Azoles are a class of five-membered

heterocyclic compound A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic organic chemistry is the branch of organic chemistry dealing with the synthesis, proper ...

s containing a

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. ...

atom and at least one other non-carbon atom (i.e.

sulfur Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...

, or

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

) as part of the ring. Their names originate from the Hantzsch–Widman nomenclature. The parent compounds are

aromatic In organic chemistry, aromaticity is a chemical property describing the way in which a conjugated system, conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibits a stabilization stronger than would be expected from conjugati ...

and have two

double bond In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist betw ...

s; there are successively reduced analogs (azolines and azolidines) with fewer. One, and only one, lone pair of electrons from each

heteroatom In chemistry, a heteroatom () is, strictly, any atom that is not carbon or hydrogen. Organic chemistry In practice, the term is mainly used more specifically to indicate that non-carbon atoms have replaced carbon in the backbone of the molecular ...

in the ring is part of the aromatic bonding in an azole. Names of azoles maintain the prefix upon reduction (e.g., pyrazoline, pyrazolidine). The numbering of ring atoms in azoles starts with the heteroatom that is not part of a double bond, and then proceeds towards the other heteroatom.

Imidazole Imidazole (ImH) is an organic compound with the formula . It is a white or colourless solid that is soluble in water, producing a mildly alkaline solution. It can be classified as a heterocycle, specifically as a diazole. Many natural products, ...

and other five-membered aromatic heterocyclic systems with two nitrogens are extremely common in nature and form the core of many

biomolecules A biomolecule or biological molecule is loosely defined as a molecule produced by a living organism and essential to one or more typically biological processes. Biomolecules include large macromolecules such as proteins, carbohydrates, lipi ...

, such as

histidine Histidine (symbol His or H) is an essential amino acid that is used in the biosynthesis of proteins. It contains an Amine, α-amino group (which is in the protonated –NH3+ form under Physiological condition, biological conditions), a carboxylic ...

Compound classes

;Nitrogen only Imidazol.svg,

Pyrazol.svg,

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 ...

1,2,3-Triazole structure.svg,

1,2,3-Triazole 1,2,3-Triazole is one of a pair of isomeric chemical compounds with molecular formula CHN, called triazoles, which have a five-membered ring of two carbon atoms and three nitrogen atoms. 1,2,3-Triazole is a basic aromatic heterocycle. Synthesis ...

1,2,4-Triazole structure.svg, 1,2,4-Triazole 1H-Tetrazole structure.svg,

Tetrazole A tetrazole is a chemical synthesis, synthetic organic heterocyclic compound, consisting of a 5-member ring of four nitrogen atoms and one carbon atom. The name tetrazole also refers to the parent compound - a whitish crystalline powder with the f ...

Pentazol.svg,

Pentazole Pentazole is an aromatic molecule consisting of a five-membered ring with all nitrogen atoms, one of which is bonded to a hydrogen atom. It has the molecular formula . Although strictly speaking a homocyclic, inorganic compound, pentazole has ...

;N,O compounds Oxazol.svg,

Oxazole Oxazole is the parent compound for a vast class of heterocyclic compound, heterocyclic aromatic organic compounds. These are azoles with an oxygen and a nitrogen separated by one carbon. Oxazoles are aromatic compounds but less so than the thiaz ...

Isoxazol.svg,

Isoxazole Isoxazole is an electron-rich azole with an oxygen atom next to the nitrogen. It is also the class of compounds containing this ring. Isoxazolyl is the Valence (chemistry), univalent functional group derived from isoxazole. Occurrence Isoxazole ri ...

1,2,3-oxadiazole.svg, 1,2,3-oxadiazole
(unstable) 1,2,4-oxadiazole.svg, Oxadiazole
(1,2,4-Oxadiazole) 1,2,5-oxadiazole.svg,

Furazan Furazan, or 1,2,5-oxadiazole, is a heterocyclic aromatic organic compound consisting of a five-atom ring containing 1 oxygen and 2 nitrogen atoms. The furazan ring system is also found in the steroid furazabol. Furazan and its derivatives are ob ...

(1,2,5-oxadiazole) 1,3,4-oxadiazole.svg ,

1,3,4-Oxadiazole 1,3,4-Oxadiazole is a nitrogen and oxygen containing heterocycle, and one of the four isomers of oxadiazole. Derivatives 1,3,4-Oxadiazole itself is not commonly used in organic chemistry, but many of its derivatives are important. For example ...

