Photoinduced Cyclization of 2-Alkynylanilines to Access 3-Bromoindole Scaffolds
Chen Ling1, Luomo Li1, Yi-Fei Chen1
1Advanced Research Institute of Multidisciplinary Science, and School of Chemistry and Chemical Engineering, Key Laboratory of Medical Molecule Science and Pharmaceutical Engineering, Ministry of Industry and Information Technology, Beijing Institute of Technology, Beijing 100081, P. R. China.
Abstract:
Herein, we report a visible-light-driven, photocatalyst-free protocol for synthesizing 3-bromoindoles via tandem cyclization-bromination from readily available 2-alkynyl anilines and ethyl 2,2-dibromo-3-oxobutanoate as the bromine source. This operationally simple method enables simultaneous indole formation and C3-bromination in one step, featuring broad substrate scope, excellent functional group tolerance, and good scalability. Mechanistic studies support a radical pathway initiated by visible-light-induced homolytic cleavage. Synthetic utility is demonstrated by gram-scale synthesis and diverse late-stage derivatizations.
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