Step 1. Synthesis of 5-bromo-2-methyl-7H-indole: To a solution of 2-methyl-1H-indole (5.0 g, 38.12 mmol) in sulfuric acid (80 mL) was added Ag2SO4 (12.5 g, 40.06 mmol) under cooling in an ice bath and stirred for 30 min. Subsequently, Br2 (6.4 g, 40.05 mmol) was slowly added dropwise over 30 minutes. After the dropwise addition, the reaction mixture was continued to be stirred at room temperature for 4 hours. Upon completion of the reaction, the reaction was quenched by the addition of a water/ice mixture (300 mL). The reaction mixture was extracted with dichloromethane (3 x 200 mL), the organic layers were combined, dried over anhydrous sodium sulfate, and concentrated under reduced pressure to afford 5-bromo-2-methyl-7H-indole as a light brown solid (6 g). The product was detected by LC-MS: [M+H]+ m/z 211.0. 1H-NMR (300MHz, CDCl3) δ: 11.23 (s, 1H), 7.56 (s, 1H), 7.21 (d, J=8.7Hz, 1H), 7.07-7.09 (m, 1H), 6.11 (s, 1H), 2.38 (s, 3H).
