Mechanistic insights into photo-assisted DMF cleavage mediated by charge transfer reaction

Abstract

Mechanistic insights into the synthetically-valued metal-free sustainable N,N-dimethylamination of perfluoroarenes have been investigated. Density functional theory (DFT) and time-dependent DFT (TD-DFT) have been applied to provide details regarding photo-assisted cleavage of N, N-dimethylformamide (DMF) for the valued N, N-dimethylamination reaction. The radical reaction mediated by the electron transfer process causes DMF cleavage, which is responsible for the amination reaction. It was found that the energy barrier for the ground state reaction is thermally prohibitive. On the other hand, visible-light irradiation activates the electron-donor properties of DMF and acceptor properties of perfluoronaphthalene (PFN), so that the energy barrier for electron transfer reduces to ∼ 14 kcal/mol. The redistribution of the electronic charge between the DMF and PFN generates an imbalance of charge on the overall molecule. These events prompt the relocation of extraneous charges to some antibonding molecular orbitals so that one of the C-F bonds in PFN gets weakened and is easily broken. The reductive cleavage of the C-F bond enables the radical ions to react quickly to afford the amination products, which eventually deactivate to the ground state.