Insights into the Dual Activation Mechanism Involving Bifunctional Cinchona Alkaloid Thiourea Organocatalysts: An NMR and DFT Study

2012 ◽  
Vol 77 (21) ◽  
pp. 9813-9825 ◽  
Author(s):  
Jun-Ling Zhu ◽  
Yong Zhang ◽  
Chong Liu ◽  
An-Min Zheng ◽  
Wei Wang
Keyword(s):  
Cinchona Alkaloid ◽  
Dft Study ◽  
Activation Mechanism ◽  
Dual Activation

scholarly journals Asymmetric Cyanation of Activated Olefins with Ethyl Cyanoformate Catalyzed by Ti(IV)-Catalyst: A Theoretical Study

Catalysts ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1079
Author(s):  
Zhishan Su ◽  
Changwei Hu ◽  
Nasir Shahzad ◽  
Chan Kyung Kim
Keyword(s):  
Transition State ◽  
Self Assembly ◽  
Theoretical Study ◽  
Activation Barrier ◽  
Cinchona Alkaloid ◽  
Activation Process ◽  
Construction Step ◽  
Dual Activation ◽  
Membered Transition State ◽  
Step Mechanism

The reaction mechanism and origin of asymmetric induction for conjugate addition of cyanide to the C=C bond of olefin were investigated at the B3LYP-D3(BJ)/6-31+G**//B3LYP-D3(BJ)/6-31G**(SMD, toluene) theoretical level. The release of HCN from the reaction of ethyl cyanoformate (CNCOOEt) and isopropanol (HOiPr) was catalyzed by cinchona alkaloid catalyst. The cyanation reaction of olefin proceeded through a two-step mechanism, in which the C-C bond construction was followed by H-transfer to generate a cyanide adduct. For non-catalytic reaction, the activation barrier for the rate-determining C-H bond construction step was 34.2 kcal mol−1, via a four-membered transition state. The self-assembly Ti(IV)-catalyst from tetraisopropyl titanate, (R)-3,3′-disubstituted biphenol, and cinchonidine accelerated the addition of cyanide to the C=C double bond by a dual activation process, in which titanium cation acted as a Lewis acid to activate the olefin and HNC was orientated by hydrogen bonding. The steric repulsion between the 9-phenanthryl at the 3,3′-position in the biphenol ligand and the Ph group in olefin raised the Pauli energy (ΔE≠Pauli) of reacting fragments at the re-face attack transition state, leading to the predominant R-product.

A DFT study unveils the secret of how H2 is activated in the N-formylation of amines with CO2 and H2 catalyzed by Ru(ii) pincer complexes in the absence of exogenous additives

2017 ◽  
Vol 53 (89) ◽  
pp. 12148-12151 ◽  
Author(s):  
Yu Lu ◽  
Zheyuan Liu ◽  
Jiandong Guo ◽  
Shuanglin Qu ◽  
Ruihua Zhao ◽  
...  
Keyword(s):  
Dft Study ◽  
Activation Mechanism ◽  
Pincer Complexes ◽  
Dft Computations

DFT computations unraveled a new H2 activation mechanism used by Ru(ii) pincer complexes to catalyze the N-formylation of amines with CO2 and H2 in the absence of external additives.

scholarly journals An Enantioconvergent Benzylic Hydroxylation Using a Chiral Aryl Iodide in a Dual Activation Mode

2020 ◽  
Author(s):  
Ayham Abazid ◽  
Nils Clamor ◽  
Boris Nachtsheim
Keyword(s):  
Activation Mechanism ◽  
Second Step ◽  
Chiral Ligand ◽  
Aryl Iodide ◽  
Radical Bromination ◽  
Benzylic Hydroxylation ◽  
Dual Activation

In this article we describe an enantioselective hydroxylation of benzylic C-H bonds with a unique activation mechanism. A chiral aryl iodide catalyst initially acts as precursor for a brominating reagent which subsequently brominates the benzylic C-H bond in a non-stereoselective fashion through a radical bromination. In the second step of this transofrmation, the same catalyst acts as a chiral ligand in a Cu-catalyzed enantioconvergent substitution. We present a broad substrate scope and an intial mechanistic proposal based on a plethora of control experiments.<br>

Activation mechanism of ammonium ions on sulfidation of malachite (–201) surface by DFT study

2017 ◽  
Vol 410 ◽  
pp. 126-133 ◽  
Author(s):  
Dandan Wu ◽  
Yingbo Mao ◽  
Jiushuai Deng ◽  
Shuming Wen
Keyword(s):  
Dft Study ◽  
Activation Mechanism ◽  
Ammonium Ions
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