Molecular rearrangements ylide reactions

Warming the sulfonium salt (5) may cause elimination of a p-hydrogen to yield a mixture of the sulfide and the alkene, i.e. route (iv) in Scheme 3. On the other hand, proton abstraction from (5) by treatment with a strong base gives the sulfur ylide (6) which can undergo molecular rearrangement to form the sulfide (7). Sulfonium salts are unstable in basic media as a result of their tendency to undergo nucleophilic substitution reactions. 

---