Homologation of Alkyl Acetates, Alkyl Ethers, Acetals and Ketals by Formal Insertion of Diazo Compounds into a Carbon-Carbon Bond

Synthesis ◽  
2021 ◽  
Author(s):  
Fei Wang ◽  
Junyi Yi ◽  
Yoshihiro Nishimoto ◽  
Makoto Yasuda
Keyword(s):  
Lewis Acid ◽  
Lewis Acids ◽  
Diazo Compounds ◽  
Lewis Acidity ◽  
Carbon Carbon Bond ◽  
Leaving Group ◽  
Diazo Esters ◽  
Alkyl Ethers ◽  
Alkyl Acetates ◽  
Leaving Groups

We have accomplished homologation of alkyl acetates, alkyl ethers, acetals, and ketals via formal insertion of diazo esters into carbon-carbon σ-bonds. The combined Lewis acid of InI3 with Me3SiBr catalyzed the homologation of alkyl acetates and alkyl ethers. That of acetals and ketals was catalyzed solely by the use of InBr3. The key point of the homologation mechanism is that the indium-based Lewis acids have the appropriate amount of Lewis acidity to achieve both the abstraction and release of leaving groups. The abstraction of a leaving group by an indium-based Lewis acid, the electrophilic addition of carbocation or oxonium intermediates to diazo esters followed by the rearrangement of carbon substituents provides the corresponding cation intermediates. Finally, the leaving group that is captured by the Lewis acid bonds with cation intermediates to furnish the homologated products.

Fluorinated 9-borafluorenes vs. conventional perfluoroaryl boranes — Comparative Lewis acidity

2005 ◽  
Vol 83 (12) ◽  
pp. 2098-2105 ◽  
Author(s):  
Preston A Chase ◽  
Patricio E Romero ◽  
Warren E Piers ◽  
Masood Parvez ◽  
Brian O Patrick
Keyword(s):  
Key Words ◽  
Lewis Acid ◽  
Lewis Acids ◽  
Acid Strength ◽  
Lewis Base ◽  
Lewis Acidity ◽  
Electrochemical Studies ◽  
Steric Factors

Perfluorinated 9-phenyl-9-borafluorene, 1, is an antiaromatic analog of the well-known tris(pentafluorophenyl)borane. Spectroscopic, structural, and electrochemical studies have been performed on 1 and its Lewis base adducts with MeCN, THF, and PMe3 with a view to assessing its comparative Lewis acid strength relative to B(C6F5)3. For the sterically undemanding Lewis base MeCN, 1 and B(C6F5)3 have comparable LA strengths, while for more sterically prominent THF, 1 is clearly the stronger Lewis acid (LA) based on competition experiments. We conclude that steric factors, rather than antiaromaticity, are the most important determinants in the LA strength differences between 1 and B(C6F5)3.Key words: boranes, Lewis acids, fluorinated compounds, heterocycles.

scholarly journals Models for Understanding Divergent Reactivity in Lewis Acid-Catalyzed Transformations of Carbonyls and Olefins

2019 ◽  
Author(s):  
Marc R. Becker ◽  
Jolene P. Reid ◽  
Katie Rykaczewski ◽  
Corinna Schindler
Keyword(s):  
Lewis Acid ◽  
Olefin Metathesis ◽  
Lewis Acids ◽  
Potential Energy Surfaces ◽  
High Selectivity ◽  
Linear Regression Models ◽  
Lewis Acid Catalysts ◽  
Carbon Carbon Bond ◽  
Acid Catalyzed ◽  
Energy Surfaces

<div>Carbonyl-ene, Prins and carbonyl-olefin metathesis reactions represent powerful strategies for carbon-carbon bond formation relying on Lewis acid catalysts. Although common Lewis acids are able to provide efficient activation, the reactions often proceed with low regio-, or chemoselectivity while high selectivity frequently requires the use of well-designed metal-ligand complexes. Here we demonstrate that simple Lewis acids including Me<sub>2</sub>AlCl, FeCl<sub>3</sub>, and SnCl<sub>4</sub> can show remarkable selectivity in dif-ferentiating between distinct transformations of carbonyl and olefin functional groups resulting in either carbonyl-ene or carbonyl-olefin metathesis products. Specifically, we report the development of predictive multivariate linear regression models that rely on kinetic and thermodynamic information obtained in DFT calculations to gain important insights into the complex potential energy surfaces (PES) of these competing reaction paths. The presented results further our understanding of Lewis acid reactivity and suggest that even simple Lewis acids have the potential to function as highly selective catalysts.</div>

