The Claisen rearrangement is a [3,3] sigmatropic rearrangement of allyl vinyl ethers to unsaturated carbonyl compounds. The rearrangement is a concerted pericyclic reaction proceeding via a chair-like transition state.

An aromatic Claisen rearrangement involves the conversion of allyl aryl ethers to an unstable ketone intermediate, which tautomerizes to give ortho-substituted phenols.

However, ortho-substituted allyl aryl ethers exclusively yield para-substituted phenols via two sequential Clasien rearrangements.