0, 1 and 2 (fungus infestation reduced to 10-0 %); active ingredients Nos. 0.3, 1.3 and 2.2, in particular, cause complete suppression of fungus infestation (residual infestation 0 to 5 %). In contrast, the level of Plasmopara infestation of untreated, but infected control plants is 100 %.

Example 3.2: Action against Phytophthora on tomato plants

Residual-protective action

Tomato plants are grown for 3 weeks and then sprayed with a spray mixture (0.02 % of active ingredient) prepared with a wettable powder of the active ingredient. After

24 hours, the treated plants are infected with a sporangia suspension of the fungus. The fungus infestation is assessed after the infected plants have been incubated for 5 days at a relative atmospheric humidity of 90-100 % and at 20°C.

Compounds from Tables 0, 1 and 2 exhibit a sustainable activity (fungus infestation less than 20 %). Infestation is prevented virtually completely (0 to 5 % infestation) using compound Nos. 0.3, 1.3, 2.2 and others. In contrast, the level of phytophthora infestation of untreated, but infected control plants is 100 %.

Example 3.3: Action against Phytophthora on potato plants

Residual-protective action

Potato plants (age: 2-3 weeks; variety: Bintje) are grown for 3 weeks and then sprayed with a spray mixture (0.02 % of active ingredient) prepared with a wettable powder of the active ingredient After 24 hours, the treated plants are infected with a sporangia suspension of the fungus. The fungus infestation is assessed a ter the infected plants have been incubated for 5 days at a relative atmospheric humidity of 90-100 % and at 20°C.

Compounds from Tables 0, 1 and 2 exhibit a sustainable activity (fungus infestation less than 20 %). Infestation is prevented virtually completely (0 to 5 % infestation) using compound Nos. 0.3, 1.3, 2.2 and others. In contrast, the level of phytophthora infestation of untreated, but infected control plants is 100 %. Example 3.4: Action against Pythium on maize and sugar beet a) Action after soil drench

The fungus is grown on sterile oat kernels and added to a soil/sand mixture. Flowerpots are filled with this infected soil, and maize or sugar beet seed is sown. Immediately after sowing, the test preparations, which have been formulated as wettable powders, are poured over the soil in the form of an aqueous suspension (20 ppm of active ingredient relative to the soil volume). The pots are then placed in a greenhouse at 20-24°C for 2-3 weeks. The soil is kept evenly moist by constantly being sprinkled with a little water. When the test is evaluated, the emergence of maize or sugar beet plants as well as the proportion of healthy and diseased plants is determined.

b) Action after seed-dressing

The fungus is grown on sterile oat kernels and added to a soil/sand mixture. Flowerpots are filled with this infected soil, and maize or sugar beet seed is sown, which has been dressed with the test preparations formulated as a powder for seed treatment (1000 ppm of active ingredient relative to the weight of the seeds). The pots together with the seeds are placed in a greenhouse at 20-24°C for 2-3 weeks. The soil is kept evenly moist by constantly being sprinkled with a little water. When the test is evaluated, the emergence of maize or sugar beet plants as well as the proportion of healthy and diseased plants is determined.

Treatment with compound No. 1.3 from Table 1 results in an emergence rate of over 80 %, the plants having a healthy appearance.

Claims

WHAT IS CLAIMED IS:

* 1. A benzimidazolesulfonic acid derivative of the formula I

in which the R₂SO₂ group is the 1- or 3-position and causes the formation of pure or mixed positional isomers relative to the CF₃ substituents and in which the substituents are as defined below:

R_x is CN or -CS(=O)_nNH₂,

R₂ is C_rC₄alkyl, C₃-C,₅cycloalkyl or -N(R')₂, in which R' substituents are identical or different C₁-C₃alkyl radicals; n is 0 or 1.

2. A benzimidazolesulfonic acid derivative of the formula lb in which the R₂SO₂ group is in the 1- or 3-position and causes the formation of pure or mixed positional isomers relative to the CF₃ substituents, and in which the substituents are defined as follows:

R₂ is Cj- alkyl, C₃-C₆cycloalkyl or -N(R')₂, in which R' substituents are identical or different C_rC₃alkyl radicals.

3. A compound as claimed in claim 1, in which

R₂ is C₂-C₂alkyl, cyclopropyl or -N(R')₂, where R' is methyl or ethyl and n is 0 or 1.

4. A compound as claimed in claim 3, in which R₂ is methyl or N(CH₃)₂ and n is 0 or 1.

5. A compound as claimed in claim 2, in which R₂ is methyl or -N(CH₃)₂.

6. The compound l(3)-dimethylaminosulfonyl-2-carbothioamido-4,6-bistrifluoro- methylbenzimidazole-S-oxide according to claim 3.

7. The compound l(3)-dimethylaminosulfonyl-2-carbothioamido-4,6-bistrifluoro- methylbenzimidazole according to claim 3.

8. The compound l(3)-dimethylaminosulfonyl-2-cyano-4,6-bistrifluoromethyl- benzimidazole according to claim 1.

9. A compound according to claim 4, in which R₂ is dimethylamino and n is 0 or 1.

10. A composition for controlling and preventing infestation of plants by microorganisms, which comprises applying, as active ingredient, a compound of the formula I together with a suitable carrier material.

11. A method of controlling and preventing infestation of plants by microorganisms, which comprises applying, as active ingredient, a compound of the formula I to the plants, parts of the plant or the plant substrate.

12. The use of a compound according to claim 1 as a microbicide.

13. A process for the preparation of a compound of the formula lb according to claim 1, which comprises reacting a compound of the formula la with H₂S in the presence of a base at temperatures from -20 to +80°C.

14. A process for the preparation of a compound of the formula Ic according to claim 1, which comprises oxidising a compound of the formula lb with organic peroxides or with hydrogen peroxide at temperatures from -20°C to +60°C.

15. The intermediate of the formula III

AMENDED CLAIMS

[received by the International Bureau on 6 December 1993 (06.12.93) original claims 8 and 15 deleted ; original claim 1 amended ; _: - remaining claims unchanged ( 2 pages ) ]

1. A benzimidazolesulfonic acid derivative of the formula I

R_ is CN or -CS(=O)_nNH₂,

R₂ is Cj-C₄alkyl, C₃-C₆cycloalkyl or -N(R')₂, in which R' substituents are identical or different C₁-C₃alkyl radicals; n is 0 or 1, with the proviso that Rj is -CS(=0)_nNH₂ ifR₂ is dimethylamino.

R₂ is Cj-C₄alkyl, C₃-C₆cycloalkyl or -N(R')₂, in which R' substituents are identical or different C_rC₃alkyl radicals.

3. A compound as claimed in claim 1, in which

R₂ is C]-C₂alkyl, cyclopropyl or -N(R')₂. where R' is methyl or ethyl and n is 0 or 1.

5. A compound as claimed in claim 2, in which R₂ is methyl or -N(CH₃)₂.

6. The compound l(3)-dimethylaminosulfonyl-2-carbothioamido-4,6-bistrifluoro- methylbenzimidazole-S-oxide according to claim 3. 7. The compound l(3)-dimethylaminosulfonyl-2-carbothioamido-4,6-bistrifluoro- methylbenzimidazole according to claim 3.

12. The use of a compound according to claim 1 as a microbicide.

14. A process for the preparation of a compound of the formula lc according to claim 1, which comprises oxidising a compound of the formula lb with organic peroxides or with hydrogen peroxide at temperatures from -20°C to +60°C.