Highly Enantioselective Michael Addition of Cyclic 1,3-Dicarbonyl Compounds to β,γ-Unsaturated α-Keto Esters

A highly enantioselective Michael addition of cyclic 1,3-dicarbonyl compounds to beta,gamma-unsaturated a-keto esters catalyzed by amino acid-derived thiourea-tertiary-amine catalysts is presented. Using 5 mol% of a novel tyrosine-derived thiourea catalyst, a series of chiral coumarin derivatives were obtained in excellent yields (up to 99%) and with up to 96% ee under very mild conditions within a short reaction time.