Chapter 17, Problem 17.71P

Interpretation Introduction

Interpretation:

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

Concept introduction:

In the Corey-Chaykovsky aziridination reaction, the sulfonium ylide reacts with imines, leading to the corresponding aziridine. An aziridine is a three memebered ring, having a nitrogen atom along with two carbons. The sulfonium ylide can be generated from alkyl halides by reacting it with dimethyl sulfide, followed by 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 which, on deprotonation by sodium hydride, produces sulfonium ylide. The negatively charged carbon of an ylide acts as a nucleophile and attacks the electrophilic carbon of imine and forms an intermediate, which has the negative charge on the nitrogen and positive charge on the sulfur atom. The negatively charged N atom is a good nucleophile, and ${{\text{(CH}}_{\text{3}}\text{)}}_{\text{2}}\text{S}$ is a good leaving group. Thus it undergoes an intramolecular ${\text{S}}_{\text{N}}\text{2}$ reaction to produce the corresponding aziridine on elimination of the ${{\text{(CH}}_{\text{3}}\text{)}}_{\text{2}}\text{S}$ group.