Claisen rearrangement

Schematic of the Claisen rearrangement. Reagents: allyl vinyl ether, allyl phenyl ether, heat, Lewis acid. Product: γ,δ-unsaturated carbonyl, o-allylphenol, p-allylphenol. Comments: Concerted [3,3]-sigmatropic rearrangement.

The Claisen rearrangement is an organic reaction where an allyl vinyl ether is converted into a γ,δ-unsaturated carbonyl compound with the input of heat or a Lewis acid. This reaction belongs to a class of reactions termed "sigmatropic rearrangements" and it is a concerted process where bonds are forming and breaking at the same time. When substituents are present in the allyl vinyl ether starting material, the stereochemistry of this reaction can be predicted by drawing the molecule in a chair-like conformation and placing the substituents in the equatorial position to minimize the steric interactions.[1][2]


Mechanism of the Claisen rearrangement. Note: For substituted compound the product can be predicted by a chairlike transition state which has the least steric interactions. Favoured R group equatorial; Not favoured R group axial. In this example both reagents lead to the same product as different conformations are prefered. Mechanism for the allyl phenyl ether reagents follows the steps: Claisen [3,3], re-aromatization, Cope [3,3], and re-aromatization.


Claisen, L. Ber. Dtsch. Chem. Ges. 1912, 45, 3157–3166.
Claisen, L.; Eisleb, O. Justus Liebigs Ann. Chem. 1913, 401, 21–119.