Search Results (85)

Quinoline derivatives constitute a privileged class of nitrogen-containing heterocycles with extensive applications in medicinal chemistry, agrochemicals, materials science, and functional organic materials. Owing to their broad biological and industrial relevance, the development of efficient, selective, and sustainable synthetic methodologies for quinoline construction remains an active area of research. This review provides a comprehensive overview of recent advances in quinoline synthesis, with particular emphasis on catalytic strategies aligned with the principles of green and sustainable chemistry. Classical transformations, including the Friedländer, Skraup, and Povarov reactions, are revisited in the context of modern catalytic developments that improve reaction efficiency, substrate scope, selectivity, and environmental compatibility. Special attention is devoted to homogeneous and heterogeneous catalytic systems based on both platinum-group and earth-abundant transition metals, highlighting the growing importance of borrowing-hydrogen and acceptorless dehydrogenative coupling methodologies. Recent progress in nanocatalysis, photocatalysis, multicomponent reactions, ionic-liquid-mediated transformations, and metal-free protocols is also critically discussed. Furthermore, solvent-free processes, microwave-assisted synthesis, and recyclable catalytic systems are examined as practical approaches toward minimizing waste generation and energy consumption. Mechanistic aspects, catalytic design principles, substrate limitations, and sustainability metrics are evaluated throughout the review to provide a critical perspective on current methodologies. Collectively, the advances summarized herein demonstrate the rapid evolution of quinoline synthesis toward more atom-economical, environmentally benign, and operationally efficient processes, while also identifying future opportunities for the development of next-generation catalytic platforms for quinoline-based heterocycle construction. Full article

Fluorine-18 is often considered an ideal positron emitter owing to its excellent chemical, physiological, and nuclear properties. Consequently, the development of rapid, simple, and reliable ¹⁸F-labeling strategies remains critically important for synthesizing new radiopharmaceuticals for PET molecular imaging. A common approach involves the synthesis of ¹⁸F-labeled prosthetic groups that subsequently undergo bioconjugation with peptides or other biomolecules to generate ¹⁸F-labeled imaging probes. However, conventional synthetic methods for these prosthetic groups are often lengthy, require large quantities of precursor and solvent, and typically rely on elevated reaction temperatures. Herein, we report a droplet-based microscale synthetic methodology for the preparation of the [¹⁸F]FVSB prosthetic group that minimizes precursor and solvent usage, proceeds rapidly, and operates at relatively low temperatures. Conditions were optimized using a platform for performing droplet reactions in parallel, enabling high-throughput study of multiple reaction parameters within a short period of time. Additionally, we introduce a simple micro-cartridge purification technique that affords purified [¹⁸F]FVSB in small volumes. Furthermore, we describe an efficient bioconjugation that requires substantially lower reagent amounts than the previously reported macroscale method. The microscale process we report could facilitate wider use of this ¹⁸F-labeling strategy and can be extended to label other thiol-bearing peptides or biomolecules. Full article

Considering the expanded interest in reducing organic solvents in synthesis, surfactants and surfactant-based catalysis have been used to carry out various organic transformations in water. In recent years, the integration of Lewis and Brønsted acid catalysis with micellar systems has gained considerable attention as a powerful approach to enhance reaction efficiency while minimizing the environmental impact of synthetic processes. In this article, we depict the most recent advances in the water-interceded synthesis of different organic systems by utilizing different surfactant-type catalysts, which are important structural motifs in pharmaceuticals, agrochemicals and functional materials. Further, these methods incorporate green reaction media, mild reaction conditions, and a great yield of product with high purity in a shorter interval of time. Understanding the scope and impact of this area, authors have made efforts to collect and compile the data that indicates many named reactions, such as Friedlander annulation, aldol condensation, the Biginelli reaction, the Mannich reaction, Suzuki–Miyaura cross-coupling, etc., now take place using surfactant-based catalysts. Full article

