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Asymmetric Allylic Substitution Reactions (asymmetric + allylic_substitution_reaction)
Selected AbstractsPreparation of Chiral Homoannularly Bridged N,P-Ferrocenyl Ligands by Intramolecular Coupling of 1,5-Dilithioferrocenes and Their Application in Asymmetric Allylic Substitution Reactions,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 33 2007Shin-ichi Fukuzawa Abstract Homoannularly bridged ferrocene 6b was prepared by intramolecular coupling of 1,5-dilithioferrocene 5b mediated by Fe(acac)3. Dilithioferrocene 5b was prepared by lithium,halogen exchange of the corresponding diiodide, which was prepared by 1,5-dilithiation of the o -TMS-blocked ferrocene and followed by trapping with iodine and removal of the TMS group. Alternatively, 5b could be readily prepared by the reaction of o -bromophenylferrocene 8 with nBuLi (>2 equiv.). The benzene ring of 6b underwent ortho lithiation with tBuLi, and the resulting lithiated species was trapped with Ph2PCl to produce corresponding aminophosphane 7d. Aminophosphane 13, which has the phosphanyl group on the cyclopentadienyl ring, was prepared by intramolecular coupling of 1,5-dilithiated PhPPFA 11 mediated by Fe(acac)3. New N,P ligands 7d and 13 were used in the palladium-catalyzed allylic alkylation and amination of 1,3-diphenyl-2-propenyl acetate (14), and ligand 7d was found to give good yields with enantioselectivities as high as 96,% ee. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Modular Furanoside Diphosphite Ligands for Pd-Catalyzed Asymmetric Allylic Substitution Reactions: Scope and LimitationsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2005Montserrat Diéguez Abstract We have synthesized a library of furanoside diphosphite ligands for the Pd-catalyzed allylic substitution reactions of acyclic and cyclic allylic esters. The library has been designed to rapidly screen the ligands to uncover their important structural features and to determine the scope of diphosphite ligands in these catalytic reactions. After the systematic variation of the sugar backbone, the substituent at C-5 and the phosphite moieties, the diphosphite ligand 4c was found to be optimal in the Pd-catalyzed asymmetric allylic substitution of hindered (S1) and unhindered (S2,S5) substrates, yielding high activities [TOFs up to >3000,mol×(mol×h),1] and enantioselectivities (ees up to 99%). In addition, the screening of the library enabled us to find other suitable ligands for hindered disubstituted linear substrate S1 (ligands 1b,d, g and 4b, d, g) and for unhindered cyclic substrates S3,S5 (ligands 6c and 7c). [source] ChemInform Abstract: Palladium-Catalyzed Asymmetric Allylic Substitution Reactions Using New Chiral Phosphinooxathiane Ligands.CHEMINFORM, Issue 24 2001Hiroto Nakano 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] ChemInform Abstract: Asymmetric Allylic Substitution Reactions of 2-Substituted 2-Cycloalkenyl Carbonates Using 9-PBN Coordinated Palladium.CHEMINFORM, Issue 23 2001Yasumasa Hamada 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] Pyranoside Phosphite-Oxazoline Ligand Library: Highly Efficient Modular P,N Ligands for Palladium-Catalyzed Allylic Substitution Reactions.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009A Study of the Key Palladium Allyl Intermediates Abstract We have screened a library of modular phosphite-oxazoline ligands for asymmetric allylic substitution reactions. The library is efficiently prepared from the commercially available and cheap D -glucosamine. The introduction of a phosphite moiety into the ligand design is highly advantageous for the product outcome. Therefore, this ligand library affords good-to-excellent reaction rates [TOFs up to 600 mol substrate×(mol Pd×h),1] and enantioselectivities (ees up to 99%) and, at the same time, shows a broad scope for mono-, di- and trisubstituted linear hindered and unhindered substrates and cyclic substrates. The NMR studies on the palladium allyl intermediates provide a deeper understanding about the effect of the ligand parameters on the origin of enantioselectivity. [source] New Carbohydrate-Based Phosphite-Oxazoline Ligands as Highly Versatile Ligands for Palladium-Catalyzed Allylic Substitution ReactionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 15 2005Yvette Mata Abstract We have designed and synthesized a new family of readily available phosphite-oxazoline ligands for Pd-catalyzed asymmetric allylic substitution reactions. These ligands can be tuned in two regions to explore their effect on catalytic performance. By carefully selecting the ligand components, we obtained high enantioselectivities in the Pd-catalyzed allylic substitution in substrates with different steric properties [source] | ||||||||||