Mechanism of Alcohol Oxidation Mediated by Copper(ll) and Nitroxyl Radicals.
2,2'-Bipyridine-ligated copper complexes, in combination with TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl), are highly effective catalysts for aerobic alcohol oxidation. Considerable uncertainty and debate exist over the mechanism of alcohol oxidation mediated by Cu and TEMPO. Here, we report experi...
| Publicado en: | Journal of the American Chemical Society Vol. 136; no. 34; pp. 12166 - 12174 |
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| Autores principales: | , , , |
| Formato: | Artículo |
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American Chemical Society
8/27/2014
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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=98561103&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 98561103 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: 8/27/2014 vid: 136 iid: 34 pid: 997 pub: American Chemical Society artinfo: ui: 98561103 10.1021/ja5070137 ppf: 12166 ppct: 8 formats: tig: atl: Mechanism of Alcohol Oxidation Mediated by Copper(ll) and Nitroxyl Radicals. aug: au: Ryland, Bradford L. McCann, Scott D. Brunold, Thomas C. Stahl, Shannon S. affil: Department of Chemistry, University of Wisconsin—Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States su: Alcohol oxidation Copper Nitroxyl Radicals (Chemistry) Density functional theory Alkoxides Hydrogen transfer reactions Reactivity (Chemistry) sug: subj: Alcohol oxidation Copper Nitroxyl Radicals (Chemistry) Density functional theory Alkoxides Hydrogen transfer reactions Reactivity (Chemistry) ab: 2,2'-Bipyridine-ligated copper complexes, in combination with TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl), are highly effective catalysts for aerobic alcohol oxidation. Considerable uncertainty and debate exist over the mechanism of alcohol oxidation mediated by Cu and TEMPO. Here, we report experimental and density functional theory (DFT) computational studies that distinguish among numerous previously proposed mechanistic pathways. Oxidation of various classes of radicalprobe substrates shows that long-lived radicals are not formed in the reaction. DFT computational studies support this conclusion. A bimolecular pathway involving hydrogen-atom-transfer from a Cu-alkoxide to a nitroxyl radical is higher in energy than hydrogen transfer from a Cu—alkoxide to a coordinated nitroxyl species. The data presented here reconcile a collection of diverse and seemingly Intramolecular Hydrogen-Atom Transfer (cf. Galactose Oxidase) contradictory experimental and computational data reported previously in the literature. The resulting Oppenauer-like reaction pathway further explains experimental trends in the relative reactivity of different classes of alcohols (benzylic versus aliphatic and primary versus secondary), as well as the different reactivity observed between TEMPO and bicyclic nitroxyls, such as ABNO (ABNO = 9-azabicyclo[3.3.1]nonane N-oxyl). pubtype: Academic Journal doctype: Article src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2014 holdings: @attributes: islocal: N |
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