1. 4-Bromo-1-methyl-3-phenyl-1H-pyrazole (300 mg) was dissolved in anhydrous tetrahydrofuran (6 mL) under argon protection and cooled to -80 °C. The reaction was carried out by stirring for 30 min.
2. 1.6 mol/L n-butyllithium-hexane solution (1.2 mL) was added slowly dropwise, keeping the temperature at -80 °C, and the reaction was stirred for 30 min.
3. 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (470 mg) was added to the reaction mixture at the same temperature.
4. the reaction mixture was slowly warmed to room temperature over a period of 4 hours with continuous stirring.
5. Upon completion of the reaction, the reaction was quenched by the addition of saturated aqueous ammonium chloride and extracted with ethyl acetate.
6. The organic layer was separated, washed with saturated aqueous sodium chloride and dried over anhydrous sodium sulfate.
7. The solvent was removed by pressurized distillation, and the crude product was obtained.
8. The crude product was purified by silica gel column chromatography (eluent: ethyl acetate/hexane) to afford 1-methyl-3-phenyl-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole (184 mg).
9. Mass spectrometry analysis showed the molecular ion peak of the target compound m/z (M+H): 285.
