Ring Concentration of 1,2,4-Triazepinobenzimidazol-4-ones. New Fused β-Lactams

Article abstract of DOI:10.1021/jo00001a017

Isolation of uncommon fused tetracyclic β-lactams 2 strongly supports a previously unconfirmed ionic mechanism for the ring concentration of nitrogen-bridged azolo-1,2,4-triazepin-3-ones in acetic anhydride.Procedure for the synthesis in good yields of substituted-pyrazolo<1.5-a>benzimidazoles from the corresponding <1.2.4>triazepino<2.3-a>benzimidazoles are reported.