The tautomerism of five symmetrically substituted 2,2'-bis-benzimidazoles [5(6),5'(6')-tetramethyl- (1); 5(6),5'(6')-dimethyl-(2); 5(6),5'(6')-dichloro- (3); 5(6),5'(6')-dimethoxy- (4) and 4(7),4'(7')-dimethyl-2,2'-bis-benzimidazole (5)], was studied by means of ¹H NMR spectroscopy at variable temperatures, and the influence of the substituents on the energy barriers for tautomeric interconversion was interpreted with the aid of theoretical calculations.
bis-benzimidazoles; tautomerism; dynamic NMR
