Heterocyclic compounds based on maleic acid monoureide

The products of the bromination in water of maleic acid monoureide and its methyl ester have the 2-imino-5-bromocarboxy(carbomethoxy)methyl-4-oxazolidone structure. 2-Imino-5-bromocarboxymethyl-4-oxazolidone undergoes dehydrobromination in aprotic polar solvents to give 2-imino-5-carboxymethylidene-4-oxazolidone. In the presence of dry hydrogen chloride in dimethylacetamide the oxazole ring undergoes dehydrobromination and isomerization to an imidazole ring with the formation of 5-carboxymethylidenehydantoin. Methyl α-bromofumarate monoureide is formed when the oxazole ring of 2-imino-5-bromocarbomethoxymethyl-4-oxazolidone is opened with alkali.