Cyanamide: a convenient building block to synthesize 4-aryl-2-cyanoimino-3,4-dihydro-1H-pyrimidine systems via a multicomponent reaction

4-Aryl-2-cyanoimino-3,4-dihydro-1H-pyrimidine derivatives were prepared using a multicomponent reaction by reacting a mixture of arene or heteroarenecarbaldehyde, 1,3-dicarbonyl compounds, and cyanamide under acidic conditions. The novelty of this approach derives from its use of cyanamide as a building block in a four-component Biginelli-type reaction. Varying the reaction conditions led to the formation of either N-(2-imino-6-phenyl-1,3,5-oxadiazinan-4-ylidene) cyanamide or 3,4-dihydropyrimidin-2(1H)-one. The type of heterocycle skeleton synthesized depends on the nature of the acid catalyst as well as the reaction conditions employed.