Cobalt-Catalyzed C─N Bond Formation via Metal-Hydride Hydrogen Atom Transfer (MHAT)

Nitrogen-containing molecules are ubiquitous in pharmaceuticals, agrochemicals, and functional materials, making the development of efficient C─N bond-forming reactions a central goal in synthesis. Cobalt-catalyzed metal-hydride hydrogen atom transfer (Co─H/MHAT) has emerged as a powerful platform for alkene hydroamination by enabling the controlled generation of carbon-centered radicals under mild and near-neutral conditions. This review summarizes the development of Co-MHAT-enabled C─N bond formation from its origins to recent advances, tracing all transformations to a common Co─H-initiated radical/organocobalt branch point. Across both reductive Co/photoredox and oxidative Co-MHAT manifolds, a common Co─H-initiated step generates a shared radical/organocobalt intermediate that can be directed into distinct pathways, including radical-radical coupling (RRC), radical-polar crossover (RPC), and radical ligand transfer (RLT). These complementary reactivity modes enable amination at sterically hindered and electronically unbiased sites. Collectively, Co-MHAT catalysis offers a versatile and conceptually distinct strategy for selective C─N bond construction.