A Systematic Investigation of Quaternary Ammonium Ions as Asymmetric Phase-Transfer Catalysts. Application of Quantitative Structure Activity/Selectivity Relationships

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• 作者：Scott E. Denmark ; Nathan D. Gould ; Larry M. Wolf
• 刊名：Journal of Organic Chemistry
• 出版年：2011
• 出版时间：June 3, 2011
• 年：2011
• 卷：76
• 期：11
• 页码：4337-4357
• 全文大小：1501K
• 年卷期：v.76,no.11(June 3, 2011)
• ISSN：1520-6904

文摘

Although the synthetic utility of asymmetric phase-transfer catalysis continues to expand, the number of proven catalyst types and design criteria remains limited. At the origin of this scarcity is a lack in understanding of how catalyst structural features affect the rate and enantioselectivity of phase transfer catalyzed reactions. Described in this paper is the development of quantitative structure鈭抋ctivity relationships (QSAR) and 鈭抯electivity relationships (QSSR) for the alkylation of a protected glycine imine with libraries of quaternary ammonium ion catalysts. Catalyst descriptors including ammonium ion accessibility, interfacial adsorption affinity, and partition coefficient were found to correlate meaningfully with catalyst activity. The physical nature of the descriptors was rationalized through differing contributions of the interfacial and extraction mechanisms to the reaction under study. The variation in the observed enantioselectivity was rationalized employing a comparative molecular field analysis (CoMFA) using both the steric and electrostatic fields of the catalysts. A qualitative analysis of the developed model reveals preferred regions for catalyst binding to afford both configurations of the alkylated product.