Cl([O-])=O.[Na+].O.P([O-])(O)(O)=O.[Na+].[OH:12][C:13]1[C:20]([C:21]([F:24])([F:23])[F:22])=[CH:19][CH:18]=[C:17]([CH3:25])[C:14]=1[CH:15]=[O:16].CC(=CC)C.S([O-])([O-])(=[O:33])=S.[Na+].[Na+].Cl>C(O)(C)(C)C.O1CCOCC1>[OH:12][C:13]1[C:20]([C:21]([F:22])([F:23])[F:24])=[CH:19][CH:18]=[C:17]([CH3:25])[C:14]=1[C:15]([OH:33])=[O:16]After an aqueous solution (40 ml) of sodium chlorite (6.0 g, 66.3 mmol) and sodium dihydrogenphosphate monohydrate (6.0 g, 43.5 mmol) was added dropwise to a solution of 2-hydroxy-6-methyl-3-(trifluoromethyl)benzaldehyde (4.65 g, 22.8 mmol) obtained in Example (28-2) in a mixture of tert-butyl alcohol (90 ml), 1,4-dioxane (30 ml) and 2-methyl-2-butene (30 ml), the mixture was stirred at room temperature for 1 hour. After the reaction mixture was cooled with ice and a 5% aqueous sodium thiosulfate solution was added thereto, the mixture was poured into 0.5N hydrochloric acid and extracted with ethyl acetate (twice). The organic layer was successively washed with water and a saturated aqueous NaCl solution and dried with anhydrous sodium sulfate. The residue obtained by removing the solvent under reduced pressure was crystallized using ethyl acetate and n-hexane to give 2-hydroxy-6-methyl-3-(trifluoromethyl)benzoic acid as a colorless compound (4.21 g, yield: 84%).
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