Benzimidazolium salts chiral

For a recent study by Benaglia et al. on chiral benzimidazolium and thiazolium salts, affording up to 15% ee in the condensation of benzalde-hyde, see S. Oriandi, M. Caporale, M. Benaglia, R. Annunziata, Tetrahedron Asymmetry 2003, 34, 3827-3830. 

Bridging of two carbene donor groups with the 1,1 -binaphthyl moiety led to ligands with axial chirality. Bis-imidazolium salt 56 and the analogous benzimidazolium derivative belong to these ligand precursors as well as the hydroxyl substituted mono-imidazolium derivative 57. Additional examples for carbenes and carbenes precursors with chiral modified N-heterocycles are presented in Schemes 1.7 and 1.8. 

---