Carboxylation Reaction Research Articles

Hydrophilic chitosan: modification pathways and biomedical applications

Chitosan, a natural and abundant polysaccharide, offers several advantageous properties, such as excellent biocompatibility, biodegradability, and antimicrobial activity, making it a highly versatile material. However, its extensive application is hindered by its insolubility in water and most organic solvents, due to numerous intramolecular/intermolecular hydrogen bonds. To overcome this limitation and optimize its benefits, chitosan is often chemically modified to enhance its utility in various industries. Biomedical materials, environmental management, biological papermaking, food preservation, and the daily chemical industry are a few examples. Modified chitosan retains the inherent properties of chitosan and acquires new physicochemical characteristics as a result of introduced functional groups. Hydrophilic modifications typically include carboxylation, phosphorylation, and quaternary ammonium modification reactions. The specific properties and applications of chitosan derivatives depend on the grafted groups. This review summarizes the reaction conditions, properties, and applications of hydrophilic chitosan derivatives in drug delivery and food preservation, serving as a reference for the development and use of chitosan-based biomaterials. <br>The bibliography includes 128 references.

Construction of Polymers with Highly Dispersed Reactive Phases and Open Pores for Catalyzing the Efficient Synthesis of CO2 to α‐Methylene Cyclic Carbonates

AbstractSelective capture of carbon dioxide as a C1 feedstock for the preparation of high‐value chemicals has been recognised as an important way to mitigate the crisis. In this work, a new heterogeneous catalyst, Cu@CP‐PII, was developed through the rational construction of an open‐pore organic skeleton, which is easy to synthesise and highly efficient. With the synergistic effect between the high CO2 affinity of the porous skeleton and the highly dispersed Cu(I) sites of the activated alkynes, it can be used for the efficient preparation of α‐methylene cyclic carbonates at ambient temperature and pressure. The structure and morphology were exhaustively characterised by Solid State 13C‐NMR, FT‐IR, XPS, TEM and N2 adsorption‐desorption tests, and this catalyst possessed a high surface area of 273.7 m2 ⋅ g−1 and uniformly dispersion of CuI. To test its catalytic activity, Cu@CP‐PII in an amount of only 0.4 mol% was used as a catalyst for the carboxylative cyclization reaction of propargylic alcohols with CO2, which resulted in substrate conversions up to 100 % and yields greater than 99 %. In addition, controlled experiments and mechanistic elucidation confirmed that anhydrous and low temperatures are necessary to achieve high selective control of the target product α‐methylene cyclic carbonates.

Density Functional Theory Study of the Mechanism of Ni-Catalyzed Carboxylation of Aryl C(sp2)-S Bonds with CO2: Computational Evidence for the Multifaceted Role of Additive Zn.

The mechanism of Ni-catalyzed carboxylation of aryl C(sp2)-S bonds with CO2 was studied for the first time by density functional theory calculations. We first proposed another possible reaction pathway in which CO2 insertion occurs prior to reduction. Then, we performed calculations on all proposed reaction pathways, and our calculation results show that the pathway in which reduction occurs prior to CO2 insertion is the favored pathway for this reaction. Additionally, our calculations disclose that additive Zn0 acts in multifaceted roles. (1) Zn0 acts as a reductant to reduce the NiI and NiII intermediates. (2) The simultaneously formed ZnIIBr2 can undergo transmetalation with NiI or NiII intermediates to produce an aryl reservoir by forming arylzinc species. (3) ZnIIBr2 can also coordinate to the CO2 to lower the energy barrier of the CO2 insertion step. Moreover, the calculation results suggest that CO2 insertion is the rate-determining step of the reaction, and CO2 is easier to insert into the NiI-Ph bond rather than into the NiII-Ph bond. These calculation results can improve our understanding of the mechanism of the carboxylation process and the multifaceted roles of metal additive Zn0 and provide theoretical guidance for improving the carboxylation reaction.

