MECHANISM OF FORMATION OF BENZOTHIAZOLE-2-THIOL

The formation of benzothiazole-2-thiol from aniline, carbon disulphide and sulphur at 230 degrees C was shown to occur by a sequence of thre e principal steps. Labelling experiments confirmed that both sulphur a toms originate from carbon disulphide. An initial polar reaction to fo rm thiocarbanilide via phenylcarbamic acid and a tetrahedral intermedi ate is followed by radical cyclization of these to benzothiazole-2-thi ol and 2-phenylaminobenzothiazole; the latter is converted into the de sired product by a polar displacement of aniline by H2S. Mechanisms fo r the formation of minor byproducts are also considered. (C) 1998 John Wiley & Sons, Ltd.