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Step 1: 5-Chloro-2-nitroaniline (6.0 g, 34.88 mmol) and N-bromosuccinimide (NBS, 6.06 g, 34.0 mmol) were dissolved in acetic acid (HOAc, 240 mL). The reaction mixture was stirred at 130 °C for 1 hour. Upon completion of the reaction, the mixture was slowly poured into water to quench the reaction. The resulting precipitate was collected by filtration and washed with petroleum ether to afford 4-bromo-5-chloro-2-nitroaniline as a light brown solid (8.25 g, 96.5% yield). The product was identified by 1H NMR (300 MHz, DMSO-d6): δ 8.24 (s, 1H), 7.62 (br s, 2H), 7.29 (s, 1H).LCMS (ESI) analysis showed m/z 251 ([M + H]+).

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