Selective C(sp2)−H Halogenation of "click" 4-Aryl-1,2,3-triazoles
Correa Navarro, Arkaitz
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Organic Letters 19(4) : 962-965 (2017)
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.