A novel route to synthesize 2,5-furandicarboxylic: Direct carboxylation of 2-furoic acid with formate

Furan-2,5-dicarboxylic acid (FDCA) is an important biomass-derived diacid, and it is the most promising substitute for terephthalic acid. The common method of FDCA usually involves 5-hydroxymethylfurfural oxidation. Edible fructose is often used as the feedstock of 5-hydroxymethylfurfural, and the oxidation step would generate undesirable impurities. Herein, FDCA was novelty synthesized by carboxylation of formate and 2-furoic acid (FA) derived from unedible-biomass. This route is potentially advantageous because it is simple to operate and does not require any additional additives. The reaction mechanism has been elucidated by density functional theory (DFT) calculations. In the carboxylation process, the C(sp(2))-H bond of formate (HCOOM) undergoes cleavage, generating the carbon dioxide radical anion (CO2 center dot-. Subsequently, CO2 center dot- attacks the C-5 of FA, forming the C-C bond and ultimately yielding FDCA. The conversion of HCOOM to CO2 center dot- is an effective way to achieve carboxylation reaction. The rate-determining step of the carboxylation reaction is the cleavage of the C(sp(2))-H bond of HCOO- ith activation barrier of 159.11 kJ.mol(-1). The investigation would provide a new strategy for the mechanism of carboxylation reactions, and hold the potential to establish pathways for FDCA production.