The treatment of a variety of heterocyclic thiones with hydrogen peroxide in acetic acid produces either heteroaromatic cations or the corresponding "oxo" compound. The results may be correlated with structural and electronic features. Benzo substitution or the presence of strongly electron withdrawing groups in the molecule favors the latter product, whereas the presence of a σ trivalent nitrogen atom in the molecule favors the former.
2,1-Benzisothiazolium salts react with several stabilized carbanions to give products that are derived by attack at the carbon atom of the heterocyclic ring.