Reactions

The regioselectivity of the Claisen rearrangement with different meta-substituted and meta- and para-substituted allyl phenyl ethers was investigated. The main results were that in meta-substituted Claisen rearrangements the regioselectivity depends roughly on the electronic nature of the substituent, with electron-donating groups favoring migration further from the meta-substituent while electron-withdrawing groups favor migration towards the meta-substituent. Different para-substituents were tested with two meta-substituents, Me, and Cl. Most of the para-substituent tested had a clear effect on the product ratio, in all but one case enhancing the proportion of the major product favored by the meta-substituent. Population analysis was performed with Mulliken, Löwdin, Hirshfeld, and natural population analysis to analyze the influence of the substituents on the atomic charges on the reaction sites. It was observed that the atomic charge on the carbon that forms the major isomer is of higher negativity than the atomic charge on the carbon that forms the minor isomer. Full article

Fungal laccases are promising oxidative enzymes for bioremediation applications, particularly in the degradation of synthetic dyes present in industrial effluents. Here, we evaluated the inhibitory effects of sodium chloride (NaCl) and sodium sulfate (Na₂SO₄) on the activity of Trametes versicolor laccase and its ability to decolorize Congo Red (CR), Malachite Green (MG), and Remazol Brilliant Blue R (RBBR). Enzyme assays revealed concentration-dependent inhibition, with IC₅₀ values of 0.22 ± 0.04 M for NaCl and 1.00 ± 0.09 M for Na₂SO₄, indicating stronger inhibition by chloride. Kinetic modeling showed mixed-type inhibition for both salts. Despite this effect, the enzyme maintained significant activity: after 12 h, decolorization efficiencies reached 95 ± 4.0% for MG, 88 ± 3.0% for RBBR, and 75 ± 3.0% for CR, even in the presence of 0.5 M salts. When applied to a mixture of the three dyes, decolorization decreased only slightly in saline medium (94.04 ± 4.0% to 83.43 ± 5.1%). FTIR spectra revealed minor structural changes, but toxicity assays confirmed marked detoxification, with radicle length in lettuce seeds increasing from 20–38 mm (untreated dyes) to 41–48 mm after enzymatic treatment. Fungal growth assays corroborated reduced toxicity of treated dyes. These findings demonstrate that T. versicolor laccase retains functional robustness under ionic stress, supporting its potential application in saline textile wastewater remediation. Full article

With their considerable capacity and structurally favorable characteristics, layered transition metal oxides have become strong contenders for cathode use in sodium-ion batteries (SIBs). Nevertheless, their practical deployment is challenged by pronounced capacity loss, predominantly induced by unstable cathode–electrolyte interphase (CEI) at elevated voltages. In this study, difluoroethylene carbonate (DFEC) is introduced as a functional electrolyte additive to engineer a robust and uniform CEI. The fluorine-enriched CEI effectively suppresses parasitic reactions, mitigates continuous electrolyte decomposition, and facilitates stable Na⁺ transport. Consequently, Na/NaNi_1/3Fe_1/3Mn_1/3O₂ (Na/NFM) cells with 2 wt.% DFEC retain 78.36% of their initial capacity after 200 cycles at 1 C and 4.2 V, demonstrating excellent long-term stability. Density functional theory (DFT) calculations confirm the higher oxidative stability of DFEC compared to conventional solvents, further supporting its interfacial protection role. This work offers valuable insights into electrolyte additive design for high-voltage SIBs and provides a practical route to significantly improve long-term electrochemical performance. Full article

The coordination chemistry of benzimidazole ligands combines σ donation and π backbonding. Owing to this electronic flexibility, benzimidazole ligands stabilize both electron deficient and electron-rich transition states in the catalytic cycle of Ziegler-Natta polymerizations. In this study, Fe(III) and Ni(II) complexes of 2-substituted-benzimidazoles were tested as catalysts for ethylene and 1-butene oligomerization. The tests realized in toluene yielded mainly butenes and minor amounts of hexenes. When dichloromethane was used as solvent, a tandem reaction took place and 1-butene produced by ethylene dimerization was further oligomerized, yielding octenes and dodecenes as main products. All tested catalysts exhibited moderate selectivity for 1-octene, indicating 1-ω enchainment in 1-butene dimerization. Beyond catalytic tests, a theoretical study of the ligand 2,2′-(furan-2,5-diyl)bis(1H-benzimidazole) confirmed the planar structure of this compound as evidenced by NMR spectroscopy. Full article

