Indol-3-ylacetic acid (1.00 g, 5.71 mmol) was dissolved in 25 mL of ethanol and concentrated sulfuric acid (1.0 mL, 18.4 mmol) was added. The reaction mixture was stirred under reflux conditions for 2 hours. Upon completion of the reaction, the mixture was cooled to 0 °C in an ice bath and subsequently neutralized with 2 N sodium hydroxide solution. The organic solvent was removed by evaporation under reduced pressure and the residue was partitioned between dichloromethane and water. The aqueous phase was extracted twice with dichloromethane, and the organic phases were combined, washed with saturated brine, dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to give 1.02 g (5.02 mmol, 88% yield) of ethyl indole-3-acetate as a brown oil. The product was confirmed by nuclear magnetic resonance hydrogen spectroscopy (1H NMR, 300 MHz, CDCl3): δ 8.09 (br.s, 1H), 7.63 (d, J = 7.69 Hz, 1H), 7.35 (d, J = 7.69 Hz, 1H), 7.04-7.25 (m, 3H), 4.17 (q, J = 7.14 Hz, 2H), 3.77 (s, 2H), 1.26 (t, J = 7.14 Hz, 3H). Ultra performance liquid chromatography-mass spectrometry (UPLC/MS) analysis showed a retention time of 1.58 min, and low resolution mass spectrometry (LRMS) measured m/z 204 ([M+1]+).
