Search Results (104)

A library of neoisopulegol-based amino and thiol adducts was developed from (+)-neoisopulegol, derived from commercially available (−)-isopulegol. Michael addition of different nucleophiles towards its highly active α,β-unsaturated γ-lactone motif was accomplished, resulting in diverse amino and thiol analogs in stereoselective reactions. Then, the lactone ring was opened, with NH₃ and benzylamine furnishing primary amide and N-benzyl-substituted amide derivatives, respectively. The in vitro antimicrobial effect of prepared compounds was also explored. The results revealed that naphthylmethyl-substituted β-aminolactone, the most promising compound, displayed selective inhibition for the Gram-positive bacteria S. aureus with an MIC (minimum inhibitory concentration) value of 12.5 μM. A docking study was performed to interpret the obtained results. Full article

Strategic utilization of carbon dioxide as both a carbon mitigation tool and a sustainable C1 feedstock represents a pivotal pathway toward green chemistry. Although poly(ionic liquid)s (PILs) exhibit promise in CO₂ conversion, conventional divinylbenzene (DVB) cross-linked architectures are limited by reduced ionic density and limited accessibility of active sites. Herein, we reported a binuclear imidazolium-functionalized PIL catalyst (P-BVIMCl), synthesized through a simple self-polymerization process, derived from rationally designed ionic liquid monomers formed by quaternization of 1,4-bis(chloromethyl)benzene with N-vinylimidazole. The dual active sites in P-BVIMCl-quaternary ammonium cation (N⁺) and nucleophilic chloride anion (Cl⁻) synergistically enhanced CO₂ adsorption/activation and epoxide ring-opening. Under optimal catalyst preparation conditions (100 °C, 24 h, water/ethanol = 1:3 (v/v), 10 wt% AIBN initiator) and reaction conditions (100 °C, 2.0 MPa CO₂, 10 mmol epichlorohydrin, 6.7 wt% catalyst loading, 3.0 h), P-BVIMCl catalyzed the synthesis of glycerol carbonate (GLC) with a yield of up to 93.4% and selectivity of 99.6%, maintaining activity close to 90% after five cycles. Systematic characterization and density functional theory (DFT) calculations confirmed the synergistic activation mechanism. This work established a paradigm for constructing high-ionic-density catalysts through molecular engineering, advancing the development of high-performance PILs for industrial CO₂ valorization. Full article

The conversion of waste biomass into biochar through inert pyrolysis represents a promising strategy for carbon sequestration. However, biochar production is often accompanied by the release of small molecular chemical substances during pyrolysis, and the resulting biochar is susceptible to environmental degradation. To enhance the carbon retention rate of biochar during pyrolysis and its stability in the environment, this study explored the incorporation of various metal soluble salts (CaCl₂, Ca(H₂PO₄)₂, MgCl₂, FeCl₃) and clay minerals (quartz, goethite, bentonite, albite) with two types of waste biomass (phragmites and goldenrod) for pre-treatment to enhance both carbon retention and stability in the resulting biochar. Furthermore, to elucidate the regulatory mechanisms of minerals on biochar structural formation, the three primary components of raw biomass—hemicellulose, cellulose, and lignin—were individually mixed with the minerals at a ratio of 1:5 (mineral/biomass, w/w) to produce biochars for a comparative analysis. The experimental results demonstrated that metal soluble salts, particularly Ca(H₂PO₄)₂, exhibited a superior performance in enhancing biochar’s carbon retention compared to clay minerals. Specifically, Ca(H₂PO₄)₂ treatment resulted in a remarkable 15% increase in the carbon retention rate. Through K₂Cr₂O₇ oxidation simulating soil aging conditions, Ca(H₂PO₄)₂-treated biochar showed approximately 12% greater stability than the untreated samples. This enhanced stability was primarily attributed to the formation of stable chemical bonds (C–O–P and P–O), which facilitated the preservation of aromatic carbon structures and small molecular compounds including sugars, alcohols, and ethers. Mechanistic investigations revealed that Ca(H₂PO₄)₂ significantly influenced the pyrolysis process by increasing the activation energy from 85.9 kJ mol⁻¹ to 156.5 kJ mol⁻¹ and introducing greater reaction complexity. During the initial pyrolysis stage (<300 °C), Ca(H₂PO₄)₂ catalyzed depolymerization, ring-opening, and C–C bond cleavage in hemicellulose, enhanced cellulose depolymerization, and side-chain cleavage in lignin phenylpropanes. In the intermediate temperature range (300–400 °C), Ca(H₂PO₄)₂ facilitated carboxylate nucleophilic addition reactions and promoted cyclization to form aromatic carbon structures. The innovative aspect of this work is that minerals can increase both the yield and carbon retention rate of biochar. Furthermore, it reveals the mechanisms underlying the improvements in pyrolysis, providing a scientific basis and theoretical foundation for better displaying the carbon sequestration potential of biochar in future applications. Full article

