Ring contraction of 1,2,4-triazepino[2,3-a]benzimidazol-4-ones. New fused .beta.-lactams
摘要:
Isolation of uncommon fused tetracyclic beta-lactams 2 strongly supports a previously unconfirmed ionic mechanism for the ring contraction of nitrogen-bridged azolo-1,2,4-triazepin-3-ones in acetic anhydride. Procedures for the synthesis in good yields of substituted-pyrazolo[1,5-alpha]benzimidazoles from the corresponding [1,2,4]triazepino[2,3-alpha]benzimidazoles are reported.