[F:1][C:2]1[CH:10]=[C:9]([O:11]C)[C:8](OC(C)C)=[CH:7][C:3]=1[C:4]([OH:6])=[O:5].[I-].[Li+].N1C(C)=CC(C)=[CH:21][C:20]=1[CH3:27]>[OH-].[Na+]>[F:1][C:2]1[CH:10]=[C:9]([OH:11])[C:8]([CH:20]([CH3:27])[CH3:21])=[CH:7][C:3]=1[C:4]([OH:6])=[O:5]A mixture of 2-fluoro-5-isopropoxy-4-methoxybenzoic acid (7.2 g) and lithium iodide (24 g) in collidine (120 mL) is heated at 150° C. overnight, cooled and dissolved in 2 N sodium hydroxide (200 mL) and washed with ethyl acetate (3×150 mL). The aqueous solution is acidified to pH 1 with concentrated hydrochloric acid and extracted with ethyl acetate (3×100 mL). The combined organic layers are dried (magnesium sulfate) and concentrated to give an oil. The oil is subjected to mplc on silica gel using petroleum ether:ethyl acetate (2:1 v/v) as eluent to give 2-fluoro-4-hydroxy-5-isopropylbenzoic acid (5.7 g). [NMR (DMSO): 7.32 (d, 1H, J=8 Hz), 6.67 (d, 1H, J=12 Hz), 4.47 (m, 1H), 1.24 (d, 6H, J=6 Hz)].
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