Synthesis, Reactions, and Biological Activity of 4(1H-Indol-3-yl)-2-Thioxopyridine Derivatives

2-cyanoethanthioamide 1 reacted with 1H-indole-3-carbaldehyde 2 to give the corresponding 2-cyano-3-(1H-indol-3-yl)prop-2-enethioamide 3 in a very good yield, which in turn reacted with 2,4-pentanedione 4 to give 5-acetyl-1,2-dihydro-4(1H-indol-3-yl)-6-methyl-2-thioxopyridine-3-carbonitrile. The synthetic potential of 5 was examined through its reaction with several active halogen-containing reagents, e.g., 1-chloropropan-2-one, chloroacetonitrile, 2-chloroacetamide, ethyl chloroacetate, chloroacetic acid, ethyl chloroformate, methyl iodide, and 2-bromo-1-arylethanones 13a–c to give the corresponding thieno[2,3-b]pyridine derivatives 15a–c. The data of elemental analysis as well as the data of IR (cm−1), 1H NMR (δ ppm), and mass spectra elucidated structures of all newly synthesized heterocyclic compounds. All newly synthesized heterocyclic compounds were evaluated as antimicrobial and GST enzyme activity and at the GSH enzyme level.