Decarboxylation Research Articles

Mesoporous multi-shell spongy nanosphere NiCo metal/metal oxide hybrid for decarboxylation of fatty acid and upgrading of sludge bio-crude

A mesoporous, multi-shell, spongy nanosphere NiCo metal/metal oxide hybrid was synthesized using glucose reduction method, and the metal/metal oxide ratio can be regulated by adjusting the amount of glucose. The NiCo metal/metal oxide hybrid outperformed NiCo metal catalyst on decarboxylation reaction, and achieved a 100 % conversion of stearic acid and a 98 % yield of heptadecane under 1 MPa H2 at 280 °C for 3 h. Despite of that metal active sites are well recognized responsible for decarboxylation, the better performance of hybrid was attributed to the co-existence of metal oxide and carbon that played an important role in separating metal particles and preventing them from aggregation, and thus exposed more active metal sites. Moreover, electron transfer from metal oxide to metal has been detected, which facilitated the adsorption of the carboxyl carbocation on metal sites and the concomitant efficient decarboxylation. The catalyst also performed efficiently on the catalytic upgrading of sludge bio-crude.

Towards Bio-Crude Refinery Integration: Hydrodeoxygenation and Co-Hydroprocessing with Light Cycle Oil

Hydrothermal liquefaction of solid waste has been gaining more and more attention over the last few years. However, the properties of the HTL product, i.e., biocrude, are limiting its direct utilization. As a result, HTL biocrude upgrading is essential to improve its quality. The main objective of the current research is to study the hydrotreatment stabilization of HTL biocrude, produced from spent coffee grounds, utilizing commercial hydrotreated catalysts, and also to investigate the integration of the stabilized biocrude into a light cycle oil (LCO) hydrotreatment plant for coprocessing to target hybrid fuel production. The results have shown that hydrotreatment is a very promising technology that can successfully remove the oxygen content from raw biocrude by hydrodeoxygenation, decarbonylation and decarboxylation reactions, leading to a stabilized product. The stabilized product can be easily blended with the LCO stream of a typical refinery, leading to the production of jet and diesel boiling range hydrocarbons, favoring at the same time the hydrogen consumption of the process. The findings of this manuscript set the basis for future research targeting the production of renewable advanced biofuels from HTL biocrude from municipal waste.

Diversity Oriented Routes to Thiopeptide Antibiotics: A Solution to the "Thiazole Problem".

The Goossen decarboxylative coupling reaction enables the union of thiazole-2-carboxylic acids with a 2-pyridyl triflate, leading to the formation of pyridine-thiazole clusters of the kind found in thiopeptide antibiotics. The method avoids problematic or technically challenging reaction sequences involving 2-thiazolyl organometallics, facilitating the investigation of the structure-activity relationship of the thiopeptides.

NADH Analogues Enable Metal- and Light-Free Decarboxylative Functionalization.

Here we report a metal- and light-free decarboxylative functionalization approach enabled by reduced nicotinamide adenine dinucleotide (NADH) analogues. The efficient and operationally simple approach, conducted in 5 minutes from in-situ preparation of aryliodine (III) dicarboxylates under open-air and ambient conditions, enables diverse bond formation and exhibits a broad substrate scope of over 70 examples. Late-stage functionalization of drug molecules and natural products further demonstrates the synthetic utility of this method. Combined experimental and computational studies elucidate the mechanistic pathway. These transformations streamline the synthesis of sp3 carbon-enriched compounds, adding a new dimension to classical decarboxylative reactions.

NADH Analogues Enable Metal‐ and Light‐Free Decarboxylative Functionalization

Here we report a metal‐ and light‐free decarboxylative functionalization approach enabled by reduced nicotinamide adenine dinucleotide (NADH) analogues. The efficient and operationally simple approach, conducted in 5 minutes from in‐situ preparation of aryliodine (III) dicarboxylates under open‐air and ambient conditions, enables diverse bond formation and exhibits a broad substrate scope of over 70 examples. Late‐stage functionalization of drug molecules and natural products further demonstrates the synthetic utility of this method. Combined experimental and computational studies elucidate the mechanistic pathway. These transformations streamline the synthesis of sp3 carbon‐enriched compounds, adding a new dimension to classical decarboxylative reactions.

