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Synthesis of Polycyclic Spirocarbocycles via Acid-Promoted Ring-Contraction/Dearomative Ring-Closure Cascade of Oxapropellanes

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journal contribution
posted on 09.09.2019, 14:33 by Naoki Ogawa, Yousuke Yamaoka, Hiroshi Takikawa, Kiyosei Takasu
We report herein the development of an acid-promoted rearrangement of oxa[4.3.2]­propellanes to afford polyaromatic-fused spiro[4.5]­carbocycles. DFT calculations suggest that the reaction pathway involves generation of a cyclobutyl cation, ring contraction to the cyclopropylcarbinyl cation, and dearomative ring closure by an internal 2-naphthol moiety. The resulting spirocarbocycles are synthetically valuable, as they could be transformed into two different polycyclic aromatic hydrocarbons via skeletal rearrangement. Syntheses of optically pure spirocarbocycles via a central-to-axial-to-central chirality transfer are also described.

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