Synthesis of [2,2’]Bifuranyl‐5,5’‐dicarboxylic Acid Esters via Reductive Homocoupling of 5‐Bromofuran‐2‐carboxylates Using Alcohols as Reductants^†

Abstract

Bifuranyl dicarboxylates | Homocoupling | Bromination | Green reductant Herein, we describe an environmentally benign and cost-effective protocol for the synthesis of valuable bifuranyl dicarboxylates, starting with α-bromination of readily accessible furan-2-carboxylates by LiBr and K 2 S 2 O 8. Furthermore, the bromination intermediate product 5-bromofuran-2-carboxylates were then conducted in a palladium-catalyzed reductive homocoupling reactions in the presence of alcohols to afford bifuranyl dicarboxylates. One of the final products in this protocol, *2,2'+bifuran-5,5'-dicarboxylic acid esters, are essential monomers of poly(ethylene bifuranoate), which can be served as an green and versatile alternative polymer for traditional poly(ethylene terephthalate) that is currently common in technical plastics.

Template‐Oriented Polyaniline‐Supported Palladium Nanoclusters for Reductive Homocoupling of Furfural Derivatives

“…In the reductive coupling reaction, ethanol reduces some of the Pd 2 + to Pd 0 , and then Pd 0 participates in the oxidative addition of the CÀ Br bond. Moreover, Pd 2 + species also are the key active centers involved in the reductive coupling, [32] which can contribute to the reaction process in a synergistic manner. Thus, the used Pd/ɛ-PANI catalyst still maintains good catalytic performance.…”

Nickel‐Electrocatalyzed Synthesis of Bifuran‐Based Monomers

“…[30] However, in comparison to FDCA synthesis, the synthesis of bifuran monomers is less established. A typical strategy involves using Pd-catalysis in either BrÀ Br homocoupling, [30][31][32][33][34] Mizoroki-Heck, [28,35] or direct CÀ Hfunctionalization. [36,37] Other approaches include oxidative homocoupling of Grignard reagents [38] and nickel-catalyzed homocoupling of ethyl 5-bromofuroate.…”

“…[36,37] Other approaches include oxidative homocoupling of Grignard reagents [38] and nickel-catalyzed homocoupling of ethyl 5-bromofuroate. [36] Some common hindrances in these protocols are the use of expensive palladium catalysts, [28,[30][31][32][33][34][35][36][37] poisonous CO, [34,39] or metal powders [33,36] as reductants.…”