Search Results (268)

In the field of green chemistry, the development of more sustainable and cost-efficient methods for synthesizing primary amines is of paramount importance, with catalyst research being central to this effort. This work presents a facile, aqueous-phase synthesis of highly active cobalt catalysts (Co-Ph@SiO₂(x)) via pyrolysis of silica-supported cobalt–phenanthroline complexes. The optimized Co-Ph@SiO₂(900) catalyst achieved exceptional performance (>99% conversion, >98% selectivity) in the reductive amination of acetophenone to 1-phenylethanamine using NH₃/H₂. Systematic studies revealed that its exceptional performance originates from the in situ pyrolysis of the cobalt–phyllosilicate complex. This process promotes the uniform distribution of metal cobalt nanoparticles, simultaneously enhancing porosity and imparting bifunctional (acidic and basic) properties to the catalyst, resulting in outstanding catalytic activity and selectivity. The catalyst demonstrated broad applicability, efficiently converting diverse ketones (aryl-alkyl, dialkyl, bioactive) and aldehydes (halogenated, heterocyclic, biomass-derived) into primary amines with high yields (up to 99%) and chemoselectivity (>40 examples). This sustainable, non-noble metal-based catalyst system offers significant potential for industrial primary amine synthesis and provides a versatile tool for developing highly selective and active heterogeneous catalysts. Full article

Bis- and trisphosphines incorporating methylene and aryl spacers readily adsorb on the surface of porous activated carbon (AC). The adsorption can be performed in the absence of solvents, even when the phosphines have high melting points, or from solutions. The diverse phosphines Ph₂PCH₂PPh₂ (dppm), Ph₂P(CH₂)₂PPh₂ (dppe), Ph₂P(CH₂)₃PPh₂ (dppp), Ph₂P(p-C₆H₄)PPh₂ (dppbz), and (Ph₂PCH₂)₃CCH₃ (tdme) were adsorbed in submonolayers on AC. The adsorbed phosphines were studied by ³¹P MAS (magic angle spinning) NMR spectroscopy, and their mobilities on the surface were confirmed by determining the ³¹P T₁ relaxation times. All phosphine groups of each bis- and trisphosphine molecule are in contact with the surface, and the molecules exhibit translational mobility as one unit. All phosphines used here are air-stable. Once a submonolayer is created on the AC surface, oxygen from the air is co-adsorbed and transforms all phosphines quantitatively into phosphine oxides at room temperature. The oxidation proceeds in a consecutive manner with the oxidation of one phosphine group after another until the fully oxidized species are formed. Studies of the kinetics are based on integrating the signals in the solution ³¹P NMR spectra. High temperatures and low surface coverages increase the speed of the oxidation, while light and acid have no impact. The oxidation is fast and complete within one hour for 10% surface coverage at room temperature. In order to study the mechanism and slow down the oxidation, a higher surface coverage of 40% was applied. No unwanted P(V) side products or water adducts were observed. The clean phosphine oxides could be recovered in high yields by washing them off of the AC surface. The oxidation is based on radical activation of O₂ on the AC surface due to delocalized electrons on the AC surface. This is corroborated by the result that AIBN-derived radicals enable the air oxidation of PPh₃ in solution at 65 °C. When the air-stable complex (CO)₂Ni(PPh₃)₂ is applied to the AC surface and exposed to the air, OPPh₃ forms quantitatively. The new surface-assisted air oxidation of phosphines adsorbed on AC renders expensive and hazardous oxidizers obsolete and opens a synthetic pathway to the selective mono-oxidation of bis- and trisphosphines. Full article

