NH-Heterocyclic Aryliodonium Salts and their Selective Conversion into N1-Aryl-5-iodoimidazoles

The synthesis of N-arylimidazoles substituted at the sterically encumbered 5-position is a challenge for modern synthetic approaches. A new family of imidazolyl aryliodonium salts is reported, which serve as a stepping stone on the way to selective formation of N1-aryl-5-iodoimidazoles. Iodine acts as a “universal” placeholder poised for replacement by aryl substituents. These new λ³-iodanes are produced by treating the NH-imidazole with ArI(OAc)₂, and are converted to N1-aryl-5-iodoimidazoles by a selective copper-catalyzed aryl migration. The method tolerates a variety of aryl fragments and is also applicable to substituted imidazoles.