Amide‐Based Morita–Baylis–Hillman Carbonates for Phosphine‐Catalyzed Asymmetric (4+2) Annulation^†

Comprehensive Summary Chiral phosphine‐catalyzed asymmetric (4+2) annulation of the amide‐based Morita–Baylis–Hillman (MBH) carbonates with β,γ‐unsaturated butenolides has been developed to give enantiomer‐enriched bicyclic δ‐lactam γ‐butyrolactone compounds. The amide‐based MBH carbonates were first used as acceptor and aza‐C4 synthon in phosphine catalysis. Under mild reaction conditions, a variety of amide‐based MBH carbonates and unsaturated butenolides were well tolerated to provide chiral bicyclic δ‐lactam γ‐butyrolactone derivatives in high yields with excellent enantioselectivities as well as diastereoselectivities. A plausible reaction mechanism was also proposed based on control experiments and DFT calculations.