Synthesis of Difuropyridines from Chitin‐Derived 3‐Acetamidofuran and their Application to Photocatalytic Reactions

AbstractDifuropyridines have been prepared from aldehydes and chitin‐derived 3‐acetamidofuran (3AF) under acid‐catalyzed conditions. Difuropyridines were comprehensively synthesized for the first time. The synthesized difuropyridines can be applied to prepare fluorescent probe analogs or catalyze decarboxylative reactions as photocatalysts.

Two birds with one stone: Mussel-inspired anchoring strategy enabling full-spectrum utilization and superior carriers transfer capacity for efficient photocatalytic degradation and antibacterial

Antibiotic pollution that often leads to the increases in the prevalence of resistance represents unneglectable risks to human health. Photocatalysis shows great potential in addressing the antibiotic pollution issue. However, developing photocatalysts integrating full-spectrum photocatalysis and self-adaptive antibacterial performances still remains challenges due to the limited utilization rate of light and carrier transfer capacity. Herein, a mussel-inspired anchoring strategy was employed to fabricate polydopamine coated Hydrothermal carbon carbide ZIF-8ZnO (PDA@HTCC/ZIF-8ZnO) heterojunction photocatalyst. The PDA coating was used as a transition layer to promote the heterogeneous nucleation of ZIF-8 on HTCC. Benefiting from the interfacial connections formed by metal coordination interactions between catechol groups of PDA coating and metal sites of ZIF-8, the carrier transfer capacity of PDA@HTCC/ZIF-8ZnO was improved and the range of light that can be utilized for the PDA@HTCC/ZIF-8ZnO was broadened. Therefore, the PDA@HTCC/ZIF-8ZnO heterojunction presented outstanding full-spectrum photocatalytic degradation and antibacterial performances. The full-spectrum degradation efficiency of tetracycline by PDA@HTCC/ZIF-8ZnO reached 98.7 % in 50 min. Moreover, the antimicrobial efficacy of PDA@HTCC/ZIF-8ZnO against E. coli exceeded 90 % under both light and dark conditions. The promotion effect of PDA transition layer on electrons transfer has been confirmed by DFT calculations. Under light irradiation, PDA@HTCC/ZIF-8ZnO gradually degrades tetracycline through demethylation, deamination, decarboxylation reactions, and ring-opening reactions, ultimately generating CO2 and H2O. This innovative strategy benefits the future heterojunction photocatalysts design for efficient solution of antibiotics pollution and the derivative drug-resistant bacteria issues.

Hydrothermal liquefaction of diverse plastics using water and seawater

In this study, a variety of plastics are converted to their monomers, fuel range hydrocarbons and other platform chemicals using hydrothermal liquefaction (HTL) at sub-critical (350 °C), near-critical (400 °C) and super-critical (450 °C) temperatures. The effect of seawater as a medium on the HTL of plastics is also studied. Polymers like polycarbonate (PC), acrylonitrile–butadiene–styrene (ABS), polyamides (PA-6, PA-66), and polyoxymethylene (POM) liquefied effectively at 350 °C, while polyolefins like polyethylene (PE) and polypropylene (PP) required ≥ 400 °C. HTL of polystyrene (PS) resulted in the highest oil yield (93 wt%) and energy recovery from oil (93.5 %) at 450 °C. HTL of PC, PS and ABS led to the formation of phenols and benzene derivatives, while polyethylene terephthalate (PET) and PA-6 formed their monomers terephthalic acid and caprolactam, respectively. Crude oils from PP and PE contained fuel grade aliphatic hydrocarbons with carbon chain length ranging between C7 and C36. Highest calorific value was recorded for the oil from PP (46.3 MJ kg−1) at 400 °C. The use of seawater generally reduced the oil yields from all the plastics, except ABS, PET and PP. The production of benzoic acid from PET was enhanced, while the selectivity to caprolactam from PA-6 decreased when seawater was used, possibly due to the enhanced decarboxylation and aromatization reactions induced by the ions in the aqueous phase. In general, the crude oil from HTL of PC, PS, ABS and polyamides are suitable for sustainable production of specialty chemicals and monomers, while that from PE and PP are good candidates for sustainable transportation fuels.

