Coupling Reactions Of Aryl Chlorides Research Articles

Nitron-derivative-based palladium carbene complexes: structural characterization, theoretical calculations, and catalytic applications in the Mizoroki-Heck coupling reaction.

New palladium(0) and palladium(ii) complexes with N-heterocyclic carbene (NHC) ligands derived from nitron and its derivatives were synthesized. The structures of most of these complexes were established by single-crystal X-ray diffraction studies. Among the new complexes, the palladium complex with a monodentate NHC ligand derived from nitron demonstrated the highest efficacy as a catalyst precursor in the Mizoroki-Heck coupling reaction of aryl chlorides with alkenes. Theoretical calculations provide valuable insights into the electronic parameters of both the ligands and the palladium complexes, highlighting the significance of a robust Pd-C bond and the π-accepting property of the NHC ligand in achieving enhanced catalytic activity. Notably, catalyst activation occurred much more rapidly with the preformed palladium(0) complex compared to its palladium(ii) counterpart.

Controlled gold–palladium cores in ceria hollow spheres as nanoreactor for plasmon-enhanced catalysis under visible light irradiation

Visible-light-driven organic transformations boosting by localized surface plasmon resonance (LSPR) have been attracting considerable interests. Gold-palladium (Au-Pd) bimetallic nanoparticles (NPs) are considered as ideal plasmonic catalysts realizing efficient light-driven catalysis. Nevertheless, stability and adjustability of plasmonic Au-Pd NPs remain to be a challenging task. Herein, we designed the controlled Au-Pd cores in ceria (CeO2) hollow spheres (Au-Pd@h-CeO2) as nanoreactor for Suzuki cross-coupling reactions. Under visible light irradiation, the Au-Pd@h-CeO2 exhibited remarkable photocatalytic performance with a turnover frequency (TOF) value as high as 797 h−1. More impressively, the coupling reactions of aryl chlorides bearing electron-withdrawing groups proceeded better and afforded the corresponding desired products in good yields. Detailed structural, optical and photoelectrochemical characterizations unraveled that the enhanced photocatalytic efficiency of Au-Pd@h-CeO2 was attributed to the LSPR effect of controllable Au-Pd cores and their synergetic effect of hollow CeO2 shells. The merits of this hollow sphere architecture lied on as followed: (I) Incident light could be reflected and refracted between the inner cores and outer shells, which extended the trapping of incident light, and then enhanced the light harvesting efficiency; (II) the mesoporous architecture of CeO2 hollow spheres provided a huge specific surface area and numerous mesoporous channels, which could enhance the absorption of reactants and provided more active sites; (III) LSPR excitation of Au-Pd NPs and band-gap excitation of CeO2 simultaneously occurred under visible light illumination, inducing a more efficient separation and transfer of charge carriers. Furthermore, due to the confinment effect of CeO2 shells, the Au-Pd@h-CeO2 exhibited an excellent reusability after six cycles without significant deactivation of yield. Our findings provided a facile way to design highly efficient plasmonic-enhanced photocatalysts utilized for catalytic organic reactions.

Front Cover: Silk−Fibroin‐Supported Palladium Catalyst for Suzuki‐Miyaura and Ullmann Coupling Reactions of Aryl Chlorides (Eur. J. Org. Chem. 16/2022)

The Front Cover shows a vortex of silk threads: From Bombyx mori cocoons, the silk fibroin-supported Palladium catalyst is prepared and successfully applied in the Suzuki-Miyaura and Ullmann coupling reactions of aryl chlorides for the synthesis of biaryl products. Cover design by Gianfranco Decandia and Antonio Guaiana. More information can be found in the Research Article by G. M. Farinola et al.

