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Synthesis of 1,1′‐ and 2,2′‐Bicarbazole Alkaloids by Iron(III)‐Catalyzed Oxidative Coupling of 2‐ and 1‐Hydroxycarbazoles
Author(s) -
Brütting Christian,
Fritsche Raphael F.,
Kutz Sebastian K.,
Börger Carsten,
Schmidt Arndt W.,
Kataeva Olga,
Knölker HansJoachim
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201704554
Subject(s) - oxidative coupling of methane , oxidative phosphorylation , catalysis , chemistry , coupling (piping) , combinatorial chemistry , peroxide , organic chemistry , materials science , biochemistry , metallurgy
We describe the synthesis of 1,1′‐ and 2,2′‐bicarbazoles by oxidative homocoupling of 2‐ and 1‐hydroxycarbazoles. The oxidative coupling using catalytic amounts of F 16 PcFe can be applied to both groups of substrates. Although F 16 PcFe generally provides the best yields for the synthesis of 1,1′‐bicarbazoles, di‐ tert ‐butyl peroxide affords better results for the 2,2′‐bicarbazoles. In our study, we have achieved the first syntheses of the biscarbalexines A–C, bisglybomine B, 2,2′‐dihydroxy‐7,7′‐dimethoxy‐3,3′‐dimethyl‐1,1′‐bicarbazole, bispyrayafoline C, and bisisomahanine. The iron‐catalyzed coupling of koenigine led to an improved synthesis of 8,8′′‐biskoenigine and afforded an unprecedented decacylic product. Oxidative coupling of 1‐hydroxycarbazoles led to bisclausenol, and to the first total syntheses of bismurrayafoline B and D.