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What is the major product formed when 1-chloro-3-iodopropane reacts with diphenyl sulfide in the presence of one equivalent of $\ce{AgBF4}$?

Reaction scheme

I know that sulfur is nucleophilic and that it can displace a halide in a SN2 reaction, but the resulting molecule will have a positive charge. Is that okay? What possible use does the product have?

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In the presence of $\ce{AgBF4}$, diphenylsulfide is alkylated to 3-chloropropyl diphenylsulfonium tetrafluoroborate. The sulfonium salt is stable and can be isolated as a crystalline product.

alkylation of disulfide


This sufonium salt can be deprotonated (e.g. with $\ce{NaH}$ in $\ce{THF}$) to the corresponding sulfonium ylide. cyclization

In the latter, intramolecular displacement of $\ce{Cl-}$ yields cyclopropyl diphenylsulfonium tetrafluoroborate, which again is a stable solid.

This cyclopropyl derivative, once converted to its sulfonium ylide S may serve as a reagent in the Corey–Chaykovsky reaction.

Corey–Chaykovsky epoxidation

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