H. Memarian, M. Ranjbar, H. Sabzyan
Sep 24, 2013
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Influential Citations
6
Citations
Journal
Journal of Molecular Structure
Abstract
Abstract X-ray crystal structure analysis and quantum chemical calculations based on density functional theory (DFT) were used for structural and electronic characterizations of two 1,2,3,4-tetrahydropyrimidine derivatives (THPMs), namely, ethyl 6-methyl-4-phenyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate ( 1 ) and methyl 4-(4-bromophenyl)-1,6-dimethyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate ( 2 ). The results of these studies revealed that the heterocyclic ring adopts a quasi-boat conformation, in which the 4-aryl group occupies the pseudo-axial position. The occurrence of the C 4 -stereocenter in the heterocyclic ring causes the formation of both R- and S- enantiomers. X-ray diffraction technique indicates that both compounds exist as a racemic mixture in the crystal structure and the enantiomers are orientated to each other via hydrogen bonding between N 3 H as donor and the C 2 S or C 2 O groups as acceptor species, in each layer under formation of an enantio-syndio packing. Most computational bond lengths and angles are well in agreement with experimental data, and support the pseudo-axial orientation of the C 4 -aryl substitution.