Cyclopentenone is a hydrocarbon

Hydrocarbon

In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....

 with chemical formula

Chemical formula

A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 ₅₆ and CAS number 930-30-3. It is structurally similar to cyclopentanone

Cyclopentanone

Cyclopentanone is a colorless liquid organic compound with a peppermint-like odor. It is a cyclic ketone, structurally similar to cyclopentane, consisting of a five-membered ring containing a ketone functional group.-Safety:...

, with the additional feature of α-β unsaturation

Enone

An enone is an unsaturated chemical compound or functional group consisting of a conjugated system of an alkene and a ketone. The simplest enone is methyl vinyl ketone or CH2=CHCOCH3....

 in the ring system. Cyclopentenone belongs to the cycloalkene

Cycloalkene

A cycloalkene or cycloolefin is a type of alkene hydrocarbon which contains a closed ring of carbon atoms, but has no aromatic character. Some cycloalkenes, such as cyclobutene and cyclopentene, can be used as monomers to produce polymer chains. Unless the rings are very large, cycloalkenes are...

 (alkene

Alkene

In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond...

s which have one or more rings of carbon atoms

Carbon ring

Carbon rings are rings of carbon atoms. Rings of five and six carbons are by far the most common, as they allow bond angles close to the ideal angle of 109.5°. Rings of three and four are possible, but with bond angles of 60° and 90°, they have a larger ring strain and are unstable...

) class of compounds and is also a ketone

Ketone

In organic chemistry, a ketone is an organic compound with the structure RCR', where R and R' can be a variety of atoms and groups of atoms. It features a carbonyl group bonded to two other carbon atoms. Many ketones are known and many are of great importance in industry and in biology...

 (it possesses a carbonyl

Carbonyl

In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups....

 functional group). It is a liquid at room temperature with a boiling point of 150 °C. It has been isolated from pressure-cooked pork liver

Liver

The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...

 by simultaneous steam distillation

Distillation

Distillation is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction....

 and continuous solvent extraction

Liquid-liquid extraction

Liquid–liquid extraction, also known as solvent extraction and partitioning, is a method to separate compounds based on their relative solubilities in two different immiscible liquids, usually water and an organic solvent. It is an extraction of a substance from one liquid phase into another liquid...

.

The term cyclopentenone may also refer to a structural motif

Structural motif

In a chain-like biological molecule, such as a protein or nucleic acid, a structural motif is a supersecondary structure, which appears also in a variety of other molecules...

 wherein the cyclopentenone moiety is a subsection of a larger molecule. In this regard, cyclopentenones are found in a large number of natural product

Natural product

A natural product is a chemical compound or substance produced by a living organism - found in nature that usually has a pharmacological or biological activity for use in pharmaceutical drug discovery and drug design...

s, including jasmone

Jasmone

Jasmone is a natural organic compound extracted from the volatile portion of the oil from jasmine flowers. It is a colorless to pale yellow liquid that has the odor of jasmine. Jasmone can exist in two isomeric forms with differing geometry around the pentenyl double bond, cis-jasmone and...

, the aflatoxin

Aflatoxin

Aflatoxins are naturally occurring mycotoxins that are produced by many species of Aspergillus, a fungus, the most notable ones being Aspergillus flavus and Aspergillus parasiticus. Aflatoxins are toxic and among the most carcinogenic substances known...

s, and several prostaglandin

Prostaglandin

A prostaglandin is any member of a group of lipid compounds that are derived enzymatically from fatty acids and have important functions in the animal body. Every prostaglandin contains 20 carbon atoms, including a 5-carbon ring....

s.

