Facile Aldol Reaction Between Unmodified Aldehydes and Ketones in Bronsted Acid Ionic Liquids

A series of condensation reactions of unmodified ketones and aromatic aldehydes to prepare α,β-unsaturated carbonyl compounds by means of Aldol reactions in Bronsted acid ionic liquids (BAILs) was explored. 1-Butyl-3-methylimidazolium hydrogen sulphate (BMImHSO4) acting as an effective media and catalyst in aldol reactions was compared with other BAILs, with the advantages of high conversion and selectivity. The product was easily isolated and the left ionic liquid can be readily recovered and reused at least 3 times with almost the same efficiency. The scope and limitation of the present method were explored and the possible catalytic mechanism was speculated.