Enantioselective Synthesis of Substituted δ-Lactones by Cooperative Oxidative N-Heterocyclic Carbene and Lewis Acid Catalysis

Efficient construction of complex cylcopentane- or cyclohexane-fused delta-lactones employing redox activation of enals using a chiral N-heterocyclic carbene and LiCl as cooperative catalysts is described. The organocascade proceeds with excellent diastereo- (>99:1) and enantioselectivity (up to >99% cc) and comprises the formation of three bonds with three contiguous stereocenters.