Coupling Of Phenylboronic Acid Research Articles

Fabrication of Fe3O4-Bis(Py-Imine)-PdCl2 Nanocomposite as a Highly Active Nanomagnetic Catalyst for Carbonylative Suzuki Reactions of Phenylboronic Acid with Aryl Iodides and Mo(CO)6

In the research work, a novel and recoverable nanomagnetic pallidum catalyst [Fe3O4-Bis(Py-Imine)-PdCl2 ] based on the immobilization of Pd on the surface of magnetic Fe3O4 nanoparticles modified with picolylamine as ligand was designed and fabricated. The structure of the as-fabricated Fe3O4-Bis(Py-Imine)-PdCl2 nanocatalyst was characterized by FT-IR spectroscopy, SEM, TEM, EDX, ICP-OES, TGA, VSM, XRD and EDX mapping techniques. The Fe3O4-Bis(Py-Imine)-PdCl2 nanocomposite demonstrated the high activity in the preparation of diaryl ketones through one-pot three-component Suzuki reactions of phenylboronic acids with aryl iodides and Mo(CO)6. The recycling of the Fe3O4-Bis(Py-Imine)-PdCl2 catalyst was examined in the coupling of phenylboronic acid with 4-methyl iodobenzene and Mo(CO)6; the results revealed that this catalyst could be reused for more than 6 consecutive runs without a loss of activity. This method offers several remarkable features, such as high yield of products, simplicity of separation of products from catalysts, performing reactions in green solvent and mild conditions, ability to recycle and reusing the catalyst without significant reduction in its catalytic activity.

Synthesis of a novel Pd supported polymeric magnetic nanoparticles with urea-pyridine bridge: application as an efficient catalyst for the C–C and C–N bond formation

Here a novel Pd supported polymeric magnetic nanoparticles with urea-pyridine bridge (denoted as Fe3O4@/Urea-Pyridine/Pd) was synthesized and characterized. The Fe3O4@/Urea-Pyridine/Pd nanocatalyst was synthesized via a four steps process by using Fe3O4 nanoparticles, 3‐(triethoxysilyl) propylisocyanate (TESPIC), 2,6 bis(propyl-triethoxysilylureylene) pyridine (BPS) and palladium chloride. The synthesized polymeric Fe3O4@/Urea-Pyridine/Pd nanocatalyst was analyzed through different analytical techniques, including FT-IR, NMR, XRD, VSM, TGA, DTA, ICP, FESEM, EDX, and BET. The described palladium supported polymeric magnetic nanoparticles with urea-pyridine bridge (Pd-MNPs) was used for the C–C and C–N coupling of phenylboronic acid with various amines and aryl halides in DMF as well as Sonogashira and Suzuki reactions in aqueous solution. Also, the Fe3O4@/Urea-Pyridine/Pd nanocatalyst exhibited high structural stability and excellent recyclability.

Cationic cellulose nanofibrils as a green support of palladium nanoparticles: catalyst evaluation in Suzuki reactions

Cationic cellulose nanofibrils (C-CNF) were used as a support for the growth and the immobilization of Pd NPs using PdCl2 as precursor. The ensuing Pd@C-CNF nanocomposite was tested as a catalyst for the Suzuki coupling reactions between aryl halides and arylboronic acid. Several characterization methods including TEM, HR-TEM, XRD, FT-IR, TGA and XPS were used to confirm the immobilization of Pd NPs onto the C-CNF surface and probe the surface composition after interaction with PdCl2. A quasi total coupling of phenyl boronic acid and 4-bromoacetophenone in DMF at 110 °C was found to occur after 4 h when only 0.02% of Pd@C-CNF of catalyst was used. Furthermore, the Pd@C-CNF could be easily recovered and reused for three consecutive Suzuki reaction cycles without significant loss of its catalytic activity and the loaded percent of palladium nanoparticles was maintained.

Increase of Direct C-C Coupling Reaction Yield by Identifying Structural and Electronic Properties of High-Spin Iron Tetra-azamacrocyclic Complexes.

