| 摘要 |
The preparation of 3-amino-1-phenylpyrazol-5-one by heating phenylhydrazine and a lower cyanoacetic acid alkyl ester in a polar solvent, using a lower alcoholate of an alkali metal as the condensation agent, leads to particularly high yields and quality, if the phenylhydrazine and 1 to 1.2 moles of the alcoholate are initially taken, the cyanoacetic ester is metered in and the reaction is carried out at 105 DEG to 140 DEG C., volatile alcohols which have been liberated from the ester and, if appropriate, from the alcoholate being distilled off at the reaction temperature. It is advantageous to employ the phenylhydrazine in an excess of up to about 200 mole % and to select, as the polar solvent, an alcohol or ether having a boiling point above 105 DEG C.
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