Low‐Temperature Nickel‐Catalyzed C−N Cross‐Coupling via Kinetic Resolution Enabled by a Bulky and Flexible Chiral N‐Heterocyclic Carbene Ligand

Abstract

AbstractThe transition‐metal‐catalyzed C−N cross‐coupling has revolutionized the construction of amines. Despite the innovations of multiple generations of ligands to modulate the reactivity of the metal center, ligands for the low‐temperature enantioselective amination of aryl halides remain a coveted target of catalyst engineering. Designs that promote one elementary reaction often create bottlenecks at other steps. We here report an unprecedented low‐temperature (as low as −50 °C), enantioselective Ni‐catalyzed C−N cross‐coupling of aryl chlorides with sterically hindered secondary amines via a kinetic resolution process (s factor up to >300). A bulky yet flexible chiral N‐heterocyclic carbene (NHC) ligand is leveraged to drive both oxidative addition and reductive elimination with low barriers and control the enantioselectivity. Computational studies indicate that the rotations of multiple σ‐bonds on the C2‐symmetric chiral ligand adapt to the changing needs of catalytic processes. We expect this design would be widely applicable to diverse transition states to achieve other challenging metal‐catalyzed asymmetric cross‐coupling reactions.