Comparison of the present method with previous literature for the one-pot multicomponent synthesis of benzo[4,5]imidazo[1,2-a]pyrimidine.

Entry	Catalytic system	Reaction conditions	Yield (%)
1	1,1,3,3-N,N,N′,N′-Tetramethylguanidinium trifluoroacetate (30 mol%)	100 °C, 5 h	73 (ref. 26)
2	[bmim][BF4] (3 mL)	90 °C, 7 h	86 (ref. 36)
3	l-Proline (20 mol%), H2O	Reflux, 3 h	91 (ref. 30)
4	Thiamine hydrochloride (5 mol%), H2O	Reflux, 3 h	90 (ref. 41)
5	α-Zirconium sulfophenylphosphonate (12 mol%)	80 °C, 20 h	73 (ref. 42)
6	Current work: [(4-SO3H)BMIM]HSO4 (10 mol%), solvent-free	100 °C, 2 h	92