Background: Triazolobenzodiazepinones, i.e. 2,3-benzodiazepines condensed
with a triazolone ring, exhibited significant anticonvulsant activity in vivo. In
this paper, their new pyrrole bioisosteres, 2,11-dihydro-3H-pyrrolo[1,2-e][1,2,4]
triazolo[4,3-b][1,2,5]triazepin-3-ones were synthesized.
Methods: Starting from the corresponding bicyclic hydrazino intermediates, final
ring closure of the triazolone ring has been attempted with several reagents under
various conditions. Among these, only triphosgene provided the tricyclic title compounds.
Results: Six representatives of the title new ring system were synthesized. The structure
of the new scaffold was determined by single crystal X-ray measurement as well as 1H and 13C
Conclusions: Starting from 1-aryl-4-hydrazino-5H-pyrrolo[2,1-d][1,2,5]triazepines (15), representatives
of a new tricyclic compound family, 6-aryl-2,11-dihydro-3H-pyrrolo[1,2-e][1,2,4]triazolo[4,3-b][1,2,5]
triazepin-3-ones (17) have been synthesised. These compounds are pyrrole bioisosteres of 6-aryl-2,11-
dihydro-3H-[1,2,4]triazolo[4,3-c][2,3] benzodiazepine-3-ones (8), a family exhibiting an outstanding
in vivo anticonvulsant activity in mice.