Heterocyclization of barbituric acid: Synthesis of novel condensed pyrimidines

A series of heterocyclic compounds was synthesized from barbituric acid. Reaction of barbituric acid with dibenzalacetone in acidic and basic medium afforded spiro compounds 3 and 4 and pyridopyrimidine derivatives 5, respectively. While, condensation reaction of barbituric acid with ethyl cyanoacetate and ethyl acetoacetate in presence of AcONH4, gave pyridopyrimidine derivatives 7 and 8, respectively. On the other hand, barbituric acid not condensed with dimedone to give compound 10, but gave 2-aminopyrimidine 9. Reaction of barbituric acid with urea and thiourea in presence of HCl and I2 gave pyrimidopyrimidne and thiazolopyrimidine derivatives 11-13, respectively. The structure of newly synthesized compounds was elucidated using spectral analysis (IR, 1H NMR and 13C NMR) and micro analysis.