Reaction of vinyl azides with nitrosyl tetrafluoroborate yields 1,2,5-oxadiazoles and 1,2,4-oxadiazoles depending on the structure of the azide. Reaction of 1,2-dialkyl vinyl azides with nitryl tetrafluoroborate gives 2-oxo-1,2,5-oxadiazoles in high yields whereas 1-aryl-2-alkyl vinyl azides gave moderate yields of 3-aryl-1,2,5-oxadiazoles and 5-aryl-1,2,4-oxadiazoles. Acyl chlorides condense with vinyl azides in the presence of aluminum chloride to yield oxazoles. Dimethyl acetylenedicarboxylate condenses with vinyl azides by cycloaddition of the azido function with the alkyne and by cycloaddition of the vinyl group with the alkyne. The latter process occurs only under the influence of AlCl3. The observed reactions are viewed as involving the participation of vinyl azides as N-diazoenamines.