Chemical and enzymatic synthetic routes to the diglycidyl ester of 2,5-furandicarboxylic acid

This work focuses on alternative, green synthetic methods for producing a bio-based bis-epoxy compound – namely bis(oxiran-2-ylmethyl) furan-2,5-dicarboxylate (DGF) – in consideration of its potential use as monomer for epoxy resins. The synthesis of DGF was conducted via transesterification reaction of 2,5-furandicarboxylic acid dimethyl ester (FDME) with glycidol. A variety of homogeneous, heterogeneous, and enzymatic catalysts were investigated, and the syntheses were carried out avoiding any chlorine-based chemicals and employing green media. The homogeneous route yielded the best results when the reaction was conducted in 2-Me-THF as medium and using triethylamine as a catalyst. DGF was isolated as pure in 82 % yield through a simple liquid-liquid extraction. In the heterogeneous route, triethylamine immobilized on a polymeric polystyrene-divinylbenzene (PS-DVB) support, led to a lower yield due to a moderate substrate conversion. The chemo-enzymatic route employed Candida antarctica lipase B (CAL-B) supported on various Supported Ionic Liquid-Like Phases (SILLPs). In this case DGF yield was only 10–20 %. Interestingly, the reaction led to similar results even in the absence of the enzyme, suggesting that the ionic liquid-like phase on the resin was not a passive support, but it actively participated in promoting the transesterification reaction. Thus, the efficiency of several SILLPs as catalysts was evaluated. Among them, the butyl imidazolium chloride SILLP demonstrated superior catalytic performance compared to supported alkyl ammonium salts leading to 79 %. Furthermore, its stability was very promising, maintaining consistent catalytic efficiency over 12 consecutive cycles.