X-ray, NMR and DFT studies on benzo[h]thiazolo[2,3-b]quinazoline derivatives

4-Phenyl-3,4,5,6-tetrahydrobenzo[h]quinazoline-2(1H)-thione 3, obtained by the condensation of 2-Benzylidene-3,4-dihydronapthalen-1(2H)-one 2 with thiourea, on reaction with chloroacetic acid and 1,2-dibromoethane furnish compounds 4 and 5 and not their possible isomers 7 and 8 respectively. The regiochemistry of the cyclized products and their structure is established by elemental analysis, H-1 NMR, C-13 NMR, IR and mass spectral data. Density functional theory (DFT) calculations have been carried out for compounds 4, 5 and their isomers 7 and 8 with Jaguar version 6.5112 using B3LYP density functional method and 6-31G** basis set. X-ray diffraction technique indicates that compound 4 crystallizes in the triclinic space group P-1, with Z = 2 and cell parameters a = 6.3404 (11) angstrom, b = 9.997 (3) angstrom, c = 13.560 (2) angstrom, alpha = 107.532(19)degrees, beta = 94.108(14)degrees, gamma = 97.469(17)degrees. H-1 and C-13 NMR of compounds 4, 5, 7 and 8 have been calculated and correlated with experimental results. 2-Arylidene derivatives of 4 were obtained by two routes and their structure was established by spectral data. The lowest energy optimized geometry of the compound 4 in gas phase is consistent with that obtained by X-ray crystallographic studies. (c) 2013 Elsevier B.V. All rights reserved.