The reaction between phenyl methyl sulphonium bis (methoxycarbonyl) methylide and either acetic anhydride or benzoyl peroxide proceeds via “Pummerer” type rearrangement to afford phenyl α-acyloxymethyl sulphide. The kinetic data suggest that the rate-determining step involves S C bond cleavage after initial acylation or acyloxylation and subsequent proton removal by acyloxy anion unlike the corresponding reaction of the analogous ...