Design and synthesis of chiral hyperbranched polymers containing cinchona squaramide moieties and their catalytic activity in the asymmetric Michael addition reaction

Abstract

Chiral hyperbranched polymers (HBP) containing cinchona alkaloids were synthesized using a Mizoroki–Heck (MH) coupling polymerization reaction between a cinchona squaramide dimer and tri- or tetra-substituted aromatic iodides. This is a new type of polymeric chiral organocatalyst. We found that the as-obtained chiral HBPs show excellent catalytic activity in the asymmetric Michael reaction. Almost perfect enantioselectivity (>99% ee) was achieved in the reaction of β-ketoester and trans-β-nitrostyrene. The three-dimensional network structure of the chiral HBPs is structurally robust and can be reused for further reaction without any loss in their catalytic activity.