New dialkylenetriamine zinc complexes as highly efficient ROP catalysts

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Phosphoraneiminato tungsten alkylidyne complexes as highly efficient alkyne metathesis catalysts

The tungsten neopentylidyne complexes [Me₃CCW(NPR₃){OCMe(CF₃)₂}₂] (3a, R = Cy; 3b, R = iPr) were prepared in excellent yields by the reaction of the solvate complex [Me₃CCW{OCMe(CF₃)₂}₃(DME)] (DME = 1,2-dimethoxyethane) with equimolar amounts of the corresponding phosphoraneiminato lithium species R₃PNLi (R = Cy, iPr) at room temperature. The products were characterized by ¹H, ¹³C{¹H}, ¹⁹F{¹H} and ³¹P{¹H} NMR spectroscopy and elemental analysis. Single crystals of both complexes were obtained from diethyl ether solutions at −35 °C, and the molecular structures were determined by X-ray diffraction analysis. Complexes 3a and 3b are able to efficiently catalyse alkyne cross-metathesis (ACM) of 3-pentynyl benzyl ether (4) and ring-closing alkyne metathesis (RCAM) of bis(3-pentynyl)adipate (6) at room temperature and with low catalyst loadings (1 or 2 mol%) to afford the diether 5 and the cyclic diester 7 in virtually quantitative yields. The reactions were carried out in the presence of molecular sieve 5 Å to adsorb 2-butyne during the metathesis.     

Robust acenaphthoimidazolylidene palladium complexes: highly efficient catalysts for suzuki-miyaura couplings with sterically hindered substrates

Robust acenaphthoimidazolylidene palladium complexes have been demonstrated as highly efficient and general catalysts for the sterically hindered Suzuki-Miyaura cross-coupling reactions in excellent yields even with low catalyst loadings under mild reaction conditions. The high catalytic activity of these complexes highlights that, besides the "flexible steric bulky" concept, σ-donor properties of the NHC ligands are also crucial to accelerate the transformations.     

Orthopalladated triarylphosphite complexes as highly efficient catalysts in the Heck reaction

An orthopalladated complex of commercially available tris(2,4-di-tert-butylphenyl)phosphite proves to be an extremely active catalyst in the Heck arylation of alkenes, with turnover numbers of up to 5,750,000 (mol product.mol Pd⁻¹) and turnover frequencies of up to nearly 300,000 (mol product.mol Pd⁻¹.h⁻¹).     

Bis(diphosphaferrocene) palladium(II) dimer complexes as efficient catalysts in the synthesis of arylboronic esters

Bis(diphosphaferrocenes)PdCl₂ dimers efficiently catalyse cross-coupling reactions between aryl iodides and pinacol borane in dioxane at 80 °C to afford the corresponding aryl boronic esters derivatives in excellent yields.     

Aziridine ring-containing chiral ligands as highly efficient catalysts in asymmetric synthesis

Enantiomerically pure bidentate heteroorganic ligands built on an achiral skeleton containing hydroxyl and aziridine moieties as nucleophilic centers, capable of binding various organometallic reagents, have proven to be highly efficient catalysts in the enantioselective addition of diethylzinc and phenylethynylzinc to aryl and alkyl aldehydes to give the desired chiral products in high chemical yields (up to 90%) and with ees of up to 95%. The influence of the stereogenic center located in the carbon atom in the aziridine moiety on the stereochemical course of the reaction is reported.     

叔胺类环钯化合物在催化Heck反应的应用

首次报道了叔胺类环钯化合物1～4在催化Heck反应中的应用。实验表明该类化合物能高效地催化Heck反应;其中催化剂4的TON值(产品摩尔数与钯摩尔数的比值)和TOF值(产品摩尔数与钯摩尔数以及反应时间的比值)分别高达9.6×10^6和8.7×10^5)。这上迄今为止催化Heck反应的最好结果。     

The polymer incarcerated method for the preparation of highly active heterogeneous palladium catalysts

A new method named "the polymer incarcerated (PI) method" for preparing a heterogeneous palladium catalyst has been developed. The method is operationally simple, and the Pd catalyst prepared (PI Pd) is highly active for hydrogenation, carbon-carbon, and carbon-oxygen bond-forming reactions. Remarkable points are that the activity of PI Pd is higher than that of homogeneous Pd catalysts and that PI Pd is recovered by simple filtration and reused several times without loss of activity. The catalyst is expected to replace many heterogeneous palladium catalysts, especially Pd/C, which is often used in academia and industry, but recovery of which is difficult.     

A highly efficient general synthesis of phosphine-borane complexes

A general synthesis of phosphine-borane complexes proceeding in high yield in a safe, green process from borane generated in situ from sodium borohydride is described. The procedure also allows simultaneous carbonyl reduction and phosphine-borane formation on air-sensitive bulky phosphine derivatives.     

