Pyrazolones
3 H -pyrazol-3-one
4 H -pyrazol-4-one
In chemistry, pyrazolones are the representatives of a group of organic compounds that belong to the heterocycles . They are derived from an additional keto group enacting pyrazole from.
The two basic compounds, 3 H -pyrazol-3-one and 4 H -pyrazol-3-one , have practically no meaning.
In a broader sense, the dihydropyrazolones are also counted among the pyrazolones, the derivatives of which can be used in a variety of ways.
synthesis
Many pyrazolones are synthetically accessible through the condensation of hydrazines and β-keto carbonyl compounds . One of the first syntheses of this kind was carried out by Ludwig Knorr in 1887 and obtained from phenylhydrazine and acetoacetic ester after subsequent methylation of the intermediate product phenazone .
Dihydropyrazolones
The dihydropyrazolones are formally derived from the pyrazolones by hydrogenation of a double bond . Here, too, the unsubstituted parent compounds are of no practical importance.
1,2-dihydro-3 H -pyrazol-3-one (2,3-dihydro-1 H -pyrazol-3-one)
2,4-dihydro-3 H -pyrazol-3-one (4,5-dihydro-1 H -pyrazol-5-one)
The dihydropyrazolones are subject to the lactam-lactim tautomerism and can therefore also be regarded as pyrazolols .
use
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Pigment Yellow 10 , a dihydropyrazolone derivative of 2,4-dichloroaniline , is used for road markings in the USA . |
Dihydropyrazolone derivatives, especially phenazone derivatives such as propyphenazone or metamizole , act as analgesics , anti-inflammatory drugs and antipyretics and form the active substance group of pyrazolone non-opioid analgesics .
Some dihydropyrazolones are used as pigments ( pyrazolone pigments such as Pigment Yellow 10 ) and as components for the synthesis of azo dyes (such as tartrazine , flavazine L ).
Phenidone (1-phenyl-3-pyrazolidinone) was used as a developer in black and white photography .
literature
- Entry to pyrazolones. In: Römpp Online . Georg Thieme Verlag, accessed on August 19, 2016.
- Pyrazolones . In: Lexicon of Chemistry . Spektrum Akademischer Verlag, Heidelberg 1998 ( Spektrum.de [accessed on August 20, 2016]).
- Walter Krohs, Otto Hensel: Pyrazolone and Dioxopyrazolidine . In: drug research. Supplement 11. Editio Cantor, Aulendorf i. Wuertt . 1961, OCLC 14594801 , PMID 14035918 .
Web links
Individual evidence
- ↑ Ruedi origin: Syntheses in the pyrazolone series. (PDF) Dissertation, ETH Zurich, 1948.
- ↑ Ludwig Knorr: Synthetic experiments with the acetoacetic ester . In: Justus Liebig's Annals of Chemistry . tape 238 , no. 1-2 , 1887, pp. 137-219 , doi : 10.1002 / jlac.18872380107 .