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The dienone–phenol rearrangement is a
reaction Reaction may refer to a process or to a response to an action, event, or exposure: Physics and chemistry *Chemical reaction * Nuclear reaction *Reaction (physics), as defined by Newton's third law * Chain reaction (disambiguation). Biology and ...
in organic chemistry first reported in 1921 by
Karl von Auwers Karl Friedrich von Auwers (September 16, 1863 – May 3, 1939) was a German chemist, and was the academic adviser of both Karl Ziegler and Georg Wittig at the University of Marburg. Life Karl Friedrich von Auwers was born the son of the renowned ...
and
Karl Ziegler Karl Waldemar Ziegler (26 November 1898 – 12 August 1973) was a German chemist who won the Nobel Prize in Chemistry in 1963, with Giulio Natta, for work on polymers. The Nobel Committee recognized his "excellent work on organometallic compound ...
. A common example of dienone–phenol rearrangement is 4,4-disubstituted converting into a stable 3,4-disubstituted phenol in presence of
acid In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequ ...
. A similar rearrangement is possible with a 2,2-disubstituted cyclohexadienone to its corresponding disubstituted phenol. Usually this type of rearrangement is spontaneous unless a dichloromethyl group is present at the 4th position or the process is otherwise blocked.


Reaction mechanism

The reaction mechanism of 4,4-disubstituted cyclohexadienones to 3,4-disubstituted phenol is illustrated here. : The migration tendency for the two different groups (R) present at either 4,4 position or 2,2 position can be determined by comparing the relative stability of the intermediate
carbocation A carbocation is an ion with a positively charged carbon atom. Among the simplest examples are the methenium , methanium and vinyl cations. Occasionally, carbocations that bear more than one positively charged carbon atom are also encounte ...
formed during rearrangement. In case of acid-promoted conditions, some relative migration tendencies are: COOEt >
phenyl In organic chemistry, the phenyl group, or phenyl ring, is a cyclic group of atoms with the formula C6 H5, and is often represented by the symbol Ph. Phenyl group is closely related to benzene and can be viewed as a benzene ring, minus a hydroge ...
(or
alkyl In organic chemistry, an alkyl group is an alkane missing one hydrogen. The term ''alkyl'' is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of . A cycloalkyl is derived from a cycloal ...
); phenyl >
methyl In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in man ...
;
vinyl Vinyl may refer to: Chemistry * Polyvinyl chloride (PVC), a particular vinyl polymer * Vinyl cation, a type of carbocation * Vinyl group, a broad class of organic molecules in chemistry * Vinyl polymer, a group of polymers derived from vinyl m ...
> methyl; methyl >
alkoxy In chemistry, the alkoxy group is an alkyl group which is singularly bonded to oxygen; thus . The range of alkoxy groups is vast, the simplest being methoxy (). An ethoxy group () is found in the organic compound ethyl phenyl ether (, also k ...
and alkoxy > phenyl. In some cases such as
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, . ...
and
benzyl In organic chemistry, benzyl is the substituent or molecular fragment possessing the structure . Benzyl features a benzene ring () attached to a methylene group () group. Nomenclature In IUPAC nomenclature, the prefix benzyl refers to a substi ...
group, the actual rearrangement might happen through the
Cope rearrangement The Cope rearrangement is an extensively studied organic reaction involving the ,3sigmatropic rearrangement of 1,5-dienes. It was developed by Arthur C. Cope and Elizabeth Hardy. For example, 3-methyl-hexa-1,5-diene heated to 300 °C yields ...
. Apart from acid catalysis, the dienone–phenol rearrangement is also possible in presence of base. The dienone–phenol rearrangement has been used in the synthesis of
steroid A steroid is a biologically active organic compound with four rings arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes that alter membrane fluidity; and ...
s,
anthracene Anthracene is a solid polycyclic aromatic hydrocarbon (PAH) of formula C14H10, consisting of three fused benzene rings. It is a component of coal tar. Anthracene is used in the production of the red dye alizarin and other dyes. Anthracene is co ...
s, and phenanthrenes.


References

{{DEFAULTSORT:Dienone-phenol rearrangement Chemical reactions Organic reactions