A recyclable and efficient triazole ligand for the palladium-catalyzed Suzuki–Miyaura and Mizoroki–Heck reactions

A new fluoroalkylated 1,4-disubstituted [1,2,3]-triazole was prepared and acted as an efficient ligand in the palladium-catalyzed Suzuki–Miyaura coupling reactions of aryl boronic acids and aryl halides (Ar–Br and Ar–Cl) and Mizoroki–Heck reactions of aryl halides and alkenes. All reactions proceeded smoothly to give the desired products in moderate to excellent yields under the optimal conditions. Moreover, the ligand could be easily recovered by fluorous solid-phase extraction with excellent purity and reused with slightly decrease in its activity.     

Heterogeneous Fe3O4@chitosan-Schiff base Pd nanocatalyst: Fabrication,characterization and application as highly efficient and magnetically-recoverable catalyst for Suzuki–Miyaura and Heck–Mizoroki C–C coupling reactions

An environmentally friendly palladium-based catalyst supported on magnetite nanoparticles was successfully prepared. FT-IR, XRD, VSM, SEM, EDS and TGA studies have been used to characterize the nanocatalyst. The catalytic activity of the as-prepared catalyst was evaluated as a heterogeneous catalyst for the Suzuki–Miyaura carbon–carbon cross-coupling reaction of aryl halides and phenylboronic acid. Furthermore, it was found that the catalyst showed a high activity for the Mizoroki–Heck reaction of aryl halides and n-butyl acrylate. Interestingly, the novel catalyst could be recovered in a facile manner from the reaction mixture and recycled consecutive five runs without any significant loss in activity.     

Heck reactions catalyzed by oxide-supported palladium – structure–activity relationships

The catalytic activity and selectivity of palladium supported on various metal oxides in carbon–carbon coupling reactions of aryl bromides with styrene (Heck reaction) were investigated. The activity is determined by the nature of the oxide support and the Pd dispersion (structure–activity relationships). The relation of homogeneous (leaching) and heterogeneous mechanisms is discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Hydroformylation of 1-octene using rhodium–phosphite catalyst in a thermomorphic solvent system

The use of a liquid–liquid biphasic thermomorphic or temperature-dependent multicomponent solvent (TMS) system, in which the catalyst accumulates in one of the liquid phases and the product goes preferably to the other liquid phase, can be an enabling strategy of commercial hydroformylation processes with high selectivity, efficiency and ease of product separation and catalyst recovery. This paper describes the synthesis of n-nonanal, a commercially important fine chemical, by the hydroformylation reaction of 1-octene using a homogeneous catalyst consisting of HRh(PPh₃)₃(CO) and P(OPh)₃ in a TMS-system consisting of propylene carbonate (PC), dodecane and 1,4-dioxane. At a reaction temperature of 363 K, syngas pressure of 1.5 MPa and 0.68 mM concentration of the catalyst, HRh(CO)(PPh₃)₃, the conversion of 1-octene and the yield of total aldehyde were 97% and 95%, respectively. With a reaction time of 2 h and a selectivity of 89.3%, this catalytic system can be considered as highly reactive and selective compared to conventional ones. The resulting total turnover number was 600, while the turnover frequency was 400 h^?1. The effects of increasing the concentration of 1-octene, catalyst loading, partial pressure of CO and H₂ and temperature on the rate of reaction have been studied at 353, 363 and 373 K. The rate was found to be first order with respect to concentrations of the catalyst and 1-octene, and the partial pressure of H₂. The dependence of the reaction rate on the partial pressure of CO showed typical substrate inhibited kinetics. The kinetic behavior differs significantly from the kinetics of conventional systems employing HRh(CO)(PPh₃)₃ in organic solvents. Most notable are the lack of olefin inhibition and the absence of a critical catalyst concentration. A mechanistic rate equation has been proposed and the kinetic parameters evaluated with an average error of 5.5%. The activation energy was found to be 69.8 kJ/mol.     

Pd Nanoparticles Stabilized on the Cross-Linked Melamine-Based SBA-15 as a Catalyst for the Mizoroki–Heck Reaction

Catalysis Letters - Mesoporous SBA-15 silicate with a high surface area was prepared by a hydrothermal method, successively modified by organic melamine ligands and then used for deposition of Pd...     

