Mild Synthesis Research Articles

Preparation of a novel Cu‐Ni mixed nanoparticles immobilized on clay: An Eco-friendly Nanocatalyst for mild synthesis of Benzimidazoles and pyrimidines

In the present work, Cu‐Ni mixed nanoparticles immobilized in magnetic clay (MMT-BAC@Fe3O4@CuNi) nanocatalyst were successfully synthesized using a simple method for the first time. In the design of this catalyst, nickel and copper ions were reduced and deposited on clay layers using a benzalkonium chloride directing group. The proposed method offers a safe, sustainable, and selective approach for the synthesis of 2-substituted benzimidazole and 3,4-dihydropyrimidin-2(1H)-ones using an environmentally friendly nanocatalyst. The solid catalyst was distinguished using a diversity of methods, including EDX (Energy Dispersive X-Ray), XRD (X-ray Diffraction), ICP (Inductively Coupled Plasma), VSM (Vibrating Sample Magnetometer), FT-IR (Fourier Transform Infrared Spectroscopy), TEM (Transmission Electron Microscopy) and FE-SEM (Field Emission Scanning Electron Microscopy). The significant features of this new protocol include good to excellent efficiency, oxidant-free conditions, low catalyst loading, inexpensive and non-toxic catalyst, simple procedure, moderate conditions, straightforward work-up, short reaction times, and easy reuse of the nanocatalyst.

Mild and practical synthesis of 5-thio-d-glucopyranose and its pentaacetate derivatives

Two synthetic approaches for 5-thio-d-glucopyranose (5-TDGP) and its pentaacetates were described, focusing on different protective groups such as tert-butyldimethylsilyl and benzoyl employed to protect 3-OH. These protective groups were easily introduced from the beginning and can be removed during transformation from the corresponding mesylate of α-d-glucofuranose to 5,6-episulfide under mild conditions. In addition, a few purification manipulations were required for each approach. More importantly, 5-TDGP can be prepared using the two approaches starting from 200 g of starting material in 66.08 % and 64.4 % overall yields, respectively.

Highly effective red phosphor for warm white LEDs without rare earth elements

The use of red fluorescent powder derived from nitrides and oxides in warm white LEDs is a pressing concern due to its lower quantum efficiency. Fluoride red phosphors activated by Mn4+ ions show promising potential for application in white light-emitting diodes (LEDs) due to their distinctive narrowband red emission and broad blue excitation, along with the relatively mild synthesis conditions required. However, the quantum efficiency of early Mn4+-doped fluoride phosphors was not optimal, highlighting the importance of identifying a suitable preparation method and matrix. Here, we introduce an efficient and thermally stable red fluoride phosphor, Cs2SiF6:Mn4+, which demonstrates a remarkable quantum efficiency of 98.32 % achieved through ion exchange techniques. However, even at a temperature of 423 K, the luminous intensity still maintained at 95 % of that under room temperature conditions. By incorporating Cs2SiF6:Mn4+ as a red emitter, a stable 10 W high-power warm white LEDs with a luminous efficiency of approximately 126.1 lm/W can be realized. These findings underscore the significant potential of the red phosphor Cs2SiF6:Mn4+ in advancing high-performance, high-power warm white LEDs.

Palladium-Catalyzed Synthesis of Nitrones Via Redox Cross-Coupling of Nitro Compounds and Alcohols.

A novel methodology for the synthesis of nitrones via palladium-catalyzed redox cross-coupling of nitro compounds and alcohols is established. The protocol is a mild, convenient, ligand-free, and scalable synthesis method that can be compatible with various nitro compounds and alcohols. Nitrone is a significant multifunctional platform synthon which can be synthesized directly and efficiently via this tactic from commercially available and cheap raw materials.

Mild and stereoselective synthesis of (1E,3E)-dienes through silver(I)-catalyzed β-hydride migration from allylic α-diazo esters

Mild and stereoselective synthesis of (1E,3E)-dienes through silver(I)-catalyzed β-hydride migration from allylic α-diazo esters

Pd-Catalyzed Aerobic Synthesis of Allylic Sulfones from Allylic Alcohols and Sulfonyl Hydrazines in Water.

