Highly chemo- and regioselective reaction of hydroxybenzenes with ${alpha},{eta}$-unsaturated compounds in acidic ionic liquid l-butyl-3-methylimidazolium hydrogen sulphate ([BMIM]HSO4) was reported for the first time. A series of oxa-Michael adducts and Friedel-Crafts alkylated products were synthesized with good yields. The acidic ionic liquid could be easily recycled for at least 5 times with only minor loss in activity.