Metal‐Free [3 + 2] Cycloaddition of Vinyldiazo Compounds and N ‐Aryl Benzohydrazonoyl Chlorides: Efficient and Rapid Assembly of Pyrazolines

A highly general, metal‐free [3 + 2] cycloaddition of vinyl diazo compounds with in situ generated nitrile imines (from N ‐Aryl Benzohydrazonoyl Chlorides) has been developed, providing diazo‐containing, functionally enriched pyrazoline derivatives in high yields. The reaction is proposed to proceed via nucleophilic attack of the vinyldiazo compound on the nitrilimine, followed by intramolecular conjugate addition. Notably, this methodology features mild conditions and a broad substrate scope, and its synthetic utility was further demonstrated through late‐stage transformations.