Benzimidazolo-diazepines From 1,3-dienes and Arenediazocyanides Through a 1,3,4-tri-aza-cope Rearrangement

Cyclic and bicyclic 1-cyano-2-arylhydrazines were prepared from arene diazocyanides and 1,3-dienes. Some of them rearrange at room temperature through a 1,3,4-triaza-Cope rearrangement, followed by an intramolecular cyclisation, to afford benzimidazolo-diazepines in moderate yields. When the competitive retro Diels-Alder reaction is made impossible by reduction of the cycloadducts, the rearrangement takes place at higher temperatures, with excellent yields, to previously unknown benzimidazolo-diazepines.