BENZOTHIAZOLE DERIVATIVES AS FUNGICIDE

Abstract: The invention relates to a benzothiazole derivative represented by general formula (I), wherein X is NHR, R or OR; R is lower alkyl, cycloalkyl, aryl or substituted aryl; Y is lower alkyl, alkenyl, alkyloxycarbonylalkyl, benzyl or substituted benzyl; and Z is lower alkoxy or hydrogen. This compound is useful as an active ingredient of agrohorticultural bactericides.

Description: Technical Field The invention relates to a benzothiazole derivative which is useful as an agricultural and horticultural fungicide. Background Art Thanks to fertilizers, pesticides and various agricultural materials, a high productivity has been achieved in recent agriculture. On the other hand, there are some serious problems in this field including the appearance of chemical-tolerant strains caused by repetitive application of pesticides and disease damage caused by continuous cropping (i.e. by continuous annual culture of a single crop). Under these circumstances, it has been urgently required to develop a highly safe chemical. Thus, the present invention provides a means for solving these problems. Disclosure of the Invention The present invention provides a benzothiazole derivative represented by the following general formula, and furthermore provides an agricultural and horticultural fungicide containing the benzothiazole derivative as an active ingredient: wherein X, Y and Z are selected from the following combinations: The compound of the present invention may be synthesised in the following manner. First, a 2-aminobenzothiazole represented by the following general formula [I]: wherein Z is as defined above, is reacted with the corresponding halide to thereby obtain a 3-substituted 2-iminobenzothiazole [II]: wherein Z and Y are each as defined above. Next, the compound [II] is reacted with the corresponding isocyanate, acid halide or halogenoformate in an appropriate solvent. Best Mode for Carrying Out the Invention Examples of the organic solvent to be used in the reaction of the 3-substituted 2-iminobenzothiazole with the isocyanate include dioxane, tetrahydrofuran, acetone, methyl ethyl ketone, benzene, toluene, xylene, monochlorobenzene, dichlorobenzene, dimethylformamide, acetonitrile and the like. Furthermore, examples of a catalyst effective for this reaction include organometallic compounds such as dibutyltin dilaurate and tertiary amines such as triethylamine. The solvent for the reaction between the 3-substituted 2-iminobenzothiazole and the acid halide or the halogenoformate may be selected from among those described above for the reaction of the 3-substituted 2-iminobenzothiazole with the isocyanate. Examples of a deacidifying agent effective for this reaction include tertiary amines such as triethylamine and alkali metal carbonates or alkaline earth metal carbonates such as sodium hydrogencarbonate, potassium carbonate and calcium carbonate. The above-described reaction between the 3-substituted 2-iminobenzothiazole and the isocyanate, acid halide or halogenoformate may be preferably conducted at a temperature of from 0 to 100°C. Now typical examples for the synthesis of the benzothiazole derivative of the present invention will be given. Table 1 summarizes the compounds thus synthesized. Synthesis Example 1 Synthesis of 3-allyl-2-methoxycarbonyliminobenzothiazole (compound No. 4 in Table 1): To a mixture comprising 3.8 g of 3-allyl-2-iminobenzothiazole, 3.4 g of sodium hydrogencarbonate and 50 ml of tetrahydrofuran was added 1.9 g of methyl chloroformate dropwise at room temperature under stirring. After reacting for two hours, the reaction mixture was poured into approximately 200 ml of water. The crystals precipitated were collected by filtering to thereby obtain 4.5 g of the objective compound. Yield: 91%. m.p.: 121 - 124°C. IR (cm⁻¹): 1638. Synthesis Example 2 Synthesis of 3-benzyl-2-[(N-cyclohexylcarbamoyl)-imino] benzothiazole (compound No. 13 in Table 1): To a solution of 1.8 g of 3-benzyl-2-iminobenzothiazole and a catalytic amount of dibutyltin dilaurate in 30 ml of acetone was added 0.95 g of cyclohexyl isocyanate dropwise. After seven hours, the reaction mixture was poured into approximately 100 ml of water. The crystals precipitated were collected by filtering to thereby obtain 2.0 g of the objective compound. Yield: 72%. m.p.: 170.5 - 173.5°C. IR (cm⁻¹): 3425 and 1640. Synthesis Example 3 Synthesis of 3-allyl-2-pivaloyliminobenzothiazole (compound No. 9 in Table 1): To a solution of 2.0 g of 3-allyl-2-iminobenzothiazole and 1.5 g of triethylamine in 30 ml of tetrahydrofuran was added 1.3 g of pivaloyl chloride dropwise at room temperature under stirring. After reacting for five hours, the reaction mixture was poured into approximately 200 ml of water. The crystals precipitated were collected by filtering to thereby obtain 2.6 g of the objective compound. m.p.: 60 - 62°C. IR (cm⁻¹ ): 1610. In using the compound of the present invention as a fungicide, it may be mixed with various carriers and formulated into various forms such as