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Favorskii rearrangement
 
 
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The Favorskii rearrangement (not to be confused with the Favorskii reaction
Favorskii reaction

The Favorskii reaction , named for the Russian chemist Alexei Yevgrafovich Favorskii, is a special case of nucleophilic attack on a carbonyl group involving a terminal alkyne with carbon acid....
), named for the Russian chemist Alexei Yevgrafovich Favorskii
Alexei Yevgrafovich Favorskii

Alexey Yevgrafovich Favorsky, also spelled Favorskii, was a Soviet/Russian chemist....
, is most principally a rearrangement of cyclopropanone
Cyclopropanone

Cyclopropanone is an organic compound with molecular formula C3H4O consisting of a cyclopropane carbon framework with a ketone functional group....
s and a-halo ketones which leads to carboxylic acid
Carboxylic acid

Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the Chemical formula -COH, usually written -COOH or -CO2H....
 derivatives. In the case of cyclic a-halo ketones, the Favorski rearrangement constitutes a ring contraction. This rearrangement takes place in the presence of a base, sometimes hydroxide
Hydroxide

In chemistry, hydroxide is the name for the Diatomic molecule anion OH-, consisting of oxygen and hydrogen atoms, usually derived from the Dissociation of a base ....
, to yield a carboxylic acid but most of the time either an alkoxide
Alkoxide

An alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. They can be written as RO–, where R is the organic substituent....
 base or an amine
Amine

Amines are organic compounds and functional groups that contain a base nitrogen atom with a lone pair. Amines are derivative s of ammonia, wherein one or more hydrogen atoms are replaced by organic substituents such as alkyl and aryl groups....
 to yield an ester
Ester

An ester is an often Aroma compound organic chemistry or partially organic compound formed by the reaction between an acid and an alcohol or aromatic alcohol with the elimination of water....
 or an amide
Amide

In chemistry, an amide is one of three kinds of compounds:* the organic chemistry functional group characterized by a carbonyl group linked to a nitrogen atom , or a compound that contains this functional group ; or...
, respectively.






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The Favorskii rearrangement (not to be confused with the Favorskii reaction
Favorskii reaction

The Favorskii reaction , named for the Russian chemist Alexei Yevgrafovich Favorskii, is a special case of nucleophilic attack on a carbonyl group involving a terminal alkyne with carbon acid....
), named for the Russian chemist Alexei Yevgrafovich Favorskii
Alexei Yevgrafovich Favorskii

Alexey Yevgrafovich Favorsky, also spelled Favorskii, was a Soviet/Russian chemist....
, is most principally a rearrangement of cyclopropanone
Cyclopropanone

Cyclopropanone is an organic compound with molecular formula C3H4O consisting of a cyclopropane carbon framework with a ketone functional group....
s and a-halo ketones which leads to carboxylic acid
Carboxylic acid

Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the Chemical formula -COH, usually written -COOH or -CO2H....
 derivatives. In the case of cyclic a-halo ketones, the Favorski rearrangement constitutes a ring contraction. This rearrangement takes place in the presence of a base, sometimes hydroxide
Hydroxide

In chemistry, hydroxide is the name for the Diatomic molecule anion OH-, consisting of oxygen and hydrogen atoms, usually derived from the Dissociation of a base ....
, to yield a carboxylic acid but most of the time either an alkoxide
Alkoxide

An alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. They can be written as RO–, where R is the organic substituent....
 base or an amine
Amine

Amines are organic compounds and functional groups that contain a base nitrogen atom with a lone pair. Amines are derivative s of ammonia, wherein one or more hydrogen atoms are replaced by organic substituents such as alkyl and aryl groups....
 to yield an ester
Ester

An ester is an often Aroma compound organic chemistry or partially organic compound formed by the reaction between an acid and an alcohol or aromatic alcohol with the elimination of water....
 or an amide
Amide

In chemistry, an amide is one of three kinds of compounds:* the organic chemistry functional group characterized by a carbonyl group linked to a nitrogen atom , or a compound that contains this functional group ; or...
, respectively. a,a’-Dihaloketones eliminate HX under the reaction conditions to give a,ß-unsaturated carbonyl compounds .

