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Hydrogen-Bond-Enabled Dynamic Kinetic Resolution of Axially Chiral Amides Mediated by a Chiral Counterion.

ABSTRACT: Non-biaryl atropisomers are valuable in medicine, materials, and catalysis, but their enantioselective synthesis remains a challenge. Herein, a counterion-mediated O-alkylation method for the generation of atropisomeric amides with an er up to 99:1 is outlined. This dynamic kinetic resolution is enabled by the observation that the rate of racemization of atropisomeric naphthamides is significantly increased by the presence of an intramolecular O-H???NCO hydrogen bond. Upon O-alkylation of the H-bond donor, the barrier to rotation is significantly increased. Quantum calculations demonstrate that the intramolecular H-bond reduces the rotational barrier about the aryl-amide bond, stabilizing the planar transition state for racemization by approximately 40?kJ?mol-1 , thereby facilitating the observed dynamic kinetic resolution.

SUBMITTER: Fugard AJ

PROVIDER: S-EPMC6492105 | biostudies-literature | 2019 Feb

REPOSITORIES: biostudies-literature

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Hydrogen-Bond-Enabled Dynamic Kinetic Resolution of Axially Chiral Amides Mediated by a Chiral Counterion.

Fugard Alison J AJ Lahdenperä Antti S K ASK Tan Jaqueline S J JSJ Mekareeya Aroonroj A Paton Robert S RS Smith Martin D MD

Angewandte Chemie (International ed. in English) 20190206 9

Non-biaryl atropisomers are valuable in medicine, materials, and catalysis, but their enantioselective synthesis remains a challenge. Herein, a counterion-mediated O-alkylation method for the generation of atropisomeric amides with an er up to 99:1 is outlined. This dynamic kinetic resolution is enabled by the observation that the rate of racemization of atropisomeric naphthamides is significantly increased by the presence of an intramolecular O-H⋅⋅⋅NCO hydrogen bond. Upon O-alkylation of the H- ...[more]

PMID: 30644159

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