The reaction was carried out with 4-pyrazoleboronic acid pinacol ester (1.94 g, 10 mmol) and 2-bromoethyl methyl ether (1.68 g, 12 mmol) in a microwave reactor with stirring at 160 °C for 1 hour. Potassium carbonate (2.76 g, 20 mmol) and N,N-dimethylformamide (16 mL) were added as solvents to the reaction system. After completion of the reaction, the reaction mixture was concentrated and purified by silica gel column chromatography (eluent: 30% ethyl acetate/petroleum ether) to afford 1-(2-methoxyethyl)-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole (2.2 g, 90% yield) as a yellow oil. The product was characterized by 1H NMR (400 MHz, CDCl3): δ 1.32 (12H, s), 3.32 (3H, s), 3.75 (2H, t, J = 5.2 Hz), 4.30 (2H, t, J = 5.2 Hz), 7.77 (1H, s), 7.79 (1H, s). Mass spectral analysis: [M + H]+ m/z calculated value 253.2, measured value 253.2.
