GENERAL STEPS: To a solution of 4-bromo-1H-indole-7-carboxylic acid (33 g, 137 mmol) in N,N-dimethylformamide (DMF, 300 mL) was added cesium carbonate (Cs2CO3, 90 g, 276 mmol) and stirred at room temperature for 1 hour. Subsequently, iodomethane (29.3 g, 206 mmol) was added slowly and dropwise at 0 °C. The reaction mixture was gradually warmed up to room temperature and stirring was continued for 3 hours. After completion of the reaction, the mixture was poured into water and extracted with ethyl acetate (EtOAc, 200 mL x 2). The organic layers were combined, washed with saturated brine, dried over anhydrous sodium sulfate (Na2SO4), filtered and concentrated under reduced pressure. The residue was purified by silica gel column chromatography to afford methyl 4-bromo-1H-indole-7-carboxylate (13.8 g, 20% yield). The structure of the product was confirmed by 1H NMR (CDCl3): δ 9.98 (s, 1H), 7.76-7.74 (d, J = 8 Hz, 1H), 7.39-7.34 (m, 2H), 6.68-6.66 (m, 1H), 4.00 (s, 3H).