Visible-Light-Mediated Three-Component Decarboxylative Coupling Reactions for the Synthesis of 4-Alkylpyridines.

4-Alkylation of pyridines has been achieved by a photocatalyzed three-component reaction of an olefin, an aryloxyacetic acid, and cyanopyridine using Ir[dF(CF3)ppy]2(dtbbpy)PF6 as a photocatalyst. In this way, a new type of 4-alkylpyridines bearing aryl and aryloxy substituents on the phenyl was accessed with potential pharmaceutical value. In addition to mild reaction conditions, the method has several other advantages, including a multicomponent one-pot protocol, good functional group tolerance, and easy amplification of the reaction scale. The reaction mechanism has been clarified by control experiments and computation of the reaction energy profile.

Ru-Catalyzed Ortho C-H Alkylation of 4-Aryl-pyrrolo[2,3-d]pyrimidines with Diazo Compounds: An Access to Fluorescent Fused Heteroarenes.

A Ru(II)-catalyzed migratory insertion of carbene into ortho C-H bonds of 4-aryl-pyrrolo[2,3-d]pyrimidines has been developed. This transformation endows the facile fabrication of C-C bonds with high atom economy, good regioselectivity, and wide functional group tolerance, exploiting the directing properties of pyrimidinic nitrogen. In addition, the planar polycyclic pyrrolo-pyrimido-isoindole framework has been accomplished from a cascade reaction of bromination, cyclization, and decarboxylation of synthesized products. Furthermore, the fluorescence properties of C-N annulated compounds have also been determined, which are valuable in the field of fluorescence properties of heterocycles.

Cavity-Based Discovery of New Fatty Acid Photodecarboxylases.

Light-dependent fatty acid photodecarboxylases (FAPs) hold significant potential for biotechnology, due to their capability to produce alka(e)nes directly from the corresponding (un)saturated natural fatty acids requiring light as the only reagent. This study expands the family of FAPs through cavity-based enzyme discovery methods. Thirty enzyme candidates with potential photodecarboxylation activity were identified by matching the cavities of four related template structures against the Protein Data Bank's flavoproteins, a library of proteins identified via the Foldseek Search Server, and homology models of sequences resulting from BLAST. Subsequent docking experiments narrowed this library to ten promising enzymes, which were expressed and assessed in vitro, identifying four photodecarboxylases. Out of these enzymes, the GMC oxidoreductase from Coccomyxa sp. Obi (CoFAP) was characterized in detail, which revealed high activity in the decarboxylation reactions of palmitic acid and octanoic acid and a broad pH tolerance (pH 6.5-9.5).

Oxidation of 4-hydroxybenzoic acid in strongly alkaline and high-salt solutions via ultrasonic-assisted ozone: Helping radioactive waste disposal and environmental safety

4-Hydroxybenzoic acid (4-HBA), as a gibbsite dissolution inhibitor and typical personal care products (PPCPs), seriously troubles radioactive waste disposal and environmental safety. This work studies the degradation mechanism of 4-HBA in ultrasonic-assisted ozonation in strongly alkaline and high-salt solutions, and comprehensively evaluates its environmental lifetime. Ultrasonic can significantly increase the effect of ozone by 1.52 times, making the degradation rate of 4-HBA reach 63.49 % within 60 min. The better electrochemical performance indicates that the redox reaction between US/O3 system and 4-HBA is more prominent. Experimental analysis and density functional theory (DFT) calculations show that the effects of OH, 1O2, O2−, and others on the degradation of 4-HBA are 56.6 %, 17.8 %, 22.1 %, and 3.5 % respectively, and HO3 is the most important precursor for OH evolution. Mechanistic exploration and DFT calculations show that degradation behavior of 4-HBA in strongly alkaline and high-salt solutions, i.e., decarboxylation reaction, ring opening, hydroxylation, aldol condensation, and hydrogenation, is significantly different from acidic or neutral solutions. Based on the environmental lifetime assessment of the intermediate product, US/O3 technology can help reduce the toxicity of 4-HBA. The US/O3 process is used to remove 4-HBA from strongly alkaline and high-salt solutions, which has huge potential economic benefits in the fields of nuclear waste chemistry and environment.

