Synthesis of 4,5-Dihydropyrazoles via Palladium-Catalyzed Cyclization Reactions of β,γ-Unsaturated Hydrazones with Aryl Iodides

A novel two-component cyclization toward the synthesis of polysubstituted 4,5-dihydropyrazoles was carried out: i.e., cyclization of β,γ-unsaturated hydrazones with aryl iodides catalyzed by Pd(0). The reaction forms new carbon–carbon bonds and carbon–nitrogen bonds with moderate to good reactivity.