The rapid advancement of 3D packaging technology has emerged as a key solution to overcome the scaling-down limitation of advanced memory and logic devices. Redistribution layer (RDL) fabrication, a critical process in 3D packaging, requires the use of polyimide (PI) films with thicknesses in the micrometer range. However, these polyimide films present surface topography variations in the range of hundreds of nanometers, necessitating chemical–mechanical planarization (CMP) to achieve nanometer-level surface flatness. Polyimide films, composed of copolymers of pyromellitimide and diphenyl ether, possess strong covalent bonds such as C–C, C–O, C=O, and C–N, leading to inherently low polishing rates during CMP. To address this challenge, the introduction of Fe(NO₃)₃ into CMP slurries has been proposed as a polishing rate accelerator. During CMP, this Fe(NO₃)₃ deformed the surface of a polyimide film into strongly positively charged 1,2,4,5-benzenetetracarbonyliron and weakly negatively charged 4,4′-oxydianiline (ODA). The chemically dominant polishing rate enhanced with the concentration of the Fe(NO₃)₃ due to accelerated surface interactions. However, higher Fe(NO₃)₃ concentrations reduce the attractive electrostatic force between the positively charged wet ceria abrasives and the negatively charged deformed surface of the polyimide film, thereby decreasing the mechanically dominant polishing rate. A comprehensive investigation of the chemical and mechanical polishing rate dynamics revealed that the optimal Fe(NO₃)₃ concentration to achieve the maximum polyimide film removal rate was 0.05 wt%. Full article

In the 21st century, sustainable agriculture is expected to become a major contributor to food security and improved nutrition. Amine–epoxide-based materials have great potential for use in agriculture due to their tunable physicochemical features, which are dependent on the concentration and composition of the monomers. In this work, catalyst-free green synthesis, using only water as a solvent, was performed to obtain a nanocarrier (TGel) capable of transporting nutrients after seed priming. The synthesis was based on the opening of the epoxy ring by nucleophile attack, using an amine-terminated polyether. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) techniques showed the spherical morphology of the particles, which ranged in size from 80 nm (unloaded TGel) to 360 nm (zinc-loaded TGel), respectively. Theoretical bonding analysis revealed that Zn cation species from the ZnSO₄ source interact with the polymer via σ-bonds, whereas EDTA forms hydrogen bonds with the polymer, thereby enhancing noncovalent interactions. Micro X-ray fluorescence (μ-XRF) and energy-dispersive X-ray fluorescence spectroscopy (EDXRF) provided details of the distributions of Zn in the seed compartments and shoots of cucumber plants after seed priming and plant growth, respectively. The use of the Zn-loaded TGels did not affect the physiology of the cucumber plants, as indicated by the photosynthetic efficacy, chlorophyll, and anthocyanin indices. Full article

Recently, nitrostilbenes characterized by two different or differently substituted aryl moieties, obtainable from the initial ring-opening of 3-nitrobenzo[b]thiophene with amines, have proved, by means of a stepwise double coupling with phenolic-type bidentate C/O nucleophiles, to be valuable precursors of oxygen-containing heteropolycycles and of fully conjugated systems therefrom via an efficient 6π-electrocyclization and final aromatization. Herein, the methodology is extended, after suitable optimization, to diverse heterophenols to afford new appealing heteropolycyclic systems of potential interest as drug leads. The synthetic results are fully consistent with up-to-date quantomechanical calculations. For some of the new molecules, a significant fluorescence is reported, with a potential for future applications, e.g., in the field of optical devices. Full article

1,5-Acrylodan (1-(5-(dimethylamino)naphthalen-1-yl)prop-2-en-1-one) is prepared in six steps from 1-nitronaphthalene and 19% overall yield. The last three steps involve an aryllithium-directed nucleophilic addition, catalytic Kulinkovich cyclopropanation, and copper-catalyzed oxidative ring-opening to generate the acryloyl moiety. The fluorescent properties of 1,5-Acrylodan (AC) are reported. These include its solvatochromism and H-bond quenching by protic solvents. Its use as a bioconjugate sensor is demonstrated with Human Serum Albumin (HSA) through its covalent attachment to Human Serum Albumin (HSA) at the free cysteine-34 moiety. Unfolding studies with guanidinium chloride (GdmCl) and sodium dodecyl sulfate (SDS) are conducted to illustrate how the fluorophore responds to changes in both micropolarity and exposure to water. Full article

