d-/l-Isoleucine chirality could be differentiated using IRMPD spectroscopy, ion-mobility mass spectrometry, and DFT calculations for the permethylated β-cyclodextrin non-covalent complex.

Scheme 1. Synthetic pathway for the ATDBF.

We examine the mechanism of S N 2 fluorination promoted by a pyrene-tagged ionic liquid (PIL). Comparison is made for contact ion-pair (CIP) vs. solvent-separated ion-pair (SSIP) mechanism by calculating the Gibbs free energies of pre-reaction complexes and Gibbs free energies of activation G ‡ for both processes. We find that the CIP mechanism is preferred for [PIL + MF + C 3 H 7 OMs] (M = Cs, K) system. S N 2 fluorination of the [1-Butyl-3-methylimidazolium (bmim)-CsF] system is also studied in order to estimate the efficacy of PIL vs. more conventional ionic liquid [bmim] [OMs]. The better promotion of the reaction by PIL is attributed to π interactions between the metal cation and pyrene, giving G ‡ that is smaller (by approximately 1.3 kcal/mol) than that for the [bmim-CsF] system, in excellent agreement with experimental observations.