Catalytic Enantioselective Synthesis of Flavanones and Chromanones

The enantioselective synthesis of flavanones and chromanones is described. Bifunctional thiourea catalysts promote an asymmetric oxo-conjugate addition to a β-ketoester alkylidene in high yields with excellent enantioselectivity (80−94% ee) for aryl and alkyl substrates. Decarboxylation of the β-ketoester proceeds smoothly in a one-pot procedure to afford the enantioenriched flavanones and chromanones.