Benzoannelated cis,cis,cis,trans-[5.5.5.6]Fenestranes: Syntheses, Base Lability, and Flattened Molecular Structure of Strained Epimers of the all-cis Series

✍ Scribed by Björn Bredenkötter; Ulrich Flörke; Dietmar Kuck

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 272 KB
• Volume: 7
• Category: Article
• ISSN: 0947-6539
• DOI: 10.1002/1521-3765(20010803)7:15<3387::aid-chem3387>3.0.co;2-6

✦ Synopsis

Tribenzofenestranes possessing the strained cis,cis,cis,trans-[5.5.5.6]fenestrane skeleton have been synthesized from cis-2,6-diphenylspiro[cyclohexane-1,2'-indane]-1',3'-diols by twofold cyclodehydration, in striking analogy to the strategy used previously to construct the stereoisomeric all-cis-tribenzo[5.5.5.6]fenestranes from the corresponding trans-diphenylspirodiols. In this manner, both of the parent hydrocarbons, all-cis-tribenzo[5.5.5.6]fenestrane 3 and cis,cis,cis,trans-tribenzo[5.5.5.6]fenestrane 4, have been made accessible from the spirodiketones 5 and 6, respectively. The C6-functionalized derivatives of 4Ðcis,cis,cis,trans-fenestranol 9 and cis,cis,cis,trans-fenestranone 12Ðwere prepared through cis-diphenylspirotriol 8 and cis-diphenyldispiroacetaldiol 11, through direct deprotonation of the ªepimericº benzylic bridgehead C7aÀH bond, which was found to be more acidic than the two CÀH bonds at the benzhydrylic bridgeheads.