A new aluminum complex (NSO)AlMe₂ featuring a hydrogen bond donor on the ligand backbone has been synthesized via the reaction of AlMe₃ with 1-((2-(isopropylamino)phenyl)thio)propan-2-ol (NSO-H) and spectroscopically characterized. In the complex, the aluminum atom is in a distorted tetrahedral coordination sphere determined by the anionic oxygen and neutral nitrogen atoms of the ligand and by the two carbon atoms of the alkyl groups. After proper activation, the complex (NSO)AlMe₂ was able to promote the ring-opening polymerization of L-, rac-lactide, ε-caprolactone and rac-β-butyrolactone. The polymerization of rac-lactide was faster than that of L-lactide: in a toluene solution at 80 °C, the high monomer conversion of 100 equivalents was achieved in 1.5 h, reaching a turnover frequency of 63 mol_LA·mol_Al^–1·h^–1. The experimental molecular weights of the obtained polymers were close to those calculated, assuming the growth of one polymer chain for one added alcohol equivalent and the polydispersity indexes were monomodal and narrow. The kinetic investigation of the polymerization led to the determination of the apparent propagation constants and the Gibbs free energies of activation for the reaction; the terminal groups of the polymers were also identified. The complex (NSO)AlMe₂ was active in harsh conditions such as at a very low concentration or in the melt using technical-grade rac-lactide. A relatively high level of activity was observed in the ring-opening polymerization of ε-caprolactone and rac-β-butyrolactone. DFT calculations were performed and revealed the central role of the NH function of the coordinated ligand. Acting as a hydrogen bond donor, it docks the monomer in the proximity of the metal center and activates it toward the nucleophilic attack of the growing polymer chain. Full article

The smallest strained, saturated N-heterocycles, such as aziridine, can be a valuable building block in synthetic organic chemistry. Ring-opening reactions with various nucleophiles could be the most important strategy to synthesize various value-added molecular entities. Therefore, regioselective ring-opening reactions of aziridines with various heteroatomic nucleophiles and carbon nucleophiles establish a useful synthetic methodology to synthesize biologically relevant β-functionalized alkylamines. The regio-selective ring-opening of aziridines is highly dependent on the substrate combination, and stereochemical control is challenging for Lewis acid-promoted reactions. Therefore, the development of a robust, catalytic ring-opening process that assists in the accurate prediction of regioselectivity and stereochemistry is highly desirable. Consequently, a large number of publications detailing distinct methods for aziridine ring-opening reactions can be found in the literature. In this review, we discuss several transition metal catalyzed cross-coupling reaction protocols for the ring opening of substituted aziridines with various carbon nucleophiles. Full article

Selenium-containing molecules represent a valuable class of compounds with a variety of applications in chemical and biological fields. Selenated reagents are used as intermediates to introduce functional groups (e.g., double bonds) onto different substrates or in the synthesis of various selenated derivatives. Among the variety of selenium-containing reagents, silyl selenides are frequently used to transfer a selenated moiety due to the smooth functionalization of the Se-Si bond, which allows for the generation of selenium nucleophilic species under mild conditions. While the use of the analogous sulfur nucleophiles, namely silyl sulfides, has been widely explored, a relatively limited number of reports on selenosilanes have been provided. This contribution will focus on the application of selenosilanes as nucleophiles in a variety of organic transformations, as well as under radical and redox conditions. The use of silyl selenides to prepare metal complexes and as selenium precursors of materials for atomic layer deposition will also be discussed. Full article

There are great challenges in the field of natural product isolation and purification and in the pharmacological study of oligosaccharide monomers. And these isolation and purification processes are still universal problems in the study of natural products (NPs), traditional Chinese medicine (TCM), omics, etc. The same polymer-modified materials designed for the special separation of oligosaccharides, named Sil-epoxy-PEI and Sil-chloropropyl-PEI, were synthesized via two different methods and characterized by scanning electron microscopy combined with energy spectrum analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, zeta potential as well as surface area analysis, etc. Several nucleotide/nucleoside molecules with different polarities and selectivities were successfully isolated in our laboratory using stainless-steel columns filled with the synthesized material. In addition, the separation of saccharide probes and oligosaccharides mixtures in water extracts of Morinda officinalis were compared in HILIC mode. The results showed that the resolution of separations for the representative analytes of the Sil-epoxy-PEI column was higher than for the Sil-chloropropyl-PEI column, and the developed stationary phase exhibited improved performance compared to hydrothermal carbon, amide columns and other HILIC materials previously reported. Full article

