Theoretical study of formation mechanism for 4-methyl-3-phenylbenzonitrile in the course of the Hiyama and Suzuki–Miyaura reactions

A theoretical study on the mechanism of conversion of 3-bromo-4-methylbenzonitrile into 4-methyl-3-phenylbenzo-nitrile in the course of the Suzuki–Miyaura and Hiyama−Denmark cross-coupling reactions has been performed at Cam-B3LYP-D3 level of theory. With the use of Pd–NHC type complex as the catalyst, the Hiyama−Denmark cross-coupling is best suited for this process from both thermodynamic and kinetic aspects.     

Highly Active Heterogeneous PdCl2/MOF Catalyst for Suzuki–Miyaura Cross-Coupling Reactions of Aryl Chloride

The exploration of highly efficient Pd/MOF heterogeneous catalyst system for the Suzuki–Miyaura cross-coupling (SMC) reactions of aryl chlorides is still challenging. Herein, a PdCl₂/UiO-67-bpydc was successfully synthesized by immobilizing a low amount of PdCl₂ onto the zirconium-based MOF (UiO-67-bpydc). PdCl₂/UiO-67-bpydc showed excellent catalytic performance and good recycle ability for the SMC reaction of aryl chlorides under an ambient condition. Furthermore, PdCl₂/UiO-67-bpydc retains the high catalytic activity even after five cycles, and exhibited excellent substrate size selectivity.     

N-Heterocyclic Carbene–Palladium Complex onto Graphene Oxide and Poly (ethylene glycol) (PEG) Applied as Superior Catalyst for the Suzuki-Miyaura Cross-Coupling Reaction in Water

Using polymeric nanocomposites incorporated Pd to promote C-C coupling reactions has been found as one of the most successful strategies. In this paper we apply graphene oxide (GO) as an efficient surface immobilized by water-soluble poly (ethylene glycol)-imidazole followed by introduction of PdCl₂ salt to obtain the desired catalyst. Catalytic performance of this composite was investigated in the Suzuki–Miyaura cross-coupling reaction under mild reaction conditions and superior results were obtained. The hydrophilic nature of the catalyst and well distribution of Pd lead to superior catalytic activity in water media. Moreover, the Suzuki–Miyaura reaction proceed successfully with excellent yield and short reaction time without any loss of activity even after seven consecutive reaction cycles.     

Suzuki–Miyaura Cross-Coupling of Bromotryptophan Derivatives at Ambient Temperature

Mild reaction conditions are highly desirable for bio-orthogonal side chain derivatizations of amino acids, peptides or proteins due to the sensitivity of these substrates. Transition metal catalysed cross-couplings such as Suzuki–Miyaura reactions are highly versatile, but usually require unfavourable reaction conditions, in particular, when applied with aryl bromides. Ligand-free solvent-stabilised Pd-nanoparticles represent an efficient and sustainable alternative to conventional phosphine-based catalysts, because the cross-coupling can be performed at considerably lower temperature. We report on the application of such a highly reactive heterogeneous catalyst for the Suzuki–Miyaura cross-coupling of brominated tryptophan derivatives. The solvent-stabilised Pd-nanoparticles are even more efficient than the literature-known ADHP-Pd precatalyst. Interestingly, the latter also leads to the formation of quasi-homogeneous Pd-nanoparticles as the catalytic species. One advantage of our approach is the compatibility with aqueous and aerobic conditions at near-ambient temperatures and short reaction times of only 2 h. The influence of different N^α-protecting groups, boronic acids as well as the impact of different amino acid side chains in bromotryptophan-containing peptides has been studied. Notably, a surprising acceleration of the catalysis was observed when palladium-coordinating side chains were present in proximal positions.     

Rational Design of an Iron-Based Catalyst for Suzuki–Miyaura Cross-Couplings Involving Heteroaromatic Boronic Esters and Tertiary Alkyl Electrophiles

Suzuki–Miyaura cross-coupling reactions between a variety of alkyl halides and unactivated aryl boronic esters using a rationally designed iron-based catalyst supported by β-diketiminate ligands are described. High catalyst activity resulted in a broad substrate scope that included tertiary alkyl halides and heteroaromatic boronic esters. Mechanistic experiments revealed that the iron-based catalyst benefited from the propensity for β-diketiminate ligands to support low-coordinate and highly reducing iron amide intermediates, which are very efficient for effecting the transmetalation step required for the Suzuki–Miyaura cross-coupling reaction.     

