In this study, a convenient procedure for the preparation of pyrazolo[1,5-c]pyrimidin7(1H)-one derivatives is described. The new pyrazolo[1,5-c]pyrimidin-7(1H)-one derivatives (2a, b) were synthesized from the cyclocondensation reaction of the compounds 1-amino-5-(4methoxybenzoyl)-4-(4-methoxyphenyl)pyrimidin-2(1H)-one (1a) and 1-amino-5-(4-methylbenzoyl)-4-(4-methylphenyl)pyrimidin-2(1H)-one (1b) with alpha-chloroacetone. The structures of the compounds (2a, b) were characterized by elemental analysis, FT-IR, H-1-NMR and C-13-NMR spectroscopic techniques. In addition to experimental study in order to find molecular properties, quantum-chemical calculations of the new pyrazolo[1,5-c]pyrimidin-7(1H)-one derivatives (2a, b) were carried out by using DFT/B3LYP method with the 6-311G(d,p) and 6-311++G(2d,2p) basic sets. Quantum chemical features such as HOMO, LUMO, HOMO-LUMO energy gap, chemical hardness, chemical softness, electronegativity, chemical potential, dipole moment etc. values for gas and solvent phase of neutral molecules were calculated and discussed.