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Enantioselective Metalation of N , N ‐Diisopropylferrocenecarboxamide and Methyl Ferrocenecarboxylate Using Lithium‐Metal Chiral Bases
Author(s) -
Dayaker Gandrath,
Tilly David,
Chevallier Floris,
Hilmersson Göran,
Gros Philippe C.,
Mongin Florence
Publication year - 2012
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201200965
Subject(s) - chemistry , dilithium , enantioselective synthesis , lithium (medication) , zincate , zinc , metalation , medicinal chemistry , cobalt , alkyl , metal , substrate (aquarium) , ligand (biochemistry) , inorganic chemistry , organic chemistry , catalysis , deprotonation , ion , medicine , oceanography , geology , endocrinology , biochemistry , receptor
Abstract 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.