The Claisen rearrangement (not to be confused with the Claisen condensation) is a powerful carbon-carbon bond-forming chemical reaction discovered by Rainer Ludwig Claisen. The heating of an allyl vinyl ether will initiate a -sigmatropic rearrangement to give a γ,δ-unsaturated carbonyl.
Discovered in 1912, the Claisen rearrangement is the first recorded example of a -sigmatropic rearrangement.
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Read more about Claisen Rearrangement: Mechanism, Claisen Rearrangement in Nature