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Pyrazolone is 5-membered heterocycle containing two adjacent
The first synthesis of pyrazolones was reported in 1883 by 
Many pyrazolones are produced by functionalization of preformed pyrazolones.
Pyrazolones are amongst the oldest synthetic pharmaceuticals, starting with the introduction of antipyrine (phenazone) in 1880s. The compounds generally act as analgesics and include dipyrone (Metamizole), aminophenazone, ampyrone, famprofazone, morazone, nifenazone, piperylon and propyphenazone. Of these dipyrone is perhaps the most widely used.
The basic structure has been also used in a number of newer drugs of other effects. Edaravone is useful for prevention and/or therapy of arterial wall injury. Eltrombopag is used to address low blood platelet count.
Pubchem - 3-Pyrazolone
Pubchem - 4-Pyrazolone
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nitrogen
Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...
atoms. It can be viewed as a derivative of pyrazole
Pyrazole is an organic compound with the chemical formula, formula . It is a heterocycle characterized as an azole with a 5-membered ring of three carbon atoms and two adjacent nitrogen atoms, which are in Arene substitution pattern, ortho-substi ...
possessing an additional carbonyl
In organic chemistry, a carbonyl group is a functional group with the formula , composed of a carbon atom double bond, double-bonded to an oxygen atom, and it is divalent at the C atom. It is common to several classes of organic compounds (such a ...
(C=O) group. Compounds containing this functional group are useful commercially in analgesics and dyes.
Structure and synthesis
Pyrazolone can exist in two isomers: 3-pyrazolone and 4-pyrazolone. 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. :
The first synthesis of pyrazolones was reported in 1883 by Ludwig Knorr
Ludwig Knorr (2 December 1859 – 4 June 1921) was a German chemist. Together with Carl Paal, he discovered the Paal–Knorr synthesis, and the Knorr quinoline synthesis and Knorr pyrrole synthesis are also named after him. The synthesis in 1883 ...
, via a condensation reaction between ethyl acetoacetate and phenylhydrazine.
:
Many pyrazolones are produced by functionalization of preformed pyrazolones.
Applications
Pharmaceuticals
Pyrazolones are amongst the oldest synthetic pharmaceuticals, starting with the introduction of antipyrine (phenazone) in 1880s. The compounds generally act as analgesics and include dipyrone (Metamizole), aminophenazone, ampyrone, famprofazone, morazone, nifenazone, piperylon and propyphenazone. Of these dipyrone is perhaps the most widely used.
The basic structure has been also used in a number of newer drugs of other effects. Edaravone is useful for prevention and/or therapy of arterial wall injury. Eltrombopag is used to address low blood platelet count.
Dyes
Pyrazolone groups are present in several important dyes. They are commonly used in combination with azo groups to give a sub-family of azo dyes; sometimes referred to as azopyrazolones ( tartrazine, orange B, mordant red 19, yellow 2G). Acid Yellow 17, Acid Yellow 23 (tartrazine), Pigment Yellow 13, and Pigment Red 38 are produced on the multi-ton scale annually.Ligands
Pyrazolones have been studied as ligands.References
External links
*Pubchem - 3-Pyrazolone
Pubchem - 4-Pyrazolone
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