Cross-coupling Of Aryl Halides Research Articles

Transition-Metal-Catalyzed C-C Bond Formation from C-C Activation.

ConspectusC-C single bonds are ubiquitous in organic compounds. The activation and subsequent functionalization of C-C single bonds provide a unique opportunity to synthesize conventionally inaccessible molecules through the rearrangement of carbon skeletons, often with a favorable atom and step economy. However, the C-C bonds are thermodynamically and kinetically inert. Consequently, the activation of C-C bonds is particularly attractive yet challenging in the field of organic chemistry. In the past decade, we sought to develop efficient strategies to carry out transition-metal-catalyzed diverse C-C cleavage/C-C forming reactions and to obtain some insights into the intrinsic reactivities of different C-C bonds. With our efforts, readily available alcohols, carboxylic acids, and ketones served as suitable substrates for the catalytic C-C coupling reactions, which are reviewed in this Account. In 2009, we observed a Ni-catalyzed cross coupling of aryl nitriles with arylboronic esters through C-CN cleavage. Encouraged by these results, we are interested in transition-metal-catalyzed C-C bond activation. Due to their broad availability, we then turned our attention to C-C cleavage of carboxylic acids. Rhodium-catalyzed decarbonylative coupling of carboxylic acids with (hetero)arenes was then achieved through oxidative addition of in situ formed, more reactive mixed anhydrides to Rh(I) without the need for oxidants that are commonly required for the decarboxylative coupling of carboxylic acids. Subsequently, the decarbonylation of more challenging unstrained aryl ketones was realized under Rh catalysis assisted by N-containing directing groups. Following this work, a group exchange of aryl ketones with carboxylic acids was achieved through 2-fold C-C bond cleavage. By employing the chelation strategy, Rh-catalyzed C-C bond activation of secondary benzyl alcohols was also accomplished through β-carbon elimination of the rhodium alcoholate intermediates. The competing oxidation of secondary alcohols to ketones via β-hydrogen elimination of the same intermediates was suppressed as thermodynamically favorable five-membered rhodacycles are formed after β-carbon elimination. Different types of transformations of alcohols, including the Heck-type reaction with alkenes, cross coupling with arylsilanes, and Grignard-type addition with aldehydes or imines, have been achieved, showing the great potential of secondary alcohols in the formation of C-C bonds. These C-C bond-forming reactions are complementary to traditional cross couplings of aryl halides with organometallic reagents. However, these transformations produce small molecules as byproducts. To improve the atom economy, we then investigated C-C bond transformations of strained-ring cyclic compounds. Ni-catalyzed intermolecular cyclization of benzocyclobutenones with alkynes was recently achieved via the uncommon cleavage of the C1-C8 bond by employing a removable blocking strategy. Rh-catalyzed intramolecular annulation of benzocyclobutenols with alkynes was also achieved. In summary, our developments demonstrate the great potential of transition-metal-catalyzed C-C bond activation for the formation of new C-C bonds. To further expand the synthetic utility of C-C bond activation, more efforts are required to expand the substrate scope and to achieve earth-abundant metal-catalyzed transformations.

Direct synthesis of anilines using copper immobilized on triazine-aminopyridine -modified MIL-101(Cr) MOF

A novel metal-organic framework consisting of supported triazine-aminopyridine (MIL-101(Cr)-NH-TA-AP) was fabricated by post-synthetic modifications of MIL-101(Cr)-NH2. Utilizing the excellent chelating ability of triazine-aminopyridine, Cu ions are immobilized over the host matrix (MIL-101(Cr)-NH-TA-AP/Cu). Subsequently the material has been catalytically employed in the cross-coupling of aryl halides with ammonium acetate (NH4OAc), as the amine source in the presence of cesium carbonate (Cs2CO3) towards the synthesis of diverse aniline derivatives. Some advantages of the synthesized catalyst are high catalytic activity, mild conditions, high thermal stability, and reusability. Moreover, this porous multifunctional nanomaterial can be used as a new support to immobilize other metals in different catalytic reactions.

Aligning Metal Coordination Sites in Metal–Organic Framework-Enabled Metallaphotoredox Catalysis

Construction of catalytic metal centers, the key modules in artificial photosynthetic systems, lies at the heart to explore unpaved reactivity patterns powered by light. Here, we disclose that the amino (-NH2) and carboxylic (-COO) functionalities, aligned in various visible-light-harvesting metal-organic frameworks (MOFs) (NH2-UiO-66, (NH2)2-UiO-67, and NH2-MIL-125), provide N/O-ligated Ni featuring different configurations and valence states. Of note, these Ni centers, in situ formed or preimplanted, demonstrated coordination units' spatial arrangement-dependent activity in cross-coupling of aryl halides and various nucleophiles. Our work provides a novel approach to construct and to regulate metal center(s) by MOFs' skeleton defined coordination environments, highlighting exclusive potential in exploring the reactivity pattern of the hosted metals.

