A Combined Theoretical and Experimental Study of Efficient and Fast Titanocene-Catalyzed 3-exo Cyclizations.
The mechanism of titanocene mediated 3-exo cyclizations was investigated by a combined theoretical and experimental study. A gradient corrected density functional theory (DFT) method has been scaled against titanocene dichloride, the parent butenyl radical, and in bond dissociation energy (BDE) calc...
| Publicado en: | Journal of the American Chemical Society Vol. 127; no. 19; pp. 7071 - 7078 |
|---|---|
| Autores principales: | , , , , |
| Formato: | Artículo |
| Publicado: |
American Chemical Society
5/18/2005
|
| Materias: | |
| 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=17105670&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 17105670 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: 5/18/2005 vid: 127 iid: 19 pid: 997 pub: American Chemical Society artinfo: ui: 17105670 10.1021/ja050268w ppf: 7071 ppct: 7 formats: tig: atl: A Combined Theoretical and Experimental Study of Efficient and Fast Titanocene-Catalyzed 3-exo Cyclizations. aug: au: Friedrich, Joachim Dolg, Michael Gansäuer, Andreas Geich-Gimbel, Daniel Lauterbach, Thorsten affil: Institut für Theoretische Chemie der Universität zu Köln, Greinstrasse 4, 50939 Köln, Germany. Kekulé-Institut für Organische Chemie und Biochemie der Universität Bonn, Gerhard Domagk Strasse 1, 53121 Bonn, Germany. su: Density functionals Cyclopropane Cycloalkanes Thermodynamics Physical & theoretical chemistry Propane sug: subj: Density functionals Cyclopropane Cycloalkanes Thermodynamics Physical & theoretical chemistry Propane ab: The mechanism of titanocene mediated 3-exo cyclizations was investigated by a combined theoretical and experimental study. A gradient corrected density functional theory (DFT) method has been scaled against titanocene dichloride, the parent butenyl radical, and in bond dissociation energy (BDE) calculations. The BP86 method using density fitting, and a basis set of triple-© quality emerged as a highly reliable tool for studying titanocene mediated radical reactions. The computational results revealed important kinetic and thermodynamic features of cyclopropane formation. Surprisingly, the β-titanoxy radicals, the first intermediates of our investigations, were demonstrated to possess essentially the same thermodynamic stabilization as the corresponding alkyl radicals by comparison of the calculated BDEs. In contrast to suggestions for samarium mediated reactions, the cyclization was shown to be thermodynamically favorable in agreement with earlier kinetic studies. It was established that stereoselectivity of the cyclization is governed by the stability of the intermediates and thus the trans disubstituted products are formed preferentially. The observed ratios of products are in good to excellent agreement with the OFT results. By a combination of computational and experimental results, it was also shown that for the completion of the overall cyclopropane formation the efficiency of the trapping of the cyclopropylcarbinyl radicals is decisive. pubtype: Academic Journal doctype: Article src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2005 holdings: @attributes: islocal: N |
|---|