Copper‐Catalyzed Oxidation of 5‐Hydroxymethylfurfural to 2,5‐Diformylfuran Assisted by TEMPOL in Liquid Sunlight Methanol

2,5-diformylfuran (DFF) is a significant biomass-derived compound with diverse applications in novel furan-based materials, fragrances, fuel additives, and drug synthesis. A pivotal challenge in DFF synthesis was developing a method to produce DFF under mild conditions using sustainable feedstocks. In this study, an affordable 4-hydroxy-2,2,6,6-tetramethylpiperidine (TEMPOL)- assisted Cu(OAc)