scholarly journals Investigation of the effect of organic solvents on kinetic parameters in metal catalyzed reactions

2000 ◽  
Vol 65 (3) ◽  
pp. 201-206
Author(s):  
Ljiljana Trifkovic ◽  
Gordana Milovanovic
Keyword(s):  
Hydrogen Peroxide ◽  
Kinetic Parameters ◽  
Acid Oxidation ◽  
Carminic Acid ◽  
Pyrocatechol Violet ◽  
Free Activation Energy ◽  
S Oxidation ◽  
Catalyzed Reactions ◽  
Metal Catalyzed ◽  
Oxidation By Hydrogen Peroxide

The effects of acetone and acetonitrile on the kinetic parameters of azorubin S oxidation by hydrogen peroxide catalyzed by manganese(II), pyrocatechol violet oxidation by hydrogen peroxide catalyzed by copper(II), and carminic acid oxidation by hydrogen peroxide catalyzed by copper(II) and activated by bifenox, were examined. It was established that the examined solvents exhibit various effects on the kinetic parameters of the above said reactions. In all instances a change in the solvent concentration affects both the enthalpy and the entropy contributions to the free activation energy during the transition of the system into the active state, as well as the constant of the active complex formed at this point.

Monodentate Trialkylphosphines: Privileged Ligands in Metal-catalyzed Crosscoupling Reactions

2020 ◽  
Vol 24 (3) ◽  
pp. 231-264 ◽  
Author(s):  
Kevin H. Shaughnessy
Keyword(s):  
Transition Metal ◽  
Cross Coupling ◽  
Coupling Reactions ◽  
Cross Coupling Reactions ◽  
Aryl Bromides ◽  
Wide Range ◽  
Sterically Demanding ◽  
Transition Metal Catalyzed ◽  
Catalyzed Reactions ◽  
Metal Catalyzed

Phosphines are widely used ligands in transition metal-catalyzed reactions. Arylphosphines, such as triphenylphosphine, were among the first phosphines to show broad utility in catalysis. Beginning in the late 1990s, sterically demanding and electronrich trialkylphosphines began to receive attention as supporting ligands. These ligands were found to be particularly effective at promoting oxidative addition in cross-coupling of aryl halides. With electron-rich, sterically demanding ligands, such as tri-tertbutylphosphine, coupling of aryl bromides could be achieved at room temperature. More importantly, the less reactive, but more broadly available, aryl chlorides became accessible substrates. Tri-tert-butylphosphine has become a privileged ligand that has found application in a wide range of late transition-metal catalyzed coupling reactions. This success has led to the use of numerous monodentate trialkylphosphines in cross-coupling reactions. This review will discuss the general properties and features of monodentate trialkylphosphines and their application in cross-coupling reactions of C–X and C–H bonds.

Chemistry of Unsymmetrical C1-Substituted Oxabenzonorbornadienes

2021 ◽  
Vol 17 ◽  
Author(s):  
Austin Pounder ◽  
Angel Ho ◽  
Matthew Macleod ◽  
William Tam
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Substituent Effects ◽  
Face Selectivity ◽  
Transition Metal Catalyzed ◽  
Catalyzed Reactions ◽  
Metal Catalyzed ◽  
Synthetic Intermediate

: Oxabenzonorbornadiene (OBD) is a useful synthetic intermediate which can be readily activated by transition metal complexes with great face selectivity due to its dual-faced nature and intrinsic angle strain on the alkene. To date, the understanding of transition-metal catalyzed reactions of OBD itself has burgeoned; however, this has not been the case for unsymmetrical OBDs. Throughout the development of these reactions, the nature of C1-substituent has proven to have a profound effect on both the reactivity and selectivity of the outcome of the reaction. Upon substitution, different modes of reactivity arise, contributing to the possibility of multiple stereo-, regio-, and in extreme cases, constitutional isomers which can provide unique means of constructing a variety of synthetically useful cyclic frameworks. To maximize selectivity, an understanding of bridgehead substituent effects is crucial. To that end, this review outlines hitherto reported examples of bridgehead substituent effects on the chemistry of unsymmetrical C1-substituted OBDs.

