Preparation and Structural Features of Lithium Cyclopentadienides that Contain Amino Acid-Derived Cp-Substituents

Treatment of N-protected amino acid active esters, e.g., 3, formed by the reaction of N,N-dibenzylalanine (2) with DCC and hydroxybenztriazole, with 2 molar equiv of CpLi gives the corresponding amino acid-substituted Cp-anion equivalents (e.g., 4). The X-ray crystal structure analysis of 4 has revealed a dimeric pentafulvenolate-type structure. Reaction of FeCl2 or (PPh3)3RuCl2 with compound 4 and related reagents yields the respective 1,1‘-difunctionalized metallocenes (7, 8).