Loncar-Tomaskovic, L. and Mintas, M. and Trotsch, T. and Mannschreck, Albrecht (1997) 2H-chromenes: Synthesis, separation of enantiomers, circular dichroism and thermal racemization. ENANTIOMER, 2 (6). pp. 459-471. ISSN 1024-2430
Full text not available from this repository.Abstract
The novel 2H-chromenes 1-3 have been synthesized by reduction of the appropriate lactones with diisobutylaluminium hydride and subsequent reaction of the resulting lactols with the corresponding alcohols. The preparation of 4-'7 was achieved from suitably substituted benzopyrylium salts and corresponding alcohols, while 8-13 were obtained by heating of appropriate hemiacetals with corresponding alcohols. The preparative separation or enrichment of enantiomers of 1-13 was accomplished by enantioselective Liquid chromatography on triacetyl- or tribenzoylcellulose. The relative configuration of 1-3 was deduced by comparison of the circular dichroism spectra of their enantiomers. The barriers for the interconversion of enantiomers were determined by thermal racemization. Gibbs energies of activation Delta G(not equal) for reversible cleavage of the C(sp(3))-O bond in 1-13 have been found in the range of 101-134 kJ/mol and are rationalized qualitatively by steric and electronic effects in the transition state.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | CHIROPTICAL DETECTION; BARRIERS; HPLC; chiral 2H-chromenes; enantiomer separation; enantioselective liquid chromatography; circular dichroism; relative configuration; barriers to racemization |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Organische Chemie > Alumni or Retired Professors > Prof.Dr. Mannschreck |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 24 May 2023 09:04 |
| Last Modified: | 24 May 2023 09:04 |
| URI: | https://pred.uni-regensburg.de/id/eprint/51149 |
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