Synthesis of certain new fused 1,4-diazepine derivatives, namely, cyclopentathienodiazepinones and their benzothieno analogues IV to produce new compounds of possible CNS depressant activity. Eleven compounds IV 1, 5, 6, 7, 12, 13, 15, 19, 20, 21 & 26 were selected and submitted to pharmacological evaluation for anxiolytic and tranquilizing activity in the open field test.