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 I is reported from suitable alpha,beta-diamine IV (or corresponding (beta-nitroamine) and phthalic anhydride (1) in a three- or four-step sequence in good yields. The key step of this methodology is based on an intramolecular alpha-aza-amidoalkylation of the N-acyliminium species. Furthermore, when R-2 is an aromatic moiety a competing alpha-amidoalkylation took place and imidazo[2,1-a]isoindolones (or benzimidazo[2,1-a]isoindolones) I and/or isoindolo[1,4]benzodiazepines III were obtained under kinetic or thermodynamic control. The chemoselectivity of these transformations is also discussed. (C) 2004 Elsevier Ltd. All rights reserved.