Synthesis
The general procedure for the synthesis of 2-methoxy-3,5-dibromopyridine from 5-bromo-2-methoxypyridine was as follows: bromine (17.8 g, 111 mmol) was slowly added to a mixed solution containing 5-bromo-2-methoxypyridine (12.0 g, 63.8 mmol), sodium acetate (5.23 g, 63.8 mmol) and acetic acid (65 mL). The reaction mixture was stirred at 80 °C for 4 hours, followed by continued stirring at room temperature for 12 hours. After completion of the reaction, the mixture was diluted with ether and washed sequentially with water, saturated sodium bicarbonate solution and brine. The organic layer was separated, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The crude product was purified by column chromatography with the eluent being a petroleum ether solution of 1-5% ethyl acetate to give 10.6 g of the target product 2-methoxy-3,5-dibromopyridine. The product was characterized by 1H NMR (300 MHz, DMSO-d6) with chemical shifts of 8.20-8.40 (m, 2H) and 3.92 (s, 3H).
References
[1] Patent: US2010/81673, 2010, A1. Location in patent: Page/Page column 14
[2] Patent: US2015/210671, 2015, A1. Location in patent: Paragraph 0173; 0181; 0182
[3] Patent: US9145393, 2015, B2. Location in patent: Page/Page column 37; 38
