Direct Reaction Research Articles

Asymmetric direct Aldol reaction between acetone and aromatic aldehydes catalyzed by diazadioxocalix[2]arene[2]triazine derivatives

Asymmetric direct Aldol reaction between acetone and aromatic aldehydes catalyzed by diazadioxocalix[2]arene[2]triazine derivatives

State-resolved quantum dynamics and reaction mechanisms of the Ne + HD+(v = 1) reaction

In the work, accurate converged theoretical simulations of the Ne + HD + ( v = 1 ) reaction are presented with the time-dependent wave packet (TDWP) method using the accurate potential energy surface by Lv (J. Chem. Phys. 2010, 132, 014303). In particular, the effect of intramolecular substitution and the translational collision energy on the reactive dynamics is investigated in detail to discern the reaction mechanisms. Total and state-to-state integral cross sections (ICSs) and differential cross sections (DCSs) of the two channels are derived and compared over a wide range of collision energies up to 1.2 eV. The analysis of the ICSs in terms of the total angular momentum contributions shows that the contribution of the J partial wave varies in the two reactive channels at different collision energies. The product state-resolved DCSs reveal that two opposite mechanisms co-exist in the two reactive channels with different ratios at low and high collision energies. Overall, NeH + + D channel appears to form the products via collision complex formation, which survives long enough leading to a forward–backward symmetric total DCS at low collision energies. In comparison, the NeD + + H proceeds through a direct stripping reaction, with predominantly forward scattering in the DCSs.

Direct Substitution of 2‐Aminotropones with Potassium Allyltrifluoroborates through Transition‐Metal‐Free C−N Bond Cleavage

AbstractThe poor nucleofugality of the amino group renders the C−N bond functionalization of primary aromatic amines highly challenging. Herein, we report a direct substitution reaction of 2‐aminotropones, bearing a unique non‐benzenoid seven‐membered aromatic ring that exists in some natural products and bioactive molecules, with potassium allyltrifluoroborates through C−N bond cleavage under transition‐metal‐free conditions. The amino group of 2‐aminotropones were directly substituted with potassium allyltrifluoroborates in the presence of sodium bicarbonate, delivering structurally diverse 2‐allyltropones in moderate to good yields. The reaction is free of directing groups, activating groups and transition metals, providing a convenient method to access substituted tropones.

Photocatalytic H2O2 production over boron-doped g-C3N4 containing coordinatively unsaturated FeOOH sites and CoOx clusters

Graphitic carbon nitride (g-C3N4) has gained increasing attention in artificial photosynthesis of H2O2, yet its performance is hindered by sluggish oxygen reduction reaction (ORR) kinetics and short excited-state electron lifetimes. Here we show a B-doped g-C3N4 (BCN) tailored with coordinatively unsaturated FeOOH and CoOx clusters for H2O2 photosynthesis from water and oxygen without sacrificial agents. The optimal material delivers a 30-fold activity enhancement compared with g-C3N4 under visible light, with a solar-to-chemical conversion efficiency of 0.75%, ranking among the forefront of reported g-C3N4-based photocatalysts. Additionally, an electron transfer efficiency reaches 34.1% for the oxygen reduction reaction as revealed by in situ microsecond transient absorption spectroscopy. Experimental and theoretical results reveal that CoOx initiates hole–water oxidation and prolongs the electron lifetime, whereas FeOOH accepts electrons and promotes oxygen activation. Intriguingly, the key to the direct one-step two-electron reaction pathway for H2O2 production lies in coordinatively unsaturated FeOOH to adjust the Pauling-type adsorption configuration of O2 to stabilize peroxide species and restrain the formation of superoxide radicals.

Effect of Beech Sawdust Conditions Modification on the Efficiency of the Sorption of Anionic and Cationic Dyes

The article presents studies on the effect of the modification method of beech sawdust on the sorption capacity of the anionic dye Reactive Black 5 (RB5) as well as the cationic dye Basic Violet 10 (BV10). In the studies, the pH value, the dose of sawdust activated with epichlorohydrin and the dose of ammonia were determined for the efficiency of the removal of anionic and cationic dyes. In the next phase of the study, the pH and the dose of epichlorohydrin activator on the previously activated sorbent were determined. The modification proposed in the work, which consists in the amination of sawdust in direct reaction with ammonia, increased the efficiency of the sorption of anionic dyes. This reaction increased the positive charge on the surface of the sorbent by introducing -NH2 groups, which led to an increase in the electrostatic attraction between the sorbent and the anionic dye, but to a decrease in the interaction between the sorbent and the cationic dye.

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.

