Catalytic Fe²⁺ Cation Pair Site for Base‐free <i>N</i>‐Alkylation of Aromatic Amines with Alcohols

The development of heterogeneous Fe catalysts is very attractive due to the ubiquitous, abundant, and inexpensive nature of Fe as a resource. However, Fe oxides are commonly inert as catalysts and hence, the design and fabrication of active Fe sites are essential. Herein, the fabrication of an active Fe cation pair site by simple reduction treatment of SiO₂-supported FeO_x (FeO_x/SiO₂) is presented. The active Fe cation pair site was formed by the removal of the oxygen atom between Fe cations of the FeO_x on SiO₂, namely oxygen vacancy formation, which is induced by temperature-controlled reduction treatment. 773 K reduction maximized the Fe cation pair sites without the decomposition of FeO_x species, which was an effective catalytic one for the N-alkylation of amines mainly proceeded through Meerwein-Ponndorf-Verley (MPV) type reduction, which is achieved by the stabilization of six-membered ring transition state derived from imines and alcohols over the open active site of the Fe cation pair site.