10.1021/jo991731o.s001 Riccardo Destro Riccardo Destro Vittorio Lucchini Vittorio Lucchini Giorgio Modena Giorgio Modena Lucia Pasquato Lucia Pasquato X-ray Structures and Anionotropic Rearrangements of Di-<i>tert</i>-butyl-Substituted Thiiranium and Thiirenium Ions. A Structure−Reactivity Relationship American Chemical Society 2000 butyl groups trans tert thietanium ion BF thietium ion Anionotropic Rearrangements steric hindrance 8 SbCl 6 Thiirenium Ions 11 SbCl 6 methylthiiranium rearrangement intramolecular S N 2 displacements 2000-05-11 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/X-ray_Structures_and_Anionotropic_Rearrangements_of_Di-_i_tert_i_-butyl-Substituted_Thiiranium_and_Thiirenium_Ions_A_Structure_Reactivity_Relationship/3720507 The X-ray structures of <i>c</i>-2,<i>t</i>-3-di-<i>tert</i>-butyl-<i>r</i>-1-methylthiiranium <b>8 </b>BF<sub>4</sub><sup>-</sup>, <i>t</i>-2,<i>t</i>-3-di-<i>tert</i>-butyl-<i>r</i>-1-methylthiiranium ion <b>10 </b>BF<sub>4</sub><sup>-</sup>, and 2,3-di-<i>tert</i>-butyl-1-methylthiirenium <b>11 </b>BF<sub>4</sub><sup>-</sup> have been determined. The Δ<i>G</i><sup>⧧</sup><sub>298</sub> values for the rearrangements from the cis and the trans <i>tert</i>-butyl groups of <b>8</b> SbCl<sub>6</sub><sup>-</sup> to thietanium ion (two intramolecular S<sub>N</sub>2 displacements) and for the rearrangement of <b>11</b> SbCl<sub>6</sub><sup>-</sup> to thietium ion (an intramolecular S<sub>N</sub>2-Vin displacement) are linearly correlated with the strengths of the C−S breaking bonds, suggesting that the two mechanisms are, in the absence of steric hindrance, uniquely governed by the nucleofugality of the sulfonium leaving group.