A mild and green synthesis of allylic sulfones from allylic alcohols and sulfonyl hydrazines was developed in water media. The simple and commercially available Pd(PPh3)4 is used as the best catalyst, and the reaction can proceed smoothly at 40 °C under air. This new method does not require the common nitrogen protection and organic media, and can be readily scaled up in gram scale, showing the good practicality value.

Accessible New Non-Quantum Dot Cs2PbI2Cl2-Based Photocatalysts for Efficient Hole-Driven Photocatalytic Applications.

Efficient, low-cost photocatalysts with mild synthesis conditions and stable photocatalytic behavior have always been the focus in the field of photocatalysis. This study proves that non-quantum-dot Cs2PbI2Cl2-based materials, created by a simple method, can be successfully employed as new high-efficient photocatalysts. The results demonstrate that two-dimensional Cs2PbI2Cl2 perovskite can achieve over three times higher photocatalytic performance compared to three-dimensional CsPbBr3 perovskite. Moreover, the photocatalytic performance of Cs2PbI2Cl2 can be further improved by constructing a heterojunction structure, such as Cs2PbI2Cl2/CsPbBr3. Cs2PbI2Cl2 can connect well with CsPbBr3 through a simple method, resulting in tight bonding at the interface and efficient carrier transfer. Cs2PbI2Cl2/CsPbBr3 exhibits notable 5-fold and 10-fold improvements in photocatalytic performance and rate compared to CsPbBr3. Additionally, Cs2PbI2Cl2/CsPbBr3 demonstrates superb stable catalytic performance, with nearly no decrease in photocatalytic performance after 7 months (RH = 20% ± 10, T = 25 °C ± 5). This study also reveals that the photocatalytic process based on Cs2PbI2Cl2/CsPbBr3 can directly oxidize organic matter using holes, without relying on the generation of intermediate reactive oxygen species from water or oxygen (such as ·OH or ·O2-), showcasing further potential for achieving high photocatalytic efficiency and selectivity in anhydrous/anaerobic catalytic reactions and treating recalcitrant pollutants.

Visible-Light-Driven Multicomponent Reactions for the Versatile Synthesis of Thioamides by Radical Thiocarbamoylation.

Thioamides are widely used structures in pharmaceuticals and agrochemicals, as well as important synthons for the construction of sulfur-containing heterocycles. This report presents a series of visible-light-driven multicomponent reactions of amines, carbon disulfide, and olefins for the mild and versatile synthesis of linear thioamides and cyclic thiolactams. The use of inexpensive and readily available carbon disulfide as the thiocarbonyl source in a radical pathway enables the facile assembly of structurally diverse amine moieties with non-nucleophilic carbon-based reaction partners. Radical thiocarbamoylative cyclization provides a practical protocol that complements traditional approaches to thiolactams relying on deoxythionation. Mechanistic studies reveal that direct photoexcitation of in situ formed dithiocarbamate anions as well as versatile photoinduced electron transfer with diverse electron acceptors are key to the reactions.

Visible‐Light‐Driven Multicomponent Reactions for the Versatile Synthesis of Thioamides by Radical Thiocarbamoylation

Thioamides are widely used structures in pharmaceuticals and agrochemicals, as well as important synthons for the construction of sulfur‐containing heterocycles. This report presents a series of visible‐light‐driven multicomponent reactions of amines, carbon disulfide, and olefins for the mild and versatile synthesis of linear thioamides and cyclic thiolactams. The use of inexpensive and readily available carbon disulfide as the thiocarbonyl source in a radical pathway enables the facile assembly of structurally diverse amine moieties with non‐nucleophilic carbon‐based reaction partners. Radical thiocarbamoylative cyclization provides a practical protocol that complements traditional approaches to thiolactams relying on deoxythionation. Mechanistic studies reveal that direct photoexcitation of in situ formed dithiocarbamate anions as well as versatile photoinduced electron transfer with diverse electron acceptors are key to the reactions.

