Hydroxylamines As Bifunctional Single-Nitrogen Sources for the Rapid Assembly of Diverse Tricyclic Indole Scaffolds

• Published in: Journal of the American Chemical Society Vol. 142; no. 14; pp. 6698 - 6707
• Main Authors: Fan, Liangxin, Hao, Jiamao, Yu, Jingxun, Ma, Xiaojun, Liu, Jingjing, Luan, Xinjun
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 08.04.2020; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Multidisciplinary; Physical Sciences; Science & Technology; ORGANOCATALYTIC SYNTHESIS; AMINO SOURCES; PALLADIUM; AZIRIDINATION; CATALYZED AMINATION; EFFICIENT SYNTHESIS; N-H; STEREOSPECIFIC SYNTHESIS; ARYL IODIDES; C-H AMINATION
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.0c00403

Conventional approaches on using hydroxylamine derivatives as single nitrogen sources, for the construction of n-membered (n > 3) N-heterocycles, rely upon two chemical operations by involving sequential nucleophilic and electrophilic C–N bond formations. Here, we report a highly efficient cascade of alkyne insertion/C–H activation/amination for the rapid preparation of a myriad of tricyclic indoles, in a single-step transformation, by using bifunctional secondary hydroxylamines. It is noteworthy that judicious selection of applicable amino agents, for enabling the prior oxidative addition of aryl iodide to initial Pd(0) species and subsequent two C–N bonds formation, was the key to the success of this reaction. Control experiments indicated that a five-membered palladacyclic intermediate played a crucial role in promoting the final aminative ring closure.