Aliphatic azidonitriles separated by three or four carbon atoms undergo facile Lewis acid- induced cycloadditions to give bicyclic tetrazoles, even at 0° C. Extension to 3-azido-2-aryl- 1, 3-dioxolanes and the corresponding 1, 3-dioxanes in the presence of TMSCN and BF3⊙ OEt2 leads to a series of diversely functionalized novel oxabicyclic tetrazoles. The reactions represent new aspects of proximity-assisted dipolar cycloadditions that afford ...