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Title: Guanidine-catalyzed asymmetric Strecker reaction: modes of activation and origin of stereoselectivity
Authors: Xue, Hansong
Tan, Choon-Hong
Wong, Ming Wah
Keywords: Organocatalysis
Strecker Reaction
Issue Date: 2016
Source: Xue, H., Tan, C.-H., & Wong, M. W. (2016). Guanidine-catalyzed asymmetric Strecker reaction: modes of activation and origin of stereoselectivity. Canadian Journal of Chemistry, 94(12), 1099-1108.
Series/Report no.: Canadian Journal of Chemistry
Abstract: Density functional theory calculations were employed to study the catalytic mechanism, modes of activation, and origin of enantioselectivity of guanidine-catalyzed asymmetric Strecker reaction of N-benzhydryl imine with hydrogen cyanide. Two types of bifunctional activation mode were identified, namely conventional bifunctional Brønsted acid activation and unconventional bifunctional Brønsted–Lewis acid activation. The lowest-energy transition states correspond to the conventional bifunctional mode of activation. The calculated enantiomeric excess, based on eight lowest-energy C–C bond forming transition states, is in good accord with observed enantioselectivity. NCI (noncovalent interaction) analysis of the key transition states reveals extensive noncovalent interactions, including aromatic interactions and hydrogen bonds, between the guanidinium catalyst and substrates. Multiple aryl–aryl interactions between the phenyl groups of guanidine catalyst and the phenyl rings of N-benzhydryl imine are the key stabilizations in the most stable (R)-inducing transition state. Differential attractive aryl–aryl stabilization is the major factor for stereoinduction.
ISSN: 0008-4042
DOI: 10.1139/cjc-2016-0307
Rights: © 2016 The author(s), published by NRC Research Press. This is the author created version of a work that has been peer reviewed and accepted for publication in Canadian Journal of Chemistry, published by NRC Research Press on behalf of the author(s). It incorporates referee’s comments but changes resulting from the publishing process, such as copyediting, structural formatting, may not be reflected in this document.  The published version is available at: [].
Fulltext Permission: open
Fulltext Availability: With Fulltext
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