An environmental friendly approach for the synthesis of highly substituted imidazoles using Brønsted acidic ionic liquid, N-methyl-2-pyrrolidonium hydrogen sulfate, as reusable catalyst

► Brønsted acidic ionic liquid, N-methyl-2-pyrrolidonium hydrogen sulfate, has been used as an catalyst. ► One-pot pseudo four-component synthesis of 2,4,5-trisubstituted imidazoles is reported. ► Four-component synthesis of 1,2,4,5-tetrasubstituted imidazoles is described. ► Substituted imidazoles were prepared under thermal solvent-free conditions in excellent yields. ► The recovered ionic liquid was reused for seven cycles without loss of its activities.