Carbon-carbon bond formation using aromatics from biomass

The transition to a circular economy requires that we adapt currently used chemical processes to the structurally diverse and often highly oxygenated precursors that are accessible from biomass. In this review, we highlight different examples of carbon-carbon bond formation using aromatics derived from bio-based sources, reported during 2015-2024. Examples of sustainable biomass building blocks include heterocycles such as furfural and hydroxymethylfurfural, obtained from carbohydrates, as well as lignin-based aromatics such as vanillin and eugenol. These have subsequently been applied in a variety of different types of carbon-carbon bond formation, including more classical methods such as aldol condensation and Morita-Baylis-Hillman reactions, but also employing transition metal catalysis, electrochemistry or photochemistry to create new C-C bonds.

Titania-supported molybdenum oxide combined with Au nanoparticles as hydrogen-driven deoxydehydration catalyst of diol compounds

A heterogenous catalyst for deoxydehydration (DODH) reaction was developed using less expensive Mo than Re as the active center. Combination of Mo with anatase-rich TiO2 and Au as the support...

Transition metal-catalyzed deoxydehydration: missing pieces of the puzzle

Deoxydehydration (DODH) is a transformation that converts a vicinal diol into an olefin with the help of a sacrificial reductant.

Deoxygenation reactions in organic synthesis catalyzed by dioxomolybdenum(VI) complexes

Dioxomolybdenum(VI) complexes have been applied as efficient, inexpensive and benign catalysts to deoxygenation reactions of a diverse number of compounds in the last two decades. Dioxomolybdenum complexes have demonstrated wide applicability to the deoxygenation of sulfoxides into sulfides and reduction of N-O bonds. Even the challenging nitro functional group was efficiently deoxygenated, affording amines or diverse heterocycles after reductive cyclization reactions. More recently, carbon-based substrates like epoxides, alcohols and ketones have been successfully deoxygenated. Also, dioxomolybdenum complexes accomplished deoxydehydration (DODH) reactions of biomass-derived vicinal 1,2-diols, affording valuable alkenes. The choice of the catalytic systems and reductant is decisive to achieve the desired transformation. Commonly found reducing agents involved phosphorous-based compounds, silanes, molecular hydrogen, or even glycols and other alcohols.

Effect of Tungsten Species on Selective Hydrogenolysis of Glycerol to 1,3-Propanediol

Glycerol, as the major byproduct of biodiesel industry, is a cheap and green chemical feedstock. Following the expanded production of biodiesel, the oversupply of glycerol has led to increasing research of the catalytic conversion of glycerol. The selective hydrogenolysis of glycerol is an economical and sustainable way to produce 1,3-propanediol, which experiences a global growing demand, and valorize glycerol. However, the secondary hydroxy group of glycerol is sterically hindered by two primary hydroxy groups. As a result, 1,2-propanediol is the preferential product rather than 1,3-propanediol during conventional hydrogenolysis of glycerol. Currently, tungsten-containing bifunctional catalysts with metal and Brønsted acid sites are considered as a highly effective and atom-economical catalytic system for the selective hydrogenolysis of glycerol to 1,3-propanediol. Therefore, this Minireview summarized various tungsten-containing bifunctional catalysts for the hydrogenolysis of glycerol in detail and deeply discussed the relationship between tungsten species, metal active sites, and glycerol for selectively producing 1,3-propanediol.

Molybdenum-Catalyzed Deoxygenation Coupling of Lignin-Derived Alcohols for Functionalized Bibenzyl Chemicals

With the growing demand for sustainability and reducing CO₂ footprint, lignocellulosic biomass has attracted much attention as a renewable, carbon-neutral and low-cost feedstock for the production of chemicals and fuels. To realize efficient utilization of biomass resource, it is essential to selectively alter the high degree of oxygen functionality of biomass-derivates. Herein, we introduced a novel procedure to transform renewable lignin-derived alcohols to various functionalized bibenzyl chemicals. This strategy relied on a short deoxygenation coupling pathway with economical molybdenum catalyst. A well-designed H-donor experiment was performed to investigate the mechanism of this Mo-catalyzed process. It was proven that benzyl carbon-radical was the most possible intermediate to form the bibenzyl products. It was also discovered that the para methoxy and phenolic hydroxyl groups could stabilize the corresponding radical intermediates and then facilitate to selectively obtain bibenzyl products. Our research provides a promising application to produce functionalized aromatics from biomass-derived materials.

Sustainable synthesis of 1,2,3,4-cyclohexanetetracarboxylate from sugar-derived carboxylic acids

Herein, we report a sustainable route for the synthesis of 1,2,3,4-cyclohexanetetracarboxylate from sugar-derived muconic acid and fumaric acid. The key Diels-Alder reaction constructed a cyclohexene framework substituted by four ester groups. The isolated yield of tetramethyl 5-cyclohexene-1,2,3,4-tetracarboxylate was up to 95.5% without any catalyst used. And the hydrogenation reaction of the cycloadduct was catalyzed by commercial RANEY® Ni at room temperature and nearly 100% yield of the cyclohexyl target products was obtained.