Cu-Catalyzed Tandem Cyclization of N-Benzyl 1,6-Diynes Via Vinyl Cations for Synthesis of Polycyclic N-Heterocycles

Intramolecular cyclization of aryl-substituted diynes has been demonstrated as an efficient and practical strategy for constructing polycyclic N-heterocycles. However, these reactions commonly rely on high temperatures or noble-metal catalysts. Herein, we report an efficient copper-catalyzed tandem cyclization of diynes. This reaction enables the one-step formation of three rings, providing an atom-economical and practical route to structurally valuable polycyclic N-heterocycles with moderate to excellent yields and excellent diastereoselectivities. This tandem cyclization presumably involves the formation of vinyl cation intermediates and copper carbene species. Importantly, these copper carbenes generated from such a diyne cyclization can be intercepted by an intramolecular aryl group rather than undergoing a previous [1,4]-H shift.