“…In general, DFF is prepared by the oxidation of HMF [ 8 , 11 ]. The selective oxidation of the hydroxyl group into the aldehyde has been achieved using a variety of different methodologies including homogeneous [ 8 , 11 , 15 , 16 ] and heterogeneous [ 8 , 11 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ] metal catalysis, a one-step procedure from fructose (DMSO, NaBr (cat. ), 150 °C, 50%) [ 38 ], using molybdovanadophosphoric heteropolyacids [ 39 , 40 ], using polyaniline-grafted vanadyl acetylacetonate [ 41 ], metal free procedures [ 42 , 43 , 44 ] and enzyme catalysis [ 45 ].…”