Heterocyclic transformations part 4: a facile transformation of 3-alkyl-6-methyl-1,3-oxazine-2,4(3H)-diones to 6-substituted 5-acetyluracils and 6-thioxo-1,3,5-triazine-2,4(1H,3H,5H)-diones

Abstract

3-Benzyl-6-methyl-1,3-oxazine-2,4(3H)-dione 1(R = CH₂Ph) reacts under phase-transfer catalytic conditions with amides and thioamides to give 6-substituted 5-acetyluracils and with malonamide to give a bicyclic pyridopyrimidine system. Similar reactions of 1 with thioureas provide 6-thioxo-1,3,5-triazine-2,4(1H,3H,5H)-diones, but with ureas, the substituents influence the mode of the reaction and the nature of the products. The synthetic scope and utility of these reactions has been examined.