The triazoles are two isomers, namely 1,2,3-triazole or 1,2,4-triazole, with the formula C2H3N3. They are aromatic ring compounds similar to the azoles pyrazole and imidazole, but with an additional nitrogen atom in the ring structure. Like the azoles, triazoles are used in many antifungal drugs and fungicides, and the triazole-based drugs are more selective for fungi than mammalian cells than the azole-based antifungal compounds. Today, most substituted triazoles are produced by so-called click chemistry pioneered by K. Barry Sharpless and others (see below). Synonyms for both of these triazoles sometimes denote that a proton is attached in the 1-position, as for example, the naming 1H-1,2,3-triazole or 1,2,3-1H-triazole.
Synthesis of substituted 1,2,3-triazoles
Most substituted triazoles are synthesized by one of several click chemistry methods. One method uses palladium (Pd) catalysts to couple alkenyl halides and sodium azide to product 4-substituted-1,2,3-triazoles. This reaction also works with aromatic alkenyl halides. Click chemistry between azides and terminal aklynes, catalyzed by various copper reagents, can be used to synthesize 3,5-disubstituted-1,2,3-triazoles,.
A variety of 1,4-disubstituted-1,2,3-triazoles can be made economically and in an environmentally friendly manner, by reacting a secondary amine, propargyl halides and an azide together in water, under atmospheric oxygen with a copper catalyst.. Another method of 1,4-disubstituted-1,2,3-triazoles (not shown) uses no solvent. In this method, the cycloaddition of alkyl azides with enol ethers provides triazoles that are not amendable to synthesis using the coupling of azides with alkynes. A variety of other synthetic methods are available.
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- 1,2,3-triazole synthesis. Retrieved on 2008-05-17.