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

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.