Issue 5, 2017

Electronic and steric effects on the three-fold Scholl-type cycloheptatriene ring formation around a tribenzotriquinacene core

Abstract

Systematic studies on the role of substituents in the bay-bridging cycloheptatriene ring formation around the tribenzotriquinacene (TBTQ) core via the non-typical Scholl reaction were carried out. The electronic effect of the substituents was found to be the predominant factor that controls the ease of the cyclization reaction, while the steric effect of methoxy groups in the bay regions of the TBTQ core appears to be also significant but less important. In several cases with insufficient electronic activation and/or unfavorable steric restriction, single bay-bridging occurred with or without concomitant bridgehead hydroxylation. Alternatively, an unprecedented ring opening/closure of the TBTQ skeleton by electrophilic ipso-attack was found to intervene in other cases. Starting from the electronically and sterically most favorable precursor, a 1,4,8-tris-(2,3,4-trimethoxyphenyl)-TBTQ derivative, a new wizard-hat-shaped, three-fold bay-bridged TBTQ nanographene core bearing nine methoxy groups at the molecular periphery was synthesized with high efficiency.

Graphical abstract: Electronic and steric effects on the three-fold Scholl-type cycloheptatriene ring formation around a tribenzotriquinacene core

Supplementary files

Article information

Article type
Research Article
Submitted
16 Feb 2017
Accepted
14 Mar 2017
First published
16 Mar 2017

Org. Chem. Front., 2017,4, 817-822

Electronic and steric effects on the three-fold Scholl-type cycloheptatriene ring formation around a tribenzotriquinacene core

H. Ip, H. Chow and D. Kuck, Org. Chem. Front., 2017, 4, 817 DOI: 10.1039/C7QO00132K

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