The general procedure for the synthesis of 4-bromo-3-phenyl-1H-pyrazole from 3-phenyl-1H-pyrazole was as follows: 3-phenyl-1H-pyrazole (4.08 g, 28.3 mmol) and N-bromosuccinimide (NBS, 5.04 g, 28.3 mmol) were dissolved in N,N-dimethylformamide (DMF, 40 mL), and the reaction was stirred for 1 h at room temperature. After completion of the reaction, the reaction mixture was poured into water and extracted with ethyl acetate (AcOEt). The organic phases were combined, washed sequentially with water and saturated saline, dried over anhydrous magnesium sulfate (MgSO?) and concentrated under reduced pressure to remove the solvent. The resulting residue was recrystallized by hexane/ethyl acetate mixed solvent to give the title compound 4-bromo-3-phenyl-1H-pyrazole (5.84 g, 93% yield) as a white solid with a melting point of 114-116 °C. The NMR hydrogen spectrum (300 MHz, CDCl?) data were as follows: δ 7.39-7.50 (m, 3H), 7.64 (s, 1H), 7.77 (d, J = 6.8 Hz, 2H), 10.73 (brs, 1H).
