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2-Cyclopentenone is a
The acid-catalyzed dehydration of cyclopentanediols affords cyclopentenone.
As a functional group, the synthesis of 2-cyclopentenones is accomplished in a variety of other ways, including the Nazarov cyclization reaction from divinyl ketones,
ketone
In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bo ...
with chemical formula and CAS number 930-30-3. It is structurally similar to cyclopentanone, with the additional feature of α-β unsaturation in the ring system. 2-Cyclopentenone contains two functional groups, a ketone and an alkene. It is a colorless liquid.
The term cyclopentenone may also refer to a structural motif
In a polymer, chain-like biological molecule, such as a protein or nucleic acid, a structural motif is a common Biomolecular structure#Tertiary structure, three-dimensional structure that appears in a variety of different, evolutionarily unrel ...
wherein the cyclopentenone moiety
Moiety may refer to:
Chemistry
* Moiety (chemistry), a part or functional group of a molecule
** Moiety conservation, conservation of a subgroup in a chemical species
Anthropology
* Moiety (kinship), either of two groups into which a society is ...
is a subunit of a larger molecule. Cyclopentenones are found in a large number of natural product
A natural product is a natural compound or substance produced by a living organism—that is, found in nature. In the broadest sense, natural products include any substance produced by life. Natural products can also be prepared by chemical syn ...
s, including jasmone
Jasmone is an organic compound, which is a volatile portion of the oil from jasmine flowers. It is a colorless to pale yellow liquid. Jasmone can exist in two isomeric forms with differing geometry around the pentenyl double bond, ''cis''-jasmon ...
, the aflatoxins, and several prostaglandin
The prostaglandins (PG) are a group of physiologically active lipid compounds called eicosanoids having diverse hormone-like effects in animals. Prostaglandins have been found in almost every tissue in humans and other animals. They are derive ...
s.
Synthesis
2-Cyclopentenones can be synthesized in a number of ways. One of the routes involves elimination of α- bromo- cyclopentanone usinglithium carbonate
Lithium carbonate is an inorganic compound, the lithium salt (chemistry), salt of carbonate with the chemical formula, formula . This white Salt (chemistry), salt is widely used in the processing of metal oxides. It is listed on the World Health O ...
and Claisen condensation-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 ...
- isomerization cascades of unsaturated diesters as shown below.
The acid-catalyzed dehydration of cyclopentanediols affords cyclopentenone.
As a functional group, the synthesis of 2-cyclopentenones is accomplished in a variety of other ways, including the Nazarov cyclization reaction from divinyl ketones, Saegusa–Ito oxidation
The Saegusa–Ito oxidation is a chemical reaction used in organic chemistry. It was discovered in 1978 by Takeo Saegusa and Yoshihiko Ito as a method to introduce α-β unsaturation in carbonyl compounds. The reaction as originally reported ...
from cyclopentanones, ring-closing metathesis from the corresponding dienes, oxidation of the corresponding cyclic allylic alcohols, and the Pauson–Khand reaction from alkenes, alkyne
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Acetylene
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Propyne
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1-Butyne
In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and n ...
s, and carbon monoxide.
Reactions
As an enone, 2-cyclopentenone undergoes the typical reactions of α-β unsaturated ketones, includingnucleophilic conjugate addition
Nucleophilic conjugate addition is a type of organic reaction. Ordinary nucleophilic additions or 1,2-nucleophilic additions deal mostly with additions to carbonyl compounds. Simple alkene compounds do not show 1,2 reactivity due to lack of polarit ...
, the Baylis–Hillman reaction, and the Michael reaction. Cyclopentenone also functions as an excellent dienophile in the Diels–Alder reaction
In organic chemistry, the Diels–Alder reaction is a chemical reaction between a conjugated diene and a substituted alkene, commonly termed the dienophile, to form a substituted cyclohexene derivative. It is the prototypical example of a peric ...
, reacting with a wide variety of dienes. In one example, a Danishefsky-type diene is reacted with a cyclopentenone to yield a fused tricyclic system en route to the synthesis of coriolin.
Occurrence
It has been isolated from pressure-cooked pork liver by simultaneous steam distillation and continuous solvent extraction.References
{{reflist Enones Cyclopentenes