452972-13-3

625-92-3

73183-34-3

452972-13-3

Preparation of compound 4-1 (5-bromopyridine-3-boronic acid pinacol ester) [221]: In a dry reaction flask 3,5-dibromopyridine (25 g, 105.5 mmol), pinacol ester of biboronic acid (28 g, 110.8 mmol), PdCl2(PPh3)2 (3.7 g, 5.27 mmol), and KOAc (20.7 g 211 mmol), and then 1,4-dioxane (211 mL) was added. The reaction mixture was stirred at reflux for 2 h at 120 °C. After completion of the reaction, it was cooled to room temperature and the organic layer was extracted with ethyl acetate. The organic layer was dried with anhydrous magnesium sulfate, filtered and concentrated. The crude product was purified by column chromatography to afford compound 4-1 (25 g, 86% yield) as a white solid.