From C-H to C-N Bonds: Three Challenges, Three Catalysts, Three Solutions.

N-heterocycles are key building blocks for many pharmaceutical products. An efficient and sustainable method for the synthesis of this class of compounds consists of the recently established intramolecular C-H amination reaction. Development of new iron-based catalysts for this transformation is of paramount importance. Herein, three major challenges in this field are addressed: the accessibility of the catalyst, the lack of mechanisticunderstanding, and the limited activity and robustness of the catalyst. These challenges are tackled by threedifferent catalysts. The first catalyst is the commercially available FeI2, that shows good activities, but is limitedto substrates with activated C-H bonds. The Fe(HMDS)2 catalyst is used to perfom in-depth mechanistic studies, revealing key intermediates of the C-H amination reaction. The third catalyst, featuring mesoionic carbene ligands, displays unprecedented activities and aminates various C-H bonds.