[F:1][C:2]([F:12])([F:11])[C:3](=O)[CH2:4][C:5]([O:7]CC)=O.Cl.[CH3:14][O:15][C:16]1[CH:21]=[CH:20][C:19]([NH:22][NH2:23])=[CH:18][CH:17]=1.Cl>CO>[CH3:14][O:15][C:16]1[CH:21]=[CH:20][C:19]([N:22]2[C:5]([OH:7])=[CH:4][C:3]([C:2]([F:1])([F:11])[F:12])=[N:23]2)=[CH:18][CH:17]=1A mixture of 5 g (27.2 mmol) of ethyl trifluoroacetoacetate, 4.76 g (27.2 mmol) of 4-methoxyphenylhydrazine hydrochloride, and 0.5 ml of conc. HCl in 60 ml of methanol was refluxed with stirring for 22 hours. After removing methanol in vacuo, toluene was added and the resulting mixture was refluxed for 20 hours and cooled. The mixture was diluted with aqueous sodium bicarbonate solution, extracted with ethyl acetate, and the organic layer was dried over sodium sulfate and concentrated in vacuo. The residue was recrystallized from methylene chloride/hexane and ethyl acetate/hexane to afford 3.7 g (53%) of 1-(4-methoxyphenyl)-3-trifluoromethyl-5-hydroxypyrazole as a tan solid.
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