Synthesis of dimeric barbiturates

The dimerisation reaction of 1,3-diphenyl barbituric acid 1 and 1,3-dipheny l 2-thiobarbituric acid 3 has been studied. Alkaline solution of these acid s when treated with vinyl acetate, yielded 5,5'-(methyl)methylene-bis-(6-hy droxy-1,2,3,4-tetrahydro-1,3-diphenly)-2,4-dioxo pyrimidine 2 and 5,5'-(met hyl)methylene-bis-(6-hydroxy-1,2,3,4-tetrahydro-1,3-diphenly)-4-oxo-2-thio pyrimidine 4 respectively. The structures of these compounds have been conf irmed from their spectral and analytical data.