Halogen Bond-Assisted Electron-Catalyzed Atom Economic Iodination of Heteroarenes at Room Temperature

A halogen
bond-assisted electron-catalyzed iodination of heteroarenes
has been developed for the first time under atom economic condition
at room temperature. The iodination is successful with just 0.55 equiv
of iodine and 0.50 equiv of peroxide. The kinetic study indicates
that the reaction is elusive in the absence of a halogen bond between
the substrate and iodine. The formation of a halogen bond, its importance
in lowering the activation barrier for this reaction, the presence
of radical intermediates in a reaction mixture, and the regioselectivity
of the reaction have been demonstrated with several control experiments,
spectroscopic analysis, and quantum chemical calculations. Allowing
the formation of the halogen bond may offer a new strategy to generate
the reactive radical intermediates and to enable the otherwise elusive
electron-catalyzed reactions under mild reaction conditions.