Unlocking C═N Bond Formation Through Microwave- Assisted Reductive Coupling of Nitroarene with Alcohols on Fe1–N4 Single-Atom Catalyst

One of the most reliable strategies in organic synthesis is the formation of C═N bonds through the reductive coupling of nitro- arenes with alcohols to produce selectively functionalized imines; however, achieving this transformation remains challenging because of the facile over-hydrogenation of the C═N bond and the low catalytic efficiency of reported systems. Herein, we report the synthesis of a highly active iron single-atom catalyst supported on N-doped graphene (Fe1@NG) via ion adsorption and microwave irradiation. The Fe1@NG catalyst exhibits superior performance, achieving high turnover frequency (TOF, ≈150h−1) under base- and solvent-free conditions with excellent selectivity. Characterization by HAADF-STEM, XANES, and FT-XAFS confirms atomically dispersed Fe sites coordinated to four nitrogen atoms (Fe1–N4) with Fe+3 oxidation state. Experimental and theoretical analyses reveal that the electronic structure of Fe1–N4 centers facilitates hydrogen borrowing, enhancing catalytic activity. The DFT study showed that on the Fe1–N4 catalyst, benzyl alcohol is oxidized while 4-nitrophenol is reduced to 4-aminophenol, which then couples with benzaldehyde to form the imine product. This synergy of single-atom metal sites and stabilizing π–π interactions facilitates favorable adsorption and alignment of the aromatic reactants on the conjugated support, thereby modulating reaction thermodynamics and promoting efficient imine formation. The catalyst demonstrates broad substrate compatibility (over 20 examples), scalability, and excellent stability over multiple cycles without significant loss of activ- ity. This work presents a robust Fe-based catalyst for efficient and sustainable C—N bond formation.