Chiral enamides, easily prepared in one step from a cyclic ketone and an oxazolidinone, are successfully employed in high-yielding, endo, and facially selective Hetero-Diels− Alder reactions involving activated oxadienes and Siever's reagent as catalyst. From the resulting bicyclic heteroadducts, a novel and efficient asymmetric modification for the Robinson annulation of cyclic monoketones is described.
