Reactions between Nucleophiles and Sulfonium Ions Containing Electron-withdrawing Substituents

Sulfonium ions containing electron-withdrawing substituents are formed by the reactions between sulfonium ylides and suitable electrophiles. Reactivities of these sulfonium ions (MeR+S–CX(CO2Me)2) with nucleophiles (Y−) are investigated. The products found are those of 1) C-attack (MeSR+YCX(CO2Me)2), 2) Me-attack (MeY+RSCX(CO2Me)2) and 3) R-attack (RY+MeSCX(CO2Me)2). When R is (+)-2-octyl and Y− is bromide ion, the RY found is (−)-2-octyl bromide with 59% optical purity. The mechanism of these reactions are discussed.