Diethylenetriamine-functionalized single-walled carbon nanotubes (SWCNTs) to immobilization palladium as a novel recyclable heterogeneous nanocatalyst for the Suzuki–Miyaura coupling reaction in aqueous media

Pd supported on diethylenetriamine (DETA) modified single-walled carbon nanotubes (SWCNT-DETA/Pd) hybrid materials were fabricated for the first time. The prepared heterogeneous catalyst was characterized by XRD, FTIR, SEM, TGA, and TEM. The catalytic activity of the prepared catalyst was investigated by employing the Suzuki–Miyaura coupling reaction as a model reaction. A series of biphenyl compounds were synthesized through the Suzuki–Miyaura reaction using SWCNT-DETA/Pd²⁺ as a catalyst. The yields of the products were in the range from 80% to 98%. The catalyst can be readily recovered and reused at least for seven consecutive cycles without significant loss of its catalytic activity.     

Synthesis of Arylidene – Isoquinolinones bearing Combretastatin Skeleton by Cyclocarbopalladation/cross coupling Tandem Heck-Suzuki Miaura Reactions using nano catalyst Pd@Py-IL-SPION

Cyclocarbopalladation/cross-coupling cascade intramolecular Heck–Suzuki–Miyaura reactions is applied for the first time by palladium immobilized on pyridine-imidazolium ionic liquid supported magnetic iron oxide nanoparticle catalyst (denoted Pd@Py-IL-SPION) for the last step to synthesize trisubstituted arylidene–isoquinolinones derivatives having Combretastatin skeleton. The reaction is performed via propargylamide intermediates prepared by Ugi 4-CR reactions, which undergoes intramolecular Heck–Suzuki–Miyaura domino reaction to produce the desired trisubstituted arylidene-isoquinolinones. The method shows full regio- and stereoselectivity derives from the particular Pd-catalyzed syn-insertion of triple bond.     

Convenient and efficient Suzuki–Miyaura and Heck–Mizoroki cross-coupling reactions catalyzed by 1,3,4-trisubstituted-1,2,3-triazolium iodide and palladium salt systems

A series of 1,3,4-trisubstituted-1,2,3-triazolium iodide salts (4a–c) were synthesized via a three-step reaction sequence. Corresponding anilines (1a–c) were converted to azides (2a–c) which were then treated with phenylacetylene with “Click” chemistry to access 1,4-disubstituted-1,2,3-triazoles (3a–c). Subsequent methylation of 1,4-disubstituted-1,2,3-triazoles (3a–c) yielded 1,3,4-trisubstituted-1,2,3-triazoliumiodide salts (4a–c) in appreciable yields. All the synthesized compounds were characterized by ¹H and ¹³C NMR, ATR–IR spectroscopic techniques and elemental analyses. Additionally, the structure of 1-(4-chlorophenyl)-4-phenyl-1,2,3-triazole (3b) was confirmed by single crystal X-ray diffraction analysis. The catalytic activity of 4a–c in a catalytic system consisting of 1,3,4-trisubstituted-1,2,3-triazoliumiodide salt/palladium(II) acetate/base were investigated toward Suzuki–Miyaura and Heck–Mizoroki cross-coupling reactions. The Suzuki–Miyaura cross-coupling reactions were carried out under mild reaction conditions with good to excellent yields, whereas Heck–Mizoroki cross-coupling reactions were performed at elevated temperature with moderate yields. Further, in situ method skips the synthetic procedure of preparing the palladium(II) complexes and hence is more economical and less tedious.     

Palladium-Catalyzed Cross-Coupling Reactions of Potassium N-Methyltrifluoroborate Isoindolin-1-one with Aryl and Heteroaryl Chlorides

Potassium N-methyltrifluoroborate isoindolin-1-one was synthesized and used in Suzuki–Miyaura palladium-catalyzed cross-coupling reactions with aryl and heteroaryl chlorides to prepare 29 examples of substituted N-benzyl isoindolin-1-ones. The new approach benefits from mild reaction conditions that tolerate a variety of functional groups. In addition, because of the large number of commercially available aryl and heteroaryl chlorides that can serve as coupling partners, the approach readily provides access to libraries of substituted N-benzyl isoindolin-1-ones.     

Negishi Cross-Coupling in the Preparation of Benzyl Substituted Pyrrolo[2,3-d]pyrimidine Based CSF1R Inhibitors

The colony-stimulating factor 1 receptor (CSF1R) is a protein kinase emerging as an attractive target with clinical relevance in cancer, CNS and inflammatory diseases. Molecular docking experiments followed by synthesis and structure–activity relationship have been used to identify low molecular weight structures as promising hits for lead optimization. These molecules are synthesized from a 4-chloro-6-iodo-pyrrolo[2,3-d]pyrimidine building block using Negishi and Suzuki–Miyaura cross-coupling reactions in high yields. Several inhibitors possessed excellent enzymatic potency, and the parent compound preferably binds to the autoinhibited form of CSF1R. Cellular and in vivo profiling indicate that further tuning of drug structure is needed prior to efficacy studies.     