The growing accumulation of waste lubricating oil presents serious environmental issues, calling for sustainable management solutions. This research discusses the creation of FeNi/TiO₂ nanocatalysts that were synthesized through an eco-friendly method utilizing grape seed extract (GSE) as a natural reducing agent for the catalytic pyrolysis of waste lubricating oil. The nanocatalyst was produced using the microemulsion technique and refined via Response Surface Methodology (RSM) to optimize its catalytic performance. Pyrolysis was carried out at 400 °C, leading to a significant conversion of waste oil into valuable fuel. The FeNi/TiO₂ nanocatalyst exhibited exceptional capabilities in facilitating the breakdown of heavy hydrocarbons into lighter fuel fractions while reducing unwanted byproducts. GC-MS analysis demonstrated the prevalence of C6–C20 hydrocarbons in the pyrolysis oil, underscoring its potential as a high-quality alternative fuel similar to traditional diesel. This study aids in the progress of environmentally sustainable waste-to-energy technologies, offering a promising pathway for effective fuel production and hazardous waste management. Full article

Nerol ((Z)-3,7-dimethylocta-2,6-dien-1-ol), (C₁₀H₁₈O), is a monoterpene alcohol that belongs to the family of BVOCs emitted naturally by means of vegetation and is found in various medicinal plants. This species attracted attention in the field of atmospheric chemistry due to its unique structural, chemical and environmental properties. In this work, OH-addition and H-abstraction reactions of Nerol by OH radical have been investigated using M06-2X, CBS-QB3 and CCSD(T) with 6-311++G(d,p) basis set. The OH addition at the C=C double bond of Nerol was shown to be the most favorable, with a small relative energy barrier of −6.86 kcal/mol and H-abstraction at the CH₂ group exhibits a relative energy barrier of 0.08 kcal/mol at CCSD(T)/6-311++G(d,p) level of theory. The obtained overall rate coefficient at 298 K is 9.68 × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹ using canonical variational transition state theory with small curvature tunnelling method (CVT/SCT), which is in good agreement with the experimental rate coefficient determined by Mahecha et al. (k_OH = (1.60 ± 0.2) × 10⁻¹⁰) at 296 ± 2 K. The obtained rate coefficient exhibits negative temperature dependence, and the atmospheric lifetime of Nerol is about 18 min. The predicted oxidation pathways reveal the formation of key products such as formaldehyde, glycolaldehyde and 6-Methyl-hept-5-en-2-ol, which is also observed in previous experimental studies, indicating good agreement between theoretical and experimental findings. This study constitutes the first theoretical study and its dependence on temperature exploration, offering detailed insights into the degradation pathways and environmental impact of Nerol initiated by hydroxyl radicals. Full article

Two new long-chain N-alkyl imidazole derivatives, 2-(1-octadecyl-imidazol-2-yl)pyridine and 2-(furan-2-yl)-1-(octadecane-1-yl)-1H-imidazole, were synthesized via the Radziszewski reaction followed by N-alkylation. This is the first report of furan-imidazole obtained by this route using furfuraldehyde as a renewable biomass-derived precursor. FTIR, 1D/2D solution NMR, and HRMS confirmed the structural elucidation, while XRD and solid-state ¹³C CPMAS NMR corroborated the crystal structures of the precursors. Notably, previously misassigned ¹H and ¹³C chemical shifts reported in the literature for pyridine and furan-imidazole precursors were corrected. Furthermore, ¹³C CPMAS NMR spectra of those precursors are reported here for the first time. These findings expand the scope of the Radziszewski reaction and provide new insights into the structural characterization of imidazole-based systems. Full article

