Rhodium-Catalyzed Annulative Coupling Using Vinylene Carbonate as an Oxidizing Acetylene Surrogate

Transition-metal-catalyzed C–H activation and
subsequent
oxidative cyclization with alkynes has been a powerful tool for the
synthesis of polycyclic aromatic compounds. Despite the substantial
progress in this field, it is still a significant challenge to establish
synthetic methodologies for the construction of nonsubstituted vinylene-fused
aromatics. We herein report a Rh­(III)-catalyzed C–H/N–H
annulation with vinylene carbonate as an acetylene surrogate. Vinylene
carbonate also acts as an internal oxidant to regenerate the Rh­(III)
species in situ; thus, no external oxidant is required to trigger
the oxidative annulation. This protocol is applicable to the direct
synthesis of various N-heteroaromatics.