Novel alternative for the N-S bond formation and its application to the synthesis of benzisothiazol-3-ones

reaction: see text] The synthesis of a series of benzisothiazolone derivatives starting from the readily available methyl thiosalicylate is presented. The key cyclization step features the formation of a N-acylnitrenium ion, generated by the hypervalent iodine reagent PIFA, and its succeeding intramolecular trapping by the thiole moiety leading to the construction of the title compounds by formation of a new N-S bond.