Synthesis, reactions and antimicrobial activity of new cyclopenta[e]thieno[2,3-b]pyridines and related heterocyclic systems.

Reaction of the arylidene cyanothioacetamides 1a, b with cyclopentanone was proved to give a mixture of 4-aryl-3-cyanocyclopenta[b]pyridine-2(1H)-thiones 2a, b and the corresponding 7-arylidene derivatives 3a, b. Compounds 2a, b were reacted with ethyl chloroacetate or chloroacetamide to give the promising S-substituted thiopyridines 6a-d. On treatment of the latter compounds with sodium ethoxide in boiling ethanol, they underwent intramolecular Thorpe-Ziegler cyclization to yield the corresponding 3-amino-4-aryl-2-functionalized-cyclopenta[e]thieno[2,3-b]pyridines (7a-d). Most of these thienopyridines were reacted with a variety of reagents to produce other new cyclopentathienopyridines as well as numerous of their condensed heterocyclic derivatives. Some of the compounds synthesized were tested in vitro for their antibacterial and antifungal activity.