scholarly journals Transition metal-catalyzed reactions of N-sulfinyl imines

2021 ◽  
pp. 153104
Author(s):  
Francisco Foubelo ◽  
Carmen Nájera ◽  
José M. Sansano ◽  
Miguel Yus
Keyword(s):  
Transition Metal ◽  
Transition Metal Catalyzed ◽  
Catalyzed Reactions ◽  
Metal Catalyzed

scholarly journals Chiral Aziridine Sulfide N(sp3),S-Ligands for Metal-Catalyzed Asymmetric Reactions

Symmetry ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 502
Author(s):  
Agata J. Pacuła-Miszewska ◽  
Anna Laskowska ◽  
Anna Kmieciak ◽  
Mariola Zielińska-Błajet ◽  
Marek P. Krzemiński ◽  
...  
Keyword(s):  
Metal Binding ◽  
Electronic Effect ◽  
Asymmetric Reactions ◽  
Addition Reactions ◽  
Phenyl Sulfide ◽  
Enantiomeric Ratio ◽  
Catalyzed Reactions ◽  
Metal Catalyzed ◽  
Sulfide Group

A series of new bidentate N,S-ligands—aziridines containing a para-substituted phenyl sulfide group—was synthesized and evaluated in the Pd-catalyzed Tsuji–Trost reaction and addition of diethylzinc and phenylethynylzinc to benzaldehyde. A high enantiomeric ratio for the addition reactions (up to 94.2:5.8) was obtained using the aziridine ligand bearing a p-nitro phenyl sulfide group. Collected results reveal a specific electronic effect that, by the presence of particular electron-donating or electron-withdrawing groups in the PhS- moiety, influences the σ-donor–metal binding and the enantioselectivity of the catalyzed reactions.

ChemInform Abstract: Metal-Catalyzed Reactions Between 2-Azabicyclo[2.2.1]hept-5-en-3-ones and Arylboronic Acids.

ChemInform ◽  
2010 ◽  
Vol 41 (42) ◽  
Author(s):  
Takumi Abe ◽  
Hiroyuki Takeda ◽  
Yumi Takahashi ◽  
Yoshihisa Miwa ◽  
Koji Yamada ◽  
...  
Keyword(s):  
Arylboronic Acids ◽  
Catalyzed Reactions ◽  
Metal Catalyzed

scholarly journals Metal-catalyzed oxidation renders silver intensification selective. Applications for the histochemistry of diaminobenzidine and neurofibrillary changes.

1986 ◽  
Vol 34 (12) ◽  
pp. 1667-1672 ◽  
Author(s):  
F Gallyas ◽  
J R Wolff
Keyword(s):  
Hydrogen Peroxide ◽  
Oxidative Polymerization ◽  
Silver Coating ◽  
Neurofibrillary Changes ◽  
Iodide Ions ◽  
Tissue Sections ◽  
Metal Catalyzed Oxidation ◽  
Pre Treatment ◽  
Metal Catalyzed ◽  
Catalyzed Oxidation

Physical developers can increase the visibility of end products of certain histochemical reactions, such as oxidative polymerization of diaminobenzidine and selective binding of complex silver iodide ions to Alzheimer's neurofibrillary changes. Unfortunately, this intensification by silver coating is generally superimposed on a nonspecific staining originating from the argyrophil III reaction, which also takes place when tissue sections are treated with physical developers. The present study reveals that the argyrophil III reaction can be suppressed when tissue sections are treated with certain metal ions and hydrogen peroxide before they are transferred to the physical developer. The selective intensification of Alzheimer's neurofibrillary changes requires a pre-treatment with lanthanum nitrate (10 mM/liter) and 3% hydrogen peroxide for 1 hr. The diaminobenzidine reaction can be selectively intensified when physical development is preceded by consecutive treatments with copper sulfate (10 mM/liter, pH 5, 10 min) and hydrogen peroxide (3%, pH 7, 10 min). In peroxidase histochemistry, this high-grade intensification may help to increase specificity and reduce the threshold of detectability in tracing neurons with horseradish peroxidase or in immunohistochemistry when the peroxidase-antiperoxidase method is used.

Iodide effects in transition metal catalyzed reactions

2004 ◽  
pp. 3409 ◽  
Author(s):  
Peter M. Maitlis ◽  
Anthony Haynes ◽  
Brian R. James ◽  
Marta Catellani ◽  
Gian Paolo Chiusoli
Keyword(s):  
Transition Metal ◽  
Transition Metal Catalyzed ◽  
Catalyzed Reactions ◽  
Metal Catalyzed
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