Synthesis and Pharmacological Properties of N-Substituted-N '-(4,6-dimethylpyrimidin-2-yl)-Thiourea Derivatives and Related Fused Heterocyclic Compounds

A series of new N-Substituted-N'-(4,6-dimethylpyrimidin-2-yl)-thiourea derivatives (3a-d) and related fused heterocyclic compounds (4a-d) were synthesized using tetrabutylammonium bromide as phase transfer catalyst (PTC). N-[(2E)-5,7-dimethyl-2H-[1,2,4] thiadiazolo [2,3-a] pyrimidin-2-ylidene] derivatives (4a-d) were prepared by oxidative cyclization of 3a-d. The structures of these novel compounds were characterized by IR, H-1 NMR, C-13 NMR, mass spectrometry, and the elemental analysis. The crystal structures were determined from single crystal X-ray diffraction data. The results indicated that the compounds possessed a broad spectrum of activity against the tested microorganisms and showed higher activity against fungi than bacteria. Compounds 3d and 3a exhibited the greatest antimicrobial activity.