a) 3,3-Dimethyl-6-nitroindol-2-one (500 mg, 2.42 mmol) was dissolved in ethyl acetate (100 mL) and 10% palladium/activated carbon catalyst (129 mg, 121 μmol) was added. The reaction was stirred at 70 °C for 48 h under hydrogen atmosphere (balloon). After completion of the reaction, the catalyst was removed by filtration and the filtrate was washed with ethyl acetate. The filtrate was concentrated to give the orange powdery product 6-amino-3,3-dimethylindol-2-one (427 mg). The product was characterized by 1H NMR (DMSO-D6, 400 MHz): δ 10.75 (s, 1H), 7.92-7.89 (m, 1H), 7.62-7.58 (m, 2H), 1.30 (s, 6H).
