Heterocycles from saccharide hydrazones : Part I. Saccharide 1,3,4-oxadiazoles

Oxidation, with iodine-mercuric oxide, of acetylated saccharide aroylhydrazones and of aromatic aldehyde hydrazones yields 5-aryl-2-(polyacetoxyalkyl)-1,3,4-oxadiazoles and 2,5-diaryl-1,3,4-oxadiazoles, respectively. On de-O-acetylation, saccharide oxadiazole acetates rearrange to the tautomeric, cyclic iminolactones which, on reacetylation, regenerate the starting oxadiazoles. Attempted dehydration of saccharide acetyl- and benzoyl-hydrazones by treatment with boiling acetic anhydride under reflux resulted in the formation of peracetylated N,N-diacetylhydrazones and-N-acetyl-N-benzoylhydrazones, respectively.