3-Amino-4-hydroxybenzoic acid

616-82-0

1571-72-8

The general procedure for the synthesis of 3-amino-4-hydroxybenzoic acid from 4-hydroxy-3-nitrobenzoic acid was as follows: tin(II) chloride (207 mg, 1.09 mmol), 12 N hydrochloric acid (1.5 mL), and 4-hydroxy-3-nitrobenzoic acid (100 mg, 0.55 mmol) were sequentially added to the reaction system at 0 °C. The reaction mixture was heated to reflux for 1 hour. After completion of the reaction, water was added to the mixture and the pH was adjusted to 1 with 2 N sodium hydroxide solution. the precipitate was collected by filtration and washed with distilled water. The filtrate was concentrated under vacuum and methanol was added to the residue. The precipitate formed was filtered again and the filtrate was concentrated under vacuum. Finally, the residue was purified by silica gel column chromatography using dichloromethane and methanol (5:1, v/v) as eluent to afford the target compound 3-amino-4-hydroxybenzoic acid (82 mg, 98% yield) as a brown solid. Its 1H NMR (500 MHz, DMSO-d6) data were as follows: δ 11.30 (brs, 1H), 9.42 (brs, 3H), 7.79 (s, 1H), 7.60 (d, 1H, J = 8.0 Hz), 7.07 (d, 1H, J = 8.0 Hz).