Endothelial cells play a crucial role in cardiovascular health by maintaining vascular homeostasis, regulating blood flow and vascular wall permeability, and protecting against external stressors. Oxidative stress, particularly excessive reactive oxygen species (ROS), disrupts cellular homeostasis and contributes to endothelial cell dysfunction. Rutaecarpine (RUT), an indolopyridoquinazolinone alkaloid isolated from Evodia rutaecarpa, has cytoprotective potential. However, the molecular mechanism underlying its cytoprotective activity in endothelial cells remains unclear. In this study, we investigated the protective effects of RUT against H₂O₂-induced apoptosis in human EA.hy926 endothelial cells and explored its underlying mechanism of action. RUT enhanced nuclear factor erythroid 2-related factor 2 (Nrf2) activation by increasing its expression and phosphorylation, resulting in the upregulation of antioxidant enzymes (GCLC, NQO1, and HO-1). RUT increased the level of the anti-apoptotic marker (Bcl-2) while inhibiting apoptotic markers (cleaved caspase-3 and Bax) in H₂O₂-induced apoptotic cells. Mechanistic analysis revealed that RUT activates Nrf2 through two pathways: TRPV1-mediated PKCδ/Akt phosphorylation and aryl hydrocarbon receptor (AhR)-dependent Nrf2 expression. These findings suggest that RUT exerts protective effects against oxidative-stress-induced apoptosis by controlling the Nrf2 signaling pathway in endothelial cells. Full article

Background/Objectives: Metabolic dysfunction-associated fatty liver disease (MAFLD) is a chronic hepatic condition marked by lipid buildup, lipotoxicity, and inflammation. Prior research indicates that 3,3′-Diindolemethane (DIM), a natural indole-type phytochemical that is abundant in brassicaceae vegetables, has been reported to reduce body weight and improve lipid metabolism in mice subjected to a high-fat diet (HFD). The aryl hydrocarbon receptor (AhR), a nuclear receptor implicated in lipid metabolism and immune regulation, serves as a functional receptor for DIM. However, the underlying signaling pathways that regulate MAFLD remain elusive. Our objective is to ascertain the beneficial impact of DIM on MAFLD and the associated mechanisms. Methods: Hematoxylin and eosin staining, together with Oil Red O staining, were utilized to assess the pathological changes and lipid deposition in the liver. Biochemical analysis was employed to measure levels of triglyceride (TG), total cholesterol (TC), free fatty acid (FFA), aspartate transaminase (AST), alanine transaminase (ALT), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C). The cell survival rate of HepG2 cells treated with palmitic acid (PA) and DIM was assessed using the CCK-8 assay. Flow cytometry was employed to measure the fluorescence intensity emitted by lipid droplets within cells. Western blotting analysis was performed to assess AhR pathway and fatty acid transporter expression levels in hepatic tissue. Results: Our results showed that DIM significantly attenuated body weight gain and hepatic injury brought on by HFD, decreased lipid droplet accumulation in HepG2 cells, and effectively suppressed the phosphorylation of p38 MAPK and the protein expression levels of fatty acid transporters CD36 and FATP4. Conclusions: DIM reduced lipid accumulation by activating AhR and suppressing p38 MAPK phosphorylation, thereby inhibiting fatty acid transport and inflammatory responses. These findings suggest that DIM may represent a promising therapeutic candidate for MAFLD, warranting further exploration for clinical applications. Full article

The search for new heterocyclic compounds with biological potential is one of the current challenges in modern chemistry. Therefore, the comprehensive study of (3 + 2) cycloaddition (32CA) reactions between a series of aryl-substituted nitrile N-oxides (NOs) and (E)-3,3,3-tribromo-1-nitroprop-1-ene (TBNP) is carried out. According to the experimental research, in all tested 32CAs, the proper (4RS,5RS)-3-aryl-4-nitro-5-tribromomethyl-2-isoxazolines are obtained as only one reaction product. In turn, the quantum–chemical MEDT study shows that the creation of heterocycles occur via the polar attack of zwitterionic moderate-nucleophilic NOs to strong electrophilic TBNP. The reactions are realized according to a two-stage, one-step asynchronous mechanism, in which the formation of the O-C(CBr₃) bond takes place once the C-C(NO₂) bond is already formed. What is more, the computational analysis confirmed the experimental results. At the end, the obtained 2-isoxazolines were docked to three proteins: gelatinase B, cyclooxygenase COX-1, and Caspase-7. We hope that the presented study will be helpful for searching for the future direction of application for this class of organic compounds. Full article