Comprehensive Review on the Synthesis of [1,2,3]Triazolo[1,5-a]Quinolines.

This report outlines the evolution and recent progress about the different protocols to synthesize the N-heterocycles fused hybrids, specifically [1,2,3]triazolo[1,5-a]quinoline. This review encompasses a broad range of approaches, describing several reactions for obtaining this since, such as dehydrogenative cyclization, oxidative N-N coupling, Dieckmann condensation, intramolecular Heck, (3+2)-cycloaddition, Ullman-type coupling and direct intramolecular arylation reactions. We divided this review in three section based in the starting materials to synthesize the target [1,2,3]triazolo[1,5-a]quinolines. Starting materials containing quinoline or triazole units previously formed, as well as starting materials which both quinoline and triazole units are formed in situ. Different methods of obtaining are described, such as metal-free or catalyzed conditions, azide-free, using conventional heating or alternative energy sources, such as electrochemical and photochemical methods. Mechanistic insights underlying the reported reactions were also described in this comprehensive review.

Embedding Reverse Electron Transfer Between Stably Bare Cu Nanoparticles and Cation-Vacancy CuWO4.

Cu nanoparticles (NPs) have attracted widespread attention in electronics, energy, and catalysis. However, conventionally synthesized Cu NPs face some challenges such as surface passivation and agglomeration in applications, which impairs their functionalities in the physicochemical properties. Here, the issues above by engineering an embedded interface of stably bare Cu NPs on the cation-vacancy CuWO4 support is addressed, which induces the strong metal-support interactions and reverse electron transfer. Various atomic-scale analyses directly demonstrate the unique electronic structure of the embedded Cu NPs with negative charge and anion oxygen protective layer, which mitigates the typical degradation pathways such as oxidation in ambient air, high-temperature agglomeration, and CO poisoning adsorption. Kinetics and in situ spectroscopic studies unveil that the embedded electron-enriched Cu NPs follow the typical Eley-Rideal mechanism in CO oxidation, contrasting the Langmuir-Hinshelwood mechanism on the traditional Cu NPs. This mechanistic shift is driven by the Coulombic repulsion in anion oxygen layer, enabling its direct reaction with gaseous CO to form the easily desorbed monodentate carbonate.

Photoinduced Copper-Catalyzed Cross-Coupling of Acylsilanes with Heteroarenes via Bimetallic Relay.

The transition metal-catalyzed direct coupling reactions involving electron-rich Fischer carbene species are largely underdeveloped and remain a big challenge. Here, a direct coupling reaction of azoles and azine N-oxides is reported with Fischer copper carbene species bearing an α-siloxy group i, which can be in situ generated from acylsilanes catalytically under photoirradiation and redox-neutral conditions. This coupling reaction between electron-rich α-siloxy Fischer Cu-carbene species with hard carbanion nucleophiles may undergo a bimetallic relay process, which is confirmed by the kinetic analysis and in situ NMR analysis. This reaction features mild conditions and remarkable heterocycle compatibility. Notably, this protocol tolerates a series of azole or azine N-oxide derivatives, including benzoxazole, benzothiazole, benzoimidazole, benzoisoxazole, oxazole, oxadiazole, triazolo[4,3-a]pyridine, purine, caffeine, pyridine N-oxide, quinoline N-oxide, pyrazine N-oxide, pyridazine N-oxide, etc. The synthetic value of this approach is demonstrated by the efficient synthesis of a histamine h4 receptor ligand and a marketed drug carbinoxamine.

Ab Initio Neural Network Potential Energy Surface and Quantum Dynamics Calculations on Na(2S) + H2 → NaH + H Reaction.

The collisions between Na atoms and H2 molecules are of great significance in the field of chemical reaction dynamics, but the corresponding dynamics results of ground-state reactions have not been reported experimentally or theoretically. Herein, a global and high-precision potential energy surface (PES) of NaH2 (12A') is constructed by the neural network model based on 21,873 high-level ab initio points. On the newly constructed PES, the quantum dynamics calculations on the Na(2S) + H2(v0 = 0, j0 = 0) → NaH + H reaction are carried out using the time-dependent wave packet method to study the microscopic reaction mechanism at the state-to-state level. The calculated results show that the low-vibrational products are mainly formed by the dissociation of the triatomic complex; whereas, the direct reaction process dominates the generation of the products with high-vibrational states. The reaction generally follows the direct H-abstraction process, and there is also the short-lived complex-forming mechanism that occurs when the collision energy exceeds the reaction threshold slightly. The PES could be used to further study the stereodynamics effects of isotope substitution and rovibrational excitations on the title reaction, and the presented dynamics data would provide an important reference on the corresponding experimental research at a higher level.

