General procedure for the synthesis of 4-bromo-2-nitrobenzonitrile from 2-amino-4-bromobenzonitrile: 2-amino-4-bromobenzonitrile (4.5 g, 22.8 mmol) was added to cold trifluoroacetic acid (18 mL) at 0 °C. After stirring for 10 min, 33% hydrogen peroxide solution (7 mL, 67.8 mmol) was slowly added. The reaction mixture was stirred at room temperature for 0.5 hr, then warmed to 50 °C and continued stirring for 2 hr. Upon completion of the reaction, the mixture was poured into ice water and the precipitated solid was filtered and washed with cold water to afford an off-white solid 4-bromo-2-nitrobenzonitrile (3.64 g, 70% yield) with a melting point of 205 °C. The structure of the product was confirmed by IR and NMR: IR (KBr) νmax/cm-1: 3042 (Ar-H), 2252 (CN), 1520,1412 (C=C).1H NMR (500 MHz, DMSO-d6) δ: 8.15 (dd, 1H, J=2.4,8.5 Hz, H-5); 8.25 (d. 1H, J=8.4Hz, H-6); 8.46 (d, 1H, J=2.4Hz, H-3).13C NMR (125.7MHz, DMSO-d6) δ: 108.88 (C-1), 114.54 (CN), 127.43 (C-3), 128.75 (C-4), 137.57 (C-5/C-6). 138.10 (C-5/C-6), 147.59 (C-2). Elemental analysis calculated values (%) C7H3BrN2O2 (225.94): C: 37.03, H: 1.33, N: 12.34; measured values (%): C: 37.00, H: 1.37, N: 12.27.
