Selective
bromination reactions of “click compounds”
are described. Electron-neutral and electron-deficient arenes selectively
undergo unprecedented Pd-catalyzed C–H <i>ortho</i>-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