Macrocyclic ligands have been explored extensively as scaffolds for transition metal catalysts for oxygen and hydrogen atom transfer reactions. C-C reactions facilitated using earth abundant metals bound to macrocyclic ligands have not been well-understood but could be a green alternative to replacing the current expensive and toxic precious metal systems most commonly used for these processes. Therefore, the yields from direct Suzuki-Miyaura C-C coupling of phenylboronic acid and pyrrole to produce 2-phenylpyrrole facilitated by eight high-spin iron complexes ([Fe3+L1(Cl)2]+, [Fe3+L4(Cl)2]+, [Fe2+L5(Cl)]+, [Fe2+L6(Cl)2], [Fe3+L7(Cl)2]+, [Fe3+L8(Cl)2]+, [Fe2+L9(Cl)]+, and [Fe2+L10(Cl)]+) were compared to identify the effect of structural and electronic properties on catalytic efficiency. Specifically, catalyst complexes were compared to evaluate the effect of five properties on catalyst reaction yields: (1) the coordination requirements of the catalyst, (2) redox half-potential of each complex, (3) topological constraint/rigidity, (4) N atom modification(s) increasing oxidative stability of the complex, and (5) geometric parameters. The need for two labile cis-coordination sites was confirmed based on a 42% decrease in catalytic reaction yield observed when complexes containing pentadentate ligands were used in place of complexes with tetradentate ligands. A strong correlation between iron(III/II) redox potential and catalytic reaction yields was also observed, with [Fe2+L6(Cl)2] providing the highest yield (81%, -405 mV). A Lorentzian fitting of redox potential versus yields predicts that these catalysts can undergo more fine-tuning to further increase yields. Interestingly, the remaining properties explored did not show a direct, strong relationship to catalytic reaction yields. Altogether, these results show that modifications to the ligand scaffold using fundamental concepts of inorganic coordination chemistry can be used to control the catalytic activity of macrocyclic iron complexes by controlling redox chemistry of the iron center. Furthermore, the data provide direction for the design of improved catalysts for this reaction and strategies to understand the impact of a ligand scaffold on catalytic activity of other reactions.

Palladium incorporated on carbonaceous catalyst for Suzuki coupling reaction in water

A new palladium incorporated carbonaceous catalyst Pd@CCSO3HNH2 was synthesized by introducing palladium on glucose derived carbocatalyst. The catalyst was well characterized and was used for the Suzuki coupling of phenyl boronic acid with different aryl halides under aqueous conditions. This green methodology represents a ligand free, cost-effective and operationally convenient method for the synthesis of a variety of biaryl’s under the conditions that are tolerant for a broad range of functional groups with good to excellent yields. Moreover, the catalyst could be easily recycled and reused at least five times without any significant loss of its catalytic activity.

Fe3O4@RGO@Au@C Composite with Magnetic Core and Au Enwrapped in Double-Shelled Carbon: An Excellent Catalyst in the Reduction of Nitroarenes and Suzuki–Miyaura Cross-Coupling

Magnetic core double-shelled carbon with Fe3O4 nanoparticles as the core, reduced graphene oxide (RGO) as the inner shell and carbon (C) layer as the outer shell, have been successfully designed and prepared. This tailor-making structure acts as an excellent capsule for encapsulating Au nanoparticles (Au NPs), which could effectively prevent Au NPs from aggregation and leaching. Because of its structural features, magnetic core-double-shell Fe3O4@RGO@Au@C architecture exhibits extremely high catalytic performance on two different kinds of organic reactions (1) reduction of nitroarenes, and (2) Suzuki–Miyaura cross coupling of phenyl boronic acid with aryl halides. Moreover, the synthesized catalyst can be easily recovered and reused for at least ten cycles due to its magnetically separable feature and good stability.

A water-soluble pyridyl-triazole ligand for aqueous phase palladium catalyzed Suzuki–Miyaura coupling

An environmentally friendly water-soluble ligand has been prepared by “clicking” 2-(azidomethyl)pyridine with but-3-ynyl sodium sulphate. In situ combination of the new ligand with [Pd(η3-C3H5)Cl]2 (Pd : ligand = 1 : 1) provides a highly active catalytic system for the Suzuki–Miyaura reaction. Coupling of phenylboronic acid with a variety of aryl or heteroaryl bromides is carried out at catalyst loadings of 0.01% or lower under conventional heating. The aqueous catalytic phase may be used three times without loss of activity.

Palladium nanoparticles supported on SiO2by chemical vapor deposition (CVD) technique as efficient catalyst for Suzuki–Miyaura coupling of aryl bromides and iodides: selective coupling of halophenols

Nanoparticles of palladium were supported on SiO2by chemical vapor deposition technique. The obtained Pd nanocatalyst was characterized by various techniques. This catalyst was found to be very efficient for the selective cross‐coupling of hydroxyl‐substituted aryl iodides and bromide with arylboronic acids in water at room temperature to produce the corresponding hydroxyl‐substituted biaryls. Coupling of phenylboronic acid with aryl iodides and bromides carrying substituents other than hydroxy group was also performed efficiently in refluxing ethanol. Copyright © 2012 John Wiley & Sons, Ltd.

