Crystal and molecular structures of 1,4-dihydro-6-methyl-5-N,N-diethylcarbamoyl-4-phenyl-2(3H)-pyrimidinethione (1) and 1,4-dihydro-6-methyl-5-N-methyl carbamoyl-4-(2′-nitrophenyl)-2(3H)-pyrimidinethione hemihydrate (2)

The crystal structure of 1,4-dihydro-6-methyl-5-N,N-diethylcarbamoyl-4-phenyl-2(3H)-pyrimidinethione, C16H21N3OS (1), is monoclinic, space group P2(1)/n, a = 6.818(1), b = 13.211(2), c = 18.807(3) Angstrom, = 99.53(1)degrees, V = 1670.6(4) Angstrom(3), Z = 4 and d(cal) = 1.206 Mg/m(3), R = 0.042 (wR = 0.119) for 190 parameters and 2560 observations with I greater than or equal to 2sigma(I) and 1,4-dihydro-6-methyl-5-N-methyl carbamoyl-4-(20-nitrophenyl)-2(3H)-pyrimidinethione hemihydrate, C13H14N4O3S . 0.5H(2)O, (2), is triclinic, space group P1, a = 7.513(1), b = 14.381(2), c = 15.506(2) Angstrom, alpha = 114.95(2), = 98.11(1), gamma = 93.55(1)degrees, V = 1490.0(3) Angstrom(3), Z = 4 and dcal = 1.406 Mg/m(3), R = 0.062 (wR = 0.165) for 388 parameters and 3094 observations with I greater than or equal to 2sigma(I). The compound 2 crystallized having two molecules in the asymmetric unit, which can be regarded as monohydrated dimers, and forming a hydrate. The conformation of the central heterocyclic ring (1,4-dihydropyrimidine) in both compounds was found to be close to a half-chair conformation. The 2-nitrophenyl substituent in 2 is in the axial synperiplanar orientation. In both compounds, the conformation of the 3-substituted carbamoyl group appears to be influenced by hydrogen bonding with anticlinal orientation observed for carbonyl groups serving as hydrogen bonding acceptors.