The Carroll rearrangement is a

rearrangement reaction 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. Often a substituent moves from one atom to another ...

organic chemistry Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, J.; ...

and involves the transformation of a β- keto

allyl In organic chemistry, an allyl group is a substituent with the structural formula , where R is the rest of the molecule. It consists of a methylene bridge () attached to a vinyl group (). The name is derived from the scientific name for garlic, ...

ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ar ...

into a α-allyl-β-ketocarboxylic acid. This

organic reaction Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, Mechanistic Organ ...

is accompanied by

decarboxylation Decarboxylation is a chemical reaction that removes a carboxyl group and releases carbon dioxide (CO2). Usually, decarboxylation refers to a reaction of carboxylic acids, removing a carbon atom from a carbon chain. The reverse process, which is t ...

and the final product is a γ,δ-allylketone. The Carroll rearrangement is an adaptation of the

Claisen rearrangement The Claisen rearrangement is a powerful carbon–carbon bond-forming chemical reaction discovered by Rainer Ludwig Claisen. The heating of an allyl vinyl ether will initiate a ,3sigmatropic rearrangement to give a γ,δ-unsaturated carbonyl, d ...

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 In organic chemistry, alkenols (shortened to enols) are a type of reactive structure or intermediate in organic chemistry that is represented as an alkene ( olefin) with a hydroxyl group attached to one end of the alkene double bond (). The te ...

which then rearranges in an electrocyclic Claisen rearrangement. The follow-up is a decarboxylation. With

palladium Palladium is a chemical element with the symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal discovered in 1803 by the English chemist William Hyde Wollaston. He named it after the asteroid Pallas, which was itself na ...

(0) as a

catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

, the reaction (Tsuji, 1980) is much milder (path B) with an intermediate allyl cation / carboxylic acid anion

organometallic Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...

complex.

Decarboxylation precedes allylation as evidenced by this reaction catalyzed by

tetrakis(triphenylphosphine)palladium(0) Tetrakis(triphenylphosphine)palladium(0) (sometimes called quatrotriphenylphosphine palladium) is the chemical compound d(P(C6H5)3)4 often abbreviated Pd( PPh3)4, or rarely PdP4. It is a bright yellow crystalline solid that becomes brown upon de ...

Asymmetric decarboxylative allylation

By introducing suitable chiral ligands, the reaction becomes

enantioselective In chemistry, an enantiomer ( /ɪˈnænti.əmər, ɛ-, -oʊ-/ ''ih-NAN-tee-ə-mər''; from Ancient Greek ἐνάντιος ''(enántios)'' 'opposite', and μέρος ''(méros)'' 'part') – also called optical isomer, antipode, or optical anti ...

. The first reported asymmetric rearrangement is catalyzed by

tris(dibenzylideneacetone)dipalladium(0) Tris(dibenzylideneacetone)dipalladium(0) or d2(dba)3is an organopalladium compound. The compound is a complex of palladium(0) with dibenzylideneacetone (dba). It is a dark-purple/brown solid, which is modestly soluble in organic solvents. Becau ...

and the

Trost ligand The Trost ligand is a diphosphine used in the palladium- catalyzed Trost asymmetric allylic alkylation. Other C2-symmetric ligands derived from ''trans''-1,2-diaminocyclohexane (DACH) have been developed, such as the (''R'',''R'')-DACH- naphthy ...

:''Asymmetric Allylic Alkylation of Ketone Enolates: An Asymmetric Claisen Surrogate'' Erin C. Burger and Jon A. Tunge Org. Lett.; 2004; 6(22) pp 4113 - 4115; (Letter) AsymmetricCarrol2005

A similar reaction uses additional

naphthol Naphthol may refer to: * 1-Naphthol * 2-Naphthol {{Short pages monitor