General procedure for the synthesis of 2-bromo-3-nitropyridine from 2-amino-3-nitropyridine: 3-nitropyridin-2-amine (1.0 g, 7.19 mmol) was dissolved in 35 mL of DMSO, KNO2 (2.45 g, 28.75 mmol) and CuBr (0.206 g, 1.44 mmol) were added. A 48% aqueous HBr solution (3.60 mL, 32.0 mmol) dissolved in DMSO (35 mL) was slowly added dropwise to the above mixture at 35 °C. After the dropwise addition was completed, the reaction mixture was stirred at 35°C for 4 hours. Subsequently, the reaction solution was transferred to 100 mL of ice water solution containing K2CO3 (7 g). The reaction mixture was extracted with ether, the ether layer was washed with water and dried over anhydrous Na2SO4. The solvent was removed by concentration under reduced pressure to give the crude product. The crude product was purified by silica gel column chromatography (eluent: 100% dichloromethane) to afford 2-bromo-3-nitropyridine as a beige powder (0.662 g, 45% yield). Thin-layer chromatography Rf value was 0.75 (dichloromethane); melting point was 121-122 °C (literature value: 123-124 °C); IR (KBr) νmax (cm-1): 3042 (νCHar), 1578 and 1562 (νC=C), 1524 (νasNO2), 1350 (νsyNO2); 1H NMR (400 MHz. DMSO-d6): δ 8.73 (dd, 1H, J1=1.6Hz, J2=4.8Hz, H-6), 8.54 (dd, 1H, J1=1.6Hz, J3=8.0Hz, H-4), 7.79 (dd, 1H, J2=4.8Hz, J3=8.0Hz, H-5); 13C NMR (100MHz, DMSO -d6): δ 153.26 (C-6), 147.08 (C-3), 134.48 (C-4), 132.08 (C-2), 124.44 (C-5); MS (ESI) m/z (%): 202.9 (100) [M+H]+, 204.9 (100) [M+H+2]+. Calculated elemental analysis (C5H3BrN2O2): C, 29.58; H, 1.49; N, 13.80. measured values: C, 29.63; H, 1.50; N, 13.83.
