Antipyretics, first synthetic drugs

Dihydro-3//-pyrazol-3-ones can be alkylated on the C-, N- or 0-atom depending on the substituents, reagent and reaction conditions. 5-Methyl-2-phenyl-2,4-dihydro-3//-pyrazol-3-one is methylated with iodomethane or dimethyl sulfate to give the 1,5-dimethyl derivative, which was one of the first synthetic drugs (1884, phenazone or antipyrine). It has antipyretic and antirheumatic action ... 

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