Solarylations via 4-Aminophenyl Cations

The application of the photo-SN1 reaction on some 4-chloroanilines was explored under solar irradiation in view of obtaining a convenient metal-free arylation method. Several reactions previously carried out by UV irradiation, as well as some new ones, where either a new trap (alpha-methylstyrene) or a new halide (N,N-dimethyl-4-fluoroaniline) were adopted, were studied under these conditions and found to occur conveniently. Furthermore, at least in some cases the halide starting concentration could be raised up to 0.2 M, the excess trapping agent reduced from 20:1 to 2.5:1, and the solvent replaced by more environmentally friendly (co)solvents including water. Under these improved conditions, the photoarylation was carried out in a gram scale by merely exposing the solution to solar irradiation. This process has a low impact on the environment and can be considered a serious competitor of metal-catalyzed arylations.