Search Results (620)

The semi-synthesis of the (5R,7R,11bR)-9-(di(1H-indol-3-yl)methyl)-4,4,7,11b-tetramethyl-1,2,3,4,4a,5,6,6a,7,11,11a,11b-dodecahydrophenanthro[3,2-b]furan-5-yl acetate was performed via a pseudo-multicomponent reaction involving a double Friedel–Crafts alkylation between the natural product-derived aldehyde 6β-acetoxyvouacapane and the corresponding indole. The transformation was carried out under solvent-free mechanochemical conditions using mortar and pestle grinding, with ZnCl₂ as the catalyst. Structural elucidation of the target compound was accomplished using 1D and 2D NMR spectroscopy (¹H, ¹³C, COSY, HSQC, and HMBC), FT-IR, and high-resolution mass spectrometry (HRMS). Full article

Multicomponent reactions (MCRs) enable the efficient assembly of complex small molecules via multiple bond-forming events in a single step. However, individual MCRs typically yield products with similar core structures, limiting access to larger, more intricate scaffolds. Strategic selection of reactants allows the combination of distinct MCRs, thus facilitating the synthesis of advanced molecular architectures with potential biological significance. Using our previously reported method for performing the aza-Friedel Crafts multicomponent reaction under green heterogeneous conditions, we have incorporated some of the obtained products into diverse multicomponent reactions to generate, in an unprecedent approach, eight novel products, some of which were also characterized by two-dimensional NMR techniques. The biological properties of such products are under investigation. Full article

Composite solid propellants, which serve as the core energetic materials in aerospace and military propulsion systems, necessitate tailored enhancement of their mechanical properties to ensure operational safety and stability. A critical challenge involves elucidating the interfacial interactions among the multiple propellant components (≥6 components, including the polymer binder HTPB, curing agent IPDI, oxidizer particles AP/Al, bonding agents MAPO/T313, plasticizer DOS, etc.) and their influence on crosslinked network formation. In this study, we propose an integrated computational framework that combines coarse-grained simulations with reactive force fields to investigate these complex interactions at the molecular level. Our approach successfully elucidates the two-step reaction mechanism propagating along the AP interface in multicomponent propellants, comprising interfacial self-polymerization of bonding agents followed by the participation of curing agents in crosslinked network formation. Furthermore, we assess the mechanical performance through tensile simulations, systematically investigating both defect formation near the interface and the influence of key parameters, including the self-polymerization time, HTPB chain length, and IPDI content. Our results indicate that the rational selection of parameters enables the optimization of mechanical properties (e.g., ~20% synchronous improvement in tensile modulus and strength, achieved by selecting a side-chain ratio of 20%, a DOS molar ratio of 2.5%, a MAPO:T313 ratio of 1:2, a self-polymerization MAPO time of 260 ns, etc.). Overall, this study provides molecular-level insights into the structure–property relationships of composite propellants and offers a valuable computational framework for guided formulation optimization in propellant manufacturing. Full article

Isocyanides insertions represent an important transformation in the palladium-catalyzed reactions landscape. However, one of their most significant limitations is in the use of inactivated alkyl electrophiles. Palladium photocatalysis has been proven as a solid tool for the generation of alkyl radicals from alkyl halides, which may engage in subsequent transformations with a variety of reaction partners, closing the catalytic cycle. Herein, we report the mild three-component isocyanide insertions into inactivated alkyl iodides mediated by the catalytic activity of a photoexcited palladium complex. We investigated the scope of the reaction obtaining differently substituted secondary amides in good to high yields. We also investigated the mechanism, hypothesizing a key role of 4-(N,N-dimethylamino)pyridine in the outcome of the reaction. Full article

Deep eutectic solvents (DESs) have emerged as prominent, environmentally benign substitutes for traditional solvents and catalysts in organic synthesis, notably in the synthesis of amines, pivotal structures in many industrial sectors. Their distinctive physicochemical attributes—including negligible volatility, exceptional thermal stability, and adjustable polarity—render them particularly advantageous for facilitating a broad spectrum of amination reactions. DESs can serve dually as reaction media and as intrinsic catalytic systems, accelerating reaction kinetics without necessitating supplementary catalysts or severe reaction conditions. They are especially efficacious in processes such as reductive amination, transamination, and multicomponent transformations, often affording superior yields and streamlining product isolation. The extensive hydrogen-bonding network intrinsic to DESs is believed to mediate crucial mechanistic steps, frequently obviating the requirement for external additives. Moreover, DESs are recyclable and exhibit compatibility with a diverse array of substrates, encompassing bio-derived and pharmaceutical intermediates. Full article