Photoinduced Metal-Free Decarboxylative Fluoroalkylation of Alkenes for the Synthesis of N-Arylbutanamides and Oxindoles.

The visible light-induced decarboxylative cascade reaction of fluoroalkyl carboxylic acids has been achieved for the efficient synthesis of fluorinated compounds. However, most of the transformations rely on noble iridium metal complex. Herein, a visible light-induced metal-free decarboxylative cascade reaction of fluoroalkyl carboxylic acids has been realized. This protocol features simple operation, transition metal free, and good functional group tolerance.

Light-Mediated Direct Decarboxylative Giese Aroylations without a Photocatalyst.

Previous light-mediated approaches to the direct decarboxylative Giese aroylation reaction have mainly relied on the use of a photocatalyst and a reductive quenching pathway. By exploiting a mechanistically distinct oxidative protocol, we have successfully developed a photocatalyst-free, light-mediated direct Giese aroylation methodology.

Electrochemical Decarboxylation Coupling Reactions.

Carboxylic acids are attractive synthetic feedstocks with stable, non-toxic, and inexpensive properties that can be easily obtained from natural sources or through synthesis. Carboxylic acids have long been considered environmentally friendly coupling agents in various organic transformations. In recent years, electrochemically mediated decarboxylation reactions of decarboxylic acids and their derivatives (NHPI) have emerged as effective new methods for constructing carbon-carbon or carbon-heterocarbon chemical bonds. Compared with transition metal and photochemistry-mediated catalytic reactions, which do not require the addition of oxidants and strong bases, electrochemically-mediated decarboxylative transformations are considered a sustainable strategy. In addition, various functional groups tolerate the electrochemical decarboxylation conversion strategy well. Here, we summarize the recent electrochemical decarboxylation reactions to better elucidate the advantages of electrochemical decarboxylation reactions.

COMPARATIVE STUDY USING CFD OF COUNTER-CURRENT AND CO-CURRENT HYDROTREATING REACTORS USING JATROPHA CURCAS L VEGETABLE OIL

In this work, mathematical modeling and CFD simulation of two countercurrent and cocurrent hydrotreatment reactors were carried out, validating the results with a drained bed reactor (TBR), a commercial CoMo/γ-Al2O3 catalyst was used, the material the raw material was Jatropha Curcas L vegetable oil. The operating conditions were temperature 380 ° C, pressure 8 MPag. The kinetic model that was used considered 13 reactions that involve processes of decarboxylation, decarbonization, hydrodeoxygenation and hydrocracking reactions for triolein and tristearin triglycerides. The CFD simulation was carried out in Fluent 18.2 in a transient state and in 3D, considering the standard κ - ε turbulence models, Eulerian multiphase model and porous medium model, it was shown that the countercurrent reactor has less pressure drop than the countercurrent, the conversion the countercurrent reactor has a greater conversion of reactants of 99%, the generation of products from the countercurrent reactor has higher concentrations than the cocurrent reactor, this is because it has more contact areas between phases in the reactor.

Valorization of olive mill wastewater as a process medium in co-hydrothermal carbonization with Sicilian agro-wastes: effects of interaction on product yield and properties

This work explores the valorization of residual olive mill wastewater as a process aqueous medium for co-hydrothermal carbonization (co-HTC) of typical Sicilian agro-wastes (tangerine and orange peel wastes). Co-HTC experiments were carried out at 180 and 220 °C to assess the interaction between the feedstocks. Synergistic effects increased the yield of hydrochar and gas phases while antagonism altered the formation of aqueous products. Compared to the expected value, hydrochar yield was increased by 37 wt%, on average, while the interaction effect on gas phase was weaker (+23 wt%, on average) and increased with temperature. Both the retention of unhydrolyzed primary char and the recapture of secondary char phases from process water enhanced the hydrochar recovery in different ways according to feedstock nature and co-HTC conditions. On the basis of hydrochars characterization through elemental analysis and surface functionality, the degree of carbonization was significantly improved after co-HTC due to promoted dehydration and decarboxylation reactions. As result, co-hydrochars exhibited a moderately higher energy content and a greater thermal stability compared to samples obtained from HTC of individual substrates. Co-hydrochars also retained relatively high amounts of nutrients such as phosphorus, potassium and calcium, which could enable their use as soil improvers.

