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Tandem Oxidative Ring Expansion for Synthesis of Dibenzocyclooctaphenanthrenes

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journal contribution
posted on 18.06.2020, 19:07 by Lu Yang, Hidenori Matsuyama, Sheng Zhang, Masahiro Terada, Tienan Jin
A novel tandem single-electron oxidative ring expansion reaction has been developed for the construction of the saddle-shaped polycyclic arenes fused with cyclooctatetraene, that is, dibenzo­[3,4:7,8]­cyclo­octa­[1,2-l]­phenanthrenes (dbCOTPs). The combination of Cu­(OTf)2 catalyst with DDQ triggered the selective oxidation of o-biphenyl-tethered methylenecirculenes fused with a seven-membered ring, giving rise to the formation of the corresponding eight-membered ring fused dbCOTPs. The present tandem ring expansion of a seven- to an eight-membered ring takes place via the selective single-electron oxidation of the benzylidene moiety, intramolecular spirocyclization, and 1,2-aryl migration sequence.