In this study, novel fluorescent 5-aryl-2-styryl-3H-indole derivatives were efficiently synthesized from 4-bromophenylhydrazine hydrochloride using the microwave-accelerated one-pot technique, which includes Fischer synthesis, Suzuki cross-coupling, and Knoevenagel condensation. The structural assignments of the synthesized compounds were based on ¹H, ¹³C, ¹⁵N, and ¹⁹F NMR; IR spectroscopy; and HRMS spectral data. The optical properties of the newly obtained styryl-indole dyes were studied using UV-vis and fluorescence spectroscopy, which clearly demonstrated that the derivatives substituted with electron-donating or -withdrawing groups exhibited varying emission shifts and quantum yields ranging from negligible to high. Full article

As a key pest damaging urban greenery in Yunnan, China, Achelura yunnanensis larvae secrete venom for defense, yet the molecular basis of this process remains poorly understood. This study aimed to uncover the molecular mechanisms of venom secretion by comparing the dorsal epidermis tissue (LDET) with the larval proleg tissue (LP). We performed transcriptomic analysis using RNA sequencing to identify differentially expressed genes between LDET and LP (10 biological replicates per tissue type), followed by functional enrichment and gene expression correlation analyses to explore tissue-specific characteristics. LDET exhibited significant upregulation of pathways related to lipid metabolism, redox reactions, and surface protective structure formation, suggesting their roles in venom stabilization, activation, and safe secretion. Conversely, genes linked to non-venom-related functions, such as extracellular matrix organization and epidermal development, were downregulated in LDET, indicating resource reallocation toward venom production. These findings reveal a multi-component mechanism in LDET that supports venom secretion through metabolic and structural adaptations, with lipid metabolism genes constituting 18.3% of total differentially expressed genes, highlighting evolutionary trade-offs in insect defense. This study provides new insights into insect venom secretion and offers potential targets for pest control strategies. Full article

During the operation of a solid rocket motor, the nozzle, which is a key component, is subjected to extreme conditions, including high temperatures, high-speed gas flow, and discrete-phase particles. For composite nozzles incorporating a carbon/carbon (C/C) throat liner and a carbon/phenolic expansion section, thermochemical ablation and the formation of ablation steps during the ablation process significantly hinder nozzle performance and engine operational stability. In this study, the fluid and solid domains and the physicochemical interactions between them during nozzle operation were analyzed. An innovative thermochemical ablation model for composite nozzles was developed to account for wall recession. The coupled model covered multi-component gas flow, heterogeneous chemical reactions on the nozzle surface, structural heat transfer, variations in material parameters induced by carbon/phenolic pyrolysis, and the dynamic recession process of the nozzle profile due to ablation. The model achieved coupling between gas flow, heterogeneous reactions, and structural heat transfer through interfacial mass and energy balance relationships. Based on this model, the distribution of the nozzle’s thermochemical ablation rate was analyzed to investigate the mechanisms underlying ablation step formation. Furthermore, detailed calculations and analyses were performed to determine the effects of the gas pressure, temperature, H₂O concentration, and aluminum concentration in the propellant on the ablation rate of the throat liner and the thickness of the ablation steps. This study provides a theoretical foundation for the thermal protection design and performance optimization of composite nozzles, improving the reliability and service life of solid rocket motor nozzles and advancing technological development. Full article

Electrochemical nitrogen reduction reaction (NRR) has emerged as a promising approach for sustainable ammonia synthesis under ambient conditions, offering a low-energy alternative to the traditional Haber–Bosch process. However, the development of efficient and sustainable electrocatalysts for NRR remains a significant challenge. Noble metals, known for their exceptional chemical stability under electrocatalytic conditions, have garnered considerable attention in this field. In this study, we report the successful synthesis of nanoporous CuAuPtPd quasi-high-entropy alloy (quasi-HEA) prism arrays through “melt quenching” and “dealloying” techniques. The as-obtained alloy demonstrates remarkable performance as an NRR electrocatalyst, achieving an impressive ammonia synthesis rate of 17.5 μg h⁻¹ mg⁻¹ at a potential of −0.2 V vs. RHE, surpassing many previously reported NRR catalysts. This work not only highlights the potential of quasi-HEAs as advanced NRR electrocatalysts but also provides valuable insights into the design of nanoporous multicomponent materials for sustainable energy and catalytic applications. Full article

