Expeditious assembly of fused dihydropyranones via N-heterocyclic carbene-catalyzed tandem Michael addition/lactonization.

A convergent and efficient NHC-catalyzed enantioselective tandem Michael addition/lactonization sequence of ynals with 1,2-dione as the dual-nucleophile is disclosed. This straightforward strategy expeditiously assembles the synthetically and pharmaceutically valuable optically active fused dihydropyranones in good to high yields (70-88%) and with excellent enantioselectivities (92-99% ee).