Arene-Iminium Salt Electron-Transfer Photochemistry. Mechanistically Interesting Photoaddition Processes

Article abstract of DOI:10.1021/ja00243a028

Studies of the electron-transfer photochemistry of arene-iminium salt systems have been explored.Fluorescence quenching investigations have demonstrated that a series of arenes including substituted toluenes and benzenes quench the fluorescence of a variety of 2-aryl-1-pyrrolinium perchlorates.Quenching rate constants in these cases correlate with the ΔG_SET values as expected for quenching by reversible electron-transfer pathways.In addition, nonconjugated iminium salts quench the fluorescence of a host of arenes with k_q values which parallel those predicted on the basis of electron-transfer free energy calculations.Photoaddition reactions of toluene, benzyltrimethylstannane, and 2-aryl-1-pyrrolinium salts have been explored.Likewise, electron-transfer-induced, excited-state reactions of toluene and benzyltrimethylsilane with 1,2-dimethyl-1-pyrrolinium perchlorate have been investigated.The results of these photoreactions have been interpreted in terms of steric, electrofugal group, and solvent effects upon the rates of competitive pathways available to initially formed radical cation pair intermediates.Finally, the photochemistry of benzyltrimethylstannane is described.