Search Results (144)

In this study, a novel magnetic metal–organic framework (MOF) composite, Pd@UiO-66@Fe₃O₄, was successfully synthesized as a high-performance heterogeneous catalyst for the Suzuki–Miyaura cross-coupling reaction. The material was prepared by loading nano-sized carboxylated Fe₃O₄ onto UiO-66 via an in situ solvothermal method, followed by the encapsulation of Pd nanoparticles using an ultrasound-assisted dual-solvent method (DSA). Characterization results, including PXRD and TEM, confirmed that the ternary composite retains the structural integrity of UiO-66 while incorporating magnetic functionality and well-dispersed Pd active sites. The catalyst exhibited high catalytic performance for the coupling of aryl iodides and aryl boronic acids. Furthermore, the catalyst demonstrated good compatibility with the substrates examined and excellent stability. Due to the integration of carboxylated Fe₃O₄, the composite could be easily separated from the reaction mixture using an external magnet and reused for at least five cycles without a significant loss in catalytic activity. The high activity and durability are attributed to the integrated roles of the Pd nanoparticles, the porous MOF support, and the magnetic Fe₃O₄ component, which respectively provide catalytic active sites, structural stabilization/dispersion, and magnetic recoverability. Full article

Organoselenium chemistry has undergone remarkable development over the past five decades, evolving from its initial association with high toxicity into a field with pivotal contributions to materials science, organic synthesis, catalysis, and Medicinal Chemistry. Among the diverse biological activities displayed by organoselenium compounds, their redox behaviour is particularly compelling, as many of these molecules act as efficient mimetics of the antioxidant enzyme glutathione peroxidase (GPx). In this work, we investigated the GPx-like activity of a series of N,N′-diaryl selenoureas toward the depletion of H₂O₂ and cumene hydroperoxide (CumOOH) as model ROS. Their reactivity was correlated with the electronic nature of the aryl substituents using a Hammett-type analysis, revealing a strong dependence of the reaction rate on remote electronic perturbations within the aromatic ring. Combined UV and NMR studies provided mechanistic evidence supporting a catalytic cycle in which selenoureas, operating at sub-stoichiometric loadings (1 mol%) and using a thiol as a cofactor-like molecule, can be used to efficiently scavenge ROS with half-lives of only a few minutes (~10–60 min). Furthermore, these selenoureas exhibited potent antiproliferative activity across several human solid tumour cell lines. Overall, these results offer mechanistic insight into the ROS-eliminating pathways of selenoureas and highlight their potential as chemopreventive or anticancer agents. Full article

We report an efficient synthetic method for the preparation of 6H-benzo[c]chromenes from substituted 1-(2′-bromo-[1,1′-biphenyl]-2-yl)-2-phenylethanols. These intermediates were obtained via a TDAE-initiated reaction between new substituted 2′-bromo-[1,1′-biphenyl]-2-carbaldehyde derivatives and substituted nitrobenzylic chlorides. The second step involved a palladium-catalyzed intramolecular O-arylation of the alcohol intermediate under microwave irradiation (110 °C for 1.5 h). The structure of 6H-benzo[c]chromene derivatives was confirmed by X-ray crystallography of product 5c. Full article

The synthesis of a small library of fused Cyclic Aryl Amino Carbon (f-CArAC) carbene precursors in the form of 1,1,2,4-tetraaryl-1H-isoindol-2-ium triflate (6), (7-R) (R = ^tBu, CF₃) or 3,3-dimethyl-2,8-bis-arene-substituted-3,4-dihydro-isoquinolin-2-ium hydrogen-dichloride (8) and 2,4,8-tri(substituted)-isoquinolin-2-ium tosylate salts (12) has been achieved. All of them feature an arene incorporated on the annulated benzene ring of the corresponding heterocycle, introduced at the early stages of their synthesis via the Suzuki cross-coupling reaction between 2,6-dibromo-benzaldehyde and the desired aryl boronic acid. The terphenyl-2′carbaldehyde by-products of this Suzuki reaction are useful starting points for the preparation of two new iminium iodide salts (10-R) (R = H, CF₃) as potential precursors to access ACyclic Amino Carbon (ACAC) carbenes. Compounds (6) and (7-^tBu) react readily with hydroxide either in THF or in a biphasic Et₂O/aqueous OH⁻ solution to produce the substituted isoindolinols (13) and (14), respectively. The thermal dehydration of the former generates the corresponding f-CArAC carbene in situ, which is trapped by Cu(I)Cl furnishing, a rare example of a two-coordinate Cu(I) complex (15) supported by this new ligand scaffold. Full article

Previously unobserved (carbamoyl)disulfanyl chlorides were prepared by (i) addition of limiting aromatic secondary amine to (chlorocarbonyl)disulfanyl chloride; (ii) Harris reactions of sulfur dichloride with appropriate O-alkyl N-methyl-N-arylthiocarbamates; and (iii) regiospecific chlorolysis of bis(N-methyl-N-arylcarbamoyl)disulfanes. The newly synthesized unstable species were observed in situ by ¹H NMR and were trapped with alkenes, thiocarbamates, and thiols using methods precedented by the chemistry of analogous (carbamoyl)sulfenyl chlorides. Furthermore, each of the trapped products was synthesized by an alternate route, reinforcing conclusions about their structures. While (N-methyl-N-phenylcarbamoyl)disulfanyl chloride was unstable and decomposed quickly or cyclized intramolecularly, introduction of the N,2,6-trimethylphenyl moiety led to significantly improved stability. As part of this study, an interesting, unexpectedly stable 1,2,4-dithiazinone was discovered and its structure was established by X-ray crystallography. The new heterocycle, with its twisted out-of-plane disulfide bond in a six-membered ring, readily donated a sulfur atom to triphenylphosphine; this reaction resulted in the formation of triphenylphosphine sulfide, along with the corresponding highly stable heterocycle in which the single sulfur that remains is part of a planar five-membered ring, fused to a co-planar aryl moiety. Full article

