Nine new 2-(substituted phenyl)/alkyl[1,3,4]thiadiazolo[2,3-b]-6,7,8,9-tetrahydrobenzo(b)thieno[3,2-e]pyrimidin-5(4H)-ones, six new 3-amino-2-[(2-oxo-2-(aryl)ethyl)thio]-5,6,7,8-tetrahydro[1]benzothieno[2,3-d]pyrimidin-4(3H)-ones, one 2-mercapto[1,3,4]thiadiazolo[2,3-b]-6,7,8,9-tetrahydrobenzo(b)thieno[3,2-e]pyrimidin-5(4H)-one and one 2-chloromethyl[1,3,4]thiadiazolo[2,3-b]-6,7,8,9-tetrahydrobenzo(b)thieno[3,2-e]pyrimidin-5(4H)-one were synthesized from 3-amino-2-mercapto-5,6,7,8-tetrahydro[1]benzothieno[2,3-d]pyrimidin-4(3H)-one. The newly synthesized compounds were characterized by analytical and spectral data. Compounds were screened for anti-inflammatory, CNS depressant and antimicrobial activities. Some of the compounds exhibited promising biological activities.