Novel Multiple-Acidic Ionic Liquids: Catalysts for Environmentally Friendly Benign Synthesis of trans-β-Nitrostyrenes under Solvent-Free Conditions

A series of novel multiple-acidic ionic liquids, sulfated from the low-cost starting material 2-aminoethanol, were introduced as catalysts for the Henry reaction of versatile aldehydes and nitroalkane under solvent-free conditions. The ionic liquid with hydrogen sulfate as a counteranion showed the best catalytic efficiency and gave the corresponding trans -β-nitrostyrenes in good to excellent yields. More importantly, the ionic liquid catalyst could be readily recovered and reused six times without considerable loss of its catalytic activity.