1,2-Benzisothiazoles. Part I. Reaction of 3-chloro-1,2-benzisothiazole with nucleophiles

Abstract

3-Chloro-1,2-benzisothiazole reacts with a range of nucleophiles to give products which arise from fission of the thiazole ring. Sodium cyanide in aqueous acetone gives a mixture consisting of o-cyanophenyl thiocyanate (62%), bis-(o-cyanophenyl) disulphide (22%), and 2-acetyl-3-aminobenzo[b]thiophen (6%); copper(I) cyanide in dimethylformamide gives bis-(o-cyanophenyl) disulphide (80%); n-butyl-lithium gives o-(n-butylthio)-benzonitrile (90%); ethanolic sodium thiophenoxide gives mainly bis-(o-cyanophenyl) disulphide (50–55%), o-cyanophenyl phenyl disulphide (ca. 5%), and diphenyl disulphide (46–50%). Mechanisms involving nucleophilic attack at either sulphur or chlorine have been proposed to explain these reactions. In contrast, treatment with ethanolic sodium ethoxide affords 3-ethoxy-1,2-benzisothiazole and no ring-opened products.