First row transition metal catalyzed small molecule activation for sustainable organic transformation: Synergy between nature and chemist’s toolbox

In this review we have tried to present our view on the synergy between nature and chemists’ toolbox toward discovery of new reactions. Toward the search for new chemical reactivity, not only chemists learn from nature but nature’s evolutionary pathway perhaps has footprints of chemist’s innovative discoveries and beyond. Taking CO2 as a representative example of an abundant energy rich small molecule resource, we have tried to explore the probable strategies of activating the molecule using first row transition metal catalysts for sustainable organic transformation. Our study has tried to unfold nature’s strategy of CO2 activation and recycling which eventually motivated chemists toward discovery of new chemical reactions and further inspired to expand their toolbox for discovering new reactivities beyond the natural enzyme repertoire. The basic chemical CO2 activation strategy which have been focused in this review are using CO2 as a C1 building block in organic synthesis; catalytic reductive formylation and methylation of amines; carboxylation reactions via CO2 insertion. Additionally, carbonylation reactions with CO2 as CO surrogate has also been discussed. The focus of this review is to correlate nature’s chemical strategies with chemist’s approach to understand the concept involved in the chemical activation and utilization process of CO2 for unlocking new reaction paradigm, both for chemists’ and for nature’s catalytic repertoire.

CARBOXYLATION OF HYDROXYARENES WITH POTASSIUM SALTS OF ALKYLCARBONIC ACID

In this article it was demonstrated that potassium ethyl carbonate can be successfully utilized within the phenol and its derivatives carboxylation. The optimal reaction conditions for m-cresol were determined: substrate to potassium ethyl carbonate ratio 2:1, temperature 180°C, pressure 10 atmospheres and reaction time 6 hours. Importantly, the carboxylation of m-cresol is selective and resulted in the obtaining of 4-methyl-2-hydroxybenzoic acid in 90% yield.To study the impact of the nature and location of substituents in the phenyl ring on the yield of the desired products, carboxylation reactions of various phenol derivatives were carried out with the use of potassium ethyl carbonate. As a result of the investigation, the optimal carboxylation reaction parameters for each of the phenol derivatives were determined.This study may have practical applications in the development of laboratory and manufacturing approaches for the synthesizing of valuable hydroxybenzoic acids and their derivatives. It was discovered that carboxylation of phenol derivatives by potassium ethyl carbonate occurs via electrophilic substitution of the aromatic ring. The most active in this reaction are p-cresol (84%), mcresol (90%), o-cresol (80%) and resorcinol (73%). It was observed that p-chlorophenol (18%), pbromophenol (48%) and p-fluorophenol (58%) showed less pronounced activity.

Transformation and degradation processes of dissolved organic matter in shale oil fracturing flowback water: Implications for environmental management

Shale oil extraction yields shale oil fracturing flowback water (SOFFW) rich in recalcitrant soluble organic compounds, the mismanagement of which can cause ecological harm. The current lack of research on dissolved organic matter (DOM) in SOFFW hampers the informed selection and optimization of oxidative methodologies. This study employed diverse characterizations to investigate the degradation and transformation mechanisms of DOM in SOFFW during Fenton oxidation. It identified three primary components in SOFFW, predominantly humic-like substances, the intensity of which was considerably reduced through oxidation. 2D-COS-FTIR analysis revealed that during oxidation, phenolic organic compounds showed preferential reactivity, followed by compounds containing double bonds and, finally, aliphatic compounds. Fenton oxidation effectively degraded highly unsaturated phenolics and polycyclic aromatic hydrocarbons, simultaneously generating an abundance of aliphatic and oxygen-poor unsaturated phenolic compounds. Through carboxylation, demethylation, and hydrogenation reactions, the proportion of large organic molecules (400–700 Da) decreased, leading to the formation of smaller molecules in the 200–400 Da range. Our findings demonstrate that hydroxyl radicals in the Fenton oxidation process react rapidly with electron-rich compounds, such as highly oxygenated unsaturated phenolics, while showing lower reactivity toward aliphatic substances. These findings substantially contribute to the efficient treatment of SOFFW and offer valuable insights for practical applications.