Since the synthesis of ferrocene in 1951, metallocenes have attracted attention, making the accurate prediction of their electronic structure and ionization energy crucial for understanding their photophysical and electrochemical behavior in materials and in biological systems. Here, we combined Density Functional Theory (DFT), Complete Active Space Self-Consistent Field (CASSCF), NEVPT2 (N-Electron Valence State Perturbation Theory) and Coupled Cluster approaches (CCSD, DLPNO-CCSD(T)) to study the electronic structure, ionization energies (IEs) and absorption spectra of metallocene and metallocenium complexes in the gas phase and in THF implicit solvent. DFT IEs agree closely with NEVPT2 and DLPNO-CCSD(T) values and with experiment values (deviations 0.02–0.3 eV). For CASSCF and NEVPT2, the minimal active space of the d electrons at six orbitals is not enough for the accurate prediction of the IEs, while an extended active space incorporating all 3d metal electrons plus four ligand valence electrons into 15 orbitals improves the calculated IE values. In solution, computed oxidation energies (OEs) in THF reproduce experimental values and follow the Fe > Ni > Co ordering. Substitution of metallocene complexes with chromophore units results in similar OEs. Overall, the substitution effects remain modest: the effect of substitution on OE values results in differences up to 0.2 eV. These results clarify the effect of the metal center on IE and OE values and UV–vis absorption behavior. Full article

In this Short Note type article, we report the synthesis of a new hybrid molecule, N-(3,4-dimethoxyphenethyl)-2-propylpentanamide, using a solvent-minimized mechanochemical method that provides a simple and efficient synthetic approach. The process achieved high yield. The compound was confirmed by melting-point analysis, ¹H and ¹³C NMR, IR spectroscopy, and mass spectrometry. Full article

This review summarizes scientific advances about the sonochemical synthesis of starch nanoparticles (St-NPs) for the food industry, as well as nutraceutical and drug delivery applications. High-intensity ultrasonication (HIU) has been explored as a versatile and environmentally friendly alternative to conventional methods for synthesizing St-NPs with high yields (>90%), controlled size (~100 nm), and minimal effluent generation. Thus, HIU has been explored (pre- or post-treatment) to mitigate the inherent disadvantages (high-cost, low yields, and environmental impact) of hydrothermal gelatinization, acid/alkaline hydrolysis, enzymatic hydrolysis, enzyme branching, water-in-oil and oil-in-water emulsions, non-solvent nanoprecipitation, extrusion, high-pressure homogenization, high-energy milling, and cold plasma. Conventional sources of starch (corn [normal, waxy, high-amylose] and potato) and other unconventional sources (tubers [cassava, yam, malanga], seeds and grains [sorghum, barley, quinoa, lotus], breadfruit, pinhao seed, Araucaria angustifolia) have been subjected to single or assisted sonochemical protocols to obtain St-NPS with unique structural, physicochemical, and technological properties. The physical–mechanical effects of ultrasonication (cavitation, heat, and pressure) directly promote surface functionalization (i.e., esterification, pore formation) and impact the St-NPS’s particle size, double-helix structure, enzymatic-resistance properties, crystallinity, and intra- and intermolecular arrangements. Pickering additives in food systems, colloids in beverages, nanocomposites in biofilms for food packaging, and nanocarriers for drug and nutraceutical delivery (oral and transdermal) have been the most reported applications. Full article

The increasing demand for environmentally benign inorganic pigments has stimulated interest in sustainable synthesis routes for iron oxide nanoparticles that minimize toxic reagents and energy-intensive processing. In this study, a plant-mediated approach for the synthesis of hematite (α-Fe₂O₃) nanoparticles using Spinacia oleracea (spinach) leaf extract is presented, with particular emphasis on pigment-relevant material characteristics. An aqueous spinach extract was employed as a natural reducing and stabilizing medium for ferric ions under ambient conditions. The formation of iron oxide nanoparticles was indicated by a characteristic color change and confirmed by structural and morphological characterization. X-ray diffraction revealed phase-pure crystalline hematite, while transmission electron microscopy showed quasi-spherical nanoparticles with sizes in the range of 20–50 nm. The synthesis avoids hazardous chemicals, high-temperature calcination, and organic solvents, offering a low-energy and environmentally compatible route. Although the yield per batch is modest, the simplicity, non-toxicity, and pigment-suitable properties of the synthesized nanoparticles highlight the potential of this method for sustainable pigment and coating applications. Full article

Herein, we report the mechanochemical synthesis of a novel hybrid molecule, N-(4-methoxyphenethyl)-2-propylpentanamide. This solvent-minimized synthesis aligns with the principles of Green Chemistry and exemplifies the emerging paradigm of medicinal mechanochemistry, offering an efficient, sustainable route to pharmaceutically relevant amides. The newly synthesized compound was fully characterized by melting point determination, ¹H and ¹³C NMR spectroscopy, infrared (IR) spectroscopy, and mass spectrometry. Full article

