title: Oxidation of 5-Chloromethylfurfural (CMF) to 2,5-Diformylfuran (DFF).
abstract: 2,5-Diformylfuran (DFF) is an important biorenewable building block, namely for the manufacture of new polymers that may replace existing materials derived from limited fossil fuel resources. The current reported methods for the preparation of DFF are mainly derived from the oxidation of 5-hydroxymethylfurfural (HMF) and, to a lesser extent, directly from fructose. 5-Chloromethylfurfural (CMF) has been considered an alternative to HMF as an intermediate building block due to its advantages regarding stability, polarity, and availability from glucose and cellulose. The only reported method for the transformation of CMF to DFF is restricted to the use of DMSO as the solvent and oxidant. We envisioned that the transformation could be performed using more attractive conditions. To that end, we explored the oxidation of CMF to DFF by screening several oxidants such as H₂O₂, oxone, and pyridineN-oxide (PNO); different heating methods, namely thermal and microwave irradiation (MWI); and also flow conditions. The combination of PNO (4 equiv.) and Cu(OTf)₂ (0.5 equiv.) in acetonitrile was identified as the best system, which lead to the formation of DFF in 54% yield under MWI for 5 min at 160 °C. Consequently, a range of different heterogeneous copper catalysts were tested, which allowed for catalyst reuse. Similar results were also observed under flow conditions using copper immobilized on silica under thermal heating at 160 °C for a residence time of 2.7 min. Finally, HMF and 5,5'-oxybis(5-methylene-2-furaldehyde) (OBMF) were the only byproducts identified under the reaction conditions studied.
authors.affiliation: Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal. ana_vicente@netc.pt.
authors.forename: Ana I
authors.initials: AI
authors.lastname: Vicente
authors.affiliation: Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal. jaimeacoelho@gmail.com.
authors.forename: Jaime A S
authors.initials: JA
authors.lastname: Coelho
authors.affiliation: Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal. svilen.p.simeonov@gmail.com.|Institute of Organic Chemistry with Centre of Phytochemistry Bulgarian Academy of Sciences, Acad. G. Bonchev str., bl. 9, 1113, Sofia, Bulgaria. svilen.p.simeonov@gmail.com.
authors.forename: Svilen P
authors.initials: SP
authors.lastname: Simeonov
authors.affiliation: Institute of Organic Chemistry with Centre of Phytochemistry Bulgarian Academy of Sciences, Acad. G. Bonchev str., bl. 9, 1113, Sofia, Bulgaria. lazarova@orgchm.bas.bg.
authors.forename: Hristina I
authors.initials: HI
authors.lastname: Lazarova
authors.affiliation: Institute of Organic Chemistry with Centre of Phytochemistry Bulgarian Academy of Sciences, Acad. G. Bonchev str., bl. 9, 1113, Sofia, Bulgaria. mpopova@orgchm.bas.bg.
authors.forename: Margarita D
authors.initials: MD
authors.lastname: Popova
authors.affiliation: Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal. carlosafonso@ff.ulisboa.pt.
authors.forename: Carlos A M
authors.initials: CA
authors.lastname: Afonso
mesh_terms: D002384:Catalysis; D005662:Furaldehyde / Q000031:analogs & derivatives* / Q000737:chemistry; D005663:Furans / Q000737:chemistry*; D008872:Microwaves; D010084:Oxidation-Reduction; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: C545952:5-(chloromethyl)furfural; D005663:Furans; D005662:Furaldehyde; C476922:2,5-diformylfuran
keywords: 2,5-diformylfuran; 5-chloromethylfurfural; 5-hydroxymethylfurfural; catalyst reuse; flow chemistry; heterogeneous catalysis; oxidation