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
Proline-catalysed asymmetric amination of α,α-disubstituted aldehydes: synthesis of configurationally stable enantioenriched α-aminoaldehydes
作者:Henning Vogt、Sylvia Vanderheiden、Stefan Bräse
DOI:10.1039/b305465a
日期:——
Proline-catalysed amination of α,α-disubstituted racemic aldehydes with azodicarboxylates proceeds smoothly to give configurationally stable scalemic aldehydes and oxazolidinones in up to 86% ee.
Highly Efficient and Practical Pyrrolidine-Camphor-Derived Organocatalysts for the Direct α-Amination of Aldehydes
作者:Pang-Min Liu、Dhananjay R. Magar、Kwunmin Chen
DOI:10.1002/ejoc.201000695
日期:2010.10
for direct α-amination of aldehydes with dialkyl azodicarboxylates to give the desired α-aminated products in high chemical yields (up to 92 %) and with high to excellent levels of stereoselectivity (up to >99 % ee). The reactions proceeded rapidly (within 5 min) with low catalyst loading (5 mol-%) at ambient temperature. Enantioselective aminations of asymmetric α,α-disubstituted aldehydes in the catalytic
Acetals: a new organocatalysis chemotype for one-pot enantioselective α-amination
作者:Ath’enkosi Msutu、Roger Hunter
DOI:10.1016/j.tetlet.2014.02.097
日期:2014.4
Conditions are described for one-pot Bronsted acid and organocatalysed enantioselective alpha-amination of acetals and associated functionalities. Of the organocatalysts screened, proline tetrazole gave the highest ee, while aqueous monochloroacetic acid proved to be the best Bronsted acid activator regarding minimizing racemization and maximizing product yield. The reaction opens up the way for using masked carbonyl functionalities in organocatalysis. (C) 2014 Elsevier Ltd. All rights reserved.
Primary amine catalyzed electrophilic amination of α,α-disubstituted aldehydes
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.