title: Lipase-mediated selective oxidation of furfural and 5-hydroxymethylfurfural.
abstract: Furfural and 5-hydroxymethylfurfural (HMF) are important biomass-derived platform chemicals that can be obtained from the dehydration of lignocellulosic sugars. A possible route for the derivatization of furanics is their oxidation to afford a broad range of chemicals with promising applications (e.g., diacids, hydroxyl acids, aldehyde acids, monomers for novel polymers). Herein we explore the organic peracid-assisted oxidation of furanics under mild reaction conditions. Using lipases as biocatalysts, alkyl esters as acyl donors, and aqueous solutions of hydrogen peroxide (30 % v/v) added stepwise, peracids are formed in situ, which subsequently oxidize the aldehyde groups to afford carboxylic acids with high yields and excellent selectivities. Furthermore, the use of an immobilized silica-based 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) affords the selective oxidation of the hydroxymethyl group of HMF to afford 2,5-diformylfuran. That product can be subsequently oxidized using again lipases for the in situ peracid formation to yield 2,5-furandicarboxylic acid, which is considered to be a key building block for biorefineries. These lipase-mediated reactions proceeded efficiently even with high substrate loadings under still non-optimized conditions. Overall, a proof-of-concept for the oxidation of furanics (based on in situ formed organic peracids as oxidants) is provided.
authors.affiliation: Institut für Technische und Makromolekulare Chemie (ITMC), RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany.
authors.forename: Monika
authors.initials: M
authors.lastname: Krystof
authors.forename: María
authors.initials: M
authors.lastname: Pérez-Sánchez
authors.forename: Pablo
authors.initials: P
authors.lastname: Domínguez de María
mesh_terms: D002175:Candida / Q000201:enzymology; D003497:Cyclic N-Oxides / Q000737:chemistry; D005662:Furaldehyde / Q000031:analogs & derivatives* / Q000737:chemistry*; D008049:Lipase / Q000737:chemistry*; D010084:Oxidation-Reduction
chemical_list: D003497:Cyclic N-Oxides; C008046:5-hydroxymethylfurfural; D005662:Furaldehyde; D008049:Lipase; C003959:TEMPO