The Circular Dichroism of 5,6-Dimethylidene-2-bicyclo[2.2.n]alky Esters. Chiral Exciton Coupling between Benzoate and Exocyclic s-cis-Butadiene Chromophores
✍ Scribed by Zou Zhichen; Pierre-Alain Carrupt; Pierre Vogel
- Book ID
- 102859440
- Publisher
- John Wiley and Sons
- Year
- 1984
- Tongue
- German
- Weight
- 612 KB
- Volume
- 67
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
Abstract
The optically pure aryl‐substituted 5,6‐dimethylidene‐2‐bicyclo[2.2.1]heptyl benzoates 12–21 were prepared; their UV absorption and CD spectra are reported. The (−)‐(1__S__,2__S__)‐esters 17–21 with carbonyl groups in endo‐position exhibit typical excitonsplit Cotton effects whereas the corresponding (−)‐(1__S__,2__R__)‐esters 12‐16 with carbonyl groups in exo‐position do not present such effects. The chiral exciton coupling between the exocyclic diene and a remote p‐substituted benzoate chromophore can be used for unambiguous assignment of the absolute configuration of 5,6‐dimethylidene‐2‐endo‐bicyclo[2.2.1]heptyl derivatives. The method is applied to establish the absolute configuration of 5,6‐dimethylidene‐2‐exo and ‐2‐endo‐bicyclo[2.2.2.]octyl p‐bromobenzoates (−)‐24 and (−)‐25.