Märkl, Gottfried and Stiegler, Jürgen and Kreitmeier, Peter and Burgemeister, Thomas and Kastner, Fritz and Dove, Stefan (1997) Configurational and conformational isomeric antiaromatic [28]tetraoxaporphyrinoids(4.2.4.2) and aromatic [26]tetraoxaporphyrin(4.2.4.2) dications. A new type of molecular dynamics in macrocyclic systems. HELVETICA CHIMICA ACTA, 80 (1). pp. 14-42. ISSN 0018-019X, 1522-2675
Full text not available from this repository.Abstract
The [28]tetraoxaporphyrinoids(4.2.4.2)6 are synthesized by cyclizing Wittig reaction of (E,E)-5,5'-(buta-1,3-diene-1,4-diyl)bis[furan-2-carbaldehyde] (8) with (E,E)-{(buta-1,3-diene-diyl)bis[(furan-5,2-diyl)methylene]}bis[triphenylphosphonium] dibromide (9) and 3,3'-{[(E)-ethene-1,2-diyl]bis(furan-5,2-diyl)}bis[(E)-prop-2-enal] (22) with (E)-{(ethene-1,2-diyl)bis[(furan-5,2-diyl)methylene]}bis[triphenylphosphonium] dibromide (23). An alternative path to get 6 is the McMurry condensation of 8. Four different configurational isomers of 6 could be isolated and characterized by H-1-NMR spectroscopy. The (Z,EE,Z,EE)-isomer 6a is the first macrocyclic system where the inner and outer protons of the (E,E)-dienediyl bridges exchange by rotation around the adjacent single bonds. In the (Z,EE,E,EE)-isomer 6b, the (E)-ethenediyl bridge is rotationally active, while in the (E,ZE,E,EZ)-isomer 6c and in the (E,EZ,E,EZ)-isomer 6e, the rotation of both (E)-ethenediyl bridges is observed. When in the dynamic systems the rotation of the active (E)-double bonds at temperatures T < -90 degrees is frozen, all configurational isomers of 6 appear to be antiaromatic and paratropic. The oxidation of the [28]tetraoxaporphyrinoids 6c and 6e with DDQ yields the aromatic, diatropic [26]tetraoxaporphyrin(4.2.4.2) dications 21e/21e' both with (E,EZ,E,EZ)-configuration but different fixed conformations. (Z,EE,Z,EE)-Isomer 6;1 is oxidized to give the (Z,EE,Z,EE)-dication 21a, while the oxidation of 6b yields a mixture of 21a and 21e/21e'. The standard formation enthalpies of the obtained and expected [28]tetraoxaporphyrinoids 6 and [26]tetraoxaporphyrin dications 21 have been calculated with the AM1 method, showing good accordance with the experimental results.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | PORPHYCENE |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Organische Chemie |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 24 May 2023 09:08 |
| Last Modified: | 24 May 2023 09:08 |
| URI: | https://pred.uni-regensburg.de/id/eprint/51192 |
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