General procedure for the synthesis of 4-bromo-1,2-dinitrobenzene from 4-bromo-2-nitroaniline: 4-bromo-2-nitroaniline (4.96 g, 22.96 mmol) was added to cold trifluoroacetic acid (25 mL) at 0 °C. After stirring for 10 min, 33% hydrogen peroxide solution (13.75 mL, 133 mmol) was slowly added and the reaction mixture was stirred at room temperature for 0.5 h. Subsequently, it was warmed up to 50 °C and continued to be stirred for 2 h. Upon completion of the reaction, the mixture was poured into ice water, the precipitated solid was collected by filtration and washed with cold water to afford the target compound 4-bromo-1,2-dinitrobenzene. Yield: 76%, yellow solid.1H NMR (500 MHz, CDCl3) δ 7.85-7.92 (m, 2H, H-5, H-6), 8.04 (br.s, 1H, H-3).13C NMR (125.7 MHz, CDCl3) δ 126.39 (C-2), 127.91 (C-3), 128.09 (C- 4), 136.29 (C-5), 141.26 (C-1), 143.42 (C-2). Elemental analysis (C6H3BrN2O4) Calculated values: C, 29.18; H, 1.22; N, 11.34%. Measured values: C, 29.12; H, 1.26; N, 11.26%.