Synthesis

Cyclopentenones can be synthesized in a number of ways. Industrially, the most common procedures are elimination of α-bromo-cyclopentanone

Cyclopentanone

Cyclopentanone is a colorless liquid organic compound with a peppermint-like odor. It is a cyclic ketone, structurally similar to cyclopentane, consisting of a five-membered ring containing a ketone functional group.-Safety:...

 using lithium carbonate

Lithium carbonate

Lithium carbonate is a chemical compound of lithium, carbon, and oxygen with the formula Li2CO3. This colorless salt is widely used in the processing of metal oxides and has received attention for its use in psychiatry. It is found in nature as the rare mineral zabuyelite.-Properties:Like almost...

 and Claisen condensation

Claisen condensation

The Claisen condensation is a carbon–carbon bond forming reaction that occurs between two esters or one ester and another carbonyl compound in the presence of a strong base, resulting in a β-keto ester or a β-diketone...

-decarboxylation

Decarboxylation

Decarboxylation is a chemical reaction that releases carbon dioxide . Usually, decarboxylation refers to a reaction of carboxylic acids, removing a carbon atom from a carbon chain. The reverse process, which is the first chemical step in photosynthesis, is called carbonation, the addition of CO2 to...

-isomerization cascades of unsaturated diesters as shown below.
As a functional group, the synthesis of cyclopentenones is accomplished in a variety of other ways, including the Nazarov cyclization reaction

Nazarov cyclization reaction

The Nazarov cyclization reaction is a chemical reaction used in organic chemistry for the synthesis of cyclopentenones. The reaction is typically divided into classical and modern variants, depending on the reagents and substrates employed...

 from divinyl ketones, Saegusa–Ito oxidation from cyclopentanone

Cyclopentanone

Cyclopentanone is a colorless liquid organic compound with a peppermint-like odor. It is a cyclic ketone, structurally similar to cyclopentane, consisting of a five-membered ring containing a ketone functional group.-Safety:...

s, ring-closing metathesis

Ring-closing metathesis

Ring-closing metathesis or RCM is a variation on olefin metathesis that allows the closing of previously hard to make rings...

 from the corresponding diene

Diene

In organic chemistry a diene or diolefin is a hydrocarbon that contains two carbon double bonds.Conjugated dienes are functional groups, with a general formula of CnH2n-2. Dienes and alkynes are functional isomers...

s, oxidation of the corresponding cyclic allylic alcohols, and the Pauson–Khand reaction

Pauson–Khand reaction

The Pauson–Khand reaction is a chemical reaction described as a [2+2+1] cycloaddition between an alkyne, an alkene and carbon monoxide to form a α,β-cyclopentenone...

 from alkene

Alkene

In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond...

s, alkyne

Alkyne

Alkynes are hydrocarbons that have a triple bond between two carbon atoms, with the formula CnH2n-2. Alkynes are traditionally known as acetylenes, although the name acetylene also refers specifically to C2H2, known formally as ethyne using IUPAC nomenclature...

s, and carbon monoxide

Carbon monoxide

Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...

.

Reactions

As an enone

Enone

An enone is an unsaturated chemical compound or functional group consisting of a conjugated system of an alkene and a ketone. The simplest enone is methyl vinyl ketone or CH2=CHCOCH3....

, cyclopentenone undergoes the typical reactions of α-β unsaturated ketones, including nucleophilic conjugate addition

Nucleophilic 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 polarity, unless the alkene is activated with special...

, the Baylis–Hillman reaction

Baylis–Hillman reaction

The Baylis–Hillman reaction is an organic reaction of an aldehyde and an α,β-unsaturated electron-withdrawing group catalyzed by DABCO to give an allylic alcohol. This reaction is also known as the Morita–Baylis–Hillman reaction or MBH reaction. It is named for the Japanese chemist Ken-ichi...

, and the Michael reaction

Michael reaction

The Michael reaction or Michael addition is the nucleophilic addition of a carbanion or another nucleophile to an alpha, beta unsaturated carbonyl compound. It belongs to the larger class of conjugate additions. This is one of the most useful methods for the mild formation of C-C bonds...

. Cyclopentenone also functions as an excellent dienophile in the Diels–Alder reaction, reacting with a wide variety of diene

Diene

In organic chemistry a diene or diolefin is a hydrocarbon that contains two carbon double bonds.Conjugated dienes are functional groups, with a general formula of CnH2n-2. Dienes and alkynes are functional isomers...

s. 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.