Dual Lewis acid - Lewis base activation in enantioselective additions to aldehydes

2006 ◽  
Vol 78 (2) ◽  
pp. 409-414 ◽  
Author(s):  
Erica Wingstrand ◽  
Stina Lundgren ◽  
Maël Penhoat ◽  
Christina Moberg
Keyword(s):  
Catalytic System ◽  
Lewis Acid ◽  
Lewis Base ◽  
Direct Route ◽  
Salen Ligands

Reaction of benzaldehyde with ethyl cyanoformate in the presence of Lewis acidic Ti(IV) complexes of bispyridylamide or salen ligands and Lewis basic amines affords the O-alkoxycarbonylated cyanohydrin. In the presence of the salen-based catalytic system, acetyl cyanide can also be added to benzaldehyde, providing a highly enantioselective direct route to the O-acetylated cyanohydrin.

scholarly journals Synergistic effects in ambiphilic phosphino-borane catalysts for the hydroboration of CO2

2016 ◽  
Vol 52 (48) ◽  
pp. 7553-7555 ◽  
Author(s):  
Anis Tlili ◽  
Arnaud Voituriez ◽  
Angela Marinetti ◽  
Pierre Thuéry ◽  
Thibault Cantat
Keyword(s):  
Catalytic System ◽  
Lewis Acid ◽  
Synergistic Effects ◽  
Lewis Base

The benefit of combining both a Lewis acid and a Lewis base in a catalytic system has been established for the hydroboration of CO2, using ferrocene-based phosphine, borane and phosphino-borane derivatives.

Cobalt/Lewis Acid Catalysis for Hydrocarbofunctionalization of Alkynes via Cooperative C–H Activation

2020 ◽  
Author(s):  
Chang-Sheng Wang ◽  
Sabrina Monaco ◽  
Anh Ngoc Thai ◽  
Md. Shafiqur Rahman ◽  
Chen Wang ◽  
...  
Keyword(s):  
Catalytic System ◽  
Lewis Acid ◽  
Hydrogen Transfer ◽  
Acid Catalysis ◽  
Rate Limiting Step ◽  
Site Selectivity ◽  
Set Up ◽  
Site Selective ◽  
First Time ◽  
Rate Limiting

A catalytic system comprised of a cobalt-diphosphine complex and a Lewis acid (LA) such as AlMe3 has been found to promote hydrocarbofunctionalization reactions of alkynes with Lewis basic and electron-deficient substrates such as formamides, pyridones, pyridines, and azole derivatives through site-selective C-H activation. Compared with known Ni/LA catalytic system for analogous transformations, the present catalytic system not only feature convenient set up using inexpensive and bench-stable precatalyst and ligand such as Co(acac)3 and 1,3-bis(diphenylphosphino)propane (dppp), but also display distinct site-selectivity toward C-H activation of pyridone and pyridine derivatives. In particular, a completely C4-selective alkenylation of pyridine has been achieved for the first time. Mechanistic stidies including DFT calculations on the Co/Al-catalyzed addition of formamide to alkyne have suggested that the reaction involves cleavage of the carbamoyl C-H bond as the rate-limiting step, which proceeds through a ligand-to-ligand hydrogen transfer (LLHT) mechanism leading to an alkyl(carbamoyl)cobalt intermediate.

Metathetical Degradation and Depolymerization of Unsaturated Polymers

1997 ◽  
Vol 70 (3) ◽  
pp. 519-529 ◽  
Author(s):  
J. C. Marmo ◽  
K. B. Wagener
Keyword(s):  
Molecular Weight ◽  
Transition Metal ◽  
Catalytic System ◽  
Lewis Acid ◽  
Catalyst System ◽  
Metal Catalysts ◽  
Transition Metal Catalysts ◽  
Side Reactions

Abstract The employment of transition metal catalysts has been a viable route in the degradation and depolymerization of unsaturated polymers. Initially, unsaturated polymers were degraded with a catalytic system containing a transition metal and a Lewis acid cocatalyst (WCl6/SnBu4). Degradation chemistry was effective in reducing the molecular weight of the polymer, however, the classical catalyst system induces side reactions which generates ill-defined products. These side reactions were obviated by using a preformed alkylidene without a Lewis acid cocatalyst, and perfectly difunctional telechelics were synthesized.