Silk−Fibroin‐Supported Palladium Catalyst for Suzuki‐Miyaura and Ullmann Coupling Reactions of Aryl Chlorides

AbstractRecently, we have reported the preparation of a silk fibroin‐supported Palladium catalyst (Pd/SF) and its use in the Suzuki‐Miyaura cross‐coupling of aryl iodides. Since its synthetic applicability and structural features are still far from being fully explored, a deeper investigation is reported here. Pd/SF is tested as a catalyst for the Suzuki‐Miyaura and Ullmann coupling reactions of aryl chlorides, in H2O/EtOH solvent mixture under atmospheric conditions. Starting from the analysis of the products of the Pd/SF promoted Ullmann reactions of poly‐haloarenes, we can hypothesize the existence of catalytic pockets where monoatomic palladium species can form stable complexes with SF. To shed light on this hypothesis, Pd/SF is characterized by Wide‐Angle X‐ray Scattering (WAXS) analysis, which supports the supposition of catalytic pockets. Finally, using a computational model developed by Molecular Mechanic Energy Minimization we have estimated the dimension of the catalytic pocket of Pd/SF (about 15 Å), in good agreement with the experimental results.

Nickel-Catalyzed Reductive Cross-Coupling of Heteroaryl Chlorides and Aryl Chlorides

We report a nickel-catalyzed cross-electrophile coupling reaction of aryl chlorides and heteroaryl chlorides enabled by a synergistic combination consisting of halide effects and the addition of a magnesium salt. The reaction relies on the electronic difference between the aromatic and heteroaromatic coupling partners to afford the cross-coupled biaryl products using a single catalyst. A variety of heterocycles were amenable to the reaction, as well as a wide range of aryl chlorides, with electron-deficient aryl chlorides performing the best in the reaction. Preliminary mechanistic evidence demonstrates the MgCl2 is essential to the reaction by accelerating the reduction of Ni(II), and that small quantities of iodide lead to improved yields.

Design, synthesis and application of triazole ligands in suzuki miyaura cross coupling reaction of aryl chlorides

DFT calculations have been demonstrated to be a valuable tool for the mechanistic study of reaction which is difficult to acquire from pure experimental techniques. Structural, electronic and coordination aspects of synthesized triazole ligands were investigated theoretically by structure optimization on Gaussian 09 package by DFT approach at B3LYP/6-31G (d, p). HOMO-LUMO energy gaps correlated to its chemical reactivity and this information applied to interpret the role of ligand in the formation of ligand-metal complex. Electron rich environment around the triazole core stabilized the HOMO orbital and made these electrons available to form complex with Pd centre. The DFT calculations provide a plausible mechanism for the reaction that is consistent with the available experimental facts. A series of triazole ligands have been synthesized via efficient 1,3-dipolar cycloaddition of readily available azide and alkynes for coordination to Pd centre. Characterization of all the synthesized compounds was done by FTIR, 1H NMR, 13C NMR and HRMS. Their ligand-Pd complexes provided excellent yields in the Suzuki-Miyaura coupling reactions (up to 92% yield) of unactivated aryl chlorides. Ligand 4-(2,6-dimethoxyphenyl)-1-phenyl-1H-1,2,3-triazole (L2) was found to be most effective ligand because of electron donating 2,6 dimethoxy phenyl moiety attached to triazole ring at 4-position that facilitated the formation of electron rich ligand-catalyst complex. The complex favoured the oxidative addition step of Pd across the aryl chloride substrate and thus allowed for the development of highly active ligand-catalyst system for Suzuki reaction. During computational analysis, 4-(2,6-dimethoxyphenyl)-1-phenyl-1H-1,2,3-triazole (L2) also showed lowest band gap due to electron rich distribution pattern on the HOMO that are involve in ligand-Pd complex formation. Conclusively, these triazoles ligands were found to be more competent and attractive for palladium catalyst because of simplistic pathway for the synthesis of triazole motif and the ease of individual tuning of the substituents on triazole core or exocyclic to it.

Microwave-assisted aqueous carbon–carbon cross-coupling reactions of aryl chlorides catalysed by reduced graphene oxide supported palladium nanoparticles

Microwave-assisted reduced graphene oxide supported palladium nanoparticles can efficiently promote aqueous Ullmann and Suzuki coupling reactions of aryl chlorides.