Herein we describe the development of the first model amphiphilic polymer conetwork (APCN) comprising a short hydrophobic hexa(L-alanine) segment being the outer block of an amphiphilic four-armed star block copolymer with inner poly(ethylene glycol) (PEG) blocks bearing benzaldehyde terminal groups and end-linked with another four-armed star PEG homopolymer (tetraPEG star) bearing aryl-substituted acylhydrazide terminal groups. The present successful synthesis that yielded the peptide-containing model APCN was preceded by several unsuccessful efforts that followed different synthetic strategies. In addition to the synthetic work, we also present the structural characterization of the peptide-bearing APCN in D₂O using small-angle neutron scattering (SANS). Full article

Organosulfur compounds are appealing owing to the diverse oxidation states accessible by sulfur, allowing the precise adjustment of their properties. In this study, we report a practical oxidation method that converts sulfides to sulfones by generating chlorine dioxide in situ from sodium chlorite (NaClO₂) and hydrochloric acid (HCl) in organic solvents. Diphenyl sulfide was effectively oxidized to diphenyl sulfone in yields of up to 96% under optimized conditions, with high selectivity in ethyl acetate and acetonitrile solvents. The method is compatible with a wide range of substrates, including various aryl, benzyl, and alkyl sulfides, although reactivity diminishes with sterically hindered or electron-rich substrates. This scalable and environmentally friendly process overcomes challenges associated with aqueous oxidants, such as substrate solubility and side reactions, providing a robust alternative for sulfone synthesis. Full article

Herein, we report the first mechanochemical strategy for the Ru-catalyzed deoxygenative borylation of free phenols via C–O bond cleavage. This Ru-catalyzed phenolic borylation approach has been successfully extended to the Suzuki–Miyaura-type cross-coupling of phenols with aryl bromides. The protocol accepts a wide scope of phenolic substrates, allowing the synthesis of aryl pinacolboranes and biphenyl structures in excellent yields and serving as a better alternative to classical cross-coupling reactions in the context of pot, atom, and step economy synthesis. Full article

An aldol condensation reaction between [2-(O=CH)C₆H₄]SnPh₂Cl and acetone gave [2-{CH₃C(=O)CH₂(OH)CH}C₆H₄]SnPh₂Cl (1). The compound was characterized in a solution using multinuclear NMR spectroscopy and HR-MS spectrometry and in a solid state using IR spectroscopy and single-crystal X-ray diffraction. The molecular structure revealed the presence of both enantiomers in the crystal. Full article

Chelation-assisted olefinic C–H functionalization has been demonstrated to be a powerful method of constructing multi-substituted alkenes from simpler ones. This strategy produces complex alkenes in a regio- and stereoselective manner, followed by C–H endo- and exo-cyclometallation. Among the various directing groups developed, N,N- and N,O-bidentate directing groups are the most widely used to selectively promote C–H functionalization due to their fine, tunable, and reversible coordination with the metal center. In this review, we discuss various N,N- and N,O-bidentate directing group-assisted olefinic C–H bond functionalization reactions, including alkenylation, alkylation, arylation, thiolation, silylation, halogenation, and cyclization. Full article

