Advances in NN Bond Formation: Mechanistic Diversity and Emerging Catalytic Strategies

The nitrogen–nitrogen (NN) bond is ubiquitous in organic compounds, yet efficient synthetic strategies for the direct construction of NN bonds remain challenging. Well‐known approaches, such as oxidative dehydrogenative coupling (ODC) and reductive coupling (RC), have provided valuable routes for forming NN linkages. Nitrene transfer strategies emerged as a complementary and increasingly versatile platform. The distinct electronic structures of classical closed‐shell nitrenoids (Fischer‐ and Schrock‐type), open‐shell nitrene radical intermediates, and photochemically generated nitrene species primarily govern NN bond‐forming selectivity. The use of electrochemical, photochemical, and biocatalytic approaches continues to expand the scope of sustainable synthetic chemistry. This review summarizes recent advances in ODC, RC, nitrene transfer chemistry, photochemical, electrochemical, and enzymatic approaches for NN bond formation, with particular emphasis on reaction design, mechanistic insights, and synthetic applications.