Synthesis of Condensed Tetrahydroisoquinoline Class of Alkaloids by Employing TfOH‐Mediated Imide Carbonyl Activation

Abstract

Abstract Isoquinoline‐based polycyclic lactams such as isoindoloisoquinolinones, pyrroloisoquinolinones, and benzo[ a ]quinolizinones were successfully assembled from the corresponding imides by using a TfOH‐mediated (TfOH = trifluoromethanesulfonic acid) imide carbonyl activation and cyclization strategy. By employing this simple method, the isoquinoline alkaloids crispine A, trolline/oleracein E, and erythrinarbine were successfully synthesized in racemic form. The reaction of unsymmetrical N ‐phenethylphthalimides with TfOH displayed excellent regioselectivity, which was rationalized by DFT calculations.