Water-soluble cis-[(NHC)PdBr 2(TPPTS)] catalysts and their applications in Suzuki–Miyaura coupling of aryl chlorides

New palladium(II) complexes ( 2), bearing NHC/TPPTS ligands, (NHC = benzimidazol-2-ylidene; TPPTS = triphenylphosphine-3,3′,3″-trisulfonic acid trisodium salt) have been prepared and characterized by elemental analyses and spectroscopic methods. Their ability to catalyze the Suzuki–Miyaura reaction in neat water has been studied at 100 °C. Very high activities have been observed in the coupling of phenylboronic acid with aryl chlorides in the presence of 1% of the catalyst. We have compared the electronic properties of cis-[PdBr 2(NHC)(TPPTS)] with the related complexes, [PdX 2(NHC)] 2 and [ trans-PdBr 2(NHC)(pdca)] (pdca = pyridine-2,6-dicarboxyic acid) ( 3) via three different techniques: cyclic voltammetry, thermogravimetric analysis and 13C NMR spectroscopy.

A fascinating Suzuki homo-coupling reaction over anchored gold Schiff base complexes on mesoporous host

We present a study of the use of chloro-functionalized mesoporous silicas as supports for immobilization of Au(III) Schiff base complex, and use of this composite material as heterogeneous catalyst for homocoupling of aryl boronic acid. The catalyst was characterised by XRD, FTIR, UV–vis DRS, TG-DTA, etc. Catalyst was initially tested using the coupling of phenylboronic acid with bromo benzene in the presence of K 2CO 3 and with xylene as solvent. The reaction was also tested in the absence of the aryl halide and K 2CO 3. The results indicate that in our catalytic system base is not needed for the activation of phenylboronic acid, and its only role is to neutralize the boric acid. The optimized catalysts are also active in the coupling of a range of aryl boronic acids, and after four catalytic runs they show virtually no drop in activity.

Phenylboronic Acid (PBA): A Versatile Chemical in Synthetic Organic Chemistry

Recently phenylboronic acid (PBA) has been used in ­organic synthesis as a versatile reagent. Examples are ­Suzuki reactions, [1-3] the coupling of PBA with styrene, [4] a ring-opening reaction of epoxy sulfide, [5] the protection of hydroxyl groups, [6] addition of PBA to α,β-unsaturated ­ketones, [7] [8] N- and O-arylations, [9] and a catalytic triple ­condensation reaction. [10] In addition, PBA is also used in carbohydrate sensor design. [12-14]

1,3-Diarylimidazolidin-2-ylidene (NHC) complexes of Pd(II): Electronic effects on cross-coupling reactions and thermal decompositions

The synthesis of 1,3-diarylimidazolidin-2-ylidene (NHC) precursor, 1,3-bis(2,4,6-trimethylphenyl)imidazolinium chloride, ( 3b) has been extended to the electronically and sterically modified NHC precursors 3a (X = H), 3c (X = Br) and 3e (X = Cl) in order to investigate the electronic effect of a p-substituent (X) on cross-coupling catalysts. Complexes of the type PdCl 2(NHC) 2 ( 5), PdCl 2(NHC)(PPh 3) ( 6) and [RhCl(NHC)(cod)] ( 7) were prepared from 3 or 4d (1,3-bis(2,4-dimethylphenyl)-2-trichloromethylimidazolidin). Initial decomposition temperatures of the complexes 5 and 6 were determined by TGA. In situ formed complexes from Pd(OAc) 2 and 3 as well as the preformed complexes 5 and 6 have been tested as catalysts in coupling of phenylboronic acid with 4-haloacetophenones. The electron donating ability of NHCs derived from 3 was assessed by measuring C–O frequencies in the respective [RhCl(NHC)(CO) 2] complex 8 which was prepared by replacement of cod ligand of 7 with CO. An interesting correlation between the electron-donating nature of the aryl substituent and catalytic activity and also initial decomposition temperature of the complexes 5 and 6 was observed.

