Hydrochloric Acid → 3-Phenyl-4,5-dihydro-1H-pyrazole-5-carboxylic acid

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Reaction Steps

A mixture of 10.0 g of 3-benzoylacrylic acid, 1.8 g of hydrazine, and 3.7 g of potassium hydroxide in 30 ml. of aqueous ethanol (1:1) is stirred and heated at reflux for 2 hours. The cooled solution is treated with 5 ml of concentrated hydrochloric acid to pH 4.0 to precipitate 7.1 g of solid, melting point 180°-182° C. This material is dissolved in 40 ml of warm dimethylformamide and treated with 140 ml of methanol to crystallize 3.9 g of the title compound, melting point 199°-201° C.

Provenance & Evidence