Phosphine‐Catalyzed Enantioselective [1+4] Annulation of Morita‐Baylis‐Hillman Carbonates with α,β‐Unsaturated Imines

This work describes a phosphine‐mediated enantioselective [1+4] annulation of Morita‐Baylis‐Hillman carbonates with α,β‐unsaturated imines. In the presence of 1,2‐bis[(2 R ,5 R )‐2,5‐dimethylphospholano]‐benzene monoxide, Morita‐Baylis‐Hillman carbonates react with α,β‐unsaturated imines smoothly to furnish a series of chiral 2‐pyrrolines in moderate to high yields with excellent diastereo‐ and enantioselectivities (all d.r. values >20 : 1, in most cases >90% ee ). Importantly, a large number of α,β‐unsaturated imines with different substituents on either the nitrogen atom or the aromatic ring is compatible, offering a facile synthetic approach to the enantiomers of reported enantiopure 2‐pyrrolines.