Example A3: To a solution of sulfuric acid (125 mL) was added 30% H2O2 (63.1 mL, 2058 mmol) dropwise at 0°C and stirred for 15 minutes. Subsequently, a cold sulfuric acid (125 mL) solution of 6-amino-3-bromo-2-methylpyridine (35 g, 187 mmol) was added dropwise. The reaction mixture was slowly warmed to room temperature and stirred continuously for 4 hours. Upon completion of the reaction, the mixture was poured into ice (1.2 kg) and the solid formed was collected by filtration. The solid was dissolved in dichloromethane (DCM), washed with brine, dried over anhydrous Na2SO4 and concentrated to dryness. The aqueous filtrate and washings were combined, extracted with DCM (2 times), the organic phases were combined, dried over anhydrous Na2SO4 and concentrated to dryness. Purification by silica gel column chromatography (eluent: EtOAc/Hex), combined with the previously separated solids, afforded the target product 3-bromo-2-methyl-6-nitropyridine (25.59 g, 63% yield). Mass spectrum (ESI) m/z: 218.9 (M+H+).
