Metal-Free Catalytic Cross-Coupling of Esters and Boranes

Over the last 50 years, palladium-catalyzed cross-coupling has become ubiquitous in chemical synthesis from laboratory to commercial scale. Due to the great importance of these reactions, extensive research efforts have been devoted to improving the sustainability, cost, and diversity of the catalysts and coupling partners. Herein, we report the rational design and experimental validation of a metal-free catalyst for cross-coupling of formate esters with organoboranes, forming aldehydes under mild, additive-free conditions. The novel mechanism establishes a model for direct C(acyl)–C(sp2) bond formation, a motif previously inaccessible via metal-free or radical-free cross-coupling pathways. Overall, this boron/nitrogen-based system is found to even outperform the efficacy of state-of-the-art nickel catalysts for ester cross-coupling, demonstrating the utility of main-group catalysts in efficiently activating challenging bonds.