scholarly journals Hydrogen activation using a novel tribenzyltin Lewis acid

2017 ◽  
Vol 375 (2101) ◽  
pp. 20170008 ◽  
Author(s):  
Robert T. Cooper ◽  
Joshua S. Sapsford ◽  
Roland C. Turnell-Ritson ◽  
Dong-Hun Hyon ◽  
Andrew J. P. White ◽  
...  
Keyword(s):  
Low Temperature ◽  
Lewis Acid ◽  
Lewis Acids ◽  
Lewis Acidity ◽  
The Novel ◽  
Hydrogen Activation ◽  
Frustrated Lewis Pair

Over the last decade there has been an explosion in the reactivity and applications of frustrated Lewis pair (FLP) chemistry. Despite this, the Lewis acids (LAs) in these transformations are often boranes, with heavier p -block elements receiving surprisingly little attention. The novel LA Bn 3 SnOTf ( 1 ) has been synthesized from simple, inexpensive starting materials and has been spectroscopically and structurally characterized. Subtle modulation of the electronics at the tin centre has led to an increase in its Lewis acidity in comparison with previously reported R 3 SnOTf LAs, and has facilitated low temperature hydrogen activation and imine hydrogenation. Deactivation pathways of the R 3 Sn + LA core have also been investigated. This article is part of the themed issue ‘Frustrated Lewis pair chemistry’.

scholarly journals Models for Understanding Divergent Reactivity in Lewis Acid-Catalyzed Transformations of Carbonyls and Olefins

2019 ◽  
Author(s):  
Marc R. Becker ◽  
Jolene P. Reid ◽  
Katie Rykaczewski ◽  
Corinna Schindler
Keyword(s):  
Lewis Acid ◽  
Olefin Metathesis ◽  
Lewis Acids ◽  
Potential Energy Surfaces ◽  
High Selectivity ◽  
Linear Regression Models ◽  
Lewis Acid Catalysts ◽  
Carbon Carbon Bond ◽  
Acid Catalyzed ◽  
Energy Surfaces

<div>Carbonyl-ene, Prins and carbonyl-olefin metathesis reactions represent powerful strategies for carbon-carbon bond formation relying on Lewis acid catalysts. Although common Lewis acids are able to provide efficient activation, the reactions often proceed with low regio-, or chemoselectivity while high selectivity frequently requires the use of well-designed metal-ligand complexes. Here we demonstrate that simple Lewis acids including Me<sub>2</sub>AlCl, FeCl<sub>3</sub>, and SnCl<sub>4</sub> can show remarkable selectivity in dif-ferentiating between distinct transformations of carbonyl and olefin functional groups resulting in either carbonyl-ene or carbonyl-olefin metathesis products. Specifically, we report the development of predictive multivariate linear regression models that rely on kinetic and thermodynamic information obtained in DFT calculations to gain important insights into the complex potential energy surfaces (PES) of these competing reaction paths. The presented results further our understanding of Lewis acid reactivity and suggest that even simple Lewis acids have the potential to function as highly selective catalysts.</div>

Catalytic Carbonyl-Olefin Metathesis of Aliphatic Ketones: Iron(III) HomoDimers as Lewis Acidic Superelectrophiles

2018 ◽  
Author(s):  
Haley Albright ◽  
Paul S. Riehl ◽  
Christopher C. McAtee ◽  
Jolene P. Reid ◽  
Jacob R. Ludwig ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Olefin Metathesis ◽  
Acid Activation ◽  
Lewis Acid Catalysts ◽  
Distinct Mode ◽  
Aliphatic Ketones ◽  
Carbon Carbon Bond ◽  
Metathesis Reactions ◽  
Acid Catalyzed

<div>Catalytic carbonyl-olefin metathesis reactions have recently been developed as a powerful tool for carbon-carbon bond</div><div>formation. However, currently available synthetic protocols rely exclusively on aryl ketone substrates while the corresponding aliphatic analogs remain elusive. We herein report the development of Lewis acid-catalyzed carbonyl-olefin ring-closing metathesis reactions for aliphatic ketones. Mechanistic investigations are consistent with a distinct mode of activation relying on the in situ formation of a homobimetallic singly-bridged iron(III)-dimer as the active catalytic species. These “superelectrophiles” function as more powerful Lewis acid catalysts that form upon association of individual iron(III)-monomers. While this mode of Lewis acid activation has previously been postulated to exist, it has not yet been applied in a catalytic setting. The insights presented are expected to enable further advancement in Lewis acid catalysis by building upon the activation principle of “superelectrophiles” and broaden the current scope of catalytic carbonyl-olefin metathesis reactions.</div>