Grafting polymer–protein bioconjugate to boron-doped diamond using aryl diazonium coupling agents

Highly boron doped diamond (BDD) surface was grafted with 4-benzoylphenyl (BP), a photopolymerization initiator group, to provide a platform for surface-confined radical photopolymerization of 2-hydroxyethyl methacrylate (HEMA). The PHEMA-modified BDD hybrid (BDD-PHEMA) resisted non-specific adsorption while the imidazole-functionalized PHEMA graft readily reacted with BSA to provide a bioactive BDD substrate. After incubation of BDD-PHEMA-BSA in anti-BSA and anti-myoglobin solution, it was found that BDD-PHEMA-BSA selectively retained anti-BSA. This work paves the way to fabrication of bioactive BDD layers through a simple process combining the surface chemistry of aryl diazonium salts and photopolymerization.     

Amino-salicylaldimine–palladium(II) complexes: New and efficient catalysts for Suzuki and Heck reactions

A series of amino-salicylaldimine–palladium(II) complexes bearing 5-methyl-3-(R-1-ylmethyl)-salicylaldimine ligands (R = morpholine, piperidine, pyrrolidine, 4-methylpiperazin, diisopropylamine) have been prepared and characterized by IR, ¹H NMR and elemental analysis. Crystal structure details of complex 2b have been confirmed by X-ray structure analysis. The obtained Pd(II) complexes were found to be effective catalysts for the Suzuki and Heck cross-coupling reactions which could be carried out in the undried solvent under air.     

Multi walled carbon nanotubes supported N-heterocyclic carbene–cobalt (ΙΙ) as a novel,efficient and inexpensive catalyst for the Mizoroki–Heck reaction

In this paper, an N-heterocyclic carbene–cobalt complex (NHC–Co^2 +) was immobilized onto the surface of multi-walled carbon nanotubes (MWCNTs) via direct grafting amination approach for the first time. The resultant composite (Co-–NHC@MWCNTs) was characterized by FT-IR, TGA, XRD, ICP-OES, FE-SEM, TEM and CHN analyses. It was demonstrated that Co–NHC@MWCNTs can act as an efficient and inexpensive catalyst for Heck reactions in normal conditions which provided the corresponding products in moderate to good yields. More importantly, this phosphine and palladium-free catalyst can be reused for at least six successive runs without any discernible decrease in its catalytic activity and no remarkable changes were observed in catalyst structure.     

Supramolecular approach to metal–organic gels using excess organic ligand as building units

A metal–organic gels containing Ag(4,4′-bipyridine)NO₃ metal–organic framework and 4,4′-bipyridine units were hydrothermally synthesized using excess 4,4′-bipyridine ligand as building units. The metal–organic gels structure was characterized by various spectroscopic methods and a mechanism of assembly was discussed on the basis of the obtained data. The metal–organic gels retained the characteristics of both the metal–organic framework and gels; furthermore, the reversible hydration/dehydration, reversible anion exchange, and responsive properties were also investigated.     

Pd(II)/Pd(0) Anchored on Magnetic Organic–Inorganic Hybrid Mesoporous Silica Nanoparticles: A Nanocatalyst for Suzuki–Miyaura and Heck–Mizoroki Coupling Reactions

Journal of Inorganic and Organometallic Polymers and Materials - 3-Chloropropyltrimethoxysilane (CPTMS) was grafted on the surface of silica coated Fe3O4 core (Fe3O4@MCM-41) and then condensed with...     

Diastereoselective reductive amination reactions using novel metal–carbon catalysts prepared from inorganic Grignard reagents

A novel class of heterogeneous catalysts prepared from inorganic Grignard reagents is shown to provide finely divided transition metal–carbon nanostructures with potential advantages as selective hydrogenation catalysts under mild liquid‐phase conditions. Preliminary investigations of the catalytic behavior of these materials in diastereoselective reductive amination reactions are described. This revised version was published online in July 2006 with corrections to the Cover Date.     

Highly active recyclable SBA-15-EDTA-Pd catalyst for Mizoroki-Heck,Stille and Kumada C–C coupling reactions

Highly efficient SBA-15-EDTA-Pd(11) heterogeneous catalyst was synthesized by covalent anchoring Pd-EDTA complex over organo-modified surface of SBA-15. SBA-15-EDTA-Pd(11) catalyst was found to exhibit excellent catalytic activity in appreciable yield for Heck, Stille and Kumada cross-coupling reactions. Catalytic system exhibited excellent activity for completion of reaction, isolation, Pd loading (0.87 mmol%) and yields of products as compared to earlier reported heterogeneous supported Pd catalysts. Covalently anchored heterogeneous SBA-15-EDTA-Pd(11) catalyst can be recycled for more than five times without noticeable loss in activity and selectivity.     

