p-Toluenesulfonic acid monohydrate → 5-Amino-1-(2,6-dichloro-4-trifluoromethylphenyl)-3-(1,2,4-oxadiazol-3-yl)-4-trifluoromethylsulfonylpyrazole

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Reaction Steps

5-Amino-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethylsulfonyl-3-pyrazolecarboxamide oxime (0.51 g, 1.87 mmol) was dissolved in 12 ml of trimethyl orthoformate and p-toluenesulfonic acid monohydrate (0.05 g) was added, and then the mixture was heated under reflux for 1 hour. Trimethyl orthoformate was distilled off and 80 ml of ethyl acetate was added to the residue. The ethyl acetate layer was washed twice with 50 ml of an aqueous saturated sodium hydrogencarbonate solution, and then washed once with 50 ml of an aqueous saturated sodium chloride solution. After drying over anhydrous magnesium sulfate, the solvent was distilled off to obtain a colorless crystal. This crystal was washed with a hexane-chloroform mixed solvent (volume ratio=2:1) to obtain 0.86 g (1.73 mmol) of the title compound as a colorless crystal. Yield 93%.

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