Optically active helical polymers with pendent thiourea groups: Chiral organocatalyst for asymmetric michael addition reaction |
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Authors: | Haiyang Zhang Wantai Yang Jianping Deng |
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Institution: | 1. State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing, China;2. College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing, China |
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Abstract: | This article reports a novel category of helical substituted polyacetylenes bearing pendant thiourea groups and showing remarkable asymmetric catalysis ability. Thiourea‐based monomer and another chiral monomer underwent copolymerization, affording copolymers with considerable optical activity. The copolymers were used as chiral organocatalyst to homogeneously catalyze the asymmetric Michael addition of diethyl malonate to trans‐β‐nitrostyrene. During catalysis, a synergetic effect occurred between the pendant thiourea moieties and the helical structures in the polymer backbones. The enantioselectivity of the reaction was governed by the thiourea moieties. Meanwhile, the concaves along the helices provided specific domains where the substrates and catalytic groups were packed together, leading to a remarkable enhancement of product yield and enantioselectivity. Product with high yield (85%) and satisfactory ee (up to 72%) can be obtained. The present helical polymers open up new opportunities for developing macromolecules as mimetic enzymes catalyzing asymmetric reactions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1816–1823 |
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Keywords: | asymmetric catalysis catalysts chiral copolymerization helical polymer |
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