A Polystyrene-Supported Phase-Transfer Catalyst for Asymmetric Michael Addition of Glycine-Derived Imines to α, β-Unsaturated Ketones

A 2-oxopyrimidinium salt was immobilized onto a polystyrene-derived polymer to generate a heterogeneous catalyst that effectively promoted the asymmetric Michael addition of glycine-derived imines to alpha, beta-unsaturated ketones. The reactions proceeded smoothly to afford the desired adducts, (S)-tert-butyl 2-[(diarylmethylidene)amino]-5-oxoalkanoates, in high yields and with high enantioselectivities (up to 92% ee). The polymer catalyst could be recovered and reused at least five times without significant loss of activity or selectivity.