Search Results (108)

In the last decades, numerous approaches have been explored for the cross-coupling of biaryl building blocks depending on the presence of boron sources. In fact, these changes have been catalyzed by transition metal complexes. This review focuses on the progress of the last decade in transition metal-catalyzed C–X borylation and direct C–H borylation, with emphasis on nickel-catalyzed C–H borylation, as effective and affordable protocols for the borylation of aryl substrates. In addition, Suzuki-type cross-coupling by activation of C–H, C–C, or C–N bonds is also reported. This study then offers an overview of recent advances for the synthesis of bi- and multi-aryls found in synthetic molecular complexes and natural products using the transition metal-catalyzed one-pot Miyaura-type C–X and C–H borylation–Suzuki coupling sequence. Full article

The fabrication of low-dimensional nanostructures through on-surface synthesis has emerged as a promising strategy for developing high-precision electronic devices. Among various reactions, Ullmann-type coupling (with carbon–halogen bond activation) stands out in this field as a prevalent methodology due to its straightforward activation process, highly programmable characteristics, and remarkable synthetic efficiency. To date, on-surface Ullmann-type coupling reactions of aryl halide precursors have been extensively studied with the assistance of in situ characterization techniques. The resulting carbon-based nanostructures exhibit high structural diversity and significant potential for applications in molecular electronics. This review categorizes recent progress in the precise preparation of carbon-based nanostructures based on molecular precursors with distinct halogen substituted sites, including para-, meta-, and ortho-sites, peri- and bay-regions, and their combination. In addition, systematic analysis and comparative discussion of their respective characteristics is also provided. Full article

A facile and efficient method for synthesizing diarylphosphinates from alcohols and aryl halides, using stable, green, and readily available sodium hypophosphite as a phosphorus source, is disclosed herein for the first time. This method offers high-efficiency and excellent functional group tolerance, providing a straightforward approach to synthesizing a broad range of diarylphosphinates from green starting materials with moderate to excellent yields. Full article

In this study, we developed a palladium-catalyzed decarbonylative nucleophilic halogenation reaction using inexpensive and readily available acid anhydrides as substrates. This approach effectively circumvents the instability of acyl chlorides and the low reactivity of acyl fluorides. The Pd/Xantphos catalyst system exhibited excellent compatibility with the thermodynamically and kinetically challenging reductive elimination of C–X bonds (X = I, Br, and Cl) from Pd(II) intermediates. Notably, for electron-donating substrates, adopting an open system significantly improved the reaction efficiency. The positive effect of the open system may be due to the reversible nature of CO insertion and deinsertion, which helps direct the reaction toward the desired pathway by allowing the generated CO to exit the reaction system. Mechanistic studies suggest that the reaction proceeds through a highly reactive acyl halide intermediate, followed by a unimolecular fragment coupling (UFC) pathway via decarbonylation or an alternative pathway involving the formation of an activated anionic palladate complex in the presence of lithium halide. Full article

The application of metal–organic frameworks (MOFs) has attracted increasing attention in organic synthesis. The modification of MOFs can efficiently tailor the structure and improve the property for meeting ongoing demand in various applications, such as the alteration of gas adsorption and separation, catalytic activity, stability, and sustainability or reusability. In this study, carboxyethylsilanetriol (CEST) disodium salt was used as a dual-functional ligand for modified Al-MIL-53 to fabricate CEST-functionalized Al-MIL-53 samples through a hydrothermal reaction of aluminum nitrate, terephthalic acid, and CEST disodium salt by varying the molar ratio of CEST to terephthalic acid and keeping a constant molar ratio of Al³⁺/-COOH of 1:1. The structure, composition, morphology, pore feature, and stability were characterized by XRD, different spectroscopies, electron microscopy, N₂ physisorption, and thermogravimetric analysis. With increasing CEST content, CEST-Al-MIL-53 still preserves an Al-MIL-53-like structure, but the microstructure changed compared with pure Al-MIL-53 due to the integration of CEST. Such a CEST-Al-MIL-53 was used as the support to load Pd particles and afford a catalyst Pd/CEST-Al-MIL-53 for Suzuki–Miyaura C-C cross-coupling reaction of aryl halides and phenylboronic acid under basic conditions. The resulting Pd/CEST-Al-MIL-53 showed a high catalytic activity compared with Pd/Al-MIL-53, due to the nanofibrous structure of silicon species-integrated CEST-Al-MIL-53. The nanofiber microstructure undergoes a remarkable transformation into intricate 3D cross-networks during catalytic reaction, which enables the leachable Pd particles to orientally redeposit and inlay into these networks as the monodisperse spheres and thereby effectively preventing Pd particles from aggregation and leaching, therefore demonstrating a high catalytic performance, long-term stability, and enhanced reusability. Obviously, the integration of CEST into MOFs can effectively prevent the leaching of active Pd species and ensure the re-deposition during catalysis. Moreover, catalytic performance strongly depended on catalyst dosage, temperature, time, solvent, and the type of the substituted group on benzene ring. This work further extends the catalytic application of hybrid metal–organic frameworks. Full article

