The general procedure for the synthesis of 2-bromo-5-methylpyridine nitrogen oxides from 2-bromo-5-methylpyridine was as follows: 2-bromo-5-methylpyridine (4 g, 2.3 mmol) was dissolved in dichloromethane (500 mL) at 0 °C and m-CPBA (52 g, 304 mmol) was added slowly. The reaction mixture was stirred continuously at room temperature for 20 hours. Upon completion of the reaction, the pH was adjusted with saturated K2CO3 solution to about 9. The organic layer was separated and concentrated to give the crude product. The crude product was purified by fast silica gel column chromatography with petroleum ether/ethyl acetate (1:1, v/v) as eluent to afford the target compound 2-bromo-5-methylpyridine 1-oxide (33 g, 75% yield). The structure of the product was confirmed by 1H NMR (CDCl3): δ 8.25 (s, 1H), 8.75 (d, 1H, J = 8.4 Hz), 6.95-6.94 (m, 1H), 2.30 (s, 3H).
