Chapter 20, Problem 20.19P

Interpretation Introduction

Interpretation:

It is to be explained how to carry out the given transformation.

Concept introduction:

The reduction of an ester group $\left({\text{CO}}_{\text{2}}\text{R}\right)$ to the corresponding alcohol is done by using a strong reducing agent, lithium aluminum hydride $\left({\text{LiAlH}}_{\text{4}}\right)$. But the ester group is less reactive as compared to the ketone. When both ketone and ester group are present in a compound, both are reduced by ${\text{LiAlH}}_{\text{4}}$. To reduce the ester group selectively, ketone group must be protected. Ketone, on treatment with $\text{1, 2-diol}$ in acidic medium, forms five-membered ring acetal, which is stable under the basic condition and not reduced by ${\text{LiAlH}}_{\text{4}}$. So the ketone is protected in the form of acetals. For the deprotection, dilute acid is used.