1.3.4- Oxadiazoles formation from tetrazoles

Two variations of the transformation of 3-acyltetrazoles into oxadiazoles are useful from a synthetic point of view. The first transformation involves the reaction of tetrazole with diketene. In the second, the sodium salt of the tetrazole is treated with oxalyl chloride. UV irradiation of some 3-amino-l,2,4-oxadiazoles leads to the formation of the corresponding 2-amino-l,3,4-oxadiazoles <1996CHEC-II(4)268>. 

The energetic 1,3,4-oxadiazole (22) is synthesized from the reaction of the tetrazole (20) with oxalyl chloride. In this reaction the tetrazole (20) undergoes a reverse cycloaddition with the expulsion of nitrogen and the formation of the 1,3-dipolar diazoalkane (21) which reacts with the carbonyl groups of oxalyl chloride to form the 1,3,4-oxadiazole rings. 

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