Synthesis, antimicrobial and DFT studies of novel fused thiazolopyrimidine derivatives

The reaction of dihydropyrimidine-2(1H)-thione 4, obtained by the condensation of chalcone 3 with thiourea, with chloroacetic acid and 1,2-dibro-moethane furnished compounds 5 and 6 and not their respective isomers 8 and 9. The regiochemistry of the cyclized products and their structure was 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 compound 5a and its isomer 8a with Jaguar version 6.5112 using B3LYP density functional method and 6-31G** basis set. H-1 and C-13 NMR spectra of compound 5a and its possible isomer 8a have been calculated and correlated with experimental results. 2-Arylidene derivatives of 5 were obtained by two routes and their structure was established by spectral data. Compounds 4-7 were screened for their antimicrobial activities.