Synthesis
b) Synthesis of 2-amino-4-trifluoromethylbenzoic acid: 250 g of 2-nitro-4-trifluoromethylbenzoic acid (1.06 mol) was dissolved in 1 liter of ethanol and 7.5 g of 5% palladium/carbon catalyst was added. The reaction mixture was subjected to hydrogenation under hydrogen pressure of 1-2.5 bar. During the reaction, the temperature was gradually increased from 10 °C to 104 °C. After 2 h, the hydrogenation reaction was completed. Subsequently, the catalyst was removed by filtration and the solvent was evaporated under reduced pressure to give 215 g (99% yield) of a light yellow solid product with a melting point of 174-176 °C.
References
[1] Patent: WO2006/108591, 2006, A1. Location in patent: Page/Page column 10; 66
[2] Patent: US2005/124681, 2005, A1. Location in patent: Page/Page column 16
[3] Patent: WO2009/96701, 2009, A2. Location in patent: Page/Page column 28
[4] Journal of Medicinal Chemistry, 1996, vol. 39, # 5, p. 1172 - 1188
[5] Patent: WO2006/125555, 2006, A2. Location in patent: Page/Page column 96
