title: Primary amine/CSA ion pair: a powerful catalytic system for the asymmetric enamine catalysis.
abstract: 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. A 0.5 mol % catalyst loading was sufficient to catalyze the reaction, and a gram scale enantioselective synthesis of biologically important α-methyl phenylglycine has been successfully demonstrated.
authors.affiliation: Department of Chemistry & Medicinal Chemistry Program, Life Sciences Institute, National University of Singapore, Singapore.
authors.forename: Chen
authors.initials: C
authors.lastname: Liu
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhu
authors.forename: Kuo-Wei
authors.initials: KW
authors.lastname: Huang
authors.forename: Yixin
authors.initials: Y
authors.lastname: Lu
mesh_terms: D000447:Aldehydes / Q000138:chemical synthesis / Q000737:chemistry*; D000588:Amines / Q000737:chemistry*; D002164:Camphor / Q000031:analogs & derivatives* / Q000737:chemistry; D002384:Catalysis; D002930:Cinchona Alkaloids / Q000737:chemistry*; D015394:Molecular Structure; D013237:Stereoisomerism
chemical_list: D000447:Aldehydes; D000588:Amines; D002930:Cinchona Alkaloids; D002164:Camphor; C006881:10-camphorsulfonic acid