;N,S compounds Thiazol.svg,

Thiazole Thiazole (), or 1,3-thiazole, is a 5-membered heterocyclic compound that contains both sulfur and nitrogen. The term 'thiazole' also refers to a large family of derivatives. Thiazole itself is a pale yellow liquid with a pyridine-like odor and the ...

Isothiazol - Isothiazole.svg,

Isothiazole Isothiazole, or 1,2-thiazole, is an organic compound consisting with the formula . The ring is unsaturated and features an S-N bond. The isomeric thiazole, where the S and N are not directly bonded are far more common. Isothiazones are produced ...

1,2,3-thiadiazole-2D-skeletal.png ,

Thiadiazole In chemistry, thiadiazoles are a sub-family of azole compounds, with the name ''thiadiazole'' originating from the Hantzsch–Widman nomenclature. Structurally, they are five-membered heterocyclic compounds containing one sulfur and two nitrogen ...

(1,2,3-Thiadiazole) 1,2,4-thiadiazole-2D-skeletal.png , 1,2,4-thiadiazole 1,2,5-thiadiazole-2D-skeletal.png , 1,2,5-thiadiazole 1,3,4-thiadiazole-2D-skeletal.png , 1,3,4-thiadiazole

Use as antifungal agents

The search for

antifungal An antifungal medication, also known as an antimycotic medication, is a pharmaceutical fungicide or fungistatic used to treat and prevent mycosis such as athlete's foot, ringworm, candidiasis (thrush), serious systemic infections such as ...

agents with acceptable toxicity profiles led first to the discovery of

ketoconazole Ketoconazole, sold under the brand name Nizoral, among others, is an antiandrogen, antifungal drug, antifungal, and antiglucocorticoid medication used to treat a number of fungal infections. Applied to the skin it is used for fungal skin inf ...

, the first azole-based oral treatment of systemic fungal infections, in the early 1980s. Later, triazoles

fluconazole Fluconazole is an antifungal medication used for a number of fungal infections. These include candidiasis, blastomycosis, coccidioidomycosis, cryptococcosis, histoplasmosis, dermatophytosis, and tinea versicolor. It is also used to pr ...

and

itraconazole Itraconazole, sometimes abbreviated ITZ, is an antifungal medication used to treat a number of fungal infections. This includes aspergillosis, blastomycosis, coccidioidomycosis, histoplasmosis, and paracoccidioidomycosis. It may be given ...

, with a broader spectrum of antifungal activity and improved safety profile were developed. In order to overcome limitations such as sub-optimal spectra of activity, drug-drug interactions, toxicity, development of resistance and unfavorable

pharmacokinetics Pharmacokinetics (from Ancient Greek ''pharmakon'' "drug" and ''kinetikos'' "moving, putting in motion"; see chemical kinetics), sometimes abbreviated as PK, is a branch of pharmacology dedicated to describing how the body affects a specific su ...

, analogues were developed. Second-generation

triazole A triazole is a heterocyclic compound featuring a five-membered ring of two carbon atoms and three nitrogen atoms with molecular formula C2H3N3. Triazoles exhibit substantial Isomer, isomerism, depending on the positioning of the nitrogen atoms w ...

s, including voriconazole, posaconazole and ravuconazole, are more potent and more active against resistant pathogens. For

wood preservation Wood preservation refers to any method or process, or even technique, used to protect the wood and extend its service life. Most wood species are susceptible to both biological (''biotic'') and non-biological (''abiotic'') factors that cause d ...

, other azoles such as propiconazole, tebuconazole and

cyproconazole Cyproconazole is an agricultural fungicide of the class of azoles, used on cereal crops, coffee, sugar beet, fruit trees and grapes, and peanuts, on sod farms and golf course turf and on wood as a preservative. It has been used against powdery ...

, are used as antifungal agents in several

wood Wood is a structural tissue/material found as xylem in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulosic fibers that are strong in tension and embedded in a matrix of lignin t ...

products or structures, with or without the addition of copper-containing compounds. Such azoles possess a good activity in solvents and water-based formulations, and are effective against wood-destroying, rot

fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

References

External links

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Nomenclature, IUPAC
{{Authority control Functional groups