Synthesis and structure of novel 4-arylhexahydro-1H,3H-pyrido[1,2-c]pyrimidine derivatives

A series of new 4-aryl-hexahydro-1H,3H-pyrido[1,2-c]pyrirnidine-1,3-dione derivatives 4a-k were prepared by catalytic hydrogenation of 4-aryl-1H,2H-pyrido[1,2-c]pyrirnidine-1,3-diones 3a-k. The structures of compounds were determined by ¹H and ¹³C nmr spectroscopy in solution. Steric hindrance caused twisting of the phenyl ring with respect to the pyridopyrimidine system, the effect was confirmed by X-ray diffraction.