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Plesner M, Hensel T, Nielsen BE, et al. Synthesis and properties of unsymmetrical azatrioxa[8]circulenes. Org Biomol Chem. 2015;13(21):5937-43doi: 10.1039/c5ob00676g.
Plesner, M., Hensel, T., Nielsen, B. E., Kamounah, F. S., Brock-Nannestad, T., Nielsen, C. B., Tortzen, C. G., Hammerich, O., & Pittelkow, M. (2015). Synthesis and properties of unsymmetrical azatrioxa[8]circulenes. Organic & biomolecular chemistry, 13(21), 5937-43. https://doi.org/10.1039/c5ob00676g
Plesner, Malene, et al. "Synthesis and properties of unsymmetrical azatrioxa[8]circulenes." Organic & biomolecular chemistry vol. 13,21 (2015): 5937-43. doi: https://doi.org/10.1039/c5ob00676g
Plesner M, Hensel T, Nielsen BE, Kamounah FS, Brock-Nannestad T, Nielsen CB, Tortzen CG, Hammerich O, Pittelkow M. Synthesis and properties of unsymmetrical azatrioxa[8]circulenes. Org Biomol Chem. 2015 Jun 07;13(21):5937-43. doi: 10.1039/c5ob00676g. PMID: 25925233.
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Org Biomol Chem. 2015 Jun 07;13(21):5937-43. doi: 10.1039/c5ob00676g.

Synthesis and properties of unsymmetrical azatrioxa[8]circulenes.

Organic & biomolecular chemistry

Malene Plesner, Thomas Hensel, Bjarne E Nielsen, Fadhil S Kamounah, Theis Brock-Nannestad, Christian B Nielsen, Christian G Tortzen, Ole Hammerich, Michael Pittelkow

Affiliations

  1. Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark. [email protected].

PMID: 25925233 DOI: 10.1039/c5ob00676g

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.

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