Synthesis and spectroscopic characterization of novel 2-amino-4,5,6,7-tetrahydro-3H-cyclopenta[d]pyrimidine and pyrimido[1,2-α]pyrimidine derivatives

2-Aminocyclopenta[d]pyrimidines 3a–c were achieved via a one-pot, three-component reactions of cyclopentanone 1, aromatic aldehyde and guanidine hydrochloride(1:2:1 molar ratio). Also, cyclization of 2,5-bis-(arylmethylidene)cyclopentanones 2 with guanidine hydrochloride(1:1 molar ratio) in methanol in the presence of sodium methoxide afforded cyclopenta-[d]pyrimidines 3. Compound 3c has been shown to be a useful building block for the synthesis of some novel pyrimido[1,2-a]pyrimidines 5, 7and 12. The structures of the newly synthesized compounds were confirmed on the basis of analytical and spectral data.