Improved method for preparing trifluoroethyl benzothiadiazolecarboxylate.

Abstract

The title method comprises (1) esterifying m-aminobenzoic acid to obtain Me m-aminobenzoate; (2) reacting with thiocyanates in the presence of surfactant to obtain N-(3-methoxycarbonylphenyl)thiourea; (3) adding bromine in chlorobenzene or acetic acid to obtain 2-amino-7-(methoxycarbonyl)benzothiazole; (4) heating in KOH water soln., performing diazotization and ring-closure under acidic condition to obtain 1,2,3-benzothiadiazole-7-carboxylic acid; (5) esterifying with 2,2,2-trifluoroethanol under the presence of acylating agent (oxalyl chloride) to obtain 2,2,2-trifluoroethyl 1,2,3-benzothiadiazole-7-carboxylate. The thiocyanates may be potassium thiocyanate, sodium thiocyanate, or ammonium thiocyanate; the surfactant may be quaternary ammonium salts or crown ethers. This invention has increased yield of product. [on SciFinder(R)]