Phosphine-Catalyzed Asymmetric Synthesis of α-Quaternary Amine via Umpolung γ-Addition of Ketimines to Allenoates.

A first phosphine-catalyzed enantioselective umpolung γ-addition of ketimines to allenoates has been developed that provides efficient access to optically active γ,δ-unsaturated α-amino esters and δ-amino esters with a chiral tertiary stereocenter under mild conditions. The salient features of this reaction include general substrate scope, mild conditions, good yields, high enantioselectivity, ease of scale-up to gram scale, and further transformations.