The influence of electronic perturbations on the Sulfur–Fluorine Gauche Effect

[Display omitted] •Solution phase conformer populations determined using NMR.•A gauche arrangement predominates over the anti.•The gauche conformer molar fractions notably depend on the para-phenyl substituent.•Average gauche populations increase in the order sulfide, sulfone and sulfoxide. Herein, a solution phase NMR conformer population analysis is employed to probe the effect of remote electronic perturbations on the conformational equilibria of a series of para-substituted β-fluorosulfides (1), sulfoxides (2) and sulfone derivatives (3). Conformations that allow for stabilizing stereoelectronic (σC–H→σ*C–F) and electrostatic (Fδ−…Sδ+) interactions predominate: this is consistent with the Sulfur–Fluorine Gauche Effect. The molar fractions (χ) of the two possible gauche conformers correlate linearly with the electron-withdrawing aptitude of the para-substituent, rendering the system ideally suited for a Hammett-type analysis. Despite the clear influence that the remote para-substituents have on conformer population, this is superseded by the oxidation state on sulfur (II, IV, VI), where an increased preference for the gauche conformer follows the trend: sulfide