Organic reaction
Claisen Rearrangement[edit]
The Claisen rearrangement is a fundamental organic reaction that involves the [3,3]-sigmatropic rearrangement of an allyl vinyl ether to produce a _,_-unsaturated carbonyl compound. This reaction is named after the German chemist Ludwig Claisen, who first reported it in 1912.
Mechanism[edit]
The Claisen rearrangement is a concerted process, meaning that it occurs in a single step without the formation of intermediates. The reaction proceeds through a six-membered cyclic transition state, which is a hallmark of pericyclic reactions. The driving force for the rearrangement is the formation of a more stable carbonyl compound from the less stable allyl vinyl ether.
Variants[edit]
Several variants of the Claisen rearrangement exist, including:
- The Johnson–Claisen rearrangement, which involves the use of an orthoester to generate the allyl vinyl ether in situ.
- The Ireland–Claisen rearrangement, which uses a silyl ketene acetal as the starting material and is performed under basic conditions.
- The Eschenmoser–Claisen rearrangement, which involves the rearrangement of allylic amines.
Applications[edit]
The Claisen rearrangement is widely used in organic synthesis to form carbon-carbon bonds and to introduce functional groups into molecules. It is particularly useful in the synthesis of natural products and complex organic molecules.
