Pinacol ester of bisboronic acid (1.25 g, 4.92 mmol) was dissolved in DMF (10 mL) under nitrogen protection and cooled to 0 °C. KOAc (1.21 g, 12.3 mmol) and Pd(dppf)Cl2-CH2Cl2 (0.1 g, 0.123 mmol) were added sequentially. The reaction mixture was heated to 80 °C and a solution of 5-bromo-2-morpholine pyridine (1.0 g, 4.1 mmol) in DMF (10 mL) was added dropwise. After the dropwise addition, the reaction was continued to be stirred at 80 °C for 10 hours. After completion of the reaction, the solvent was removed by evaporation. The residue was dissolved in ethyl acetate and the insoluble material was removed by filtration. The filtrate was evaporated and purified by column chromatography (eluent ratio: ethyl acetate:petroleum ether = 1:4) to afford 6-(morpholin-4-yl)pyridine-3-boronic acid pinacol ester (940 mg, 79% yield).