Polypropylene Crystallinity Reduction through the Synergistic Effects of Cellulose and Silica Formed via Sol-Gel Synthesis.

This study focuses on the development of environmentally sustainable polypropylene (PP)-based composites with the potential for biodegradability by incorporating cellulose and the oligomeric siloxane ES-40. Targeting industrial applications such as fused deposition modeling (FDM) 3D printing, ES-40 was employed as a precursor for the in situ formation of silica particles via hydrolytic polycondensation (HPC). Two HPC approaches were investigated: a preliminary reaction in a mixture of cellulose, ethanol, and water, and a direct reaction within the molten PP matrix. The composites were thoroughly characterized using rotational rheometry, optical microscopy, differential scanning calorimetry, and dynamic mechanical analysis. Both methods resulted in composites with markedly reduced crystallinity and shrinkage compared to neat PP, with the lowest shrinkage observed in blends prepared directly in the extruder. The inclusion of cellulose not only enhances the environmental profile of these composites but also paves the way for the development of PP materials with improved biodegradability, highlighting the potential of this technique for fabricating more amorphous composites from crystalline or semi-crystalline polymers for enhancing the quality and dimensional stability of FDM-printed materials.

Designing 1-nm-Thick MOF Nanosheets with Donor-Acceptor Complexes for Photosynthesis of H2O2 Using Water and Dioxygen Only.

Artificial photosynthesis of hydrogen peroxide (H2O2) presents a promising environmentally friendly alternative to the industrial anthraquinone process. This work designed ultrathin metal-organic framework (MOF) nanosheets on which porphyrin ligand as an electron donor (D) and anthraquinone (AQ) as an electron acceptor (A) are integrated as the D-A complexes. The porphyrin component allows the MOF nanosheets to absorb full-spectrum solar light while the acceptor AQ motif promotes central aluminum ion coordination, hindering layer stacking to achieve a thickness of 1.0 nm. The ultrathin D-A design facilitates the separation of electrons from the MOF skeleton to the AQ motif, which induces the direct two-electron oxygen reduction reaction (ORR) mediated by the reversible redox couple of AQ-AQH2 and multielectron water oxidation reaction (WOR) driven by holes remaining on the porphyrin part. In O2-saturated water, the ultrathin MOF nanosheets outperformed the AQ-free bulk and multilayered counterparts by 2.9 and 2.6 times in H2O2 production, respectively, achieving the apparent quantum yield of 4.8% at 420 nm. It also surpasses other benchmark photocatalysts, including the typical MOF photocatalyst, MIL-125-NH2, and organic polymeric photocatalysts. The ultrathin D-A MOF photocatalyst generated H2O2 via both two-electron ORR as a major path and two-electron WOR as a minor path. This approach presents a promising strategy for the rational design of efficient nanostructured photocatalysts for solar fuels and chemicals.

A revision of the Ni-Zn phase diagram based on vapor-solid diffusion experiments

The technique of vapor-solid diffusion couples was systematically studied for its potential in phase diagram investigation using the well-established Ni-Zn system which is highly suitable for this purpose due to the high vapor pressure difference of the two constituents. More than 50 samples synthesized by direct vapor-solid reaction, varying the parameters temperature, time and overall system composition, were investigated by SEM/EDX focusing on diffusion profile line-scans. Supporting powder-XRD and DTA experiments were performed as well. Based on these experimental results, significant changes to the currently accepted Ni-Zn phase diagram, specifically concerning the β, β1, and γ phase fields, are proposed. Furthermore, a relatively simple experimental procedure to prepare vapor-solid diffusion experiments is introduced and its application in phase diagram investigation is discussed in detail.

Controlled Release of Diborane from Alkali Metal Borohydride using Ionic Liquid-Based Lewis Acids.

Alkali metal borohydrides present a rich source of energy dense materials of boron and hydrogen, however their potential in propellants has been hitherto untapped. Potassium borohydride is a promising fuel with high gravimetric energy density and relatively low sensitivity to air and moisture. Problems arise due to the dehydrogenation of the borohydride on heating with minimal energy release. Common methods to extract both boron and hydrogen by means of borane species involve direct reaction of boron trifluoride species with alkali borohydrides. However, these methods face storage and safety issues due to rapid release of diborane on mixing the reactants. We propose a method of diborane release through controlled release of boron trifluoride by means of a tetrafluoroborate based ionic liquid. The trifluoride is released from the ionic liquid at elevated temperatures and enables safe mixture of the reactants at room temperature. It was found that the reaction between borohydride and boron trifluoride proceeds well above room temperature with potassium borohydride releasing diborane and potassium fluoride. The reaction pathway shows a primary reaction releasing diborane and potassium fluoride and a second less energy efficient step leading to the formation of potassium tetrafluoroborate. A 3D printed propellant formulation was also tested.

