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Various Electrophiles (various + electrophile)

Distribution by Scientific Domains

Chemistry	100%

Selected Abstracts

Diastereoselective Alkylation of (Arene)tricarbonylchromium and Ferrocene Complexes Using a Chiral, C2 -Symmetrical 1,2-Diamine as Auxiliary

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 7 2005
Alexandre Alexakis
Abstract The aminal of (benzaldehyde)tricarbonylchromium and en-antiopure bipyrrolidine undergoes diastereoselective ortho -metallation with butyllithium. Quenching with various electrophiles, followed by hydrolysis of the aminal, affords ortho -substituted (benzaldehyde)tricarbonylchromium compounds with high ee (91,99,%). When quenched with Ph2PCl, a new chiral P,N-bidentate ligand is obtained, which shows efficiency in Pd- and Cu-catalysed reactions. The aminal of ferrocenecarbaldehyde could also be formed, but the ortho -deprotonation occurs with only moderate diastereoselectivity (70,%). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

Lithiation of 2-Aryl-2-(chloroaryl)-1,3-dioxolanes and Its Application in the Synthesis of New ortho -Functionalized Benzophenone Derivatives

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2004
Gyula Lukács
Abstract 2-Aryl-2-(chloroaryl)-1,3-dioxolanes 4 were lithiated ortho to the ketal group of the chloroaryl ring by treatment with butyllithium in THF between ,78 and 0 °C. The site selectivity of some of the deprotonation reactions was rationalized by the long-range effect of the 4-chloro substituent. The lithio species thus generated were treated with various electrophiles to give ortho -functionalized benzophenone derivatives. Intramolecular competition between the aryl rings was observed in the lithiation of 2-(4-chlorophenyl)-2-(4-fluorophenyl)-1,3-dioxolane (4s). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

1,3,5-Triaza-7-phosphaadamantane (PTA): A Practical and Versatile Nucleophilic Phosphine Organocatalyst

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2007
Xiaofang Tang
Abstract In this paper, the air-stable and readily available 1,3,5-triaza-7-phosphaadmantane (PTA) is reported as a practical and versatile nucleophilic phosphine organocatalyst. Under the mediation of 15,30 mol,% of PTA, various electrophiles like aldehydes and imines readily undergo the Morita,Baylis,Hillman reactions with a variety of activated olefins, giving the corresponding adducts in high yields. In the phosphine-catalyzed [3+2] cycloaddition reaction of 4-substituted 2,3-butadienoates with N -tosylimines, PTA is also proven to be a comparable catalyst as tributylphosphine (PBu3). By systematic comparison with other structurally similar N,P catalysts, it is concluded that the superiority of PTA in the above nucleophilic catalysis is attributable to its comparable nucleophilicity with that of trialkylphosphines. The feasibility to use PTA as an alternative catalyst in place of the air-sensitive trialkylphosphines is also discussed. [source]

Selective Mono- and 1,2-Difunctionalisation of Cyclopentene Derivatives via Mg and Cu Intermediates

CHEMISTRY - A EUROPEAN JOURNAL, Issue 8 2008
Christina Despotopoulou Dipl.
Abstract A single Br/Mg exchange of 1,2-dibromocyclopentene with iPrMgCl, LiCl provides the corresponding ,-bromocyclopentenylmagnesium reagent, which can then be reacted with various electrophiles (yields: 65,82,%). In the presence of a secondary alkylmagnesium halide and Li2CuCl4 (2,mol,%), these 2-bromoalkenylmagnesium compounds undergo bromine substitution and can then further react with electrophiles to give 1,2-difunctionalised cyclopentenes (63,79,%). The mechanism of this process is discussed. Durch einen Br/Mg-Austausch an 1,2-Dibromcyclopenten mit iPrMgCl,LiCl werden die entsprechenden , -Bromcyclopentenyl-magnesium-Verbindungen erhalten, die anschließend mit verschiedenen Elektrophilen umgesetzt werden (65,82,%). Zusätzlich können diese 2-Bromalkenylmagnesium-Verbindungen in Anwesenheit eines sekundären Alkylmagnesiumhalogenids und Li2CuCl4 (2,mol,%) eine Bromsubstitution eingehen und danach mit verschiedenen Elektrophilen abgefangen werden, sodass 1,2-difunktionalisierte Cyclopentenderivate (63,79,%) erhalten werden. Zusätzlich wird der Mechanismus dieser Reaktion diskutiert. [source]