[Synthesis]
General method (10): 5-Aminoindole (1.0 eq.) and triethylamine (3.6 eq.) were dissolved in dichloromethane (10 mL, corresponding to 1.182 mmol of raw material) and acetyl chloride (1.2 eq.) was added slowly. The reaction mixture was stirred at room temperature for 3 hours. After completion of the reaction, the mixture was poured into water and extracted three times with dichloromethane. The organic layers were combined, washed with brine, dried over anhydrous sodium sulfate and concentrated under reduced pressure. Purification by fast silica gel column chromatography using 7:3 hexane/ethyl acetate as eluent afforded 5-acetamidoindole (Intermediate 17A/-(1/-/-indol-5-yl)acetamide, Intermediate 17) as a clear oil (177 mg, 1.016 mmol, 85% yield).1H NMR (400 MHz, CDCl3) δ 8.27 ( bs, 1H), 7.80 (s, 1H), 7.30 (d, J = 8.5 Hz, 2H), 7.20 (dd, J = 8.8, 2.0 Hz, 2H), 6.50 (s, 1H), 2.18 (s, 3H). |