Synthesis and pharmacological evaluation of a series of 4-piperazinylpyrazolo[3,4-b]- and -[4,3-b][1,5]benzodiazepines as potential anxiolytics

The synthesis and pharmacological evaluation of a series of pyrazolo[b][1,5]benzodiazepines are described. Some of the 4-piperazinyl-2,10-dihydropyrazolo[3,4-b][1,5]benzodiazepine derivatives demonstrated potent anxiolytic activity in the three-part operant anticonflict test in rats. Compounds 21 and 30 were more active than the clinically effective anxiolytic chlordiazepoxide in releasing conflict-suppressed behavior. This study shows a dissociation of the anxiolytic and antidopaminergic activities found in the thieno- and dibenzodiazepine derivatives flumezapine and clozapine, respectively. Examples of the three other dihydropyrazolo[b][1,5]benzodiazepine ring systems are described and evaluated for comparison and were found to be less active.