Research Summary
In the modern era, sustainable development for the production of fine chemicals from abundant biomass using various chemical transformations has become a significant trend in scientific research. This approach offers a sustainable alternative to petrochemicals as the primary source of fine chemicals. Lignin, in particular, is an alternative major source of monomeric phenolic compounds, and the oxidation of lignin-based monomeric phenolics for the synthesis of fine chemicals is gaining serious attention. For instance, biomass-derived vanillin or vanillyl alcohol can be oxidized to vanillic acid, which serves as a new building block for the synthesis of various value-added products.
In this context, an air-stable iron(III) complex has been synthesized and used as an effective base-metal catalyst for the selective oxidation of vanillyl alcohol to vanillic acid. The process utilized hydrogen peroxide and tert-butyl hydroperoxide as green oxidants. These peroxidative oxidations of vanillyl alcohol to vanillic acid were performed in metal-free, type-III deep eutectic solvents, serving as green and sustainable reaction media.
After the first set of oxidation reactions, the catalyst and reaction medium were recycled five times without any noticeable decrease in catalytic performance. The CHEM21 green metrics toolkit was also employed to assess the sustainability and green aspects of the optimized oxidation protocol for the conversion of vanillyl alcohol to vanillic acid. The low E-factors (4.65) indicate waste-minimized, sustainable oxidation processes.
Finally, vanillic acid was used as a starting material for the synthesis of several fine chemicals with various potential applications, including flavorants, odorants, surfactants, and bio-based plasticizers.
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