An Expedient Synthesis of Carbazoles through Potassium tert‐Butoxide‐Promoted Intramolecular Direct C–H Bond Arylation

• Published in: European journal of organic chemistry Vol. 2017; no. 3; pp. 443 - 447
• Main Authors: Lin, Songbo, He, Xingrui, Meng, Jinpeng, Gu, Haining, Zhang, Peizhi, Wu, Jun
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 18.01.2017; Wiley Subscription Services, Inc
• Subjects: Carbazoles; Chemistry; Chemistry, Organic; Cross‐coupling; C–H arylation; Ethylene glycol; Fused‐ring systems; Metal‐free; Nitrogen heterocycles; Physical Sciences; Potassium; Science & Technology; DESIGN; Metal-free; METAL-FREE CONDITIONS; SOLAR-CELLS; C-H arylation; INDOLES; Carbazoles; AMINATION; Cross-coupling; Nitrogen heterocycles; DERIVATIVES; Fused-ring systems; CYCLIZATION; ACCESS; SUBSTITUTED CARBAZOLES; ALKALOIDS
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.201601293

Transition‐metal‐free access to carbazoles was achieved through base‐mediated intramolecular C–C bond formation. Reactions of N‐substituted o‐halodiarylamines with potassium tert‐butoxide in the presence of ethylene glycol or 1,10‐phenanthroline provided carbazoles in moderate to excellent yields. This transformation may proceed through a radical pathway according to a control experiment with a radical scavenger. Facile access to carbazoles through intramolecular C–H arylation from readily accessible N‐substituted o‐halodiarylamines under transition‐metal‐free conditions is reported. The intramolecular direct C–C cross‐coupling of N‐substituted o‐iododiarylamines proceeds under mild conditions (30 °C) by using ethylene glycol as a cheap and nontoxic additive.