Efficient synthesis of novel 4-benzoyl-7-thioxo-4,6,7,8-tetrahydro-2H- pyrimido[5,4-e][1,3]oxazine-2,5(3H)-diones via one-pot three-component reaction under thermal and microwave conditions

Concise and attractive synthesis of a new class of 4-benzoyl-7-thioxo-4,6,7,8-tetrahydro-2H-pyrimido[5,4-e][1,3]oxazine-2,5(3H)-diones was attained with impressive yields, by means of a convenient and elegant condensation reaction between thiobarbituric acid and aryl glyoxals in the presence of N-methyl urea in EtOH under reflux and microwave conditions. Some specific merits of the current procedure, including availability of the starting materials, low reaction time, high reaction yield, operational simplicity, no harmful by-products, and the isolated product is in pure form. Structures of all the freshly synthesized products have been deduced by their FT-IR, 1H-NMR, 13C-NMR, and elemental analysis.