Isonitriles as efficient ligands in Suzuki-Miyaura reaction

Isonitrile palladium complexes [(RNC)₂PdCl₂] were prepared and tested in Suzuki reaction of 4-chloroanisol. (AdNC)₂PdCl₂ was found the most effective catalyst and was used in phenylation of several chloro and bromoaromatic substrates.     

cis-Fashioned palladium (II) complexes of 2-phenylbenzimidazole ligands: Synthesis, characterization, and catalytic behavior towards Suzuki-Miyaura reaction

Reaction of 2-arylbenzimidazole with PdCl₂(CH₃CN)₂ in CH₂Cl₂ affords benzimidazole palladium (II) complexes in high yields. The structure of complexes C1, C2, and C3 has been confirmed by X-ray structure analysis. The configuration of complexes depends on the substituent on the 2-position of benzimidazole. Phenyl affords the complexes in cis-fashion due to π-π stacking of phenyl and benzimidazole. Tolyl affords the complex in trans-fashion. The catalytic studies show that cis-configured 2-phenylbenzimidazole palladium (II) complexes are highly efficient catalysts in the Suzuki-Miyaura reaction.     

A polymer-supported salen-type palladium complex as a catalyst for the Suzuki-Miyaura cross-coupling reaction

A salen-type palladium(II) complex was readily immobilised onto a Merrifield resin. The supported complex is an effective recyclable heterogeneous catalyst for the Suzuki cross-coupling reaction without the use of phosphine ligands. Leaching of the metal into solution from the supported catalyst proved negligible.     

Synthesis of a bis(phenoxyketimine) palladium(II) complex and its activity in the Suzuki-Miyaura reaction

The synthesis of a new charge-neutral, air- and moisture-stable fluorinated bis(phenoxyketimine) Pd(II) complex is presented. Its activity as a precatalyst in the Suzuki-Miyaura cross-coupling reaction of activated and unactivated bromides has been explored.     

Salen and half-salen palladium(II) complexes: synthesis, characteriztion and catalytic activity toward Suzuki-Miyaura reaction

Salen and half-salen palladium(II) complexes (salden)Pd (1, salden=N,N′-bis(3,5-di- tert-butylsalicylidene)-1,2-dimethylethylenediamine), (hsalph)PdCl (2, hsalph=3,5-di-tert- butylsalicylidene-1-iminophenylene-2-amine), and (salph)Pd (4, salph=N,N′-bis(3,5-di-tert- butylsalicylidene)-1,2-phenylenediamine) were prepared and structurally characterized by X-ray crystallography. Complex 2 proved to exhibit high catalytic activity toward Suzuki-Miyaura reaction. Polyaromatic C₃-symmetric derivatives and various fluorinated biphenyl derivatives were readily achieved in good yields using Suzuki-Miyaura reaction catalyzed by complex 2.     

In situ generation of palladium nanoparticles: ligand-free palladium catalyzed ultrafast Suzuki-Miyaura cross-coupling reaction in aqueous phase at room temperature

An ultrafast and highly efficient ligand-free Suzuki-Miyaura cross-coupling reaction between aryl bromides/iodides and arylboronic acids using palladium chloride as catalyst in PEG400/H₂O in air at room temperature has been developed. TEM showed that palladium nanoparticles were generated in situ from PdCl₂/PEG400/H₂O without use of other reductants. The catalyst system can be recycled to reuse three times with good yields.     

Pd-EDTA as an efficient catalyst for Suzuki-Miyaura reactions in water

PdCl₂-EDTA complex 1 is an efficient catalyst for the Suzuki-Miyaura reactions of aryl and heteroaryl halides with aryl(heteroaryl)boronic acids in water at 20-100 °C. Aryl iodides and bromides undergo the cross-coupling with turnover numbers (TON) up to 97,000 and turnover frequencies (TOF) up to 582,000 h⁻¹.     

Impregnated palladium on magnetite, a new catalyst for the ligand-free cross-coupling Suzuki-Miyaura reaction

A new catalyst for the cross-coupling Suzuki-Miyaura reaction is reported. The impregnated palladium on magnetite catalyst is very easy to prepare using the standard impregnation methodology. This catalyst avoids the use of any type of expensive and difficult handle organic ligand, showing excellent yields, under mild reaction conditions, for the classical formation of biaryl compounds. The catalyst is very easy to remove from the reaction medium, only by using a simple magnet, and it could be re-used up to three times with only a slightly decrease of the chemical yield.     

