General procedure for the synthesis of 3-chloro-4-aminobenzoic acid from methyl 4-amino-3-chlorobenzoate:
1. Saponification reaction: 4-amino-3-chlorobenzoic acid methyl ester (21.6 mmol) was dissolved in ethanol (25 mL) and 1M NaOH aqueous solution (25 mL), and heated to reflux for 2 hours.
2. Post-treatment: after completion of the reaction, the organic solvent was removed by evaporation and the pH of the reaction solution was adjusted to 4 with acid.
3. Isolation and purification: The precipitate was collected by filtration, washed with water and subsequently dried under vacuum to obtain the target product 3-chloro-4-aminobenzoic acid.
Yield: 92%.
1H NMR (D6-DMSO) δ: 6.15 (s, 2H), 6.79 (d, 1H), 7.59 (dd, 1H), 7.71 (d, 1H), 12.37 (br s, 1H).
