Meerwein–Ponndorf–Verley Reduction
Table of Contents
The Meerwein–Ponndorf–Verley (MPV) reduction is an organic reaction used to reduce aldehydes and ketones to alcohols. Aldehydes form primary alcohols, while ketones form secondary alcohols. [1–4]
General Reaction
The overall reaction can be represented as: [2]
R1R2C=O + (CH3)2CHOH ⇌ R1R2CHOH + (CH3)2CO
Where
R1R2C=O: a ketone, or an aldehyde when R2 = H
(CH3)2CHOH: 2-propanol
In this reaction:
- the aldehyde or ketone is reduced to an alcohol;
- 2-propanol is oxidized to acetone.
Examples
Mechanism
The Meerwein–Ponndorf–Verley reduction is commonly carried out using aluminum isopropoxide (Al(OiPr)3) in 2-propanol. [3,4]
Step 1: Coordination of the Carbonyl Group
The oxygen atom of the aldehyde or ketone coordinates to the aluminum center. This positions the carbonyl compound correctly for hydride transfer.
Step 2: Hydride Transfer
The carbonyl compound and an aluminum-bound isopropoxide group form a six-membered cyclic transition state.
Within this arrangement, a hydride is transferred from the carbon atom of the isopropoxide group to the carbonyl carbon. At the same time, the carbonyl compound is reduced, and the isopropoxide group is converted into acetone.
The hydride is transferred directly within the cyclic transition state; a free hydride ion, H⁻, is not formed.
Step 3: Alcohol Release and Catalyst Regeneration
The reduced carbonyl compound is initially present as an alkoxide attached to the aluminum center. Reaction with 2-propanol converts this alkoxide into the corresponding alcohol and regenerates aluminum isopropoxide.
