Synthesis and properties of unsymmetrical azatrioxa[8]circulenes
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...
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Veröffentlicht in: | Organic & biomolecular chemistry 2015-06, Vol.13 (21), p.5937-5943 |
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Hauptverfasser: | , , , , , , , , |
Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | 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. |
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ISSN: | 1477-0520 1477-0539 |
DOI: | 10.1039/c5ob00676g |