Synthesis
The general procedure for the synthesis of methyl 4-amino-3-methoxybenzoate from methyl 3-methoxy-4-nitrobenzoate was as follows: methyl 3-methoxybenzoate (83.0 g, 500 mmol) was added drop-wise to a mixture of acids consisting of HNO3 (65% by weight, 40 ml) and H2SO4 (70% by weight, 200 ml) at 0 °C. The reaction mixture was stirred overnight and poured into ice water. The mixture was filtered and the solid filter cake was washed with water (3 x 300 ml) to give 84.4 g of methyl 4-nitro-3-methoxybenzoate as a yellow solid in 80% yield. Next, an ethanol (1500 ml) solution of methyl 4-nitro-3-methoxybenzoate (84.4 g, 400 mmol) was stirred with Pd/C (10% Pd, 5.35 g) catalyst for 5 h under H2 atmosphere. After completion of the reaction, the catalyst was removed by Celite? filtration. The solvent was evaporated in vacuum to give an off-white solid. Finally, the off-white solid was recrystallized from methanol to give methyl 4-amino-3-methoxybenzoate (70.95 g, 392 mmol) in 98% yield.
References
[1] Patent: WO2010/56722, 2010, A1. Location in patent: Page/Page column 360
[2] Journal of Medicinal Chemistry, 2010, vol. 53, # 19, p. 7035 - 7047
[3] Journal of Medicinal Chemistry, 2013, vol. 56, # 5, p. 1843 - 1852
[4] Australian Journal of Chemistry, 1988, vol. 41, # 7, p. 1087 - 1097
[5] Patent: CN107698598, 2018, A. Location in patent: Paragraph 0065-0068
