Asymmetric Organocatalysis: An Efficient Enantioselective Access to Benzopyranes and Chromenes

Valuable, biologically active chromenones such as those depicted were synthesized based on a diaryl prolinol ether catalyzed, enantioselective reaction of diketones with α,β-unsaturated aldehydes. In these efficient addition–acetalization cascade reactions, diverse aliphatic and aromatic α,β-unsaturated aldehydes, as well as various diketones, can be successfully applied and the 2-hydroxychromenones can be isolated in good yields and with excellent enantioselectivities.