Kinetic versus thermodynamic access to imidazoisoindolones, benzimidazoisoindolones, and [1,4]diazepinoisoindolones: intramolecular nitrogen and π-aromatic trapping of N-acyliminium cation

Efficient assembly of substituted imidazo[2,1-a]isoindolones is reported from suitable α,β-diamine (or corresponding β-nitroamine) and phthalic anhydride () in a three- or four-step sequence in good yields. The key step of this methodology is based on an intramolecular α-aza-amidoalkylation of the N-acyliminium species. Furthermore, when R2 is an aromatic moiety a competing α-amidoalkylation took place and imidazo[2,1-a]isoindolones (or benzimidazo[2,1-a]isoindolones) and/or isoindolo[1,4]benzodiazepines were obtained under kinetic or thermodynamic control. The chemoselectivity of these transformations is also discussed.