Triazole

Triazole refers to a family of five-membered heteroaromatic rings containing three nitrogens. The three main isomeric forms are 1,2,3-triazole, 1,2,4-triazole, and 1,3,4-triazole. All share a planar, aromatic ring with two carbons and three nitrogens, and the hydrogen atoms and substituents vary with substitution. The rings are isosteric with other heterocycles and can act as hydrogen-bond acceptors; the nitrogen atoms influence the ring’s basicity and electronic properties.

1,2,3-Triazoles are especially associated with the azide–alkyne cycloaddition reaction. In the copper(I)-catalyzed variant (CuAAC), propargyl compounds react with organic azides to form 1,4-disubstituted 1,2,3-triazoles in high regioselectivity; ruthenium catalysts can give 1,5-disubstituted isomers. Other triazoles (1,2,4- and 1,3,4-triazoles) are typically prepared by cyclization of precursors such as amidrazones, hydrazide–carboxylate systems, or condensation reactions, providing a range of substitution patterns.

Triazoles are found in many biologically active compounds. They are components of antifungal drugs such as fluconazole and itraconazole and appear in various antiviral and anticancer agents. In medicinal chemistry, the triazole ring is valued as a bioisostere for amide or ether linkages and as a stable, metabolically robust linker.

Beyond medicine, triazoles serve as ligands in coordination chemistry and as functional groups in materials science, including polymers and click-assembled bioconjugates.