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Carroll rearrangement
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.〔Carroll, 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. .〕 This organic reaction is accompanied by decarboxylation and the final product is a γ,δ-allylketone. The Carroll rearrangement is an adaptation of the Claisen rearrangement and effectively a decarboxylative Allylation.
== Reaction mechanism ==
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 an electrocyclic Claisen rearrangement. The follow-up is a decarboxylation. With palladium(0) as a catalyst, the reaction (Tsuji, 1980) is much milder (path B) with an intermediate allyl cation / carboxylic acid anion organometallic complex.〔''Palladium-catalyzed rearrangement of allylic esters of acetoacetic acid to give γ,δ-unsaturated methyl ketones'' Tetrahedron Letters, Volume 21, Issue 33, 1980, Pages 3199-3202 Isao Shimizu, Toshiro Yamada and Jiro Tsuji 〕
Decarboxylation precedes allylation as evidenced by this reaction catalyzed by tetrakis(triphenylphosphine)palladium(0):〔
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