Covalent organic frameworks editing for efficient metallaphotoredox catalytic carbon–oxygen cross coupling of aryl halides with alcohols

Cross-coupling by dual metal/photoredox catalysis is attractive for producing valuable chemical building blocks, where the photoredox catalysts lay the foundations for an efficient and sustainable operation.

Cross-Coupling of Aryl Halides and Alkyl Boronic Esters under Dual Photoredox/Nickel Catalysis

Cross-Coupling of Aryl Halides and Alkyl Boronic Esters under Dual Photoredox/Nickel Catalysis

Facile synthesis of N-aryl phenothiazines and phenoxazines via Brønsted acid catalyzed C-H amination of arenes.

N-Aryl phenothiazines and phenoxazines are of significant importance in various disciplines throughout academia and industry. The conventional synthetic strategy for the construction of these structures centers on the transition-metal-catalyzed cross-coupling of aryl halides with phenothiazines or phenoxazines. Here we present an organocatalytic approach to access N-naphthyl phenothiazine and phenoxazine scaffolds through a straightforward C-H amination of arenes as enabled by an azo group. This reaction features operational simplicity, adequate substrate generality and excellent functional group compatibility. Notably, the efficiency of the catalyst could be perfectly preserved after 5 catalytic cycles.

Forging C-S Bonds Through Decarbonylation: New Perspectives for the Synthesis of Privileged Aryl Sulfides.

Aryl thioethers are tremendously important motifs in various facets of chemical science. Traditional technologies for the precise assembly of aryl thioethers rely on transition-metal-catalyzed cross-coupling of aryl halides; however, despite the continuous advances, the scope of these methods remains limited. Recently a series of reports has advanced an alternative manifold in which thio(esters) are subject to transition-metal-catalyzed decarbonylation, which (1) permits to exploit ubiquitous carboxylic acids as highly desirable and orthogonal precursors to aryl halides; (2) overcomes the issues of high concentration of thiolate anion leading to catalyst poisoning; (3) enables for novel disconnections not easily available from aryl halides; and (4) introduces new concepts in catalysis.

Photoredox C–O Cross Coupling of Aryl Halides and Alcohols on Nickel-Coordinated Carbon Nitride

Key words nickel catalysis - carbon nitride - cross-coupling - photoredox catalysis - aryl halides - alcohols

Continuous-Flow Nickel/Photocatalytic C–N Cross-Coupling of Aryl Halides and Hydrazine Nucleophiles

Key words nickel catalysis - iridium catalysis - photocatalysis - C–N coupling - hydrazine

Recent progress in application of nanocatalysts for carbonylative Suzuki cross-coupling reactions.

In the past few decades, cross-coupling of aryl halides and arylboronic acids in the presence of carbon monoxide (CO), also called carbonylative Suzuki coupling, to form two new carbon–carbon bonds in the production of synthetically and biologically important biaryl ketones, has been widely studied. Consequently, various catalytic systems have been extensively investigated in order to maximize the efficiency of this appealing area of biaryl ketone synthesis. As evidenced in the literature, nanometal-based systems are among the most powerful catalysts for this transformation as their large surface area to volume ratio and reactive morphologies allow faster reaction rates under milder CO pressure even at very low catalyst loadings. This review aims to provide an overview of the recent advances and achievements in the application of nano-sized metal catalysts for carbonylative Suzuki cross-coupling reactions, which may serve as an inspiration to researchers in their future work.

Phosphine-Built-in Porous Organic Cage for Stabilization and Boosting the Catalytic Performance of Palladium Nanoparticles in Cross-Coupling of Aryl Halides.

