Abstract
A simple, economical, and green approach to the synthesis of 5,5'4(2,4-dichlorophenyl)methylene)bis(1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione) 4 using a tandem Aldol condensation-Michael addition process in aqueous diethylamine medium was described. The 3D structure of the latter was confirmed by single-crystal X-ray structure determination. The molecular structure of the titled compound was calculated using DFT B3LYP/6-311G(d,p) method. The calculated geometric parameters are in good agreement with the experimental data obtained from our reported X-ay structure. The two pyrimidinetrione rings have C16 and C20 atoms deviated significantly from the ring plane. The electronic spectra of the studied compound have been calculated using the TD-DFT method. The longest wavelength band (257.8 nm, f = 0.0276) occurs due to H -> L (86%) transition. The H-1 and C-13 NMR calculated chemical shifts using CIAO method showed good correlation with the experimental data. The molecular electrostatic potential (MEP) showed that the most reactive sites for electrophilic and nucleophilic attacks are the carbonyl oxygen (05) and the H21 atoms, respectively. The NBO calculations were performed to predict the natural atomic charges at the different atomic sites and to study the different intramolecular charge transfer (ICT) interactions occurring in the studied system. Interestingly, there is some delocalization of electron densities from the occupied sigma-type NBO of the C20-H21 to the unoccupied pi*-NBO of the two adjacent carbonyl groups. (C) 2014 Elsevier B.V. All rights reserved.