Sustainable Production of Pyromellitic Acid from Biomass-Derived Furanic Platform Chemicals

Aromatic poly(carboxylic acid)s, especially terephthalic acid and pyromellitic acid, are extremely important monomers for polyester and polyimide manufacture. Current industrial processes predominantly rely on halogen-promoted oxidation reactions, which require specialized equipment and cause serious environmental pollution. Herein, a novel route was developed to synthesize pyromellitic acid from biomass-derived furanic platform chemicals. The process begins with a Diels–Alder reaction between furan and dimethyl acetylenedicarboxylate, forming an oxygen-bridged cyclohexadiene structure with a yield of 84.4%, and the cycloaddition strategy can also be applied to a variety of substituted furan-based feedstocks. The central diene of dimethyl furan-3,4-dicarboxylate was achieved via a cascade of selective hydrogenation and a retro-Diels–Alder reaction, with an isolated two-step yield of 92.8%. Subsequently, Diels–Alder, deoxy-aromatization, and hydrolysis reactions were integrated to efficiently produce pyromellitic acid, achieving yields higher than 91.3% in each step. Hence, the overall yield of the target product was approximately 65.1%, originating from furan. Preliminary green metrics and life cycle assessment were conducted to calculate the consumption and emissions of the process, thereby indicating its potential environmental friendliness. This work provides an effective methodology for the synthesis of crucial aromatic compounds through the precise design of Diels–Alder and retro-Diels–Alder reactions, paving the way for the production of environmentally friendly polyimide materials from renewable biomass.