Triphenylphosphine as reducing agent for copper(II)-catalyzed AGET ATRP

Triphenylphosphine(TPP) was used as reducing agent to continuously generate the Cu(I) activator in copper(II)-catalyzed activators generated by electron transfer atom transfer radical polymerization(AGET ATRP). For example, the polymers prepared with a molar ratio of [MMA]0/[EBi B]0/[Cu Cl2]0/[PMDETA]0/[TPP]0 = 500/1/0.1/0.5/0.5 had controlled molecular weights and low molecular weight distribution(Mw/Mn) values(~1.2). TPP as a commercial reducing agent provides a convenient copper-catalyzed AGET ATRP procedure for the preparation of well-defined polymers.     

室温有氧条件下高稳定性Pd(P-Phos)Cl2配合物催化Suzuki-Miyaura交叉偶联反应

制备了新型Pd(P-Phos)Cl₂配合物, 并通过¹H, ¹³C和³¹P核磁共振及X射线单晶衍射对其结构进行了确认及表征. 结果表明, 该配合物是室温有氧条件下Suzuki-Miyaura交叉偶联反应的高稳定高效催化剂, 并具有广泛的底物适用性. 催化剂用量较低, 且转化数(TON)最高可达49000.     

Catalytic activity of η-(olefin)palladium(0) complexes with iminophosphine ligands in the Suzuki-Miyaura reaction. Role of the olefin in the catalyst stabilization

The catalytic activity of η²-(olefin)palladium(0)(iminophosphine) complexes in the Suzuki-Miyaura coupling is strongly dependent on the reaction conditions and on the nature of the ligands. The reaction is at the best carried out in aromatic solvents in the presence of K₂CO₃ at 90-110 °C. Higher reaction rates are obtained when the R substituent on the N-imino group is an aromatic group of low steric hindrance and the olefin is a moderate π-accepting ligand such as dimethyl fumarate. At temperatures lower than 90 °C, a self-catalyzed process leading to catalyst deactivation becomes predominant. Preliminary mechanistic investigations indicate that the oxidative addition of the aryl bromide to a Pd(0) species is the rate determining step in the catalytic cycle and that the olefin plays a key role in catalyst stabilization. Systems in situ prepared by mixing Pd(OAc)₂ or Pd(dba)₂ with 1 equiv of iminophosphine appear substantially less active than the preformed catalysts.     

Palladium(II)-N-heterocyclic carbene complex derived from proline towards Suzuki-Miyaura coupling reaction in water at room temperature

Palladium(II)-N-heterocyclic carbene complex 1 derived from proline has been proved to be a highly effective catalyst in the Suzuki-Miyaura coupling reaction of aryl iodides and bromides with arylboronic acids in water at room temperature. The reactions are tolerant towards various functional groups in the substrates. Moreover, the complex 1-catalyzed medium-scale (10.0 mmol) Suzuki-Miyaura reactions were also carried out and it was found that the complex was also effective enough in these cases.     

Amine- and phosphine-free palladium(II)-catalyzed homocoupling reaction of terminal alkynes

An efficient, amine- and phosphine-free palladium(II)-catalyzed homocoupling of terminal alkynes has been developed. In the presence of PdCl₂, CuI, Me₃NO, and NaOAc, homocoupling of various terminal alkynes underwent smoothly to afford the corresponding diynes in moderate to high yields without any phosphine ligands. In contrast, the presence of a phosphine ligand (PPh₃) disfavored this palladium-catalyzed homocoupling procedure. Bases, solvents, and CuI have fundamental influence on the palladium-catalyzed homocoupling of terminal alkynes.     

Bis-chelate tetracarbene palladium(II) complex as an efficient and recyclable catalyst precursor for Heck reaction

A homoleptic Pd(II) complex with two chelating di-N-heterocyclic carbene (NHC) ligands has been synthesized and its square planar molecular geometry has been determined by X-ray diffraction analysis. The complex proved to be an efficient catalyst having exceedingly high turnover number and good reusability in Heck reaction.     

