Radical Redox-Relay Catalysis: Formal [3+2] Cycloaddition of <i>N</i>‑Acylaziridines and Alkenes

We report Ti-catalyzed radical formal [3+2] cycloadditions of N-acylaziridines and alkenes. This method provides an efficient approach to the synthesis of pyrrolidines, structural units prevalent in bioactive compounds and organocatalysts, from readily available starting materials. The overall redox-neutral reaction was achieved via a redox-relay mechanism, which harnesses radical intermediates for selective CN bond cleavage and formation.