Synthesis, oxidation and dehydrogenation of cyclic N,O- and N,S-acetals. Part III. Transformation of N,O-acetals: 3-acyl-1,3,4-oxadiazolines

✍ Scribed by László Somogyi

• Publisher: Journal of Heterocyclic Chemistry
• Year: 2007
• Tongue: English
• Weight: 724 KB
• Volume: 44
• Category: Article
• ISSN: 0022-152X
• DOI: 10.1002/jhet.5570440603

✦ Synopsis

Abstract

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Various aldehyde and ketone acylhydrazones are synthesized and, under acylating conditions, cyclized into 3‐acyl‐1,3,4‐oxadiazolines. The scope and limitations of these cyclizations and the possible side reactions (e.g. formation of the open‐chain N,O‐acylhydrazinocarbinols) are dissected. For the first time, simple, convenient and efficient dehydrogenations of 3‐acyl‐1,3,4‐oxadiazolines to oxadiazoles by treatment with potassium permanganate, or more conveniently, with ammonium cerium(IV) nitrate (CAN) are presented. CAN oxidation of 2,2‐disubstituted 3‐acyl‐1,3,4‐oxadiazolines, as well as that of aldehyde diacylhydrazones (open‐chain isomers of 2,5‐disubstituted 3‐acyl‐1,3,4‐oxadiazolines) regenerates the parent carbonyl compounds.