Search Results (211)

Schiff bases are bioactive compounds that have been synthesized by many researchers in recent years. They may also exhibit strong antimicrobial activities against various pathogenic microorganisms in both medicine and veterinary applications. The synthesis of new Schiff base-derived compounds remains of interest due to the increasing problem of antibiotic-resistance in clinical practice. Seven new Schiff base derivatives were synthesized, and their chemical structures were characterized using FT-IR, ¹H/¹³C NMR, and LCMS-MS analyses. The antimicrobial activities of thesyntesized compounds against various pathogenic bacteria, yeasts, and fungi were evaluated using the disk-diffusion method, and their MIC values were also determined. In addition, one representative microorganisms from each class were selected for molecular docking studies. IFD analyses were performed for the 4f and 4g ligands using the dihydrofolate reductase enzyme. Spectroscopic analyses confirmed the structures of the synthesized compounds, revealing the presence of characteristic imine functionalities and validating the integrity of the molecular frameworks. Antimicrobial assays demonstrated that several derivatives exhibited measurable activity, with compounds 4f and 4g showing the most potent effects, displaying MIC values of 32 µg/mL against B. cereus and E. faecalis, respectively. Molecular docking studies further indicated that both 4f and 4g bind efficiently to the DHFR active site. These findings indicate that among the synthesized Schiff base derivatives, compounds 4f and 4g exhibit particularly promising antimicrobial activity, warranting further pharmacological evaluation and medicinal chemistry optimization. Full article

A strategy for constructing trifluoromethylated spiroisoxazolones has been developed. This approach relies on the 1,3-dipolar cycloaddition of CF₃-substituted nitrile imines, generated in situ from trifluoroacetyl hydrazonoyl bromides and K₂CO₃, with the exocyclic double bond of 4-benzylidene-3-methylisoxazol-5(4H)-ones. The reaction provides a series of trifluoromethylated spiro(isoxazolone-pyrazoline) derivatives in moderate to high yields (up to 93%). The protocol exhibits broad substrate compatibility with respect to aromatic substituents on both reaction partners. To the best of our knowledge, the introduction of a trifluoromethyl group at the 3-position of the pyrazoline ring via nitrile imine cycloaddition chemistry has not been previously reported. The resulting products incorporate a valuable CF₃-substituted pyrazoline pharmacophore spiro-fused to an isoxazolone core and may be of interest for medicinal chemistry programs. Full article

Non-cephem drugs with 1,3-thiazine-derived rings are very rare, although a number of bioactive 1,3-thiazine derivatives are known. Similarly, 1,4-thiazepine-derived drugs are rare, but many 1,4-thiazepine derivatives show interesting biological activities. Therefore, our aim was the synthesis of such N,S-heterocycles using a versatile and short (1–3 steps) literature method. First, a three-component reaction of a cycloalkene, a thioamide, and an aldehyde provided 5,6-dihydro-4H-1,3-thiazines. Afterwards, Staudinger ketene–imine cycloaddition with chloroketene resulted in β-lactam-fused 1,3-thiazinanes. Finally, treatment with sodium methoxide induced ring expansion, yielding 4,5,6,7-tetrahydro-1,4-thiazepines. This synthetic pathway generates 3–5 new chiral centers with the help of pericyclic reactions, and almost every cycloaddition proceeded in a diastereoselective manner. Two-dimensional NOESY as well as single-crystal X-ray diffraction enabled unequivocal determination of the stereochemistry of all synthesized compounds. Full article

Herein, we prepared nanoparticles of chitosan–manganese(II) complexes in different molar ratios (1:2, 1:1, and 2:1) and fully characterized them using dynamic and electrophoretic light scattering, X-ray diffraction, SEM, FTIR, and thermal analysis. Nanoparticles Chitosan + Mn²⁺ (1:1) have a high catalytic activity in the oxidative coupling of benzylamine, resulting in the imine formation and also in selective aldol reaction. Chitosan + Mn²⁺ (1:1) catalyze the reactions in the greenest solvents: water and water/ethanol mixture. Moreover, Chitosan + Mn²⁺ (1:1) is very easy to prepare and convenient to use. The catalyst is separated from the reaction mixture by a simple nanoporous filter or centrifugation and does not lose catalytic activity after at least ten uses. The chitosan–manganese(II) complexes reduce the milk fermentation time, demonstrating the effectiveness in accelerating the fermentation process by Streptococcus thermophilus. They also contribute to increasing the shelf life of fermented milk products by inhibiting the undesirable post-acidification process. We found that the optimal ratio of chitosan and Mn²⁺ to manifest the apogee of the desired effects (acceleration of milk fermentation and increase in the shelf life of the fermented product) is 1:2. Full article

