Reaction #8666

Reaction equation

2-fluorobenzyl-hydrazine

trifluoroacetic acid

sodium

ethyl cyanopyruvate

→

Ethyl 5-amino-1-(2-fluorobenzyl)pyrazole-3-carboxylate

Solvents

dioxane

Conditions

Workup

1. 1
   workup.DISSOLUTIONdissolves
2. 2
   workup.WAITthe mixture is boiled overnight
3. 3
   TemperatureAfter cooling
4. 4
   Otherthe sodium trifluoroacetate crystals which have separated out
5. 5
   Filtrationare filtered off with suction
6. 6
   Washwashed with dioxane
7. 7
   Otherthe remaining crude solution is reacted further

Procedure

111.75 g (75 ml, 0.98 mol) of trifluoroacetic acid are added to 100.00 g (0.613 mol) of the sodium salt of ethyl cyanopyruvate (prepared in analogy to Borsche and Manteuffel, Liebigs Ann. 1934, 512, 97) while stirring efficiently in 2.5 l of dioxane at room temperature under argon, 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 remaining crude solution is reacted further.

Source