Cp*Co(iii) and Cu(OAc)2 bimetallic catalysis for Buchwald-type C–N cross coupling of aryl chlorides and amines under base, inert gas & solvent-free conditions

A strategy involving bimetallic catalysis which requires a combination of Cp*Co(CO)I2 and Cu(OAc)2 was used to perform Buchwald-type C–N coupling reactions of aryl chlorides with amines.

Dechlorinated Ullmann Coupling Reaction of Aryl Chlorides on Ag(111): A Combined STM and XPS Study.

Surface-assisted Ullmann coupling was widely applied to construct various molecular nanostructures on surfaces due to its reliability and controllability. By using 4,4''-dichloro-1,1':3',1''-terphenyl (DCTP) as the precursor, covalently bonded zig-zag oligophenylene chains and hexagonal hyperbenzene rings, e. g., [18]-honeycombenes, were successfully fabricated on Ag(111) via dechlorinated Ullmann coupling reaction. Stepwise annealing was applied to investigate the reaction process in detail. Scanning tunneling microscopy and synchrotron X-ray photoemission spectroscopy were utilized to explore the thermal evolution of the DCTP molecules on Ag(111) under ultrahigh vacuum conditions, evidencing the existence of intact DCTP molecules, chemisorbed Cl atoms, covalently bonded DCTP dimers as well as organometallic C-Ag-C-containing intermediates. These results may help understand dechlorinated Ullmann coupling reaction of aryl chlorides on metal surfaces.

A Highly Active Catalyst System for Suzuki–Miyaura Coupling of Aryl Chlorides

A series of new Pd(II) complexes with simple structures were designed and synthesized for Suzuki–Miyaura coupling reactions of aryl chlorides. The new Pd(II) complexes contain bidentate amine ligan...

Room temperature Pd(0)/Ad3P-catalyzed coupling reactions of aryl chlorides with bis(pinacolato)diboron

Room temperature Pd(0)/Ad3P-catalyzed cross-coupling reactions of aryl chlorides with bis(pinacolato)diboron are described. The Pd(0)/Ad3P catalyst, generated from Ad3P-coordinated acetanilide-based palladacycle complex, proved to be an efficient catalyst system for the Miyaura borylation reactions of a variety of aryl chlorides with bis(pinacolato)diboron. The mild reaction condition, the easy availability of the catalyst and good coupling yields make these reactions potentially useful in organic synthesis.

Palladium/phosphorus-functionalized porous organic polymer with tunable surface wettability for water-mediated Suzuki-Miyaura coupling reaction.

A series of phosphorus-functionalized porous organic polymers supported palladium catalysts with tunable surface wettability were successfully prepared using an easy copolymerization and successive immobilization method. The obtained polymers were carefully characterized by many physicochemical methods. Characterization results suggested that the prepared materials featured hierarchically porous structures, high pore volumes, tunable surface wettability and strong electron-donating ability towards palladium species. We demonstrated the use of these solid catalysts for water-mediated Suzuki–Miyaura coupling reactions. It was found that the surface wettability of the prepared catalysts has an important influence on their catalytic activities. The optimal catalyst, which has excellent amphipathicity and relatively high phosphorus concentration, displayed superior catalytic activity compared to the other catalysts. Under ambient conditions, a variety of aryl chlorides can be efficiently transformed to biaryls in high yields. Moreover, the catalyst could be easily recovered and reused at least six times.

Palladium catalyzed chloroethoxylation of aromatic and heteroaromatic chlorides: an orthogonal functionalization of a chloroethoxy linker.

A novel disconnection based on cross-coupling chemistry was designed to access pharmaceutically relevant aryl-aminoethyl ethers. The developed palladium-catalyzed functionalization of aryl- and heteroaryl chlorides with a sodium tetrakis-(2-chloroethoxy) borate salt is orthogonal to the simple nucleophilic replacement of the chloro function of the ethylene linker. The transformation enables efficient 2-chloroethoxylation in the absence of an additional external base. Subsequent amine substitution of the alkyl halide affords 2-aminoethoxy arenes. The applicability of this method was demonstrated through the synthesis of various aryl- and heteroaryl-alkyl ethers, including the intermediates of marketed drug molecules.

