Enantioselective [3+3] Annulation-Deoxalation Strategy for Rapid Access to -Oxoesters via N-Heterocyclic Carbene Catalysis

A new and unprecedented stereoselective synthetic approach to delta-oxoesters derivatives from readily available starting materials has been developed. This method, catalyzed by N-heterocyclic carbene, involves an annulation-deoxalation reaction of alkynyl aldehydes with 2,4-diketoesters and proceeds via the chiral alpha,beta-unsaturated acylazolium intermediates. The annulation includes the in situ formation of dihydropyranones, which undergo ring-opening methanolysis with Lewis acid activation, followed by deoxalation to afford chiral 1,5-ketoesters in moderate to good yields. [GRAPHICS] .