METHOD OF PRODUCING POTASSIUM SALT OF 2-[1-(1,1-DIOXOTHIETANYL-3)BENZIMIDAZOLYL-2-THIO]ACETIC ACID Russian patent published in 2014 - IPC C07D409/04 

FIELD: chemistry.

SUBSTANCE: method includes synthesis of o-phenylenediamine (o-PDA) dihydrochloride first by dissolving o-PDA in hydrochloric acid solution, filtering the obtained solution and vacuum evaporation to a dry residue which is dried at 105-110°C; mixing the dry o-PDA dihydrochloride with urea, heating the obtained mixture on a paraffin bath to 150°C, cooling the obtained melt, grinding and dissolving in a warm diluted sodium hydroxide solution, filtering, adding hydrochloric acid to the filtrate until neutralisation, filtering out the precipitated benzimidazolone-2, purifying by recrystallising from ethanol; adding phosphorus oxychloride to the benzimidazol-2one, adding concentrated hydrochloric acid, heating at 145-150°C for 4 hours, stirring after cooling the mixture and pouring on ice, filtering out the reaction mixture, neutralising the filtrate with 10 ammonia solution to pH 7-8, filtering the 2-chlorobenzimidazole precipitate, drying at 60°C, recrystallising from a mixture of ethanol and water in ratio of 1:1; synthesis of 2-chloromethylthiirane by mixing epichlorohydrin and ethanol, cooling to 0°C, adding ground thiourea, mixing for 60 minutes at 0-5°C, slowly raising temperature to 20°C for 60 minutes and stirring at said temperature for 3 hours, filtering, pouring the filtrate in three portions into a separating funnel containing 3 litres of water, collecting the organic layer, washing with water, filtering, drying the filtrate, adding anhydrous calcium chloride, filtering and vacuum distillation. Further, the method includes synthesis of 1-(thietanyl-3)-2-chlorobenzimidazole by adding 2-chlorobenzimidazole to aqueous potassium hydroxide solution, heating to 70°C and adding 2-chloromethylthiirane, stirring the reaction mixture at said temperature until achieving pH≤7, filtering out the filtrate, washing with diethyl ether, 10% potassium hydroxide solution, water, drying, purifying by crystallisation from a mixture of ethanol and water in ratio of 1:1, separating the organic and aqueous layers, adding hydrochloric acid solution to the aqueous solution to pH 5-6, filtering out the precipitate, washing with water and drying. Further, 2-[1-(1,1-dioxothietanyl-3)benzimidazolyl-2-thio]acetic acid is obtained using thioglycolic acid solution and potassium hydroxide solution in distilled water, boiling for 30 minutes, cooling to room temperature, filtering the solution, acidifying the filtrate with hydrochloric acid to pH 3-4, filtering out the precipitate, washing with water and drying. The end product is obtained by adding potassium hydroxide to a solution of 2-[1-(1,1-dioxothietanyl-3)benzimidazolyl-2-thio]acetic acid in ethanol, boiling the mixture for 45 minutes, cooling, filtering out the filtrate and drying.

EFFECT: novel method of producing a compound, which increases the output of the end product while reducing the time and cost of production.

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