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 sodium salt of ethyl cyanopyruvate (prepared in analogy to Borsche and Manteuffel, Liebigs Ann. 1934, 512, 97) in 2.5 l of dioxane under argon with efficient stirring at room temperature, and the mixture is stirred for 10 minutes during which much of the precursor dissolves. Then 85.93 g (0.613 mol) of 2-fluorobenzylhydrazine are added, and the mixture is heated under reflux overnight. After cooling, the crystals of sodium trifluoroacetate which have separated out are filtered off with suction and washed with dioxane, and the solution is reacted further as it is.

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