Chiral phosphine-squaramide-catalyzed Morita-Baylis-Hillman reaction: enantioselective synthesis of 3-hydroxy-2-oxindoles

Phosphine-squaramide derivatives were developed to catalyze the enantioselective Morita-Baylis-Hillman reaction of acrylates with isatins to construct 3-hydroxy-2-oxindoles with quaternary stereocenters. In the presence of 2 mol% H-bonding catalyst 3e, the desired products were achieved in high yields and good-to-excellent enantioselectivities (up to 95% ee).