• alcohols;
  • biomass;
  • heterocycles;
  • magnetic properties;
  • oxidation


A highly selective aerobic oxidation of 5-hydroxymethylfurfural (5-HMF) into 2,5-diformylfuran (DFF) by employing a magnetically separable 2,2,6,6-tetramethylpiperidine-N-oxide (TEMPO) catalyst (Fe3O4@SiO2–TEMPO) under metal- and halogen-free conditions is described. Quantitative yields of DFF with excellent selectivities as high as >99 % were achieved under several versatile reaction conditions in a catalytic system consisting of Fe3O4@SiO2–TEMPO as a catalyst, tert-butyl nitrite as a co-catalyst, acetic acid as an additive, and toluene as a solvent. The results clearly demonstrate that the present catalytic system for selective conversion of 5-HMF into DFF is comparable or even superior to the many systems based on transition-metal catalysts. In addition, the catalyst can be successfully recovered and reused in five consecutive reaction runs by an external magnetic source with keeping its catalytic performance and selectivity.