Acetonitrile → 3-n-Butylureido-1-(p-sulfophenyl)-5-pyrazolone Triethylamine Salt

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Reaction Steps

Into 30 ml of acetonitrile were dissolved 15.9 g of ethylβ-amino-β-ethoxy acrylate and 10 g of n-butyl isocyanate, and the system then allowed to stand at room temperature for 3 days. Into a mixed solution of 50 ml of methanol. 50 ml of triethylamine and 50 ml of glacial acetic acid was dissolved 18.8 g of p-sulfophenyl hydrazine, to which was slowly added the above ester reaction solution. The resulting solution was allowed to stand at room temperature for 7 days and then concentrated under reduced pressure. The concentrated residue was dissolved by adding 50 ml of ethanol containing 35% by wt. hydrogen chloride thereto. On standing the solution so obtained in a refrigerator for one night, crystals precipitated. The crystals were collected and recrystallized from ethanol, whereupon 26.5 g of needle-like crystals of the objective compound of a melting point of 174° to 176° C. was obtained.

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