A Catalyst-Controlled Enantiodivergent Bromolactonization
作者:Yuk-Cheung Chan、Xinyan Wang、Ying-Pong Lam、Jonathan Wong、Ying-Lung Steve Tse、Ying-Yeung Yeung
DOI:10.1021/jacs.1c05680
日期:2021.8.18
enantiodivergent bromolactonization of olefinicacids has been developed. Quinine-derived amino-amides bearing the same chiral core but different achiral aryl substituents were used as the catalysts. Switching the methoxy substituent in the aryl amide system from meta- to ortho-position results in a complete switch in asymmetric induction to afford the desired lactone in good enantioselectivity and yield
Continuous Separation of Racemic 3,5-Dinitrobenzoyl-Amino Acids in a Centrifugal Contact Separator with the Aid of Cinchona-Based Chiral Host Compounds
作者:Andrew J. Hallett、Gerard J. Kwant、Johannes G. de Vries
DOI:10.1002/chem.200800797
日期:2009.2.16
Resolution through revolution: It is possible to extract 3,5‐dinitrobenzoyl‐protected amino acids enantioselectively with the aid of a table‐top centrifugalcontactseparator and a catalytic amount of a chiral host compound based on the Cinchona alkaloids. Enantioselectivities of up to 80 % could be reached in a single pass. This allows the development of a process for the continuous separation of
Strong Detrimental Effect of a Minute Enantiomeric Impurity of a Chiral Selector on the Enantioselectivity Factor
作者:Pavel A. Levkin、Norbert M. Maier、Volker Schurig、Wolfgang Lindner
DOI:10.1002/anie.201002215
日期:2010.10.11
Without a trace? The higher the enantioselectivity of a chiralselector, the more it is sensitive to enantiomericimpurities. Therefore, the enantiomeric purity of a chiralselector affects the enantioseparation factor α (see picture).
A Cation-Directed Enantioselective Sulfur-Mediated Michael/Mannich Three-Component Domino Reaction involving Chalcones as Michael Acceptors
作者:Ran Ding、Bo Zheng、Yan Wang、Yungui Peng
DOI:10.1021/acs.orglett.5b01833
日期:2015.9.4
A new approach has been developed for an asymmetric sulfur-mediated three-component intermolecular Michael/Mannich domino reaction using chalcones as Michael acceptors. This reaction is catalyzed by chiral quaternary ammonium salts derived from modified quinine and provides facile access to complex sulfur-containing compounds with three contiguous stereogenic centers in yields of up to 93%, with 95:5 dr and 95% ee. These compounds were further elaborated to give the equivalent of a chiral aza-Morita-Baylis-Hillman reaction involving chalcones and azetidines bearing four chiral centers.