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 β,γ-unsaturated α-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.