Increased reactive carboxyl and free alfa-amino groups from fish type I collagen peptides by Alcalase® hydrolysis exhibit higher antibacterial and antioxidant activities

Abstract This study aimed to generate low molecular weight peptides (LMWP) from fish collagen type I hydrolysed by increasing activity of Alcalase® from 0.0 to 12.0 (AU-A per 100 g) at 55 °C and 7.4 of pH for 3 h 40 min. The results showed that all enzyme activity levels caused 34–55 % reductions in protein recovery, 1.0–3.0 folds’ increase in free α-amino groups and 1.7–3.2 folds’ increase in carboxyl groups. Degree of hydrolysis ranged from 20 to 30 % with increasing enzyme activity. The number average molecular weight significantly reduced from 3200 g/mol in 0.0 AU-A per 100 g enzyme activity to 1151, 1398, 1175, 1040 and 1246 g/mol in 2.4, 4.8, 7.2, 9.6 and 12.0 AU-A per 100 g enzyme activities, respectively. Depending upon enzyme activity level, the produced LMWP with reactive carboxyl and amino end-groups exhibited 2.5- to 4.0-fold increases in antioxidant capacity and 1.0–3.5 log cfu/ml inhibition of four pathogen bacteria. Highest inhibition of 2.5 log cfu/ml in Escherichia coli was obtained from 2.4 AU-A per 100 g enzyme activity and 3.5 log cfu/ml in Listeria monocytogenes from 9.6 and 12.0 AU-A per 100 g enzyme activity levels. Infrared spectroscopy clearly identified reactive end-groups and showed remarkably differences in molar absorptivity of various molecular regions between non-enzyme and enzyme treated collagen type I molecule. A 9.6 and 12.0 AU-A per 100 g enzyme activity levels were found optimally effective to generate LMWP. In conclusion, LMWP exhibited high antioxidant and antibacterial activity due to increased functional reactive end-groups, and these bio-active peptides may have greater potentialities in various food and pharmaceutical applications.

Molecular transformation of petroleum compounds by hydroxyl radicals produced upon oxidation of reduced nontronite

At redox interfaces, the interaction between oxygen and structural Fe(II) in minerals produces hydroxyl radicals (●OH); however, the specific reactivity and mechanisms of oxidation of complex petroleum compounds by ●OH remain poorly understood. This study investigates the interaction mechanisms between ●OH generated from reduced nontronite, an Fe-rich clay mineral (NAu-2), and petroleum compounds by employing a suite of wet chemistry, gas chromatography mass spectrometry and Fourier transform-ion cyclotron resonance-mass spectrometry, as well as theoretical calculations. The results showed that the intrinsic structure, composition, solubility, and adsorption of petroleum molecules onto reduced NAu-2 significantly influenced their reactivity with ●OH. Specifically, the aromatic fraction of a crude oil sample exerted a minimal influence on the oxidation rate of structural Fe(II) in reduced NAu-2, but enhanced the production of ●OH by generating environmentally persistent free radicals. ●OH reacted more with water-soluble dissolved organic matter from oil compared to polar compounds. The newly generated molecules by ●OH exhibited a preference for the insoluble (polar) phase. The oxidation of petroleum hydrocarbons by ●OH was mediated through hydrogen atom abstraction and radical adduct formation, followed by dehydrogenation, hydroxylation, and carboxylation reactions. Consequently, the abundance of oxygen-containing compounds in polar compounds increased. However, specific oxidation pathways differed depending on the nature of petroleum compounds. Our results provide insights that oxidation of petroleum compounds by ●OH is vital for mitigating the negative impacts from hydrocarbon contamination and for evaluating the role of these processes in the carbon cycle in redox-active environments.

