Lewis base phase transfer catalyst promoted solvent‐free nucleophilic reactions in ionic liquids: Quantum chemical analysis for cooperative enhancement in <scp>S_N2</scp> reaction rates

Abstract We present quantum chemical analysis of Lewis base phase transfer catalyst (PTC) facilitated solvent‐free nucleophilic reactions in green solvent/catalyst ionic liquids (ILs). We adopt two nucleophilic processes: First, we examine whether and how the reaction rate of 18‐crown‐6‐promoted S N 2 reaction is further enhanced by the IL [Bmim]OMs. Second, we examine the promotion of S N 2 cynation by the IL‐integrated aza‐crown ether, and third, the S N 2 fluorination facilitated by [2.2.2]‐cryptand in the IL. Interactions between the IL, PTC and the substrates are shown to give rise to lower Gibbs free energies of activation, with the IL anion (OMs − ) acting as an additional Lewis base promoter on the counter‐cation M + , (M = K, Cs), thereby further mitigating the latter's disadvantageous influence on the nucleophile. We thus propose that the ILs may be used to facilitate the nucleophilic processes as solvent/ organocatalysts instead of environmentally malicious organometallic compounds.