Tuberculosis (TB) remains one of the leading causes of mortality worldwide, exacerbated by the emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) Mycobacterium tuberculosis strains. In the pursuit of novel therapeutic strategies, thiazolidin-4-one derivatives have gained significant attention due to their structural diversity and broad-spectrum biological activities. This review provides a comprehensive summary of recent advances (2021–present) in the synthesis, structure–activity relationship (SAR), and mechanisms of action of thiazolidin-4-one derivatives as promising antitubercular agents. A detailed discussion of synthetic pathways is presented, including classical and multi-component reactions leading to various subclasses such as thiazolidine-2,4-diones, rhodanines, and pseudothiohydantoins. The SAR analysis highlights key functional groups that enhance antimycobacterial activity, such as halogen substitutions and heterocyclic linkers, while molecular docking and in vitro studies elucidate interactions with key Mtb targets including InhA, MmpL3, and DNA gyrase. Several compounds demonstrate potent inhibitory effects with MIC values lower than or comparable to first-line TB drugs, alongside favorable cytotoxicity profiles. These findings underscore the potential of thiazolidin-4-one scaffolds as a valuable platform for the development of next-generation antitubercular therapeutics. Full article

Tetrasubstituted furans and their derivatives represent a versatile class of important heterocyclic frameworks widely distributed in natural products. These scaffolds also demonstrate significant potential in pharmaceutical chemistry, materials science, and organic synthesis methodologies. In this study, we successfully established a synergistic catalytic system utilizing benzoylacetonitriles, aldehydes, and benzoyl chlorides as substrates, facilitated by tributylphosphine and immobilized lipase (Novozym 435), to achieve efficient synthesis of cyano-containing tetrasubstituted furans. Under optimized conditions, we obtained a series of target products exhibiting exceptional substrate tolerance with good to excellent isolated yields ranging from 80% to 94%. Additionally, we proposed a reasonable reaction mechanism and verified it through controlled experiments. This methodology not only expands the synthetic utility of lipase in non-natural transformations but also establishes a paradigm of green chemistry for the construction of tetrasubstituted furans. Full article

Methoxycamalexins are close structural derivatives of the indolic phytoalexin Camalexin, which is a well-known drug lead with an antiproliferative and antioxidant profile. 6-methoxycamalexin, 7-methoxycamalexin, and 6,7-dimethoxycamalexin are natural bioactive products, and there is significant interest in the development of efficient methods for the synthesis of structurally related analogues. Herein, we describe an efficient and high-yielding method for the synthesis of variously substituted hydroxy-, bezyloxy, and methoxycamalexins. A set of methoxy-, hydroxy-, and benzyloxy-indoles were successfully amidoalkylated with N-acyliminium reagents derived in situ from the reaction of thiazole or methylthiazoles with Troc chloride. Eleven novel N-acylated analogues were synthesized, with yields ranging from 77% to 98%. Subsequent oxidative reactions with o-chloranil or DDQ led to 10 novel oxy-camalexins in 62–98% yield. This two-step approach allowed the synthesis of two 4,6-dimethoxy camalexins, which are difficult to obtain using published methods. The structure of the obtained products was unequivocally determined by ¹H-, ¹³C{¹H}-, HSQC-NMR, FTIR, and HRMS spectral analyses. An in silico assay was carried out on the obtained products to assess their general toxicity and physicochemical properties, including their compliance with Lipinski’s rule of five. The results indicate that all compounds have good potential to be developed as drugs or agrochemicals. Full article

