Primary Amine/CSA Ion Pair: A Powerful Catalytic System for the Asymmetric Enamine Catalysis
作者:Chen Liu、Qiang Zhu、Kuo-Wei Huang、Yixin Lu
DOI:10.1021/ol200747x
日期:2011.5.20
A novel ion pair catalyst containing a chiral counteranion can be readily derived by simply mixing cinchona alkaloid-derived diamine with chiral camphorsulfonic acid (CSA). A mixture of 9-amino(9-deoxy)epi-quinine 8 and (−)-CSA was found to be the best catalyst with matching chirality, enabling the direct amination of α-branched aldehydes to proceed in quantitative yields and with nearly perfect enantioselectivities
Organocatalytic alpha-amination of alpha,alpha-disubstituted aldehydes promoted by 9-amino-(9-deoxy)-epi-quinine is described. alpha-Hydrazino aldehydes bearing a quaternary stereogenic center are obtained in good to excellent yields and enantioselectivities. (C) 2011 Elsevier Ltd. All rights reserved.