Methyl lithium (1.6 M ether solution, 30 mL, 51.2 mmol) was added slowly and dropwise to a solution of anhydrous tetrahydrofuran (30 mL) of indole-5-carboxylic acid (2.5 g, 15.5 mmol) at 0 °C and under nitrogen protection. The reaction mixture was stirred at room temperature for 4 hours before the reaction was quenched with aqueous ammonium chloride solution and extracted with dichloromethane (3 x 50 mL). The organic layers were combined, washed with saturated brine, dried over anhydrous sodium sulfate and concentrated under reduced pressure to give 5-acetylindole (1.8 g, white solid).
