Construction of spirocyclic oxindole derivatives by copper-catalyzed enantioselective Michael/hemiketalization in aqueous media

An asymmetric Michael/hemiketalization reaction between isatin-derived β,γ-unsaturated α-ketoesters and 4-hydroxycoumarins was developed in aqueous media. A series of chiral spirooxindole derivatives with an all-carbon quaternary stereogenic center were obtained in high yields (up to 93%) and excellent enantioselectivities (up to 98%).