Indium(III)-Catalyzed Asymmetric Hetero-Diels-Alder Reaction of Brassard-Type Diene with Aliphatic Aldehydes

A highly diastereo- and enantioselective hetero-Diels-Alder (HDA) reaction of a Brassard-type diene with aliphatic aldehydes has been developed. The chiral N,N'-dioxide L2/In(OTf)(3) complex was efficient toward the obtention of the corresponding beta-methoxy-gamma-methyl alpha,beta- unsaturated delta-lactones in good yields (up to 86%) as well as dr and ee values (up to 97:3 cis/trans and 94% ee). In addition, the product 4a could be easily transformed into the methyl-protected epi-prelactone B by hydrogenation.