Copper(I)-Catalyzed Oxidative Coupling between 2‑Aminobenzothiazole and Terminal Alkyne: Formation of Benzothiazine

An unprecedented formation of benzothiazine during copper­(I)-catalyzed oxidative coupling of 2-aminobenzothiazole and terminal alkyne in air has been observed. This unique transformation possibly occurs through the ring opening of 2-aminobenzothiazole and subsequent oxidative coupling with alkyne followed by intramolecular cyclization. A variety of substituted benzo­[b]­[1,4]­thiazine-4-carbonitriles are obtained by this protocol.