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

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Reaction Steps

Under argon, 100 g (0.613 mol) of the sodium salt of ethyl cyanopyruvate (preparation analogously to Borsche and Manteuffel, Liebigs Ann. 1934, 512, 97) in 2.5 l of dioxane are admixed, with efficient stirring and at room temperature, with 111.75 g (75 ml, 0.98 mol) of trifluoroacetic acid, and the mixture is stirred for 10 min, during which a large proportion of the starting material dissolves. 85.93 g (0.613 mol) of 2-fluorobenzylhydrazine are then added, and the mixture is boiled overnight. After cooling, the precipitated sodium trifluoroacetate crystals are filtered off with suction and washed with dioxane, and the crude solution is reacted further.

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