Highly Selective Aromatic Alkylation of Phenol and Anisole by Using Recyclable Brønsted Acidic Ionic Liquid Systems

A highly efficient ionic liquid catalyst system for selective alkylation of phenol and anisole with alkenes is described. By using Brønsted acidic triflate ionic liquids containing the SO3H group attached to the cation, it was possible to recycle the catalyst and reuse it after a simple workup procedure. Moreover, selectivity towards the monoalkylated products was improved to 93 % by using a biphasic system. A sulfonic acid functionalized ionic liquid is used as catalyst in the hexylation of phenol and anisol, enabling very high product selectivities, simple product isolation and effective catalyst recycling. The observed selectivity boost is mainly due to differential solubility effects of the liquid–liquid biphasic reaction system established by the ionic liquid catalyst.