Ligand‐Free Copper‐Catalyzed Suzuki‐Miyaura‐Type Coupling via a Photo‐Mediated Radical Relay

Comprehensive Summary The Suzuki‐Miyaura cross‐coupling reaction, which couples organoboron nucleophiles with organic electrophiles, has become one of the most widely used methods for carbon‐carbon bond formation in modern organic synthesis. Although copper offers an attractive and cost‐effective alternative to precious metals, the development of copper‐catalyzed Suzuki‐Miyaura‐type coupling has remained comparatively limited. A major challenge lies in the generally sluggish oxidative addition of organic electrophiles to low‐valent copper species, which often requires elevated temperatures or specially designed ligands. In contrast, high‐valent copper intermediates are well known to undergo efficient reductive elimination, suggesting that alternative modes of electrophile activation could provide new opportunities for copper‐catalyzed cross‐coupling. Herein, we demonstrate that conventional oxidative addition can be circumvented by combining photochemical radical generation with organocopper chemistry. Under visible‐light irradiation, readily available electrophilic precursors are converted into highly reactive acyl or trifluoromethyl radicals, which are subsequently captured by arylcopper species derived from arylboronic acids. The resulting high‐valent copper intermediates undergo reductive elimination to furnish the corresponding C–C coupling products under mild and ligand‐free conditions. This strategy enables the synthesis of a broad range of aryl ketones from aromatic carboxylic acids and arylboronic acids through in situ activation, tolerating both electron‐donating and electron‐withdrawing substituents as well as sterically demanding substrates. The approach can also be extended to the trifluoromethylation of arylboronic acids using trifluoroacetic anhydride as a CF₃‐radical precursor, with good compatibility toward halides, carbonyl‐containing groups, cyano groups, heterocycles, and structurally complex bioactive molecules. This work provides a mechanistically distinct approach to copper‐catalyzed Suzuki‐Miyaura‐type bond formation and expands the synthetic utility of copper catalysis.