The influence of substituents on the tautomerism of symmetrically substituted 2,2′-bis-benzimidazoles

Abstract

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.