Synthesis
General procedure for the synthesis of 4-bromo-5-fluoro-2-nitrophenol from 4-bromo-3-fluorophenol: To a stirred mixture of 4-bromo-3-fluorophenol (10.23 g, 53.56 mmol), dichloromethane (108 mL), and sulfuric acid (6 mL, 107 mmol) was added slowly 65% nitric acid (3.8 mL, 53.6 mmol) at 0 °C. The reaction mixture was kept stirred at 0°C for 1 hour. After completion of the reaction, the mixture was diluted with water. The aqueous phase was extracted three times with dichloromethane and the organic layers were combined. The organic layer was concentrated and the resulting residue was purified by medium pressure liquid chromatography (MPLC) using a 10:1 to 2:1 gradient elution of hexane:ethyl acetate to afford 4-bromo-5-fluoro-2-nitrophenol (9.47 g, 75% yield) as a yellow solid.
References
[1] Patent: WO2015/171610, 2015, A2. Location in patent: Paragraph 000434
[2] Patent: WO2008/37746, 2008, A1. Location in patent: Page/Page column 15
[3] Patent: US2008/90804, 2008, A1. Location in patent: Page/Page column 6-7
[4] Patent: WO2010/130773, 2010, A2. Location in patent: Page/Page column 65-66
