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Chiral Phosphoric Acid (chiral + phosphoric_acid)

Distribution by Scientific Domains
Chemistry100%
Distribution within Chemistry
Organic Chemistry55%
General & Introductory Chemistry44%

Selected Abstracts

Titelbild: Which Is the Actual Catalyst: Chiral Phosphoric Acid or Chiral Calcium Phosphate? (Angew. Chem.

ANGEWANDTE CHEMIE, Issue 22 2010
22/2010)
Aktiv sind beide die chirale Phosphorsäure und das chirale Calciumphosphat! K. Ishihara et,al. berichten in der Zuschrift auf S.,3911,ff. über eine hoch enantioselektive direkte Mannich-Reaktion von Aldiminen mit einer Vielzahl an 1,3-Dicarbonylverbindungen, einschließlich ungewöhnlichen ,-Ketothioestern und Thiomalonat. Die Reaktion wird in Gegenwart einer chiralen Phosphorsäure ausgeführt und läuft in An- und Abwesenheit von CaII ab. Phosphorsäure- und Calciumphosphat-Katalyse ergeben Produkte mit entgegengesetzter absoluter Konfiguration. [source]

Which Is the Actual Catalyst: Chiral Phosphoric Acid or Chiral Calcium Phosphate?,

ANGEWANDTE CHEMIE, Issue 22 2010
Manabu Hatano Dr.
Beide! Hoch enantioselektiv verlief die gezeigte direkte Mannich-Reaktion in Gegenwart einer chiralen Phosphorsäure mit oder ohne Calcium(II)-Zusatz. Phosphorsäure- und Calciumphosphat-Katalyse ergaben Produkte mit entgegengesetzter absoluter Konfiguration (Boc=tert -Butoxycarbonyl). [source]

ChemInform Abstract: Enantioselective Friedel,Crafts Alkylation of Indoles, Pyrroles, and Furans with Trifluoropyruvate Catalyzed by Chiral Phosphoric Acid.

CHEMINFORM, Issue 26 2010
Wataru Kashikura
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Highly Enantioselective Friedel,Crafts Reaction of Indoles with Imines by a Chiral Phosphoric Acid.

CHEMINFORM, Issue 24 2007
Qiang Kang
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

ChemInform Abstract: Highly Enantioselective Hydrogenation of Enamides Catalyzed by Chiral Phosphoric Acids.

CHEMINFORM, Issue 30 2009
Guilong Li
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Highly Enantioselective Transfer Hydrogenation of ,-Imino Esters by a Phosphoric Acid

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2007
Qiang Kang
Abstract Chiral phosphoric acids have been identified as highly efficient organocatalysts for the asymmetric transfer hydrogenation of ,-imino esters and amide. Utilizing Hantzsch esters as the hydrogen donor, versatile highly enantioenriched ,-amino esters and their derivatives were obtained with up to 98,% ee. [source]

ChemInform Abstract: Highly Enantioselective Relay Catalysis in the Three-Component Reaction for Direct Construction of Structurally Complex Heterocycles.

CHEMINFORM, Issue 40 2010
Chao Wang
Abstract The three-component cascade reaction, consisting of an enantioselective [4 + 2] cycloaddition reaction catalyzed by chiral phosphoric acid and a subsequent catalytic intramolecular hydroamination by gold(I) complex, provides a method to access structurally diverse julolidine derivatives. [source]

Mechanistic Investigation of Chiral Phosphoric Acid Catalyzed Asymmetric Baeyer,Villiger Reaction of 3-Substituted Cyclobutanones with H2O2 as the Oxidant

CHEMISTRY - A EUROPEAN JOURNAL, Issue 10 2010
Senmiao Xu Dr.
Abstract The mechanism of the chiral phosphoric acid catalyzed Baeyer,Villiger (B,V) reaction of cyclobutanones with hydrogen peroxide was investigated by using a combination of experimental and theoretical methods. Of the two pathways that have been proposed for the present reaction, the pathway involving a peroxyphosphate intermediate is not viable. The reaction progress kinetic analysis indicates that the reaction is partially inhibited by the ,-lactone product. Initial rate measurements suggest that the reaction follows Michaelis,Menten-type kinetics consistent with a bifunctional mechanism in which the catalyst is actively involved in both carbonyl addition and the subsequent rearrangement steps through hydrogen-bonding interactions with the reactants or the intermediate. High-level quantum chemical calculations strongly support a two-step concerted mechanism in which the phosphoric acid activates the reactants or the intermediate in a synergistic manner through partial proton transfer. The catalyst simultaneously acts as a general acid, by increasing the electrophilicity of the carbonyl carbon, increases the nucleophilicity of hydrogen peroxide as a Lewis base in the addition step, and facilitates the dissociation of the OH group from the Criegee intermediate in the rearrangement step. The overall reaction is highly exothermic, and the rearrangement of the Criegee intermediate is the rate-determining step. The observed reactivity of this catalytic B,V reaction also results, in part, from the ring strain in cyclobutanones. The sense of chiral induction is rationalized by the analysis of the relative energies of the competing diastereomeric transition states, in which the steric repulsion between the 3-substituent of the cyclobutanone and the 3- and 3,-substituents of the catalyst, as well as the entropy and solvent effects, are found to be critically important. [source]

Charge-Transfer Effect on Chiral Phosphoric Acid Catalyzed Asymmetric Baeyer-Villiger Oxidation of 3-Substituted Cyclobutanones Using 30% Aqueous H2O2 as the Oxidant,

CHINESE JOURNAL OF CHEMISTRY, Issue 9 2010
Senmiao Xu
Abstract The intermolecular charge-transfer effect has been employed for the first time as a modulating approach to affect the enantioselectivity in asymmetric catalysis by taking the chiral phosphoric acid catalyzed asymmetric Baeyer-Villiger oxidation of 3-aryl cyclobutanones as the reaction prototype. It was found that the electron acceptor additives were able to effectively tune the enantioselectivity via donor-acceptor interaction with the catalyst and up to 9% enhancement of ee value was observed in a favorable case. [source]