Search Results (1,578)

Background/Objectives: [¹⁸F]Fluproxadine (formerly [¹⁸F]AF78) is a PET radiotracer targeting the norepinephrine transporter (NET) with potential applications in cardiac, neurological, and oncological imaging. Its guanidine moiety, while essential for NET binding, presents major radiosynthetic challenges due to high basicity and the harsh deprotection conditions required for protected precursors. Previous methods relied on multistep procedures, strong acids, and complex purification, limiting clinical translation. This study aimed to develop a practical one-step radiosynthesis suitable for routine and automated production. Methods: A direct SN2-type nucleophilic [¹⁸F]fluorination was performed using an unprotected guanidine precursor to eliminate deprotection steps. Reaction parameters, including the base system, solvent composition, precursor concentration, and temperature, were optimized under conventional and microwave heating. Radiochemical conversion (RCC) and operational robustness were evaluated, and purification strategies were assessed for automation compatibility. Results: Direct [¹⁸F]fluorination using the unprotected precursor reduced the total synthesis time to 60–70 min. Optimal conditions employed a tert-butanol/acetonitrile (4:1) solvent system with K₂CO₃/Kryptofix222, affording RCC up to 33% under conventional heating. Microwave irradiation further improved efficiency, achieving RCC of up to 64% within 1.5 min at 140 °C. The method showed broad tolerance to variations in the base molar ratio and precursor concentration and enabled isocratic HPLC purification. Conclusions: This one-step radiosynthesis overcomes longstanding challenges in [¹⁸F]fluproxadine production by eliminating harsh deprotection and enabling high-yield, automation-ready synthesis, thereby improving clinical feasibility. Full article

The synthesis, in particular the industrial production, of pharmaceuticals requires a broad arsenal of synthetic reactions capable of selectively forming specific structural motifs and assembling smaller building blocks into complex molecules. The Chan–Evans–Lam cross-coupling reaction, which forms a bond between a N-nucleophile and an aryl group from a boronic acid, catalysed by copper salts, is a typical example of this synthetic route. Considering the toxicity of copper and the stringent regulatory limits for its residues in final pharmaceutical products, a heterogeneous catalytic approach offers a viable alternative for this transformation. In this work, we present a simply and reproducibly synthesized catalyst based on copper nanoparticles supported on reduced graphene oxide (Cu-rGO), with high efficiency in a model Chan–Lam reaction involving benzimidazole and aniline derivatives with substituted boronic acids. Full article

This review examines the feasibility of electrochemical synthesis of poly-L-arginine (PArg) using repetitive cyclic voltammetry in neutral aqueous phosphate-buffered saline. Previous studies on electrochemical deposition of PArg onto different carbonaceous electrode materials are discussed with respect to the already reported mechanistic models. Some controversial interpretations are of interest, predominantly the formation of peptide bonds during the electropolymerisation of L-arginine. Several alternative anodic pathways are considered via the possibilities and limitations of ways of attaching L-arginine molecules to the electrode surface. Furthermore, the role of oxygen-containing surface groups is discussed, as this aspect has been largely overlooked in the context of L-arginine deposition, despite the O-terminating character of the electrode surface and its effect on the reactivity of the nucleophilic guanidine group in L-arginine. Also, the application of extremely high potentials around +2 V vs. Ag/AgCl/3 mol L⁻¹ KCl is considered, as it can lead to the generation of reactive oxygen species that may interfere with or even govern the entire deposition process. Thus, the absence of such considerations may raise doubts about the peptide nature of the electrochemically assisted polymerisation of this basic amino acid. Finally, it seems that the identity of the electrochemically synthesised PArg does not correspond to that of this polymer prepared by conventional methods, such as solid-phase peptide synthesis, solution-phase synthesis, or N-carboxy-anhydride polymerisation, and therefore the whole process remains unproved. Full article

The review critically discusses the methodological approach used to characterize the mechanism and to assess kinetic parameters in catalytic processes promoted by surfactant-based nanozymes. Using the hydrolysis of carboxylic and phosphoric esters as model reactions, it quantitatively analyzes several examples in which the catalytic system consists either of aggregates formed by non-functional surfactants or of surfactants bearing one or more reactive functions, ranging from classical nucleophiles to transition metal ions. This analysis highlights both the importance of the design of the kinetic experiments and of the selection of the appropriate experimental conditions, and the need to apply the correct model and set of kinetic equations in the interpretation of the data, in order to obtain kinetic parameters with true chemical significance. Improper kinetic modeling may lead to misleading rate enhancements and false claims of very high activity of the system studied. The aim of the review is not to provide a general overview of micelle and liposome-promoted catalysis, but rather to offer methodological tools to correctly assess rate accelerations with these systems. Full article

