Merz, Andreas and Gromann, Lutz and Karl, Andreas and Burgemeister, T. and Kastner, F. (1996) Conformations and rotational barriers of (Z)-1,2-alpha-naphthostilbene crown ethers and their alkali metal complexes. LIEBIGS ANNALEN-RECUEIL, 1996 (10). pp. 1635-1640. ISSN 0947-3440
Full text not available from this repository.Abstract
The synthesis of 2,3-didehydro[15]crown-5 and -[18]crown-6 derivatives 4a, b with vicinal alpha-naphthyl groups at the double bonds starting from alpha-naphthoin (3) is described. The barriers to rotation of the naphthyl groups were probed by MM2 and by dynamic H-1-NMR spectroscopy. An achiral syn and a chiral anti conformation were experimentally observed at -90 degrees C for the free ligands and at -40 degrees C for the complexes. The experimental Delta G* and the calculated Delta H* values are in fair agreement. The barriers are substantially higher in the alkali metal complexes than in the free ligands. In the presence of racemic and potassium S-(+)-mandelate non-equilibrating ion pairs with 4b were observed by low-temperature H-1-NMR spectroscopy for the anti conformation.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | TRIMETHYLSILYL CYANIDE; NUCLEOPHILIC ACYLATION; ALDEHYDES; UMPOLUNG; REAGENT; calculations, force field; dynamic NMR spectroscopy; chiral conformations; chiral ion pairs |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Organische Chemie |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 22 Jun 2023 09:49 |
| Last Modified: | 22 Jun 2023 09:49 |
| URI: | https://pred.uni-regensburg.de/id/eprint/51447 |
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