The amino acid L-histidine, which has an imidazole ring, was investigated as a corrosion inhibitor for AISI 1018 carbon steel in chloride solution based on the effectiveness of inhibitors containing imidazole in their composition. A neutral environment was chosen for this study due to the scarcity of research on this amino acid in this environment type. Concentrations of 250, 500, and 1000 ppm were evaluated. Various methods were used to determine inhibition effectiveness, including mass loss, open circuit potential, linear potentiodynamic polarization, and electrochemical impedance spectroscopy. For mass loss, the inhibition efficiency varied from 83 to 88% according to the increase in concentration. For the electrochemical tests, the efficiency variation ranged from 62 to 90% with increasing amino acid concentration. Furthermore, a simulation analysis using quantum chemical calculations within the scope of Density Functional Theory (DFT) revealed that histidine’s nucleophilic character is crucial for its corrosion inhibitory capacity in an aqueous medium at pH 7. The inhibition efficiency increased with increasing concentration in a neutral medium, following the Langmuir isotherm for the adsorption of L-histidine. Additional studies were carried out using Fourier transform infrared spectroscopy (FTIR) and thermogravimetry (TGA). Analysis of the substrate surface by scanning electron microscopy (SEM) showed greater preservation with the addition of L-histidine, confirming its adsorption on the steel. Atomic Force Microscopy (AFM) also demonstrated an improvement in surface roughness in the presence of amino acids compared to the medium without an inhibitor. Full article

Malamides (diamide derivatives of malic acid) are prevalent in nature and of significant biological interest, yet only limited synthetic methods to access functionalised enantiopure derivatives have been established to date. Herein, an effective synthetic method to generate this molecular class is developed through in situ formation of spirocyclic β-lactone-oxindoles (employing a known enantioselective isothiourea-catalysed formal [2+2] cycloaddition of C(1)-ammonium enolates and isatin derivatives) followed by a subsequent dual ring-opening protocol (of the β-lactone and oxindole) with amine nucleophiles. The application of this protocol is demonstrated across twelve examples to give densely functionalised malamide derivatives with high enantio- and diastereo-selectivity (up to >95:5 dr and >99:1 er). Full article

The increase in the resistance of mutant strains of Neisseria gonorrhoeae to the antibiotic ceftriaxone is pronounced in the decrease in the second-order acylation rate constant, k₂/K_S, by penicillin-binding protein 2 (PBP2). These changes can be caused by both the decrease in the acylation rate constant, k₂, and the weakening of the binding affinity, i.e., an increase in the substrate constant, K_S. A501X mutations in PBP2 affect second-order acylation rate constants. The PBP2^A501V variant exhibits a higher k₂/K_S value, whereas for PBP2^A501R and PBP2^A501P variants, these values are lower. We performed molecular dynamic simulations with both classical and QM/MM potentials to model both acylation energy profiles and conformational dynamics of four PBP2 variants to explain the origin of k₂/K_S changes. The acylation reaction occurs in two elementary steps, specifically, a nucleophilic attack by the oxygen atom of the Ser310 residue and C–N bond cleavage in the β-lactam ring accompanied by the elimination of the leaving group of ceftriaxone. The energy barrier of the first step increases for PBP2 variants with a decrease in the observed k₂/K_S value. Submicrosecond classic molecular dynamic trajectories with subsequent cluster analysis reveal that the conformation of the β₃–β₄ loop switches from open to closed and its flexibility decreases for PBP2 variants with a lower k₂/K_S value. Thus, the experimentally observed decrease in the k₂/K_S in A501X variants of PBP2 occurs due to both the decrease in the acylation rate constant, k₂, and the increase in K_S. Full article

Using Ni(II) as the catalyst, electron-deficient 3,5-dimethylacryloylpyrazole olefin was reacted with C,N-diarylnitrones alone for 10 min to prepare novel five-member heterocyclic products, 4-3,5-dimethylacryloylpyrazole isoxazolidines with 100% regioselectivity and up to 99% yield. And then, taking these cycloadducts as substrates, six kinds of derivatization reactions, like ring-opening, nucleophilic substitution, addition-elimination and reduction, were studied. Experimental results showed that all kinds of transformations could obtain the target products at a high conversion rate under mild conditions, a finding which provided the basic methods for organic synthesis methodology research based on an isoxazolidine skeleton. Full article