Benzimidazole nitrogen-directed, regiocontrolled, lithiation of ferrocenyl- and phenyl-N-n-butylbenzimidazoles.
2-Ferrocenyl- and 2-phenyl-N-n-butylbenzimidazoles were synthesized to evaluate the influence of the benzimidazole 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 electrophiles to give the disubstituted 2-ferrocenyl- and 2-phenyl-N-n-butylbenzimidazoles compounds. This study showed that despite a simple n-butyl function on the benzimidazole, directed lithiation was readily achieved with high regiocontrol on the ferrocenyl and phenyl groups. (-)-Sparteine failed to provide asymmetric induction in the ferrocene system, and its inefficiency is explained by intramolecular coordination of the lithiated species by the benzimidazole nitrogen, which is preferred over sparteine coordination.
Hérault
Damien
D
Department of Chemistry, Durham University, Sciences Laboratories, South Road, Durham DH1 3LE, UK.
Aelvoet
Karel
K
Blatch
Alexandrea J
AJ
Al-Majid
Abdullah
A
Smethurst
Christian A
CA
Whiting
Andrew
A
D001562:Benzimidazoles / Q000138:chemical synthesis / Q000737:chemistry*; D001897:Boronic Acids / Q000737:chemistry; D007501:Iron / Q000737:chemistry*; D008094:Lithium / Q000737:chemistry*; D015394:Molecular Structure; D009584:Nitrogen / Q000737:chemistry*
D001562:Benzimidazoles; D001897:Boronic Acids; D008094:Lithium; D007501:Iron; C031000:benzimidazole; D009584:Nitrogen