1,2,3-Triazole is one of a pair of

isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formula – that is, the same number of atoms of each element (chemistry), element – but distinct arrangements of atoms in space. ''Isomerism'' refers to the exi ...

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

s with

molecular formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as paren ...

CHN, called

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, which have a five-membered ring of two carbon atoms and three nitrogen atoms. 1,2,3-Triazole is a basic

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 ...

heterocycle.

Synthesis

The unsubstituted ring can be produced by an oxidative coupling of glyoxal,

hydrazine Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly hazardous unless handled in solution as, for example, hydraz ...

and

sodium nitrite Sodium nitrite is an inorganic compound with the chemical formula . It is a white to slightly yellowish crystalline powder that is very soluble in water and is hygroscopic. From an industrial perspective, it is the most important nitrite sa ...

. A wide range of methods exist for forming substituted 1,2,3-triazoles. These include the Banert cascade or the azide alkyne Huisgen cycloaddition in which an

azide In chemistry, azide (, ) is a linear, polyatomic anion with the formula and structure . It is the conjugate base of hydrazoic acid . Organic azides are organic compounds with the formula , containing the azide functional group. The dominant ...

and an

alkyne \ce \ce Acetylene \ce \ce \ce Propyne \ce \ce \ce \ce 1-Butyne In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and n ...

undergo a 1,3-dipolar cycloaddition reaction. Under thermal conditions, regioselectivity is substrate dependent. Selectivity can be increased with metal catalysts, which have the added benefit of reacting without excessive or extensive heating. Copper catalyzed cycloadditions favor 1,4-disubstituted triazoles, Ruthenium catalyzed cycloaddition favor 1,5-disubstituted triazoles. This chemistry was expanded by Zhu et al. in 2018 wherein they report a two-step sequence from a terminal alkyne to 4-cyano 1,5-disubstituted triazoles.

Properties

The 2H-1,2,3-triazole tautomer is the major form in aqueous solution. It is a surprisingly stable structure compared to other organic compounds with three adjacent nitrogen atoms. However, flash vacuum

pyrolysis Pyrolysis is a process involving the Bond cleavage, separation of covalent bonds in organic matter by thermal decomposition within an Chemically inert, inert environment without oxygen. Etymology The word ''pyrolysis'' is coined from the Gree ...

at 500 °C leads to loss of molecular nitrogen (N) leaving a three-member

aziridine Aziridine is an organic compound consisting of the three-membered heterocycle . It is a colorless, toxic, volatile liquid that is of significant practical interest. Aziridine was discovered in 1888 by the chemist Siegmund Gabriel. Its deriva ...

ring. Certain triazoles are relatively easy to cleave due to ring–chain tautomerism. One manifestation is found in the Dimroth rearrangement.

Applications

1,2,3-Triazole finds use in research as a

bioisostere In medicinal chemistry, bioisosteres are chemical substituents or groups with similar physical or chemical properties which produce broadly similar biological properties in the same chemical compound. In drug design, the purpose of exchanging one b ...

for

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, ...

s and various

carboxylic acid In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an Substituent, R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl ...

derivatives in medicinal chemistry. Consequently it is an industrial building block for more complex chemicals, including pharmaceutical drugs such as mubritinib and tazobactam.

References

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