Dess–Martin oxidation is an organic reaction that converts primary alcohols into aldehydes and secondary alcohols into ketones using Dess–Martin periodinane (DMP). The reaction is particularly useful because it usually occurs under mild conditions without requiring strongly acidic or basic reagents. It can therefore be used with many compounds containing sensitive functional groups. ^[1–4]

The reaction is named after Daniel B. Dess and James C. Martin, who reported the periodinane reagent in 1983.

General Reaction

The product of a Dess–Martin oxidation depends on the type of alcohol used.^[1–5,7]

Primary Alcohol

A primary alcohol is oxidized to an aldehyde:

R–CH₂OH –{DMP}→ R–CHO

For example, 1-butanol is oxidized to butanal:

CH₃–CH₂–CH₂–CH₂OH –{DMP}→ CH₃–CH₂–CH₂–CHO

Secondary Alcohol

A secondary alcohol is oxidized to a ketone:

R¹R²CH–OH –{DMP}→ R¹R²C=O

For example, propan-2-ol is oxidized to propanone:

CH₃CH(OH)CH₃ –{DMP}→ CH₃COCH₃

Another example is the conversion of cyclohexanol into cyclohexanone:

C₆H₁₁OH –{DMP}→ C₆H₁₀O

In each of these reactions, the carbon atom that originally bears the hydroxyl group becomes the carbonyl carbon. The carbon skeleton of the molecule is normally retained.

Tertiary Alcohol

A tertiary alcohol does not undergo normal Dess–Martin oxidation because the carbon bearing the hydroxyl group has no hydrogen attached to it. This hydrogen, described as the α-hydrogen in the mechanism below, is required for formation of the carbonyl group.

What Is Dess–Martin Periodinane

Dess–Martin periodinane, commonly abbreviated as DMP, is a hypervalent iodine(V) oxidizing reagent. The iodine atom has an oxidation state of +5 and acts as an electrophilic center during the reaction. ^[2–4,5,7]

The oxygen atom of the alcohol interacts with this iodine center, allowing the alcohol to become attached to the reagent. DMP is a stoichiometric reagent, meaning that it is consumed as the alcohol is oxidized.

Although DMP is used under relatively mild conditions, it is a reactive oxidizing agent and must be handled using appropriate laboratory safety procedures.

Mechanism of Dess–Martin Oxidation

A simplified mechanism can be represented in three main stages. Ligand exchange and removal of the O–H proton are shown separately here for clarity, although these processes may be closely associated. ^[1,2,5,7]

1. Ligand Exchange

The oxygen atom of the alcohol uses one of its lone pairs to attack the electrophilic iodine(V) center of DMP. One of the acetate groups attached to iodine is displaced, forming an intermediate in which the alcohol oxygen is bonded to iodine.

This intermediate is called an alkoxyiodinane intermediate.

2. Removal of the O–H Proton

An acetate ion acts as a base and removes the proton attached to the alcohol oxygen. This produces a neutral alkoxyiodinane intermediate and acetic acid.

This step removes the hydrogen from the O–H bond. It should not be confused with the removal of the hydrogen attached to carbon in the following step.

3. Acetate-Assisted Elimination

An acetate ion acts as a base and removes the α-hydrogen, i.e., the hydrogen attached to the same carbon that originally bore the hydroxyl group.

At the same time, the electrons from the C–H bond help form the C=O bond, and the bond between oxygen and iodine breaks. The aldehyde or ketone is released, while the iodine(V) center is reduced and iodine-containing byproducts are formed.

The bond-forming and bond-breaking changes occur together in an elimination step.

Advantages and Limitations

Compared with many chromium(VI)-based oxidation methods, including Jones oxidation and PCC oxidation, DMP avoids chromium-containing waste and is often suitable for compounds containing sensitive functional groups.^[1,3,4,6,7]

DMP often converts primary alcohols into aldehydes without oxidizing them further to carboxylic acids. It is also compatible with many functional groups that may be affected by strongly acidic or basic conditions.

However, the reaction produces acetic acid. A suitable base may therefore be added when the starting material is particularly sensitive to acidic conditions.

DMP is normally used in a stoichiometric amount, often in slight excess, and must be handled carefully because it is a reactive oxidizing reagent.