Synthesis
As shown in Step 2-iv of Scheme 2, a methanolic solution of 2,5-dibromo-3-methoxypyridine (13.0 g, 43.8 mmol) and 25 wt% sodium methanolate (95.0 mL, 438.3 mmol) was placed in a reaction vial and the reaction was stirred for 3 hours at 75 °C. Upon completion of the reaction, the mixture was cooled to room temperature and subsequently extracted by adding ethyl acetate and saturated saline. The organic phase was separated, dried with anhydrous magnesium sulfate, filtered and concentrated under reduced pressure. The residue was purified by silica gel column chromatography to afford 5-bromo-2,3-dimethoxypyridine (9.1 g, 95% yield). The product was characterized as follows: ESMS (M + 1) = 218/220; 1H NMR (DMSO-d6) δ 7.8 (d, 1H), 7.46 (d, 1H), 3.81 (s, 3H), 3.86 (s, 3H).
