Application of a diphosphinidenecyclobutene ligand in the solvent-free copper-catalysed amination reactions of aryl halides

1,2-Diphenyl-3,4-bis[(2,4,6-tri-tert-butylphenyl)phosphinidene]cyclobutene was used as an additive ligand in copper-catalysed amination reactions of halobenzenes with amines in the presence of base to afford the corresponding secondary or tertiary amines in good to excellent yields.     

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.     

Cross-coupling reactions catalyzed by P, O chelate palladium complexes at room temperature

A new catalytic system based on P, O chelate palladium complexes for cross-coupling reactions is described. These catalysts have all shown high activity and selectivity under mild reaction condition.     

Aminoarenethiolate-copper(I)-catalyzed amination of aryl bromides

[reaction, structure: see text] Aminoarenethiolate-copper(I) complexes are known to be efficient catalysts for carbon-carbon bond formation. Here, we show the first examples that these thiolate-copper(I) complexes are efficient for carbon-nitrogen bond formation reactions as well. N-Arylation of benzylamine and imidazole with bromobenzene was achieved either in NMP as solvent or under solvent-free conditions in the presence of 2.5 mol % of aminoarenethiolate-copper(I) complex only.     

Palladium-catalyzed amination of aryl and heteroaryl tosylates at room temperature

Mild palladium-catalyzed aminations of aryl tosylates and the first aminations of heteroaryl tosylates are described. In the presence of the combination of L2Pd(0) (L = P(o-tol)3) and the hindered Josiphos ligand CyPF-t-Bu, a variety of primary alkylamines and arylamines react with both aryl and heteroaryl tosylates at room temperature to form the corresponding secondary arylamines in high yields with complete selectivity for the monoarylamine. These reactions at room temperature occur in many cases with catalyst loadings of 0.1 mol % and 0.01 mol % in one case, constituting the most efficient aminations of aryl tosylates by nearly 2 orders of magnitude. This catalyst is made practical by the development of a convenient method to synthesize the L2Pd(0) precursor. This complex is stable to air as a solid. In contrast to conventional relative rates for reactions of aryl sulfonates, the reactions of aryl tosylates are faster than parallel reactions of aryl triflates, and the reactions of aryl tosylates are faster than parallel or competitive reactions of aryl chlorides.     

Palladium-catalyzed amination of aryl bromides with hindered N-alkyl-substituted anilines using a palladium(I) tri-tert-butylphosphine bromide dimer

An efficient palladium-catalyzed amination of aromatic bromides with hindered N-alkyl-substituted anilines is described, either using the combination of Pd(OAc)(2) and P(t-Bu)(3) or a palladium(I) tri-tert-butylphosphine bromide dimer, [Pd(mu-Br)(t-Bu(3)P)](2), a new, commercially available, and easily handled catalyst.     

Heck reactions of 2-substituted enol ethers with aryl bromides catalysed by a tetraphosphine/palladium complex

cis,cis,cis-1,2,3,4-Tetrakis(diphenylphosphinomethyl)cyclopentane/[PdCl(C₃H₅)]₂ efficiently catalyses the Heck reaction of β-substituted enol ethers with aryl bromides. Employing β-methoxystyrene, 3-ethoxyacrylonitrile or methyl 3-methoxyacrylate, the regioselective α-arylation of these enol ethers was observed in all cases, and mixtures of Z and E isomers were generally obtained, which in many cases yielded a single ketone product after acid treatment. The stereoselectivity of this reaction depends on steric and electronic factors, and better stereoselectivities in favour of Z isomers were observed with electron-rich or sterically congested aryl bromides. Better yields were obtained for this reaction with electron-rich or sterically congested aryl bromides than with electron-poor aryl bromides. This observation suggests that with these β-substituted enol ethers the rate-limiting step of the catalytic cycle is not the oxidative addition of the aryl bromide to the palladium complex.     

Novel method for the synthesis of enamines by palladium catalyzed amination of alkenyl bromides

The intermolecular palladium catalyzed cross-coupling reaction between secondary amines and alkenyl bromides is described for the first time, giving rise to enamines with very high yields and regioselectivity.     

Solvent free,palladium catalyzed highly facile synthesis of diaryl disulfides from aryl thiols

An efficient solvent free Pd(pCH₂S)₂dba catalyzed green-chemical strategy for the synthesis of diaryl disulfides from aryl thiols in moderate to excellent yield is reported. Variety of diaryl disulfides were synthesized. The catalyst is recyclable up to four cycles.     

Reversal of aryl bromide reactivity in Pd-catalysed aryl amination reactions promoted by a hemilabile aminophosphine ligand

Incorporation of a hemilabile amino group with a bulky, electron-rich phosphorus ligand led to a reversal in the order of aryl bromide reactivity in Pd-catalysed aryl amination reactions.     

Heck reactions of aryl bromides with alk-1-en-3-ol derivatives catalysed by a tetraphosphine/palladium complex

cis,cis,cis-1,2,3,4-Tetrakis(diphenylphosphinomethyl)cyclopentane/[PdCl(C₃H₅)]₂ efficiently catalyses the Heck reaction of alk-1-en-3-ol with a variety of aryl bromides. In the presence of hex-1-en-3-ol or oct-1-en-3-ol, the β-arylated carbonyl compounds were selectively obtained. Linalool and 2-methylbut-3-en-2-ol led to the corresponding 1-arylalk-1-en-3-ol derivatives. Turnover numbers up to 69,000 can be obtained for this reaction. A minor electronic effect of the substituents of the aryl bromide was observed. Similar reaction rates were observed in the presence of activated aryl bromides such as bromoacetophenone and deactivated aryl bromides such as bromoanisole.     

