Electrochemical transformation of bio-derived furans using a salen-manganese homogeneous catalyst

A sustainable model society requires a change from an economy based in fossil resources to the so-called bio-based economy, where most of the chemicals and materials are produced from renewable feedstocks like biomass. The development of new catalysts for the transformation of biomass derived compounds into valued-added chemicals and liquid fuels is highly desirable to overcome the key challenges for market penetration of the sustainable biomass-based products. 5-hydroxymethylfurfural (HMF) is one of these most promising products, which has the potential to be converted to a variety of useful intermediates for polymers and many other fine chemicals.

In this communication, we report the electrochemical oxidation of HMF to DMF (2,5-furandicarboxaldehyde) catalysed by a salen-manganese homogeneous catalyst. DMF is a versatile precursor in the synthesis of functional polymers, pharmaceuticals, antifungal agents, and furan-urea resins. A manganese(III)-Schiff base complex 1 was synthetized and characterized by different analytical and spectroscopic techniques. Complex 1 behaves as a peroxidase mimic and also as an efficient catalyst for electrochemical oxidation of HMF to DMF. Conversion of HMF to DFF was performed under mild conditions in saline media, following a procedure developed by us. Oxidation of DFF to HMF with conversion rate of 75% was achieved at pH 8.5, phosphate buffer and using sodium chloride as electrolyte to increase the conductivity and to reduce power dissipation. The role of the catalyst is this process is also discussed in this communication.