A convenient synthetic route to novel 7-substituted benzo[f]thieno[3,2-h]quinazoline and 8-substituted benzo[g,h]dithieno[2,3-e:3′,2′-j]perimidine systems, bearing the fused pyrimidine ring, has been advanced. A commercially available 5-bromopyrimidine was used as the starting material to obtain various polycyclic systems through the sequence of nucleophilic aromatic substitution of hydrogen (the S_N ^H reaction), Suzuki cross-coupling and oxidative photocyclization. Evidence for the structure of benzo[g,h]dithieno[2,3-e:3′,2′-j]perimidines has been obtained by X-ray crystallographic analysis. Molecular orbital calculations (DFT), as well as redox and optical measurements for all new compounds have been performed. The data show that the reported polycyclic systems have potential for use in organic electronic applications. A convenient route to a new class of diazapyrene systems, bearing the fused pyrimidine ring, is presented along with their optoelectronic properties. The photophysical and electrochemical properties of these thienoazaacenes have been investigated by UV/Vis absorption and photoluminescence spectrophotometry. Cyclic voltammetry, and X-ray crystallography studies have also been performed.