A simple, highly efficient and eco-friendly protocol for the synthesis of bioactive 2,4,5-trisubstituted-1 H -imidazoles via one-pot three component condensation of benzil, aromatic aldehydes and ammonium acetate under solvent free conditions has been achieved utilizing the novel Bronsted acidic ionic liquid, (L-pyrrolidine-2-carboxylic acid sulfate) as catalyst. The distinguishing features of this methodology are excellent yields in shorter reaction time, cleaner reaction profile, and environmentally friendly nature, use of non-toxic, easily synthesizable, inexpensive catalyst.