General procedure for the synthesis of 2-nitro-4-chloro-6-bromoaniline from 4-chloro-2-nitroaniline: 4-chloro-2-nitroaniline (5.1 g, 30 mmol) and N-bromosuccinimide (6.2 g, 36 mmol) were dissolved in acetonitrile (50 mL) and the reaction was heated to reflux overnight. After completion of the reaction, the mixture was cooled to room temperature and diluted with ethyl acetate (50 mL). Subsequently, the mixture was washed with saturated aqueous potassium carbonate (100 mL x 2). The organic phase was separated, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure to afford the target compound 2-nitro-4-chloro-6-bromoaniline (109a) as a yellow solid (8.1 g, 100% yield).LCMS analysis showed [M + H]+ of 253.1 H NMR (500 MHz, CDCl3) δ 8.17 (d, J = 2.5 Hz, 1H), 1 H 7.71 (d, J = 2.5 Hz, 1H), 6.64 (s, 2H).
