Remarkable Enhancement of the Enantioselectivity of an Organocatalyzed Asymmetric Henry Reaction Assisted by Helical Poly(phenylacetylene)s Bearing Cinchona Alkaloid Pendants via an Amide Linkage

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• 作者：Zhenglin Tang ; Hiroki Iida ; Hai-Yu Hu ; Eiji Yashima
• 刊名：ACS Macro Letters
• 出版年：2012
• 出版时间：February 21, 2012
• 年：2012
• 卷：1
• 期：2
• 页码：261-265
• 全文大小：322K
• 年卷期：v.1,no.2(February 21, 2012)
• ISSN：2161-1653

文摘

A series of novel helical poly(phenylacetylene)s bearing amino-functionalized cinchona alkaloid pendant groups connecting to the phenyl rings through an amide linkage were prepared by the polymerization of the corresponding phenylacetylenes using a rhodium catalyst. All of the polymers formed a preferred-handed helical conformation biased by the optically active pendants, resulting in the induced circular dichroism in their 蟺-conjugated polymer backbone regions. The optically active helical polymers efficiently catalyzed the asymmetric Henry reaction of benzaldehydes with nitromethane, giving optically active products up to 94% enantiomeric excess (ee) when the poly(phenylacetylene) bearing an amino-functionalized quinine pendant group was used as the polymeric organocatalyst; the enantioselectivity was remarkably higher than those catalyzed by the corresponding nonhelical poly(phenylacetylene) (18% ee) and the monomer (28% ee).