2-Ferrocenyl- and 2-phenyl-
N-
n-butylbenzimidazoles were synthesized to evaluate the influence of thebenzimidazole functional group upon their directed lithiation. The regiochemistry of lithiation was studied,as well as the effect of stabilization of the lithiated species by diamine coordination using tetramethyl-ethylenediamine and (-)-sparteine. The lithiations were followed by reaction with a variety of electrophilesto give the disubstituted 2-ferrocenyl- and 2-phenyl-
N-
n-butylbenzimidazoles compounds. This studyshowed that despite a simple
n-butyl function on the benzimidazole, directed lithiation was readily achievedwith high regiocontrol on the ferrocenyl and phenyl groups. (-)-Sparteine failed to provide asymmetricinduction in the ferrocene system, and its inefficiency is explained by intramolecular coordination of thelithiated species by the benzimidazole nitrogen, which is preferred over sparteine coordination.
