Synthesis and structural assignment of certain pyrimido[1,2-alpha] benzimidazole derivatives

The pyrimido[1,2-alpha]benzimidazole derivatives compounds 1-8 were synthesized through cyclocondensation of 2-aminobenzimidazole with the appropriate benzsubstituted benzoylacetone by fusion at 150-170 degrees C for 5 h. Quaternary salts compounds 9-22 were obtained by quaternization of compounds 1-8 with dimethyl or diethyl sulfate and subsequent isolation as the relatively insoluble perchlorate salts. Assignment and confirmation of the structures of the newly synthesized compounds were based upon elemental microanalyses and other spectral evidence.