Selective C(sp²)–H Halogenation of “Click” 4‑Aryl-1,2,3-triazoles

Selective bromination reactions of “click compounds” are described. Electron-neutral and electron-deficient arenes selectively undergo unprecedented Pd-catalyzed C–H ortho-halogenations assisted by simple triazoles as modular directing groups, whereas electron-rich arenes are regioselectively halogenated following an electrophilic aromatic substitution reaction pathway. These C–H halogenation procedures exhibit a wide group tolerance, complement existing bromination procedures, and represent versatile synthetic tools of utmost importance for the late-stage diversification of “click compounds”. The characterization of a triazole-containing palladacycle and density functional theory studies supported the mechanism proposal.本研究报道了‘点击化学化合物（click compounds）’的选择性溴化反应。电子中性与缺电子芳烃可在简单三唑作为模块化导向基团的辅助下，发生前所未有的钯催化C-H邻位卤化反应；而富电子芳烃则通过亲电芳香取代反应路径实现区域选择性卤化。此类C-H卤化反应具有广泛的基团耐受性，可作为现有溴化方法的重要补充，同时亦是用于‘点击化学化合物’后期多样化修饰的通用合成工具，具备至关重要的应用价值。对含三唑的钯环配合物的表征以及密度泛函理论（density functional theory）研究，为该反应的机理假说提供了有力支撑。