scholarly journals Thermodynamic versus kinetic control in substituent redistribution reactions of silylium ions steered by the counteranion

2018 ◽  
Vol 9 (25) ◽  
pp. 5600-5607 ◽  
Author(s):  
Lukas Omann ◽  
Bimal Pudasaini ◽  
Elisabeth Irran ◽  
Hendrik F. T. Klare ◽  
Mu-Hyun Baik ◽  
...  
Keyword(s):  
Kinetic Control ◽  
Exchange Reactions ◽  
Redistribution Reactions ◽  
Judicious Choice ◽  
Selective Formation

Substituent exchange reactions of silylium ions can be steered in opposite directions. The judicious choice of the hydrosilane and the counteranion enables the selective formation of either triaryl- or trialkylsilylium ions.

Selective Formation of a Self-Assembling Homo or Hetero Cavitand Cage via Metal Coordination Based on Thermodynamic or Kinetic Control

2006 ◽  
Vol 128 (5) ◽  
pp. 1531-1539 ◽  
Author(s):  
Masamichi Yamanaka ◽  
Yoshifumi Yamada ◽  
Yoshihisa Sei ◽  
Kentaro Yamaguchi ◽  
Kenji Kobayashi
Keyword(s):  
Metal Coordination ◽  
Kinetic Control ◽  
Self Assembling ◽  
Selective Formation

Phosphorus-31, mercury-199 and selenium-77 n.m.r. studies of ligand exchange reactions in mercury(II) halide complexes

1980 ◽  
Vol 33 (7) ◽  
pp. 1463 ◽  
Author(s):  
R Colton ◽  
D Dakternieks
Keyword(s):  
Time Scale ◽  
Ligand Exchange ◽  
Room Temperature ◽  
Mixed Ligand ◽  
Mixed Ligand Complexes ◽  
Exchange Reactions ◽  
Halogen Exchange ◽  
Redistribution Reactions ◽  
Halide Complexes

Mercury(II) halide complexes of tris(4-methoxyphenyl)phosphine have been investigated by 31P and 199Hg n.m.r. spectroscopy of CH2Cl2 solutions. At room temperature the phosphine exchanges at an appreciable rate and halogen exchange is fast. At -50°C both phosphine and halogen exchange are slow on the n.m.r. time scale and halogen redistribution reactions are observed. ��� Mercury(II) halide complexes with tributylphosphine selenide have been investigated by 31P, 199Hg and 77Se n.m.r. methods. This ligand is labile and exchanges rapidly on the n.m.r. time scale at room temperature, although the exchange can be slowed down at about -100°C. Halogen exchange is also fast at room temperature. ��� Ligand exchange reactions between tributylphosphine and either tris(4-methoxyphenyl)phosphine or tributylphosphine selenide were investigated and redistribution reactions to give mixed ligand complexes were observed.

Synthesis and catalysed hydroboration of styryl sulfonamides

2005 ◽  
Vol 83 (6-7) ◽  
pp. 661-667 ◽  
Author(s):  
Natalie A Wynberg ◽  
Lisa J Leger ◽  
Maren L Conrad ◽  
Christopher M Vogels ◽  
Andreas Decken ◽  
...  
Keyword(s):  
Transition Metal ◽  
Metal Catalyst ◽  
Transition Metal Catalyst ◽  
Boronate Esters ◽  
Sulfonyl Chlorides ◽  
Hydrogenation Reactions ◽  
Judicious Choice ◽  
Selective Formation

We have prepared the aryl sulfonamides 4,4′-R-C6H4SO2NHC6H4CH=CH2 (R = CH3, 1a; NO2, 1b) by addition of 2 equiv. of 4-vinylaniline to the corresponding sulfonyl chlorides. The disulfonamides 4,4,4′-(R-C6H4SO2)2NC6H4CH=CH2 (R = CH3, 2a; NO2, 2b) were also prepared using 4-vinylaniline and 2 equiv. of the sulfonyl chlorides in the presence of DMAP. Although hydroborations of sulfanilamide derivatives 1 suffered from competing hydrogenation reactions, judicious choice of the transition metal catalyst gave selective formation of either the primary or secondary boronate esters in hydroborations of 2a.Key words: boronate esters, catalysed hydroborations, sulfanilamides, vinylaniline.