Harnessing of carboxy containing starch nanoparticles as an adsorbent for Cd (II) ions and methylene blue from waste water effluent: synthesis, metrological characterization and properties

Purpose The novelty addressed here is undertaken by using tailor-made and fully characterized starch nanoparticles (SNPs) having a particle size ranging from 80 to 100 nm with a larger surface area, biodegradability and high reactivity as a starting substrate for cadmium ions and basic dye removal from wastewater effluent. This was done via carboxylation of SNPs with citric acid via esterification reaction using the dry preparation technique, in which a simple, energy-safe and sustainable process concerning a small amount of water, energy and toxic chemicals was used. The obtained adsorbent is designated as cross-linked esterified starch nanoparticles (CESNPs). Design/methodology/approach The batch technique was used to determine the CESNPs adsorption capacity, whereas atomic adsorption spectrometry was used to determine the residual cadmium ions concentration in the filtrate before and after adsorption. Different factors affecting adsorption were examined concerning pH, contact time, adsorbent dose and degree of carboxylation. Besides, to validate the esterification reaction and existence of carboxylic groups in the adsorbent, CESNPs were characterized metrologically via analytical tools for carboxyl content estimation and instrumental tools using Fourier-transform infrared spectroscopy (FTIR) spectra and scanning electron microscopy (SEM) morphological analysis. Findings The overall adsorption potential of CESNPs was found to be 136 mg/g when a 0.1 g adsorbent dose having 190.8 meq/100 g sample carboxyl content at pH 5 for 60 min contact time was used. Besides, increasing the degree of carboxylation of the CESNPs expressed as carboxyl content would lead to the higher adsorption capacity of cadmium ions. FTIR spectroscopy analysis elucidates the esterification reaction with the appearance of a new intense peak C=O ester at 1,700 cm−1, whereas SEM observations reveal some atomic/molecules disorder after esterification. Originality/value The innovation addressed here is undertaken by studying the consequence of altering the extent of carboxylation reaction expressed as carboxyl contents on the prepared CESNPs via a simple dry technique with a small amount of water, energy and toxic chemicals that were used as a sustainable bio nano polymer for cadmium ions and basic dye removal from wastewater effluent in comparison with other counterparts published in the literature.

Carboxylic Acid-Enabled Vinylene Transfer Reaction by Co(III) Catalyst: Scope and Applications to the Five-Step Total Synthesis of Protoberberine Alkaloids Containing Free Hydroxyl Group without Protection.

A Co(III)-catalyzed vinylene transfer reaction enabled by carboxylic acid is presented. This redox-neutral transformation tolerates various functional groups, including free hydroxyl groups, and features practicality. Five-step routes based on the vinylene transfer reaction and Heck annulation have been devised to the total synthesis of 8-oxodehydrodiscretamine and 2-demethyl-oxypalmatine without the protection of the free hydroxyl functionality.

Low energy consumption pathway to improve sulfamethoxazole degradation by carbon fiber@Fe3O4-CuO: Electrocatalysis activity, mechanism and toxicity

Catalysts play a pivotal role in advanced oxidation processes for the remediation of organic wastewater. In this study, a 3D carbon fiber@Fe3O4-CuO catalyst was fabricated, and its efficacy for persulfate activation to remove sulfamethoxazole (SMX) was investigated at extremely low current density. The results of characterization revealed that the catalyst was uniformly distributed on the carbon fiber, and the loaded catalyst was Fe3O4-CuO nanoparticles with a diameter range of 20–50 nm. The SMX removal rate was significantly enhanced at extremely low current density by the metallic oxide catalyst loaded on carbon fiber. Approximately 90 % of SMX was degraded within 90 min when the electric current density was set at 0.1 mA cm−2. This modification process not only improved the persulfate activation efficiency but also enhanced the generation of hydrogen peroxide. Both radical and non-radical pathways were involved in the degradation of SMX. The degradation pathway mainly included hydroxylation, carboxylation, aniline cleavage, and desulfonation reactions. The quantitative structure–activity relationship model indicated that the potential risk of intermediate products to fish, daphnia, and green algae significantly decreased during the electrocatalytic oxidation process. This study provides a novel strategy for persulfate activation, which can significantly enhance the degradation efficiency, toxicity abatement, and energy usage effectiveness of electrocatalytic technology.

