Reaction Solvent Research Articles

Coptis Root-Derived Hierarchical Carbon-Supported Ag Nanoparticles for Efficient and Recyclable Alkyne Halogenation

The advancement of green chemistry and sustainable chemical processes has been significantly facilitated by catalytic systems derived from plant roots, which also present substantial application prospects in the realm of chemical synthesis. This study utilized the roots of Rhizoma Coptidis as a support to successfully fabricate a silver-based nanocatalyst. By depositing silver nanoparticles onto the root material of Coptis chinensis and subjecting it to carbonization, a silver/carbon composite was synthesized, featuring monodisperse silver nanoparticles and a hierarchical mesoporous carbon framework. This composite exhibits robust surface activity, a well-defined pore structure, and superior mechanical properties. The catalyst achieves a catalytic yield nearing 90%, showcasing remarkable activity in terminal alkyne halogenation reactions. Its stability and recyclability are markedly enhanced; it retains 95% of its mass and remains unaltered in the reaction solvent for over 160 h after five cycles. This method simplifies the synthesis of terminal alkynes and their derivatives, rendering the process more environmentally benign and efficacious. Furthermore, it broadens the potential applications of Rhizoma Coptidis in synthetic chemistry and pioneers a novel approach for the synthesis of precious metal catalysts from renewable resources.

Catalytic Hydrogenation of CO2 by Direct Air Capture to Valuable C1 Products Using Homogenous Catalysts.

Growing atmospheric CO2 concentrations are a global concern and a primary factor contributing to global warming. Development of integrated CO2 capture and conversion protocols is necessary to mitigate this alarming challenge. Though CO2 hydrogenation to produce formic acid and methanol has seen many strides in the past decades, most studies utilize pure CO2 for this transformation. The CO2 concentration in the atmosphere stands at 400 ppm and reports that utilize direct air capture as the strategy to capture CO2 and utilize it for production of formic acid and methanol have only been reported in the past few years. This perspective summarizes such reports with a focus on the CO2-capturing additive, reaction solvent, and the molecular catalyst used to affect the transformation.

Solvent Effects in the Reactions of Alkenes with gem‐Bis(triflyl)ethylene

AbstractThe reaction modes in the reactions of several alkenes with Tf2C=CH2 (Tf=CF3SO2) have been controlled by the reaction solvents. For example, although the reaction with allylsilanes selectively produced normal allylation products in MeCN, gem‐bis(triflyl)cyclopentanes were formed in toluene. In particular, a selective formation of the (3+2) cycloadducts was achieved by using sterically hindered allylsilanes. We also found notable solvent effects in the reaction with simple alkenic hydrocarbons. That is, in hot toluene, the Alder ene reaction of the alkenes with Tf2C=CH2 smoothly proceeded to give the corresponding (E)‐alkenes bearing a superacidic bis(triflyl)methyl group.

Solvent-controlled catalytic divergent C–H alkylation of quinolones driven by unusual DMSO-promoted 1,3-heteroarene migration

We report on a catalytic divergent C–H alkylation of 4-quinolones with diazo compounds where the reaction pathways are controlled by a reaction solvent. Cp*Rh(III)-catalyzed site-selective C−H alkylation was carried out...

Synthesis of 4-hydroxyquinoline-2(1H)-ones Based on Ag(I)-catalyzed Carbon Dioxide Fixation on 2-alknylanilines

4-Hydroxyquinoline-2(1<i>H</i>)-ones exhibit multiple biological activities, and studying their synthetic methods is of great significance. In the presence of tetramethylguanidine and silver nitrate, 4-hydroxyquinoline-2(1<i>H</i>)-ones were efficiently synthesized from 2-ethynylanilines and carbon dioxide under atmospheric pressure. The reaction conditions, such as types of silver catalysts and reaction solvents, were optimized, and the applicability of the substrate was preliminarily investigated. This method provides an alternative pathway for the synthesis of 4-hydroxyquinoline-2(1<i>H</i>)-ones and the conversion and utilization of carbon dioxide.

