Fig. 4: Mechanistic study and proposed mechanism.

a Comparison of the PTC1-Br₂ intermediate formation conditions. Ar = 3,5-bis(trifluoromethyl)phenyl. b Effect of NaHCO₃ and NaOH in the bromination process using preformed PTC1-Br₂ as a stoichiometric reagent. When NaOH was used, no conversion of 1a was observed because it decomposed PTC1-Br₂. In contrast, NaHCO₃ prevented this decomposition and recovered the desired reactivity, which mimicked the standard condition. c, d Cyclic voltammetry measurements in H₂O with 0.1 M NaNO₃ and 5 mM substrate at room temperature with a scan rate of 100 mVs⁻¹. e Detailed mechanism including the roles of NaHCO₃.