Pushing Radical Cyclization from Regioselective to Regiospecific:  Cyclization of Amidyl Radicals Controlled by Vinylic Halogen Substitution

作者：Tianshun Hu, Mei‐Hua Shen, Qian Chen, Chaozhong Li · 发表于：Organic Letters · 年份：2006 · DOI：10.1021/ol060983q · 被引用次数：52 · 研究领域：Radical Photochemical Reactions、Catalytic C–H Functionalization Methods、Sulfur-Based Synthesis Techniques

Efficient and regiospecific 6-exo, 7-endo, 7-exo, and even 8-endo amidyl radical cyclizations can be accomplished by the direct reactions of unsaturated N-H amides if they bear a vinylic halogen (Cl, Br, I) substituent. This remarkable halogen-substitution effect could be rationalized in terms of lone pair-lone pair electron repulsion between the N radical and the vinylic halogen atom, in addition to the well-known steric and radical-stabilizing effect. [reaction: see text]