Fabrication of regular UiO-66(Ce) nanocubes and their electrochemical catalysis performance

Metal-organic frameworks (MOFs), characterized with highly ordered porous structures and relatively high surface area, exhibit significant application potential in the field of electrochemistry catalysis. In this study, we successfully prepared UiO-66(Ce) particles with uniform nanocube morphology and the size distribution ranging from 90 to 156 nm. Both morphology and size can be precisely tuned by directly adjusting detailed synthesis parameters, including solvent concentration and reaction time. Moreover, the crystal growth mechanism of UiO-66(Ce) was comprehensively investigated through the microstructure characterization. Such uniform particles demonstrated a desirable electrocatalytic performance with hydrogen evolution reaction (HER) overpotential of 118.6 mV (at 10 mA cm−2) in alkaline electrolyte (1 M KOH). This study not only introduces a novel approach for the morphological manipulation of UiO-66(Ce), but also presents new material candidates for the advancement of high-performance electrochemical energy conversion systems.

Expedient, metal-, extraction- and generally purification-free, temperature- and solvent-directed oxidation of diaryl sulfides using t-BuOCl

An environmentally friendly, operationally simple and convenient, scalable, temperature- and solvent-directed oxidation of hydrophobic sulfides that yields sulfoxides and sulfones is presented. The conversion proceeds rapidly in a variety of green solvents, e.g., methanol, water, acetone, and acetic acid using tert-butyl hypochlorite (t-BuOCl), an easy-to-prepare and inexpensive oxidant with numerous applications in green chemistry and industry. Oxidation proceeds efficiently for challenging and purely soluble perfluoroalkyl, heterocyclic, or polyaryl systems with multiple strongly electron-withdrawing groups, e.g. nitro, acyl, and chloro, and selectively for electron-rich systems with benzylic and enolizable competing reaction sites or multiple sulfur atoms. Various industrially important products such as pesticides, anti-HIV agents, polymer monomers and additives can be generally isolated in pure form by simply removing the reaction solvent and benign volatiles. The mechanism was explored by NMR experiments and DFT calculations. Selective oxidation of polyphenylene sulfide allowed us to synthesize more durable polymer powders and to modify the surface of the film. The depth of the oxidized layer was tuned by duration of exposure to the oxidant. The developed clean, rapid, preparative, and scalable transformation of sulfides generally without required purification can likely be extended to other similar substrates and might be of interest for synthetic and sustainability-oriented chemical processes.

Determination of Puberulic Acid in Monascus-Fermented Red Yeast Rice by LC-MS/MS Combined with Precolumn Derivatization.

Puberulic acid (PA) is a mycotoxin produced by a species of Penicillium. It has received widespread attention as a significant contributor to the reported fatalities associated with red yeast rice dietary supplements. However, the detection of PA, especially at low concentration levels, poses a considerable challenge, with no detection methods reported thus far. Here, we present a simple and sensitive derivatization-based LC-MS/MS method, requiring no purification processes, for determination of PA in the red yeast rice. The methylating derivatization with trimethylsilyldiazomethane (TMSCHN2) was performed to enhance its analytical performance. To achieve optimal detection sensitivity, the amount of solvent and TMSCHN2 for the derivatization reaction, along with the reaction time, were individually optimized. Moreover, sample extraction solvent was carefully chosen to improve recoveries in real sample analyses. Comparatively, the proposed LC-MS/MS method achieved a superior detection sensitivity, over 100-fold higher than that of the liquid chromatography method. A good linear relationship within the concentration range of 5 ng/mL to 200 ng/mL (with a linear correlation coefficient of 0.99952) was demonstrated by the method validation. The average recovery rate was between 82.2% and 84.2%, and the repeatability (RSD of 2.1% to 10.4%, n = 6) was satisfactory. The derivatized PA remained stable within 48 h. The limit of detection and the limit of quantification could reach 2 μg/kg and 50 μg/kg, respectively. As a result, the method was successfully applied to detect PA in over 42 batches of the red yeast rice samples. It indicated a low risk of PA contaminations in the red yeast rice products made in China. Furthermore, its application to the other health food products containing red yeast rice demonstrated the applicability of the established method.

