Green Synthesis of 2-Substituted Imidazolines using Hydrogen Peroxide Catalyzed by Tungstophosphoric Acid and Tetrabutylammonium Bromide in Water

摘要

Various 2-substituted imidazolines were constructed from aromatic aldehydes with ethylenediamine using hydrogen peroxide as an oxidant in water. Tungstophosphoric acid (HPW) was found to be active for this transformation due to its ubiquitous catalytic and oxidative nature, and further combination of tetrabutylammonium bromide (TBAB) made this transformation more efficient and attractive. It was found that the yields of the corresponding 2-substituted imidazolines were markedly influenced by the position and nature of the substituents on the phenyl ring. A plausible mechanism was also proposed to clarify this catalytic oxidative system.