[OH-].[Na+].[Cl:3][C:4]1[C:13]([C:14]2[CH2:18][CH:17]([CH3:19])[O:16][N:15]=2)=[C:12]([S:20]([CH3:23])(=[O:22])=[O:21])[CH:11]=[CH:10][C:5]=1[C:6]([O:8]C)=[O:7]>CO>[Cl:3][C:4]1[C:13]([C:14]2[CH2:18][CH:17]([CH3:19])[O:16][N:15]=2)=[C:12]([S:20]([CH3:23])(=[O:21])=[O:22])[CH:11]=[CH:10][C:5]=1[C:6]([OH:8])=[O:7]A solution of 3.52 g (88 mmol) of sodium hydroxide, dissolved in 100 ml of methanol, was slowly added dropwise to a mixture of 15.00 g (45 mmol) of methyl 2-chloro-3-(5-methyl-4,5-dihydroisoxazol-3-yl)-4-methylsulfonylbenzoate and 200 ml of methanol. The suspension was stirred for 48 hours at room temperature. After the solvent had been distilled off, the residue was taken up in water, and the aqueous phase was washed three times with ethyl acetate. The aqueous phase was acidified with hydrochloric acid and extracted three times with ethyl acetate. The combined organic phases were subsequently washed to neutrality with water, dried and concentrated. This gave 13.20 g (92% of theory) of 2-chloro-3-(5-methyl-4,5-dihydroisoxazol-3-yl)-4-methylsulfonylbenzoic acid.
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