Wittig rearrangement reaction: Mechanism

Wittig rearrangement reaction, 1,2-Wittig rearrangement reaction, 2,3-Wittig rearrangement reaction, mechanism, and application have been discussed here.

wittig rearrangement reaction

Wittig rearrangement reaction has been classified into two types; 1,2-Wittig rearrangement and 2,3-Wittig rearrangement. Let’s discuss them with the mechanism.

1,2-Wittig rearrangement reaction:

When ether is treated with a strong base like alkyl lithium, ether is converted into a secondary alkoxide or alcohol via a 1,2- carbon shift. This reaction is known as 1,2-Wittig rearrangement. Let’s see some examples.

wittig rearrangement reaction

The migration tendency of groups depends on the group’s ability to stabilize a radical. Therefore, the migratory aptitude of groups is given below:

Methyl>Primary alkyl> Secondary alkyl> Tertiary alkyl

Mechanism of 1,2-Witting rearrangement:

1,2-Witting rearrangement is supposed to proceed via a radical mechanism and it is a stepwise reaction that consists of the following steps:

Step 1: Deprotonation of ether to form a carbanion

wittig rearrangement reaction

Step 2: Homolytic cleavage of an alkoxy carbanion to radical radical anion pair.

wittig rearrangement reaction

Step 3: Recombination of radical pairs

wittig rearrangement reaction

Alternatively, an ionic mechanism has been proposed in which the heterolytic cleavage of alpha-alkoxy carbanion takes place to form a ketone and anion. Then, the nucleophilic addition of anion to the carbonyl group takes place.

wittig rearrangement reaction

2,3- Wittig rearrangement reaction:

The conversion of allyl ethers or benzylic ethers into alcohol via the 2,3-sigmatropic rearrangement when allyl ether is treated with a base is called 2,3-Wittig rearrangement.’

wittig rearrangement reaction
2 3 wittig rearrangement

Mechanism of 2,3-wittig rearrangement:

The mechanism of this type of rearrangement is shown below:

2 3 wittig rearrangement mechanism

application of wittig rearrangement

Wittig rearrangement is one of the important rearrangement reactions which is widely used in organic synthesis such as homoallylic alcohol derivatives.


  1. Wang, Z., Comprehensive Organic Name Reactions and Reagents, John Wiley & Sons, Inc.,2010
  2. J.J. Li, Name Reactions, 4th ed.,© Springer-Verlag Berlin Heidelberg 2009
  3. March, J., Advanced Organic Chemistry, Wiley Eastern Limited, 1986.
  4. Morrison, R. T., & Boyd, R. N., Organic chemistry, Allyn and Bacon, Inc. 1987

Please comment if you have any problems related to this topic. Thank you.

Read also:

  1. Hofmann Rearrangement
  2. wagner meerwein rearrangement
  3. Pinacol pinacolone rearrangement
  4. Favorskii rearrangement
  5. Cope rearrangement
  6. Claisen Rearrangement
  7. Beckmann Rearrangement

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