Synthesis
The general procedure for the synthesis of 3-aminophthalic acid hydrochloride from 3-nitrophthalic acid was as follows: an ethanol solution (600 mL) of 3-nitrophthalic acid (100 g) and 10% Pd/C catalyst (3.2 g) was added to an autoclave. A hydrogen pressure of 4.0 kg was applied at 20-25 °C and the reaction was carried out for 3.0 hours. Upon completion of the reaction, the reaction mixture was cooled to 20 °C and filtered through a Hyflo bed. The filtrate was concentrated by distillation under reduced pressure and acetone was added to the residue. The mixture was cooled to 10 °C and concentrated hydrochloric acid was added slowly with continuous stirring. After removing the solvent under reduced pressure, acetonitrile was added. The mixture was again cooled to 10°C and the precipitated solid was filtered. Finally, the product was dried under vacuum at 45-50 °C for 6 h to give 3-aminophthalic acid hydrochloride (65.0 g).
References
[1] Patent: US5103057, 1992, A
[2] Patent: EP434145, 1991, A2
[3] Patent: WO2017/33116, 2017, A1. Location in patent: Paragraph 00114; 00132
[4] Patent: CN106986783, 2017, A. Location in patent: Paragraph 0008
