Home  About us  Contact
 

Chiral Quaternary Centers (chiral + quaternary_center)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

Enantioselective Radical Reactions: Formation of Chiral Quaternary Centers.

CHEMINFORM, Issue 30 2006
Mukund P. Sibi
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]

Copper-Catalyzed Asymmetric Conjugate Addition of Trialkylaluminium Reagents to Trisubstituted Enones: Construction of Chiral Quaternary Centers

CHEMISTRY - A EUROPEAN JOURNAL, Issue 34 2007
Magali Vuagnoux-d'Augustin
Abstract Me3Al, Et3Al, and vinylalane species undergo enantioselective conjugate addition to a wide range of 2- or 3-substituted enones (cyclopent-2-enones, cyclohex-2-enones, 3-methyl cyclohept-2-enone) in the presence of catalytic amount of copper salt (copper thiophene carboxylate, [Cu(CH3CN)4]BF4 or [CuOTf]2,C6H6) and tropos-phosphoramidite-based ligand. Thus, chiral quaternary centers can be built, with up to 98,% ee after rigorous optimization of experimental conditions. It was shown that the main important parameter was the order of the introduction of the reagents. Then, the generated enantioenriched aluminium enolates and the chiral conjugate adducts were functionalized and used for subsequent reactions. [source]

Highly Selective Preparation of a Chiral Quaternary Allyl Aryl Piperidinedione by Palladium-Catalyzed Asymmetric Allylation Under Solid,Liquid Phase-Transfer Catalysis

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 36 2007
Audrey Nowicki
Abstract The combination of a chiral palladium catalyst and a solid,liquid phase-transfer catalyst provides an effective method for the chemo- and enantioselective preparation of the chiral quaternary center of an allyl aryl piperidinedione. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

Exploring Chiral Space en route to DPC 963: A Personal Account

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2003
William
Abstract DPC 961 and DPC 963 are non-nucleoside reverse transcriptase inhibitors (NNRTIs) for the treatment of HIV. These drug candidates contain a chiral quaternary center, which can be installed via addition of lithium cyclopropylacetylide to an N -acylketimine in the presence of a chiral moderator. This account describes our efforts to identify a cost-effective moderator by rapidly preparing, screening, and optimizing libraries of enantiopure ,-amino alcohols. The result is a highly enantioselective process that has been used to produce these NNRTIs on a metric ton scale. [source]

High Diversity on Simple Substrates: 1,4-Dihalo-2-butenes and Other Difunctionalized Allylic Halides for Copper-Catalyzed SN2, Reactions

CHEMISTRY - A EUROPEAN JOURNAL, Issue 34 2008
Caroline A. Falciola Dr.
Abstract Enantioselective allylic alkylation with an organomagnesium reagent catalyzed by copper thiophene carboxylate (CuTC) was carried out on difunctionalized substrates, such as commercially available 1,4-dichloro-2-butene and 1,4-dibromo-2-butene, and on similar compounds of higher substitution pattern of the olefin for the formation of all-carbon chiral quaternary centers. The high regioselectivity obtained throughout the reactions favored good regiocontrol for the addition of phenyl Grignard reagents. Other difunctionalized substrates (allylic ethers and allylic alcohols) also underwent asymmetric SN2, substitution. [source]

Copper-Catalyzed Asymmetric Conjugate Addition of Trialkylaluminium Reagents to Trisubstituted Enones: Construction of Chiral Quaternary Centers

CHEMISTRY - A EUROPEAN JOURNAL, Issue 34 2007
Magali Vuagnoux-d'Augustin
Abstract Me3Al, Et3Al, and vinylalane species undergo enantioselective conjugate addition to a wide range of 2- or 3-substituted enones (cyclopent-2-enones, cyclohex-2-enones, 3-methyl cyclohept-2-enone) in the presence of catalytic amount of copper salt (copper thiophene carboxylate, [Cu(CH3CN)4]BF4 or [CuOTf]2,C6H6) and tropos-phosphoramidite-based ligand. Thus, chiral quaternary centers can be built, with up to 98,% ee after rigorous optimization of experimental conditions. It was shown that the main important parameter was the order of the introduction of the reagents. Then, the generated enantioenriched aluminium enolates and the chiral conjugate adducts were functionalized and used for subsequent reactions. [source]