Biogenic synthesis of palladium nanoparticles using Boswellia sarrata and their applications in cross-coupling reactions

A facile and green route for biogenic synthesis of palladium nanoparticles (PdNPs) using aqueous extract of nontoxic and renewable Boswellia sarrata leaves is reported. The as-synthesized PdNPs were systematically characterized by using ultraviolet (UV)–visible spectroscopy, X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The PdNPs were crystalline and cubic in nature with average particle size of ~6 nm and successfully employed as heterogeneous catalyst in the Suzuki–Miyaura and Mizoroki–Heck cross-coupling reactions. The PdNPs could be recycled up to five times with modest change in the catalytic activity.     

Rational Design of an Iron‐Based Catalyst for Suzuki–Miyaura Cross‐Couplings Involving Heteroaromatic Boronic Esters and Tertiary Alkyl Electrophiles

Suzuki–Miyaura cross‐coupling reactions between a variety of alkyl halides and unactivated aryl boronic esters using a rationally designed iron‐based catalyst supported by β‐diketiminate ligands are described. High catalyst activity resulted in a broad substrate scope that included tertiary alkyl halides and heteroaromatic boronic esters. Mechanistic experiments revealed that the iron‐based catalyst benefited from the propensity for β‐diketiminate ligands to support low‐coordinate and highly reducing iron amide intermediates, which are very efficient for effecting the transmetalation step required for the Suzuki–Miyaura cross‐coupling reaction.     

Flow reactor synthesis of unsymmetrically substituted p-terphenyls using sequentially selective Suzuki cross-coupling protocols

ABSTRACT

Synthetic procedures, based on integrated flow chemical methods, have been developed for the sequential chemo-selective Suzuki–Miyaura cross-coupling of 1,4-dibromo-2-nitrobenzene (1) with various arylboronic acids. The first Suzuki coupling step used a phosphine-(ligand)-free palladium catalyst at room temperature and gave regio-selective coupling of (1) at the ortho-position to the nitro group. The bromo-biaryl product was then directly subjected in situ to a second coupling step, using different arylboronic acids, as a continuous in-flow operation. Based on this methodology, a number of unsymmetrically substituted p-terphenyl compounds were synthesized in excellent overall yields. This approach provides a convenient route to this class of compounds, and is suited for the generation of targeted chemical libraries, or the synthesis of precursors of biologically active natural product analogues that contain the p-terphenyl core. During the first coupling step, dimerization at low levels of the bromo-biaryl intermediate occurred, leading to formation of quaterphenyl compounds.     

External cross-linked sulfonate-functionalized <Emphasis Type="Italic">N</Emphasis>-heterocyclic carbenes: an efficient and recyclable catalyst for Suzuki–Miyaura reactions in water

A sulfonate-functionalized N-heterocyclic carbene (NHC) was successfully attached to a hyper-cross-linked polymer via an external cross-linking reaction. The structure of Poly-BBIS was confirmed by FTIR spectroscopy, TEM, FESEM, and BET. The Poly-BBIS show a large surface areas (up to 563 m² g^?1) and hydrophilicity, as well as abundant micro-mesoporous, tunable and versatile active sites. The catalytic activity of the Pd derivative Poly-BBIS-Pd²⁺ was examined for Suzuki–Miyaura cross-coupling reactions in water, followed by an investigation of the reaction mechanism. The Poly-BBIS-Pd²⁺ gives a yield of 98% for the reaction between bromobenzene and phenylboronic acid with a loading of 0.057 mmol % Pd in water after approximately 2 h. Also, the catalyst can be reused for 5 times without significant loss of activity. This work highlights a low-cost route to the synthesis of heterogeneous catalysts based on hydrophilic sulfonate-functionalized NHC polymers for the Suzuki–Miyaura cross-coupling reaction in water.     

Asymmetric Synthesis of β2-Aryl Amino Acids through Pd-Catalyzed Enantiospecific and Regioselective Ring-Opening Suzuki–Miyaura Arylation of Aziridine-2-carboxylates

A Pd-catalyzed enantiospecific and regioselective ring-opening Suzuki–Miyaura arylation of aziridine-2-carboxylates was developed. The cross-coupling allows for the asymmetric preparation of enantioenriched β²-aryl amino acids, starting from commercially available enantiopure d - and l -serine esters. The mechanism and selectivity of the reaction was rationalized based on computational models.     

