Heterocyclic transformations. Part 5: Studies in reactions of 6-methyl -l,3-oxazine-2,4(3H)-dione with arylamines—a facile synthesis of 1-aryl-6-methyluracils

Abstract

6-Methyl-1,3-oxazine-2,4(3H)-dione 1 reacts with 2 equiv. arylamines 3 at 150–160 °C to give 1 -aryl6-methyluracils 5 or 1-aryl-3-(3-aryliminobutanoyl)ureas 4. The latter—as well as mixtures of 1 and 3(2 equiv.) on refluxing, in isopentanol in some cases or in acetic acid in general–provide a facile synthesis of 5. The role of the stoichiometric excess of arylamines as against an equiv. of an alkylamine in similar reactions has been rationalized.