Intramolecular cyclization of N′-chloroacetylsalicylhydrazide

Treatment of N′-chloroacetylsalicylhydrazide (I) with sodium hydroxide in dimethylformamide produces an intramolecular cyclization. Of all theoretically possible reactions, only one proceeds to give 5,6-dihydro-2-o-hydroxyphenyl-4H-1,3,4-oxadiazin-5-one (II). No formation of the 1,4,5-benzoxadiazocin-3,6-dione (III) is detected. The structure of II, as well as of its acetylation, methylation and hydrolysis derivatives are discussed.