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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).
[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.
For instance, aluminum catalysts based on bulky 3,3'-disilyl substituted BINOL have been developed as early examples of catalytic asymmetric hetero-Diels-Alder reaction [60] and Claisen rearrangement, [61] while introduction of electron-withdrawing groups at the 6,6'-positions was crucial for increasing the Lewis acidity, and hence catalytic ...
The Carroll rearrangement is an adaptation of the Claisen rearrangement and effectively a decarboxylative allylation. The Carroll rearrangement (1940) in the presence of base and with high reaction temperature (path A) takes place through an intermediate enol which then rearranges in a sigmatropic Claisen rearrangement. The follow-up is a ...
The Ireland–Claisen rearrangement is a type of Claisen rearrangement. The mechanism is therefore a concerted [3,3]-sigmatropic rearrangement which according to the Woodward–Hoffmann rules show a concerted, suprafacial, pericyclic reaction pathway.
In the case of the modified benzannulation reaction (Scheme 5); irradiation of the diazoketones induces the Wolff rearrangement yielding the vinyl ketene intermediate which reacts with the acetylene in a [2+2] cycloaddition then a four-electron cleavage of the resulting 4-substituted cyclobutenone produces a dienylketene which then undergoes a ...
The asymmetric version of this reaction has been performed by utilizing chiral thiazolium and triazolium salts. Triazolium salts were found to give greater enantiomeric excess than thiazolium salts. [8] An example is shown below. [9] Scheme 2. An intramolecular benzoin addition