Copper(I) Photocatalyzed Bromonitroalkylation of Olefins: Evidence for Highly Efficient Inner‐Sphere Pathways

We report the visible light‐mediated copper‐catalyzed vicinal difunctionalization of olefins utilizing bromonitroalkanes as ATRA reagents. This protocol is characterized by high yields and fast reaction times under environmentally benign reaction conditions with exceptional scope, allowing the rapid functionalization of both activated and unactivated olefins. Moreover, late‐stage functionnalization of biologically active molecules and upscaling to gram quantities is demonstrated, which offers manifold possibilities for further transformations, e.g. access to nitro‐ and aminocyclopropanes. Besides the synthetic utility of the title transformation, this study undergirds the exclusive role of copper in photoredox catalysis showing its ability to stabilize and interact with radical intermediates in its coordination sphere. EPR studies suggest that such interactions can even outperform a highly favorable cyclization of transient to persistent radicals contrasting iridium‐based photocatalysts. Photocatalytic bromonitroalkylations of activated and unactivated olefins with broad scope become possible in the presence of CuI‐photocatalysts. The key to success for this transformation is the highly efficient interaction of CuII with radical intermediates, which can even outperform a highly favorable cyclization of a transient to a persistent radical.