The relative reactivity of the nitrovinyl molecular segment characterized by the “cis” orientation of nitro group and the aryl ring was evaluated based on the experimental and Density Functional Theory quantum chemical data. It was found that, on the contrary to E-R-nitroethenes, the Z-2-Ar-1-EWG-1-nitroethene molecular segment is not planar. This fact reduces the possibility of the conjugation of π-electron systems, and as a consequence, decreases the global reactivity. Due to these conditions, the reaction of the model ethyl 4,β-dinitrocinnamate and 2-methylenecyclopentane is realized as a very difficult process; however, with full regioselectivity, it leads to the expected (4 + 2) hetero Diels–Alder cycloadduct. Bonding Evolution Theory studies show that the first new C4-C5 single bond is formed in Phase VIII by merging two pseudoradical centers. In turn, the second C6-O1 single bond is formed in last phase of the reaction, by the depopulation of V(C6), V(O1) and V’(O1) monosynaptic basins. According to this, the title reaction was classified as a process carried out according to a “one-step two-stage” mechanism. 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

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

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

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

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

Palladium-catalyzed carbonylation reactions of ortho-phenylene dihalides were studied using aminoethanols as heterobifunctional N,O-nucleophiles. The activity of aryl-iodide and -bromide as well as the chemoselective transformation of amine and hydroxyl functionalities were studied systematically under carbonylation conditions. Aminocarbonylation can be selectively realized under optimized conditions, enabling the formation of amide alcohols, and the challenging alkoxycarbonylation can also be proved feasible, enabling amide-ester production. Intramolecular double carbonylation reaction can be achieved using 1,2-diiodobenzene and amino alcohols featuring secondary amine groups, giving oxazocine derivatives. Useful reaction scope with various amino alcohols was performed with good isolated yields of the targeted compounds. Intramolecular C-O coupling of amide alcohols possessing bromo substituent in adjacent ortho position is also demonstrated as a potential next step in benzoxazepine heterocycle formation. Full article

Polycarbonate (PC) is a highly versatile plastic material that is extensively utilized across various industries due to its superior properties, including high impact strength and heat resistance. However, its durability presents significant challenges for recycling and waste management. Polycarbonate is a thermoplastic polymer representative of the class of condensation reaction polymers obtained from the reaction of bisphenol A (BPA) and a carbonyl source, such as phosgene or alkyl and aryl carbonate. The recycling processes for PC waste include mechanical recycling, blending with other materials, pyrolysis, and chemical recycling. The latter is based on the cleavage of carbonate units to their corresponding monomers or derivatives through alcoholysis and/or hydrolysis and ammonolysis, normally under basic conditions and without catalysts. This study investigates the efficacy of the use of several heterogeneous catalysts based on silica gel as a robust support, including Sc(III)silicate (thortveitite), which has been previously reported for the preparation of polyesters, core-shell Si-ILs, and core-shell Si-ILs-ZnO, which has never been used before in the depolymerization of polycarbonate, proposing a sustainable and efficient method for recycling this valuable polymer. We chose to explore core-shell catalysts because these catalysts are robust and recyclable, and have been used in very harsh industrial processes. The core-shell silica catalysts used in this study were characterized by XRD; SEM_EDX, FT-IR, and ICP-OES analysis. In our experimental protocol, polycarbonate samples were exposed to the catalyst under controlled conditions (60–150 °C, for 12–24 h) using both oxygen and nitrogen nucleophiles. The depolymerization process was systematically monitored using advanced analytical techniques (GC/MS and GPC chromatography). The experimental results indicated that core-shell silica catalyst exhibits high efficacy, with up to 75% yield for the ammonolysis reaction, producing monomers of high purity. These monomers can be reused for the synthesis of new polycarbonate materials, contributing to a more sustainable approach to polycarbonate recycling. Full article

Cysteine plays a crucial role in the development of an efficient copper-catalyst system, where its thiol group serves as a strong anchoring site for metal coordination. By immobilizing copper onto cysteine-modified, polydopamine-coated magnetite particles, this advanced catalytic platform exhibits exceptional stability and catalytic activity. Chemical modification of the polydopamine (PDA) surface with cysteine enhances copper salt immobilization, leading to the formation of the Fe₃O₄@PDA-Cys@Cu platform. This system was evaluated in palladium-free, copper-catalyzed Sonogashira coupling reactions, effectively catalyzing the coupling of terminal acetylenes with aryl halides. Additionally, the Fe₃O₄@PDA-Cys@Cu platform was employed in click reactions, confirming the enhanced catalytic efficiency due to increased copper content. The reusability of the platform was further investigated, demonstrating improved performance, especially in recyclability tests in click reaction, making it a promising candidate for sustainable heterogeneous catalysis. Full article