Heterocyclic syntheses with malonyl chloride. Part X. 2-Aryl- and -alkyl-thio-7-chloropyrano[3,4-e][1,3]oxazine-4,5-diones from thiocyanates, and their behaviour with amines

Abstract

Malonyl chloride reacts with alkyl and aryl thiocyanates yielding 2-alkyl-(or aryl-)thio-7-chloropyrano[3,4-e][1,3]oxazine-4,5-diones (2). These react stepwise with amines, undergoing replacement of the thio-group and then of the chloro-substituent. Next, the pyrone ring is opened and finally the oxazine ring, to yield N-substituted β-aminoglutaconamides having an α-allophanoyl side chain. The intermediate N-substituted 2,7-diaminopyrano-oxazinediones (some of which are tautomeric) suffer oxazine ring scission with amine hydrochloride and yield substituted 3-allophanoyl-4,6-diaminopyran-2-ones. The parent heterocycles (2), when treated with amine hydrochloride, retain the sulphur group and yield S-alkyl N-(diamino-oxopyran-3-carbonyl)thiocarbamates.