Silica-based sorbents covalently modified with polyhedral boron clusters represent a promising platform for highly selective separation materials, yet robust and synthetically accessible immobilization protocols remain underdeveloped. In this work, novel sorbents based on commercially available silica gels functionalized with closo-dodecaborate anions were synthesized and systematically characterized. Two immobilization strategies were compared: direct nucleophilic addition of surface aminopropyl groups to the nitrilium derivative (Bu₄N)[B₁₂H₁₁NCCH₃] and sol–gel condensation of a pre-formed boron-containing APTES-derived silane. Covalent attachment via amidine bond formation was confirmed by solution and MAS ¹¹B NMR spectroscopy, IR spectroscopy, elemental analysis/ICP-OES, and SEM. The direct grafting route afforded a boron loading of 4.5 wt% (≈20% of the theoretical capacity), with the efficiency limited by electrostatic repulsion between anionic amidine fragments on the negatively charged silica surface, whereas the APTES route gave lower absolute loading (0.085 mmol/g) due to the low specific surface area of the coarse silica support. Despite the moderate degree of functionalization, the resulting boron cluster–modified silica gels are attractive candidates for specialized chromatographic applications, where the unique hydrophobic and dihydrogen-bonding properties of closo-dodecaborates may enable selective retention of challenging analytes and motivate further optimization of surface morphology and immobilization conditions. Full article

Nucleophilic ring-opening of bis(oxiranes), containing several reactive centers, can be used to elaborate straightforward atom-economy and stereoselective approaches to polyfunctionalized compounds. In the present work, ring-opening of cis- and trans-diastereomers of a spirocyclic bis(oxirane), containing a cyclooctane core (namely, 1,8-dioxadispiro[2.3.2.3]dodecane), upon treatment with various amines, was studied. Trans-isomer afforded aminoalcohols with 9-oxabicyclo[3.3.1]nonane moiety, formed via domino-process, including opening of an oxirane ring followed by intramolecular cyclization. Ring-opening of cis-isomer gave aminosubstituted cis-cyclooctane-1,5-diols, derived from independent reaction of two oxirane moieties. Activation of oxirane rings by the addition of LiClO₄, acting as a Lewis acid, allowed the involvement of a number of primary and secondary aliphatic amines as well as aniline derivatives in the reaction. Scope and limitations of the reaction were studied and a series of aminoalcohols with a 9-oxabicyclo[3.3.1]nonane core and symmetric diaminodiols with a cyclooctane core were obtained. Full article

This work explores a novel and efficient synthetic approach to a new class of boron cluster derivatives via the nucleophilic addition of stabilized phosphorus ylides, Ph₃P=CHR² (R² = COOEt, CN), to a series of nitrilium salts of the closo-decaborate anion, [2-B₁₀H₉NCR¹]⁻ (R¹ = Me, Et, ⁿPr, ⁱPr, Ph). The reaction proceeds regio- and stereospecifically, affording a diverse range of iminoacyl phosphorane derivatives, [2-B₁₀H₉NH=C(R¹)C(PPh₃)R²]⁻, in high isolated yields (up to 95%). The obtained compounds (10 examples) were isolated as tetrabutylammonium or tetraphenylphosphonium salts and thoroughly characterized by multinuclear NMR (¹¹B, ¹H, ¹³C, ³¹P), high-resolution mass spectrometry, and single-crystal X-ray diffraction. The reaction feasibility was found to be strongly influenced by the steric hindrance of the R¹ group. Furthermore, the practical utility of these novel hybrids was demonstrated by employing the [2-B₁₀H₉NH=C(CH₃)C(COOC₂H₅)=PPh₃]⁻ anion as a highly effective membrane-active component in ion-selective electrodes. The developed tetraphenylphosphonium (TPP⁺) sensor exhibited a near-Nernstian response, a low detection limit of 3 × 10⁻⁸ M, and excellent selectivity over a range of common inorganic and organic cations, showcasing the potential of closo-borate-based ionophores in analytical chemistry. Full article

