Palladium-Catalyzed Synthesis of 1H-1,2,3-Triazoles

Significance

A palladium-catalyzed synthesis of 1H-1,2,3-triazoles from sodium azide and alkenyl bromides with yields ranging from 45-93% is reported. Among the ligands tested, the large bite angle bidentate XantPhos shows the highest activity, which is attributed to its ability to behave as a trans-chelating ligand. The optimized conditions for alkyl-substituted alkenyl bromides are different from aryl-substituted ones in that increased catalyst loading, higher temperature and more polar solvents are required for the former systems. Electronic variations of the aryl ring do not significantly affect the results of the reaction and sensitive functional groups such as ester, nitrile and halogen are compatible with the reaction conditions. A mechanism involving a [3+2] cycloaddition of the azide anion with a vinylpalladium species has been proposed.