5-Aminooxindole

20870-79-5

20876-36-2

General procedure for the synthesis of 5-amino-dihydroindol-2-one from 5-nitroindol-2-one: 5-nitrodihydroindol-2-one (5 g, 1 equiv.) was suspended in ethanol (50 mL), activated charcoal (1 g) and ferric chloride (1 g) were added. The reaction mixture was heated to 78 °C and stirred continuously for 10 minutes. Subsequently, 80% aqueous hydrazine hydrate (8 eq.) was slowly added dropwise to the reaction system over 5 minutes. After the dropwise addition was completed, the reaction mixture was continued to be stirred at 78°C for 8-10 hours. Upon completion of the reaction, the mixture was cooled to room temperature and filtered to remove the activated carbon residue. The filtrate was concentrated in vacuum to give the crude product, which was purified by recrystallization with ethanol (about 15 mL) to give the final 5-amino dihydroindol-2-one as a light yellow solid in 91.9% yield.