Synthesis
The general procedure for the synthesis of 4-amino-2-chlorobenzoic acid from 2-chloro-4-nitrobenzoic acid was as follows: firstly, NaBH4 (1 mmol) was added as a reducing agent to methanol at room temperature and the reaction was carried out for 2 h. Ag (+1) was reduced to Ag (0). Subsequently, the Ag/MMT catalyst was obtained by filtration separation. In a standard reaction procedure, 2-chloro-4-nitrobenzoic acid (0.1 mmol), KOH (0.15 mmol), isopropanol (3 mL) and 1.01 wt% of Ag/MMT catalyst (50 mg) were mixed and the reaction was stirred at room temperature until completion (the reaction progress was monitored by GC). Upon completion of the reaction, the catalyst was removed by filtration. The product was extracted with ethyl acetate and washed repeatedly (3-4 times) with water to remove residual KOH. finally, the solvent in the extract was evaporated to dryness under vacuum to afford the target product 4-amino-2-chlorobenzoic acid.
References
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[2] Journal of the Iranian Chemical Society, 2018, vol. 15, # 2, p. 281 - 291
[3] Patent: US2014/18368, 2014, A1. Location in patent: Paragraph 0162; 0187
[4] Journal of the American Chemical Society, 1949, vol. 71, p. 4154
[5] Chemische Berichte, 1891, vol. 24, p. 706