Exchange reactions and electrolytic dissociation

1948 ◽  
Vol 45 ◽  
pp. 147-149 ◽  
Author(s):  
C. C. Evans ◽  
S. Sugden
Keyword(s):  
Exchange Reactions ◽  
Electrolytic Dissociation

Modeling of photosynthesis light curves by linear splines

2019 ◽  
pp. 20-29
Author(s):  
Alexander S. Lelekov ◽  
Rudolf P. Trenkenshu
Keyword(s):  
Experimental Data ◽  
Chlorophyll A ◽  
Skeletonema Costatum ◽  
Light Flux ◽  
Photosynthesis Rate ◽  
Light Curves ◽  
External Irradiation ◽  
Exchange Reactions ◽  
Cell Adaptation ◽  
Linear Splines

The paper presents an example of the linear splines use to describe the photosynthesis light curves for microalgae culture. The main mathematical models of the relationship between photosynthesis rate and light are listed. Based on the previously formulated basic principles of modeling microalgae photobiosynthesis, a mathematical model is proposed that describes the dependence of the assimilation number of chlorophyll a on the value of the light flux by linear splines. The advantage of the proposed approach is a clear definition of the point of change of the limiting factor. It is shown that light-limited photosynthesis rate is determined not only by external irradiation, but also by the concentration of chlorophyll a. The light-saturated rate depends on the amount of a key enzyme complex, which limits the rate of energy exchange reactions in the cell. Verification of the proposed model on the example of the diatom microalgae Skeletonema costatum was carried out. It is shown that the higher the degree of cell adaptation to high irradiation, the better the photosynthesis curve is described by linear splines. If S. costatum cells are adapted to low irradiation, deviations of experimental data from the idealized broken line are observed, which are caused by changes in the pigment composition. When the experimental data are normalized, the cell adaptation factor is reduced, all points are described by a single broken line, which indicates the universality of the proposed approach.

Metal-Metal Cooperative Bond Activation by Heterobimetallic Alkyl, Aryl, and Acetylide PtII/CuI Complexes

2020 ◽  
Author(s):  
Shubham Deolka ◽  
Orestes Rivada Wheelaghan ◽  
Sandra Aristizábal ◽  
Robert Fayzullin ◽  
Shrinwantu Pal ◽  
...  
Keyword(s):  
Alkyl Group ◽  
Bond Activation ◽  
Bond Cleavage ◽  
Terminal Alkyne ◽  
Alkyl Aryl ◽  
Metal Metal ◽  
The Stability ◽  
Selective Formation ◽  
Organoplatinum Compounds

We report selective formation of heterobimetallic PtII/CuI complexes that demonstrate how facile bond activation processes can be achieved by altering reactivity of common organoplatinum compounds through their interaction with another metal center. The interaction of the Cu center with Pt center and with a Pt-bound alkyl group increases the stability of PtMe2 towards undesired rollover cyclometalation. The presence of the CuI center also enables facile transmetalation from electron-deficient tetraarylborate [B(ArF)4]- anion and mild C-H bond cleavage of a terminal alkyne, which was not observed in the absence of an electrophilic Cu center. The DFT study indicates that the role of Cu center acts as a binding site for alkyne substrate, while activating its terminal C-H bond.

Gold Catalyzed Hydroamination of Propargylic Alcohols: Controlling Divergent Reaction Pathways to Access 1,3-Aminoalcohols, 3-Hydroxyketones or 3-Aminoketones

2018 ◽  
Author(s):  
Victor Laserna ◽  
Tom Sheppard
Keyword(s):  
Gold Catalysis ◽  
Reaction Pathways ◽  
High Yield ◽  
Reaction Conditions ◽  
Propargylic Alcohols ◽  
Catalytic Quantity ◽  
Selective Formation ◽  
General Method

A versatile approach to the valorization of propargylic alcohols is reported, enabling controlled access to three different products from the same starting materials. Firstly, a general method for the hydroamination of propargylic alcohols with anilines is described using gold catalysis to give 3-hydroxy imines with complete regioselectivity. These 3-hydroxyimines can be reduced to give 1,3-aminoalcohols with high syn seletivity. Alternatively, by using a catalytic quantity of aniline, 3-hydroxyketones can be obtained in high yield directly from propargylic alcohols. Further manipulation of the reaction conditions enables the selective formation of 3-aminoketones via a rearrangement/hydroamination pathway.<br>

Sign in / Sign up

Export Citation Format

Share Document