Copper-Catalyzed Halogen Exchange in Aryl Halides:  An Aromatic Finkelstein Reaction

A mild and general method for the conversion of aryl, heteroaryl, and vinyl bromides into the corresponding iodides was developed utilizing a catalyst system comprising 5 mol % of CuI and 10 mol % of a 1,2- or 1,3-diamine ligand. A variety of polar functional groups are tolerated, and even N-H containing substrates such as sulfonamides, amides, and indoles are compatible with the reaction conditions. Both the reaction rate and the equilibrium conversion of the aryl bromide depend on the choice of the halide salt and the solvent. The best results were obtained using NaI as the halide salt and dioxane, n-butanol, or n-pentanol as the solvents.