Synthesis
Step 1: To a stirred solution of 6-bromo-3-nitropyridin-2-amine (2.5 g, 11.47 mmol) in a mixed solvent of glacial acetic acid (10 mL), methanol (10 mL), and ethanol (10 mL) was added zinc powder (3.73 g, 57.35 mmol) in batches at 0 °C. The reaction mixture was stirred at room temperature for 15 hours. After completion of the reaction, the mixture was filtered through a diatomaceous earth pad and the filtrate was concentrated under reduced pressure. The concentrated residue was partitioned between saturated aqueous sodium bicarbonate solution and ethyl acetate. The organic layer was separated and the aqueous layer was extracted with additional ethyl acetate. All organic layers were combined, washed with brine, dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure to give 6-bromopyridine-2,3-diamine (1.30 g, 60% yield) as a solid, which did not require further purification. The product was characterized by 1H NMR (300 MHz, DMSO-d6) and LCMS (ESI): 1H NMR δ 6.61 (d, J = 7.7 Hz, 1H), 6.47 (d, J = 7.7 Hz, 1H), 5.82 (s, 2H), 4.79 (s, 2H); LCMS (ESI) m/z 188 and 190 (M + H)+.
References
[1] Patent: EP2766359, 2016, B1. Location in patent: Paragraph 0578
[2] Patent: US2010/222345, 2010, A1. Location in patent: Page/Page column 91
[3] Patent: US2014/315888, 2014, A1. Location in patent: Paragraph 1221-1222
[4] Patent: US6348474, 2002, B1. Location in patent: Page column 45
