Efficient Preparation of β-Branched γ,δ-Unsaturated Esters through Copper-Catalyzed Allylic Alkylation of Ketene Silyl Acetal

Copper-catalyzed allylic alkylation of ketene silyl acetals proceeded with excellent gamma-E-selectivity. Efficient alpha-to-gamma chirality transfer with anti-selectivity occurred in the reaction of enantioenriched secondary allylic phosphates, affording enantioenriched beta-branched gamma,delta-unsaturated esters. The reaction was readily scalable and highly reliable in terms of product yield and stereoselectivities.