Chiral N-heterocyclic Carbenes (chiral + n-heterocyclic_carbene)

Distribution by Scientific Domains


Selected Abstracts


ChemInform Abstract: Asymmetric Transfer Hydrogenation Catalyzed by a Novel Planar Chiral N-Heterocyclic Carbene,Rhodium(I) Complex.

CHEMINFORM, Issue 35 2009
Ru Jiang
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]


All-Carbon Quaternary Stereogenic Centers by Enantioselective Cu-Catalyzed Conjugate Additions Promoted by a Chiral N-Heterocyclic Carbene.

CHEMINFORM, Issue 23 2007
M. Kevin Brown
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]


Enantioselective Synthesis of Spirocyclic Oxindole-,-lactones via N-Heterocyclic Carbene-Catalyzed Cycloaddition of Ketenes and Isatins

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2010
Xiao-Na Wang
Abstract Chiral N-heterocyclic carbenes were found to be efficient catalysts for the formal [2+2] cycloaddition reaction of disubstituted ketenes and isatins to give the corresponding spirocyclic oxindole-,-lactones in good yields with good diastereoselectivities and excellent enantioselectivities. Ring opening with Grignard reagents or decarboxylation of the oxindole spirocyclic-,-lactone gave the corresponding 3-hydroxy- or 3-alkylenyloxindoles in good yields. [source]


Enantioselective Synthesis of Dihydrocoumarins via N-Heterocyclic Carbene-Catalyzed Cycloaddition of Ketenes and o -Quinone Methides

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2009
Hui Lv
Abstract Chiral N-heterocyclic carbenes were found to be efficient catalysts for the formal [4+2],cycloaddition reaction of alky(aryl)ketenes and o -quinone methides to give the corresponding 3,3,4-trisubstituted 3,4-dihydrocoumarins in good yields with good diastereoselectivities and excellent enantioselectivities. [source]


N-Heterocyclic Carbene-Mediated Enantioselective Addition of Phenols to Unsymmetrical Alkylarylketenes

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2009
Carmen Concellón
Abstract Chiral N-heterocyclic carbenes (NHCs) mediate the enantioselective addition of 2-phenylphenol to unsymmetrical alkylarylketenes, delivering ,-alkyl-,-arylacetic acid derivatives with good levels of enantiocontrol (up to 84% ee). Enantiodivergent stereochemical outcomes are observed using 2-phenylphenol and benzhydrol in the NHC-promoted esterification reaction using a triazolium precatalyst derived from pyroglutamic acid, consistent with distinct mechanistic pathways operating within these processes. [source]


New Chiral N-Heterocyclic Carbene Ligands in Palladium-Catalyzed ,-Arylations of Amides: Conformational Locking through Allylic Strain as a Device for Stereocontrol

CHEMISTRY - A EUROPEAN JOURNAL, Issue 21 2010
Yi-Xia Jia Dr.
Abstract New Enders/Herrmann-type chiral N-heterocyclic carbene (NHC) ligands have been developed and applied in asymmetric palladium-catalyzed intramolecular ,-arylations of amides. The best ligands feature the bulky tert -butyl group and ortho -substituted aryl groups at the stereogenic centers. Aryl bromides readily react at room temperature and aryl chlorides at 50,°C. The highly enantiomerically enriched (up to 96,%,ee) 3-alkyl-3-aryloxindole products were obtained in generally high yields (>95,%) except in cases of steric congestion. The critical roles both of the bulky alkyl group and of the ortho -aryl substituent at the stereogenic center of the ligand were revealed in the crystal structure of a [Pd(,3 -allyl)(NHC-L*)(I)] complex. The ligand aryl location and orientation is fixed by conformational locking that minimizes A1,3 -strain and enables optimal transfer of chiral information. [source]