Chemistry

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Claisen rearrangement

The Claisen rearrangement, named after Ludwig Claisen, is a pericyclic rearrangement, the course of which is analogous to that of the Cope rearrangement.

It proceeds through a six-membered transition state with two π bonds and one σ bond. The Claisen rearrangement is also referred to as the Oxa-Cope rearrangement and is assigned to the sigmatropic reactions in which a σ-bond, which is adjacent to one or more π-electron systems, migrates to a new position in a [3,3] -shift.

An allyl vinyl ether reacts in this way to form a γ, δ-unsaturated carbonyl compound. Since allyl phenyl ethers also convert accordingly, a distinction is made between the aliphatic and the aromatic Claisen rearrangement.

Both the aliphatic and the aromatic Claisen rearrangement are in many cases thermal isomerizations, temperatures> 100 ° C make necessary. By using Lewis acid catalysts, in particular transition metal complexes, these reactions can be carried out under mild conditions.


Video: STD 11 Chemistry - Hybridization in organic compounds (January 2022).