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12.13: Protecting Groups for Aldehydes and Ketones: Introduction

JoVE Core
Organic Chemistry

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Protecting Groups for Aldehydes and Ketones: Introduction

12.13: Protecting Groups for Aldehydes and Ketones: Introduction

Protecting groups are compounds that can bind to a specific functional group in the presence of other functional groups to protect them from undesired chemical reactions. These compounds can selectively bind to particular functional groups and advance chemoselective reactions in polyfunctional systems (Figure 1). After the functional group has served its purpose, it is removed by reacting it with specific compounds.


The aldehydes and ketones can be selectively protected in the presence of other carbonyl groups such as esters or acids based upon their reactivity. This is important for the manipulation of one functional group over the other.

For instance, when carrying out a reduction reaction in the presence of an ester and a ketone, the ketone will always be preferentially reduced to alcohol. In order to achieve the selective reduction of an ester to an alcohol while keeping the ketone unaffected, the ketone group needs to be protected (Figure 2, first step). After the ketone is protected, the ester is reduced to an alcohol using LiAlH4 (Figure 2, second step). Finally, the ketone is regenerated by removing the protecting group (Figure 2, third step).


Acetals and thioacetals are the most commonly used protecting groups for aldehydes and ketones and can be easily removed. In addition, they are resistant to chemical species such as nucleophiles, or reducing and oxidizing agents.


Protecting Groups Aldehydes Ketones Functional Groups Chemical Reactions Chemoselective Reactions Polyfunctional Systems Carbonyl Groups Esters Acids Reactivity Reduction Reaction Alcohol Selective Reduction LiAlH4 Regeneration Acetals Thioacetals Nucleophiles Reducing Agents Oxidizing Agents

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