Výsledky vyhledávání - "Guenter Helmchen"

Enantioselective Iridium-Catalyzed Allylic Alkylations - Improvements and Applications Based on Salt-Free Reaction Conditions

Autor: Nicole Miller, Christian Gnamm, Kerstin Broedner, Guenter Helmchen, Sebastian Foerster

Publikováno v: Synlett. 2007:0790-0794

Simplified procedures for the Ir-catalyzed asymmetric allylic alkylation reaction are described that often allow substitution products to be obtained with ≥99% ee. Applications to syntheses of important chiral building blocks, such as the Taniguchi

Externí odkaz: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::8e16f530a1bf523b758fcc8385de4dd7
https://doi.org/10.1055/s-2007-970754

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A Straightforward Synthesis of (3S)-4-Methoxybutane-1,3-diol and its Use as Chiral Auxiliary for the Preparation of (pS)-1-(Diphenylphosphino)-2-formyl-1′,2′,3′,4′,5′-pentamethylferrocene

Autor: Felix M. Geisler, Guenter Helmchen

Publikováno v: Synthesis. 2006:2201-2205

(3S)-4-Methoxy-butane-1,3-diol (S)-4, an important auxiliary for the synthesis of planar-chiral metallocenes, has been obtained from (S)-1,2,4-butanetriol via formation of an isomerically pure acetal of p-nitrobenzaldehyde, O-methylation and hydrolys

Externí odkaz: https://explore.openaire.eu/search/publication?articleId=doi_________::9b268d6441a6a935d748f5d1695c7c2f
https://doi.org/10.1055/s-2006-942415

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Chiral Phosphinooxazolines with a Pentamethylferrocene BackboneSynthesis and Use as Ligands in Asymmetric Catalysis

Autor: Felix M. Geisler, Guenter Helmchen

Publikováno v: The Journal of Organic Chemistry. 71:2486-2492

Novel phosphinooxazolines, containing a unit of central and a unit of planar chirality in a matched case combination, have been successfully tested in the Pd-catalyzed asymmetric allylic substitution with cycloalkenyl acetates as substrates.

Externí odkaz: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::8674406c73a8502c57c2a80ab0e72d72
https://doi.org/10.1021/jo0526136

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Syntheses of Enantiomerically Pure Cyclopent-2-ene-1-carboxylic Acid and (Cyclopent-2-enyl)acetic Acid by Enantioselective Palladium-Catalyzed Allylic Alkylations − Synthesis of Enantiomerically Pure (−)-Chaulmoogric Acid

Autor: Matthias Seemann, Steffen Kudis, Markus Schoeller, Guenter Helmchen

Publikováno v: European Journal of Organic Chemistry. 2003:2122-2127

Asymmetric Pd-catalyzed allylic alkylations of dimethyl malonate and diethyl 2-acetoxymalonate with 3-chlorocyclopentene, using phosphanyloxazolines 1 and ent-1 as chiral ligands, gave products (−)-2 and (+)-3b with 95 and 99.5% ee, respectively. O

Externí odkaz: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::a1bab64df0caea6d8e071110e6710085
https://doi.org/10.1002/ejoc.200200700

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Asymmetric IrI-Catalysed Allylic Alkylation Of Monosubstituted Allylic Acetates With Phosphorus Amidites As Ligands

Autor: Cristina García-Yebra, Guenter Helmchen, Bjoern Bartels

Publikováno v: ResearcherID

Monodentate phosphorus amidites derived from 2,2′-binaphthol and a variety of chiral amines were employed as ligands in IrI-catalysed allylic alkylations of unsymmetrically substituted allylic acetates. The enantio- and regioselectivities of these

Externí odkaz: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::a7d562ee2782df2ccd4210c4ad28c85f
https://doi.org/10.1002/ejoc.200390162

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Iridium-Catalysed Allylic Substitution: Stereochemical Aspects and Isolation of IrIII Complexes Related to the Catalytic Cycle

Autor: Guenter Helmchen, Cristina García-Yebra, Bjoern Bartels, Frank Rominger

Publikováno v: ResearcherID

Ir-catalysed allylic alkylations of enantiomerically enriched monosubstituted allylic acetates proceed with up to 87% retention of configuration using P(OPh)3 as ligand. High regio- and enantioselectivity of up to 86% ee in asymmetric allylic alkylat

Externí odkaz: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::eb7f3772bc1eaefc75d7cbb32e170b9d
https://doi.org/10.1002/1099-0682(200210)2002:10<2569::aid-ejic2569>3.0.co

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ChemInform Abstract: Enantio- and Regioselective Iridium-Catalyzed Allylic Esterification

Autor: Lydia Rossberg, Guenter Helmchen, Jian-Ping Qu

Publikováno v: ChemInform. 45

A synthesis of a broad range of aliphatic and aromatic substituted chiral allyl esters with high enantiomeric excess from allyl phosphates is presented.

Externí odkaz: https://explore.openaire.eu/search/publication?articleId=doi_________::f6d3c287441c746471c1de803e449843
https://doi.org/10.1002/chin.201434075

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