In recent years, there has been growing interest in the development of greener alternatives to traditional reagents used in carbon–carbon coupling reactions, particularly in response to environmental concerns. The commonly used aryl halides, despite being highly reactive in the Suzuki–Miyaura coupling (SMC), pose significant environmental risks. As a result, research has shifted towards exploring the use of phenols, which are widely accessible and environmentally benign. However, phenols are considerably less reactive due to the poor leaving group properties of the hydroxyl group, necessitating prior activation to facilitate their use in coupling reactions. This work aims to review the recent investigations on the activation strategies for phenols, focusing on their application in the Suzuki–Miyaura and related C-C couplings. In addition, the exploration of the potential of conducting the activation step “in situ” will also be discussed. We hope that this article will pave the way for the development of more sustainable and efficient coupling methodologies, addressing both ecological and practical challenges in organic synthesis. Full article

Nitriles are valuable compounds because they have widespread applications in organic chemistry. This report details the nickel-catalyzed reductive cyanation of aryl halides and epoxides with cyanogen bromide for the synthesis of nitriles. This robust protocol underscores the practicality of using a commercially available and cost-effective cyanation reagent. A variety of aryl halides and epoxides featuring diverse functional groups, such as -TMS, -Bpin, -OH, -NH₂, -CN, and -CHO, were successfully converted into nitriles in moderate-to-good yields. Moreover, the syntheses at gram-scale and application in late-stage cyanation of natural products and drugs reinforces its potentiality. 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

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

Introduction: N-heterocyclic carbenes (NHCs) are considered important preferred auxiliary ligands for transition metals due to their strong σ-donor and weak π-acceptor properties and ease of structural modification in catalyst design. The functionalization of NHC by adding different substituent groups is an effective strategy for designing complexes with desired electronic and steric properties. NHC–Pd complexes are of particular importance due to their resistance to air, moisture and heat and their strong stability under catalytic and biological conditions. It is known that NHC–Pd complexes show excellent performance in the Suzuki–Miyaura cross-coupling reaction. The traditional Suzuki–Miyaura reaction involves the cross-coupling reaction of alkyl and arylboronic acids with aryl halides. This reaction has some advantages over other C-C coupling reactions. The use of water as a suitable and reliable solvent in the reaction, the fact that the reaction products are generally poorly soluble in water and can be easily separated from the reaction mixture, the use of non-toxic chemicals, the moderation of reaction conditions, and good functional group compatibility make it useful and worth studying. There are many examples of studies on the application of NHC–Pd complexes in the Suzuki–Miyaura reaction in aqueous media, and the highly effective catalytic activities and versatility of these reactions have been proven. Methods: In this study, a series of benzimidazole-based Pd–NHC complexes were synthesized. The synthesized complexes were characterized by spectroscopic methods. All complexes were tested as catalysts in the Suzuki–Miyaura cross-coupling reaction. Results: According to the obtained results, the synthesized benzimidazole-based Pd–NHC complexes were found to have high catalytic activity in the Suzuki–Miyaura cross-coupling reaction. Conclusions: The synthesized NHC-Pd complexes can be used as potential catalysts due to their high catalytic activity. It is thought that these catalysts can be used in different biochemical studies in the future. Full article

