Rh(III)-Catalyzed Multicomponent Formal [4 + 2+1]/[4 + 1] Annulation for the Synthesis of Benzo[d]pyrazolo[1,5-a]azepin-4-ones.

A Rh(III)-catalyzed three-component cascade cyclization has been developed for the efficient synthesis of highly functionalized benzo[d]pyrazolo[1,5-a]azepin-4-ones (BPAPOs) from a sulfoxonium ylide, a vinyl diazo ester, and excess vinylene carbonate. The reaction proceeds through a formal [4 + 2+1]/[4 + 1] cyclization cascade, rapidly constructing the tricyclic BPAPO framework and forming five new chemical bonds in a one-pot process. Notably, the two stereocenters in the target molecules can be controlled through temperature-dependent diastereoselectivity: Temperature-controlled diastereoselectivity enables the selective formation of diastereomer 4 at 100 °C and diastereomer 5 at 70 °C, both with high dr values. Their relative configurations were confirmed by single-crystal X-ray diffraction. The method features broad substrate scope and good functional-group tolerance, providing efficient access to diverse tricyclic scaffolds for biological and medicinal chemistry.