A Green Synthesis of 5,5′-[Oxybis(methylene)]bis-2-Furfural: from By-Product to Attractive Bio-Based Platform Chemical

In this work, a green synthetic approach to 5,5'-(oxybis(methylene)]bis-2-furfural (OBMF) from 5-hydroxymethyl-2-furfural (HMF) is reported for the first time. In the optimized reaction conditions, dimethyl carbonate (DMC) is used as the preferred green solvent and iron(III) sulfate as the best catalyst, recyclable up to three times. The HMF self-etherification reaction is conducted both in milligram- and gram-scale with isolated yields up to 99% and 81% respectively. OBMF is further derivatized via reduction to achieve 5,5'-oxybis(methylene)bis(furan-5,2-diyl)dimethanol (OBMF-H), a potential bisphenol-A biobased alternative. Thus, methoxycarbonylation of OBMF-H leads to the biscarboxymethylated derivative (OBMF-DC) employing, once again, DMC as solvent and reagent. Both OBMF-H and OBMF-DC are achieved in high yields and are fully characterized. Furthermore, thermogravimetric analysis of OBMF, OBMF-H, and OBMF-DC establishes that these compounds are more thermally stable than HMF and its derivatives. In fact, they can withstand up to 200 degrees C before undergoing complete degradation rendering OBMF and its derivatives valuable bio-based monomers for bioplastics prepared via polycondensation reaction.