Acetic Acid and Ethyl Acetate as Solvents for Electropolymerization Reactions, Considering 4-Methoxyphenol and Composition of Solvent Mixtures

Various organic compounds susceptible to anodic polymerization were selected to study the effects of two solvents: acetic acid and ethyl acetate. Phenol and most of its derivatives, as well as resorcinol and 3,5-dihydroxybenzoic acid, exhibited typical electrode deactivation similar to other solvents; however, a continuous decrease in peak currents was not observed for 4-tert-butylphenols or salicylic aldehyde. Similar behavior was noted for monomers unrelated to phenols. In general, peaks were observed only for certain compounds and not in the initial voltammogram. Significant differences between the two solvents were observed in the subsequent voltammetric curves for some monomers. Microelectrode studies using 4-methoxyphenol as a model compound revealed notable differences between acetic acid and ethyl acetate in terms of curve shapes and the onset potentials of the plateaus. Plateau currents were used to estimate the solvent composition, demonstrating relatively high sensitivity to the acetic acid content.

CO2‐Promoted Reactions: A Prosperous Strategy for Conversion of Functional Group in Organic Synthesis

AbstractDue to its nontoxic nature, cost‐effectiveness, and natural abundance, carbon dioxide (CO2) is increasingly recognized as a valuable C1 source in organic synthesis. In addition to the building block for molecular construction, the role of CO2 as a promoter or catalyst to enhance reaction rates and selectivity is gaining attention. Acting as a reversible covalent Lewis acid, CO2 can function as an activating group in the transformation of various compounds, such as alcohols and amines, facilitating the dissociation of hydroxyl or activation of amino. It can also modulate the reactivity of nucleophilic reagents, including H2O, N‐heterocyclic carbenes (NHCs), cyanide (CN), and nucleophilic reductants like borohydride (BH4−). When CO2 interacts with these nucleophiles, it can exhibit Brønsted acidity or hydrogen‐bond donating capabilities and can also act as a coordinating ligand to transition metals in its carboxylate form (─CO2−). In this review, we mainly summarize and classify the synthetic applications and mechanistic insights of CO2‐promoted reactions according to different functional groups and bonding types, which include CO2‐promoted functional transformation of alcohols, CO2‐promoted functional transformation of amines; CO2‐promoted reactions in protic solvent; CO2‐promoted reactions via adducts of CO2 and nucleophiles, CO2‐promoted reductive reaction.

Kinetic and Mechanistic Study of the Oxidation of Some Para-substituted Benzhydrols by Cetyltrimethylammonium Bromochromate using Spectrophotometric Technique

Objectives: This study investigates the oxidation of para-substituted benzhydrols by cetyltrimethylammonium bromochromate (CTMABC) in dimethylsulfoxide (DMSO), aiming to elucidate the reaction kinetics and solvent effects. Methods: The oxidation was carried out under pseudo-first-order conditions, showing first-order kinetics for both CTMABC and benzhydrols. The role of hydrogen ions in catalysis was examined, and the reaction was analyzed in 19 different organic solvents. Solvent effects were quantified using Kamlet’s and Swain’s multi-parametric equations. Findings: The reaction produced the corresponding benzophenones and demonstrated a first-order dependence on both reactants. The presence of hydrogen ions accelerated the reaction. Solvent studies indicated that solute-solvent interactions significantly influenced reactivity. Novelty: This research provides a comprehensive kinetic and mechanistic understanding of benzhydrol oxidation, utilizing a novel multi-parametric approach to analyze solvent impacts, offering new insights into solute-solvent interactions in oxidation processes. Keywords: Kinetics, Mechanism, Cetyltrimethylammonium bromochromate, Benzhydrol, Solvent effect

Novel Heterogeneous Pd Catalysts for Cross‐Coupling Reactions in Biocompatible Media – Structural Insights from Solid‐State NMR Techniques

