Diastereo‐ and Enantioselective Construction of γ‐Butenolides through Chiral Phosphane‐Catalyzed Allylic Alkylation of Morita–Baylis–Hillman Acetates

Abstract

Abstract A series of multifunctional, chiral amide–phosphane organocatalysts have been designed and synthesized for the allylic substitution of Morita–Baylis–Hillman (MBH) acetate with 2‐trimethylsilyloxyfuran for butenolide synthesis. This reaction was achieved in good to excellent yield (42–98 %) and high ee (85–99 %) with respect to a wide range of substrates in absolute MeOH or CH 3 CN, using chiral amide–phosphane organocatalysts with an amide moiety including an active proton. NMR tracing experiments identified the critical phosphonium intermediates involved in the catalytic cycles. Computational studies disclosed the origins of diastereo‐ and enantioselectivity, in particular, revealing that the active proton of the amide moiety is the critical factor for the catalyst to have high enantiofacial control.