Nitrene Transfer Reactions for Asymmetric C-H Amination: Recent Development

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.