Aryl Coupling Reactions Research Articles

Recent Developments in Catalytic Aryl Coupling Reactions

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

A regioselective palladium-free protocol for accessing unsymmetrical biaryls through ring transformation of 6-aryl-α-pyrones

A regioselective synthesis of unsymmetrical biaryls with electron withdrawing or donating substituents is described and illustrated by carbanion-induced ring transformation of 6-aryl-α-pyrones with methoxyacetone in excellent yield. Our methodology is an alternative to classical organometal-catalyzed aryl–aryl coupling reactions and can be applied to the synthesis of functionally demanding naphthyl biaryls for the development of new ligands for asymmetric synthesis.

Recent Developments in Catalytic Aryl Coupling Reactions

AbstractThe present microreview is aimed at describing the evolution of the methodology used in aryl coupling reactions towards catalytically efficient and highly selective procedures, which have been achieved through the use of assisted and metallacycle‐directed reactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

PEG-Coated Mesoporous Silica-Supported Pd for the Suzuki-Miyaura Coupling Reaction

Poly(ethylene glycol)-coated SBA-15 mesoporous silica-supported palladium complex 1 was prepared and used as a catalyst in Suzuki-Miyaura coupling reaction. The mesoporous silica-supported palladium complex 1 was prepared by the reaction of Pd(PPh3)4 with poly(ethylene glycol)-coated SBA-15 (eq. 1). The Suzuki coupling reaction of aryl and alkenyl halides with aryl boronic acids took place in water in the presence of 0.001-0.1 mol% palladium of the catalyst 1 to give the coupling products in 66-98% yield (eq. 2). The catalyst 1 was reused without significant loss of catalytic activity (5 reuses, 89-92% yield).

Pyridin‐, Quinolin‐ and Acridinylidene Palladium Carbene Complexes as Highly Efficient C–C Coupling Catalysts

AbstractA series of four new complexes bearing N‐heterocyclic carbene ligands (NHCs) as well as four compounds bearing N‐heterocyclic carbene ligands with remote heteroatoms (rNHCs) of the general types [(NHC)(PPh3)2PdCl]+BF4− and [(rNHC)(PPh3)2PdCl]+BF4−, respectively, have been prepared in high yields. Crystal and molecular structures have been determined for four representative examples. These compounds proved to be efficient catalysts for aryl coupling reactions of the Heck and Suzuki types (reaching TONs of as high as 6,200,000). Both aryl bromides and aryl chlorides can be used as substrates. Like the well known mixed, standard (NHC)(phosphine) compounds, the new six‐numbered, one‐N‐heterocyclic carbene complexes (and in particular certain rNHC‐containing ones) also combine the advantageous stability of bis(carbene) and the high activity of bis(phosphine) complexes. Furthermore, their good catalytic performance and, especially, their easy synthesis based on cheap and commercially available starting materials, make them by far superior when compared to the mixed (NHC)(phosphine) catalysts known thus far.

Aryl Palladium Carbene Complexes and Carbene—Aryl Coupling Reactions.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Palladium‐Catalyzed C–S Bond Formation: Rate and Mechanism of the Coupling of Aryl or Vinyl Halides with a Thiol Derived from a Cysteine

AbstractThe mechanism of the palladium‐catalyzed coupling reaction of aryl or vinyl halides with a thiol derived from a protected chiral cysteine 1 (RSH), leading to C–S bond formation, has been investigated in the context of catalytic reactions. All palladium complexes involved in the catalytic cycle have been characterized, successively, as PhPdI(dppf), PhPdI(SHR)(η1‐dppf) and PhPd(SR)(dppf). The oxidative addition reaction which generates PhPdI(dppf) is followed by the metallation of 1 whose mechanism has been investigated. In the case of the weakly acidic cysteine 1 (RSH) studied here, the anions RS– are not generated in detectable concentrations in the reaction with the NEt3 base. Even if the classical transmetallation reaction of PhPdI(dppf) by RS–, present at a very low concentration, cannot be entirely excluded, we propose that an alternative mechanism, complexation of the thiol, leads to the previously unreported PhPdI(SHR)(η1‐dppf) (observed by 31P NMR spectroscopy) after decomplexation of one of the phosphorus atoms of the dppf ligand, followed by the easier deprotonation of the coordinated RSH by the base, which generates PhPd(SR)(dppf). A classical reductive elimination reaction delivers the coupling product PhSR. The kinetics of all the steps have been investigated independently, one after the other, starting from Pd2(dba)3 and dppf, using the initial concentrations of the reagents used in the catalytic reaction. Under the experimental conditions used in the catalytic reaction involving phenyl iodide and NEt3 as the base, the reductive elimination reaction is the slowest step which mainly limits the rate of the catalytic cycle up to approximately 80 % conversion. The metallation reaction of RSH is very slow when propylene oxide was used as the probase. The reductive elimination is the slowest step in the cross‐coupling of a vinyl iodide. Diastereoisomers of the vinyl‐PdX(dppf) (X = I, SR) complexes were observed as a result of the atropisomerism induced by the bulkiness of the investigated vinyl group and the chiral center present on the vinyl or on the SR group. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Catalysts for Suzuki—Miyaura Coupling Processes: Scope and Studies of the Effect of Ligand Structure.

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Palladium‐Catalyzed Inter‐ and Intramolecular Coupling Reactions of Aryl and Vinyl Halides Mediated by Indium.