The effect of steric size of leaving group on rates of the competing syn- and anti-pathways in biomolecular elimination

1980 ◽  
Vol 45 (8) ◽  
pp. 2171-2178
Author(s):  
Jiří Závada ◽  
Magdalena Pánková
Keyword(s):  
Comparative Analysis ◽  
Homologous Series ◽  
Leaving Group ◽  
Leaving Groups

Approximate rates of the competing syn- and anti-pathways have been determined in t-C4H9OK-t-C4H9OH promoted elimination from two homologous series of tosylates: I-OTs trans-III (R = H, CH3, C2H5, n-C3H7, i-C3H7, t-C4H9) and II-OTs trans-IV (R = CH3, C2H5, n-C3H7, i-C3H7, t-C4H9). A comparison has been made with rates of the same processes in the (+) elimination of the corresponding trimethylammonium salts I-N(CH3)3 trans-III and (+) II-N(CH3)3 trans-IV. The title effect is demonstrated by a comparative analysis of the rate patterns obtained for the two leaving groups.

Copper(II) complexes with tridentate halogen‐substituted Schiff base ligands: synthesis, crystal structures and investigating the effect of halogenation, leaving group and ligand flexibility on antiproliferative activities

2021 ◽  
Author(s):  
Nazanin Kordestani ◽  
Hadi Amiri Rudbari ◽  
Alexandra R Fernandes ◽  
Luís R Raposo ◽  
André Luz ◽  
...  
Keyword(s):  
Schiff Base ◽  
Anticancer Activity ◽  
Crystal Structures ◽  
Copper Complexes ◽  
Schiff Base Ligands ◽  
Leaving Group ◽  
Leaving Groups ◽  
Tridentate Schiff Base ◽  
Antiproliferative Activities

To investigate the effect of different halogen substituents, leaving groups and the flexibility of ligand on the anticancer activity of copper complexes, sixteen copper(II) complexes with eight different tridentate Schiff-base...

scholarly journals Glucose Conversion into 5-Hydroxymethylfurfural over Niobium Oxides Supported on Natural Rubber-Derived Carbon/Silica Nanocomposite

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 887
Author(s):  
Rujeeluk Khumho ◽  
Satit Yousatit ◽  
Chawalit Ngamcharussrivichai
Keyword(s):  
Natural Rubber ◽  
Lewis Acid ◽  
Value Added ◽  
Acid Sites ◽  
Superior Performance ◽  
Lewis Acidity ◽  
Lewis Acid Sites ◽  
Niobium Oxides ◽  
Silica Nanocomposite ◽  
Loading Amount

5-Hydroxymethylfurfural (HMF) is one of the most important lignocellulosic biomass-derived platform molecules for production of renewable fuel additives, liquid hydrocarbon fuels, and value-added chemicals. The present work developed niobium oxides (Nb2O5) supported on mesoporous carbon/silica nanocomposite (MCS), as novel solid base catalyst for synthesis of HMF via one-pot glucose conversion in a biphasic solvent. The MCS material was prepared via carbonization using natural rubber dispersed in hexagonal mesoporous silica (HMS) as a precursor. The Nb2O5 supported on MCS (Nb/MCS) catalyst with an niobium (Nb) loading amount of 10 wt.% (10-Nb/MCS) was characterized by high dispersion, and so tiny crystallites of Nb2O5, on the MCS surface, good textural properties, and the presence of Bronsted and Lewis acid sites with weak-to-medium strength. By varying the Nb loading amount, the crystallite size of Nb2O5 and molar ratio of Bronsted/Lewis acidity could be tuned. When compared to the pure silica HMS-supported Nb catalyst, the Nb/MCS material showed a superior glucose conversion and HMF yield. The highest HMF yield of 57.5% was achieved at 93.2% glucose conversion when using 10-Nb/MCS as catalyst (5 wt.% loading with respect to the mass of glucose) at 190 °C for 1 h. Furthermore, 10-Nb/MCS had excellent catalytic stability, being reused in the reaction for five consecutive cycles during which both the glucose conversion and HMF yield were insignificantly changed. Its superior performance was ascribed to the suitable ratio of Brønsted/Lewis acid sites, and the hydrophobic properties generated from the carbon moieties dispersed in the MCS nanocomposite.

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