Structure and synthesis
Pyrazolone can exist in 3 isomers: 3-pyrazolone, 4-pyrazolone, and 5-pyrazolone. These isomers can interconvert via lactam–lactim and imine–enamine tautomerism; these conversion often display photochromism. For pyrazolone derivatives, the 5-pyrazolone form can be stabilized with N-alkyl or N-aryl substituents.
Pyrazolones are amongst the oldest synthetic pharmaceuticals, starting with the introduction of antipyrine (phenazone) in 1880's. The compounds generally act as analgesics and include dipyrone (Metamizole), aminopyrine, ampyrone, famprofazone, morazone, nifenazone, piperylon and propyphenazone. Of these dipyrone is perhaps the most widely used.
Pyrazolone groups are present in several important dyes. They are commonly used in commination with azo groups to give a sub-family of azo dyes; sometimes referred to as azopyrazolones (tartrazine, orange B, mordant red 19, yellow 2G).
Pyrazolones have been studied as ligands.
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- Brune, Kay (December 1997). "The early history of non-opioid analgesics". Acute Pain. 1 (1): 33–40. doi:10.1016/S1366-0071(97)80033-2.
- CASAS, J; GARCIATASENDE, M; SANCHEZ, A; SORDO, J; TOUCEDA, A (June 2007). "Coordination modes of 5-pyrazolones: A solid-state overview". Coordination Chemistry Reviews. 251 (11-12): 1561–1589. doi:10.1016/j.ccr.2007.02.010.
- Pyrazolones at the US National Library of Medicine Medical Subject Headings (MeSH)
- Pubchem - 3-Pyrazolone
- Pubchem - 5-Pyrazolone
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