Immobilization of Thermoplasma acidophilum Glucose Dehydrogenase and Isocitrate Dehydrogenase Through Enzyme-Inorganic Hybrid Nanocrystal Formation

The development of green catalysts, specifically biocatalysts, is crucial for building a sustainable society. To enhance the versatility of biocatalysts, the immobilization of enzymes plays a vital role as it improves their recyclability and robustness. As target enzymes to immobilize, glucose dehydrogenases and carboxylases are particularly important among various kinds of enzymes due to their involvement in two significant reactions: regeneration of the reduced form of coenzyme required for various reactions, and carboxylation reactions utilizing CO2 as a substrate, respectively. In this study, we immobilized Thermoplasma acidophilum glucose dehydrogenase (TaGDH) and T. acidophilum isocitrate dehydrogenase (TaIDH) using a previously reported method involving the formation of enzyme-inorganic hybrid nanocrystals, in the course of our continuing study focusing on carboxylation catalyzed by the free form of TaGDH and TaIDH. Subsequently, we investigated the properties of the resulting immobilized enzymes. Our results indicate the successful immobilization of TaGDH and TaIDH through the formation of hybrid nanocrystals utilizing Mn2+. The immobilization process enhanced TaIDH activity, up to 211%, while TaGDH retained 71% of its original activity. Notably, the immobilized TaGDH exhibited higher activity at temperatures exceeding 87 °C than the free TaGDH. Moreover, these immobilized enzymes could be recycled. Finally, we successfully utilized the immobilized enzymes for the carboxylation of 2-ketoglutaric acid under 1 MPa CO2. In conclusion, this study represents the first immobilization of TaGDH and TaIDH using the hybrid nanocrystal forming method. Furthermore, we achieved significant activity enhancement of TaIDH through immobilization and demonstrated the recyclability of the immobilized enzymes.

(De)carboxylation mechanisms of heteroaromatic substrates catalyzed by prenylated FMN-dependent UbiD decarboxylases: An in-silico study

The UbiD enzymes are proposed to catalyze reversible (de)carboxylation reaction of unsaturated carboxylic acids using prenylated flavin mononucleotide (prFMN) as a cofactor. This positions UbiD enzymes as promising candidates for converting CO2 into valuable chemicals. However, their industrial-scale biotransformation is currently constrained by low conversion rates attributed to thermodynamic limitations. To enhance the carboxylation activity of UbiD enzymes, a molecular-level understanding of the (de)carboxylation mechanisms is necessary. In this study, we investigated the reaction mechanisms of heteroaromatic substrates catalyzed by PtHmfF, PaHudA, and AnlnD enzymes using molecular dynamics (MD) simulations and free energy calculations. Our extensive mechanistic study elucidates the mechanisms involved in the formation of the initial prFMN-substrate intermediate. Specifically, we observed nucleophilic attack during decarboxylation, while carboxylation reactions involving furoic acid, pyrrole, and indole tend to favor a 1,3-dipolar cycloaddition mechanism. Furthermore, we identified proton transfer as the rate-limiting step in the carboxylation reaction. In addition, we considered the perspectives of reaction energies and electron transfer to understand the distinct mechanisms underlying decarboxylation and carboxylation. Our calculated free energies are consistent with available experimental kinetics data. Finally, we explored how different rotamers of catalytic residues influence the efficiency of the initial intermediate formation.

