Process for the manufacture of 3-amino-1-phenylpyrazol-5-one

US4410707A · kind A · utility

Assignee

• Hoechst GmbH · DE

Inventors

• Wolfgang Tronich
• Wolfgang Rieper · Frankfurt am Main, DE
• Peter Bohme · Kelkheim, DE

Key dates

• Filing date: Jul 21, 1981
• Grant date: Oct 18, 1983
• Expiry date: Jul 21, 2001

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07D231/52
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

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.degree. to 140.degree. 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.degree. C.