Benzoxazoles are recognized as significant building blocks in organic synthesis and materials science. This work observed the formation of benzoxazole from o-aminophenol and o-hydroxybenzaldehyde using online ¹H NMR (continuous flow cell, 80 MHz). The identification of changes in the functional group was complemented by ATR-FTIR analysis. Additionally, the kinetic roles of phenylboronic acid and cyanide in the one-pot condensation-cyclization reaction are examined. Real-time monitoring has revealed three observable events: the rapid condensation of the aldehyde and o-aminophenol to produce the imine; the formation of the boron complex in the presence of phenylboronic acid; and the cyanide-assisted cyclization that converts the intermediate into benzoxazole. The findings clarify the transformations that control throughput and provide valuable insights for optimizing reagent loadings under environmentally friendly conditions. Full article

β-Lactams are key scaffolds in synthetic and medicinal chemistry, valued for both therapeutic relevance and synthetic utility. Classical ketene-imine [2+2] cycloadditions often employ stabilized aryl ketenes, which display reduced reactivity and modest stereoselective. Disruption of π-conjugation in N-pyrrolylketene has been shown to enhance electrophilicity and direct stereochemical outcomes in reactions with aromatic imines. The ketene, generated in situ from N-pyrrolylpropanoic acid, undergoes cycloaddition under mild conditions to give β-lactams with a strong preference for the trans isomer. Frontier molecular orbital analysis and mechanistic interpretation suggest a polar asynchronous pathway, highlighting ketene destabilization as a practical strategy for stereoselective β-lactam synthesis. Full article

Epoxy resins are valuable in aerospace, electronics, and high-performance industries; however, their inherently low thermal conductivity (TC) limits applications requiring effective heat dissipation. Recent reports suggest that certain liquid crystalline or partially crystalline epoxy formulations can achieve higher TC, even exceeding 1 W/(m·K). To investigate this, 17 epoxy formulations were prepared, including the commonly used diglycidyl ether of bisphenol A (DGEBA) and two custom-synthesized diepoxides: TME4, which contains rigid aromatic ester linkages with a C4 aliphatic spacer, and LCE-DP, featuring rigid imine bonds. Thermal conductivity was measured using four techniques: laser flash analysis (LFA), modified transient plane source (MTPS), time-domain thermoreflectance (TDTR), and displacement thermo-optic phase spectroscopy (D-TOPS). Additionally, small-angle and wide-angle X-ray scattering (SAXS/WAXS) were performed to detect crystalline or liquid crystalline domains. All formulations exhibited TC values ranging from 0.13 to 0.32 W/(m·K). The TME4–DDS systems, previously reported to be near 1 W/(m·K), consistently measured between 0.26 and 0.30 W/(m·K). Thus, under our synthesis and curing conditions, the elevated TC reported in prior studies was not reproduced, and no strong evidence of crystallinity was observed; indications of local ordering did not translate into higher conductivity. Variations in TC among methods often matched or exceeded the gains attributed to mesophase formation. More broadly, evidence for crystallinity in epoxy thermosets appears weak, consistent with the notion that crosslinking suppresses long-range ordering. Full article

In this work, a new asymmetric amidine–imine ligand, using 1,8-diaminonaphthalene as a rigid platform, was synthesized and characterized, and its ability to form complexes with aluminum(III) was investigated. Several aluminum complexes were synthesized and characterized in solution and in the solid state. The synthesis of a dihalogenated aluminum(III) complex (AlI₂L) using a reducing agent revealed an atypical pathway, which was investigated using Density Functional Theory (DFT). The dimethylated aluminum complex AlMe₂L and the dihalogenated aluminum complex AlI₂L were evaluated as catalysts for the transformation of CO₂ and epoxides into cyclic carbonates in the presence of Bu₄NI as a co-catalyst or in a single-component system, respectively. AlMe₂L/Bu₄NI appeared to be the most efficient system under 1 bar of CO₂ at 90 °C. Full article

