C–H bonds are ubiquitous and abundant in organic molecules. If C–H bonds could be directly converted to desired functional groups in a chemo-, site-, and stereoselective manner, C–H functionalization would be a strong and useful tool for organic synthesis. Recent developments in catalytic and enzymatic chemistry have achieved highly sustainable and selective nitrene C–H insertion. Initially, C–H amination was inspired by model studies on enzymatic oxidation and used iminoiodinanes, nitrogen analogs of iodosobenzene, as nitrene precursors. Transition-metal/iminoiodinane systems are well studied and established. These systems can directly introduce sulfonamide groups with excellent stereoselectivity, albeit with co-production of iodobenzene as waste material. Fortunately, the atom economics of this methodology were improved by introducing highly sustainable nitrene sources such as azide compounds and 1,2,4-dioxazol-5-one derivatives. In this review, we present the details of these developments with respect to their catalysts and nitrene sources.
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