Novel SBA‐15 supported heterogeneous catalysts are synthesized and applied in the Mizoroki‐Heck and the Suzuki‐Miyaura cross coupling reactions in green solvents like PEG or water. The structural properties of the products after each synthesis step are monitored by different analytics. The amount of amine/carboxyl groups and vanillin/histidine methyl ester and thermal stability are determined by TGA and elemental analysis while ICP‐OES delivered the amount of palladium of the catalysts. The morphology is investigated by SEM and XPS and confirms the presence of coordinated palladium in the zero‐oxidation state. Gas adsorption analysis is conducted, which indicates the presence of palladium clusters in one of the two catalysts which is underlined by BSE images combined with EDX. A detailed 13C ssNMR and DNP enhanced 15N ssNMR spectral analysis is presented, which provides ultimate proof of the successful syntheses of the catalysts. The coordination of the palladium onto the carrier material is shown by combining the NMR spectral results with the results of the other analytics. First catalytic tests show for the Mizoroki‐Heck reaction yields up to nearly 100 % and for the Suzuki‐Miyaura up to 88 % in the presence of PEG and water, respectively.

Microwave-derivatized enhanced-spectrofluorophotometric characterization of nateglinide-loaded solid dispersion adsorbate and greenness profile assessment of method.

Nateglinide is an oral meglitinide that treats diabetes. Nateglinide was determined in several commercial formulations using chromatographic and spectrophotometric methods in published research. Quality-by-design approach was applied to develop the in-house nateglinide-loaded Solid Dispersion Adsorbate (SDA) for improving bioavailability and solubility. To determine nanogram-level nateglinide concentration forthe in-house developed nateglinide-SDA pharmacokinetics required time-consuming and expensive hyphenated analytical techniques such as LC-MS or UPLC-MS. Hence, asensitive spectrofluorophotometric method was developed to estimate nateglinide using NBD-Cl (7-chloro-4-nitrobenzoxadiazole) as the fluorophore. Microwave-aided chemical derivatization of nateglinide with NBD-Cl sped up sample analysis. Chemical reaction solvents were eco-friendly to safeguard aquatic life and environment. The chemical process was optimized by quality by design approach using screening design and response surface modelling. The fluorescence intensity of nateglinide was found to be linear over the concentration range of 20-250 ng/mL with a correlation coefficient of 0.9978. The limits of detection and quantification were found to be 10 and 20 ng/mL respectively. Precision and robustness investigations of the spectrofluorimetric method showed less than 2% relative standard deviations. Nateglinide-SDA drug-release study and pharmacokinetics were performed using the sensitive spectrofluorophotometric method. The in-house developed nateglinide-SDA released 95% of the drug in 30 min time duration. In-house-developed nateglinide-SDA has 1.5 times the oral bioavailability of commercial formulations due to in-vivo absorption. The published analytical methods were compared to the enhanced-spectrofluorophotometric method for user-friendliness, efficiency, cost-of-analysis, and environmental friendliness. The proposed sensitive-spectrofluorophotometric method was found to be robust, rapid, eco-friendly, cost-effective, and simple for the estimation of nateglinide.

Cooperative Iodine and Nitrate Catalyzed Oxidation of Stilbenes to α-Diketones in Water.

An efficient oxidation of stilbenes to α-diketones co-catalyzed by bismuth nitrate and iodine is reported. The utilization of molecular oxygen as a terminal oxidant and water as the reaction solvent provides a low-cost and environmentally friendly approach to preparing the α-diketone derivatives from readily available stilbenes. Isotope labeling experiments suggest that the two oxygen atoms of the α- diketone products mainly originate from water. The method displays high functional group tolerance and we have demonstrated a concise route for preparing trifenagrel and HIV-1 integrase inhibitors from 1,2-diphenylethene.

Fabrication of lignin-MOF derived spherical carbon supported NiCo-bimetallic catalysts for selective hydrogenolysis lignin derived ether.

