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Issue 21, 2015
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Synthesis and properties of unsymmetrical azatrioxa[8]circulenes

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Abstract

Insights to the subtle reactivity patterns of hydroxy-substituted carbazoles allows the precise synthesis of unsymmetrical azatrioxa[8]circulenes by the reaction of N-benzyl-2,7-di-tert-butyl-3,6-dihydroxycarbazole with two different 1,4-benzoquinones in the presence of an oxidant (chloranil) and a Lewis acid (BF3OEt2). The unique synthetic control obtained originates from the selectivity obtained upon reacting N-benzyl-2,7-di-tert-butyl-3,6-dihydroxycarbazole with an electron-rich benzoquinone to give first the C–C bond formation and then subsequently the dibenzofuran formation with high regioselectivity. Herein the first synthesis of unsymmetrical antiaromatic azatrioxa[8]circulenes and the full characterization using NMR spectroscopy, optical spectroscopy, electrochemistry, computational techniques and single crystal X-ray crystallography is reported. The controlled stepwise condensation of N-benzyl-2,7-di-tert-butyl-3,6-dihydroxycarbazole with two different 1,4-benzoquinones gives selectively the unsymmetrical azatrioxa[8]circulenes.

Graphical abstract: Synthesis and properties of unsymmetrical azatrioxa[8]circulenes

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Supplementary files

Article information


Submitted
06 Apr 2015
Accepted
21 Apr 2015
First published
30 Apr 2015

This article is Open Access

Org. Biomol. Chem., 2015,13, 5937-5943
Article type
Paper
Author version available

Synthesis and properties of unsymmetrical azatrioxa[8]circulenes

M. Plesner, T. Hensel, B. E. Nielsen, F. S. Kamounah, T. Brock-Nannestad, C. B. Nielsen, C. G. Tortzen, O. Hammerich and M. Pittelkow, Org. Biomol. Chem., 2015, 13, 5937
DOI: 10.1039/C5OB00676G

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