Controlled Release of Diborane from Alkali Metal Borohydride using Ionic Liquid‐Based Lewis Acids

AbstractAlkali metal borohydrides present a rich source of energy dense materials of boron and hydrogen, however their potential in propellants has been hitherto untapped. Potassium borohydride is a promising fuel with high gravimetric energy density and relatively low sensitivity to air and moisture. Problems arise due to the dehydrogenation of the borohydride on heating with minimal energy release. Common methods to extract both boron and hydrogen by means of borane species involve direct reaction of boron trifluoride species with alkali borohydrides. However, these methods face storage and safety issues due to rapid release of diborane on mixing the reactants. We propose a method of diborane release through controlled release of boron trifluoride by means of a tetrafluoroborate based ionic liquid. The trifluoride is released from the ionic liquid at elevated temperatures and enables safe mixture of the reactants at room temperature. It was found that the reaction between borohydride and boron trifluoride proceeds well above room temperature with potassium borohydride releasing diborane and potassium fluoride. The reaction pathway shows a primary reaction releasing diborane and potassium fluoride and a second less energy efficient step leading to the formation of potassium tetrafluoroborate. A 3D printed propellant formulation was also tested.

A Novelly Hierarchical LDHs−Based Cathode with Reduced Deprotonation Barrier Toward High−Performance Alkaline Energy Storage

AbstractLayered double hydroxides (LDHs) are promising electrode materials for alkaline electrochemical energy storage (EES). However, their low capacity, sluggish rate performance, and limited cycle life significantly hinder practical applications. This study unlocks the direct deprotonation reaction pathway for LDH materials through theoretical calculations. Guided by this insight, a novelly hierarchical composite (LDH−TPA) with various dimensions and components is fabricated by introducing terephthalic acid (TPA), serving as a superior cathode material for alkaline EES devices. Experimental results and theoretical investigations reveal the transformation process for metal–organic framework quantum dots (MOF−QDs) and the enhanced mechanism of reaction kinetics in the LDH−TPA electrode. Benefiting from the reduced deprotonation barrier, optimized electronic structure, and fast electrons/ions transport rates, the LDH−TPA1 electrode demonstrates a high specific capacity of 267 mAh g−1 at 1 A g−1 and retains 167 mAh g−1 even at 20 A g−1, along with excellent cycling stability. Furthermore, an alkaline nickel−zinc battery (AZB) with LDH−TPA1 cathode is assembled, achieving a lifespan exceeding 3400 cycles, and a high energy density of 341.3 Wh kg−1 at a power density of 1640.9 W kg−1. This study is expected to provide new insight into the modification of LDHs and the advancement of alkaline energy systems.

Bimetallic MnZn-MOF-74 with enhanced percentage of MnIII: Efficiently catalytic activity for direct oxidative carboxylation of olefins to cyclic carbonates under mild and solvent-free condition

Multi-functional MOF catalyst with oxidative- and acid- centers showed potential in olefins oxidative carboxylation to cyclic carbonates directly. In this work, a series of bimetallic MnZn-MOF-74 with different molar ratios of Mn and Zn were synthesized successfully through a one-pot facile method. Thoroughly characterization indicated that the existence of Zn regulated the valance state distribution of Mn in the obtained MnZn-MOF-74. Mn99.3Zn0.7-MOF-74 with the highest ratio of MnIII (61.3 %) performed the most efficient activity for olefin direct tandem oxidative carboxylation reaction using aqueous tert-butyl hydroperoxide oxidant under solvent-free condition of 90 °C, 1.0 MPa CO2 and 4 h. Mn99.3Zn0.7-MOF-74 also showed satisfactory versatility and recyclability. Based on the experiments, a feasible mechanism was presented. Thanks to the high ratio of active MnIII as main oxidative center, the coordination unsaturated bimetal Mn and Zn as Lewis-acid sites, O2– of metal − O as Lewis-base sites and combined effect with Bu4NBr cocatalyst, Mn99.3Zn0.7-MOF-74 presented efficient performance for the direct synthesis of cyclic carbonates from olefins. The metal Zn in MOF can regulate the valance state distribution of Mn and result in efficient catalytic property, presenting a potential avenue for direct oxidative carboxylation reaction of olefins to cyclic carbonates synthesis.

