[NH2:1][C:2]1[C:10]([F:11])=[CH:9][C:5]([C:6]([OH:8])=[O:7])=[C:4]([F:12])[CH:3]=1.[CH2:13](O)[CH3:14].O.C(=O)(O)[O-]>Cl>[NH2:1][C:2]1[C:10]([F:11])=[CH:9][C:5]([C:6]([O:8][CH2:13][CH3:14])=[O:7])=[C:4]([F:12])[CH:3]=1A solution of 4-amino-2,5-difluorobenzoic acid (intermediate 137; 2.7 g; 0.015 mol) in hydrogen chloride 1.25 mL in ethanol (91 mL, 0.113 mol) was stirred for 24 hours at 60° C. The solvent was removed under reduced pressure and the crude obtained was treated with water and solid bicarbonate to obtain a basic pH, after few minutes stirring an extraction with ethyl acetate was done. The organic layer was washed with brine, dried and the solvent was removed under reduced pressure to give the title compound as a white solid (92%), which was used in the next step without further purification.
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