Furfural was synthesized from hexose sugars instead of 5-HMF by using polar aprotic solvents with very low basicity.

A novel catalytic strategy involving protective chemistry is presented for the selective production of 5-formylfuran-2carboxylic acid (FFCA) and furan-2,5-dicarboxylic acid (FDCA) from concentrated 5-hydroxymethylfurfural (HMF) solutions. By protecting the reactive formyl group of HMF by acetalization with 1,3-propanediol (PDO), degradation and premature oxidation of HMF is suppressed. A hydroxyapatite-supported Au catalyst can selectively oxidize HMF-acetal in a 10 wt % solution to FFCA-acetal in 94 % yield in 2 hours at 373 K under 0.5 MPa of O 2 . Deprotection of FFCA-acetal by mineral acids affords FFCA in 98 % yield and recovers nearly all PDO. FFCA in a 20 wt % solution can be oxidized to FDCA in 95 % yield under similar reaction conditions. The presented chemistry contributes to the development of novel manufacturing routes of prospective biobased monomer precursors using protecting agents.

No abstract