Preparation of 1H-1,2,3-Triazoles by Cuprous Ion Mediated Cycloaddition of Terminal Alkyne and Sodium Azide

1H-1,2,3-triazoles can be prepared in good yield by the reaction of terminal alkyne and sodium azide in the presence of cuprous chloride at a temperature higher than 70 C. The alkyne is unactivated and the reaction has to be carried out under inert gas. At room temperature, the reaction first gives a Cu(I)-azide complex which is converted to a Cu-alkyne complex when the temperature is raised to higher than 70 C. The reaction of Cu(I)-alkyne complex and azide ion dissociated from or coordinated to Cu(I) then give