Activation of N−O σ Bonds with Transition Metals: A Versatile Platform for Organic Synthesis and C−N Bonds Formation**

N−O σ bonds containing compounds are versatile substrates for organic synthesis under transition metal catalysis. Their ability to react through both polar (oxidative addition, formation of metallanitrene, nucleophilic substitution) and radical pathways (single electron transfer, homolytic bond scission) have triggered the development of various synthetic methodologies, particularly toward synthesizing nitrogen-containing compounds. In this review, we discuss the different modes of activation of N−O bonds in the presence of transition metal catalysts, emphasizing the experimental and computational mechanistic proofs in the literature to help to design new synthetic pathways toward the synthesis of C−N bonds.