Direct Asymmetric Allylic Alkylation of Butenolides with Morita−Baylis−Hillman Carbonates

The direct asymmetric allylic alkylation of β,γ-butenolides with MBH carbonates to access γ,γ-disubstituted butenolides containing adjacent quaternary and tertiary chiral centers has been presented in excellent stereoselectivities (86−96% ee, dr >95:5) and moderate to good yield (50−83%). Their synthetic utility has been well demonstrated by the facile construction of bicyclic lactones bearing 4−5 stereogenic centers.