Cu(I)-Catalyzed [3 + 3] Cycloaddition Reaction of Ethynyl Methylene Cyclic Carbamates and Azomethine Imines: Synthesis of 1,2,4-Triazinane Derivatives

A copper-catalyzed, efficient, operationally simple, and general method for straightforward synthesis of 1,2,4-triazinane derivatives employing EMCCs (ethynyl methylene cyclic carbamates) as precursors reacting with azomethine imines was first reported. A wide variety of 1,2,4-triazinane derivatives were obtained in acceptable to good yields under mild conditions. This protocol features a broad substrate scope, high functional group tolerance, and easy operation, therefore enabling late-stage functionalization. In addition, a scale-up experiment further highlighted the synthetic utility.