Stepwise Cope Rearrangement of Cyclo-biphenalenyl via an Unusual Multicenter Covalent π-Bonded Intermediate.
Abstract: Multicenter covalent a-bonding between ar-conjugated radicals has been recently recognized as a novel and important bonding interaction. The Cope rearrangement of cyclo-biphenalenyl 9 is studied by exploring its potential energy surface with density functional theory (DFT), and it is found...
| Published in: | Journal of the American Chemical Society Vol. 128; no. 22; pp. 7277 - 7287 |
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| Main Authors: | , |
| Format: | Article |
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American Chemical Society
6/7/2006
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| Online Access: | View this record in EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=hlh&AN=21211353&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 21211353 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: 6/7/2006 vid: 128 iid: 22 pid: 997 pub: American Chemical Society artinfo: ui: 21211353 10.1021/ja060427r ppf: 7277 ppct: 10 formats: tig: atl: Stepwise Cope Rearrangement of Cyclo-biphenalenyl via an Unusual Multicenter Covalent π-Bonded Intermediate. aug: au: Jingsong Huang Kertesz, Mikios affil: Department of Chemistry, Georgetown University, 37th and 0 Street, Washington, D.C. su: Cyclic compounds Radicals (Chemistry) Density functionals Chemical bonds Cyclophanes Paramagnetism sug: subj: Cyclic compounds Radicals (Chemistry) Density functionals Chemical bonds Cyclophanes Paramagnetism ab: Abstract: Multicenter covalent a-bonding between ar-conjugated radicals has been recently recognized as a novel and important bonding interaction. The Cope rearrangement of cyclo-biphenalenyl 9 is studied by exploring its potential energy surface with density functional theory (DFT), and it is found that π-bonding plays a critical role in the rearrangement process. Affected by this, the rearrangement of 9 takes place by a stepwise mechanism through an unusual π-intermediate 10, of C symmetry, which can be characterized as a 2×13πr+2×2π system. The π-intermediate has a long inter-phenalenyl distance of R ≈ 2.8 Å, which is shorter than the sum of the van der Waals radii displaying multicenter covalent π-bonding between the two phenalenyl units. The energy of the π-intermediate 10 is higher than that of the σ-bonded reactant 9 by ~2 kcal/mol according to the employed spin-restricted DFT. NMR chemical shift calculations support the σ-bonded 9 as the global minimum. The calculated activation barrier of ~6 kcal/mol for the Cope rearrangement is consistent with the stepwise mechanism. A covalent σ-bonding effect in the π-intermediate 10 is demonstrated indirectly by the shortening of inter-naphthalene distance of the dianion and dication of the cyclophane 14 compared to that of its neutral counterpart. The unusual π-bonded structure with a long inter-phenalenyl distance becomes the most stable structure for the ethano-bridged derivative 13, which should have observable paramagnetism according to the calculated paramagnetic susceptibility. pubtype: Academic Journal doctype: Article src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2006 holdings: @attributes: islocal: N |
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