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Nickel‐Catalyzed Electrochemical Coupling of Aryl, Heteroaryl or Vinyl Halides with Activated Alkyl Chlorides: Synthetic and Stereochemical Aspects

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Catalysts for Suzuki−Miyaura Coupling Processes: Scope and Studies of the Effect of Ligand Structure

Suzuki-Miyaura coupling reactions of aryl and heteroaryl halides with aryl-, heteroaryl- and vinylboronic acids proceed in very good to excellent yield with the use of 2-(2',6'-dimethoxybiphenyl)dicyclohexylphosphine, SPhos (1). This ligand confers unprecedented activity for these processes, allowing reactions to be performed at low catalyst levels, to prepare extremely hindered biaryls and to be carried out, in general, for reactions of aryl chlorides at room temperature. Additionally, structural studies of various 1.Pd complexes are presented along with computational data that help elucidate the efficacy that 1 imparts on Suzuki-Miyaura coupling processes. Moreover, a comparison of the reactions with 1 and with 2-(2',4',6'-triisopropylbiphenyl)diphenylphosphine (2) is presented that is informative in determining the relative importance of ligand bulk and electron-donating ability in the high activity of catalysts derived from ligands of this type. Further, when the aryl bromide becomes too hindered, an interesting C-H bond functionalization-cross-coupling sequence intervenes to provide product in high yield.

Biphasic Suzuki coupling reactions of aryl or benzyl bromides employing cobalt-containing phosphine ligand coordinated palladium complex

Biphasic Suzuki-coupling reactions of aryl and benzyl bromides employing a cobalt-containing phosphine ligand chelated palladium complex 2 were carried out in various reaction conditions. Comparisons of the catalytic efficiencies in the presence/absence of a phase-transfer agent, TBAB, were presented. In addition, the effects of altering solvents, temperatures, catalysts, and substrates on the reactions were monitored and reported. Better yields were commonly observed while a phase-transfer agent TBAB was participated in the reactions. The factor of reaction time is more crucial than that of temperature in short reaction hour experiments. Obviously, an induction period for the reduction of Pd(II) to Pd(0) active species is needed for this type of reaction.

A Highly Effective (Triphenyl phosphite)palladium Catalyst for a Cross—Coupling Reaction of Allylic Alcohols with Organoboronic Acids.

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Palladium-Catalyzed Inter- and Intramolecular Coupling Reactions of Aryl and Vinyl Halides Mediated by Indium

Treatment of aryl and vinyl halides with 50 mol % of 100 mesh indium, 2.5 mol % of Pd-C, and 1.5 equiv of LiCl under mild conditions (DMF, 100 degrees C, 1-3 h) could produce coupling products efficiently in good to excellent yields in which the C(sp2)-C(sp2) bond was formed. This reagent worked equally well with both intermolecular and intramolecular coupling reactions, producing a variety of biaryls, 1,3-dienes, and cyclic compounds.

A Highly Effective (Triphenyl phosphite)palladium Catalyst for a Cross−Coupling Reaction of Allylic Alcohols with Organoboronic Acids

AbstractThe cross coupling reaction of aryl and vinyl boronic acids and allylic alcohols proceeded smoothly in toluene or dioxane in the presence of a (triphenyl phosphite)palladium catalyst to give the corresponding allylbenzene derivatives and 1,4‐dienes. Neither cocatalysts for promoting C−O bond cleavage of allylic alcohols nor bases for activation of organoboron reagents are required for promoting the coupling process. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

New Developments in the Synthesis of Heterotopic Atropisomeric Diphosphines via Diastereoselective Aryl Coupling Reactions.

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A Highly Efficient Microwave‐Assisted Suzuki Coupling Reaction of Aryl Perfluorooctylsulfonates with Boronic Acids.

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New developments in the synthesis of heterotopic atropisomeric diphosphines via diastereoselective aryl coupling reactions

The new heterotopic atropisomeric diphosphine ( R)-5,6-benzo-2,2′-bis(diphenylphosphino)-4′,5′,6′-trimethylbiphenyl has been prepared. The key step of this synthesis is a diastereoselective, intramolecular aryl–aryl coupling reaction via oxidation of a suitable, chiral diarylcuprate. The catalytic properties of the diphosphine in ruthenium promoted hydrogenations of model substrates and in rhodium promoted 1,4-additions of boronic acids to α,β-unsaturated ketones are fully comparable to those of reference ligands such as BINAP. This seems to indicate that C 2-symmetry is not a structural prerequisite for atropisomeric chiral diphosphines to obtain high enantioselectivities in 1,4-addition reactions as well as in hydrogenation reactions.

Pentamethylcyclopentadienylruthenium(II) Complexes: Synthesis, Characterization and Catalytic Activity in Aryl–Aryl Coupling

Ruthenium(II) complexes of the type [Ru(PPh3)(η5-C5Me5)L] have been synthesized by the reactions of [RuCl(PPh3)2(η5-C5Me5)] with Schiff bases having the (N, O) donor atoms. The Schiff bases used in this study were prepared by condensing the appropriate aniline with salicylaldehyde or 2-hydroxy-1-naphthaldehyde in a 1:2 molar ratio respectively. The complexes were characterized by analytical, spectral (i.r., electronic and 1H-n.m.r.) data. The new complexes have been used as catalysts in aryl–aryl coupling reactions.

A highly efficient microwave-assisted suzuki coupling reaction of aryl perfluorooctylsulfonates with boronic acids.

[reaction: see text] A new strategy to improve the efficiency of Suzuki coupling reactions is introduced by combining fast microwave reaction with easy fluorous separation. Aryl perfluorooctylsulfonates derived from the corresponding phenols are coupled with aryl boronic acids to form biaryls under general microwave conditions. Both intermediates and products are purified by solid-phase extraction over FluoroFlash silica gel. Application of this tagging strategy to multistep synthesis of biaryl-substituted hydantoin is also described.