Enantioselective Synthesis of Bicyclic δ-Lactones via N-Heterocyclic Carbene-Catalyzed Cascade Reaction.

The asymmetric reaction of cinnamylmethyl or cinnamylethyl malonates with aryl, hetaryl, alkenyl, or alkyl aldehydes delivers the title products containing three consecutive stereocenters in high yields, with excellent diastereoselectivities and very high enantioselectivities.