The structure and activity of potassium supported on SBA-15 molecular sieve: Density functional theory study

2014 ◽  
Vol 13 (01) ◽  
pp. 1350076 ◽  
Author(s):  
Bing Liu ◽  
Daxi Wang ◽  
Zhongxue Wang ◽  
Zhen Zhao ◽  
Yu Chen ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Lewis Acid ◽  
Molecular Sieve ◽  
Active Sites ◽  
Density Functional ◽  
Structural Model ◽  
Vibrational Frequencies ◽  
Oxygen Molecule ◽  
Lewis Base ◽  
Functional Theory

The geometries, vibrational frequencies, electronic properties and reactivity of potassium supported on SBA-15 have been theoretically investigated by the density functional theory (DFT) method. The structural model of the potassium supported on SBA-15 was constructed based on our previous work [Wang ZX, Wang DX, Zhao Z, Chen Y, Lan J, A DFT study of the structural units in SBA-15 mesoporous molecular sieve, Comput. Theor. Chem.963, 403, 2011]. This paper is the extension of our previous work. The most favored location of potassium atom was obtained by the calculation of substitution energy. The calculated vibrational frequencies of K /SBA-15 are in good agreement with the experimental results. By analyzing the properties of electronic structure, we found that the O atom of Si - O (2)- K group acts as the Lewis base center and the K atom acts as the Lewis acid center. The reactivity of K /SBA-15 was investigated by calculating the activation of oxygen molecule. The oxygen molecule can be activated by K /SBA-15 with an energy barrier of 103.2 kJ/mol. In the final state, the activated oxygen atoms become new Lewis acid centers, which are predicted to act as the active sites in the catalytic reactions. This study provides a deep insight into the properties of supported potassium catalysts and offers fundamental information for further research.

Erratum to “Synthesis and structure of potential Lewis acid–Lewis base bifunctional catalysts: 2-N,N-diisopropylaminobenzylboronate derivatives” [J. Organomet. Chem. 690 (2005) 4784–4793]

2006 ◽  
Vol 691 (3) ◽  
pp. 538
Author(s):  
Samuel W. Coghlan ◽  
Richard L. Giles ◽  
Judith A.K. Howard ◽  
Leonard G.F. Patrick ◽  
Michael R. Probert ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Lewis Base ◽  
Bifunctional Catalysts

Lewis Base Mediated β-Elimination and Lewis Acid Mediated Insertion Reactions of Disilazido Zirconium Compounds

2013 ◽  
Vol 135 (40) ◽  
pp. 15225-15237 ◽  
Author(s):  
KaKing Yan ◽  
Juan J. Duchimaza Heredia ◽  
Arkady Ellern ◽  
Mark S. Gordon ◽  
Aaron D. Sadow
Keyword(s):  
Lewis Acid ◽  
Lewis Base ◽  
Insertion Reactions ◽  
Zirconium Compounds

scholarly journals Lewis acid- and/or Lewis base-catalyzed [3+2] cycloaddition reaction: synthesis of pyrazoles and pyrazolines

2008 ◽  
Vol 49 (48) ◽  
pp. 6768-6772 ◽  
Author(s):  
Palakodety Radha Krishna ◽  
Empati Raja Sekhar ◽  
Florence Mongin
Keyword(s):  
Lewis Acid ◽  
Cycloaddition Reaction ◽  
Lewis Base ◽  
Reaction Synthesis

Empirical Lewis acid strengths for 135 cations bonded to oxygen

2017 ◽  
Vol 73 (5) ◽  
pp. 956-961 ◽  
Author(s):  
Olivier Charles Gagné ◽  
Frank Christopher Hawthorne
Keyword(s):  
Lewis Acid ◽  
Strong Correlation ◽  
Ionization Energy ◽  
Acid Strength ◽  
Lewis Base

New and updated Lewis acid strengths are listed for 135 cations bonded to oxygen for use with published Lewis base strengths. A strong correlation between Lewis acid strength and ionization energy is shown, and correlation with electronegativity is confirmed.

scholarly journals Lewis Base Activation of Lewis Acid: A Detailed Bond Analysis

ACS Omega ◽  
2018 ◽  
Vol 3 (11) ◽  
pp. 16292-16300 ◽  
Author(s):  
Gianluca Ciancaleoni
Keyword(s):  
Lewis Acid ◽  
Lewis Base
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