Thioethers are critical in the fields of pharmaceuticals and organic synthesis, but most of the methods for synthesis alkyl thioethers employ foul-smelling thiols as starting materials or generate them as by-products. Additionally, most thiols are air-sensitive and are easily oxidized to produce disulfides under atmospheric conditions; thus, a novel method for synthesizing thioethers is necessary. This paper reports a simple, effective, green method for synthesizing dialkyl or alkyl aryl thioether derivatives using odorless, stable, low-cost ROCS₂K as a thiol surrogate. This transformation offers a broad substrate scope and good functional group tolerance with excellent selectivity. The reaction likely proceeds via xanthate intermediates, which can be readily generated via the nucleophilic substitution of alkyl halides or aryl halides with ROCS₂K under transition-metal-free and base-free conditions. Full article

Methyl 4-(1,3a,6a-triazapentalen-3-yl)benzoate (TAP1) shows interesting properties as a small molecule fluorophore. In the search for post-functionalization methods, palladium-catalyzed arylation reactions were demonstrated. Direct CH arylation reactions of TAP1 with various aryl halides resulted in 3,6-diaryltriazapentalenes TAP4, although mostly in poor yields. Bromination of TAP1 followed by Suzuki coupling, on the other hand, requires a more delicate procedure, but gave arylated products with the same regiochemistry (TAP4) in moderate to good yields. The structure of 6-phenyltriazapentalene TAP4a was confirmed by crystallographic analysis. In addition, the effect of the C6 arylation on the fluorescent properties of 3-aryl-1,3a,6a-triazapentalenes was studied in dichloromethane at room temperature and in 2-methyltetrahydrofuran at 77 K, while the photophysical properties of two saponified derivatives were measured in acetonitrile. Full article

An efficient palladium-catalyzed carbonylation of aryl fluorosulfates with aryl formates for the facile synthesis of esters was developed. The cross-coupling reactions proceeded effectively in the presence of a palladium catalyst, phosphine ligand, and triethylamine in DMF to produce the corresponding esters in moderate to good yields. Of note, functionalities or substituents, such as nitro, cyano, methoxycarbonyl, trifluoromethyl, methylsulfonyl, trifluoromethoxy, fluoro, chloro, bromo, methyl, methoxy, N,N-dimethyl, and [1,3]dioxolyl, were well-tolerated in the reactions, which could be kept for late-stage modification. The reactions employing readily available and relatively robust aryl fluorosulfates as coupling electrophiles could potentially serve as an attractive alternative to traditional cross-couplings with the use of aryl halides and pseudohalides as substrates. Full article

In this article, we present a comprehensive computational investigation into the reaction mechanism of N-arylation of substituted aryl halides through Ullmann-type coupling reactions. Our computational findings, obtained through DFT ωB97X-D/6-311G(d,p) and ωB97X-D/LanL2DZ calculations, reveal a direct relation between the previously reported experimental reaction yields and the activation energy of haloarene activation, which constitutes the rate-limiting step in the overall coupling process. A detailed analysis of the reaction mechanism employing the Activation Strain Model indicates that the strain in the substituted iodoanilines is the primary contributor to the energy barrier, representing an average of 80% of the total strain energy. Additional analysis based on conceptual Density Functional Theory (DFT) suggests that the nucleophilicity of the nitrogen in the lactam is directly linked to the activation energies. These results provide valuable insights into the factors influencing energetic barriers and, consequently, reaction yields. These insights enable the rational modification of reactants to optimize the N-arylation process. Full article

Radicals based on arylamine cyclophanes can be used as functional materials and show application potential in fields such as synthetic chemistry, molecular electronic components, organic light-emitting diodes, and catalytic chemistry. Using a Buchwald–Hartwig palladium-catalyzed aryl halide amination method, we synthesized a series of neutral hexaazacyclophane compounds 1–3 with different substituents in the meta–meta–meta positions of the phenyl rings. Three characteristic high-spin hexaazacyclophane diradical dications were obtained by two-electron oxidation using AgSbF₆: 1^2·+•2[SbF₆]⁻, 2^2·+•2[SbF₆]⁻, and 3^2·+•2[SbF₆]⁻. The electronic structures and physical properties of these compounds were then investigated by ¹H and ¹³C nuclear magnetic resonance spectroscopy, cyclic voltammetry, electron paramagnetic resonance spectroscopy, superconducting quantum interferometry, ultraviolet–visible spectroscopy, and density functional theory calculations. The findings provide new ideas for designing radical species with novel physical properties and electronic structures. Importantly, the obtained radical species are not sensitive to air, making them valuable functional materials for practical applications. Full article