wettable powder, emulsion, dust, granules or suspension by a conventional method employed in the art. The carrier may be selected from among liquid ones such as conventional organic solvents and solid ones such as conventional clay minerals and pumice. The formulation may further contain, for example, a surfactant to thereby give emulsifiability, dispersibility, spreadability or the like. Furthermore, it may be mixed with fertilizers or other agricultural chemicals such as insecticide, fungicide or the like. In order to use the formulation as a fungicide, it is necessary to sufficiently apply the active compound in such a manner as to fully exert the desired effect. The amount of application thereof may range generally from 50 to 2000 g/ha, preferably from 200 to 1000 g/ha. The formulation may be in the form of a wettable powder, an emulsion, a dust, granules or a suspension containing 0.1 to 50% by weight of the active ingredient. In preparing an emulsion, the active ingredient is dissolved in an agriculturally acceptable organic solvent and an emulsifier which is soluble in the solvent is then added thereto. Suitable examples of the solvent include xylene, o-chlorotoluene, cyclohexanone, isophorone, dimethylformamide, dimethylsulfoxide and mixtures thereof. Among these solvents, aromatic hydrocarbons and mixtures thereof with ketones and polar solvents are particularly suitable. The surfactant to be used as an emulsifier may be used in an amount of from 1 to 20 % by weight of the emulsion. Any of the anionic, cationic and nonionic surfactants may be selected therefor. Examples of the anionic surfactants include salts of alkyl sulfates, alkyl diphenyl ether disulfonates, naphtylmethanesulfonates, lignin sulfonates, alkyl sulfosuccinates, alkylbenzenesulfonates and alkyl phosphates. Examples of the cationic surfactants include alkylamine salts and quaternary ammonium salts. Examples of the nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylaryl ethers, sorbitan fatty esters, polyoxyethylene sorbitan fatty esters, polyoxyethylene sorbitol fatty esters, glycerol fatty esters and polyoxyethylene fatty esters. The concentration of the active ingredient may range from 0.5 to 20 % by weight, preferably from 1 to 10 % by weight. A wettable powder may be formulated by adding the active ingredient to an inert solid carrier in the form of a fine powder and a surfactant. The content of the active ingredient may range from 2 to 50 % by weight while the content of the surfactant may range from 1 to 20 % by weight in general. The solid carrier commonly mixed with the active ingredient may be selected from among natural clay, silicates, silica and alkaline earth metal carbonates. Typical examples thereof include kaolin, zieclite, talc, diatomaceous earth, magnesium carbonate, calcium carbonate, dolomite. Anionic surfactants, nonionic surfactants or mixtures thereof may be employed as an emulsifier, a spreader or a dispersant to be generally used for formulation of the wettable powder. Similar surfactants to those cited above regarding the emulsion may be used therefor. A dust may be formulated by blending the active ingredient with inert carriers commonly used in the dust formulation, for example, talc, fine clay power, pyrophyllite, diatomaceous earth, magnesium carbonate. The concentration of the active ingredient may range from 0.1 to 20 % by weight, preferably from 0.5 to 5 % by weight. Granules may be formulated by mixing the active ingredient with inert carriers in the form of a fine powder, such as bentonite, kaolin clay, diatomaceous earth or talc, kneading the mixture together with water and then granulating the same with a granulating machine. Alternatively, the granules may be prepared by dissolving the active ingredient together with a spreader, and depositing the resulting solution onto a granular carrier previously granulated to have the particle size of 15 to 30 mesh, or onto a granular mineral obtained by grinding natural pumice, acid clay or zeolite followed adjusting its particle size. These granules may contain 0.2 to 20 % by weight, preferably 1 to 10 % by weight, of the active ingredient. A suspension may be prepared by finely powdering the active ingredient and mixing the same with a surfactant and water. As the surfactant to be used herein, any of the anionic, cationic and nonionic ones as well as mixtures thereof cited above regarding the preparation of the emulsion may be selected. It is generally used in an amount of from 1 to 20 % by weight. The active ingredient may be contained in an amount of from 1 to 50 % by weight, preferably from 2 to 20 % by weight. Examples To further illustrate the present invention, the following Examples will be given, in which "parts" represent part by weight. Formulation Example 1: Emulsion compound No. 24 10 parts o-chlorotoluene 50 parts cyclohexanone 36 parts Sorpol 900B 4 parts The above components were homogeneously mixed together and dissoloved to thereby obtain an emulsion of the present invention. Formulation Example 2: Wettable powder compound