Quercetin, a natural flavonoid, present in various vegetables and fruits, has garnered increasing attraction for its potential antiallergic properties. Its broad-spectrum activity depends on its anti-inflammatory, immunomodulatory, and antioxidant effects, which target the critical pathways involved in type 2-driven allergic inflammation. Quercetin inhibits mast cell degranulation, reduces the production of histamine and pro-inflammatory cytokines, and restores homeostasis of the immune system by modulating the Th1/Th2 and Treg/Th17 balances. Additionally, its antioxidant properties help to dampen oxidative stress, a critical factor in the pathophysiology of allergic diseases. In vitro studies have consistently demonstrated quercetin’s ability to suppress allergic reactions. In contrast, in vivo studies, particularly in murine models of allergic rhinitis, have confirmed its efficacy in relieving symptoms (such as nasal itching, sneezing, rhinorrhea, and congestion) and dampening type 2 mucosal inflammation. Preclinical evidence also supports its therapeutic potential in asthma, conjunctivitis, atopic dermatitis, and food allergies. However, human studies are still scarce, as only two clinical trials investigated quercetin as a monotherapy. Both studies reported promising results, including symptom reduction and improved quality of life, though larger, randomized trials are needed to validate these findings. Some other studies have investigated multicomponent products that also contain quercetin. This review aimed to report and discuss the most recent in vitro and in vivo evidence on quercetin’s application in allergic models. It also provides a comprehensive overview of human studies, highlighting its potential as an agent in food supplements to manage patients with allergic diseases. Moreover, this review introduces a new quercetin phospholipids formulation that may represent a keystone in clinical use. The literature search was based on a PubMed consultation considering the most recent (last five years) publications using the keywords “quercetin and allergic disease” and “quercetin and immune system”. Full article

This paper presents and establishes a reaction kinetic model of Hg/Cl/C/H/O/N/S to investigate the reaction characteristics of mercury during coal combustion and elucidate its migration and transformation mechanisms in flue gas. Using CHEMKIN software, the influence of HCl, Cl₂, and other flue gas components on the mercury oxidation reaction rate is examined. Building on this, the mechanism of Hg homogeneous oxidation under the influence of multi-component and multi-reaction interactions is revealed. The results indicated that as Hg concentration increased, the transformation rate of mercury also increased. As the reaction temperature increases, the reaction rate of HCl and elemental mercury also increases, leading to a higher transformation rate of mercury at elevated temperatures. Additionally, an increase in Cl₂ concentration leads to a higher amount of HgCl₂ produced. When the Cl₂ concentration was 4 × 10⁻⁵ mol/L, the amount of mercury chloride produced was highest, increasing by 40% compared to the absence of Cl₂. As chlorine concentration increases, more Hg²⁺ is converted from Hg⁰, enhancing its capture and removal by existing technologies, which significantly contributes to environmental sustainability and mercury emission control in coal-fired power plants. It is also shown that the rate of change of HgCl₂ varies with different Cl₂ concentrations, with higher Cl₂ concentrations inhibiting mercury oxidation beyond a certain threshold. The reaction was most intense when the mercury concentration was 5 × 10⁻⁵ mol/L. At this concentration, the largest amount of HgCl₂ is produced. The mercury conversion rate curve remained consistent after adding NO and SO₂, with a HgCl₂ amount increasing as NO and SO₂ concentrations rose. This indicates that the addition of NO and SO₂ converts Hg⁰ to Hg²⁺, thereby improving mercury removal efficiency and contributing to sustainability. Full article

A comprehensive theoretical investigation of the C₃H₂O potential energy surface (PES) was conducted, revealing 30 equilibrium structures (EQs), 128 transition state structures (TSs), and 35 direct dissociation channels (DCs), establishing a global reaction network comprising 101 isomerization pathways and dissociation channels. Particular focus was placed on the five most stable isomers, H₂CCCO (EQ3), OC(H)CCH (EQ7), H-c-CC(O)C-H (EQ0), HCC(H)CO (EQ1), and HO-c-CCC-H (EQ12), and their reactions with water molecules. Multicomponent artificial force-induced reaction (MC-AFIR) calculations were employed to study bimolecular collisions between H₂O and these stable isomers. The product distributions revealed isomer-specific reactivity patterns: EQ3 and EQ7 predominantly formed neutral species at high collision energies, EQ0 produced both ionic and neutral species, while EQ1 and EQ12 exhibited more accessible reaction pathways at lower collision energies with a propensity for spontaneous isomerization. Born–Oppenheimer Molecular Dynamics (BOMD) simulations complemented these findings, suggesting several viable products emerge from reactions with water molecules, including HCCC(OH)₂H (EQ7 + H₂O), OCCHCH₂OH (EQ1 + H₂O), and HO-c-CC(H)C(OH)-H (EQ12 + H₂O). This investigation elucidates the intrinsic relationships between isomers and their potential products, formed through biomolecular collisions with water molecules, establishing a fundamental framework for future conformational and reactivity studies of the C₃H₂O family. Full article