Effective Coordination Promoted Carbene N─H Bond Insertion on Heterogeneous Cu Catalyst

In this study, we present a rationally designed Cu nanowire (NW) catalyst for carbene N─H bond insertion, addressing the challenges associated with highly coordinative aliphatic amines. The heterogeneous Cu NW catalyst with well-defined structures efficiently catalyzed carbene insertion reactions between various α-aryl diazoesters and aliphatic amines including monoethanolamine (MEA), achieving moderate to high yields. Infrared spectroscopy analysis and theoretical studies confirm the strong coordination of MEA on the surface of the Cu NW. Comprehensive kinetic studies reveal that both the two substrates and Cu NW were involved in the rate-determining step (RDS). Notably, the observed second-order dependence on Cu NW suggests that two identical Cu atoms participated in the RDS, one coordinating with the carbene carbon and the other binding with the amine nitrogen. A Hammett-plot study with 4-substituted benzylamines reveal that amines bearing electron-donating groups reacted significantly more slowly than those bearing electron-withdrawing groups, supporting a concerted N─H carbene insertion mechanism. Collectively, these findings elucidate the exceptional catalytic performance of Cu NW in carbene N─H bond insertion reactions, further underscoring the significance of heterogeneous catalysts in organic transformations.