Hydrazine → (+/-)-4,5-Dihydro-3-(2-thienyl)-1H-pyrazole-5-carboxylic acid

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Reaction Steps

Potassium hydroxide (3.3 g) is dissolved in 100 cc of methanol and 9.1 g of 4-(2-thienyl)-4-oxocrotonic acid is added. To the resulting solution is added 2 g of hydrazine and the solution is refluxed for 2 hours. The methanol is removed and the viscous residue dissolved in 80 cc of water. The solution is made strongly acid with 20% HCl and a precipitate forms. It is filtered and air-dried to yield 8.1 g of the title compound, melting point 163°-165° C., dec. After recrystallization from ethanol the compound is constant melting at 171°-173° C., dec.

Provenance & Evidence