Synthesis, Characterization, and Antifungal Activity of Some New Thieno[2,3-b]pyridines Incorporating Quinazoline or Benzimidazole Moiety

Reaction of 4,6-dimethyl-3-cyanopyridine-2(1H)-thione (IIIa) or 4,5,6-trisubstituted-3-cyanopyridine-2(1H)-thiones (IIIb-d) with 2-chloromethylquinazoline-4(3H)-one (IVa) furnished the corresponding 3-amino-2-(4-oxo-3,4-dihydroquinazolin-2-yl)thieno[2,3-b]pyridines (VIa-d). Reaction of aminothieno-pyridines (VIa, b, d) were reacted with triethyl orthoformate, acetic anhydride or nitrous acid to furnish pyridothienopyrimidoquinazolines (VIIIa, b, d), (IXa, b, d) or pyridothienotriazinoquinazolines (Xa, b, d). The new compound, 3-cyano-5-acetyl-6-methyl-4-styrylpyridine-2(1H)-thione (IIIe) was synthesized and reacted with 2-chloromethyl-1H-benzimadazole to give 5-acetyl-3-amino-2-(1H-benzimidazol-2-yl)-6-methyl-4-styryl-thieno[2,3-b]pyridine (XII) which was used as a key intermediate for synthesizing pyridothienopyrimidobenzimidazoles (XIII, XIV). All newly synthesized compounds were characterized on the basis of their elemental and spectral analyses. Also, most of the synthesized compounds were screened in vitro for their antifungal activity.