Boric Acid Catalyzed Convenient Synthesis of Benzimidazoles in Aqueous Media

Synthesis of benzimidazoles has been developed by theo-phenylenediamine with aldehydes using boric acid an efficient catalyst under mild reaction conditions in aqueous media. The product is applicable to aryl and heteroaryl aldehydes. This reaction led to the formation of benzimidazoles new derivatives in good yields. The FT-IR,19F-NMR,1H-NMR,13C-NMR spectra and elemental analysis confirm the structure of compounds.

2-Amino-N-(2-benzyloxy-3-methoxybenzylidene)aniline

The title compound, C₂₁H₂₀N₂O₂, a Schiff base ligand, contains two independent mol­ecules (A and B) in the asymmetric unit, with similar conformations. In mol­ecule A, the central benzene ring forms dihedral angles of 30.79 (13) and 23.56 (13)°, respectively, with the amino and benzyl benzene rings, while in mol­ecule B these angles are 32.30 (13) and 13.13 (12)°. The mol­ecular structure is stabilized by intra­molecular N—H⋯N and C—H⋯O hydrogen bonds. The crystal structure is stabilized by N—H⋯N hydrogen bonds and N—H⋯π and C—H⋯π inter­actions.

NMR investigation of hydrogen bonding and 1,3-tautomerism in 2-(2-hydroxy-5-substituted-aryl) benzimidazoles

The 1,3-tautomerism associated with 2-(2-hydroxy-5-substituted-aryl)benzimidazoles was studied in different solvents. The effect of hydrogen bonding involving the hydroxyl group of the 2-aryl ring on the tautomerism was investigated using NMR spectroscopy. The influence of the solvent concentration on 2-(2-hydroxy-5-chloroaryl)benzimidazole was studied in acetone-d6 and DMSO-d6.