lignin-derived monomers, fatty acids, aliphatic alkanes/alkenes or aromatics/ phenolic, vegetable oils, terpenes, C5-C6 sugars, and their furan-based derivatives.Among these biomolecules, 5-(hydroxymethyl)furfural (HMF) -first reported in 1895 -has quickly become the archetype of bio-based platform chemicals. [4][5][6][7][8] HMF is a versatile molecule with a wide range of potential applications in pharmaceuticals, [9,10] biofuels, [11][12][13] biopolymers, [14][15][16] and surfactants. [17] On the other hand, HMF also encompasses some issues such as i) the absence of a cost-efficient scale-up synthesis (currently cost being 960 € kg −1 ), [18] ii) a hydrophilic and polar behavior that prevents its recovery from aqueous media, and iii) a fast degradation due to the formation of dimers, oligomers, and humin during storage. The latter drawback has been partially solved with the addition of a small amount of stabilizer. [19] In fact, it is known that the typical dehydration conditions employed for the HMF synthesis, promote numerous secondary reactions such as (self-) etherification, esterification, aldol condensation, acetalization, and, of course, humin formation. [20] Among these by-products, 5,5′-[oxybis(methylene)]bis-2-furfural (OBMF), detected both during HMF synthesis and as a result of its spontaneous degenerative process, is indeed an interesting compound. [21] To date, OBMF has been only scarcely reported in the literature despite the fact that the first synthetic procedures to this molecule dated back to the end of the XX century. [21][22][23][24] Only in recent years, the interest in OBMF has considerably risen due to its exploitation in the synthesis of macrocycles (16-crown-6), [25] and, most importantly, as a precursor of polyurethanes, polyamides, and polyamines. [26] Table 1 and Figure 1 report an overview of the main synthetic procedures for OBMF available in the literature. Several homogeneous and heterogeneous catalysts were employed.One of the first methodologies reported was the HMF selfetherification reaction (#1, 2, 7; Table 1) generally promoted by acids such as p-toluenesulfonic acid (PTSA), in non-polar organic solvents, that is, benzene, toluene or xylene. This approach was conducted also on a gram-scale, leading OBMF with a yield of up to 76%. [22,27,28] In another less efficient approach, OBMF achieved in 55% yield by thermal dehydration of HMF in dimethyl sulfoxide (DMSO), (#3; Table 1). [23] 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 bis...