Four new pentacyclic benzodiazepine derivatives (PBDTs 13-16) were synthesized by conventional thermal heating and microwave-assisted intramolecular cyclocondensation. Their anticonvulsant, sedative and anxiolytic activities were evaluated by drug-induced convulsion models, a pentobarbital-induced hypnotic model and an elevated plus maze in mice. PBDT 13, a triazolopyrrolo[2,1-c][1,4] benzodiazepin-8-one fused with a thiadiazolone ring, exhibited the best anticonvulsant, sedative and anxiolytic effects in our tests. There was no significant difference in potency between PBDT 13 and diazepam, and we proposed that the action mechanism of PBDT 13 could be similar to that of diazepam via benzodiazepine receptors.