Carbon Dioxide → 1-methyl-3-pentafluoroethyl-1H-pyrazole-5-carboxylic acid

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Reaction Conditions

Reaction Steps

Under an argon atmosphere, 5.00 g (24.99 mmol) of 1-methyl-3-pentafluoroethyl-1H-pyrazole are initially introduced in diethyl ether and the solution is cooled to −78° C. 11.09 ml (27.73 mmol) of 2M lithium diisopropylamide solution in THF/heptane are added dropwise and, at −30° C. with vigorous stirring, 450 g of crushed dry ice are added. When the evolution of gas has finished, the reaction mixture is admixed with 235 ml of water and adjusted to a pH of 11 with 1N sodium hydroxide solution. The alkaline solution is extracted three times with ethyl acetate and then adjusted to pH 2 with 1N hydrochloric acid. The aqueous phase is extracted three times with ethyl acetate and the organic phase is dried over sodium sulphate. Distilling off the solvent on a rotary evaporator under reduced pressure gives 1.20 g (17.75% of theory) of 1-methyl-3-pentafluoroethyl-1H-pyrazole-5-carboxylic acid as a solid.

Provenance & Evidence