Strategic scaffolds in molecules increase the possibility of obtaining derivatives with potential uses in scientific and industrial areas. The regio- and stereoselective reactions can be considered to gain these tactical motifs. Natural diterpenes are key molecules for reaching such aims. Among this class of compounds, neo-clerodanes are highlighted by the presence of a furan moiety in their chemical structure. This work describes a regio- and stereoselective strategy to gain beta-lactone and oxirane derivatives from kerlinic acid (1) when the β,γ-unsaturated carboxylic acid system is oxidized, preserving the furan moiety. Oxidation of 1 yielded salviaolide (2), suggesting regio- and stereoselective means. A reaction mechanism was proposed when oxidation of the acetate (1a), benzoate (1b), and methyl ester (1c) derivatives from 1 were gained. The obtention of the epoxide derivative 3, kernolide (4), and kernolide epoxide (5) also supported the reaction mechanism. X-ray diffraction analysis of 3, Karplus-type analyses, and DFT calculations from hypothetical intermediates revealed conformational preferences that guide the regioselectivity. The stereoselectivity was attributed to the natural origin of 1. All compounds were characterized by their physical and spectroscopical data. These results suggest the feasibility of promoting regioselective oxidation on neo-clerodane compounds, preserving the furan moiety. Full article

The NAD⁺-dependent alcohol dehydrogenase AdhB from Aromatoleum aromaticum EbN1 belongs to family III of Fe-dependent alcohol dehydrogenases. It was recombinantly produced in Escherichia coli and biochemically characterized, showing activity only with ethanol or n-propanol. The enzyme contained substoichiometric amounts of Fe, Zn, and Ni and a yet unidentified nucleotide-like cofactor, as indicated by mass spectrometric data. As suggested by its narrow substrate spectrum and complementation of a related species to growth on ethanol, the most probable physiological function of AdhB is the oxidation of short aliphatic alcohols such as ethanol or n-propanol. The enzyme also exhibits a very high tolerance to ethanol and n-propanol, showing moderately substrate-inhibited Michaelis–Menten kinetics up to concentrations of 20% (v/v). AdhB can also be applied biotechnologically to convert acetate to ethanol in coupled enzyme assays with the tungsten enzyme aldehyde oxidoreductase, showing activity with either another aldehyde or pre-reduced benzyl viologen as electron donors. Full article

Carbon dioxide is naturally present in the Earth’s atmosphere and plays a role in regulating and balancing the planet’s temperature. However, due to various human activities, the amount of carbon dioxide is increasing beyond safe limits, disrupting the Earth’s natural temperature regulation system. Today, CO₂ is the most prevalent greenhouse gas; as its concentration rises, significant climate change occurs. Therefore, there is a need to utilize anthropogenically released carbon dioxide in valuable fuels, such as formic acid (HCOOH). Single-atom catalysts are widely used, where a single metal atom is anchored on a surface to catalyze chemical reactions. In this study, we investigated the potential of Cu@Phosphorene as a single-atom catalyst (SAC) for CO₂ reduction using quantum chemical calculations. All computations for Cu@Phosphorene were performed using density functional theory (DFT). Mechanistic studies were conducted for both bimolecular and termolecular pathways. The bimolecular mechanism involves one CO₂ and one H₂ molecule adsorbing on the surface, while the termolecular mechanism involves two CO₂ molecules adsorbing first, followed by H₂. Results indicate that the termolecular mechanism is preferred for formic acid formation due to its lower activation energy. Further analysis included charge transfer assessment via NBO, and interactions between the substrate, phosphorene, and the Cu atom were confirmed using quantum theory of atoms in molecules (QTAIM) and non-covalent interactions (NCI) analysis. Ab initio molecular dynamics (AIMD) calculations examined the temperature stability of the catalytic complex. Overall, Cu@Phosphorene appears to be an effective catalyst for converting CO₂ to formic acid and remains stable at higher temperatures, supporting efforts to mitigate climate change. Full article

The nitrogen electroreduction reaction (NRR) has emerged as a promising and sustainable alternative to the Haber–Bosch process for NH₃ production. This study investigated the NRR in alkaline medium using Pd/C, Rh/C, and PdRh/C electrocatalysts, employing online electrochemical mass spectrometry (OLEMS) for gaseous-product detection and ultraviolet–visible spectroscopy to confirm NH₃ formation. To our knowledge, no previous reports have simultaneously detected H₂, N₂H, and N₂H₂ intermediates and monitored N₂ consumption as a function of applied potential for Pd and Rh catalysts. The bimetallic PdRh/C catalyst showed superior NRR performance compared with the monometallic catalysts, exhibiting higher faradaic charges, more pronounced generation of nitrogen intermediates, and selectivity for NH₃. This work provides key insights into the NRR mechanisms and underlines the strategic importance of the bimetallic catalyst design for more efficient, sustainable electrochemical NH₃ synthesis. Full article