The conversion of abundant lignin was of great significance for the utilization of biomass resources. In this study, lignin sulfonate (LS) was selected as a carbon-based support, which was successfully introduced into the NiCo-MOF structure. A series of lignin and MOF hybrid catalysts (NinCo-MOF-LS) with varying metal ratios of Ni and Co were synthesized via the hydrothermal method. Subsequently, the catalytic hydrogenolysis of lignin-derived dimers was conducted over a range of NinCo-MOF-LS, with the impact of calcination temperature and lignin addition in the catalysts taken into account. The selective conversion of benzyl phenyl ether (BPE) and other lignin dimers was achieved over the NinCo-MOF-LS catalyst with isopropanol serving as the hydrogen donor solvent in a nitrogen atmosphere. The Ni/Co metal ratio and calcination temperature were found to have a significant impact on the catalytic performance. Through a comprehensive investigation of various reaction parameters, including temperature, pressure, reaction time, and reaction solvent, it was determined that the catalyst exhibited excellent catalytic activity in the selective hydrogenolysis of BPE to cycloalkane and cyclohexanol. The optimal reaction conditions (240°C, 4h, 3MPaN2) were found to be conducive to the effective conversion of BPE into methylcyclohexane and cyclohexanol. The combination of lignin and metal-organic framework represented a novel approach to the utilization of lignin resources and the upgrading of biomass-derived chemicals.

Bimetallic nickel‑cobalt sulfide derived from lignin-MOFs hybrid as a high-efficiency heterogeneous catalyst for hydrogenolysis of lignin dimers.

Lignin represents a significant source of aromatic hydrocarbons in the natural world. The production of high-value chemicals from lignin has the great potential to effectively address the issue of fossil energy scarcity. In this study, complex sulfides of nickel‑cobalt bimetallic catalysts were prepared via hydrothermal synthesis and subsequently employed in the catalytic hydrogenolysis of CO bonds present in lignin. A series of complex sulfides Ni3S2/Co3S4-CSn-x-T derived from lignin-MOF (n = 0.5, 1, 1.5 and 2; x = 2, 4 and 6; T = 400, 500, 600 and 700 °C), were prepared under different conditions and subsequently employed in the catalytic hydrogenolysis of lignin model compounds. The optimal catalyst Ni3S2/Co3S4-CS1-4-500 exhibited the highest conversion rate of benzyl phenyl ether (BPE) (about 97.3 %), and the yields of toluene and phenol produced were 49.5 % and 43.6 %, respectively with isopropanol as the reaction solvent and no external H2. The introduction of element sulfur in catalysts could effectively inhibit the further hydrogenation of generated aromatic chemicals. The catalysts were well characterized, and the results demonstrated that the catalysts exhibited high catalytic activity with an increased loading of active components. This study provided some novel findings for the construction of biomass-based catalysts and the production lignin-derived aromatic chemicals.

One-Pot Synthesis and <i>In Vitro</i> Studies of Calix[4]-2-methylresorcinarene Derivatives as Antimalarial Agents Against <i>Plasmodium falciparum</i> Chloroquine-Resistant Strain FCR-3

Malaria is an endemic disease in Indonesia caused by infection from the Plasmodium parasite. Recently, antimalarial resistance significantly contributed to the decline in the cure rate of malaria sufferers. In this work, three calix[4]resorcinarenes have been synthesized from 2-methylresorcinol and different benzaldehyde derivatives, i.e., 4-chlorobenzaldehyde, 4-methoxybenzaldehyde, and 4-dimethylaminobenzaldehyde through the one-pot synthesis procedure. The calix[4]resorcinarenes synthesis was done through a cyclo-condensation reaction by using HCl 37% as the catalyst and ethanol as the solvent in an one-pot reaction. The structures of the synthesized products were confirmed using Fourier transform infrared, proton-nuclear magnetic resonance, and liquid chromatography-mass spectrometry techniques. The antimalarial activity assay was evaluated against the Plasmodium falciparum FCR-3 strain through an in vitro study. Three synthesized compounds, i.e., C-4-chlorophenylcalix[4]-2-methylresorcinarene, C-4-methoxyphenylcalix[4]-2-methylresorcinarene and C-4-dimethylaminophenylcalix[4]-2-methylresorcinarene have been successfully synthesized in up to 97% yield. The C-4-chlorophenylcalix[4]-2-methylresorcinerene exhibited the most potent antimalarial activity with a half-maximal inhibitory concentration (IC50) value of 2.66 µM against P. falciparum FCR-3 while the C-4-methoxyphenylcalix[4]-2-methylresorcinarene and C-4-dimethylaminophenylcalix[4]-2-methylresorcinarene gave the IC50 values of 23.63 and 13.82 µM, respectively. From the results, it could be concluded that the antimalarial activity of calix[4]-2-methylresorcinarenes was influenced by the type of substituent of aromatic rings at the para position.