Investigating the formation of soot in CH4 pyrolysis reactor: A numerical, experimental, and characterization study

Methane pyrolysis is a promising method for eco-friendly hydrogen production, but soot formation and carbon interaction pose challenges for scaling up. Therefore, understanding the dynamics of soot formation and carbon deposition is crucial. This study delves into the intricacies of soot formation in methane pyrolysis under industrially relevant conditions, namely operations at atmospheric pressure, employing a H2:CH4 ratio of 2 and exploring a range of hot zone temperatures (1473 K, 1573 K, 1673 K, and 1773 K) with a 5 s residence time. Utilizing a detailed gas-phase kinetic model with direct carbon deposition reactions, the research adopts the method of moments coupled with a one-dimensional plug flow reactor model to simulate soot formation. The model is validated by characterizing soot particles that were produced in a pyrolysis reactor by means of transmission electron microscopy, Dynamic light scattering (DLS), and Raman spectroscopy. Results show that lower temperatures lead to nucleation-dominated growth, whereas higher temperatures significantly restrain particle growth due to carbon deposition. DLS data indicate a complex balance between particle growth and deposition processes. These findings provide insights into operational parameters that can enhance reactor performance and sustainability in hydrogen production processes by mitigating soot and carbon deposition.

A “sizing-free” strategy to improve the interfacial property of PEEK/CF composites based on “grafting-bridging” bifunctional diazonium salt

Achieving simple and efficient interfacial modification between carbon fiber and polyether ether ketone (PEEK) has been the pursuit of researchers. In this study, by comparing the nucleophilicity of various aromatic amines, a direct Schiff base reaction with polyether ether ketone (PEEK) has been achieved. Based on this, a “grafting-bridging” bifunctional diazonium salt containing a phenylethylamine structure was designed and synthesized to enhance the interfacial strength through covalent bonding without the use of sizing agents. The diazonium salt was grafted onto the surface of carbon fiber through electrochemical reduction, while the PEEK resin and phenylethylamine could achieve bridging through heat treatment, thus a PEEK/CF interface with enhanced covalent bonds was constructed. The reaction and conversion rate between phenylethylamine and PEEK resin were confirmed through IR and NMR. The successful grafting of the diazonium salt on the carbon fiber was determined through XPS and cyclic voltammetry. The bridging reaction on the surface of carbon fiber was verified through XPS and the use of 6F-PEEK with characteristic elements. As a result, the interfacial shear strength (IFSS) of the modified PEEK/CF interface reached 86.2 MPa, representing a 102.8 % improvement compared to the untreated interface of 42.5 MPa, fully demonstrating the excellent effect of the bifunctional diazonium salt.

Indium‐Catalyzed Direct Amidation Reaction of Carboxylic Acids and In Silico Study for Screening the Activity of Potential Therapeutics of the Synthesized Products

AbstractAmide bonds are ubiquitous and valuable motifs in synthetic chemistry, found in a wide range of applications such as the backbone of proteins and pharmaceutical agents. Thus, environmentally friendly and selective methods for synthesizing amide bonds are important. Herein, we report a simple, efficient, and rapid route to access a range of functionalized amides from non‐activated carboxylic acids and amines using indium (III) trifluoromethanesulfonate as an efficient catalyst. A wide range of carboxylic acids – including aliphatic, aromatic, heterocyclic, and dicarbonyl acids – participate smoothly in these reactions, generating structurally diverse amides in moderate to good yields (up to 91 % in 24 examples). The reactions are conducted in dry tetrahydrofuran (THF) under reflux conditions. Furthermore, this amidation strategy provides a method for addressing challenging molecules, such as protected amino acids, to produce biocompatible products. These products can then be used as substrates for various organic transformations, including C−H functionalization reactions. We also demonstrate the synthetic utility of our protocol through the synthesis of essential substrates in organic and medicinal chemistry by reacting N‐protected carboxylic acids with 8‐aminoquinoline to produce a series of biologically valuable compounds. Five of these products, named 4 f, 4p, 9a, 9c, and 9d, have been biologically evaluated through an in‐silico study. The interaction of these compounds with receptor protein 8DQT was examined to assess their potential as drug candidates for hypertension treatment. Effective binding was detected between these compounds and the receptor. Data from molecular docking studies show that compounds 4d and 4 m are the most active, with binding scores of −8.8 and −8.6 kcal/mol, respectively. However, compound 4 m exhibited a stronger binding affinity than compound 4d over the course of dynamic simulation. Our ADMET study suggests that all five compounds are highly safe in the body. Based on the BOILED‐Egg model study, good absorption is suggested for all the molecules, and they can cross the blood‐brain barrier.