53092-64-1

A magnetic palladium nickel carbon (Fe3O4@Pd@Ni/C) nanocomposite has been synthesized using a simple one-pot procedure via a hydrothermal approach. Ferric nitrate, palladium acetate, and nickel nitrate were dissolved in water together with glucose, and the mixture was heated in an autoclave. The Fe3O4@Pd@Ni/C nanocomposite was characterized via XRD, TEM, FE-SEM, VSM, EDS, and XPS studies. The catalytic abilities of the Fe3O4@Pd@Ni/C nanocomposite were investigated for the synthesis of distyrylbenzene and 9,10-distyrylanthracene derivatives. This method shows obvious advantages, such as the recyclability of the catalyst, simple experimental operation, and the obtaining of good to excellent yields.

In the past decades,para-terphenyls have been attracting tremendous attention due to their polymorphism and conformational diversity. In this work we report the synthesis, crystal structure, polymorphism and dielectric properties of two 2,2''-bis-substitutedpara-terphenyls: 2,2''-bis(hydroxymethyl)-para-terphenyl and 2,2''-bis(acetyloxymethyl)-para-terphenyl. On the basis of calorimetric and X-ray studies, we showed that the latter compound occurs in at least four polymorphic forms with melting points equal to 364, 345, 341 and 326 K, differentiated also in terms of thermodynamic stability and crystal symmetry. The most stable polymorph I is characterized by theP21/nspace group. 2,2''-Bis(hydroxymethyl)-para-terphenyl crystallizes in the monoclinicP21/cspace group. Both 2,2''-bis-substitutedpara-terphenyls can undergo vitrification, which is a highly exceptional feature for this class of chemical compounds and has not been reported before. Consequently, the molecular dynamics and conformational changes in the glassy and supercooled liquid states were analyzed by means of IR and broadband dielectric spectroscopy. Two relaxation processes were observed for both compounds: structural a-relaxation, connected with reorientational motions of molecules in supercooled liquid, and intermolecular ?-relaxation, ascribed to rotational motions of substituents of thepara-terphenyl skeleton. Taking into account the ongoing discussion about the conformational diversity of thepara-terphenyl skeleton, we showed that although free rotation of benzene rings is suppressed, the molecules in the glassy and liquid states can adopt both twisted and helical conformations, which results in diversity of the polymorphic forms.

Two N-heterocyclic carbene ligands provide orthogonal chemoselectivity during the Pd-catalyzed Suzuki-Miyaura (SM) cross-coupling of chloroaryl triflates. The use of SIPr [SIPr = 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene] leads to selective cross-coupling at chloride, while the use of SIMes [SIMes = 1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene] provides selective coupling at triflate. With most chloroaryl triflates and arylboronic acids, ligand-controlled selectivity is high (≥10:1). The scope of this methodology is significantly more general than previously reported methods for selective SM coupling of chloroaryl triflates using phosphine ligands. Density functional theory studies suggest that palladium's ligation state during oxidative addition is different with SIMes compared to SIPr.

The disclosure relates to the efficient preparation of aromatic hydrocarbons useful as intermediates for di-, tri-, tetra- and poly-dentate organophosphorus ligands having value in particular as hydroformylation catalysts. The use of triarylphosphine halide catalysts have been found to be more efficient in forming these intermediates by the use of excess triarylphosphine in an amount beyond what is required to form a coordination complex.

We report a direct cross-coupling reaction between diarylzinc (Ar2Zn) and aryltrimethylammonium salts (ArNMe3 +??OTf) in the presence of LiCl, via C?N bond cleavage. The reaction takes place smoothly upon heating in THF without any external catalyst, enabling an efficient and chemoselective formation of biaryl products. Mechanistic studies indicate that the reaction proceeds through a single electron transfer route.

A simple and efficient catalytic system for PdCl2 catalyzing the Suzuki-Miyaura reaction of dibromobenzene and arylboronic acid has been developed by using 3-(diphenylphosphino)propanoic acid as a ligand in dimethylsulfoxide at 100 °C. Using this method, a series of symmetrical terphenyl derivatives were obtained with remarkably good yields, up to 93%.

A simple and efficient catalytic system for Na2PdCl4 catalyzing the Suzuki-Miyaura reaction of dibromobenzene and arylboronic acid has been developed by using 2N2O-salen as a ligand in H2O/EtOH (V:V=4:1) at 100°C. Using this method, the reactions of substrates containing sterically demanding ortho substituents (e.g. dibromobenzene and/or arylboronic acids) proceeded efficiently, with the corresponding terphenyl derivatives being produced in moderate to excellent yields. Furthermore, this method offers interesting features for the multi-gram scale synthesis of terphenyl compound.

An efficient copper(I)-catalyzed coupling of triaryl and trialkylindium reagents with aryl iodides and bromides is reported. The reaction proceeds at low catalyst loadings (2 mol %) and generally only requires 0.33 equivalents of the triorganoindium reagent with respect to the aryl halide as all three organic nucleophilic moieties of the reagent are transferred to the products through consecutive transmetalations. The reaction tolerates a variety of functional groups and sterically hindered substrates. Furthermore, preliminary mechanistic studies that entailed the synthesis and characterization of potential reaction intermediates offered a glimpse of the elementary steps that constitute the catalytic cycle.

We present a direct cross-coupling reaction between arylaluminum compounds (ArAlMe2·LiCl) and organic halides RX (R=aryl, alkenyl, alkynyl; X=I, Br, and Cl) without any external catalyst. The reaction takes place smoothly, simply upon heating, thereby enabling the efficient and chemo-/stereoselective formation of biaryl, alkene, and alkyne coupling products with broad functional group compatibility.

