Concerted bimolecular substitution reactions of anilino thioethers

Article abstract of DOI:10.1021/ja00142a005

The anilino thioethers, 3-NO₂-C₆H₄N(CH₃)CH ₂SC₆H₄-2-COO^- (1) and 4-NO₂-C₆H₄N(CH₃)CH ₂SC₆H₄-2-COO^- (2) undergo concerted bimolecular nucleophilic substitution (A_ND_N) with nucleophilic reagents in aqueous solution at 25 °C that is enforced by the absence of a significant lifetime for the corresponding iminium ion^?-SAr intermediates. Electron donation from the aniline nitrogen atom provides assistance to the nucleophilic reaction and results in a dissociative character for the transition state of the reaction. A Swain-Scott correlation with s ≈ 0.4 indicates an early transition state for bond formation, with a low sensitivity of the nucleophilic reaction toward the attacking nucleophile.