The first insoluble polymer-bound palladium complexes of 2-pyridyldiphenylphosphine: highly efficient catalysts for the alkoxycarbonylation of terminal alkynes

Palladium complexes of 2-pyridyldiphenylphosphine anchored on polystyrene, polymethylmethacrylate and styrene-methylmethacrylate copolymer form highly active heterogeneous catalysts for the alkoxycarbonylation of terminal alkynes with activities approaching those obtained under homogeneous conditions.     

Suzuki-Miyaura coupling on heterogeneous palladium catalysts

Summary Five supported heterogeneous Pd catalysts have been prepared, characterized and found to be active and selective in the Suzuki-Miyaura coupling of boronic acids, and aromatic iodo and bromo compounds to form the corresponding biaryls in high selectivities. Reaction conditions, namely, the solvent, base (triethylamine, Na₂CO₃, Cs₂CO₃) and tetrabutylammonium chloride as an additive are shown to have profound effects on catalyst performance.</o:p>     

The air-stable and highly efficient P, N-chelated palladium(II) complexes as catalysts for the Suzuki cross-coupling reaction at room temperature

Two air-stable P, N-chelated palladium(II) complexes have been evaluated as highly efficient and simple catalysts for Suzuki cross-coupling reaction between aryl bromides and arylboronic acids. They exhibit high activity and selectivity at room temperature.     

Hydrogen-bonding 2D metal-organic solids as highly robust and efficient heterogeneous green catalysts for Biginelli reaction

Two new Zn(II) and Cd(II) MOFs have been synthesized. These MOFs have been applied as heterogeneous catalysts for the green synthesis of a variety of dihydropyrimidinone derivatives through the Biginelli reaction and the desired products were obtained in high yields with short reaction time under mild solvent-free conditions. Moreover, the MOF catalysts may be readily recovered after the reaction and reused for many cycles.     

Transition metal complexes on mesoporous silica nanoparticles as highly efficient catalysts for epoxidation of styrene

We have synthesized a series of catalysts for epoxidation of styrene by immobilizing salicylaldimine transition metal (copper, manganese, and cobalt) complexes on mesoporous silica nanoparticles (MSNs) with diameters of 120-150 nm. The prepared catalysts are characterized by infrared (IR) spectra, thermal gravimetric analyses (TGA), inductively coupled plasma (ICP), CHN elemental analysis, nitrogen adsorption-desorption, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). These catalysts possess excellent catalytic efficiency in epoxidation of styrene when using tert-BuOOH (TBHP) as oxidant. Styrene shows a high conversion (～99%) as well as epoxide selectivity (～80%) over Cu-MSN catalysts, and high conversion (～99%) and moderate epoxide selectivity (～65%) over Mn-MSN and Co-MSN catalysts. The recycling experiment results indicate that these catalysts maintain catalytic activity even after being used for three cycles. Our results indicate that MSNs can serve as better catalyst supports.     

Novel trans-spanned palladium complexes as efficient catalysts in mild and amine-free cyanation of aryl bromides under air

[reaction: see text] The use of a novel trans-spanned palladium complex as an efficient and selective catalyst in the cyanation of aryl halides is described. The suggested reaction conditions are mild, exhibit good scope of substrates, and circumvent the need for an inert atmosphere and amine co-ligands.     

Silica-supported polymeric palladium (0) complexes as catalysts for Heck reaction in organic synthesis

Silica-supported palladium (0) complexes have been prepared from γ-chloropropyl triethoxysilica and γ-aminopropyl triethoxysilica via immobilization on fumed silica, followed by reacting with ethylenediamine and salicylaldehyde, and then the reaction with palladium chloride in ethanol and reduction with KBH₄ in ethanol. They are efficient catalysts for Heck reaction of aryl iodides with alkene at 90^oC. These polymeric palladium (0) catalysts can be recovered and reused without loss in activity. This revised version was published online in June 2006 with corrections to the Cover Date.     

The use of palladium complexes in highly selective multistep organic synthesis

Palladium complexes are versatile catalysts for the selective construction of organic molecules. The use of a model system containing a norbornyl-palladium bond stable toward -hydrogen elimination allows the formation of a variety of molecules. Carbon monoxide is a particularly advantageous building block in these multistep reactions, because it helps to induce the formation of various types of carbon-carbon bonds. Some palladium-catalyzed multistep reactions, which proceed in sequence and have a common initial step,i.e., oxidative addition, are described.This review is based on material from a report delivered at the conference INEOS-94: The Modern Problems of Organometallic Chemistry (May 21–27, 1994, Moscow).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 412–420, March, 1995.     

Ultrasound-promoted green synthesis of 1,4-dihydropyridines using fuctionalized MWCNTs as a highly efficient heterogeneous catalyst

A new method for multi-component synthesis of 1,4-dihydropyridine derivatives (1,4-DHPs) in the presence of meglumine supported on multiwalled carbon nanotubes (MWCNTs@meglumine) as a new heterogeneous, highly efficient and reusable catalyst was investigated. The reaction was performed under ultrasonic irradiation in EtOH at room temperature. A new, highly efficient heterogeneous catalyst, short reaction times, high to excellent yield of products, and safe and clean conditions are the advantages of the presented method.