Heterocyclic syntheses with malonyl chloride. 15. 7-Chloro-3,4-dihydro-4,5-dioxo-3-aryl(or-alkyl)-2-thio-2H,5H-pyrano[3,4-2-e]-1,3-oxazine from aryl or alkyl isothio-cyanates and their degradation with morpholine and ethanol

TLDR: The pyrano oxazine 1 react stepwise with morpholine undergoing replacement of the 7-chloro substituent yielding the 7morpholino analogue (4), then the pyrone ring was opened producing 5-morpholine carbonyl-4-oxo-3-substituted phenyl-2-thio-1,3-oxazine-6-ylacetomorpholid (5).

Abstract: Substituted aromatic isothiocyanates with malonyl chloride yield 7-chloro-3-substituted-3,4-dihydro-4,5-dioxo-2-thio-2H,5H-pyrano [3,4-e]-1,3-oxazine (1). Alkyl isothiocyanates with malonyl chloride yield a mixture of 7-chloro-3-alkyl-2-thio pyranooxazine (2) and the 2-oxo-analogue (3). The pyrano oxazine 1 react stepwise with morpholine undergoing replacement of the 7-chloro substituent yielding the 7-morpholino analogue (4), then the pyrone ring was opened producing 5-morpholino carbonyl-4-oxo-3-substituted phenyl-2-thio-1,3-oxazine-6-ylacetomorpholid (5). Finally the oxazine ring was opened yielding 2-substituted phenyl carbomyl-3-morpholino-N,N-glutaconoyldimorpholine (6). Ethanol react with compound 1 at any molar ration causing the opening of the pyrone ring and retain the oxazine ring. Mass spectra. 1H-n.m.r., u.v. and i.r. spectroscopic data provided information about the fine structures of the products.