Rhodium(II)-Catalyzed Divergent Dearomative Cyclization of 1,3-Azoles with Cyclopropenes.

Herein, we report a rhodium(II)-catalyzed divergent dearomative cyclization of benzimidazoles and benzoxazoles with cyclopropenes that proceeds through a unified azolium ylide mechanism. Scaffold tuning of the 1,3-azole substrates enables two distinct pathways: pyrroloimidazoles from benzimidazoles and benzoxazoloazepines from benzoxazoles. This method features good functional group tolerance and gram-scale scalability, providing straightforward access to two classes of pharmaceutically relevant nitrogen heterocycles.