CCCCCC.C([Li])CCC.S1C=CC=C1C1C=C(C(F)(F)F)NN=1.ClC(OCC)=O.C(OC([N:37]1[C:41]([C:42]([F:45])([F:44])[F:43])=[CH:40][C:39]([C:46]2[S:50][C:49]([C:51]([O:53][CH2:54][CH3:55])=[O:52])=[CH:48][CH:47]=2)=[N:38]1)=O)C.C(OC(N1C(C2SC(C(OCC)=O)=CC=2)=CC(C(F)(F)F)=N1)=O)C.C(=O)(O)[O-].[Na+]>O.O1CCOCC1.C(O)C.C1COCC1>[F:44][C:42]([F:43])([F:45])[C:41]1[NH:37][N:38]=[C:39]([C:46]2[S:50][C:49]([C:51]([O:53][CH2:54][CH3:55])=[O:52])=[CH:48][CH:47]=2)[CH:40]=1An n-butyl lithium-n-hexane solution (1.6 M) was added to a mixture of 3-(2-thienyl)-5-trifluoromethyl-1H-pyrazole and THF at −60° C. or below, followed by stirring at 0° C. for 50 minutes. Ethyl chloroformate was added to the reaction solution at −60° C. or below. After stirring at −78° C. for 1 hour, it was subjected to purification in the usual way to give a mixture of ethyl 5-(1-ethoxycarbonyl-5-trifluoromethyl-1H-pyrazol-3-yl)thiophene-2-carboxylate and ethyl 5-(1-ethoxycarbonyl-3-trifluoromethyl-1H-pyrazol-5-yl)thiophene-2-carboxylate as a light yellow solid. Then, a mixture of this mixture with sodium bicarbonate, ethanol, 1,4-dioxane and water was stirred at room temperature for 3 days, and it was subjected to purification in the usual way to give ethyl 5-(5-trifluoromethyl-1H-pyrazol-3-yl)thiophene-2-carboxylate as colorless powder crystals. This was hydrolyzed with a base in the usual way to give 5-(5-trifluoromethyl-1H-pyrazol-3-yl)thiophene-2-carboxylic acid.
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