Versuche zur Synthese von Calicen aus trisubstituierten Cyclopropanen und Cyclopentenon
✍ Scribed by Andreas Weber; Roberto Galli; Gabriele Sabbioni; Urs Stämpfli; Stefan Walther; Markus Neuenschwander
- Publisher
- John Wiley and Sons
- Year
- 1989
- Tongue
- German
- Weight
- 645 KB
- Volume
- 72
- Category
- Article
- ISSN
- 0018-019X
No coin nor oath required. For personal study only.
✦ Synopsis
Attempted Synthesis of Calicene from Trisubstitued Cyclopropanes and Cyclopentenone
The Li carbenoids 4, prepared by treatment of substituted 1,l-dihalocyclopropanes with BuLi, are reacted with cyclopent-2-enone under thermodynamic and kinetic control (Scheme 1). In general, the latter procedure gives better yields of cyclopropylcyclopentenols 5a+, but the reaction seems to be controlled mainly by the steric and electronic properties of the substituent Y. So, with 4b and 4e, the main reaction is the attack of the carbenoid at C(1) of cyclopent-2-enone, while 4a ( I ' = PhS) predominantly deprotonates the ketone (Scheme 4 ) . Whereas 5d and 5e can easily be converted to the dihydrocalicenes 6d and 6e (Scheme 6 ) . the attempted elimination of H 2 0 from 5a -E leads to the rearranged products 1 3 1 6 due to the opening of the cyclopropane ring (Scheme 5 ) . Finally, the generation of the parent compound 2 from the silylated precursor 6d is attempted: treatment with MeO-gives the addition products 18A/18B, while the reaction with Br2 provides 19 by a bromination/dehydrobromination sequence (Scheme 7).
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Teil der Diplomarbeit [3].