Herein, we report first a novel phosphine-containing porous organic cage (PPOC) from a [2 + 3] self-assembly of triphenyl phosphine-based trialdehyde and (S,S)-1,2-diaminocyclohexane via dynamic imine chemistry, which was employed as a porous material for the controlled growth of palladium nanoparticles (NPs) due to the strong affinity of Pd to the phosphine ligand based on the principle of hard and soft acids and bases. Comprehensive characterizations including X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, NMR, and X-ray absorption spectroscopy reveal that ultrafine Pd NPs with narrow size distribution (1.7 ± 0.3 nm) and enhanced surface electronic density via a strong interaction between NPs and phosphine were homogeneously dispersed in the PPOC. The resultant catalyst Pd@PPOC exhibits remarkably superior catalytic activities for various cross-coupling reactions of aryl halides, for example, Sonogashira, Suzuki, Heck, and carbonylation. The catalytic activity of Pd@PPOC outperforms the state-of-the-art Pd complexes and other Pd NPs supported on N-containing porous cages under identical conditions, owing to the enhanced surface electronic density of Pd NPs and their high stability and dispersibility in solution. More importantly, Pd@PPOC is highly stable and easily recycled and reused without loss of their catalytic activity. This work provides a new functional POC with extended potentials in catalysis and material science.

Monodentate Trialkylphosphines: Privileged Ligands in Metal-catalyzed Crosscoupling Reactions

Phosphines are widely used ligands in transition metal-catalyzed reactions. Arylphosphines, such as triphenylphosphine, were among the first phosphines to show broad utility in catalysis. Beginning in the late 1990s, sterically demanding and electronrich trialkylphosphines began to receive attention as supporting ligands. These ligands were found to be particularly effective at promoting oxidative addition in cross-coupling of aryl halides. With electron-rich, sterically demanding ligands, such as tri-tertbutylphosphine, coupling of aryl bromides could be achieved at room temperature. More importantly, the less reactive, but more broadly available, aryl chlorides became accessible substrates. Tri-tert-butylphosphine has become a privileged ligand that has found application in a wide range of late transition-metal catalyzed coupling reactions. This success has led to the use of numerous monodentate trialkylphosphines in cross-coupling reactions. This review will discuss the general properties and features of monodentate trialkylphosphines and their application in cross-coupling reactions of C–X and C–H bonds.

Micellar Cross-Coupling of Aryl Halides with N-Tosylhydrazones Catalyzed by Palladium Nanoparticles

Micellar Cross-Coupling of Aryl Halides with N-Tosylhydrazones Catalyzed by Palladium Nanoparticles

Orthogonal Nanoparticle Catalysis with Organogermanes.

Although nanoparticles are widely used as catalysts, little is known about their potential ability to trigger privileged transformations as compared to homogeneous molecular or bulk heterogeneous catalysts. We herein demonstrate (and rationalize) that nanoparticles display orthogonal reactivity to molecular catalysts in the cross‐coupling of aryl halides with aryl germanes. While the aryl germanes are unreactive in LnPd0/LnPdII catalysis and allow selective functionalization of established coupling partners in their presence, they display superior reactivity under Pd nanoparticle conditions, outcompeting established coupling partners (such as ArBPin and ArBMIDA) and allowing air‐tolerant, base‐free, and orthogonal access to valuable and challenging biaryl motifs. As opposed to the notoriously unstable polyfluoroaryl‐ and 2‐pyridylboronic acids, the corresponding germanes are highly stable and readily coupled. Our mechanistic and computational studies provide unambiguous support of nanoparticle catalysis and suggest that owing to the electron richness of aryl germanes, they preferentially react by electrophilic aromatic substitution, and in turn are preferentially activated by the more electrophilic nanoparticles.

Synthesis of Mono- and Bis-Pyrazoles Bearing Flexible p-Tolyl Ether and Rigid Xanthene Backbones, and Their Potential as Ligands in the Pd-Catalysed Suzuki–Miyaura Cross-Coupling Reaction

The present work describes the synthesis of mono- and bis-pyrazole compounds bearing flexible p-tolyl ether and rigid 4,5-dibromo-2,7-di-tert-butyl-9,9-dimethyl-9H-xanthene backbones as pyrazolyl analogues of DPEphos and Xantphos ligands, respectively. The synthesis of new pyrazolyl analogues was accomplished following an Ullmann coupling protocol, and the resulting products were isolated in overall good yields. In addition, a hybrid imidazolyl–pyrazolyl analogue bearing a xanthene backbone was synthesized using the same protocol, whereas a hybrid selanyl–pyrazolyl analogue with a xanthene backbone was synthesized in a good yield employing a second C–H activation step. The symmetrical bis-pyrazolyl and the hybrid imidazolyl–pyrazolyl analogues were found to be the most active among the new ligands evaluated in the Pd-catalysed Suzuki-Miyaura cross-coupling of aryl halides with aryl boronic acids. A simple catalytic system based on Pd(OAc)2/2a was developed, which efficiently catalyses the Suzuki–Miyaura reaction of aryl halides and aryl boronic acids and provides moderate to excellent yields of the corresponding cross-coupling products.

