Pyrazolone

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.

The first synthesis of pyrazolones was reported in 1883 by Ludwig Knorr, via a condensation reaction between ethyl acetoacetate and phenylhydrazine.^[2]

Many pyrazolones are produced by functionalization of preformed pyrazolones.

Applications

Pharmaceuticals

Antipyrine (phenazone), the earliest pyrazolone based drug

Pyrazolones are amongst the oldest synthetic pharmaceuticals, starting with the introduction of antipyrine (phenazone) in 1880s.^[3]^[4] 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.^[3]^[5]

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.

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.^[1]

Ligands

Pyrazolones have been studied as ligands.^[7]

References

^ ^a ^b Kornis, Gabe I. (2000). "Pyrazoles, Pyrazolines, and Pyrazolones". Kirk-Othmer Encyclopedia of Chemical Technology. doi:10.1002/0471238961.1625180111151814.a01. ISBN 0471238961.
^ Knorr, Ludwig (July 1883). "Einwirkung von Acetessigester auf Phenylhydrazin". Berichte der Deutschen Chemischen Gesellschaft (in German). 16 (2): 2597–2599. doi:10.1002/cber.188301602194.
^ ^a ^b Brogden, Rex N. (1986). "Pyrazolone Derivatives". Drugs. 32 (Supplement 4): 60–70. doi:10.2165/00003495-198600324-00006. PMID 3552586. S2CID 2761563.
^ 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.
^ ^a ^b Zhao, Zefeng; Dai, Xufen; Li, Chenyang; Wang, Xiao; Tian, Jiale; Feng, Ying; Xie, Jing; Ma, Cong; Nie, Zhuang; Fan, Peinan; Qian, Mingcheng; He, Xirui; Wu, Shaoping; Zhang, Yongmin; Zheng, Xiaohui (2020). "Pyrazolone structural motif in medicinal chemistry: Retrospect and prospect". European Journal of Medicinal Chemistry. 186: 111893. doi:10.1016/j.ejmech.2019.111893. PMC 7115706. PMID 31761383.
^ Bailly, Christian; Hecquet, Paul-Emile; Kouach, Mostafa; Thuru, Xavier; Goossens, Jean-François (2020). "Chemical reactivity and uses of 1-phenyl-3-methyl-5-pyrazolone (PMP), also known as edaravone". Bioorganic & Medicinal Chemistry. 28 (10): 115463. doi:10.1016/j.bmc.2020.115463. PMID 32241621. S2CID 214766793.
^ 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.

External links

Pyrazolones at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
Pubchem - 3-Pyrazolone
Pubchem - 4-Pyrazolone

[KO-1] Kornis, Gabe I. (2000). "Pyrazoles, Pyrazolines, and Pyrazolones". Kirk-Othmer Encyclopedia of Chemical Technology. doi:10.1002/0471238961.1625180111151814.a01. ISBN 0471238961.

[2] Knorr, Ludwig (July 1883). "Einwirkung von Acetessigester auf Phenylhydrazin". Berichte der Deutschen Chemischen Gesellschaft (in German). 16 (2): 2597–2599. doi:10.1002/cber.188301602194.

[pharma1-3] Brogden, Rex N. (1986). "Pyrazolone Derivatives". Drugs. 32 (Supplement 4): 60–70. doi:10.2165/00003495-198600324-00006. PMID 3552586. S2CID 2761563.

[4] 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.

[Zhao-5] Zhao, Zefeng; Dai, Xufen; Li, Chenyang; Wang, Xiao; Tian, Jiale; Feng, Ying; Xie, Jing; Ma, Cong; Nie, Zhuang; Fan, Peinan; Qian, Mingcheng; He, Xirui; Wu, Shaoping; Zhang, Yongmin; Zheng, Xiaohui (2020). "Pyrazolone structural motif in medicinal chemistry: Retrospect and prospect". European Journal of Medicinal Chemistry. 186: 111893. doi:10.1016/j.ejmech.2019.111893. PMC 7115706. PMID 31761383.

[6] Bailly, Christian; Hecquet, Paul-Emile; Kouach, Mostafa; Thuru, Xavier; Goossens, Jean-François (2020). "Chemical reactivity and uses of 1-phenyl-3-methyl-5-pyrazolone (PMP), also known as edaravone". Bioorganic & Medicinal Chemistry. 28 (10): 115463. doi:10.1016/j.bmc.2020.115463. PMID 32241621. S2CID 214766793.

[7] 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.

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v t e Non-steroidal anti-inflammatory drugs (NSAIDs) (primarily M01A and M02A, also N02BA)
pyrazolones / pyrazolidines	Aminophenazone Ampyrone Azapropazone Clofezone Difenamizole Famprofazone Feprazone Kebuzone Metamizole Mofebutazone Morazone Nifenazone Oxyphenbutazone Phenazone Phenylbutazone Propyphenazone Sulfinpyrazone Suxibuzone^‡
salicylates	Aspirin (acetylsalicylic acid)^# Aloxiprin Benorylate Carbasalate calcium Diflunisal Dipyrocetyl Ethenzamide Guacetisal Magnesium salicylate Methyl salicylate Salsalate Salicin Salicylamide Salicylic acid (salicylate) Sodium salicylate
acetic acid derivatives and related substances	Aceclofenac Acemetacin Alclofenac Amfenac Bendazac Bromfenac Bufexamac Bumadizone Diclofenac Difenpiramide Etodolac Felbinac Fenclozic acid Fentiazac Indometacin Indometacin farnesil Isoxepac Ketorolac Lonazolac Mofezolac Oxametacin Prodolic acid Proglumetacin Sulindac Tiopinac Tolmetin Zomepirac^†
oxicams	Ampiroxicam Droxicam Isoxicam Lornoxicam Meloxicam Piroxicam Pivoxicam Tenoxicam
propionic acid derivatives (profens)	Alminoprofen Benoxaprofen^† Carprofen^‡ Dexibuprofen Dexketoprofen Fenbufen Fenoprofen Flunoxaprofen Flurbiprofen Ibuprofen^# Ibuproxam Indoprofen^† Ketoprofen Loxoprofen Miroprofen Naproxen Oxaprozin Pelubiprofen Piketoprofen Pirprofen Suprofen Tarenflurbil Tepoxalin^‡ Tiaprofenic acid Vedaprofen^‡ Zaltoprofen COX-inhibiting nitric oxide donator: Naproxcinod
n-arylanthranilic acids (fenamates)	Azapropazone Clonixin Etofenamate Floctafenine Flufenamic acid Flunixin Flutiazin Glafenine^† Meclofenamic acid Mefenamic acid Morniflumate Niflumic acid Tolfenamic acid
COX-2 inhibitors (coxibs)	Apricoxib Celecoxib (+tramadol) Cimicoxib^‡ Deracoxib^‡ Etoricoxib Firocoxib^‡ Lumiracoxib^† Mavacoxib^‡ Parecoxib Robenacoxib^‡ Rofecoxib^† Valdecoxib^†
other	Aminopropionitrile Benzydamine Chondroitin sulfate Diacerein Fluproquazone Glucosamine Glycosaminoglycan Hyperforin Nabumetone Nimesulide Oxaceprol Proquazone Superoxide dismutase / orgotein Tenidap
NSAID combinations	Ibuprofen/famotidine Ibuprofen/hydrocodone Ibuprofen/oxycodone Ibuprofen/paracetamol Meloxicam/bupivacaine Naproxen/diphenhydramine Naproxen/esomeprazole
Key: underline indicates initially developed first-in-class compound of specific group; ^#WHO-Essential Medicines; ^†withdrawn drugs; ^‡veterinary use.
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