A facile and efficient method for the synthesis of N-substituted isoindolin-1-one derivatives from 2-formylbenzoic acid and amine under Pd(OAc)2/HCOOH system has been described. The whole process is carried out in ligand-free conditions and furnished the desired products by reductive intramolecular cyclization. Furthermore, this procedure is applied successfully for the modification of natural products, such as vindoline and estrone.