Pyrazolone is 5-membered
heterocycle containing two adjacent
nitrogen atoms. It can be viewed as a derivative of
pyrazole possessing an additional
carbonyl (C=O) group. Compounds containing this functional group are useful commercially in
analgesics and dyes.[1]
Structure and synthesis
Pyrazolone can exist in two isomers: 3-pyrazolone and 4-pyrazolone.
Chemical structures of 3-pyrazolone (left) and 4-pyrazolone (right)
These isomers can interconvert via lactam–lactim and imine–enamine
tautomerism; these conversion often display
photochromism. For pyrazolone derivatives, the 3-pyrazolone isomer can be stabilized with N-alkyl or N-aryl substituents.
Many pyrazolones are produced by functionalization of preformed pyrazolones.
Applications
Pharmaceuticals
This section is missing information about safety profile of analgesics (which ones are withdrawn and whether there is a common theme in adverse effects). Please expand the section to include this information. Further details may exist on the
talk page.(August 2022)
The basic structure has been also used in a number of newer drugs of other effects.[5]Edaravone is useful for prevention and/or therapy of arterial wall injury.[6]Eltrombopag is used to address low blood platelet count.