2-Propenoic acid, 2-cyano-3-ethoxy-, ethyl ester → ethyl 5-amino-1-(tert-butyl)-1H-pyrazole-4-carboxylate

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Reaction Steps

A solution of tert-butylhydrazine monohydrochloride (13.9 g, 111.55 mmol), sodium acetate (11.44 g, 139.43 mmol) and ethyl 2-(ethoxymethylene)-2-cyanoacetate (19 g, 112.31 mmol) in ethanol (130 mL) was heated under reflux for 20 hr. Ethanol was evaporated under reduced pressure, and ethyl acetate was added to the residue. The solution was washed with aqueous sodium hydrogen carbonate solution and saturated brine and dried, and the solvent was evaporated under reduced pressure. The residue was purified by silica gel column chromatography (solvent gradient; 2→35% ethyl acetate/hexane) to give ethyl 5-amino-1-tert-butyl-1H-pyrazole-4-carboxylate (24 g, 111.55 mmol, 102%) as a pale-yellow oil.

Provenance & Evidence