Ethyl 2-chloroacetoacetate → 3-(Cyclopropylamino)-5-methyl-1H-pyrazole-4-carboxylic acid, ethyl ester hydrochloride

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Reaction Steps

A stirred slurry of 10.4 g (0.079 mole) of 4-cyclopropyl-3-thiosemicarbazide under nitrogen atmosphere was treated with 13 g (0.079 mole) of ethyl 2-chloroacetoacetate, stirred at ambient temperature for 1 hr, treated with 30 mL of 2N ethanolic hydrogen chloride and heated to reflux. The reaction mixture was allowed to cool to ambient temperature while stirring for ~72 hr. The sulfur residue was removed by filtration and the filtrate concentrated in vacuo to an orange oil which solidified. Recrystallization twice from acetone gave 7.4 g of large blade-like crystals, after drying for 2 hr at 98° C. under reduced pressure, mp 147°-148.5° C. The filtrates gave an additional 6 g of crude product. The 2 solids were combined ad recrystallized from methyl ethyl ketone to give 6.3 g of white crystalline power, mp 151°-152° C.

Provenance & Evidence