1354356-24-3

845306-08-3

73183-34-3

1354356-24-3

Step 1: Synthesis of tert-butyl 5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine-2-carboxylate A 1,4-dioxane solution (3.69 mL) of tert-butyl 5-bromopyridine-2-carboxylate (0.50 g, 1.937 mmol), potassium acetate (0.380 g, 3.87 mmol), pinacol ester of bis(boronic acid) (0.590 g, 2.325 mmol), and DMSO (0.184 mL) were added to a reaction flask under argon gas protection. The mixture was deoxygenated by argon bubbling for 5 min followed by addition of PdCl2(dppf)-CH2Cl2 adduct (0.079 g, 0.097 mmol). Subsequently, the reaction mixture was stirred at 90°C for 3 hours. After completion of the reaction, it was cooled to room temperature and the reaction solution was extracted and layered with ethyl acetate (300 mL) and water (80 mL). The organic phase was washed with water (100 mL×2) and saturated saline in turn, dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure to obtain the crude product. The crude product was purified by ISCO silica gel column chromatography (n-hexane/ethyl acetate gradient elution, 24 g silica gel column), and the target fraction was collected and concentrated to afford 0.60 g (near quantitative yield) of tert-butyl 5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine-2-carboxylate as a nearly white solid. The product was analyzed by HPLC (Method B) with a retention time of 2.07 min.1H NMR (400 MHz, chloroform-d) δ 9.05 (s, 1H), 8.17 (dd, J = 7.8, 1.7 Hz, 1H), 7.99 (dd, J = 7.7, 0.9 Hz, 1H), 1.28 (s, 9H), 1.25 (s, 12H).