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<p>Atropisomeric carbazoles are widely used in organic synthesis, medicine, and material science. Although the enantioselective coupling of two aryl units provides a straightforward means to access biaryl atropisomers, this approach has yet to be explored extensively for carbazole-based structures due to their diverse reactive sites. This report presents a chiral phosphoric acid-catalyzed approach to achieve enantioselective synthesis of carbazole-based atropisomers with exceptional chemo-, site-, and stereoselectivities. The key innovation lies in the organocatalytic activation of the heteroaromatic compound, which represents the first example of converting nucleophilic carbazoles into electrophilic species, thereby enriching the field of carbazole chemistry. Hydrazine-decorated carbazoles undergo oxidative homo-coupling to furnish atropisomeric bicarbazoles, while the inclusion of external indole nucleophiles as coupling partners leads to the formation of indole-carbazole atropisomers. A novel chiral phosphine ligand has been synthesized on the homo-coupled bicarbazole skeleton. The distinctive features of this complex reaction system were enabled by the <i>in situ</i> oxidation of both substrates and products, as well as the judicious choice of indoles as nucleophiles to regulate selective coupling.</p>

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Chiral phosphoric acid-catalyzed atroposelective oxidative coupling of carbazoles

  • 期刊论文

  • 发表日期：

    2025年3月14日

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  • Qian Lu,
  • Minjie Bi,
  • Yong-Bin Wang,
  • Limin Yang,
  • Huan-Huan Liu,
  • Shao-Hua Xiang,
  • Bin Tan

摘要

Atropisomeric carbazoles are widely used in organic synthesis, medicine, and material science. Although the enantioselective coupling of two aryl units provides a straightforward means to access biaryl atropisomers, this approach has yet to be explored extensively for carbazole-based structures due to their diverse reactive sites. This report presents a chiral phosphoric acid-catalyzed approach to achieve enantioselective synthesis of carbazole-based atropisomers with exceptional chemo-, site-, and stereoselectivities. The key innovation lies in the organocatalytic activation of the heteroaromatic compound, which represents the first example of converting nucleophilic carbazoles into electrophilic species, thereby enriching the field of carbazole chemistry. Hydrazine-decorated carbazoles undergo oxidative homo-coupling to furnish atropisomeric bicarbazoles, while the inclusion of external indole nucleophiles as coupling partners leads to the formation of indole-carbazole atropisomers. A novel chiral phosphine ligand has been synthesized on the homo-coupled bicarbazole skeleton. The distinctive features of this complex reaction system were enabled by the in situ oxidation of both substrates and products, as well as the judicious choice of indoles as nucleophiles to regulate selective coupling.