SOFT MECHANOCHEMICAL SYNTHESIS OF ZINC, MANGANESE AND NICKEL DIPHOSPHATES

Currently, condensed phosphates are used in many growths, while crystalline phosphate polymers were previously obtained by thermolysis, which is economically and environmentally unprofitable. In this regard, obtaining the required product at relatively low temperatures by mild mechanochemical synthesis (MMhC) is one of the urgent tasks. The purpose of this work is to establish conditions for the soft mechanochemical synthesis of zinc, manganese and nickel diphosphates. To achieve the goal of the work, a new mechanothermal method for the production of diphosphates of a number of d-elements (Zn, Mn, Ni) was developed, consisting of two stages of synthesis: 1) in the mechanochemical process of diphosphate; 2) in the heat treatment of the intermediate product. The mechanochemical synthesis was carried out in grinding machines, at a modern RETSCH brand planetary mill. Also, various complexes of physico-chemical research methods were used to study the properties and composition of the obtained materials. Results and discussions. With mechanochemical activation of the studied mixtures, intermediate compounds - NH4M(II)PO4 can be obtained, and thermolysis at low temperatures – target products - individual diphosphates Zn, Mn, Ni (400°C, 300°C, 500°C.) It has been established that this method is environmentally friendly and low energy costs. Conclusion. Conditions for the soft mechanochemical synthesis of zinc, manganese and nickel diphosphates were established.

Construction and Function of Thiolate-Bridged Diiron NxHy Nitrogenase Model Complexes.

ConspectusBiological nitrogen fixation mediated by nitrogenases has garnered significant research interest due to its critical importance to the development of efficient catalysts for mild ammonia synthesis. Although the active center of the most studied FeMo-nitrogenases has been determined to be a complicated [Fe7S9MoC] hetero-multinuclear metal-sulfur cluster known as the FeMo-cofactor, the exact binding site and reduction pathway of N2 remain a subject of debate. Over the past decades, the majority of studies have focused on mononuclear molybdenum or iron centers as potential reaction sites. In stark contrast, cooperative activation of N2 through bi- or multimetallic centers has been largely overlooked and underexplored, despite the renewed interest sparked by recent biochemical and computational studies. Consequently, constructing bioinspired bi- or multinuclear metallic model complexes presents an intriguing yet challenging prospect. In this Account, we detail our long-standing research on the design and synthesis of novel thiolate-bridged diiron complexes as nitrogenase models and their application to chemical simulations of potential biological N2 reduction pathways.Inspired by the structural and electronic features of the potential diiron active center in the belt region of the FeMo-cofactor, we have designed and synthesized a series of new thiolate-bridged diiron nitrogenase model complexes, wherein iron centers with +2 or +3 oxidation states are coordinated by Cp* as carbon-based donors and thiolate ligands as sulfur donors. Through the synergistic interaction between the two iron centers, unstable diazene (NH═NH) species can be trapped to generate the first example of a [Fe2S2]-type complex bearing a cis-μ-η1:η1-NH═NH subunit. Significantly, this species can not only catalyze the reductive N-N bond cleavage of hydrazine to ammonia but also trigger a stepwise reduction sequence NH═NH → [NH2-NH]- → [NH]2-(+NH3) → [NH2]- → NH3. Furthermore, an unprecedented thiolate-bridged diiron μ-nitride featuring a bent Fe-N-Fe moiety was successfully isolated and structurally characterized. Importantly, this diiron μ-nitride can undergo successive proton-coupled electron transfer processes to efficiently release ammonia in the presence of separate protons and electrons and can even be directly hydrogenated using H2 as a combination of protons and electrons for high-yield ammonia formation. Based on combined experimental and computational studies, we proposed two distinct reductive transformation sequences on the diiron centers, which involve a series of crucial NxHy intermediates. Moreover, we also achieved catalytic N2 reduction to silylamines with [Fe2S2]-type complexes by ligand modulation.Our bioinspired diiron cooperative scaffold may provide a suitable model for probing the potential N2 stepwise reduction pathways from the molecular level. Different from the traditional alternating and distal pathways dominated by mononuclear iron or molybdenum complexes, our proposed alternating transformation route based on the diiron centers may not involve the N2H4 intermediate, and the convergence point of the alternating and terminal pathways is imide, not amide. Our research strategy could inform the design and development of new types of bioinspired catalysts for mild and efficient nitrogen reduction in the future.

