Synthesis
General procedure for the synthesis of 2,6-dichloro-3-aminopyridine from 2,6-dichloro-3-nitropyridine: To a solution of 2,6-dichloro-3-nitropyridine (100 g, 0.518 mol) in acetic acid (1 L) was added powdered iron (86.49 g, 1.555 mol) in batches. The reaction mixture was stirred at room temperature for 6 hours. The progress of the reaction was monitored by thin layer chromatography (TLC) system (petroleum ether/ethyl acetate = 8:2) to confirm the completion of the reaction. After completion of the reaction, the reaction mixture was concentrated under high vacuum. The crude product was dissolved in water (1 L) and ethyl acetate (EtOAc, 2 L). The pH of the aqueous solution was adjusted to 6.5 using sodium carbonate (Na2CO3) powder under stirring.The mixture was filtered through diatomaceous earth (Celite), the organic layer was separated, dried with anhydrous sodium sulfate and concentrated to give 2,6-dichloro-3-aminopyridine (80 g, 95% yield) as a white solid.1H NMR (400 MHz, DMSO-d6) δppm : 7.14-7.20 (2H, m), 5.78 (2H, s).
References
[1] Patent: WO2014/22349, 2014, A1. Location in patent: Paragraph 00221-00222
[2] Molecules, 2007, vol. 12, # 2, p. 218 - 230
[3] Journal of Organic Chemistry, 2011, vol. 76, # 23, p. 9841 - 9844
[4] Patent: WO2016/103097, 2016, A1. Location in patent: Page/Page column 47
[5] Journal of Heterocyclic Chemistry, 1984, vol. 21, # 3, p. 673 - 679
