Synthesis of Dihydropyrazoles via Ligand-Free Pd-Catalyzed Alkene Aminoarylation of Unsaturated Hydrazones with Diaryliodonium Salts

A ligand-free, palladium-catalyzed aminoarylation reaction of the unactivated alkenes in β,γ-unsaturated hydrazones is described. This protocol enables efficient and simultaneous formation of C­(sp³)–N and C­(sp³)–C­(sp²) bonds under mild conditions, providing a practical and general approach to various diversely substituted dihydropyrazoles in generally good yields, without the use of any stoichiometric external oxidant.