Synthesis
The general procedure for the synthesis of 5-bromo-2-ethoxypyridin-3-amine from 5-bromo-2-ethoxy-3-nitropyridine was as follows: 5-bromo-2-ethoxy-3-nitropyridine (75.2 mg, 0.304 mmol) was dissolved in ethyl acetate (3 mL), and stannous chloride (II) (289 mg, 1.52 mmol) was added. The reaction mixture was heated to reflux and maintained for 2 hours. Upon completion of the reaction, it was cooled to room temperature and 50% aqueous sodium hydroxide solution was added slowly and dropwise until a viscous brown solid formed in the reaction mixture. Subsequently, anhydrous sodium sulfate was added and stirred for several minutes. Solid impurities were removed by filtration and the filtrate was dried with anhydrous sodium sulfate, filtered again and concentrated under reduced pressure to afford 5-bromo-2-ethoxypyridin-3-amine (53 mg, 0.25 mmol, 80% yield) as a dark blue film. The product was characterized by 1H NMR (400 MHz, CDCl3): δ 7.56 (d, 1H), 6.97 (d, 1H), 4.37 (q, 2H), 3.85 (br s, 2H), 1.40 (dd, 3H); the results of mass spectrometry (EI) analysis conformed to the molecular weight of C7H9BrN2O: 217,219 (Br isotope, MH+).
References
[1] Patent: WO2010/135524, 2010, A1. Location in patent: Page/Page column 237
[2] Patent: WO2016/38582, 2016, A1. Location in patent: Paragraph 00144
[3] Patent: WO2009/147187, 2009, A1. Location in patent: Page/Page column 132
