Direct Selective Oxidative Functionalization of C–H Bonds with H2O2: Mn-Aminopyridine Complexes Challenge the Dominance of Non-Heme Fe Catalysts

Non-heme iron(II) complexes are widespread synthetic enzyme models, capable of conducting selective C-H oxidation with H₂O₂ in the presence of carboxylic acid additives. In the last years, structurally similar manganese(II) complexes have been shown to catalyze C-H oxidation with similarly high selectivity, and with much higher efficiency. In this mini-review, recent catalytic and mechanistic data on the selective C-H oxygenations with H₂O₂ in the presence of manganese complexes are overviewed. A distinctive feature of catalyst systems of the type Mn complex/H₂O₂/carboxylic is the existence of two alternative reaction pathways (as found for the oxidation of cumenes), one leading to the formation of alcohol, and the other to ester. The mechanisms of formation of the alcohol and the ester are briefly discussed.