Convenient synthesis of photochromic symmetrical or unsymmetrical bis(heteroaryl)maleimides via the Suzuki-Miyaura cross-coupling reaction

A general method for the synthesis of symmetrical or unsymmetrical bis(heteroaryl)maleimides by a one-pot procedure involving Suzuki-Miyaura cross-coupling sequence was developed on the basis of the reaction of 3,4-diiodo-1-benzyl-1H-pyrrole-2,5-dione with cyclic boronate esters using PdCl₂(dppf) as the catalyst. Photochromic properties of the products were examined.     

General and efficient methodology for the Suzuki-Miyaura reaction in technical grade 2-propanol

The reaction profile of a series of palladium-based catalysts was examined in the Suzuki-Miyaura reaction using technical grade 2-propanol as solvent and potassium t-butoxide as base. The results generally show high activity. The method allows for the coupling of electron-rich aryl chlorides with sterically hindered aryl boronic acids to produce tri-ortho-substituted biaryls in high yields using very mild conditions and short reaction times.     

Dimethylaminoalkyl chalcogenolate palladium(II) complexes as an efficient copper- and phosphine-free catalyst for Sonogashira reaction

N,N-Dimethylaminoalkyl chalcogenolate Pd(II) complexes [PdCl(E^∩NMe₂)]_n has been investigated as a moisture/air-stable and robust catalyst for Sonogashira cross-coupling reaction in the absence of copper and phosphine ligand. The dimeric palladium(II) complex of selenium containing ligand shows the best catalytic activity as compared with monomeric and trimeric complexes. The variety of functional groups are tolerated under optimized catalytic systems and provide excellent yields of the products.     

[PdCl2{8-(di-tert-butylphosphinooxy)quinoline)}]: a highly efficient catalyst for Suzuki-Miyaura reaction

The complex [PdCl₂(P-N)] containing the basic and sterically demanding 8-(di-tert-butylphosphinooxy)quinoline ligand (P-N) is a highly efficient catalyst for the coupling of phenylboronic acid with aryl bromides or aryl chlorides. The influence of solvent and base has been investigated, the highest rates being observed at 110 °C in toluene with K₂CO₃ as the base. With aryl bromides the reaction rates are almost independent on the electronic properties of the para aryl substituents, on the contrary, reduced reaction rates are observed when bulky substituents are present on the substrate. Nevertheless the coupling of 2-bromo-1,3,5-trimethylbenzene with phenylboronic acid can be carried out to completion in 2 h using a catalyst loading of 0.02 mol %. Under optimized reaction conditions, turnover frequencies as high as 1900 h⁻¹ can be obtained in the coupling of 4-chloroacetophenone with phenylboronic acid; lower reaction rates are obtained with substrates bearing EDG substituents on the aryl group.     

Practical synthesis of 6-aryluridines via palladium(II) acetate catalyzed Suzuki-Miyaura cross-coupling reaction

Sugar-protected 6-halouridine derivatives underwent Suzuki-Miyaura cross-coupling reactions with arylboronic acids in the presence of palladium(II) acetate as a catalyst, triphenylphosphine as a ligand, and sodium carbonate as a base. This methodology is applicable to both the C5- and C6-position of uridine and provides a direct access for versatile uridine derivatives.     

Ferrocenylimidazoline palladacycles: efficient phosphine-free catalysts for Suzuki-Miyaura cross-coupling reaction

A series of new ferrocenylimidazoline ligands 5 with different substituents in the imidazoline ring and their corresponding cyclopalladated complexes 6 were synthesized. Chloride-bridged palladacycle dimers 6, which are thermally stable and insensitive to air and moisture, have been evaluated as effective phosphine-free catalysts for the Suzuki reaction of aryl bromides with arylboronic acid. The catalyst 6b presents the highest efficiency in the coupling processes for less reactive 2-bromothiophene. Moreover, the reactions can be carried out at room temperature under aerobic conditions to give the corresponding biaryls in high yields. Additionally, the triphenylphosphine adduct of cyclopalladated ferrocenylimidazoline 7a was structurally characterized by single-crystal X-ray diffraction.