Polymer, Vol.80, 115-122, 2015
Fabrication of optically active microparticles constructed by helical polymer/quinine and their application to asymmetric Michael addition
This article reports a novel category of optically active polymer microparticles combining helical substituted polyacetylene and quinine moieties. The microparticles were prepared through click reaction in aqueous system with the aid of stabilizer. The polymer chains constituting the microparticles adopted helical conformations of predominantly one-handed screw sense, according to circular dichroism and UV-vis spectroscopy measurements. The quinine pendants were grafted on the helical polymer chains and afforded the microparticles with catalytic ability for heterogeneous asymmetric Michael addition, in which a high product yield up to 86% and satisfactory enantioselectivity (83% ee) were obtained. An intriguing synergistic effect occurred in the asymmetric catalysis between the helical macromolecular frameworks and pendent quinine moieties. The reusability of the microparticles was further demonstrated. The present study not only provides a new strategy for manufacturing helical polymer-immobilized chiral catalysts, but also opens up opportunities for developing novel macromolecular catalysts and even advanced functional chiral materials. (C) 2015 Elsevier Ltd. All rights reserved.