Homogeneous Iron Catalyzed C−H Amination

Abstract

AbstractIron‐catalyzed C−H amination is emerging as an attractive and sustainable method to install amine functionalities into organic compounds. Amination of C(sp3)−H bonds is usually mediated by an iron‐nitrene intermediate via a Hydrogen Atom Abstraction/Radical Recombination mechanism reminiscent of biomimetic C−H oxidation. Accordingly, this transformation can be catalyzed by engineered iron enzymes, heme and nonheme iron complexes as well as iron salts, although it is often limited to intramolecular reactions and/or activated positions. Aromatic C(sp2)−H amination is mediated by addition of electrophilic iron nitrenes or protonated N‐radical intermediates (produced with Fe catalysts) to aromatic systems. Again, high selectivity is obtained via (pseudo) intramolecular reactions. From a mechanistic perspective, several iron nitrene intermediates have been isolated and characterized over the years in different ligand scaffolds and iron oxidation states. Structure‐activity correlations have been drawn only in few cases and point to a key role of the spin density on the nitrene ligand and of the iron oxidation state. This review describes the state of the art for homogeneous iron catalyzed C(sp3)−H and C(sp2)−H amination focusing on the last 5 years (2019–2023) from a mechanism‐driven catalyst design perspective.