[NH2:1][C:2]1[CH:3]=[C:4]([CH:8]=[C:9]([Cl:11])[CH:10]=1)[C:5]([OH:7])=[O:6].S(Cl)(Cl)=O.[CH3:16]O>>[CH3:16][O:6][C:5](=[O:7])[C:4]1[CH:8]=[C:9]([Cl:11])[CH:10]=[C:2]([NH2:1])[CH:3]=1To a stirred solution of 3-amino-5-chloro-benzoic acid (50 g, 291 mmol) in methanol (300 mL) was added thionyl chloride (45 mL, 605 mmol) dropewise at 0° C. Then the mixture solution was refluxed for 12 hours before cooling to room temperature. Then the reaction mixture was concentrated in vacuo and the residue was dissolved in ethyl acetate (500 mL), washed with saturated aqueous sodium bicarbonate solution (3×100 mL), dried over anhydrous sodium sulfate and concentrated in vacuo to afford 3-amino-5-chloro-benzoic acid methyl ester (54 g, quant.) as a pale-white solid: LC/MS m/e calcd for C8H8ClNO2 (M+H)+: 186.61, observed: 185.9.
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