Quinazoline is a privileged heterocyclic scaffold commonly found in numerous pharmaceuticals and bioactive natural products, known for its diverse biological activities. The pursuit of efficient and versatile synthetic methods to produce quinazoline derivatives remains a central focus for organic and medicinal chemists, owing to the therapeutic potential of these compounds. This paper reviews the innovative use of 2-azidobenzaldehyde-enabled annulation strategies for the synthesis of quinazoline derivatives, including quinazolin-4(3H)-one, 2,3-dihydroquinazolin-4(1H)-one, 3,4-dihydroquinazoline, 3,4-dihydroquinazoline-2(1H)-thione, and 1,2,3,4-tetrahydroquinazoline. Emphasizing both the mechanistic insights and practical advantages, this review highlights the efficacy and applicability of these methods in the domain of heterocyclic chemistry, providing an invaluable framework for future drug discovery and development efforts. Full article

Nitrile imines and nitrile oxides are capable of undergoing (3+2)-cycloaddition reactions at double and triple carbon–carbon, carbon-heteroatom, or heteroatom–heteroatom bonds of various dipolarophiles, forming five-membered heterocyclic compounds. When cyclic dipolarophiles bearing an exocyclic carbon–nitrogen double bond (exo-C=N) are introduced into the reaction with these dipoles, spiro-fused 1,2,4-triazoline or 1,2,4-oxadiazoline cycles are formed. Such reactions can provide efficient synthetic approaches to spiro-heterocyclic compounds with enhanced biological activity. This review comprehensively summarizes the literature data on the 1,3-dipolar cycloaddition of nitrile imines and nitrile oxides to exo-C=N bonds for spiro compound synthesis. The research area covers reactions of both saturated and unsaturated dipolarophiles, monocyclic and polycyclic molecules, as well as compounds containing one to three heteroatoms, with special emphasis on systems containing biologically significant heterocyclic pharmacophores. Recent advances in reaction techniques, such as microwave and ultrasonic activation, as well as one-pot and diffusion protocols, are also mentioned. Full article

Ethylene imine-based porous polymer nanocomposites were prepared by ring-opening polymerization of 2,2-bishydroxymethylbutanol-tris [3-(1-aziridinyl)propionate] (3AZ), a tri-functional aziridine compound, in the presence of commercially available metal oxide nanoparticles, SiO₂ or ZrO₂, accompanied by polymerization-induced phase separation. The reactions with SiO₂ and ZrO₂ nanoparticles successfully yielded nanocomposite porous polymers as rigid materials. The nanocomposite porous polymers with SiO₂ and ZrO₂ nanoparticles showed characteristic surface morphologies composed of gathered particles with diameters less than 1 micrometer. These nanocomposites were effective in increasing Young’s moduli of the porous polymers due to an increase in their bulk densities. The presence of SiO₂ and ZrO₂ nanoparticles in the porous polymers efficiently retarded thermal decomposition. Full article

The present study reports the sono-chemical synthesis of novel nanosized Cr(III), Mn(II), and Pd(II) complexes incorporating the chloro-2-(quinolin-8-yliminomethyl)-phenol imine ligand. The synthesized complexes were characterized using various spectroscopic and analytical techniques, including Fourier-transform infrared (FT-IR) spectroscopy, ultraviolet–visible (UV–Vis) spectroscopy, scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA). The results confirmed the successful coordination of the ligand-to-metal centers, forming stable nanosized metal complexes with distinct physicochemical properties. Biological evaluations, including antimicrobial and antioxidant assays, revealed that the synthesized complexes exhibited enhanced biological activity compared to the free ligand, demonstrating potent antibacterial and antifungal properties against various pathogenic strains. The potential of the complexes to serve as efficient free-radical inhibitors was determined by employing DPPH radical scavenging assays, which underscored their significant antioxidant properties. Furthermore, molecular docking studies were conducted to elucidate the binding interactions of the metal complexes with biological targets, providing insights into their mechanism of action. The findings suggest that the synthesized nanosized Cr(III), Mn(II), and Pd(II) complexes possess promising biological properties, making them potential candidates for pharmaceutical and biomedical applications. The study also demonstrates the effectiveness of sono-chemical synthesis in producing nanosized metal complexes with enhanced physicochemical and biological characteristics. Full article

