Sulfur Ylides and Related Species as Nucleophiles

Next to phosphorus ylides in importance as synthetic reagents are sulfur ylides, especially dimethylsulfonium methylide and dimethyloxosulfonium methylide. These sulfur ylides are prepared by deprotonation of the appropriate sulfonium 

Trost and L. S. Melvin, Jr., Sulfur Ylides, Academic Press, New York (1975). b. E. Block, Reactions of Organosulfur Compounds, Academic Press, New York (1978). 

There is an important difference between the reactions of these sulfur ylides and the analogous phosphorus ylides with carbonyl compounds. Whereas phosphorus ylides react with aldehydes and ketones to yield alkenes, dimethylsulfonium methylide and dimethyloxosulfonium methylide yield epoxides. Instead of a four-center elimination in the zwitterionic intermediate, intramolecular nucleophilic displacement by oxygen occurs. 

SECTION 2.7. SULFUR YLIDES AND RELATED SPECIES AS NUCLEOPHILES 

CHAPTER 2 REACTIONS OF CARBON NUCLEOPHILES WITH CARBONYL GROUPS 

---