Neighbouring group participation in reactions of sulphides with chloramine-t

Neighbouring group participation in reactions of chloramine-T with ortho-substituted aryl methyl sulphides and diaryl sulphides has been studied. The reaction is markedly hindered by the steric effect of the ortho substituent of the phenyl ring, but groups having a CO moiety show an anchimeric effect in the following order: o-CH₂CO₂Me ~ o-CH₂CO₂H < o-CH₂CO₂^- < o-CO₂Me ~ o-CO₂H < o-CO₂^- ? 2o-CO₂ in the rate-determining step may be ruled out on the basis of salt and isotope effect. Substituents with neighbouring group participation diminish the yield of sulphilimine in solvents containing water. The electrophilic chlorination of sulphides by TsNHCl may be assumed to be the rate-determining step with the positively charged sulphonium centre stabilized by the negatively polarized or charged carbonyl-oxygen in the transition state. This type of interaction hinders the nucleophilic attack of sulphonamidate ion at the sulphonium centre in the fast product-controlling steps, decreasing the yield of sulphilimine.