Expanding Ullmann Homocoupling to Cross-Coupling: Electrochemical Copper-Catalyzed Cross-Electrophile Coupling of Alkyl and Aryl Halides

The construction of C-C bonds is a pivotal transformation in organic synthesis. Traditional Ullmann type and Hurtley reactions for constructing C(sp3)-C(sp2) bonds rely on organometallic reagents or substrates with active methylene units. These requirements significantly limit their practical applicability. Herein, employing two readily available organic halides, we report a ligand-enabled, electrochemical copper-catalyzed cross-electrophile coupling. Although Cu is the first metal reported for C-C bond construction, cross-electrophile coupling nowadays is dominated by Ni. This work demonstrates that efficient cross-electrophile coupling can be realized by electrochemical Cu catalysis. Our protocol is applicable to a wide range of propargyl bromides and (hetero)aryl iodides or bromides, delivering the desired products in good yields with high cross-selectivity. The use of an orthodimethylamine-substituted diamine ligand is crucial for promoting the reaction and suppressing cathodic Cu deposition. We attribute this effect to an intramolecular H···N H-bonding, which facilitates hyperconjugation between the NMe2 moiety and the nitrogen atom coordinated to the Cu center. Mechanistic studies indicate that the reaction follows a radical pathway, contrasting with the SN2 pathway reported previously. This work establishes a foundation for electrochemical Cu-catalyzed cross-electrophile coupling and provides a new paradigm for Cu-catalyzed C-C bond formation via radical intermediates.