An Enantioselective Decarboxylative Glycolate Aldol Reaction.

Herein, we report the application of a benzyloxy-functionalized malonic acid half thioester as an activated ester equivalent in a highly enantioselective decarboxylative glycolate aldol reaction. This robust method operates at ambient temperature, tolerates air and moisture, and generates CO2 as the only byproduct. The synthetic applicability of the method is demonstrated by the large-scale enantiodivergent synthesis of α-benzyloxy-β-hydroxybutyric acid thioester and its subsequent conversion to diverse polyoxygenated building blocks, deoxy-sugars, and (-)-angiopterlactone B.

Comparative profiling of the absorbed compounds and metabolites, and pharmacokinetic studies of Danshen-Chuanxiong herb pair in rat plasma and brain using liquid chromatography-tandem mass spectrometry

Danshen-Chuanxiong (DS-CX) was a classic herb pair commonly used to treat ischemic stroke. Nevertheless, the metabolic conversion and pharmacokinetic behavior of DS-CX in vivo remains unclear. This work aimed to reveal the in vivo metabolic behavior of DS-CX through establishing metabolic profiles and performing multicomponent pharmacokinetics analysis. The mass defect filtering (MDF) strategy integrated with UHPLC-QTOF-MS was firstly developed to characterize the metabolites of DS-CX in rats’ plasma and brain. Moreover, a sensitive UHPLC-QQQ-MS method was utilized to perform the comparative pharmacokinetic studies of major active ingredients of DS-CX in rats’ plasma. A total of 111 exogenous compounds (29 prototype compounds and 82 metabolites) were identified in rat biological samples. The major metabolic pathways were hydroxylation, methylation, deoxidation, dehydration, hydrogenation, demethylation, hydrolysis, decarboxylation and glucuronidation binding reactions. According to the results of metabolites profiling, sixteen active compounds (8 phenolic acids, 5 phthalides and 3 tanshinones) were selected as markers for further comparative pharmacokinetics study. Compared with the oral administration of DS or CX alone, the higher Cmax of salvianolic acid B, crytotanshinone and tanshinone IIA; the shorter Tmax of lithospermic acid, rosmarinic acid and tanshinone IIA; as well as the higher AUC0−∞ of ferulic acid, rosmarinic acid, salvianolic acid B, senkyunolide I and crytotanshinone, could be found after co-administration of DS-CX (P < 0.05). This study provided the overall knowledge of metabolites profiling of DS-CX in vivo, which would help to understand the effective material basis and promote the clinical application of DC-CX herb pair.

Enhanced removal of recalcitrant naphthenic acids through electro-cocatalytic activation of peracetic acid: Synergistic effects of multiple factors

Herein, a peracetic acid (PAA)-based electro-cocatalytic system (EC/PAA/Fe(III)) has been established for efficient degradation of 1-adamantanecarboxylic acid (ACA), which is a typical model chemical for naphthenic acids (NAs) that are abundantly present in petroleum industrial wastewater. The electric field greatly boosted the regeneration of Fe(II) to activate PAA in the system, resulting in 99.8 % removal for ACA within 20-min reaction time, with kobs of 0.3451 min−1. Results of quenching and chemical probe experiments verified the production of •CH3, CH3C(O)O•, •OH and FeIVO2+, in the EC/PAA/Fe(III) system with the FeIVO2+ identified as the primary contributor to ACA removal. The H2O2 present in the PAA solution enhanced the activation of PAA by promoting Fe(II) generation, thereby significantly improving ACA degradation efficiency. The ACA degradation byproducts and pathways were identified using the results of high resolution mass spectrometry analysis and density functional theory (DFT) calculations. Decarboxylation, hydroxy substitution, and carbonyl substitution reactions were predominant oxidation pathways of ACA decontamination. The EC/PAA/Fe(III) system demonstrated resilient degradation performance under the influence of anions and the natural water matrix for effective degradation of the commercial NAs mixture. Overall, the EC/PAA/Fe(III) system has been established with effectiveness and reliability for future remediation of NAs in petroleum industrial wastewater.