Dual Roles of β‑Oxodithioesters in the Copper-Catalyzed Synthesis of Benzo[e]pyrazolo[1,5‑c][1,3]thiazine Derivatives

A facile and efficient method for the chemoselective synthesis of benzo­[e]­pyrazolo­[1,5-c]­[1,3]­thiazine derivatives has been developed by tandem Ullmann coupling reactions of β-oxodithioesters (ODEs) with 3-(2-bromoaryl)-1H-pyrazoles in C–S bond formation manner, in which ODEs play dual roles as both a substrate and a ligand. A series of benzo­[e]­pyrazolo­[1,5-c]­[1,3]­thiazine derivatives were provided in good to excellent yields with CuI as the copper source in the presence of NaOH in CH3CN at 80 °C under a N2 atmosphere.