Enantioselective Synthesis of Dihydropyrazoles by Palladium/Xu‐Phos‐Catalyzed Alleneamination of β, γ‐Unsaturated Hydrazones with Propargylic Acetates

The palladium-catalyzed asymmetric carboamination reaction is one of the most significant transformations in organic chemistry. Herein, we report the first palladium-catalyzed asymmetric alleneamination of β, γ-unsaturated hydrazones with propargylic acetates. This protocol enables the efficient installation of various multisubstituted allene groups onto enantioenriched dihydropyrazoles in good yields (up to 96%) with up to 96% ee. The chiral sulfinamide phosphine ligand Xu-5 is responsible for high effciency and good enantioselectivity. The salient features of this reaction include the readily available starting materials, a broad substrate scope, an easy scale-up, mild reaction conditions and versatile transformations.