A novel ditopic ring-expanded N-heterocyclic carbene ligand-assisted Suzuki-Miyaura coupling reaction in aqueous media

A series of seven-membered ditopic ring-expanded N-heterocyclic carbene (dre-NHC) precursors, bearing sterically demanding and electron-rich aryl groups, were synthesised in moderate yields via the reaction of 1,2,4,5-tetrakis(bromomethyl)benzene with the corresponding N,N′-diarylformamidines in the presence of K2CO3 in acetonitrile under an air atmosphere. All new compounds were characterised by HRMS, NMR spectroscopy, and microanalysis, as well as X-ray crystallography for compound 1c. The development of an efficient catalytic system for the Suzuki-Miyaura coupling reaction of aryl chlorides with various boronic acids was also investigated using the in situ generated dre-NHC ligands.

Eumelanin as a support for efficient palladium nanoparticle catalyst for Suzuki coupling reaction of aryl chlorides in water

Eumelanin-supported palladium (Pd) nanoparticle (NP) catalysts was found to exhibit excellent catalytic activities with high turnover number (TON, 2000) and turnover frequency (TOF, 1000 h−1) for Suzuki cross coupling reaction of aryl chlorides in water. We propose that the amphiphilic property of the eumelanin support helps Pd NPs to catalyse the C–C coupling reaction in water through hydrophobic effect.

Highly bulky and stable geometry-constrained iminopyridines: Synthesis, structure and application in Pd-catalyzed Suzuki coupling of aryl chlorides.

A series of bulky geometry-constrained iminopyridylpalladium chlorides were developed. The steric environment adjacent to the nitrogen atom in the pyridine rings and diimine parts enhanced the thermal stability of the palladium species. Bulkier groups at the imino group stabilized the palladium species and the corresponding palladium chlorides showed high activities in the coupling reaction of aryl chlorides.

Monodentate palladium(0)–[60]fullerene complexes of diphosphine ligands as efficient and sustainable nanocatalysts for the Mizoroki–Heck coupling reaction of aryl chlorides

The present article combines fullerene chemistry with phosphine-based Pd catalytic systems to report new palladium(0)–[60]fullerenes as heterogeneous nanocatalysts for C–C bond transformations of aryl chlorides.

Efficient symmetrical bidentate dioxime ligand-accelerated homogeneous palladium-catalyzed Suzuki–Miyaura coupling reactions of aryl chlorides

A series of N,O-bidentate ligands were synthesized and studied as high activity ligands for palladium-catalyzed Suzuki–Miyaura cross-coupling reactions of aryl chlorides with arylboronic acids under mild conditions.

Highly active palladium catalysts containing a 1,10-phenanthroline analogue N-heterocyclic carbene for room temperature Suzuki-Miyaura coupling reactions of aryl chlorides with arylboronic acids in aqueous media

Two new palladium (II) complexes containing a 1,10-phenanthroline analogue N-heterocyclic carbene (NHC) have been synthesized. The complexes were characterized by 1H and 13C NMR spectroscopy and elemental analysis and their structures were determined by single-crystal X-ray diffraction. The NHC-palladium complexes were employed as catalysts for Suzuki-Miyaura coupling reactions of aryl chlorides with arylboronic acids in aqueous media at room temperature. The cross-coupling reactions were highly efficient with low catalysts loadings.

A Highly Active Pd(II) Complex with 1‐Tritylimidazole Ligand for Suzuki‐Miyaura and Heck Coupling Reactions

AbstractA [Pd(1‐tritylimidazole)2Cl2] complex was synthesized and characterized by 1H and 13C NMR spectroscopy, elemental analysis, and X‐ray crystallography. The X‐ray analysis confirmed that the Pd(II) has a four‐coordinated square planar structure. The palladium complex was used to carry out Suzuki‐Miyaura coupling reactions of aryl chlorides with a variety of phenylboronic acids in i‐PrOH‐H2O (1:1, V:V) at room temperature and Heck coupling reactions of aryl halides with methyl acrylate in DMF at 110°C. High yields of the cross‐coupling products were obtained.