Interplays between Reactions within and without the Catalytic Cycle of the Heck Reaction as a Clue to the Optimization of the Synthetic Protocol

Schmidt, Alexander F.; Halaiqa, A. Al; Смирнов, В. В.

doi:10.1055/s-2006-951527

Cited by 86 publications

(79 citation statements)

References 104 publications

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“…[93,94] It is highly probable that in these cases the Heck coupling reaction proceeds through the oxidative addition of the aryl halide on the nanoparticles surface, and the oxidized Pd species thus formed are detached from the surface and enter into the main catalytic cycle. [95] The Pd 0 formed in the main catalytic cycle, after bhydride and reductive elimination steps, can either continue in the catalytic cycle or fall back to the nanoparticle reservoir. [67] The same behavior was observed in the hydroformylation of olefins catalyzed by Rh 0 nanoparticles prepared in BMI·PF 6 .…”

Section: Catalytic Reactionsmentioning

confidence: 99%

Catalytic Applications of Metal Nanoparticles in Imidazolium Ionic Liquids

Migowski

Dupont

2006

Chemistry A European J

432

241

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Metal nanoparticles (MNPs) with a small diameter and narrow size distribution can be prepared by H2 reduction of metal compounds or decomposition of organometallic species dissolved in ionic liquids (ILs). MNPs dispersed in ILs are catalysts for reactions under multiphase conditions. These soluble MNPs possess a pronounced surfacelike rather than single‐site like catalytic properties. In other cases the MNPs are not stable and tend to aggregate or serve as reservoirs of mononuclear catalytically active species.

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Section: Catalytic Reactionsmentioning

confidence: 99%

Catalytic Applications of Metal Nanoparticles in Imidazolium Ionic Liquids

Migowski

Dupont

2006

Chemistry A European J

432

241

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“…All of these species enter (and are interconverted by) the catalytic cycle. [16][17][18] However, the coupling activity is expected to decrease with the size of the Pd aggregates. Finally, the irreversible precipitation of Pd black will occur, shifting the equilibria b towards inactive species, and stalling catalytic activity.…”

Section: Introductionmentioning

confidence: 99%

“…[16,17] Typical means to prevent this deactivation are the addition of stabilizers (often in excess) for Pd(0), such as phosphane and carbene ligands. Other additives or solvents have been used to stabilize the Pd particles.…”

Section: Introductionmentioning

confidence: 99%

Macrocyclic Palladium(II) Complexes in CC Coupling Reactions: Efficient Catalysis by Controlled Temporary Release of Active Species

Röhlich¹,

Köhler²

2010

Adv Synth Catal

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Stabilization of palladium species against agglomeration is essential for reasonable catalytic activity in C À C coupling reactions. In contrast to common methods of palladium(0) complex or particle stabilization, a new concept is introduced here: it is demonstrated that a controlled release of palladium from an inactive precatalyst provides stability, too, and leads to high catalytic activity. This paper presents surprising catalytic results for Heck and Suzuki reactions with aryl chlorides and bromides, using three highly stable macrocyclic palladium complexes as catalyst precursors. Three different behaviour patterns for the macrocyclic complexes can be deduced from the evaluation of catalytic activities, UV-Vis spectroscopy, recycling studies of immobilized complexes, and ligand addition experiments. (i) Palladium tetraphenylporphyrin reversibly releases only extremely low amounts of palladium during the reactions, and low coupling activities are observed.(ii) Release of palladium from its phthalocyanine complex is irreversible; cumulative release of palladium into the reaction mixtures leads to high catalytic activity. (iii) Extraordinary results were obtained with a Robson-type complex of palladium, which reversibly releases effectual amounts of palladium into solution under reaction conditions. This controlled release prevents the formation of inactive palladium agglomerates under harsh conditions and leads to high catalytic performances. Even strongly deactivated electron-rich aryl chlorides (4-chloroanisole) can be completely and selectively converted by the in situ formed anionic palladium halide complexes; the addition of typical stabilizing additives (TBAB) was found to be unnecessary. The bimetallic palladium complex is regenerated at the end of the reaction. These results contribute to the current understanding of the active species in C À C coupling reactions of Heck and Suzuki types.

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“…A simple Heck reaction [12][13][14][15] of iodobenzene and methyl acrylate has been selected as a test reaction. Recently it was indicated that the pressurization with CO 2 accelerated the rate of Heck reactions with a Pd-TPP (TPP: triphenylphosphine) complex catalyst for a few selected substrates although the reactions took place in homogeneous liquid phases and CO 2 was not a reactant [16].…”

Section: Methodsmentioning

confidence: 99%

Carbon dioxide pressure induced heterogeneous and homogeneous Heck and Sonogashira coupling reactions using fluorinated palladium complex catalysts

Akiyama

Meng

Fujita

et al. 2009

The Journal of Supercritical Fluids

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The Heck reaction of iodobenzene and methyl acrylate was investigated with CO 2 -philic Pd complex catalysts having fluorous ponytails and the organic base triethylamine (Et 3 N) in the presence of CO 2 under solventless conditions at 80 C. The catalysts are not soluble in the organic phase in the absence of CO 2 and the reaction occurs in a solid-liquid biphasic system. When the organic liquid mixture is pressurized by CO 2 , CO 2 is dissolved into the organic phase and this promotes the dissolution of the Pd complex catalysts. As a result, the Heck reaction occurs homogeneously in the organic phase, which enhances the rate of reaction. This positive effect of CO 2 pressurization competes with the negative effect that the reacting species are diluted by an increasing amount of CO 2 molecules dissolved. Thus, the maximum conversion appears at a CO 2 pressure of around 4 MPa under the present reaction conditions. The catalysts are separated in the solid granules by depressurization and are recyclable without loss of activity after washing with n-hexane and/or water. When the washing is made with hexane alone, the catalytic activity tends to increase on the repeated Heck reactions, probably due to the accumulation of such a base adduct as Et 3 NHI on the catalysts. When the washing is further made with water, however, the base adduct is taken off from the catalysts and they show similar activity levels in the repeated runs. The potential of CO 2 pressure tunable heterogeneous/homogeneous reaction system has also been investigated for Sonogashira reactions of iodobenzene and phenylacetylene under similar conditions.

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Interplays between Reactions within and without the Catalytic Cycle of the Heck Reaction as a Clue to the Optimization of the Synthetic Protocol

Cited by 86 publications

References 104 publications

Catalytic Applications of Metal Nanoparticles in Imidazolium Ionic Liquids

Catalytic Applications of Metal Nanoparticles in Imidazolium Ionic Liquids

Macrocyclic Palladium(II) Complexes in CC Coupling Reactions: Efficient Catalysis by Controlled Temporary Release of Active Species

Carbon dioxide pressure induced heterogeneous and homogeneous Heck and Sonogashira coupling reactions using fluorinated palladium complex catalysts

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