[3+2] Cycloaddition of Bicyclic Diaziridines with Acyl Azides: Synthesis of 1,3,5-Triazabicyclo[3.3.0]octanes.

An efficient, catalyst-free [3 + 2] cycloaddition between bicyclic diaziridines and acyl azides has been developed for the facile construction of valuable 1,3,5-triazabicyclo[3.3.0]octane scaffolds. This transformation features a broad substrate scope, excellent functional group tolerance, high atom economy, simple operation, and good scalability. It accommodates a wide range of substrates bearing aryl, heteroaryl, alkenyl, and alkyl groups, as well as drug- and natural product-derived bioactive motifs. This additive-free strategy provides a practical modular route to pharmaceutically relevant nitrogen-bridged bicyclic frameworks.