Chapter 17, Problem 17.57P

Interpretation Introduction

Interpretation:

The complete mechanism for each reaction in the given sequence is to be drawn.

Concept introduction:

The sulfonium ylide can be generated from alkyl halides. The alkyl halide is first reacted with dimethyl sulfide and the product of that reaction is treated with a strong base. In the first step, the reaction favors ${\text{S}}_{\text{N}}\text{2}$ reaction in which the nucleophile ${{\text{(CH}}_{\text{3}}\text{)}}_{\text{2}}\text{S}$ attacks the carbon attached to the leaving group (halide anion). The organic product accommodates the positive charge on the sulfur atom. Then, deprotonation is carried out by sodium hydride to produce sulfonium ylide. In the next step, the negatively charged C atom from the sulfonium ylide attacks the ketone and forms a new $\text{C-C}$ bond. The negatively charged O atom is a good nucleophile and ${{\text{(CH}}_{\text{3}}\text{)}}_{\text{2}}\text{S}$ is a good leaving group. Finally, an intramolecular ${\text{S}}_{\text{N}}\text{2}$ reaction is carried out and ${{\text{(CH}}_{\text{3}}\text{)}}_{\text{2}}\text{S}$ departs from it and produces an epoxide functional group.