A series of new imidazolium chlorides were straightforwardly prepared from the reactions between chloroacetone and imidazole derivatives. Deprotonation of the methylene proton next to the ketone group in these salts by pyridine led to the formation of a monodentate ligand that coordinated to palladium, readily forming zwitterionic anionic palladium pyridine complexes bearing a formal positive charge on the ligand ancillary. The pyridine ligand in the zwitterionic complexes can be facilely replaced by phosphine ligands. Seven of these new complexes were successfully characterized by X-ray crystallography. The zwitterionic phosphine complexes were highly efficient in catalyzing room-temperature Suzuki-Miyaura reactions between sterically hindered aryl chlorides and arylboronic acids in an aqueous medium.

Three novel [CNN]-pincer nickel(ii) complexes with NHC-amine arms were synthesized in three steps. Complex 5b was proven to be an efficient catalyst for the Kumada coupling of aryl chlorides or aryl dichlorides under mild conditions.

Direct cross-coupling between an arylzinc reagent and an aryl halide was accomplished without any external catalyst, enabling efficient and selective formation of the corresponding biaryl compound with broad functional group compatibility. Direct cross-coupling between a diarylzinc compound and an aryl iodide was accomplished without using any external catalyst. The reaction is efficient and selective, enabling formation of the corresponding biaryl compounds with broad functional group compatibility. The reaction is proposed to proceed by a thermally initiated single electron transfer (SET) route. Copyright

N-Heterocyclic carbene-based pincer nickel complexes were synthesized and characterized. These complexes efficiently catalyze cross-coupling of aryl Grignard reagents with aryl chlorides or fluorides under mild conditions.

The Suzuki cross-coupling reaction of various aryl and heteroaryl halides with arylboronic and heteroarylboronic acids was studied using a titania-supported palladium(0) catalyst at room temperature under air. The conversion and selectivity results obtained for many substrates were excellent and similar to those provided by more active or even homogeneous catalysts. The methodology is similarly effective using 2-bromo-3,4,5-trimethoxybenzaldehyde as the coupling partner and gave products in good yield. Furthermore, it has been shown that it is useful for the synthesis of terphenyl and tetraphenyls. The catalyst is quantitatively recovered from the reaction by simple filtration and reused for a number of cycles without significant loss of activity. Inductively coupled plasma (ICP) mass-spectrometric analysis of the filtrate from the reaction mixture demonstrated that the palladium metal hardly leached into the solution within the limits of the detector (1 ppm), thus suggesting that the present Suzuki-Miyaura reaction proceeded by heterogeneous catalysis. Copyright

P,N,O-chelate nickel complexes efficiently catalyse the cross-coupling reaction of aryl chlorides with arylzinc reagents in a 11 THF-NMP mixture. The reactions proceed at room temperature with low catalyst loading.

The nickel-catalyzed Negishi cross-coupling reaction of aryl chlorides with arylzinc compounds was investigated. The nickel complexes with the amido pincer type of ligands exhibited high catalytic activity and good functional group tolerance.

(Chemical Equation Presented) Ortho-substituted p-terphenyl hydrocarbons exist as trans and cis atropisomers that were identified by low-temperature NMR spectroscopy. The interconversion barriers increase with the dimensions of the ortho substituents, the experimental values being matched by ab initio calculations. X-ray diffraction shows that only the trans atropisomer is present in the solids. Spectra of a tert-butyl derivative in nonequilibrium conditions indicate that the cis is more populated than the trans atropisomer in solution, favored by attractive interactions.

The Suzuki cross-coupling reactions of phenyl-1,4-diboronic acid bis-pinacol ester with a range of aryl halides are reported. The reaction proceeded smoothly, even with sterically hindered aryl halides, to give symmetrical terphenyls often quantitatively.

A novel palladium-catalyzed reaction of aryldiazonium tetrafluoroborate salts with arylboronic esters furnishes cross-coupled products in moderate yields. The reaction proceeds at relatively mild temperatures and in aqueous media. (C) 2000 Published by Elsevier Science Ltd.

Reaction of 4-bromophenyl triflate (1) with phenylmagnesium bromide in the presence of 5 mol % of PdCl2(dppp) gave 97% yield of 4-bromobiphenyl (2a), which was formed by selective replacement of triflate in 1 by phenyl. On the other hand, bromide in 1 was substituted with the phenyl Grignard reagent selectively by use of PdCl2(meo-mop)2 to give 4-biphenyl triflate (3a) in high yield. The selective substitution was demonstrated to take place at the oxidative addition step to a palladium(0) species in a stoichiometric reaction of 1 with palladium(0) phosphine complexes.

The reactions of aryl Grignard reagents with p- and m-bromochlorobenzenes catalyzed by non-ligated NiCl2 give selectively chlorobiphenyl derivatives. By the stepwise reaction, an unsymmetrical terphenyl was synthesized in a good yield.

The reaction between aryl Grignard reagents and aryl halides in the presence of non-ligated nickel(II) chloride affords the cross-coupling products in high yields (60-98percent).

A one-pot route to p-terphenyls is described.Addition of 1,4-dibromo-2,5-diiodobenzene, 1, to excess aryl Grignard reagent gives the terphenyl di-Grignard 2 and the trihalo mono-Grignard 5.After aqueous quench, p-terphenyls are isolated in 30percent to 50percent yield (Table I).This yield can be improved to 70-80percent by adding potassium tert-butoxide or lithium tetramethylpiperidide to the reaction mixture prior to workup.Mechanisms involving organometallic aryne intermediates are proposed.With o-bromoiodoarenes in place of tetrahaloarenes the method can be adapted to prepare unsymmetric biaryls in good yield (Table II).

Phane skeletons containing para-terphenyl units have been synthesized.Substituent effects on conformative movements can be investigated by DNMR spectroscopy.