Chiral Bifunctional Phosphine Ligand-Enabled Cooperative Cu Catalysis: Formation of Chiral α,β-Butenolides via Highly Enantioselective γ-Protonation

alpha,beta-Butenolides with >= 96% enantiomeric excess are synthesized from beta,gamma-butenolides via a novel Cu(I)-ligand cooperative catalysis. The reaction is enabled by a chiral biphenyl-2-ylphosphine ligand featuring a remote tertiary amino group. Density functional theory studies support the cooperation between the metal center and the ligand basic amino group during the initial soft deprotonation and the key asymmetric gamma-protonation. Remarkably, other coinage metals, that is, Ag and Au, can readily assume the same role as Cu in this asymmetric isomerization chemistry.