Controllable synthesis of benzoxazinones and 2-hydroxy-3-indolinones by visible-light-promoted 5-endo-dig N-radical cyclization cascade

• Published in: Cell reports physical science Vol. 2; no. 10; p. 100577
• Main Authors: Tan, Tong-De, Zhai, Tong-Yi, Liu, Bin-Yang, Li, Long, Qian, Peng-Cheng, Sun, Qing, Zhou, Jin-Mei, Ye, Long-Wu
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 20.10.2021
• Subjects: cyclizations; heterocycles; photocatalysis; radicals; tandem reaction; cyclizations; tandem reaction; radicals; photocatalysis; heterocycles
• ISSN: 2666-3864; 2666-3864
• DOI: 10.1016/j.xcrp.2021.100577

In recent years, significant advances have been made on photoredox-catalyzed N-radical addition to C-C unsaturated bond via N-H bond cleavage. However, these N-centered radical additions have so far been mostly limited to the alkenes, and to our knowledge, N-radical 5-endo-dig cyclizations of alkynes have been less exploited. Herein, we disclose an 5-endo-dig N-radical cascade cyclization of o-ethynylacetamides by photoredox catalysis involving rare radical cleavage of C-C triple bond, allowing the practical and controllable synthesis of a diverse array of valuable benzoxazinones and 2-hydroxy-3-indolinones in moderate to good yields under mild conditions. Furthermore, a mechanistic rationale for this radical cyclization cascade is supported by various control experiments and theoretical calculations. [Display omitted] •N-radical 5-endo-dig cyclization-initiated cascade reaction•Photoredox-catalyzed N-radical addition to C-C triple bond•C-C triple bond cleavage•Controllable and practical synthesis of diverse heterocycles Tan et al. describe a practical radical cascade reaction via photoredox-catalyzed N-centered radical addition to C-C triple bond, which represents the first N-radical 5-endo-dig cyclization cascade, to the best of their knowledge. This method enables the efficient and controllable synthesis of functionalized benzoxazinones and 2-hydroxy-3-indolinones with wide substrate scope under mild reaction conditions.