5- Substituted-l,3,4-oxadiazolin-2-ones

Substituted-l,3,4-oxadiazolin-2-ones 178 are synthesized by the oxidation of carbo-/-butoxyhydrazones 177 of aromatic aldehydes with IBD. In some cases, in addition to 178, 5-acetoxy-l,3,4-oxadiazoIes 179 are also obtained. The oxidation of ethoxycarbonyl hydrazones 180 affords 2-ethoxy-l,3,4-oxadiazoles 181 (86JHC945) (Scheme 48). 

---