Synthesis of Cinchona Urea Polymers and Their Evaluation as Catalyst in the Asymmetric Reactions

Chiral polyureas of cinchona alkaloids were synthesized via repetitive Mizoroki-Heck (MH) coupling reaction. The Pd-catalyzed polycondensation of cinchona urea dimers6and aromatic diiodide7afforded the chiral polyureas (P1-P4). The catalytic activity of the chiral polymers was subsequently investigated. The asymmetric Michael addition of ketoesters to nitroolefins was successfully catalyzed by the polymeric organocatalysts (P1-P4) to give the corresponding Michael adducts with high catalytic activities and excellent enantionselectivities (up to >99% ee). The polymeric catalysts were insoluble in commonly used organic solvents. They were easily recovered and reused several times without any loss of the catalytic activity.