The Rearrangment of 3-Aminobenzo-[b]thiophenes to Tricyclic Benzoisothiazoles as Result of a Simple Azo-coupling Procedure

摘要

As a result of the reaction of ethyl 3-amino-4-dimethylamino-benzothiophene-2-carboxylate (1) with 2-thiazolediazonium salt 2, tricyclic ethyl 5-(thiazol-2-yl)-8-(thiazol-2-yldiazenyl)-5H-isothiazolo[3,4,5-d,e]cinnoline-3-carboxylate 4, instead of the expected 7-thiazolylazo derivative 3, is formed. A mechanism in which sulfanyl cations occur as intermediates is proposed.