Secondary Orbital Eftect in the Electrocyclic Ring Closure of 7-Azahepta-1,2,4,6-tetraene—A CASSCF Molecular Orbital Study.
Results of (10,9)CASSCF/6-31G* and B3LYP/6-31G* level calculations on the potential surface for the electrocyclic ring closure of E-7-azahepta-1,2,4,6-tetraene 3 to 1-aza-6-methylidenecyclohexa-2,4-diene (4) are reported, as well as parallel calculations on the electrocyclizations of hepta-1,2,4,6-t...
| Publicado en: | Journal of the American Chemical Society Vol. 130; no. 21; pp. 6740 - 6749 |
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| Autores principales: | , , |
| Formato: | Artículo |
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American Chemical Society
5/28/2008
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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=32574855&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 32574855 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: 5/28/2008 vid: 130 iid: 21 pid: 997 pub: American Chemical Society artinfo: ui: 32574855 10.1021/ja074402j ppf: 6740 ppct: 9 formats: tig: atl: Secondary Orbital Eftect in the Electrocyclic Ring Closure of 7-Azahepta-1,2,4,6-tetraene—A CASSCF Molecular Orbital Study. aug: au: Duncan, James A. Calkins, David E. G. Chavarha, Mariya affil: Department of Chemistry, Lewis & Clark College, Portland, Oregon 97219-7899 su: Pericyclic reactions Cyclopolymerization Molecular orbitals Density functionals Magnitude estimation Nitrogen Vector analysis Linear free energy relationship Rotational motion sug: subj: Pericyclic reactions Cyclopolymerization Molecular orbitals Density functionals Magnitude estimation Nitrogen Vector analysis Linear free energy relationship Rotational motion ab: Results of (10,9)CASSCF/6-31G* and B3LYP/6-31G* level calculations on the potential surface for the electrocyclic ring closure of E-7-azahepta-1,2,4,6-tetraene 3 to 1-aza-6-methylidenecyclohexa-2,4-diene (4) are reported, as well as parallel calculations on the electrocyclizations of hepta-1,2,4,6-tetraene 5, hexa-1,3,5-triene 7, Z and E-1-aza-1,3,5-hexatrienes 9 and 10, and Z-7-azahepta-1,2,4,6-tetraene 12 for purposes of careful comparison. The 3 → 4 rearrangement has been studied computationally with density functional theory (DFT) by others, leading to disagreement over whether it is pseudopericyclic (de Lera, A. R.; Alvarez, R.; Lecea, B.; Torrado, A- CossIo, F. P. Angew. Chem., mt. Ed. 2001, 40, 557-561; de Lera, A. R.; Cosslo, F. P. Angew. Chem., mt. Ed. 2002, 41, 1150-1152) or pericyclic (RodrIguez-Otero, J.; Cabaleiro-Lago, E. Angew. Chem., mt. Ed. 2002, 41, 1147-1150). In accordance with disrotatory motion, the normal mode vectors for TS calculated at the (10,9)CASSCF/6-31G* level show a greater magnitude of rotation of the N1-H group relative to the N1-C2 bond being formed than in TS calculated at the B3LYP/6-31G* level. Furthermore, comparison of orbital correlation diagiams constructed entirely from localized complete active space (CAS) molecular orbitals (MOs) for the electrocyclizations of 3, 5, 7, 9, and 10 suggest that it is the highest occupied delocalized π-MO of 3 that is primarily responsible for a-bond formation in 4, not the terminal allenyl π-bond MO. However, there does appear to be a special secondary orbital effect role for the nitrogen lone-pair and hence the process is likely neither purely pericyclic nor pseudopericyclic. pubtype: Academic Journal doctype: Article src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2008 holdings: @attributes: islocal: N |
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