4-Arylazo-5-imino-3-pyrazolidinones

Amino-5-imino-3-pyrazolidinones have been synthesized by reduction of the corresponding oximes.644,1339 Such amines form ureas and thioureas by reaction with potassium cyanate in acid solution and with phenyl isothiocyanate.644 4-Arylimino-5-imino-3-pyrazolidinones have been prepared by reaction of the 5-imino-3-pyrazolidinones with p-amino-A.-AT-diethylaniline in the presence of silver salts as oxidizing agents (eq. 172).244,519,1255,1538 4-Arylazo-5-imino-3-pyrazolidinones have most frequently been prepared by reaction of 5-imino-3-pyrazoli-dinones with aryldiazonium chlorides, as is usual for the preparation of similar compounds.591,594,920,1087,1255,1339,1539,1649 One such compound has been prepared by the Curtius rearrangement of the corresponding 4-arylazo azide.594... 

Amino-5-imino-3-pyrazolidinones react with formaldehyde at the 4-amino group giving methylol derivatives.644 The 4-arylimino derivatives are reduced catalytically to give 4-arylamino analogs.1538 An interesting reaction of the 4-arylazo-5-imino-3-pyrazolidinones is the replacement of the 4-arylazo group by arylimino (eq. 272).1255 1296... 

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