Step 1: Methyl 2-fluoro-5-hydroxybenzoate (30.0 g, 176.47 mmol, 1.0 eq.) was dissolved in a solvent mixture of THF and H2O (3:1 v/v, total 350 mL). To this solution was added LiOH-H2O (22.2 g, 529.41 mmol, 3.0 eq.) at room temperature. The reaction mixture was stirred at room temperature for 16 hours. After completion of the reaction, THF was removed by distillation under reduced pressure and the residue was diluted with cold water. The pH was adjusted to about 3 with 1.5 N HCl aqueous solution and the aqueous phase was extracted with EtOAc (3 x 250 mL). The organic phases were combined, washed with brine (150 mL), dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure to give 2-fluoro-5-hydroxybenzoic acid as an off-white solid (25.1 g, 91% yield).MS m/z: [M-1] = 155.4.
