Metal‐Free C−H Functionalization via Diaryliodonium Salts with a Chemically Robust Dummy Ligand

A two‐step strategy for the transition‐metal‐free C−H functionalization of arenes using unsymmetrical iodonium salts as versatile synthetic linchpins is presented. The key to the success of this strategy is the identification of the 3,5‐dimethyl‐4‐isoxazolyl (DMIX) group as a superior dummy ligand, which enables not only site‐selective C−H functionalization to afford unsymmetrical iodonium salts, but also highly selective aryl transfer during the subsequent metal‐free coupling reaction. Both electron‐rich and moderately electron‐deficient arenes can be converted into the iodonium salts through C−H functionalization, allowing for diverse structural elaboration by metal‐free C−N, C−C, C−S, and C−O coupling. A two‐step C−H functionalization applicable to both electron‐rich and electron‐deficient arenes is described. The method does not require a transition‐metal catalyst and allows rapid structural diversification through the incorporation of various functionalities into complex molecules.