Anthropogenic CO₂ emissions have accelerated climate change, prompting the need for effective capture technologies. Adsorption using clay-based sorbents offers an eco-friendly alternative, although performance often requires enhancement. This study explored mechanochemical modification of two halloysite-rich kaolin clay samples—iron-poor (Hal) and iron-rich (HalFe)—using locust bean gum and quillaja saponin and compared their CO₂ uptake with the calcined counterparts (CHal, CHalFe). All samples were characterized using standard techniques, and their CO₂ uptake was measured volumetrically across 0.1–20 bar and 15–35 °C. Modified sorbents showed enhanced mesoporosity and binding sites, increasing CO₂ uptake by up to 26% at 20 bar (11.85 mg/g) and 125% at 1 bar (2.25 mg/g). Calcination, however, reduced surface area and sorption capacity. Isosteric heat values remained within the physisorption range, as supported by FTIR, XRF, and XPS, which showed no bulk carbonate formation. These sorbents show lower CO₂ uptakes than conventional ones. Yet their low costs, abundance, biocompatibility, and solvent-free synthesis indicate strong potential for large-scale applications, especially for low-pressure implementations such as landfills. Further detailed studies on kinetics, thermodynamics, and sorbent regeneration are needed. Spent sorbents can potentially be repurposed for subsequent use in other applications, e.g., water treatment, construction materials, thereby minimizing waste production and supporting circular economy principles. Full article

The extraction of rare earth elements is becoming increasingly essential due to their many applications in current and emerging advanced material technologies. However, in many rare earth deposits, rare earth minerals are associated with radionuclides; specifically, thorium and uranium. The radioactive nature of these elements is a major concern during processing. Techniques such as solvent extraction and precipitation have been employed in this regard to minimize the radioactivity levels and address any related processing or environmental concerns. However, they face various challenges such as high chemical reagent consumption, secondary waste generation, and limited selectivity, which hinder either their scalability or sustainability. The current study provides a literature review about these technologies to provide critical insights on their applications and discuss the challenges hampering their extensive use in the mining industry. Biotechnology is also evaluated and highlighted as a promising, cost-effective, and low-environmental-impact option for the selective recovery of radionuclides from rare earth elements. Specifically, pyoverdine siderophores were discussed due to their catecholates and hydroxamate moieties which have high affinity for radionuclides to enhance selective recovery during rare earth processing. Conversely, integration of this approach into existing mineral processing flowsheets is a constraint. Hence, future studies should focus on optimizing the kinetics of siderophore synthesis and explore a hybrid approach to combine the biotechnological and conventional techniques. Full article

Neglected tropical diseases (NTDs) remain a significant global health burden, exacerbated by the ongoing climate emergency, which alters disease distribution and increases vulnerability in affected populations. The urgent need for novel therapeutics demands innovative approaches in drug discovery, with heterocyclic compounds serving as versatile scaffolds due to their diverse electronic and structural properties that enable potent biological activity. This review highlights how green chemistry principles have been applied to the construction of bioactive heterocyclic cores relevant to NTD drug development. Key sustainable methodologies are discussed, including microwave-assisted solvent-free and green-solvent reactions, ultrasound-assisted synthesis, mechanochemical one-pot multistep strategies, and the use of ionic liquids and deep eutectic solvents as environmentally benign catalysts and reaction media. By focusing on these approaches, the review emphasizes how green synthetic strategies can accelerate the development of pharmacologically relevant heterocycles while minimizing environmental impact, resource consumption, and hazardous waste generation. Full article

Under elevated loading conditions, the aggregation of fillers emerges as a pivotal factor driving the degradation of separation performance in mixed matrix membranes. The two-dimensional (2D) modification of fillers, aimed at enhancing interfacial contact with polymers, has been recognized as an effective strategy to improve interphase compatibility and increase filler loading capacity. However, it is worth noting that the BET surface area of 2D fillers is typically relatively low. In this study, a two-step approach was developed. First, a “diffusion-mediated” process was combined with a solvent optimization strategy based on first-principles (DFT) calculations, achieving a 20-fold suppression in ZIF-67 nucleation-crystallization rate. This enabled the successful synthesis of a 2D amorphous nanoflower structure. Subsequently, the processing parameters were fine-tuned to enhance the specific surface area of ZIF-67 to 403 m²/g while preserving its 2D structural integrity. Ultimately, the as-prepared 2D ZIF-67 was incorporated into a hydrogenated styrene-butadiene block copolymer (SEBS) matrix to fabricate a mixed matrix membrane. Remarkably, at a filler loading of 20 wt%, the CH₄ permeability coefficient increased significantly from 11.7 barrer to 35.3 barrer, while the CH₄/N₂ selectivity was maintained at 3.21, indicating minimal interfacial defects and demonstrating the feasibility and effectiveness of the proposed methodology. Full article