Investigation of turbulence modulation in solid–liquid suspensions using parallel competing reactions as probes for micro-mixing efficiency

The Bourne and the Villermaux competitive reaction chemistries were applied to study the effects of suspended particles on the yield of an undesired product and hence to infer their effects on local dissipation rates. Two-phase micro-mixing experiments were carried out in a 1 l stirred vessel, agitated by a pitched-blade turbine, using four particle size ranges: 70–100, 250–300, 700–750 and 1000 μm. Experiments were carried out with up to 1.75 vol% particles in the Bourne scheme and 3 vol% in the Villermaux scheme. Both reaction schemes gave qualitatively similar results, although stronger effects of added particles were obtained with the Bourne chemistry. The effect of 700–750 μm particles could not be distinguished from experimental error, but the other size ranges gave increased by-product yields and suppressed the dissipation rates. These results confirmed earlier two-phase PIV observations: smaller particles (70–100 and 250–300 μm) gave maximum suppression at ∼1 vol%. Above this volume fraction, the level of suppression decreased and in some cases turbulence augmentation occurred, indicating that particle concentration, as well as size, is an important factor.     

Thermoresponsive core–shell nanoparticles with cross-linked π-conjugate core based on amphiphilic block copolymers by RAFT polymerization and palladium-catalyzed coupling reactions

Well-defined amphiphilic block copolymers composed of S-vinyl sulfides and N-isopropyl acrylamide (NIPAM) were synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. Thermoresponsive core–shell nanoparticles with cross-linked π-conjugate cores were obtained by in situ cross-linking reactions between 4-bromophenyl moieties in the block copolymers and diboronic acids or a diamine compound in the presence of a palladium catalyst following micelle formation in ethanol/H₂O or ethanol. We initially investigated RAFT polymerization of two S-vinyl sulfide derivatives, namely phenyl vinyl sulfide (PVS) and 4-bromophenyl vinyl sulfide (BPVS), using a dithiocarbamate-type chain transfer agent (CTA). Then, RAFT polymerization of NIPAM using poly(S-vinyl sulfide) macro-CTAs was conducted to synthesize the amphiphilic block copolymers. Suzuki and Buchwald-Hartwig coupling reactions were found to be effective in the preparation of core–shell nanoparticles with thermoresponsive shells and cross-linked optoelectronic cores. The resulting nanoparticles showed characteristic thermoresponsive properties, as confirmed by turbidity and dynamic light scattering measurements. Stable and uniform core cross-linked nanoparticles were successfully prepared by the in situ palladium-catalyzed coupling reactions, and the optoelectronic and thermoresponsive properties of the nanoparticles could be tuned depending on the nature of the difunctional coupling agents, reaction conditions, and comonomer composition of the block copolymers.     

Synthesis of a ruthenium complex of a cyclic trifunctional η6, η1, η1-arene–diphosphine ligand by intramolecular dehydrofluorinative carbon–carbon coupling

Treatment of the ruthenium complex cation [(η⁶-C₆H₃Me₃-1,3,5)(RuCl(dfppe)]⁺ {dfppe=(C₆F₅)₂PCH₂CH₂P(C₆F₅)₂} with proton sponge yields [{η⁶,η¹,η¹-C₆H₃Me-5-[CH₂-2-C₆F₄P(C₆F₅)CH₂]₂-1,3}RuCl]⁺ by stepwise intramolecular dehydrofluorinative carbon–carbon coupling.     

Room-temperature Suzuki–Miyaura coupling of aryl bromides with phenylboronic acid catalyzed by a palladium complex with an inexpensive nitrogen-containing bis(phosphinite) ligand

A palladium(II) complex with a known inexpensive and very easily synthesized nitrogen-containing bis(phosphinite) ligand has been prepared and characterized by spectroscopic and crystallographic studies. The ligand is bound to the metal in a P,P-bidentate coordination mode with a bite angle of 98.90°. This complex was found to be an efficient catalyst for room-temperature Suzuki–Miyaura coupling of a variety of aryl bromides with phenylboronic acid. At 0.1 mol% of palladium in DMF/K₃PO₄ for 24 h, the corresponding biaryls were obtained with 75–92% yields. Activated substrates displayed high yields even within minutes.