Base-Free Suzuki–Miyaura Coupling Reaction Using Palladium(II) Supported Catalyst in Water

The carbon–carbon bond formation via Suzuki–Miyaura reaction was performed in water as green solvent. Pd(OAc)2(PPh3)2 supported on magnesium hydroxide and cerium carbonate hydroxide composite was prepared and characterized by various techniques. The cross-coupling reaction of aryl halides carried out in water using mild conditions. The effects of temperature, solvents, the amount of catalyst and leaving groups were studied to find the optimization conditions for cross-coupling reaction. Various aryl halides were smoothly transformed into the biaryls in good yields. In addition, the catalyst also exhibited stability and catalytic performance in the cross-coupling of aryl halides. A new approach is developed for carbon–carbon bond formation via Suzuki–Miyaura reaction.2 Pd(OAc)2(PPh3)2 supported on mixed magnesium hydroxide and cerium carbonate hydroxide were prepared and characterized by XRD, XPS, SEM–EDX techniques. The cross-coupling reaction of aryl halides can be carried out in water and under mild conditions (80 °C).

Cobalt Schiff Base Immobilized on a Graphene Nanosheet with N, O Linkage for Cross-Coupling Reaction

A simple and direct pathway to synthesize heterogeneous catalyst by covalently immobilizing a cobalt Schiff base complex on the surface of amino functionalized graphene oxide for the cross coupling of aryl halides and arylboronic acids is reported. The as synthesized samples were characterized using various spectroscopic techniques and thermal analysis to attain their structural and functional features. The analysis confirmed that the Co bounded to the ligand using bi(N, O) linkage and the Co Schiff base complex immobilized onto the functionalized graphene oxide through its amino moiety. The catalytic investigation confirmed the product yield up to 96.5% for the Suzuki cross coupling using gas chromatography. ICP analysis shows that the central active metal is 85% in its catalyst even after the fifth iteration. High product yield, environmentally benign, easy workup, easy filtration of catalyst, and mild reaction conditions are the main facets of this catalyst.

Nanographene Sheet Immobilized Transition Metal Complexes for C-C Coupling Reactions

Transition metal Schiff base complexes covalently immobilized on the surface of amino functionalized graphene sheet to catalyze C-C coupling reaction is reported. Graphene sheet which synthesized using mechanical exfoliation and then by differential oxidative reduction phenomenon of graphite. The schiff base ligand is prepared using aldehyde and amino groups containing compounds which further treated with metal salts to form metal complexes. The as-synthesized metal complexes was then incorporated into amino functionalized nanosheets which are characterized using different spectrochemical techniques. The catalytic investigation of the as-prepared catalyst were done by the cross coupling of aryl halides and aryl boronic acids to form biaryls as product in C-C cross coupling reaction. The yield of the products were high and selective which were analyzed using Gas chromatography technique. The advantage of this catalyst is high stability, recyclability easy recovery of catalyst, environmentally benign and mild reaction condition.

Iron Pincer Complexes as Catalysts in Cross-coupling of Aryl Halides and Phenylboronic Acid

Pincer complexes with iron as active metal center were synthesized to study their catalytic activity in Suzuki-Miyaura coupling reactions. Tridentate pincer ligand was synthesized by the reaction of diphenylchlorophosphine with m-aminophenol and m-phenylenediamine respectively in a 2:1 ratio in the presence of triethylamine as a base and tetrahydrofuran as solvent media. The resultant ligand was complexed with FeSO4 to obtain PCP complexes, C-1 with O and N atoms in the side arms and C-2 with both N atoms in the side arms. The synthesized complexes were examined for their C-C coupling efficiency in cross-coupling between phenyl boronic acid and para substituted halobenzenes. The research study aims to provide an alternative approach to the Pd catalyzed cross coupling methods, an otherwise subjugated method to obtain cross-coupled products. Also the study implores on the effect of variation in the side arm atom relating to the donating ability of the ligand and thereby relatively affecting the coupling yield of the catalysts.

Biphenyl sulfonic acid ligands for catalytic C-N cross coupling of aryl halides with anilines and secondary amines

The use of two biphenyl sulfonic acid ligands for the catalytic C-N cross coupling of aryl halides with anilines, 3-aminopyridine, and secondary amines is reported. Our results represent a significant improvement compared to state of the art methods especially with regards to the removal of palladium.