[Synthesis]
General procedure for the synthesis of 1H-pyrrolo[2,3-b]pyridine-2,3-dione from 7-azaindol-2-one: Dry dimethylsulfoxide (DMSO, 6 mL) was heated to 120 °C, and 7-azaindol-2-one (500 mg, 3.7 mmol) and N-bromosuccinimide (NBS, 690.6 mg, 3.9 mmol) dissolved in a solution of anhydrous DMSO (2 mL). The reaction mixture was stirred at 120 °C for 30 min, and upon completion of the reaction, the pH was adjusted to 5-6 with 5% aqueous sodium bicarbonate (NaHCO3), followed by extraction with ethyl acetate. The organic phase was concentrated under reduced pressure to remove the solvent, and the resulting crude product was purified by column chromatography using ethyl acetate:hexane (3:1, v/v) as eluent to afford the target product 1H-pyrrolo[2,3-b]pyridine-2,3-dione (259.2 mg, 1.76 mmol, 65% yield) as a yellow solid. The structure of the product was characterized by nuclear magnetic resonance hydrogen spectroscopy (1H NMR, 400 MHz, DMSO-d6, δ= 2.49 ppm): 11.6 (s, 1H), 8.38 (dd, 1H, 3JH,H = 3.3 Hz, 4JH,H = 0.9 Hz), 7.87 (dd, 1H, 3JH,H = 5.0 Hz, 4JH,H = 1.1 Hz). 7.01 (dd, 1H, 3JH,H = 4.8 Hz, 4JH,H = 3.5 Hz) and NMR carbon spectra (13C-{1H} NMR, 150 MHz, DMSO-d6, δ= 39.5 ppm): 183.0, 164.0, 160.0, 155.2, 132.6, 119.0, 112.9 confirmed. Elemental analysis (C7H6N2O2): measured values C 56.66%, H 2.83%, N 18.72%; theoretical values C 56.76%, H 2.72%, N 18.91%. |