Agricultural land abandonment is a widespread phenomenon found in many regions of the world. There are many studies on post-agricultural changes in temperate, arid, semi-arid regions, etc., but studies of such soils in boreal or Arctic conditions are rare. Our study aims to fill the gaps in research on the processes of post-agricultural soil transformation, with a focus on the harsh climatic conditions of the Arctic and Subarctic regions. Parameters of soil organic matter (SOM) are largely reflected in the quality of soil, and this study investigates the dynamics of SOM properties in Subarctic agricultural soils in process of post-agrogenic transformation and long-term fertilization. Using a chronosequence approach (0–25 years of abandonment) and a reference site with over 90 years of fertilization, we performed elemental (CHN-O) analysis, solid-state ¹³C NMR spectroscopy of SOM, PXRD of soil and parent material, and multivariate statistical analysis to identify the connections between SOM composition and other soil properties. The results revealed transient increases in soil organic carbon (SOC) during early abandonment (5–10 years; 3.75–4.03%), followed by significant declines after 25 years (2.15–2.27%), driven by mineralization in quartz-dominated soils lacking reactive minerals for organo-mineral stabilization. The reference site (the Yamal Agricultural Station) maintained stable SOC (3.58–3.83%) through long-term organic inputs, compensating for poor mineralogical protection. ¹³C NMR spectroscopy highlighted shifts from labile alkyl-C (40.88% in active fields) to oxidized O-alkyl-C (21.6% in late abandonment) and lignin-derived aryl-C (15.88% at middle abandonment), reflecting microbial processing and humification. Freeze–thaw cycles and quartz dominance mineralogy exacerbated SOM vulnerability, while fertilization sustained alkyl-C (39.61%) and balanced C:N (19–20) ratios. Principal Component Analysis linked SOC loss to declining nutrient retention and showed SOM to be reliant on physical occlusion and biochemical recalcitrance, both vulnerable to Subarctic freeze–thaw cycles that disrupt aggregates. These findings underscore the fragility of SOM in Subarctic agroecosystems, emphasizing the necessity of organic amendments to counteract limitations of poor mineralogical composition and climatic stress. Full article

An efficient access to novel 2-substituted 1H-imidazole derivatives was developed based on acid-mediated denitrogenative transformation of 5-amino-1,2,3-triazole derivatives available through dipolar azide−nitrile cycloaddition (DCR). The proposed approach includes intramolecular cyclization of 5-amino-4-aryl-1-(2,2-diethoxyethyl) 1,2,3-triazoles followed by triazole ring opening and insertion of in situ formed carbene intermediate into the O-H bond of different alcohols under acidic conditions. Full article

The so far unattended version of the Hirao reaction involving the coupling of the less reactive chloroarenes with >P(O)H reagents, such as diarylphosphine oxides, diethyl phosphite, and ethyl phenyl-H-phosphinate, was investigated in detail using Pd(OAc)₂ as the catalyst precursor, and applying some excess of the P-reagent to provide the ligand via its trivalent tautomeric (>P-OH) form. In the presence of triethylamine, no P–C coupling took place, meaning that there was a need for a stronger base, an alkali carbonate. The solvent had a significant effect on the efficiency of the Hirao reaction. The optimum conditions (10% of the Pd(OAc)₂, 1.3 equiv. of the P-reagent, 1.1 equiv. of the alkali carbonate, 135–150 °C) explored herein were applied in the synthesis of diaryl-phenylphosphine oxides, aryl-diphenylphosphine oxides, diethyl arylphosphonates, and ethyl diphenylphosphinate. Theoretical calculations performed at the M06-2X/6-31G(d,p)[PCM(MeCN)] level also justified coupling with the chloroarenes under appropriate conditions, and were in accord with the experimental results revealing the unsuitability of triethylamine as a base and the need for an alkali carbonate. The new protocol elaborated herein is more practical and “greener” than the version with bromoarenes, and embraces a wide substrate scope. 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

Orthopalladated derivatives from substituted phenylglycines [Pd(μ-Cl)(C₆H₃R₁C(R₂)(R₃)N(R₄)₂]₂ (1) react with halogenating reagents (PhICl₂, Br₂, I₂) (2) to give the corresponding o-halogenated amino acids C₆H₃(X)R₁C(R₂)(R₃)N(R₄)₂ (3). The reaction is general and tolerates a variety of functional groups (R₁ to R₄) at the aryl ring, the Cα, and the N atom. On the other hand, the reaction of [Pd(μ-Cl)(C₆H₃R₁C(R₂)(R₃)N(R₄)₂]₂ (1) with PhI(OAc)₂ in the presence of a variety of alcohols R₅OH (4) gives the o-alkoxylated phenylglycines C₆H₃(OR₅)R₁C(R₂)(R₃)N(R₄)₂ (5), also as a general process. A partial loss of the enantiomeric excess is observed when the starting phenylglycine is enantiomerically pure, this arising from the formation of bridging azavinylidene (6) and imine intermediate species (7), which were characterized by X-ray diffraction methods. Full article