A new series of 6-arylaminoflavones was synthesized via the Buchwald–Hartwig cross-coupling reaction, aiming to functionalize the flavone core efficiently. Reaction optimization revealed that Pd₂(dba)₃/XantPhos with Cs₂CO₃ in toluene provided the best yields, with isolated yields ranging from 8% to 95%, depending on the arylamine structure. Steric hindrance and electron-withdrawing groups at the arylamine ring impacted the reaction outcomes. Cytotoxicity assays in different human cancer cell lines indicated that substitution patterns at both the arylamine and B-rings strongly impacted biological activity. In particular, compounds bearing a 3,4-dimethoxy substitution at the B-ring and a trifluoromethyl (13c) or chlorine (13g) group at the aniline moiety exhibited enhanced cytotoxicity. These findings provide insights into the structure–activity relationship of 6-arylaminoflavones while contributing to the development of synthetic methodologies for functionalized flavones. Full article

Polycyclic aromatic compounds can often be made by a sequence featuring an initial Diels–Alder [4 + 2] cycloaddition reaction, followed by cheletropic extrusion of carbon monoxide. These reactions normally require heating the diene and dieneophile in petrochemical-derived aromatic hydrocarbon solvents, such as xylenes or diphenyl ether. This article summarizes the results of attempts to use renewable solvents in place of those currently in use to prepare pentaphenylbenzene and 1,2,4-triphenyltriphenylene. Dihydrolevoglucosenone, p-cymene, ethyl lactate, diethyl carbonate, and cyclopentyl methyl ether have all been successfully evaluated as renewable solvent alternatives in Diels–Alder/cheletropic reaction sequences. An analysis of the products from the reactions investigated did not show evidence of oxidative degradation of the diene reactants. Furthermore, norbornadien-7-one intermediates were not isolated from any of the reactions tested. Full article

Aluminothermic reduction is an alternative processing route for the circular economy because Al is produced electrochemically in the Hall–Héroult process with minimal CO₂ emissions if the electricity input is sourced from non-fossil fuel energy sources. This circular processing option attracts increased research attention in the aluminothermic production of manganese and silicon alloys. The Al₂O₃ product must be recycled through hydrometallurgical processing, with leaching as the first step. Recent work has shown that the NaAlO₂ compound is easily leached in water. In this work, a suitable slag formulation is applied in the aluminothermic reduction of manganese ore to form a Na₂O-based slag of high Al₂O₃ solubility to effect good alloy–slag separation. The synergistic effect of carbon and silicon reductants with aluminium is illustrated and compared to the test result with only carbon reductant. The addition of small amounts of carbon reductant to MnO₂-containing ore ensures rapid pre-reduction to MnO, facilitating aluminothermic reduction. At 1350 °C, a loosely sintered mass formed when carbon was added alone. The alloy and slag chemical analyses are compared to the thermochemistry predicted phase chemistry. The alloy consists of 66% Mn, 22–28% Fe, 2–9% Si, 0.4–1.4% Al, and 2.2–3.5% C. The higher %Si alloy is formed by adding Si metal. Although the product slag has a higher Al₂O₃ content (52–55% Al₂O₃) compared to the target slag (39% Al₂O₃), the fluidity of the slags appears sufficient for good alloy separation. Full article

Dye-sensitized solar cells (DSSCs) have emerged as a promising technology for converting sunlight into electricity at a low cost; however, it is still necessary to find a photostable, low-cost, and efficient photosensitizer. In this sense, the natural product bixin (Dye 1) has previously been reported as a potential photosensitizer. Thus, the present work reports the full synthesis of diester and diacid hybrids (Dyes 2 and 3, respectively, with corresponding yields of 93% and 52%) using the natural product bixin as a starting material and 1,3,4-oxadiazole ring as a connected point. The hydrolysis step of Dye 2 aims to obtain Dye 3 with a structural capacity to anchor the titanium dioxide (TiO₂) nanofilms via the carboxylic acid group. Both compounds (Dyes 1 and 3) can be adsorbed via pseudo-first order on the surface of TiO₂ nanofilms, reaching saturation after 10 and 6 min of exposure in an organic solution (1 × 10⁻⁵ M), respectively, with adsorption kinetics of the semisynthetic compound almost twofold higher than the natural product. Contrary to expectations, Dye 3 had spectral behavior similar to Dye 1, but with better frontier molecular orbital (FMO) parameters, indicating that Dye 3 will probably behave very similarly or have slightly better photovoltaic performance than Dye 1 in future DSSC measurements. Full article

