Triazole Your Tetrazoles

Key words

triazoles - regioselectivity - tetrazoles - photochemistry

Significance

Stewart, Harris, and Jamieson developed a one-step reaction to photochemically synthesize N2-aryl 1,2,3-triazoles 5 from 2,5-di­aryl tetrazoles 2. This method bypasses issues of regioselectivity by first preparing the appropriate N-arylated tetrazole, which under UV irradiation forms a nitrile imine intermediate 3 that dimerizes and rearranges to produce the appropriate N2-aryl 1,2,3-triazole.

Comment

Electron-donating substituents and dilute conditions led to improved yields of the triazoles, while electron-deficient N-aryl substituents led to poor or zero conversion. Previous studies of similar starting materials identified tetrazine as the final product, but the authors indicate that the only other compound isolated in their study was the Wanzlick dimer 4, which can be converted into the final triazole with additional UV irradiation.