Oxidative addition of aryl tosylates to palladium(0) and coupling of unactivated aryl tosylates at room temperature

Aryl tosylates are attractive substrates for Pd-catalyzed cross-coupling reactions, but they are much less reactive than the more commonly used aryl triflates. We report the oxidative addition of aryl tosylates to Pd(PPF-t-Bu)[P(o-tolyl)3] and to Pd(CyPF-t-Bu)[P(o-tolyl)3] at room temperature to produce the corresponding palladium(II) aryl tosylate complexes. In the presence of added bromide ions, arylpalladium(II) bromide complexes were formed. The rate of oxidative addition was accelerated by addition of either coordinating or weakly coordinating anions, and the reactions were faster in more polar solvents. The mild conditions for oxidative addition allowed for the development of Pd-catalyzed Kumada couplings and amination reactions of unactivated aryl tosylates at room temperature. The catalysts for these mild couplings of aryl tosylates were generated from palladium precursors and the sterically hindered Josiphos-type ligands that induced oxidative addition of aryl tosylates to Pd(0) at room temperature.     

Suzuki reactions catalyzed by palladium complexes bearing the bulky (2,6-dimesitylphenyl)dimethylphosphine

A new bulky and stable phosphine (2,6-dimesitylphenyl)dimethylphosphine, and representative palladium complexes have been prepared and structurally characterized; some of these complexes prove efficient for coupling of aryl chlorides with arylboronic acids.     

Application of a new bicyclic triaminophosphine ligand in Pd-catalyzed Buchwald-Hartwig amination reactions of aryl chlorides, bromides, and iodides

The new bicyclic triaminophosphine ligand P(i-BuNCH2)3CMe (3) has been synthesized in three steps from commercially available materials and its efficacy in palladium-catalyzed reactions of aryl halides with an array of amines has been demonstrated. Electron-poor, electron-neutral, and electron-rich aryl bromides, chlorides, and iodides participated in the process. The reactions encompassed aromatic amines (primary or secondary) and secondary amines (cyclic or acyclic). It has also been shown that the weak base Cs2CO3 can be employed with ligand 3, allowing a variety of functionalized substrates (e.g., those containing esters and nitro groups) to be utilized in our amination protocols. This ligand provides a remarkably general, efficient, and mild palladium catalyst for aryl iodide amination. Although 3 is slightly air and moisture sensitive, easy procedures can be adopted that avoid the need of a glovebox. Comparisons of the efficacy of 3 in these reactions with that of the proazaphosphatrane P(i-BuNCH2CH2)3N (2) reveal that in addition to the opportunity for transannulation in 2 (but not in 3), other significant stereoelectronic contrasts exist between these two ligands which help account for differences in the activities of the Pd/2 and Pd/3 catalytic systems.     

Cross-coupling reactions of aryl and vinyl chlorides catalyzed by a palladium complex derived from an air-stable H-phosphonate

A palladium complex derived from air-stable TADDOLP(O)H catalyzes efficiently Hiyama, Stille, Kumada and Suzuki cross-coupling reactions of aryl and vinyl chlorides.     

Polymer-supported DABCO–palladium complex as a stable and reusable catalyst for room temperature Suzuki–Miyaura cross-couplings of aryl bromides

Polymer-supported DABCO–palladium complex was observed as to be efficient and reusable catalytic system for the Suzuki–Miyaura cross-coupling reaction. In the presence of 0.25 mol % of the polymer-supported DABCO–palladium complex, a variety of aryl bromides were coupled with arylboronic acids efficiently in an aqueous ethanol at room temperature under air. Moreover, the reaction was very rapid, and the catalyst could be recovered readily from the reaction by simple filtration and could be reused at least five times.     

Coupling reactions of aryl bromides with 1-alkynols catalysed by a tetraphosphine/palladium catalyst

cis,cis,cis-1,2,3,4-Tetrakis(diphenylphosphinomethyl)cyclopentane/[PdCl(C₃H₅)]₂ system catalyses efficiently the coupling reactions of aryl halides with a variety of alkynols such as propargyl alcohol, but-1-yn-4-ol, pent-1-yn-5-ol or hex-1-yn-6-ol. The catalyst can be used at low loading. Higher reaction rates were observed in the presence of but-1-yn-4-ol, pent-1-yn-5-ol or hex-1-yn-6-ol than with propargyl alcohol. The protection of the alcohol functions as an ether or a silyloxy group led generally to similar or better results than the reactions performed with the unprotected alcohols.     

Pd(PhCN)(2)Cl(2)/P(t-Bu)(3): a versatile catalyst for Sonogashira reactions of aryl bromides at room temperature

[reaction: see text] Pd(PhCN)(2)Cl(2)/P(t-Bu)(3) serves as an efficient and a versatile catalyst for room-temperature Sonogashira reactions of aryl bromides.     

C-C coupling reactions of aryl bromides and arylsiloxanes in water catalyzed by palladium complexes of phosphanes modified with crown ethers

[reaction: see text] The complexes [PdCl2L2], where L is a crown-ether-containing triarylphosphane, catalyze the formation of biaryls from arylsiloxanes and aryl bromides with high yields in water as solvent and under air. The water-insoluble catalysts [PdCl2(PhCN)2] and [PdCl2(PPh3)2] are also efficient, although they decompose more quickly to form black Pd0.