Noble metal free double helix binuclear Cu(I) complex as catalyst for carboxylative cyclization of propargylamines with atmospheric carbon dioxide toward oxazolidinones synthesis under mild conditions

The application of economically abundant, renewable and C1-feedstock, carbon dioxide into organically important compounds is considered as the hot topic in modern aspects. In this prospective, a binuclear double helix copper (I) complex (1) was synthesized through insitu reaction between quinolone-2-carbaldehyde and succino-hydrazide with copper (II) nitrate hexahydrate. Single crystal X-ray analysis of complex 1, clearly explained that both tetra co-ordinated Cu(I) ions are in tetrahedral geometric environment, having suprmolecular network arrangement via weak interaction of H-bonding, π…π stacking and CH…π stacking. The complex 1 was found to be effectively active catalyst in carboxylative cyclization reaction of propargylic amines with carbon dioxide towards oxazolidinones synthesis under atmospheric pressure and mild reaction conditions. Due to the initiation of side reaction by –NH2 group of primary propargyliamines, which reduces the yield percentage of respective oxazolidinones as a result the carboxylative cyclization reaction of primary propargylic amines, was rarely developed. In this work both primary and secondary propargylamines smoothly undergoes through this catalytic reaction and produced high percentage of desired oxazolidinones product. Again neat condition for this catalytic reaction makes the methodology more environmentally benign and sustainable. The complex 1 showed luminescent property. Moreover DFT methods were utilized in order to explain the probable mechanistic pathway of carboxylative cyclization reaction.

Probing the role of protein conformational changes in the mechanism of prenylated-FMN-dependent phenazine-1-carboxylic acid decarboxylase

Phenazine-1-carboxylic acid decarboxylase (PhdA) is a prenylated-FMN-dependent (prFMN) enzyme belonging to the UbiD family of decarboxylases. Many UbiD-like enzymes catalyze (de)carboxylation reactions on aromatic rings and conjugated double bonds and are potentially valuable industrial catalysts. We have investigated the mechanism of PhdA using a slow turnover substrate, 2,3-dimethylquinoxaline-5-carboxylic acid (DQCA). Detailed analysis of the pH dependence and solvent deuterium isotope effects associated with the reaction uncovered unusual kinetic behavior. At low substrate concentrations, a substantial inverse solvent isotope effect (SIE) is observed on Vmax/KM of ∼ 0.5 when reaction rates of DQCA in H2O and D2O are compared. Under the same conditions, a normal SIE of 4.15 is measured by internal competition for proton transfer to the product. These apparently contradictory results indicate that the SIE values report on different steps in the mechanism. A proton inventory analysis of the reaction under Vmax/KM and Vmax conditions points to a "medium effect" as the source of the inverse SIE. Molecular dynamics simulations of the effect of D2O on PhdA structure support that D2O reduces the conformational lability of the enzyme and results in a more compact structure, akin to the active, "closed" conformer observed in crystal structures of some UbiD-like enzymes. Consistent with the simulations, PhdA was found to be more stable in D2O and to bind DQCA more tightly, leading to the observed rate enhancement under Vmax/KM conditions.

Surveying the scope of aromatic decarboxylations catalyzed by prenylated-flavin dependent enzymes.

The prenylated-flavin mononucleotide-dependent decarboxylases (also known as UbiD-like enzymes) are the most recently discovered family of decarboxylases. The modified flavin facilitates the decarboxylation of unsaturated carboxylic acids through a novel mechanism involving 1,3-dipolar cyclo-addition chemistry. UbiD-like enzymes have attracted considerable interest for biocatalysis applications due to their ability to catalyse (de)carboxylation reactions on a broad range of aromatic substrates at otherwise unreactive carbon centres. There are now ∼35 000 protein sequences annotated as hypothetical UbiD-like enzymes. Sequence similarity network analyses of the UbiD protein family suggests that there are likely dozens of distinct decarboxylase enzymes represented within this family. Furthermore, many of the enzymes so far characterized can decarboxylate a broad range of substrates. Here we describe a strategy to identify potential substrates of UbiD-like enzymes based on detecting enzyme-catalysed solvent deuterium exchange into potential substrates. Using ferulic acid decarboxylase (FDC) as a model system, we tested a diverse range of aromatic and heterocyclic molecules for their ability to undergo enzyme-catalysed H/D exchange in deuterated buffer. We found that FDC catalyses H/D exchange, albeit at generally very low levels, into a wide range of small, aromatic molecules that have little resemblance to its physiological substrate. In contrast, the sub-set of aromatic carboxylic acids that are substrates for FDC-catalysed decarboxylation is much smaller. We discuss the implications of these findings for screening uncharacterized UbiD-like enzymes for novel (de)carboxylase activity.

