A scalable carboxylation route to furan-2,5-dicarboxylic acidElectronic supplementary information (ESI) available: Experimental procedures, additional data, NMR spectra. See DOI: 10.1039/c7gc01059a
Furan-2,5-dicarboxylic acid (FDCA) is a biomass-derived diacid that can be used to make polymers including polyethylene furandicarboxylate (PEF), a highly attractive substitute for petroleum-derived polyethylene terephthalate (PET). Current FDCA syntheses require edible fructose as the feedstock, en...
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Zusammenfassung: | Furan-2,5-dicarboxylic acid (FDCA) is a biomass-derived diacid that can be used to make polymers including polyethylene furandicarboxylate (PEF), a highly attractive substitute for petroleum-derived polyethylene terephthalate (PET). Current FDCA syntheses require edible fructose as the feedstock, entail a difficult oxidation step that generates undesirable aldehyde impurities, and have moderate yields. As an alternative, carbonate-promoted C-H carboxylation enables the synthesis of FDCA from 2-furoic acid and CO
2
. This route is potentially advantageous because 2-furoic acid is made from furfural, a feedstock produced commercially from inedible lignocellulosic biomass, and it obviates late-stage oxidation. In the carboxylation reaction, salt mixtures composed of alkali furan-2-carboxylate (furoate) and alkali carbonate (M
2
CO
3
) are heated under CO
2
in the absence of solvent or catalysts to form furan-2,5-dicarboxylate (FDCA
2−
), which is subsequently protonated to produce FDCA. Previously, high yields were achieved on small-scale reactions using caesium furoate and Cs
2
CO
3
. In this work, we investigate the carboxylation reaction using alkali furoate/M
2
CO
3
salts containing cation blends and describe reaction conditions that provide high yields on a preparative scale. We show that the carboxylation proceeds efficiently with K
+
/Cs
+
blends that have a high K
+
content (up to 4 : 1 K
+
: Cs
+
). Removing H
2
O, which is a by-product of the reaction, is important for suppressing decomposition pathways. The accumulation of the FDCA
2−
product inhibits the reaction. Integrating these lessons, we demonstrate the carboxylation of furoate on a 1 mol scale using a fixed-bed flow reactor with 89% isolated yield of pure FDCA upon protonation.
2-Furoic acid is converted to furan-2,5-dicarboxylic acid in high yield on a mole scale using carbonate-promoted C-H carboxylation. |
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ISSN: | 1463-9262 1463-9270 |
DOI: | 10.1039/c7gc01059a |