Nanoparticulate Palladium Supported by Covalently Modified Silicas: Synthesis, Characterization, and Application as Catalysts for the Suzuki Coupling of Aryl Halides

We present a study of the use of amine-functionalized, mesoporous silicas as supports for nanoparticulate palladium, and the use of the composite materials as heterogeneous catalysts for the Suzuki coupling of aryl bromides. Upon modification of the silica, via attachment of N-functionalized aminopropylsilyl ethers to surface silanol groups, only a small reduction in surface area and average pore diameter is observed. The mesoporosity and high surface area are also maintained after introduction of nanoparticulate palladium, as evidenced by the measurement of BET nitrogen sorption isotherms. Electron microscopy shows that the palladium particles are well-dispersed and of typical diameter 3−6 nm. Catalysis was initially tested using the coupling of phenylboronic acid with 4-bromoanisole in the presence of K2CO3 and with toluene as solvent. This revealed that the choice of organic modification has a crucial role in determining the activity and recyclability of the catalyst: optimum behavior was found for diamine- and triamine-containing systems, while quaternary alkylammonium salts showed poor activities. The optimized catalysts are also active in the coupling of a range of aryl bromides and phenylboronic acids, and after three catalytic runs they show virtually no drop in activity. Upon further cycling, however, and after six catalytic runs, we do observe a drop in activity, and this is accompanied by some leaching of palladium and pore-blocking by reaction products and byproducts.

Syntheses, Structures and Redox Properties of New Macrocyclic Triazatriolefinic Pd0 Complexes and Their Polypyrrole Modified Electrodes − Application to Heterogeneous Catalytic Suzuki Cross‐Coupling Reactions

AbstractNew triolefinic macrocyclic ligands of the type (E,E,E)‐1,6,11‐tris(arenesulfonyl)‐1,6,11‐triazacyclopentadeca‐3,8,13‐triene (aryl: a = ferrocenyl, b = 4‐pyrrol‐1‐ylphenyl, c = 4‐methylphenyl) and their Pd0 complexes (1aab, 1abb and 1bcc) have been prepared and characterized. Further structural characterization in the solid state has also been performed by means of X‐ray diffraction analysis for the complex 1bcc. The redox properties of both the ligands and their Pd complexes have been studied using cyclic voltammetric and coulombimetric techniques. In particular, complexes and ligands containing the pyrrole group do polymerize upon exposure to sufficiently positive potentials, on glassy carbon electrodes, generating highly stable modified electrodes. The new modified electrodes are efficient and selective heterogeneous catalysts for Suzuki cross‐couplings, benefiting from simple removal of the catalyst from the reaction vessel. As an example, more than 2·105 metal cycles are achieved at 65 °C in the coupling of phenylboronic acid and cinnamyl bromide. Iodoarenes and phenylboronic acid are also converted into biphenyls with relatively good conversions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Solid-Phase Synthesis of 4-Arylazetidin-2-ones via Suzuki and Heck Cross-Coupling Reactions

Application of the Suzuki and the Heck cross-coupling reactions for efficient synthesis of diverse biaryl- and styryl-substituted β-lactams on solid support using an optimized catalyst system is reported. The coupling of phenylboronic acid with the resin-bound 3-phenoxy-4-iodophenyl β-lactam 1a proceeded in 89% isolated yield by employing 20 mol % of the bidentate phosphine−palladium complex, [1,1‘-bis(diphenylphosphino)ferrocene]palladium(II) dichloride {PdCl2(dppf)} as catalyst in the presence of triethylamine (TEA, 10 equiv) in DMF at 65 °C for 12 h. Efficient cross-coupling of the iodophenyl β-lactam to heterocyclic boronates and aryl boronates substituted with various electron-donating and -withdrawing groups is also demonstrated. The reverse coupling reactions of immobilized arylboronic acid 1c with a variety of substituted aryl iodides were found to proceed in excellent yields using the same catalyst system in a 3/7 mixture (v/v) of H2O:DMF at 40 °C. The use of this catalyst for the vinylation of a...

Palladium-Catalyzed Cross-Coupling of Organoboron Compounds with Iodonium Salts and Iodanes.

The palladium-catalyzed cross-coupling reaction of iodinanes (iodonium salts and iodanes) with organoboron compounds to form carbon-carbon bonds was achieved at ambient temperature under aqueous conditions in the absence of base. Coupling of phenylboronic acid with diphenyliodonium tetrafluoroborate in the presence of Pd(PPh(3))(4) (0.2 mol %) or Pd(OAc)(2) (0.2 mol %) under aqueous conditions gave biphenyl in almost quantitative yield. Under the same conditions, substituted boronic acids, boronates, and trialkylboranes were readily coupled with diaryl-, alkenyl-, and alkynyliodonium salts. Finally, the iodanes ArI(OH)OTs underwent cross-coupling with boronic acids, boronates, and trialkylboranes to afford biphenyls and aryl-substituted alkenes.