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Selection between Diastereomeric Kinetic vs Thermodynamic Carbonyl Binding Modes Enables Enantioselective Iridium-Catalyzed anti-(α-Aryl)allylation of Aqueous Fluoral Hydrate and Difluoroacetaldehyde Ethyl Hemiacetal

Author:
Cabrera, James M., Tauber, Johannes, Zhang, Wandi, Xiang, Ming, Krische, Michael J.
Source:
Journal of the American Chemical Society 2018 v.140 no.30 pp. 9392-9395
ISSN:
1520-5126
Subject:
Lewis acids, acetates, aldehydes, allylation, binding sites, enantioselectivity, thermodynamics
Abstract:
Enantioselectivity increases with increasing carbonyl electrophilicity in 2-propanol-mediated reductive couplings of aldehydes with branched aryl-substituted allylic acetates to form products of carbonyl anti-(α-aryl)allylation. This unusual phenomenon is caused by aldehyde coordination to diastereomeric kinetic vs thermodynamic carbonyl binding sites that deliver enantiomeric products. Exploiting this effect, anti-diastereo- and enantioselective (α-aryl)allylations of fluoral hydrate and difluoroacetaldehyde ethyl hemiacetal were developed.
Agid:
6079158