Electron-Transfer-Mediated Synthesis of Phenanthridines by Intramolecular Arylation of Anions from N-(ortho-Halobenzyl)arylamines: Regiochemical and Mechanistic Analysis

The synthesis of a series of substituted phenanthridines by photostimulated C-C cyclization of anions from N-(ortho-halobenzyl)arylamines has been found to proceed in very good to excellent yields (79-95%) in liquid ammonia and in DMSO. The N-(ortho-halobenzyl)arylamines are obtained in good to very good isolated yields (44-85%) by nucleophilic substitution of ortho-halobenzylchlorides with different arylamines. The reaction of the anions of a diverse set of N-(ortho-halobenzyl)arylamines was studied, and the methodology was extended to the synthesis of tri-spheridine, a natural product, in very good yield. In order to explain the regiochemical outcome or these reactions, a theoretical analysis was performed with DFT methods and the B3LYP functional.