4-Arylazo-2- -4- pyrazol-3-ones

Boulton-Katritzky rearrangement, 5, 258 Pyrazol-5-one, 4-arylazo-reactions, 5, 262 Pyrazol-5-one, 4-arylidene-configuration, 5, 208... 

Ravindranath and co-workers studied the electrochemical behavior of 5-amino-2-phenyl-4-arylazo-l,2-dihydro-3//-pyrazol-3-one (90UC864) and 5-methyl-4-arylazo-2-(pyridin-2-ylcarbonyl)-2,4-dihydro-3//-pyrazol-3-(Mie (90IJC895). Similar studies were undertaken by Jain and Damodharan of pyrazol-3-ones 408a-f (95CJC176) (Scheme 94). The underlying rationale for this study on the electrochemical reduction of these biologically important pyrazol-3-ones is that it can lead to information on the reaction routes and mechanisms of biological redox reactions. 

Arylazo-3-pyrazolin-5-ones have been used as dyes. They form complexes with chromium which have good dyeing properties.1060 Miehaelis, Kotelmann and Drews984 report the reduction of 4-aryl-azo-3-pyrazolin-5-ones having no 1-substituent to pyrazoles by use of phosphorus pentasulfide (eq. 202). Reaction of such azo compounds... 

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