Origins of Enantioselectivity in Asymmetric Radical Additions to Octahedral Chiral-at-Rhodium Enolates: A Computational Study.
The origin of asymmetric induction in the additions of carbon- and nitrogen-centered radicals to octahedral centrochiral rhodium enolates has been investigated with density functional theory calculations. Computed free energies of activation reproduce the preference for the experimentally observed m...
| Publicado en: | Journal of the American Chemical Society Vol. 139; no. 49; pp. 17902 - 17908 |
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| Autores principales: | , , , |
| Formato: | Artículo |
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American Chemical Society
12/13/2017
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| Acceso en línea: | Ver este registro en EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=hlh&AN=126761858&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 126761858 longDbName: Humanities International Complete uiTag: AN controlInfo: bkinfo: jinfo: jid: 00027863 ACS jtl: Journal of the American Chemical Society issn: 00027863 maglogo: N pubinfo: dt: 12/13/2017 vid: 139 iid: 49 pid: 997 pub: American Chemical Society artinfo: ui: 126761858 10.1021/jacs.7b08650 ppf: 17902 ppct: 6 formats: tig: atl: Origins of Enantioselectivity in Asymmetric Radical Additions to Octahedral Chiral-at-Rhodium Enolates: A Computational Study. aug: au: Shuming Chen Xiaoqiang Huang Meggers, Eric Houk, K. N. affil: Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Strasse 4, 35043 Marburg, Germany su: Rhodium compounds Enantioselective catalysis Addition reactions Asymmetric synthesis Enolates Density functional theory sug: subj: Rhodium compounds Enantioselective catalysis Addition reactions Asymmetric synthesis Enolates Density functional theory ab: The origin of asymmetric induction in the additions of carbon- and nitrogen-centered radicals to octahedral centrochiral rhodium enolates has been investigated with density functional theory calculations. Computed free energies of activation reproduce the preference for the experimentally observed major enantiomer. Good levels of enantioselectivity are maintained upon replacement of the bulky tert-butyl substituents on the ligands with methyl groups. Distortioninteraction analysis indicates that for both carbon- and nitrogen-centered radicals, which have relatively early and late transition states, respectively, the difference in the distortion energies controls the enantioselectivity. In the enolate derived from the Λ-configured catalyst, the tert-butyl group that shields the si face of the substrate plays the most sterically significant steric role by directly hindering access to the enolate double bond. Exploration of the effect of the N substituent size and shape on the imidazole substrate shows that compared to N-Me, N-iPr and N-Ph variants, the N-o-tolyl variant of the rhodium enolate results in the most substantial improvement in stereodiscrimination, a finding that is in agreement with experimental ee values. pubtype: Academic Journal doctype: Article src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2017 holdings: @attributes: islocal: N |
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