Copper-Catalyzed Enantioselective Hetero-Diels-Alder Reaction of Danishefsky's Diene with β,γ-Unsaturated α-Ketoesters

A highly enantioselective hetero-Diels-Alder reaction of Danishefsky's diene with beta,gamma-unsaturated alpha-ketoesters was developed for the first time by virtue of chiral copper complexes. This protocol provided a facile access to optically active dihydropyranones bearing a quaternary center with high enantioselectivities and good yields. Furthermore, on the basis of the isolated intermediate analysis, the reaction pathway was substrate-dependent.