Pyrene-Tagged Ionic Liquids: Separable Organic Catalysts for S<sub>N</sub>2 Fluorination

We prepared pyrene-substituted imidazolium-based ionic liquids (PILs) as organic catalysts for the S<sub>N</sub>2 fluorination using alkali metal fluoride (MF). In this system, the PIL significantly enhanced the reactivity of MF due to the phase-transfer catalytic effect of the imidazolium moiety as well as the metal cation−π (pyrene) interactions. Furthermore, this homogeneous catalyst PIL was easily separated from the reaction mixture using reduced graphene oxide by π–π stacking with the pyrene of PIL.