2-Methylbenzothiazole synthesis from 2-Mercaptoaniline and Acetic Acid

2-Methylbenzothiazole is widely used as the half-product for the thiocyanine dyes photosensitisers synthesis. It usually is synthesized by action of an acetic anhydride in excess on 2-mercaptoaniline. High-temperature reaction of 2-mercaptoaniline derivatives with the organic acids at temperatures above 200oC was extensively studied, but the reaction with acetic acid was not described [1-5]. The method of benzothiazole and its lower 2-alkylsubstituted derivatives synthesis from zinc 2-aminomercaptide and lower aliphatic acids was earlier described, but even in this paper in the examples of 2-methylbenzothiazole synthesis acetic anhydride alone or its mixture with benzene was used [6]. We have elaborated a new efficient method of 2-methylbenzothiazole synthesis from 2-mercaptoaniline and acetic acid shown at the scheme 1