One-Pot Efficient Synthesis of 2-Aryl-1-arylmethyl-1H-benzimidazoles and 2,4,5-Triaryl-1H-imidazoles Using Oxalic Acid Catalyst

摘要

Oxalic acid was found to be a versatile catalyst for the synthesis of 2-aryl-1-arylmethyl-1H-benzimidazoles and 2-aryl-4,5-diphenyl-1H-imidazoles in moderate to excellent isolated yields. 2-Aryl-1-arylmethyl-1H-benzimidazoles were efficiently synthesized from o-phenylenediamine and various substituted aldehydes using 10 mol% oxalic acid. 2-Aryl-4,5-diphenyl-1H-imidazoles were synthesized from benzil or benzoin, ammonium acetate, and aromatic aldehydes. The advantages of this method are the use of an inexpensive and readily available catalyst, easy workup, and improved yields, and the use of an ethanol-water solvent that is considered to be relatively environmentally benign.