反应详情

温度

-78 °C

Under an argon atmosphere, 5.00 g (25.0 mmol) of 1-methyl-3-pentafluoroethyl-1H-pyrazole are initially introduced into diethyl ether and the solution is cooled to −78° C. 11.1 ml (27.7 mmol) of 2M lithium diisopropylamide solution in tetrahydrofuran/heptane are added dropwise and, at −30° C. and with vigorous stirring, 450 g of crushed dry ice are added. When the evolution of gas has stopped, the reaction mixture is admixed with 235 ml of water and adjusted to pH 11 with 1M 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 of the solvent on a rotary evaporator under reduced pressure gives 1.20 g of 1-methyl-3-pentafluoroethyl-1H-pyrazole-5-carboxylic acid (18%) as a solid.

1. additionare added
2. extractionThe alkaline solution is extracted three times with ethyl acetate
3. extractionThe aqueous phase is extracted three times with ethyl acetate
4. dry with materialthe organic phase is dried over sodium sulphate
5. distillationDistilling of the solvent on a rotary evaporator under reduced pressure