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.