Metal-free mild oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran

The potential of 4-hydroxy-2,2,6,6-tetramethyl-piperidine-1-oxyl (4-hydroxy-TEMPO radical) as an oxidant with [bis(acetoxy)-iodo]benzene (BAIB) and acetic acid (CH3COOH) as co-oxidants to convert 5-hydroxymethylfurfural (5-HMF) into 2,5-diformylfuran (2,5-DFF) was investigated. The effects of oxidant/acid dosages, choice of appropriate solvent, reaction temperature and time were determined to maximize the 2,5-DFF yield. Optimally, 66% 2,5-DFF yield was achieved in TEMPO/BAIB/CH3COOH system at 30 °C after 45 min in ethyl acetate. The reaction system is environmentally benign (metal-free) and energy efficient (mild at short reaction period). With scarce reports on 2,5-DFF production, the developed system provides an alternative route for a better access and wider application of this important platform chemical.