Convergent Synthesis of α-Branched Amines by Transition-Metal-Catalyzed C-H Bond Additions to Imines.

α-Branched amines are ubiquitous in drugs and natural products, and consequently, synthetic methods that provide convergent and efficient entry to these structures are of considerable value. Transition-metal-catalyzed C-H bond additions to imines have the potential to be highly practical and atom-economic approaches for the synthesis of a diverse and complex array of α-branched amine products. These strategies typically employ readily available starting inputs, display high functional group compatibility, and often avoid the production of stoichiometric waste byproducts. A number of C-H functionalization methods have also been developed that incorporate cascade cyclization pathways to give amine-substituted carbocycles, and in many cases, proceed with the formation of multiple stereogenic centers. Advances in the area of asymmetric C-H bond additions to imines have also been achieved through the use of chiral imine N-substituents as well as by enantioselective catalysis.