Hydrochloric Acid → 7-[5-(3,5-Dichloro-phenyl)-5-trifluoromethyl-4,5-dihydro-isoxazol-3-yl]-benzo[1,2,5]thiadiazole-4-carboxylic acid

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Reaction Steps

To a solution of 7-[5-(3,5-dichlorophenyl)-5-trifluoromethyl-4,5-dihydro-isoxazol-3-yl]-benzo[1,2,5]thiadiazole-4-carboxylic acid methyl ester (Example 5.7) (4.01 g) in tetrahydrofuran (30 ml) was added aqueous sodium hydroxide (1M) (25.3 ml). The reaction mixture was stirred at ambient temperature for 1.5 hours. Aqueous hydrochloric acid (1M) (100 ml) was added and the mixture diluted with ethyl acetate (150 ml). After separation of the layers, the aqueous layer was extracted with ethyl acetate (2×75 ml). The combined organic layers were washed with water (75 ml) and brine (75 ml), dried over sodium sulfate and concentrated. The residue was purified by column chromatography (dichloromethane/methanol) to give 7-[5-(3,5-dichloro-phenyl)-5-trifluoromethyl-4,5-dihydro-isoxazol-3-yl]-benzo[1,2,5]thiadiazole-4-carboxylic acid (1.29 g) as yellow solid. 1H-NMR (DMSO-d6, 400 MHz): 13.67 (bs, 1H), 8.37-7.26 (m, 5H), 4.76 (d, 1H), 4.53 (d, 1H) ppm.

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