Concerning the denticity of the dimethylsulfinyl anion in Meisenheimer complexation

The denticity (O-, S-, and C-nucleophilic reactivity) of the dimethylsulfinyl carbanion ("dimsyl") toward 1,3,5-trinitrobenzene (TNB) has been studied by NMR spectroscopy, and structures of adducts have been assigned. Three dimsyl adducts are observed for the first time and have been ascribed to the O-adduct 15, the S-adduct 16, and the C-adduct 17. The kinetic (15 > 16 > 17) and thermodynamic preference (17 > 16 > 15) for the reactivity of dimsyl toward TNB is compared to the known O- and C-reactivity of enolate anions and the O- and S-reactivity of dimethyl sulfoxide. Thus, dimsyl apparently represents a unique system in which three adjacent atoms having unshared electron pairs can utilize these in covalent bond formation.