Under argon protection, butyl lithium solution (1.6 M in hexane, 15.3 mL, 22.27 mmol) was slowly added dropwise to a solution of 5-bromo-2-methoxy-4-methylpyridine (4.5 g, 22.3 mmol) dissolved in 150 mL of tetrahydrofuran, keeping the reaction temperature at -78 °C. After the reaction mixture was stirred continuously at -78 °C for 1 h, triisopropyl borate (6.2 mL, 26.7 mmol) was added. Subsequently, the reaction system was slowly warmed to room temperature and stirring was continued overnight. Upon completion of the reaction, the mixture was poured into a mixture of equal volumes of saturated aqueous ammonium chloride solution and water and extracted with ethyl acetate. The organic layers were combined, washed with brine, dried over anhydrous sodium sulfate and concentrated. The crude product was washed with ethyl ether to afford 6-methoxy-4-methylpyridine-3-boronic acid as a white solid (2.12 g, 56.6% yield).LRMS (m/z): 168 (M + 1)+.