Mild and selective synthesis of imines and N-Heterocyclic compounds via formic acid-mediated reductive coupling strategy over Nitrogen-Coordinated cobalt Single-Atom catalysts

The selective formation of C = N bonds through the formic acid-mediated reductive coupling of nitro groups with carbonyl groups over heterogeneous catalysts poses challenges due to the corrosion of metal catalysts by formic acid and the rapid further hydrogenation of C = N into C-N bonds. In this study, we demonstrate that nitrogen-coordinated cobalt single-atom catalysts exhibit robust activity in this transformation. Various imines and N-heterocyclic compounds, including benzimidazoles, quinazolines, and pyrroles, can be synthesized at a modest temperature of only 70 °C. The high catalytic activity is attributed to the synergistic roles of nitrogen and cobalt atoms, serving as basic and active sites, respectively. Experimental data, complemented by density functional theory (DFT) calculations, clearly indicate that the transfer hydrogenation of nitrobenzene preferentially proceeds via the “direct” pathway rather than the “condensation” pathway. Moreover, the reduction of C = N bonds into C-N bonds demands much higher energy than the reduction of nitro groups, thereby enabling high selectivity towards C = N bonds. The findings of this study are expected to provide a novel approach for selective C = N bond formation and contribute to a deeper understanding of the mechanism underlying the reductive amination process.

Preparation of Polydopamine Functionalized HNIW Crystals and Application in Solid Propellants.

The application of hexanitrohexaazaisowurtzitane (HNIW) as an oxidizer in solid propellants aligns with the pursuit of high-energy materials. However, the phase transformation behavior and high impact sensitivity of HNIW are its limitations. Due to the strong adhesion and mild synthesis conditions, polydopamine (PDA) has been employed to modify HNIW. However, the method suffers from a slow coating process and a non-ideal coating effect under short reaction time. Herein, oxygen-accelerated dopamine in situ polymerization coating method was developed. It was found that oxygen not only reduced the coating time but also contributed to forming a dense and uniform PDA layer. HNIW@PDA coated in oxygen for 6 h exhibited the most favorable performance, with a delay of 20.8 °C in the phase transition temperature and a reduction of 145.45% in the impact sensitivity. The -OH groups on the surface of PDA enhanced the interaction between HNIW and polymer binders, resulting in a 20.36% reduction in the dewetting percentage. The lower content of PDA in HNIW@PDA (1.17%) resulted in minimal variation in the heat of explosion for HNIW@PDA-based HTPB propellant (6287 kJ/kg) in comparison to HNIW-based HTPB propellant (6297 kJ/kg). Hence, HNIW@PDA-based propellants are expected to offer an alternative with promising safety and mechanical performance compared to existing HNIW-based propellants, thus facilitating the application of HNIW in high-energy propellants. This work presents a low-cost method for efficiently inhibiting the phase transformation of polycrystalline explosives and reducing the impact sensitivity. It also offers a potential approach to enhance the interfacial interaction between nitro-containing explosives and polymer binders.

Regioselective N1‐methylation of 1H‐tetrazoles with methyl 2,2,2‐trichloroacetimidate

AbstractAn efficient, mild, and regioselective synthesis of substituted 1‐methyl‐1H‐tetrazole using methyl 2,2,2‐trichloroacetimidate is described. The substrate scope of the methodology has been established with wide variety of tetrazoles. N1‐Methylated tetrazoles were synthesized with high yields (85%–97%).

Surface state modulation of carbon dots for efficient generation of hydrogen peroxide

Electrocatalytic dual electron oxygen reduction to hydrogen peroxide (2e ORR) is considered a special and sustainable method for on-site continuous production of hydrogen peroxide. Oxygen doped carbon based materials have demonstrated their superiority in the generation of H2O2. However, there is still a lack of direct experimental evidence to determine the true active site on complex carbon surfaces. In this work, we introduce only carboxyl functional groups on the surface of carbon dots by a mild and simple synthesis method to study the specific COOH functional groups on the generation of H2O2. The H2O2 selectivity was correlated with the contents of COOH functional groups. In alkaline environments, the citric acid modified CDs (CA-OCDs) own excellent catalytic ability for 2e ORR, showing a maximum starting potential of 0.829 V (vs. RHE) and a high selectivity of 89.7 % over a wide potential range of 0.2–0.7 V (vs. RHE). In actual H2O2 production, the Faraday efficiency (FE) of CA-OCDs can be up to 97 %, and the yield achieves 838 mmol gcatalyst−1 h−1. This work provides an effective and simple strategy for designing efficient carbon-based catalysts for sustainable H2O2 electrosynthesis.

