2-Fluoro-4-methyl-5-nitro-aniline (1.85 g, 10.90 mmol) was suspended in concentrated hydrobromic acid (22 ml_) and cooled to 0 ℃. Solution of sodium nitrite (0.83 g, 12.00 mmol) in water (3.6 ml_) was added dropwise while maintaining the temperature at 0-5 °C. After stirring for 15 min, the mixture was filtered through a cotton pad and slowly poured into a solution of cuprous oxide (2.60 g, 17.5 mmol) and concentrated hydrobromic acid (20 ml) at 0 °C. After stirring overnight, the reaction mixture was diluted with EtOAc, washed with 10 % aq NaOH and 5percent aq Na2S2Os successively, dried over MgSO4, filtered and concentrated. The residue was purified by column chromatography (ethyl acetate: hexane; 2:98) to afford 1-Bromo-2-fluoro-4- methyl-5-nitro-benzene as a colorless oil (2.30 g, 91 %).
[1] Patent: WO2003/99824, 2003, A1. Location in patent: Page 32
[2] Patent: WO2003/99275, 2003, A1. Location in patent: Page 65
[3] Bioorganic and Medicinal Chemistry Letters, 2006, vol. 16, # 2, p. 457 - 460
[4] Patent: WO2015/54572, 2015, A1. Location in patent: Page/Page column 247
[5] Patent: US2004/224973, 2004, A1. Location in patent: Page 21
