Catalytic Cleavage of the C-O Bond in 2,6-dimethoxyphenol Without External Hydrogen or Organic Solvent Using Catalytic Vanadium Metal

Abstract

Hydrogenolysis of the CO bonds in lignin, which promises to be able to generate fuels and chemical feedstocks from biomass, is a particularly challenging and important area of investigation. Herein, we demonstrate a vanadium-catalyzed cleavage of a lignin model compound (2,6-dimethoxyphenol). The impact of the catalyst in the context of the temperature, reaction time, and the solvent, was examined for the cleavage of the methyl ethers in 2,6-dimethoxyphenol. In contrast to traditional catalytic transfer hydrogenolysis, which requires high pressure hydrogen gas or reductive organic molecules, such as an alcohol and formic acid, the vanadium catalyst demonstrates superior catalytic activity on the cleavage of the CO bonds using water as a solvent. For example, the conversion of 2,6-dimethoxyphenol is 89.5% at 280 • C after 48 h using distilled water. Notably, the vanadium-catalyzed cleavage of the CO bond linkage in 2,6-dimethoxyphenol affords 3-methoxycatechol, which undergoes further cleavage to afford pyrogallol. This work is expected to provide an alternative method for the hydrogenolysis of lignin and related compounds into valuable chemicals in the absence of external hydrogen and organic solvents.

Advancements and Perspectives toward Lignin Valorization via O‐Demethylation

“…Both catalysts were also reported for guiacol (see above). Syringol conversion (89 %) in the presence of vanadium powder in hot pressurized water (280 °C) yielded 43 % pyrogallol and 40 % 3‐methoxycatechol at ≈90 % conversion [133] …”

Hydrogen‐transfer strategy in lignin refinery: Towards sustainable and versatile value‐added biochemicals

“…Furthermore, the refinery of complex product mixtures derived from lignin depolymerization is imperative to enhance the yield and selectivity of desired platform chemicals produced through hydrodeoxygenation processes. [34,35,73,[100][101][102][103][104][105][106][107][108][109][110][111][112][113][114][115][116][117] In the context of biofuel applications, minimizing the oxygen content within these aromatic mixtures is critical for obtaining a more concentrated product range. [118] Conducting hydrodeoxygena-tion under mild conditions may also be beneficial, as it allows for the conservation of specific functional groups; this conservation is advantageous for the subsequent production of functionalized monomers, which have the potential for further value-added conversion processes.…”

“…Furthermore, the refinery of complex product mixtures derived from lignin depolymerization is imperative to enhance the yield and selectivity of desired platform chemicals produced through hydrodeoxygenation processes [34,35,73,100–117] . In the context of biofuel applications, minimizing the oxygen content within these aromatic mixtures is critical for obtaining a more concentrated product range [118] .…”

Emerging Chemical Diversity and Potential Applications of Enzymes in the DMSO Reductase Superfamily

“…Biocatalytic dehydroxylation of catechols under ambient conditions has no equivalent in conventional organic synthesis. Indeed, catechol dehydroxylation typically requires extremely high temperature or elevated pressure in the presence of heterogeneous transition metal catalysts, which are accompanied by low selectivity (63,64). In contrast, catechol dehydroxylases remove the p-hydroxyl group with high regioselectivity (58).…”