Carbon Dioxide → 1-Methyl-3-(trifluoromethyl)-1H-pyrazole-5-carboxylic acid

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To a mixture of 8.71 g of 1-methyl-3-trifluoromethyl-1H-pyrazole and 130 ml of tetrahydrofuran was added dropwise 32 ml of a 2.0 mol/L lithium diisopropylamide solution in heptane/tetrahydrofuran/ethylbenzene at −78° C. The mixture of stirred at −78° C. for 2 hours and then poured into a mixture was dry ice and 50 ml of tetrahydrofuran. The mixture was stirred for 2 hours while allowing it to rise to around room temperature. Water and diethyl ether were poured into the reaction mixture. The aqueous layer was adjusted to pH 10-12 by an addition of a 2N aqueous sodium hydroxide solution, and then layers were separated. The resulting aqueous layer was washed with diethyl ether two times, adjusted to around pH 3 by an addition of 2N hydrochloric acid, and then extracted with methyl tert-butyl ether three times. The organic layers were combined, washed with an aqueous saturated sodium chloride solution, dried over magnesium sulfate, and concentrated under reduced pressure to obtain 8.19 g of 1-methyl-3-trifluoromethyl-1H-pyrazole-5-carboxylic acid of the formula:

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