Synthesis
General procedure for the synthesis of 3,5-diaminobenzoic acid from 3,5-dinitrobenzoic acid: 3,5-dinitrobenzoic acid (51 g, 0.24 mol) and 300 mL of water were added to a 1 L stainless steel high-pressure reactor and stirred thoroughly until homogeneous. Subsequently, the pH of the reaction system was adjusted to 7-8 using an aqueous sodium hydroxide solution with a mass percent concentration of 20%. 0.25 g of Ni-Yb-Al triple-acting catalyst was added followed by three nitrogen substitutions to remove air. The hydrogen pressure was controlled at 0.2 MPa and the reaction temperature was maintained at 25-30 °C until the reaction pressure decreased significantly, indicating the completion of the reaction. Upon completion of the reaction, the catalyst was recovered by filtration. The filtrate was adjusted to pH 3 with concentrated hydrochloric acid to precipitate the target product 3,5-diaminobenzoic acid. The solid product was collected by filtration, washed with water and finally dried under vacuum to give 36.5 g of 3,5-diaminobenzoic acid in 98.8% yield and 98.9% HPLC purity. The retention time of the product was consistent with the standard control.
Purification Methods
Crystallise the acid from water. The dihydrochloride has m 226-228o(dec). [Beilstein 14 H 453, 14 III 1179, 14 IV 1304.]
References
[1] Patent: CN105949076, 2016, A. Location in patent: Paragraph 0025; 0026; 0031; 0036; 0040; 0045; 0053
[2] Journal of the Iranian Chemical Society, 2014, vol. 11, # 6, p. 1587 - 1592
[3] Synthetic Communications, 2000, vol. 30, # 20, p. 3639 - 3644
[4] Indian Journal of Chemistry - Section B Organic and Medicinal Chemistry, 2000, vol. 39, # 9, p. 709 - 711
[5] Synthetic Communications, 2003, vol. 33, # 2, p. 281 - 289
