A novel access to the isoindolinone and isoquinolin-2-one skeletons from adequately substituted aromatic precursors is described. The key intramolecular cyclization step was performed by the action of phenyliodine (III) bis (trifluoroacetate)(PIFA) on the corresponding vinyl or allyl substituted N-(p-methoxyphenyl) benzamide derivatives leading to the heterocyclic compounds through 5-exo-trig and 6-exo-trig processes, respectively.