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The Claisen rearrangement is a powerful carbon–carbon bond-forming chemical reaction discovered by Rainer Ludwig Claisen. [1] The heating of an allyl vinyl ether will initiate a [3,3]-sigmatropic rearrangement to give a γ,δ-unsaturated carbonyl, driven by exergonically favored carbonyl CO bond formation Δ(Δ f H) = −327 kcal/mol (−1,370 kJ/mol).
Johnson–Claisen rearrangement [ edit ] The Johnson–Claisen rearrangement is the reaction of an allylic alcohol with an ortho ester containing a deprotonatable alpha carbon (e.g. triethyl orthoacetate ) to give a γ,δ-unsaturated ester .
It is the ethyl orthoester of acetic acid. It is a colorless oily liquid. Triethyl orthoacetate is used in organic synthesis for acetylation. [1] It is also used in the Johnson-Claisen rearrangement. [2]
[11] [12] [13] This rearrangement is a useful carbon-carbon bond-forming reaction. An example of Claisen rearrangement is the [3,3] rearrangement of an allyl vinyl ether, which upon heating yields a γ,δ-unsaturated carbonyl. The formation of a carbonyl group makes this reaction, unlike other sigmatropic rearrangements, inherently irreversible.
In organic chemistry, a rearrangement reaction is a broad class of organic reactions where the carbon skeleton of a molecule is rearranged to give a structural isomer of the original molecule. [1] Often a substituent moves from one atom to another atom in the same molecule, hence these reactions are usually intramolecular.
Modified Wittig–Claisen tandem reaction is a cascade reaction that combines the Wittig reaction and Claisen rearrangement together. The Wittig reaction generates the allyl vinyl ether intermediate that further participates in a Claisen rearrangement to generate the final γ,δ-unsaturated ketone or aldehyde product (Figure "Modified Wittig ...
The mechanism for this transformation is formally a Claisen rearrangement, supported by the kinetic and isotopic data reported by Knowles, et al. [7] Reaction catalyzed by chorismate mutase. E. coli and Yeast chorismate mutase have a limited sequence homology, but their active sites contain similar residues. The active site of the Yeast ...
In one study, seven-membered rings were constructed in a tandem 5-exo-dig addition reaction / Claisen rearrangement: [6] A 6-endo-dig pattern was observed in an allene - alkyne 1,2-addition / Nazarov cyclization tandem catalysed by a gold compound: [7] A 5-endo-dig ring closing reaction was part of a synthesis of (+)-Preussin: [8]