Visible-Light-Promoted Aryl Cation Formation: Aromatic S N 1 Reactions of Areneazo-2-(2-nitro)propanes.

The visible light excitation of areneazo-2-(2-nitro)propane·HCl salts generated the singlet aryl cation that readily underwent aromatic S N 1 reactions with a variety of nucleophiles. The in situ generated singlet aryl cation was stabilized by a counter nitronate anion that prevented other intersystem crossing and single electron transfer processes. With the improved safety features of neutral areneazo-2-(2-nitro)propane derivatives, the current visible-light-promoted aromatic S N 1 reactions provide an alternative aryl C sp 2 -X bond forming strategy.