One-pot formation of chiral polysubstituted 3,4-dihydropyrans via a novel organocatalytic domino sequence involving alkynal self-condensation.

The self-condensation of alkynals was for the first time implemented under mild organocatalytic conditions and was successfully linked with a domino organocatalytic inverse-electron-demand oxa-Diels-Alder reaction, which led to the development of a facile one-pot method to produce a wide variety of polysubstituted chiral 3,4-dihydropyrans with good to high yields and diastereoselectivities and high enantioselectivities. The unprecedented alkynal self-condensation was revealed to pass through secondary amine-catalyzed C-C triple bond hydration and subsequent aldol condensation.