Asymmetric Michael Additions with Polymer-Supported Pyrrolidine Derivatives

Significance

Polymer-immobilized pyrrolidine-based chiral ionic liquids (5a-c) were readily prepared from N-Boc-l-proline in four steps. Michael addition of cyclohexanone to nitrostyrene with catalysts 5 was carried out in various polar and nonpolar solvents to give the corresponding Michael adducts in 25-95% yield with 98-99% ee and 98-99% syn selectivity. Under solvent-free conditions, 5a catalyzed the Michael addition of various ketones and isobutylaldehyde in 69-98% yield with 46-99% ee and 75-99% syn selectivity (22 examples). The catalyst was recovered by simple filtration and reused for eight consecutive runs without loss of catalytic activity and enantio­selectivity.