Rhodium-Catalyzed Addition–Cyclization of Hydrazines with Alkynes: Pyrazole Synthesis via Unexpected C–N Bond Cleavage

Rhodium-catalyzed addition–cyclization of hydrazines with alkynes has been achieved to afford highly substituted pyrazoles under mild conditions. The cascade reaction involves two transformations: addition of the C–N bond of hydrazines to alkynes via unexpected C–N bond cleavage and intramolecular dehydration cyclization