A series of 2-substituted-1H-phenanthro[9,10-d]imidazoles were synthesized by a three-component, one-pot condensation of 9,10-phenanthrenedione, aromatic aldehydes and ammonium acetate using 3-(triethylammonio)propanesulfonic acid hydrosulfate ([TEAPS]HSO₄) as a novel acidic ionic liquid catalyst. Effect of the molar ratio, catalyst amount, solvent and reaction time on the yield was investigated. The optimum reaction conditions were determined and the possible mechanism was proposed. Moreover, the catalyst could be recovered conveniently and reused for at least four times without evident loss of activity. The products were identified by ¹H NMR, ¹³C NMR, IR and MS techniques. The present methodology offers several advantages such as milder conditions, shorter reaction time, excellent yields and environmental friendliness.

Key words: ionic liquid, [TEAPS]HSO₄, one-pot synthesis, 2-substituted-1H-phenanthro[9,10-d]imidazole