Märkl, Gottfried and Sauer, Heinrich and Stiegler, Jürgen and Kreitmeier, Peter and Burgemeister, Thomas (1998) Tetraepoxy[22]annulene(2.2.2.0): a tetraepoxy-bridged neutral aromatic [22]annulene of a new type. HELVETICA CHIMICA ACTA, 81 (5-8). pp. 1077-1087. ISSN 0018-019X, 1522-2675
Full text not available from this repository.Abstract
We describe the synthesis of tetraepoxy[22]annulene(2.2.2.0) 4, the first aromatic annulene of type B by a cyclizing twofold Wittig reaction of 2,2'-bifuran-5,5'-dicarbaldehyde (5) and the bis[phosphonium] salt 8. The configuration of 4, mainly determined by NMR spectroscopy is (Z,E,Z). According to the UV/VIS spectrum and the H-1-NMR data, the electronic situation in 4 is quite different from that of tetraepoxy[22]annulene(3.0.3.0) 2 and tetraepoxy[22]annulene(2.1.2.1) 3. According to variable-temperature H-1-NMR spectroscopy, 4 is a highly dynamic system, where the (E)-double bond rotates around the adjacent sigma-bonds. At ca. -130 degrees, this dynamic process is frozen, and 4 appears as a diatropic aromatic system; the free activation energy of the rotation Delta G double dagger is ca. 5.75 kcal/mol.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | DICATION; PORPHYRIN |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Organische Chemie |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 01 Mar 2023 07:59 |
| Last Modified: | 01 Mar 2023 07:59 |
| URI: | https://pred.uni-regensburg.de/id/eprint/50209 |
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