Mechanism of oxidation of aryl methyl sulfoxides with sodium hypochlorite catalyzed by (salen)MnIII complexes

The oxidation of organic sulfoxides to sulfones with sodium hypochlorite catalyzed by (salen)MnIII complexes in 90% acetonitrile–10% water (v/v) follows an overall second-order kinetics, first-order each in the oxo complex and the substrate. The less nucleophilic sulfoxides are more sensitive to substituent effect (ρ = −2.57) compared to the corresponding sulfides (ρ = −1.85). A positive ρ-value (ρ = 0.50) is observed in the oxidation of phenyl methyl sulfoxide by substituted oxo(salen)manganese(V) complexes. Substituent, acid and solvent effect studies reveal the operation of a common SN2 mechanism. Correlation analyses establish that there is an inverse relationship between reactivity and selectivity in both the sulfoxide and complex series. A valid reactivity–selectivity principle (RSP) is observed in this redox system.

Graphical abstract(Salen)MnIII complexes catalyzed NaOCl oxidation of aryl methyl sulfoxides to sulfones in 90% acetonitrile–10% water (v/v) follows an overall second-order kinetics, first-order each in the oxo complex and the substrate. The less nucleophilic sulfoxides are more sensitive to substituent effect compared to the corresponding sulfides. Substituent, acid and solvent effect studies reveal the operation of a common SN2 mechanism. A valid reactivity–selectivity principle is observed in this redox system. Figure optionsDownload full-size imageDownload as PowerPoint slide