Regioselective Mononitration of Aromatic Compounds Catalyzed by Heteropolyanions-based Acidic Ionic Liquids

A Keggin heteropolyanions-based Bronsted acidic ionic liquid that combined an imidazolium cation with heteropolyanions was synthesized and used as a catalyst for regioselective mononitration of aromatic compounds in HNO3 (67%). The reactions were carried out at 60°C to 80°C with reasonable to good yields and improved para-selectivities for halogenobenzenes compared to those without the catalysts. In addition, this heteropolyanions-based ionic liquid could be recovered and reused at least five times without noticeable decrease in the catalytic activity.