Enantioselective Metalation of N,N-Diisopropylferrocenecarboxamide and Methyl Ferrocenecarboxylate Using Lithium-Metal Chiral Bases - Université de Rennes Accéder directement au contenu
Article Dans Une Revue European Journal of Organic Chemistry Année : 2012

Enantioselective Metalation of N,N-Diisopropylferrocenecarboxamide and Methyl Ferrocenecarboxylate Using Lithium-Metal Chiral Bases

Résumé

Enantioselective deprotonative metalations of substituted ferrocenes using mixed lithium-metal bases are described. Using N,N-diisopropylferrocenecarboxamide as substrate, magnesium, iron, cobalt, zinc, and cadmium were tested as metals in bis[(S)-1-phenylethyl]amido-based combinations; after interception of the metalated species with iodine, very high enantiomeric excess (96 %) but low yield was obtained with cobalt, whereas zinc and cadmium only gave 27 and 30 % ee, respectively, but in excellent yields. The small alkyl groups methyl and ethyl were identified as particularly suitable in the reaction using the putative dialkyl bis[(S)-1-phenylethyl]amido-based lithium and dilithium zincates. The dimethyl dilithium zincate was selected for a study of dependency on the temperature, reaction time, and amount of base. Increased enantioselectivities with temperature, reaction time, and amount of base were noted (ee = 86 % at 0 °C after 2 h, 2 equiv. of base). The best result using methyl ferrocenecarboxylate as substrate was observed without alkyl ligand.

Domaines

Chimie organique

Dates et versions

hal-01053773 , version 1 (01-08-2014)

Identifiants

Citer

Gandrath Dayaker, David Tilly, Floris Chevallier, Göran Hilmersson, Philippe C. Gros, et al.. Enantioselective Metalation of N,N-Diisopropylferrocenecarboxamide and Methyl Ferrocenecarboxylate Using Lithium-Metal Chiral Bases. European Journal of Organic Chemistry, 2012, pp.6051-6057. ⟨10.1002/ejoc.201200965⟩. ⟨hal-01053773⟩
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