A Torquospecific 1,5-Electrocyclization |
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Authors: | Paul Gesche Franois Klinger Andreas Riesen Thophile Tschamber Margareta Zehnder Jacques Streith |
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Institution: | Paul Gesche,François Klinger,Andreas Riesen,Théophile Tschamber,Margareta Zehnder,Jacques Streith |
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Abstract: | Saponification of homodiazepine 1a and 1b , in the absence of any proton donors, led to the formation of the 6π electron anionic species A which, by virtue of a 1,5-electrocyclization, is in equilibrium with the allylic anion B . This latter tricyclic species is thermodynamically less favoured than its bicyclic isomer A . Nevertheless, B could be trapped by acylation and led tupe- 2 compounds which are the major reaction products. This is due to the fact that B is more nucleophilic and, therefore, much more reactive than A . The transoid topology of the tricyclic products 2 was demonstrated by 1H-NMR and by an X-ray diagram of 2d . The transoid geometry of 2 is a consequence of a torquospecific 1,5-electrocyclization (of A ), which is due to a steric, and possibly even to an electronic factor. |
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