Carroll rearrangement
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The Carroll rearrangement is a rearrangement reaction in organic chemistry and involves the transformation of a β-keto allyl ester into a α-allyl-β-ketocarboxylic acid.[1] This organic reaction is accompanied by decarboxylation and the final product is a γ,δ-allylketone. The Carrol rearrangement is an adaptation of the Claisen rearrangement.
[edit] Reaction mechanism
The Carrol rearrangement in the presence of base and with high reaction temperature (path A) takes place through an intermediate enol which then rearranges in an electrocyclic Claisen rearrangement. The follow up is a decarboxylation. With palladium(0) as a catalyst, the reaction is much milder (path B) with an intermediate allyl cation / carboxylic acid anion organometallic complex.
[edit] Asymmetric Carrol rearrangement
One asymmetric Carrol rearrangement is reported[2] catalyzed by tris(dibenzylideneacetone)dipalladium(0), the Trost ligand and naphthol.
This reaction delivers one enantiomer with 88% ee. It remains to be seen if this reaction will have a wide scope because the acetamido group is a prerequisite.
[edit] References
- ^ Carrol, M. F. "131. Addition of α,β-unsaturated alcohols to the active methylene group. Part I. The action of ethyl acetoacetate on linalool and geraniol". J. Chem. Soc. 1940, 704–706. DOI:10.1039/JR9400000704.
- ^ Kuwano, R.; Ishida N.; Murakami, M. "Asymmetric Carroll rearrangement of allyl α-acetamido-β-ketocarboxylates catalysed by a chiral palladium complex". Chem. Commun. 2005, (31), 3951–3952. DOI:10.1039/b505105c.