Isoxazole-based molecules constitute a crucial category of heterocyclic compounds with wide-ranging applications across pharmaceutical development, advanced materials, and pesticide synthesis. Traditional synthetic approaches for isoxazole derivatives frequently encounter challenges such as extended reaction periods, severe operating conditions, and reliance on toxic solvents. As an eco-friendly alternative, sonochemistry has emerged as a promising approach for organic synthesis, offering enhanced reaction efficiency, reduced energy consumption, and improved yields. In this context, this review introduces the recent advancements in ultrasound-assisted strategies for the synthesis of isoxazole-scaffolds and their derivatives. Various methodologies are discussed, including multi-component reactions, catalytic systems, and solvent-free protocols. The integration of ultrasound not only accelerates reaction kinetics but also minimizes byproduct formation and enables the use of green solvents or catalysts. Key advantages such as shorter reaction durations, higher atom economy, and operational simplicity are emphasized. This work underscores the potential of sonochemical techniques to revolutionize isoxazole-based molecule synthesis, aligning with the principles of sustainable and green chemistry. Full article

In this work, we report a green synthesis of zinc oxide (ZnO) nanoparticles using aqueous and ethanolic extracts of Tradescantia spathacea (purple maguey) as bioreducing and stabilizing agents, which are plant extracts not previously employed for metal oxide nanoparticle synthesis. This method provides an efficient, eco-friendly, and reproducible route to obtain ZnO nanoparticles, while minimizing environmental impact compared to conventional chemical approaches. The extracts were prepared following a standardized protocol, and their phytochemical profiles, including total phenolics, flavonoids, and antioxidant capacity, were quantified via UV-Vis spectroscopy to confirm their reducing potential. ZnO nanoparticles were synthesized using zinc acetate dihydrate as a precursor, with variations in pH and precursor concentration in both aqueous and ethanolic media. UV-Vis spectroscopy confirmed nanoparticle formation, while X-ray diffraction (XRD) revealed a hexagonal wurtzite structure with preferential (101) orientation and lattice parameters a = b = 3.244 Å, c = 5.197 Å. Scanning electron microscopy (SEM) showed agglomerated morphologies, and Fourier transform infrared spectroscopy (FTIR) confirmed the presence of phytochemicals such as quercetin, kaempferol, saponins, and terpenes, along with Zn–O bonding, indicating surface functionalization. Zeta potential measurements showed improved dispersion under alkaline conditions, particularly with ethanolic extracts. This study presents a sustainable synthesis strategy with tunable parameters, highlighting the critical influence of precursor concentration and solvent environment on ZnO nanoparticle formation. Notably, aqueous extracts promote ZnO synthesis at low precursor concentrations, while alkaline conditions are essential when using ethanolic extracts. Compared to other green synthesis methods, this strategy offers control and reproducibility and employs a non-toxic, underexplored plant source rich in phytochemicals, potentially enhancing the crystallinity, surface functionality, and application potential of the resulting ZnO nanoparticles. These materials show promise for applications in photocatalysis, in antimicrobial coatings, in UV-blocking formulations, and as functional additives in optoelectronic and environmental remediation technologies. Full article

This study reports an improved diastereoselective synthesis of substituted spiro[chromane-2,4′-pyrimidin]-2′(3′H)-ones via the acid-catalyzed condensation of 6-styryl-4-aryldihydropyrimidin-2-ones with resorcinol, 2-methylresorcinol, and pyrogallol. The optimized method allows for the isolation of diastereomerically pure products, with stereoselectivity controlled by varying acid catalysts (e.g., methanesulfonic acid vs. toluenesulfonic acid) and solvent conditions. The synthesized compounds were evaluated for antimicrobial and antioxidant activities. Notably, the (2S*,4R*,6′R*)-diastereomers exhibited significant antibacterial activity against both Gram-positive and Gram-negative bacterial strains with minimal inhibition concentration down to 2 µg/mL, while derivatives containing vicinal bisphenol moieties demonstrated potent antioxidant activity, with IC₅₀ values (12.5 µg/mL) comparable to ascorbic acid. Pharmacokinetic analysis of selected hit compounds revealed favorable drug-like properties, including high gastrointestinal absorption and blood-brain barrier permeability. These findings highlight the potential of spirochromane-pyrimidine hybrids as promising candidates for further development in the treatment of infectious diseases and oxidative stress-related pathologies. Full article