Toughening modification of epoxy resin (EP) matrices is important for advancing high-performance fiber-reinforced composites. A promising strategy involves the use of multi-component additive systems. However, synergistic effects in such additive systems are difficult to achieve for multidimensional performance optimization due to insufficient interfacial interactions and competing toughening mechanisms. Herein, a “hard–soft” biphasic synergistic toughening system was engineered for epoxy resin, composed of furan-ring-grafted polyhedral oligomeric silsesquioxane (FPOSS) and liquid polysulfide rubber. The hybrid toughening agent significantly enhanced the integrated performance of the epoxy system: Young’s modulus, tensile strength, and elongation at break increased by 13%, 56%, and 101%, respectively. These improvements are attributed to the formation of enriched molecular chain entanglement sites and optimized dispersion, facilitated by nucleophilic addition reactions between flexible rubber segments and rigid FPOSS units with the epoxy matrix. The marked enhancement in toughness primarily stems from the synergistic toughening mechanism involving “crazing pinning” and “crazing-shear band”. Concurrently, FPOSS incorporation effectively modulated the curing reaction kinetics, rendering the process more gradual while substantially elevating the glass transition temperature (T_g) of the cured system by 16.82 °C and endowing it with superior thermal degradation stability. This work provides a simple and unique strategy to leverage multi-scale mechanisms for the construction of epoxy-based composites with good toughness and strength, and enhanced heat resistance. Full article

Copolymers of polyphenylene sulfone and polyarylene ether nitrile were synthesized using nucleophilic polycondensation. 2,6-difluorobenzonitrile (DFBN), 4,4′-dihydroxybiphenyl, and 4,4′-dichlorodiphenyl sulfone were used as monomers. The structure of the obtained copolymers was confirmed by means of IR spectroscopy, and their solubility in various solvents was studied. Thermal properties were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis, as well as a set of basic mechanical properties. It was found that both thermal stability and glass transition temperature are virtually independent of the copolymer composition, while samples with a DFBN monomer content of more than 75% exhibit a melting peak in the region of 357 °C on the DSC curves, indicating an increase in the degree of crystallinity, accompanied by a deterioration in the solubility of these polymers. With increasing DFBN content, a uniform increase in elastic modulus is observed, and both bending and tensile strength increase significantly. However, the introduction of DFBN segments into the polyphenylene sulfone structure leads to a decrease in impact strength. Full article

Amino acid derivatives, such as β-keto esters and pyrrolones, were used as nucleophiles in organocatalyzed Michael additions to nitroalkene acceptors, while fatty acid derivatives acted as both nucleophiles (β-keto esters) and electrophiles (nitroalkene acceptors). Bifunctional noncovalent organocatalysts were employed as asymmetric organocatalysts. Twenty compounds—including fatty acid and amino acid derivatives, as well as fatty acid–amino acid conjugates—were prepared with enantioselectivities of up to 98% ee. All novel products were fully characterized. This research demonstrates the ease of assembling readily available fatty acid and amino acid building blocks under ambient conditions. Full article

Methylbutynol (MB) is a typical propargylic alcohol with both alkynyl and hydroxyl groups, featuring excellent modifiability and broad applications. Currently, it is produced through the reaction of alkaline metallic acetylides and acetone, requiring expensive raw material and harsh reaction conditions. Herein, a novel method was proposed by replacing the metallic acetylide with calcium carbide (CaC₂) as a low-cost industrial acetylide reagent. The effects of solvent, activator, and proton donor on the ball mill reaction, and the defoaming performance of the resultant MB and its oxidative coupling product (2,7-dimethyl-3,5-octadiyn-2,7-diol), were studied. Nucleophilic reactivity of CaC₂ with acetone can be regulated by the activating effect of the ball mill, an appropriate activator, and a proton donor. High yield of MB (~94%) was obtained under synergistic action of TBAF·3H₂O and acetylene, which represents a facile synthesis process of MB under mild conditions. MB exhibits good defoaming performance, and 2,7-dimethyl-3,5-octadiyn-2,7-diol is more promising, being an excellent non-ionic defoamer. The result is of great significance for exploring new chemical reactions of CaC₂ and its high-value utilizations. Full article

The interfacial polymerization of fluorine-containing polyarylates (F-PAR) represents an important synthetic route for advanced polymeric materials. This work presents a comprehensive mechanistic investigation through integrated kinetic analysis and macromolecular characterization. The polymerization for both F-PAR and its non-fluorinated analogue (M-PAR) follows a two-stage, second-order kinetic profile, with the F-PAR system exhibiting a lower initial rate constant. Kinetic modeling revealed a dynamic reaction locus, transitioning from the bulk organic phase to an indistinguishable regime. The fluorinated system exhibits distinct stage-dependent behavior: initial retardation due to fluorine-induced “nucleophilicity penalty” on bisphenol monomer followed by a kinetic crossover where the growth rate of F-PAR surpasses M-PAR through enhanced oligomer electrophilicity. The terminal stage reveals fundamental divergence, while flexible M-PAR chains sustain accelerated growth via efficient chain-chain coupling, rigid F-PAR chains reach a molecular weight plateau. The incorporation of fluorine enhances thermal stability and optical transparency due to the low polarizability of C-F bonds. This study provides a complete mechanistic roadmap of fluorine’s dynamic role in polymer architecture control. Full article

