Dimethyl sulfonium reaction with alkenes

It is known that dimethyl sulfide (MeSMe) reacts with 1-bromobutane to form a sulfonium salt. Draw it. It is also known that treatment of this salt with butyllithium leads to an ylid (draw it) however, when this yhd reacts with acetone, the product is an epoxide (l-butyl-2,2-dimethyloxirane) rather than an alkene. The coproduct of this reaction is dimethyl sulfide. Suggest a mechanism that accounts for formation of this epoxide and MegS from the yhd. 

Furthermore, the transformation of alkenes into triazoles was also effectively performed in one pot by the reaction of dimethyl(methylthio)-sulfonium tetrafluoroborate and NaNa in MeCN in presence of CuNPs/C to produce the corresponding methylsulfanyl azide which further reacts with the alkyne to give the product (Scheme 31). 

The camphor-derived P-hydroxyl-sulfonium yhde proved to be unusually efficient for the cyclopropanation of electron-deficient alkenes. For example, the reaction of salt 21b with a,P-unsaturated nitrile affords the desired cyclopropane in 61% yield and 96% ee. In comparison, the corresponding tetrahydrothiophene and dimethyl sulfide-derived sulfonium salts (23 and 24), which lack the hydroxyl group, only gave a trace amount of the desired cyclopropane (Scheme 20.21). 

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