Oxidative and non-oxidative photo-cyclization reaction of pyrazoles

A series of 5-(dimethoxyphenyl)-1,3-diphenylpyrazoles containing two methoxy groups on the different C5-aryl ring positions were synthesized and the electronic and steric effects, especially the position of the methoxy substitutions on the outcome of their photoreaction were investigated. Furthermore, the effect of the type and nature of solvent (chloroform or cyclohexane) in the progress of the photoreaction are also investigated. The photochemical results indicated the formation of two different phenanthridine products depending on the used solvent. Based on the proposed photo-induced electron-transfer mechanism in CHCl3 solution, the methoxy group on the ortho-position is eliminated during the photo-cyclization process and a chlorine atom is added to one of the allowed C5-aryl ring positions. While the observed photo-cyclization reaction in cyclohexane solvent occurs via complexation mechanism, which strongly requires the presence of the methoxy group on the ortho-position. In this case, complexation of the ortho-methoxy group to the N1-phenyl ring started the cyclization process, resulting in the formation of the phenanthridine photoproducts by elimination of this group. The phenanthridine products of both photoreactions are characterized by the analysis of their FT-IR, 1H NMR, 13C NMR, UV–Vis and Mass spectra. In addition, DFT computational studies were carried out to support the results of the experimental study.

Proline-Functionalized Magnetic Nanoparticles as Highly Performing Asymmetric Catalysts.

Amino acids have a crucial role in the field of asymmetric organocatalysis for the production of chiral compounds with high added value and specific biological activity. In particular, proline offers high activity and stereoselectivity for catalyzing aldol reactions in organic solvents. However, proline-based catalysts often lack water-solubility, accessibility, catalytic performance, or recovery in aqueous media. This work reports the design of proline-functionalized poly(methyl methacrylate) (PMMA) nanoparticles with a magnetic core that offer high availability of chiral units in water and high recyclability. A proline-based copolymerizable surfactant is designed and integrated onto the surface of PMMA nanoparticles through a miniemulsion polymerization process without using additional surfactants. The miniemulsion technique allows the incorporation of magnetite to the system to create a magnetically separable catalyst. The chiral nanocatalyst presents a high diastereoselective catalytic activity for the intermolecular aldol reaction between p-nitrobenzaldehyde and cyclohexanone in water.

Visible-Light-Induced Divergent Oxygenation of Methylbenzene Utilizing Aryl Halides.

The selective oxidation of methylbenzene to value-added products is of indisputable importance in organic synthesis. Although photocatalytic oxidation reactions of toluene have achieved great success for the preparation of its oxidative products, such as carboxylic acids, benzaldehyde, and benzoate, there remains a lack of a unified photocatalytic system for the selective preparation of these oxidation products. Herein, we report a metal- and additive-free photocatalytic protocol enabled by aryl halides using O2 as a green oxidant for the selective synthesis of the above-mentioned three oxidation products by adjusting the reaction solvent. This strategy features many advantages, including environmentally friendly and mild reaction conditions, broad substrate applicability and functional group tolerance, and potential practical application for the synthesis of aromatic carboxylic drugs and polymer materials and degradation of polystyrene waste. The continuous-flow system was utilized for the oxidation of toluene, which resulted in a reduced reaction time and increased production efficiency. Detailed mechanistic investigation revealed that the hydrogen atom transfer process was facilitated by the bromine radical from aryl halides for further oxidation, and an electron donor-acceptor complex of methylbenzene and aryl halides may exist.