Under nitrogen atmosphere, 3-bromo-5-nitropyridine (20.3 g, 0.10 mol), pinacol ester of bisboronic acid (25.4 g, 0.10 mol), potassium acetate (14.7 g, 0.15 mol), and catalyst PdCl2 (dppf) (0.74 g, 0.001 mol) were sequentially added to 550 mL of dioxane and stirred well. The reaction system was slowly warmed up to 80-90 °C and the reaction was kept stirring for 2-3 hours. After monitoring the completion of the reaction by GC, the reaction mixture was cooled and filtered through diatomaceous earth to obtain a dark black filtrate. The filtrate was allowed to react at room temperature with stirring overnight under a hydrogen atmosphere at 1 atmosphere. At the end of the reaction, activated charcoal was added for decolorization, followed by distillation under reduced pressure to remove the solvent until no fraction escaped. Heptane mixed solvent was added to the residue, which was cooled and pulped for 30 min and filtered to obtain a light gray crude product. The crude product was dissolved by heating with ethanol, and crystals were precipitated after cooling, the filter cake was washed with anhydrous ethanol at -20°C, and after drying, 15.6g of 5-aminopyridine-3-boronic acid pinacol ester was obtained as a light yellow solid with a yield of 71% and a purity of 97.9% by HPLC.
