Fused heterocycles from o-acylbenzenethiol derivatives

The oximes of 2-acylthioanisole derivatives may be conveniently converted into 1,2-benzisothiazoles by acetic anhydride in pyridine. 3-(2-Methylthiophenyl)-1,2-benzisothiazole, prepared by this method, has been further converted into the 1,2-benzisothiazolo[2,3-b]-1,2-benzisothiazolium system. The phenylhydrazones of certain 2-acylthioanisoles are also cyclized by polyphosphoric acid to 2-(2-methylthio)phenylindoles, which are further converted into benzo[b]thieno[3,2-b]indoles by demethylation and oxidation.