Chapter 17, Problem 17.72P

Interpretation Introduction

Interpretation:

Detailed mechanism for the given example of the Corey-Chaykovsky cyclopropanation reaction is to be drawn.

Concept introduction:

In the Corey-Chaykovsky cyclopropanation reaction, the dimethyloxosulfonium methylide reacts with $\text{α,β-}$ unsaturated ketones, leading to the corresponding cyclopropanes. The dimethyloxosulfonium methylide can be generated from alkyl halides by reacting it with dimethyl sulfoxide (DMSO), followed by a strong base. In the first step, the reaction favors ${\text{S}}_{\text{N}}\text{2}$ mechanism in which the nucleophile ${{\text{(CH}}_{\text{3}}\text{)}}_{\text{2}}\text{S=O}$ attacks the carbon attached to the leaving group (halide anion). The organic product accommodates the positive charge on the sulfur atom, which, on deprotonation by sodium hydride, produces dimethyloxosulfonium methylide. The dimethyloxosulfonium methylide, on reaction with $\text{α,β-}$ unsaturated ketone, undergoes $\text{1, 4-}$ addition reaction, forming a cylcopropane ring at $\text{α,β-}$ carbons.