Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/33406
Title: Development of Enantioselective Synthetic Methods Promoted by Primary Amine-Based Organic Catalysts
Authors: LIU CHEN
Keywords: Primary amine-based chiral catalysts, Michael Addtion, Amination, Aldol reaction
Issue Date: 2-Aug-2011
Source: LIU CHEN (2011-08-02). Development of Enantioselective Synthetic Methods Promoted by Primary Amine-Based Organic Catalysts. ScholarBank@NUS Repository.
Abstract: This thesis studies the development of enantioselective synthetic methods promoted by primary amine-based organic catalysts. Chapter 1 provides a brief historic review of the development of the asymmetric organocatalysis. Especially, the development of asymmetric aminocatalysis via iminium and enamine activation was described. Some selected examples of secondary and primary amine catalysts in this field were illustrated in detailed. Chapter 2 introduces a novel primary amine-based organocatalyst, the combination of 9-amino-9-deoxy-epi-cinchonine and (+)-CSA, for effective conjugated addition via iminium activation of nitro esters to a,b-unsaturated ketones. Such a catalytic system could catalyze the conjugate addition in a highly enantioselective manner, affording the desired adducts in high yields and with up to 99% ee. The Michael adducts are rich in functionality and ready to be converted into useful chiral building blocks. Chapter 3 presents that a mixture of 9-amino(9-deoxy)epi-quinine and (-)-CSA was found to be the best catalyst with matching chirality, enabling the direct amination of a-branched aldehydes to proceed in quantitative yields and with nearly perfect enantioselectivities. A 0.5 mol % catalyst loading was sufficient to catalyze the reaction, and a gram scale enantioselective synthesis of biologically important methyl phenylglycine has been successfully demonstrated. Chapter 4 focuses on the effective aldol reaction of acetone and hydroxyacetone to b,g-unsaturated a-keto ester catalyzed by the combination of 9-amino-9-deoxy-epi-cinchonine and trifluoroacetic acid. The desired adducts containing a chiral tertiary alcohol skeleton could be obtained in high yields and up to 99% ee, and an efficient access to 2-substituted glycerol derivatives was also reported.
URI: http://scholarbank.nus.edu.sg/handle/10635/33406
Appears in Collections:Ph.D Theses (Open)

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