Methyl 2,5-dimethyl-1H-pyrrole-3-carboxylate (6.85 g, 45.0 mmol) was used as a raw material and was mixed with triethylamine (8.7 mL, 63.0 mmol) and dichloromethane (270 mL). Pyridinium bromide (15.7 g, 15.7 mmol) was added to the mixture in batches at 0 °C. The reaction mixture was stirred at 0 °C for 2 h before being poured into brine and extracted with ethyl acetate. The organic layers were combined, dried with anhydrous magnesium sulfate and subsequently concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (eluent: hexane-ethyl acetate). The final product, methyl 4-bromo-2,5-dimethyl-1H-pyrrole-3-carboxylate, was recrystallized by hexane-ethyl acetate to give yellow crystals (7.59 g, 92% yield).1H NMR (300 MHz, CDCl3) δ: 2.19 (3H, s), 2.47 (3H, s), 3.82 (3H, s), 8.20 (1H, s).
