Abstract Benzoquinazolin-2-one derivatives were synthesized by using a catalytic amount of task specific ionic liquid,[1-methyl-3-(4-sulfobutyl) imidazolium-4-methylbenzenesulfonate] through a one-pot multicomponent Biginelli reaction of α-tetralone, aldehyde, and urea/thiourea in excellent yields within a short reaction time. Mechanism studies suggest that the reaction proceeds through iminium intermediate and C2-H of the TSIL plays a ...