Synthesis
General procedure for the synthesis of 2,4-difluoro-5-bromoaniline from 2,4-difluoro-5-bromonitrobenzene: In a 250 mL round-bottomed flask, 5-bromo-2,4-difluoro nitrobenzene (5.04 g, 21.3 mmol), saturated ammonium chloride solution (25.0 mL), iron powder (5.00 g, 89.5 mmol), ethanol (100 mL), tetrahydrofuran (50.0 mL), and water (25.0 mL), and refluxed at 95 °C for 1.5 hours. Upon completion of the reaction, it was cooled to room temperature, saturated sodium bicarbonate solution (100 mL) was added, and the mixture was filtered through diatomaceous earth and the diatomaceous earth was washed with ethyl acetate (3 x 50 mL). The combined filtrates were washed sequentially with water and brine, dried with anhydrous magnesium sulfate, filtered and concentrated under reduced pressure. The crude product was purified by fast chromatography (ethyl acetate: hexane = 1:9) to afford 5-bromo-2,4-difluoroaniline (2.61 g, 59.1% yield).1H NMR (400 MHz, CDCl3) δ 6.97 (dd, 1H, J = 7.2, 6.7 Hz), 6.85 (t, 1H, J = 8.2 Hz), 3.63 (br, 2H) .
References
[1] Journal of Medicinal Chemistry, 2007, vol. 50, # 16, p. 3870 - 3882
[2] Patent: WO2004/5257, 2004, A1. Location in patent: Page 67-68
[3] Journal of the American Chemical Society, 1956, vol. 78, p. 2593,2596