The adequacy of the observed kinetic order in catalyst and the differential selectivity patterns to the hypothesis of the cooperative mechanism of catalysis of the Suzuki—Miyaura reaction

The generally accepted mechanism of the Suzuki—Miyaura reaction suggests a sequential activation of the substrate (aryl halide) and the reagent (arylboronic acid) by a palladium catalyst with the formation of unsymmetric biaryl as a result of a single turnover of the catalytic cycle, i.e., it is linear from the kinetic point of view. At the same time, the use of an unconventional kinetic approach based on the analysis of the differential selectivity of the reaction, rather than the regularities of catalytic activity, indicates the inadequacy of the linear mechanism, that is consistent with the hypothesis of a nonlinear (the so-called cooperative) mechanism of catalysis, in which the product is formed as a result of the substrate and reagent activation by two different palladium-containing intermediates in two parallel catalytic cycles. The experimentally observed low kinetic orders of the Suzuki—Miyaura reaction with respect to the concentration of the palladium catalyst precursor under the ligand-free conditions of catalysis are also consistent with the cooperative mechanism and can be due to the changes in the relative amount of the catalyst in two parallel catalytic cycles and/or to the process of catalyst deactivation.

     

Room Temperature Anhydrous Suzuki–Miyaura Polymerization Enabled by C−S Bond Activation

The Suzuki–Miyaura cross-coupling is one of the most important and powerful methods for constructing C−C bonds. However, the protodeboronation of arylboronic acids hinder the development of Suzuki–Miyaura coupling in the precise synthesis of conjugated polymers (CPs). Here, an anhydrous room temperature Suzuki–Miyaura cross-coupling reaction between (hetero)aryl boronic esters and aryl sulfides was explored, of which universality was exemplified by thirty small molecules and twelve CPs. Meanwhile, the mechanistic studies involving with capturing four coordinated borate intermediate revealed the direct transmetalation of boronic esters in the absence of H₂O suppressing the protodeboronation. Additionally, the room temperature reaction significantly reduced the homocoupling defects and enhanced the optoelectronic properties of the CPs. In all, this work provides a green protocol to synthesize alternating CPs.     

Chitosan-supported palladium(0) catalyst for microwave-prompted Suzuki cross-coupling reaction in water

A chitosan-supported palladium (Pd) (0) catalyst was prepared by simple adsorption of palladium(II) ion onto chitosan beads and a subsequent reduction process. To maintain mechanical stability, the chitosan-supported palladium(0) catalyst was cross-linked with either glutaraldehyde or diglycidyl ether polyethylene glycol. The catalysts were utilized for the Suzuki cross-coupling reaction in water. The catalyst, in the presence of a tetrabutylammonium bromide (TBAB) additive, showed excellent catalytic activity in microwave-prompted Suzuki cross-coupling reactions using various aryl halides and boronic acids. In addition, the catalyst was successfully reused up to five times without significant loss of catalytic activity.     

Xylan-type hemicelluloses supported terpyridine–palladium(II) complex as an efficient and recyclable catalyst for Suzuki–Miyaura reaction

Xylan-type hemicelluloses supported terpyridine–palladium(II) as a novel biomass-supported catalyst was synthesized and characterized in terms of morphology, composition, and thermal stability. The nano-Pd catalyst was further explored for Suzuki–Miyaura reaction between arylboronic acid and aryl halide under aerobic condition, with a yield up to 98 %. In particular, the catalyst exhibited both high catalytic activity and stability for Suzuki–Miyaura reaction. Furthermore, the catalyst could be easily recovered by simple filtration and reused at least six times without significant loss of its catalytic activity. This work provides a novel and effective supported catalyst, and broadens the applications of polysaccharides in green catalysis.     

Silica‐supported terpyridine palladium(II) complex as an efficient and reusable catalyst for Heck and Suzuki cross‐coupling reactions

Silica‐supported terpyridine palladium(II) was prepared and used as an effective and recyclable catalyst in Mizoroki–Heck and Suzuki–Miyaura coupling reactions. The catalyst was very effective for the Mizoroki–Heck reaction of aryl halides with olefins and conversion was in most cases excellent. The catalyst showed good thermal stability (up to 230 °C) and could be recovered and reused for four reaction cycles. The Suzuki coupling of aryl iodides with aryl boronic acids in the presence of the catalyst was also investigated and the reaction proceeded with a short reaction time and excellent conversion. Copyright © 2013 John Wiley & Sons, Ltd.