Phosphorus-modified poly(vinyl alcohol) (PVA) has recently gained increasing attention as a functional polymeric matrix suitable for gel-based systems, owing to its biocompatibility, film-forming ability, and capacity to develop semi-interpenetrating networks. In this work, PVA was chemically modified through the nucleophilic substitution of its hydroxyl groups with the chloride groups of phenyl dichlorophosphate, following a literature-reported method carried out in N,N-dimethylformamide (DMF) as reaction medium, resulting in phosphorus-containing PVA networks (PVA-OP3). Hybrid gel-like films were then prepared by incorporating titanium dioxide nanoparticles (TiO₂ NPs), known for their antimicrobial activity, low toxicity, and high stability. The resulting composites were structurally, morphologically, and thermally characterized using FTIR, SEM, and thermogravimetric analysis. The incorporation of TiO₂ NPs significantly improved the thermal stability, with T₅% increasing from 240 °C for neat PVA-OP3 to 288 °C for the optimal composite, increased the char residue from 4.5% for the neat polymer to 30.1% for PVA-OP3/TiO₂-4, and enhanced antimicrobial activity against both Gram-positive and Gram-negative bacteria. These findings demonstrate that PVA-OP3/TiO₂ hybrid films possess promising potential as advanced biomaterials for biomedical, protective, and environmental applications. Full article

This paper demonstrates the successful synthesis of novel hybrid heterogeneous catalysts for the sustainable conversion of CO₂ into cyclic organic carbonates (COCs). The nanocat-alysts have been fabricated by encapsulating pre-formed ultra-small gold nanostructures into a nascent zinc-coordination polymer (ZnCP) framework formed from two organic building blocks, 2,4-naphthalenedicarboxylic acid (1,4-NDC) and 5-amino-1H-tetrazole (5-Atz), which serves as a nitrogen-rich ligand. Applying the fabricated catalysts in the synthesis of COCs yields high yields (up to 97%) and high selectivity (up to 100%), with exceptionally high turnover frequencies (TOFs) (up to 408 h⁻¹). The catalytic process can be carried out under mild conditions (80 °C, 1.5 MPa CO₂) and without the use of solvents. Nitrogen-rich ligand molecules in the structure of ZnCPs enhance catalytic performance thanks to additional nucleophilic centres, which are effective in the epoxides’ ring-opening process. The hybrid catalysts with encapsulated gold nanostructures, which modify the liquid–gas interface between epoxide and CO₂, give significantly higher yields and TOFs for less active epoxides. The designed hybrid nanocatalysts exhibit superior stability under the studied reaction conditions and can be reused without loss of activity. The developed coordination polymers are constructed from green components, and green chemistry principles are applied to prepare these catalytic materials. Full article

The efficient generation of structurally diverse rare ginsenosides from abundant precursors remains a significant challenge. In this study, a heterogeneous catalyst, 12-tungstosilicic acid supported on mesoporous silica (HSiW@mSiO₂), was developed for the transformation of ginsenoside Re in aqueous ethanol solution. The reaction was conducted under mild conditions, and the products were systematically analyzed using high-performance liquid chromatography coupled with multistage tandem mass spectrometry and high-resolution mass spectrometry. A total of 24 transformation products were identified, arising from deglycosylation, epimerization, dehydration, cyclization, and nucleophilic addition reactions. Structural elucidation revealed the formation of deglycosylated, hydrated and dehydrated derivatives, C-20 epimers, and novel ethoxylated protopanaxatriol-type ginsenosides resulting from solvent incorporation at the C-24(25) or C-20 position. Product distribution varied with reaction parameters, including solvent composition, reaction time, temperature, and catalyst dosage. The synthesized HSiW@mSiO₂ catalyst could be readily recovered by centrifugation and reused for five consecutive cycles, with complete conversion of ginsenoside Re maintained in the first two runs and a gradual decline in conversion to approximately 50% by the fifth cycle. This work demonstrates the efficacy of solid acid catalysts in enabling the structural diversification of ginsenosides through solvent-involved pathways. Full article