Background/Objectives: To design the pDNA delivery carrier for delivery into skeletal muscle, a total of twelve terminal-alkylated PEGs (Cx-I-PEGy) with four alkyl groups of different carbon numbers (Cx: x = 4, 8, 12, 16) modified via an imine spacer at the ends of three methoxy PEGs of different molecular weights (PEGy: y = 500, 2k, 5k) have been synthesized. Methods: Among them, four Cx-I-PEG5k formed an imine-mediated complex formation with pDNA, as assessed by agarose gel electrophoresis, defined as an iminium mono-ion complex (I-MIC) without multivalent electrostatic interaction by minimizing potential toxic cations. Results: Most resulting I-MICs maintained the flexible structure of pDNA and promoted the binding to pDNA. The expression of pDNA by intramuscular injection with the resulting I-MICs was the highest by using I-MICs with C4-I-PEG5k and was observed extensively by the in vivo imaging system (IVIS). Conclusions: These results suggest that the I-MICs with C4-I-PEG5k are promising for pDNA transfection into skeletal muscle, offering the alkyl iminium for the pDNA binding group to demonstrate the factor of pDNA’s flexible structure as one of the key parameters for in vivo local pDNA transfection. Full article

Ultra-high-molecular-weight polyethylene (UHMWPE) is a pivotal material in engineering and biomedical applications due to its exceptional mechanical strength, wear resistance, and impact performance. However, its extreme melt viscosity, caused by extensive chain entanglements, severely limits processability via conventional melt-processing techniques. Recent advances in catalytic synthesis have enabled the production of disentangled UHMWPE (dis-UHMWPE), which exhibits enhanced processability while retaining superior mechanical properties. Notably, heterogeneous catalytic systems, utilizing supported fluorinated bis (phenoxy-imine) titanium (FI) catalysts, polyhedral oligomeric silsesquioxanes (POSS)-modified Z-N catalysts, and other novel catalysts, have emerged as promising solutions, combining structural control with industrial feasibility. Moreover, optimizing polymerization conditions further enhances chain disentanglement while maintaining ultra-high molecular weights. These systems utilize nanoscale supports and ligand engineering to spatially isolate active sites, tailor the chain propagation/crystallization kinetics, and suppress interchain entanglement during polymerization. Furthermore, characterization techniques such as melt rheology and differential scanning calorimetry (DSC) provide critical insights into chain entanglement, revealing distinct reorganization kinetics and bimodal melting behavior in dis-UHMWPE. This development of hybrid catalytic systems opens up new avenues for solid-state processing and industrial-scale production. This review highlights recent advances concerning interaction between catalyst design, polymerization control, and material performance, ultimately unlocking the full potential of UHMWPE for next-generation applications. Full article

Imine-linked covalent organic frameworks (COFs) have attracted considerable interest in recent years because they can form strong and reversible covalent bonds, enabling the development of highly ordered crystalline structures. This reversibility is crucial in correcting structural defects during the crystallization process, which requires sufficient time to proceed. This review critically examines the advancements in synthetic strategies for these valuable materials, focusing on catalytic versus conventional approaches. Traditional methods for synthesizing imine-linked COFs often involve harsh reaction conditions and prolonged reaction times, which can limit the scalability and environmental sustainability of these frameworks. In contrast, catalytic approaches offer more efficient pathways, enabling shorter reaction times, milder reaction conditions, and higher yields. This article elucidates the key differences between these methodologies and examines the impact of reduced reaction times and milder conditions on the crystallinity and porosity of COFs. By comparing the catalytic and conventional synthesis routes, this review aims to provide a comprehensive understanding of the advantages and limitations of each approach, offering insights into the optimal strategies for the development of high-performance COFs. Full article