2-(2-Cyano-acetylamino)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylic acid ethyl ester (2) was utilized as a key intermediate for the synthesis of thiocarbamoyl derivative 3 via its reaction with phenyl isothiocyanate. Treatment of 3 with chloroacetyl chloride afforded thiazolidin-5-one 4. Compound 7 reacted with different α-halo carbonyl compounds to give thiazolidine 8a,b, and thiazolidin-4-one derivatives 9. Treatment of 4 with the appropriate aromatic aldehyde and tolyl diazonium chloride afforded the corresponding thiazolidin-5-one derivatives 5a,b and 6, respectively. The thiazolidin-4-one derivative 10 was obtained via the reaction of compound 2 with 2-mercaptoacetic acid. Finally, the thiazoline 11 was obtained via the reaction of compound 2 with phenyl isothiocyanate/sulfur. The title compounds were characterized by elemental analyses and spectral data. The quantum mechanical calculations for some compounds were accomplished and subjected for antioxidant and antitumor studies, whereas, some of them exhibited promising activities.