In the case of cylic a-halo ketones, the rearrangement occurs as depicted below :

Favorskii Rearrangement Scheme

Reaction mechanism


The reaction mechanism
Reaction mechanism

In chemistry, a reaction mechanism is the step by step sequence of elementary reactions by which overall chemical change occurs .Although only the net chemical change is directly observation for most chemical reactions, experiments can often be designed that suggest the possible sequence of steps in a reaction mechanism....
 is thought to involve the formation of an enolate on the side of the ketone
Ketone

In organic chemistry, a ketone is a type of organic compound which contains a carbonyl group bonded to two other carbon atoms in the form:Neither of the substituents R1 and R2 may be equal to hydrogen ....
 away from the chlorine
Chlorine

Chlorine...
 atom. This enolate cyclizes to a cyclopropanone
Cyclopropanone

Cyclopropanone is an organic compound with molecular formula C3H4O consisting of a cyclopropane carbon framework with a ketone functional group....
 intermediate which is then attacked by the hydroxide nucleophile
Nucleophile

In chemistry, a nucleophile is a reagent that forms a chemical bond to its reaction partner by donating both bonding electrons. Because nucleophiles donate electrons, they are by definition Lewis bases ....
.

Usage of alkoxide
Alkoxide

An alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. They can be written as RO–, where R is the organic substituent....
 anions such as sodium methoxide, instead of sodium hydroxide, yields the ring-contracted ester
Ester

An ester is an often Aroma compound organic chemistry or partially organic compound formed by the reaction between an acid and an alcohol or aromatic alcohol with the elimination of water....
 product.

Wallach degradation

In the related Wallach degradation (Otto Wallach
Otto Wallach

Otto Wallach was a Germany chemist and Nobel laureate for work on alicyclic compounds....
, 1918) not one but two halogen atoms flank the ketone resulting in a new contracted ketone after oxidation and decarboxylation
Decarboxylation

Decarboxylation is any chemical reaction in which a carboxyl group is split off from a compound as carbon dioxide ....
 

Photo-Favorskii reaction

The reaction type also exists as a photochemical reaction
Photochemical reaction

A photochemical reaction is a chemical reaction which is induced by electromagnetic wave . Examples of photochemical organic reactions are electrocyclic reactions, photoisomerization and Norrish reactions....
. The photo-Favorskii reaction has been used in the photochemical unlocking of certain phosphate
Phosphate

A phosphate, an inorganic chemical, is a Salt of phosphoric acid. Inorganic phosphates are mining to obtain phosphorus for use in agriculture and industry....
s (for instance those of ATP
Adenosine triphosphate

This article is about the chemical used by cells as an energy carrier. For other uses, see ATP .Adenosine-5'-triphosphate is a multifunctional nucleotide, and plays an important role in cell biology as a coenzyme that is the "molecule unit of currency" of intracellular energy transfer....
) protected
Protecting group

A protecting group or protective group is introduced into a molecule by chemical modification of a functional group in order to obtain chemoselectivity in a subsequent chemical reaction....
 by so-called p-hydroxyphenacyl groups . The deprotection proceeds through a triplet diradical
Diradical

A diradical in organic chemistry is a molecule with two electrons occupying two degenerate molecular orbitals . They are known by their higher reactivities and shorter lifetimes....
 (3) and a dione
Diketone

A diketone is a molecule containing two ketone groups. The simpliest diketone is diacetyl, also known as 2,3-butanedione. Diacetyl, acetylacetone, and hexane-2,5-dione are examples of 1,2-, 1,3-, and 1,4-diketones, respectively....
 spiro
Spiro compound

A spiro compound is a bicyclic organic compound with rings connected through just one atom. The rings can be different in nature or identical. The connecting atom is also called the spiroatom, most often a quaternary carbon ....
  intermediate (4) although the latter has thus far eluded detection .


See also

  • A classic cubane
    Cubane

    Cubane is a synthetic hydrocarbon molecule that consists of eight carbon atoms arranged at the corners of a Cube , with one hydrogen atom attached to each carbon atom....
     synthesis contains two Favorskii rearrangements.