N-N二座配位パラジウム(II)を用いたHeck反応の触媒サイクルと配位子効果に関する理論的研究

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Immobilization of Pd(0) nanoparticles on polyaza-ligand-functionalized polyacrylonitrile fiber as highly active catalyst for the Heck reaction

A gold-catalyzed Heck reaction of aryl and styryl iodides with styrenes was developed. The hemilabile P,N-ligand-assisted gold-catalyzed C(sp2)-C(sp2) cross-coupling can synthesize stilbenes and bistyryl complexes, with good functional-group tolerance and mild conditions. The elementary organometallic steps of migratory insertion and β-hydride elimination might be involved in this ligand-enabled Au(I)/Au(III)-catalyzed Heck reaction with styrenes.

1-(2-Iodophenyl)-1H-tetrazole as a ligand for Pd(II) catalyzed Heck reaction

As part of pharmacological-phytochemical in- tegrated studies of medicinal plants from Indian flora, costunolide (1) was isolated as a major compound from Saussurea lappa, plant traditionally used in different Asian traditional medicine systems. To improve the efficacy of this natural product lead, a series of analogues have been synthesized by the coupling of various aryl iodides using the standard Heck reaction conditions and evaluated for their cytotoxic activities against human cancer cell lines. The results indicated that several of the analogues were effective against the tested cell lines compared to the parent compound costunolide. Among the tested com- pounds, 2c and 2j demonstrated good activity against Hela cell line while compounds 2d showed potent activity against DU-145 and MCF-7 cell lines, respectively. Graphical Abstract A series of costunolide derivatives have been synthesized by Pd(II)-catalyzed Heck reaction and were studied for their cytotoxic properties against the panel of human cancer cell lines (B-16, DU-145, Hela, A549, MCF-7).

N-P二座配位のパラジウム(？U)触媒を用いたHeck反応に関する理論的研究

Mechanism of ketone hydrosilylation by Cu(I) catalysts: A theoretical study

Predicting the catalytic efficiency by quantum-chemical descriptors: Theoretical study of pincer metallic complexes involved in the catalytic Heck reaction

Ligand-free indium(III)-catalyzed Heck reaction

ChemInform 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 complexes containing an o-phenylene-derived amido diphosphine ligand efficiently catalyze the Heck olefination of a wide array of aryl halides, leading to extremely high turnover numbers of up to 4.5 × 107.

Preparation of the 5-substituted azepino[3,4-b]indole core structure can be realised through a catalytic Heck reaction. The scope and limitations of this methodology are reported. The reactivity of di-tert-butyl 5-ethoxycarbonylmethylene-1,3,4,5-tetrahydro-1-oxoazepino[3,4-b]indole-2,10-dicarboxylate (1) was investigated in order to prepare the indole analogue of hymenialdisine and derivatives.

The first theoretical study on the effects of ligands on the mechanism, reactivities, and regioselectivities of Rh(I)-catalyzed (5 + 2) cycloadditions of vinylcyclopropanes (VCPs) and alkynes has been performed using density functional theory (DFT) calculations. Highly efficient and selective intermolecular (5 + 2) cycloadditions of VCPs and alkynes have been achieved recently using two novel rhodium catalysts, [Rh(dnCOT)](+)SbF(6)(-) and [Rh(COD)](+)SbF(6)(-), which provide superior reactivities and regioselectivities relative to that of the previously reported [Rh(CO)(2)Cl](2) catalyst. Computationally, the high reactivities of the dnCOT and COD ligands are attributed to the steric repulsions that destabilize the Rh-product complex, the catalyst resting state in the catalytic cycle. The regioselectivities of reactions with various alkynes and different Rh catalysts are investigated, and a predictive model is provided that describes substrate-substrate and ligand-substrate steric repulsions, electronic effects, and noncovalent π/π and C-H/π interactions. In the reactions with dnCOT or COD ligands, the first new C-C bond is formed proximal to the bulky substituent on the alkyne to avoid ligand-substrate steric repulsions. This regioselectivity is reversed either by employing the smaller [Rh(CO)(2)Cl](2) catalyst to diminish the ligand-substrate repulsions or by using aryl alkynes, for which the ligand-substrate interactions become stabilizing due to π/π and C-H/π dispersion interactions. Electron-withdrawing groups on the alkyne prefer to be proximal to the first new C-C bond to maximize metal-substrate back-bonding interactions. These steric, electronic, and dispersion effects can all be utilized in designing new ligands to provide regiochemical control over product formation with high selectivities. The computational studies reveal the potential of employing the dnCOT family of ligands to achieve unique regiochemical control due to the steric influences and dispersion interactions associated with the rigid aryl substituents on the ligand.

The present study reports the evidence for the multiple carbon-carbon bond insertion into the metal-heteroatom bond via a five-coordinate metal complex. Detailed analysis of the model catalytic reaction of the carbon-sulfur (C-S) bond formation unveiled the mechanism of metal-mediated alkyne insertion: a new pathway of C-S bond formation without preliminary ligand dissociation was revealed based on experimental and theoretical investigations. According to this pathway alkyne insertion into the metal-sulfur bond led to the formation of intermediate metal complex capable of direct C-S reductive elimination. In contrast, an intermediate metal complex formed through alkyne insertion through the traditional pathway involving preliminary ligand dissociation suffered from "improper" geometry configuration, which may block the whole catalytic cycle. A new catalytic system was developed to solve the problem of stereoselective S-S bond addition to internal alkynes and a cost-efficient Ni-catalyzed synthetic procedure is reported to furnish formation of target vinyl sulfides with high yields (up to 99%) and excellent Z/E selectivity (>99:1).

The conversion of allylic alcohols to enols mediated by Fe(CO)(3) has been studied through density functional theoretical calculations. From the results obtained a complete catalytic cycle has been proposed in which the first intermediate is the [(allyl alcohol)Fe(CO)(3)] complex. This intermediate evolves to the [(enol)Fe(CO)(3)] complex through two consecutive 1,3-hydrogen shifts involving a pi-allyl hydride intermediate. The highest Gibbs energy transition state corresponds to the partial decoordination ot the enol ligand prior to the coordination of a new allyl alcohol molecule that regenerates the first intermediate. Alternative processes for the [(enol)Fe(CO)(3)] complex such as [Fe(CO)(3)]-mediated enol-aldehyde transformation and enol isomerization have also been considered. The results obtained show that the former process is unfavourable, whereas the enol isomerization may compete with the enol decoordination step of the catalytic cycle.