Copper Makes the Difference: Visible Light-Mediated Atom Transfer Radical Addition Reactions of Iodoform with Olefins

Herein, we report a visible light-mediated copper-catalyzed protocol enabling the highly economic, vicinal difunctionalization of olefins utilizing the readily available bulk chemical iodoform. This protocol is characterized by high yields under environmentally benign reaction conditions and allows the regioselective and chemoselective functionalization of activated double bonds. Besides the synthetic utility of the shown transformation, this study undergirds the exclusive role of copper in photoredox catalysis as the title transformation is not possible via the most commonly employed ruthenium, iridium, or organic dye-based photocatalysts owing to the ability of copper to stabilize and interact with radical intermediates in its coordination sphere. Furthermore, the protocol can be smoothly scaled to gram quantities of the product, which offers manifold possibilities for further transformations, for example, heterocycle synthesis or intramolecular cyclopropanation.