Chapter 23.SE, Problem 72AP

Interpretation Introduction

Interpretation:

Given that the third and fourth steps in the synthesis of Hagemann’s ester from ethyl acetoacetate are intramolecular aldol cyclization to yield a substituted cyclohexenone and a decarboxylation reaction. Both reactions are to be shown and products of each step are to be shown.

Concept introduction:

In intramolecular aldol reactions dicarbonyl compounds such as diketones react with a base to yield a cyclic enone as the products. The reaction occurs in three steps i) Abstraction of α-hydrogen by a base to yield an enolate anion ii) Attack of the anion on the carbonyl carbon in the same molecule iii) Protonation of the alkoxide intermediate.

A β-ketoacid normally eliminates CO₂ on heating.

To show:

The third and fourth steps in the synthesis of Hagemann’s ester from ethyl acetoacetate, the intramolecular aldol cyclization to yield a substituted cyclohexenone and a decarboxylation reaction and further to show the products of these reactions.