Pd((R)-DTBM-SEGphos)Cl2-catalyzed kinetic resolution of tertiary propargylic alcohols

A variety of optically active tertiary propargylic alcohols and tetrasubstituted 2,3-allenoic acids have been synthesized via a Pd((R)-DTBM-SEGphos)Cl2-catalyzed carboxylative kinetic resolution reaction of racemic tertiary propargylic alcohols.

Enhanced carboxylation of furoic salt with CO2 by ZnCl2 coordination for efficient production of 2,5-furandicarboxylic acid.

C-H carboxylation of furoic acid (FA) with CO2 is an atom-efficient strategy to produce 2,5-furandicarboxylic acid (2,5-FDCA) from lignocellulose. The existing carbonate-promoted CO2 carboxylation processes rely on the use of large amounts of expensive Cs2CO3 as a deprotonating reagent and molten salt. Substitution of Cs with other cheap and abundant alkali ions (such as K and Na) can reduce the use of Cs, but it faces the problem of a low yield of 2,5-FDCA. This study found that the addition of catalytic amounts of ZnCl2 as a Lewis acid can increase the yield of 2,5-FDCA in the CO2 carboxylation reaction of Na/K-FA in a molten salt reaction system. 1H NMR analysis and DFT calculations confirmed that ZnCl2 coordinates with the furan ring through electron transfer from the conjugated furan ring to Zn2+, thereby activating the H at the C5 position of Na/K-FA. This coordination lengthened the C5-H bond and lowered its heterolytic dissociation energy, making it more susceptible to being deprotonated by CO32- and subsequently carboxylated by CO2. The developed Lewis acid coordination strategy provides a new idea for the efficient construction of C-C bonds between CO2 and aromatics through carbonate-promoted C-H carboxylation.

Carboxylation reactions for the sustainable manufacture of chemicals and monomers

Carboxylation is a promising and versatile technology for producing industrially valuable products, being a potential process for future use of captured CO2. Enzymatic and thermochemical routes are the closest to being scaled up.

Electrosynthetic Carboxylation of Biomass-Derived Compounds in Ionic Liquids

Chemical production from renewable biomass and CO2 is a sustainable alternative to the current fossil based chemical industry as it will enable significant reduction of greenhouse gas emissions. CO2 is a desirable chemical building block as it is abundant and steadily becoming more available as carbon capture technologies are maturing. However, activation and valorization of CO2 remains a challenge due to its thermodynamic stability and kinetic inertness. CO2 activation has been demonstrated with thermal, (photo)catalytic and electrochemical methods, and especially the electrochemical approach allows for mild reaction conditions and high efficiency. In this context, the synthesis of carboxylic acids by electrosynthetic carboxylation represents an interesting strategy for valorization of biomass-derived alcohols and CO2.In electrosynthesis, a supporting electrolyte salt is needed in the reaction medium to ensure high conductivity. A major drawback of using such a supporting electrolyte salt is increased waste generation. However, by replacing supporting electrolyte salts with recyclable ionic liquids the waste generation can in theory be avoided. In addition, ionic liquids can provide a highly conducting reaction medium with a sufficiently large electrochemical window allowing CO2 activation to take place. Furthermore, room temperature ionic liquids are especially suitable for electrosynthetic carboxylation reactions due to their high CO2 absorption capacity.In this work, we present preliminary results, including cyclic voltammetry and reaction optimization studies, for electrosynthetic C-O activation and carboxylation of biomass-derived compounds with room temperature ionic liquids as electrolytes.