Synthesis of 5-substituted 1H-tetrazoles by the copper-catalyzed [3+2] cycloaddition of nitriles and trimethylsilyl azide

The copper-catalyzed [3+2] cycloaddition between various nitriles and trimethylsilyl azide in DMF/MeOH produced the corresponding 5-substituted 1H-tetrazoles in good to high yields. It was proposed that the reaction proceeds through the formation in situ of a copper azide species and subsequent [3+2] cycloaddition with the nitriles. Furthermore, we found that a copper and triethylamine combined catalyst also promoted the cycloaddition of nitriles and trimethylsilyl azide to afford the 5-substituted 1H-tetrazoles at relatively low reaction temperatures. The copper azide species would be formed by reaction of the copper catalyst with Et₃N·HN₃ generated in situ.