Microwave-assisted solvothermal synthesis of Eu3+-doped CsY2F7 and RbY2F7 phosphorescent nanoparticles

We synthesized Eu3+-doped CsY2F7 and RbY2F7 nanoparticles (orthorhombic crystal structure, Pnna space group, No. 52) by the microwave-assisted solvothermal technique and investigated the influence of reaction temperature and fluoride ion concentration on the particles’ phase and crystal structure. Fluoride ions were added in excess of the stoichiometric amount to achieve the orthorhombic phase for CsY2F7 and to convert the cubic RbY3F10 to the orthorhombic RbY2F7. Mild synthesis conditions yielded nanoparticles with crystallites ranging in size from 19 to 37 nm and a combination of spherical, rod-like, and hexagonal shapes. Nanoparticles emit a strong orange and red light when excited into the Eu3+5L6 level, which is centered around 390 nm. The strongest emission peak is around 612 nm, which comes from the 5D0→7F2 electronic transitions. Emission intensity dependence on Eu3+ concentration revealed that nanoparticles can be heavily doped with Eu3+, up to 25 % with respect to Y3+. Emission decay measurements provided values of excited state lifetimes of 6.2 ms for the Cs(Y0.75Eu0.25)2F7 and 6.0 ms for the Rb(Y0.75Eu0.25)2F7.

Tf2O-Mediated mild synthesis of 6H-chromeno[4,3-b]quinolines

Tf2O-Mediated mild synthesis of 6H-chromeno[4,3-b]quinolines

Practical operating flexibility of a bifunctional freestanding membrane for efficient anion exchange membrane water electrolysis across all current ranges

AbstractThis study explores a symmetric configuration approach in anion exchange membrane (AEM) water electrolysis, focusing on overcoming adaptability challenges in dynamic conditions. Here, a rapid and mild synthesis technique for fabricating fibrous membrane‐type catalyst electrodes is developed. Our method leverages the contrasting oxidation states between the sulfur‐doped NiFe(OH)2 shell and the metallic Ni core, as revealed by electron energy loss spectroscopy. Theoretical evaluations confirm that the S–NiFe(OH)2 active sites optimize free energy for alkaline water electrolysis intermediates. This technique bypasses traditional energy‐intensive processes, achieving superior bifunctional activity beyond current benchmarks. The symmetric AEM water electrolyzer demonstrates a current density of 2 A cm−2 at 1.78 V at 60°C in 1 M KOH electrolyte and also sustains ampere‐scale water electrolysis below 2.0 V for 140 h even in ambient conditions. These results highlight the system's operational flexibility and structural stability, marking a significant advancement in AEM water electrolysis technology.

Mild synthesis of 2,3,5,6-tetrafluoropyridine ethers and their reactivity toward imidazole and pyrazole

A series of six, 4-substituted 2,3,5,6-tetrafluoropyridine (TFP) hetero ethers have been synthesized via regio-selective, nucleophilic aromatic substitution (SNAr) of pentafluoropyridine with aliphatic alcohols and phenols. Furthermore, the hexyloxy modified TFP substrate also served as a synthetic intermediate for the preparation of 3,5-difluoro-4-(hexyloxy)-2,6-di(1H-imidazol-1-yl)pyridine, as well as 4-(hexyloxy)-2,3,5,6-tetra(1H-pyrazol-1-yl)pyridine, which offers a terpyridine scaffold. This work outlines their synthetic methodology in addition to detailing the TFP intermediates’ unexpected reactivity with imidazole and pyrazole nucleophiles

One-step synthesis of δ-MnO2 with rich defects for efficient ozone decomposition under humid conditions

The catalytic performance of manganese oxides (MnOx) for ozone (O3) decomposition is affected by moisture and stability, for which MnOx with abundant defects offers a promising solution. In this study, a simple and mild one-step synthesis route was developed for highly defective δ-MnO2 preparation. The optimal catalyst was operated at 35 % relative humidity (RH) for 12 h, and the O3 conversion maintained over 99 %. Characterizations revealed that the K+ insertion into the interlayers preserved a highly defective layered structure. Rich surface defects and grain boundaries facilitated the generation of oxygen vacancies and the migration of oxygen species, stabilizing the elimination of O3. In addition, a combination of characterization and experiments determined that physisorbed water is critical for inhibiting activity, and thus, weak physisorption of water on the catalyst represents excellent water resistance. This work aims to provide guidance and new insights into the design of stable and water-resistant MnOx catalysts.