Heterocyclic Synthesis from the Reaction of Aryl Cyanate with Malonyl Chloride and Bromomalonyl Chloride

Abstract

Substituted aromatic cyanate reacts with malonyl chloride to yield 7-chloro-2-aryloxy-4H,5H-pyrano[3,4-e][1,3]oxazine-4,5-dione (3). Water reacts with 7-chloro-2-phenoxy-4H,5H-pyrano[3,4-e][1,3]oxazine-4,5-dione (3a), producing phenyl (6-chloro-4-hydroxy-2-oxo-2H-pyran-3-yl) carbonylcarbamate (8). Compound 3a reacts with morpholine in the presence of anhydrous potassium carbonate to yield phenyl (4-hydroxy-6-morpholin-4-yl-2-oxo-2H-pyran-3-yl)carbonylcarbamate (9). Product 9 was also produced from the reaction of compound 8 with morpholine. Substituted aromatic cyanate induces the self-condensation of bromomalonyl chloride, yielding 3,5-dibromo-6-chloro-4-hydroxy-2-oxo-3,4-dihydro-2H-pyran-3-carboxylic acid chloride (intermediate 14) which then cyclized and produced 6-bromo-7-chloro-2-aryloxy-4H,5H-pyrano-[3,2-e][1,3]oxazine-4,5-dione (4-pyrano-oxazine) (15) and not the expected 8-bromo-7-chloro-2-aryloxy-4H,5H-pyrano-[3,4-e][1,3] oxazine-4,5-dione (16).