Book Chapter10.1007/978-3-642-02815-1_17
Lewis Acid Organocatalysts
69
TL;DR: This review covers the survey of known classes of metal-free Lewis acids and their application in catalysis and reveals the ability to catalyze a range of reactions either in substoichiometric amount or, if used as the reaction medium, in stoichiometric or even larger quantities.
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Abstract: The term Lewis acid catalysts generally refers to metal salts like aluminium chloride, titanium chloride and zinc chloride. Their application in asymmetric catalysis can be achieved by the addition of enantiopure ligands to these salts. However, not only metal centers can function as Lewis acids. Compounds containing carbenium, silyl or phosphonium cations display Lewis acid catalytic activity. In addition, hypervalent compounds based on phosphorus and silicon, inherit Lewis acidity. Furthermore, ionic liquids, organic salts with a melting point below 100 °C, have revealed the ability to catalyze a range of reactions either in substoichiometric amount or, if used as the reaction medium, in stoichiometric or even larger quantities. The ionic liquids can often be efficiently recovered. The catalytic activity of the ionic liquid is explained by the Lewis acidic nature of their cations. This review covers the survey of known classes of metal-free Lewis acids and their application in catalysis.
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Citations
Direct Organocatalytic Oxo-Metathesis, a trans-Selective Carbocation-Catalyzed Olefination of Aldehydes
TL;DR: In this paper, a direct organocatalytic carbonyl/olefin oxo-metathesis has been developed, which utilizes unactivated alkenes for the olefination of aromatic aldehydes to give transalkylstyrenes in yields of 44-85% with only acetone as the byproduct.
Computational Studies on the Tropylium‐Catalyzed Carboxylic Acid O‐H Insertion with Diazoesters: The Role of Homoaromaticity
TL;DR: Tropylium‐catalyzed carboxylic acid O‐H insertion with diazoesters proceeds through a revised mechanism involving a homoaromatic intermediate.
A Boron–Oxygen Transborylation Strategy for a Catalytic Midland Reduction
Kieran Nicholson,Joanne Dunne,Peter DaBell,Alexander Beaton Garcia,Andrew D. Bage,Jamie H. Docherty,Thomas Anthony Hunt,Thomas Langer,Stephen P. Thomas +8 more
TL;DR: The enantioselective hydroboration of ketones is a textbook reaction requiring stoichiometric amounts of an enantioenriched borane, with the Midland reduction being a seminal example as mentioned in this paper.
Electrophilic phosphonium cations catalyze hydroarylation and hydrothiolation of olefins
TL;DR: Electrophilic phosphonium cations are efficient main group catalysts for the hydroarylation of olefins under mild conditions, providing a facile route to substituted aniline, bis-arylamine, phenol, furan, thiophene, pyrrole, and indole derivatives.
References
•Book
Ionic Liquids in Synthesis
Peter Wasserscheid,Tom Welton +1 more
- 01 Jan 2002
TL;DR: The early years of Ionic liquid production were covered in this article, where a new generation of soluble supports for Supported Organic Synthesis (SPOS) was proposed. But this support was not applied to the task-specific Ionic liquids.
•Book
Comprehensive asymmetric catalysis
Eric N. Jacobsen,Andreas Pfaltz,尚 山本 +2 more
- 01 Jan 1999
TL;DR: Ohkuma et al. as mentioned in this paper proposed an asymmetric Dihydroxylation process for carbon-Carbon double bonds and showed that it can be used for allylation of C=O.
3.9K
Chemical Redox Agents for Organometallic Chemistry
TL;DR: 1. Advantages and disadvantages of Chemical Redox Agents, 2. Reversible vs Irreversible ET Reagents, 3. Categorization of Reagent Strength.
Equilibrium Acidities in Dimethyl Sulfoxide Solution
TL;DR: The first acidity scale to be established in a pure solvent other than water was the result of the pioneering work of Conant, Wheland, and McEwen in ether or ben~ene.