Chemocatalytic and Enzymatic Synthesis of 5-Hydroxymethylfuran-2-carbonitril and Novel Biobased Polyimidoesters from the Biorenewable Feedstock 5-Hydroxymethyl-2-furfural

5-Hydroxymethyl-2-furfural (5-HMF) is a platform molecule with a rich and versatile chemistry, which represents a promising biobased molecule for the formation of biopolymers with potential for a large-scale replacement of petroleum-based materials such as plastics and polymers. 5-Hydroxymethylfuran-2-carbonitril (5-HMFCN) is an analogue of 5-HMF containing a nitrile moiety and is readily accessible via Cu(II)OAc-catalyzed in situ-dehydration of the corresponding aldoxime (E/Z)-5-hydroxymethylfuran-2-carboxim (5-HMFO). After process optimization, this method leads to a complete conversion of the aldoxime with a product nitrile to product amide ratio of 25 mol/mol on a 10 g synthesis scale (96% nitrile selectivity). As an alternative route starting also from 5-HMFO, an enzymatic synthetic route to 5-HMFCN is described for the first time using the aldoxime dehydratase (Oxd) mutant M29G, which leads to the complete conversion of the oxime species to the nitrile compound within 24 h of reaction time at 14 mM substrate loading and 50 g/L biowet-weight (bww) concentration of the whole-cell catalyst suspended in aqueous buffer. Furthermore, it was found in this work for the first time that 5-HMFCN readily forms a polyimidoester by a simple heating procedure. The glass transition temperature can be adjusted from −60 to 90 °C by varying the polymerization time and temperature, and excellent thermal stability up to 340 °C has been observed for this novel type of polyimidoester.