Suzuki Coupling Of Aryl Halides Research Articles

Sol–gel entrapped dichlorobis(triphenylphosphine)palladium as an efficient recyclable catalyst for the cross-coupling of aryl halides with indium- and related alkylating reagents

Physically entrapped dichlorobis(triphenylphosphine)palladium(II) within a silica sol–gel matrix is an efficient catalyst for cross-coupling of aryl iodides, bromides and triflates with intramolecularly stabilized dimethyl- and diethylindium alkylating reagents. The coupling reactions take place in benzene or toluene and depend both on the electronic and steric nature of the substrate, and on the electronic structure of the encaged palladium complex. The immobilized catalyst is leach proof and can be recycled at least four times without significant loss of its activity. The catalyst promotes also the Suzuki coupling of aryl halides with phenylboronic acid and the Stille reaction with tributylphenyltin. In aromatic hydrocarbon solvents both cross-coupling and homocoupling take place as the major and minor processes, respectively. In dioxane homocoupling becomes more significant on account of the desired cross-coupling reaction.

Preparation, Characterization and Catalytic Properties of Polyaniline‐Supported Metal Complexes

AbstractPolyaniline‐supported Sc, In, Pd, Os and Re catalysts were prepared by using a simple protocol and the thus prepared catalysts were well characterized using FTIR, XPS, UV‐Vis/DRS, TGA‐DTA. All the catalysts were successfully employed in a wide range of organic transformations such as cyanation and allylation of carbonyl compound, Suzuki coupling of aryl halides and boronic acids, and, most importantly, in asymmetric dihydroxylation of olefins to afford optically active vicinal diols. All the catalysts were separated from the reaction mixture by simple filtration and reused with consistent activity for five cycles without noticeable leaching of metal from the support.

Layered double hydroxides supported nanoplatinum catalyst for Suzuki coupling of aryl halides

Layered double hydroxides (LDH) supported nanoplatinum catalyst was prepared and employed for Suzuki cross coupling of aryl halides (iodides and bromides) with a broad range of arylboronic to afford the corresponding biaryls in good to excellent yields without using any external ligand. The catalyst is reused for several cycles with consistent activity.

Synthesis and Reactivity of Palladium and Nickel β-Diimine Complexes: Application as Catalysts for Heck, Suzuki, and Hiyama Coupling Reactions

The synthesis of a range of sterically hindered β-diimine ligands and their complexes with palladium(II) and nickel(II) of the formula Pd(κ2N,N-RNCHC(CH2)n−CHNR)(Cl2) (R = 2,6-i-Pr2Ph, 2,6-Me2Ph, Cy, t-Bu, n = 4, 5) and Ni(κ2N,N-RNCHC(CH2)4−CHNR)(Br2) (R = 2,6-i-Pr2Ph, 2,6-Me2Ph) has been investigated. Representative X-ray structures of both ligands and complexes have been determined. The use of the palladium complexes as catalysts for Suzuki coupling of aryl halides and arylboronic acids has been examined. In addition, it has been shown that the palladium complexes are also active in the Heck reaction of aryl bromides and methyl acrylate as well as in the Hiyama coupling of aryl halides and phenyltrimethoxysilane.

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.

Nanofiltration for Homogeneous Catalysis Separation: Soluble Polymer-Supported Palladium Catalysts for Heck, Sonogashira, and Suzuki Coupling of Aryl Halides

The anionic polymerization of 4-methylstyrene results in a linear poly(4-methylstyrene), whose substoichiometric bromination with Br2 converts a portion of 5−18% of the −CH3 units into −CH2Br groups, which were then reacted with (1-Ad)2PH to synthesize a polymer loaded with sterically demanding and electron-rich −CH2P(1-Ad)2 groups as the respective air-stable phosphonium salt. Palladium complexes with the phosphinated polymer are efficient catalysts for carbon−carbon coupling reactions of the Sonogashira, Suzuki, and Heck type with aryl chlorides and bromides. The molecular weight of the respective phosphines in the range of 5−35 kDa does not have a significant effect on the catalytic performance. Such polymer-enlarged catalysts are suitable for separation over a solvent-resistant nanofiltration membrane composed of a dense poly(dimethylsiloxane) (PDMS) layer cast on a porous sublayer of poly(acrylonitrile) (PAN). The membrane displays virtually quantitative retention of the polymeric catalyst; furthermore palladium could not be found in the permeate; TXRF and spectrophotometric determinations are indicative of >99.95% retention of the catalyst. The activity of the catalyst retained in the retentate is almost unchanged, as shown by the high (typically >90%) and almost constant yields of the coupling reactions as well as by the constant turnover frequencies of the catalysts following the membrane separation experiments during up to nine cycles of Sonogashira and Suzuki reactions. For the Heck coupling the used polar aprotic solvents best suited for the catalytic reaction lead to rapid deterioration of the membranes tested.