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Highly Enantioselective Catalyst (highly + enantioselective_catalyst)

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Chemistry100%

Selected Abstracts

Polymer-Supported Highly Enantioselective Catalyst for Nitro-Michael Addition: Tuning through Variation of the Number of H-Bond Donors and Spacer Length

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2009
Lital Tuchman-Shukron
Abstract Two series of polymer-bound bifunctional organocatalysts, based on chiral diamine scaffolds, were prepared by solid-phase synthesis. The series, incorporating a single hydrogen bond donor carbamate functionality, was notably more enantioselective in the Michael reaction of acetone and nitrostyrene than the series that includes a double hydrogen bond donor urea moiety, or the polymer-bound diamine that lacks sufficiently acidic protons. The best aminocarbamate catalyst promoted the addition of acetone to nitroolefins with enantioselectivity unmatched by known heterogeneous catalysts. Introduction of a short linear spacer between the support and the scaffold improves the activity but reduces the selectivity of the catalyst. Alternatively, an increase in the reaction yield could be induced by the benzoic acid additive. [source]

Diphenylprolinol Methyl Ether: A Highly Enantioselective Catalyst for Michael Addition of Aldehydes to Simple Enones.

CHEMINFORM, Issue 4 2006
Yonggui Chi
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

A Highly Enantioselective Catalyst for the Asymmetric Nozaki,Hiyama,Kishi Reaction of Allylic and Vinylic Halides.

CHEMINFORM, Issue 26 2003
Albrecht Berkessel
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Chiral Chromium(III) Porphyrins as Highly Enantioselective Catalysts for Hetero-Diels,Alder Reactions Between Aldehydes and Dienes.

CHEMINFORM, Issue 23 2006
Albrecht Berkessel
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]

Chiral Squaramides as Highly Enantioselective Catalysts for Michael Addition Reactions of 4-Hydroxycoumarins and 4-Hydroxypyrone to ,,,-Unsaturated ,-Keto Esters

CHEMISTRY - A EUROPEAN JOURNAL, Issue 14 2010
Dan-Qian Xu Prof.
Distance brings forth beauty: The first highly enantioselective organocatalytic Michael addition of 4-hydroxycoumarins and the analogous 4-hydroxy-6-methyl-2-pyrone to ,,,-unsaturated ,-keto esters by using chiral squaramides as the organocatalysts is disclosed. The efficiency of the process is attributed to the hydrogen-bonding activation (see scheme). [source]

Enantioselective Cyanosilylation of Ketones Catalyzed by a Nitrogen-Containing Bifunctional Catalyst

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4-5 2006
Yan Xiong
Abstract An efficient and optically active, bifunctional tetraaza ligand (2S)- N -{(1R,2R)-2-[(S)-pyrrolidine-2-carboxamido]-1,2-diphenylethyl}pyrrolidine-2-carboxamide has been developed for the addition of trimethylsilyl cyanide (TMSCN) to ketones. The bifunctional catalyst system based on a monometallic titanium complex was found to be a highly enantioselective catalyst to provide O -TMS cyanohydrins with up to 94% ee. A possible transition state has been proposed to explain the origin of the activation and asymmetric inductivity. [source]