Facile difluoromethylation of aliphatic alcohols with an S-(difluoro-methyl)sulfonium salt: reaction, scope and mechanistic study

2019 ◽  
Vol 55 (52) ◽  
pp. 7446-7449 ◽  
Author(s):  
Guo-Kai Liu ◽  
Xin Li ◽  
Wen-Bing Qin ◽  
Xiao-Shui Peng ◽  
Henry N. C. Wong ◽  
...  
Keyword(s):  
Transition State ◽  
Aliphatic Alcohols ◽  
Mechanistic Study ◽  
Sulfonium Salt ◽  
Membered Transition State

Facile difluoromethylation of alcohols is herein described, and the mechanistic study reveals that the difluorocarbene pathway is rational via a five-membered transition state with the participation of water.

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.

Ion Cyclotron Resonance Studies of Alkylsilyl Ions. II. The Reactions of Ketones, Carboxylic Acids and Esters with the Trimethylsilyl Cation

1979 ◽  
Vol 32 (6) ◽  
pp. 1389 ◽  
Author(s):  
IA Blair ◽  
JH Bowie
Keyword(s):  
Carboxylic Acid ◽  
Transition State ◽  
Lewis Acid ◽  
Cyclotron Resonance ◽  
Nucleophilic Attack ◽  
Ion Cyclotron Resonance ◽  
Deuterium Isotope Effect ◽  
Trimethylsilyl Cation ◽  
A Minor ◽  
Membered Transition State

Nucleophilic attack of a ketone, carboxylic acid or ester at the electrophilic centre of the trimethylsilyl cation (Me,Si+) produces a 1:1 adduct. This adduct does not decompose in the case of ketones. Acid adducts decompose primarily by loss of methane, but a minor pathway exists which involves elimination of a ketene. Ester adducts fragment primarily by this latter process through a four-membered transition state. The transfer of hydrogen was shown to arise solely from the acyl group and was shown to proceed with a small deuterium isotope effect. Further decomposition of the resulting ion by loss of methane provides unequivocal proof that esters react predominantly through the alkyl oxygen with the Lewis acid Me3Si+.

scholarly journals Nickel-Catalysed Allylboration of Aldehydes

Synthesis ◽  
2020 ◽  
Vol 52 (13) ◽  
pp. 1903-1914 ◽  
Author(s):  
Benjamin M. Partridge ◽  
Francesca M. Dennis ◽  
Craig C. Robertson
Keyword(s):  
Transition State ◽  
Nickel Catalyst ◽  
Lewis Acid ◽  
Homoallylic Alcohols ◽  
Membered Transition State

A nickel catalyst for the allylboration of aldehydes is reported, facilitating the preparation of homoallylic alcohols in high diastereoselectivity. The observed diastereoselectivities and NMR experiments suggest that allylation occurs through a well-defined six-membered transition state, with nickel acting as a Lewis acid.

scholarly journals A combined experimental and DFT mechanistic study for the unexpected nitrosolysis of N-hydroxymethyldialkylamines in fuming nitric acid

RSC Advances ◽  
2018 ◽  
Vol 8 (34) ◽  
pp. 19310-19316 ◽  
Author(s):  
Yu Zhang ◽  
Po Zou ◽  
Yingbin Han ◽  
Yongliang Geng ◽  
Jun Luo ◽  
...  
Keyword(s):  
Nitric Acid ◽  
Dft Calculations ◽  
Transition State ◽  
Redox Reaction ◽  
Mechanistic Study ◽  
Fuming Nitric Acid

N-Hydroxymethyldialkylamines were nitrosolyzed unexpectedly in fuming HNO3 to give N-nitrosamines. A mechanism involving a redox reaction of HNO3 was proposed and DFT calculations indicated that the reaction proceeded smoothly with a rigid bicyclic transition state.

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