Efficient synthesis of 2,4,5-tri substituted imidazoles catalyzed by an ionic liquid derived from hexamine and 1,4-butane sultone under solvent-free conditions

The HMTA-[(CH2)(4)-SO3H](4)(4+)(HSO4-)(4) ionic liquid derived from hexamethylene-tetramine and 1,4-butane sultone was applied as an efficient and effective catalyst for synthesis of 2,4,5-tri-substituted imidazole derivatives. These heterocycles were obtained from benzil, ammonium acetate and substituted benzaldehydes under solvent free and thermal conditions. The characteristic features of catalyst were inferred from infrared (FT-IR) and H-1 NMR spectroscopy. The results showed that the novel catalyst was very effective for the reaction, with ability of excellent water and acid resistance. This ionic liquid is including four SO3H groups, so that the catalyst made extremely high acidity. Also, it has high polarity, which made the recycling of the catalyst very convenient and possible. The operational simplicity, low cost of used catalyst, high yields, short reaction times, wide applicability and reusability of catalyst are the key features of this new methodology. Therefore, this novel catalyst has great potential for use in green processes.