The disposal of wastewater resulting from petroleum industries presents a major environmental challenge due to the presence of hard-to-degrade organic pollutants, such as oils and hydrocarbons, and high chemical oxygen demand (COD). In this study, an efficient and eco-friendly method was developed to treat such wastewater using a photocatalyst composed of biochar derived from pistachio shells and loaded with zinc oxide (ZnO) nanoparticles. The biochar-ZnO composite was prepared via a co-precipitation-assisted pyrolysis method to evaluate its efficiency in the photocatalytic degradation of petroleum wastewater (PW). The synthesized material was characterized using various techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy, to determine surface morphology, crystal structure, and functional groups present on the catalyst surface. Photocatalytic degradation experiments were conducted under UV and sunlight for 90 h of irradiation to evaluate the performance of the proposed system in removing oil and reducing COD levels. Key operational parameters, such as pH (2–10), catalyst dosage (0–0.1) g/50 mL, and oil and COD concentrations (50–500) ppm and (125–1252) ppm, were optimized by response surface methodology (RSM) to obtain the maximum oil and COD removal efficiency. The oil and COD were removed from PW (90.20% and 88.80%) at 0.1 g/50 mL of PS/ZnO, a pH of 2, and 50 ppm oil concentration (125 ppm of COD concentration) under UV light. The results show that pollutant removal is slightly better when using sunlight (80.00% oil removal, 78.28% COD removal) than when using four lamps of UV light (77.50% oil removal, 75.52% COD removal) at 0.055 g/50 mL of PS/ZnO, a pH of 6.8, and 100 ppm of oil concentration (290 ppm of COD concentration). The degradation rates of the PS/ZnO supported a pseudo-first-order kinetic model with R² values of 0.9960 and 0.9922 for oil and COD. This work indicates the potential use of agricultural waste, such as pistachio shells, as a sustainable source for producing effective catalysts for industrial wastewater treatment, opening broad prospects in the field of green and nanotechnology-based environmental solutions in the development of eco-friendly and effective wastewater treatment technologies under solar light. Full article

A new synthetic route of Epalrestat was proposed in this study. The new route abandons the raw material carbon disulfide, which is highly harmful to the environment, and optimizes the key steps in the typical synthesis strategy. Epalrestat was prepared through a three-step process, and the reaction products were characterized. The optimum conditions for the synthesis of the substituted rhodanine intermediate are as follows: under the catalysis of 2.0 equivalents of 25%KOH, ethanol was used as the solvent, and the reaction was carried out at 40 °C for 1 h. The optimal conditions for the synthesis of Epalrestat are as follows: under the catalysis of 2.0 equivalents of 50%KOH, ethanol was used as the solvent, and the reaction was carried out at 40 °C for 5 h. Full article

1,3-Dipolar cycloadditions on nitrone dipoles are key reactions to access five-membered heterocycles, which are useful intermediates in the synthesis of biologically relevant glycomimetics. The good atomic balance and high stereoselectivity characteristic of such reactions make them good candidates for the development of green protocols. In the present work, these features were maximized by avoiding the use of organic solvents and considering starting materials derived from biomass. Reactions involving (acyclic and cyclic) carbohydrate-derived nitrones as dipoles and levoglucosenone as dipolarophile were considered. Performing selected 1,3-dipolar cycloadditions in neat conditions showed reduced reaction times, maintaining similar selectivity and yields with respect to the classical protocols. The use of microwave irradiation and orbital shaking were also exploited to increase the sustainability of the synthetic protocols. The collected results highlight the potential of solvent-free 1,3-dipolar cycloadditions in the design of efficient synthetic routes according to green chemistry principles, such as prevention, atom economy, safer solvents and auxiliaries, and use of renewable feedstocks. Full article