Benzoic Acid/TEMPO as a Highly Efficient Metal‐Free Catalyst System for Selective Oxidation of 5‐hydroxymethylfurfural into 2, 5‐diformylfuran. Issue 8 (3rd March 2017) - Li, Jinlong
Abstract: The combination of benzoic acid and 2, 2, 6, 6‐teramethylpiperidin‐1‐oxyl (TEMPO) afforded an efficient catalytic system for the aerobic oxidation of 5‐hydroxymethylfurfural (HMF) into 2, 5‐diformylfuran (DFF) under certain conditions. The maximum conversion of 86.7 % for HMF was obtained with a nearly 77.8 % DFF yield at 1 mmol benzoic acid and 0.4 MPa oxygen pressure in acetonitrile. The aerobic oxidation ability of HMF into DFF depended on the electron density of the organic acid skeletal structure with the carboxyl group. Meanwhile, the catalyst system of benzoic acid/TEMPO also exhibited good performance for aerobic oxidation of other alcohols. Based on experimental results, we propose that the benzoic acid acted as the primary catalyst and TEMPO was the key co‐catalyst, oxidized into oxoammonium cation through electron transport and then regenerated by a superoxide radical during the reaction. Abstract : Metal‐free catalysis : The combination of benzoic acid and 2, 2, 6, 6‐teramethylpiperidin‐1‐oxyl (TEMPO) affords an efficient catalytic system for the aerobic oxidation of 5‐hydroxymethylfurfural (HMF) into 2, 5‐diformylfuran (DFF) under certain conditions. Based on experimental results, we propose that the benzoic acid acts as the primary catalyst and TEMPO is the key co‐catalyst, oxidized into oxoammonium cation through electron transport and then regenerated by a superoxide radical during the reaction.