Trifluoroacetic acid → ethyl 5-amino-1-(2-fluorobenzyl)-1H-pyrazole-3-carboxylate

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Reaction Steps

111.75 g (75 ml, 0.98 mol) of trifluoroacetic acid are added to 100 g (0.613 mol) of the sodium salt of ethyl cyanopyruvate (preparation in analogy to Borsche and Manteuffel, Liebigs Ann. 1934, 512, 97) in 2.51 of dioxane under argon with efficient stirring at room temperature, and the mixture is stirred for 10 min, during which most of the precursor dissolves. Then 85.93 g (0.613 mol) of 2-fluorobenzyl-hydrazine are added, and the mixture is boiled overnight. After cooling, the sodium trifluoroacetate crystals which have separated out are filtered off with suction and washed with dioxane, and the crude solution is reacted further.

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