No. 6 30 parts kaolin clay 63 parts Sorpol 5039 5 parts Sorpol 5060 2 parts The above components were mixed together and ground to thereby obtain a wettable powder of the present invention. Formulation Example 3: Dust compound No. 7 2 parts kaolin clay 98 parts The above components were mixed together and ground to thereby obtain a dust of the present invention. Formulation Example 5: Suspension compound No. 29 10 parts ethylene glycol 5 parts Sorpol 3078 5 part Sorpol 7512 0.5 part water 79.5 parts The above components were homogeneously mixed together and ground to thereby obtain a suspension of the present invention. To illustrate the mycelium growth-inhibiting effect on typical molds and the plant disease-preventing effect of the compound of the present invention, the following Test Examples will be given. Test Example 1: Mycelium growth-inhibiting effect on Petri dish A solution of the compound of the present invention in dimethyl sulfoxide was added to a potato dextrose agar medium (PDA medium) to give a concentration of 100 ppm. Then a plate medium was prepared in a Petri dish of 9 cm in diameter. Two mycelia 4 mm in diameter, which had been cultured in a PDA medium, were placed on the agar medium and cultured at 25°C for two days (in the case of Pythium graminicola ), five days (in the case of Fusarium oxysporum ) or three days (in the case of Rhizoctonia solani ). Then the diameter of the obtained colony was compared with that of a control lot wherein no chemical was added and the growth inhibition ratio was calculated according to the following equation. Table 2 gives the results wherein each value is a mean value. Test Example 2: Preventive effect on cucumber downy mildew A cucumber seedling (variety: Kashu No. 1) was grown in an unglazed pot of 9 cm in diameter. On reaching the trifoliate stage, 10 ml of a formulation of each compound prepared by the method of Formulation Example 1 (concentration: 100 ppm) was sprayed thereon with a spray gun. Three plants were employed per compound. After drying for four hours, a spore suspension (2 X 10⁵/ml) of Pseudoperonospora cubensis causative of cucumber downy mildew was inoculated to the plants by spraying. Following the inoculation, each plant was cultured at 20°C under moisture-saturated conditions for 12 hours and then at 20°C at a relative humidity of 70 to 80% for six days. Seven days after the inoculation, lesions formed on the leaves of the monofoliate and difoliate stages were examined and the preventive value (%) was calculated according to the following equation. Table 3 gives the results. Compound No. Preventive value (%) 4 45 5 75 6 80 7 85 10 100 11 80 13 50 24 90 29 85 Test Example 3: Preventive effect on wheat powdery mildew : A wheat seedling (variety: Norin No. 61) was grown in a pot of 9 cm in diameter. On reaching the difoliate stage, 20 ml of a formulation of each compound prepared by the method of Formulation Example 1 (concentration: 100 ppm) was sprayed thereon with a spray gun. 13 plants were employed per lot for each compound and two lots were employed for each compound. One day after the spraying, each plant was inoculated with conidia of Eryshiphe graminis causative of wheat powder mildew by application. Following the inoculation, each plant was cultured at 20°C under moisture-saturated conditions for 12 hours and then at 20°C at 12 hour photoperiod for six days. Seven days after the inoculation, lesions formed on the leaves of the monofoliate and difoliate stages were examined and the preventive value (%) was calculated in the same manner as in the above-discribed Test Example 2. Table 4 gives the results. Compound No. Preventive value (%) 2 75 4 95 6 95 7 85 12 50 13 75 14 50 28 75 29 75 As described above, the compound of the present invention exerts a growth-inhibiting effect of various molds, suppresses the occurrence of plant diseases and thus provides an effective means for elevating productivity without giving any chemical damage.

Claims: A benzothiazole derivative represented by the following general formula: wherein X, Y and Z are selected from the following combinations: An agricultural and horticultural fungicide containing a benzothiazole derivative as claimed in Claim 1 as an active ingredient. A process for the synthesis of a benzothiazole derivative as defined in Claim 1, which comprises reacting a 2-aminobenzothiazole represented by the general formula [I]: wherein Z is as defined in Claim 1, with a halide to thereby obtain a 3-substituted 2-iminobenzothiazole of the general formula [II]: wherein Y and Z are each as defined in Claim 1, and reacting the 3-substituted 2-iminobenzothiazole thus obtained with an isocyanate, an acid halide or a halogenoformate in an appropriate solvent.

Inventors: KAWADA HIROSHI, NISHIMURA SHINJI, TANAKA KEN-ICHI, YAMAZAKI MITSUMASA, KAWADA, HIROSHI, NISHIMURA, SHINJI, TANAKA, KEN-ICHI, YAMAZAKI, MITSUMASA
Applicants: HODOGAYA CHEMICAL CO LTD, HODOGAYA CHEMICAL COMPANY, LIMITED
Application year: 1990
Main classification: C07D277
IPC codes: A01N47, C07D277, A01N43