Cyclopentenone

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Cyclopentenone
IUPAC name

2-Cyclopenten-1-one

Identifiers
CAS number 930-30-3 YesY
PubChem 13588
ChemSpider 12999 YesY
ChEMBL CHEMBL52190 YesY
Jmol-3D images Image 1
Properties
Molecular formula C5H6O
Molar mass 82.04 g·mol−1
Density 0.98 g·mL−1
Boiling point 150 °C
Solubility in water almost insoluble in water
Hazards
Main hazards Harmful
Flash point 42 °C; 108 °F; 315 K
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

2-Cyclopentenone is a hydrocarbon with chemical formula C5H6O 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 belongs to the cycloalkene (alkenes which have one or more rings of carbon atoms) class of compounds and is also a ketone (it possesses a carbonyl 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 by simultaneous steam distillation and continuous solvent extraction.[1]

The term cyclopentenone may also refer to a structural motif wherein the cyclopentenone moiety is a subsection of a larger molecule. In this regard, cyclopentenones are found in a large number of natural products, including jasmone, the aflatoxins, and several prostaglandins.

Synthesis

2-Cyclopentenones can be synthesized in a number of ways. Industrially, the most common procedures are elimination of α-bromo-cyclopentanone using lithium carbonate[2] and Claisen condensation-decarboxylation-isomerization cascades of unsaturated diesters as shown below.[3]

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 from cyclopentanones, ring-closing metathesis from the corresponding dienes, oxidation of the corresponding cyclic allylic alcohols, and the Pauson–Khand reaction from alkenes, alkynes, and carbon monoxide.[4]

Reactions

As an enone, 2-cyclopentenone undergoes the typical reactions of α-β unsaturated ketones, including nucleophilic conjugate addition, the Baylis–Hillman reaction, and the Michael reaction. Cyclopentenone also functions as an excellent dienophile in the Diels–Alder reaction, 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.[5]

References

  1. ↑ Mussinan,C.J.; Walradt, J.P. (1974), J. Agric. Food Chem. 22 (5): 827–831, doi:10.1021/jf60195a002 
  2. ↑ US EP1418166, Daisuke, Fukushima & Hirata Norihiko, "Process for producing 2-bromocyclopentanone", published 2004-05-12 
  3. ↑ US EP1422212, Liang, Shelue; Andrea Haunert & Sylvia Huber-Dirr et al., "Process for preparing cyclopentenone", published 2004-11-25 
  4. ↑ Organic Reactions Portal "Cyclopentenone synthesis"
  5. ↑ Danishefsky, S.; Zamboni, R.; Kahn, M.; Etheredge, S.J. (1980), J. Am. Chem. Soc. 102 (6): 2097–2098, doi:10.1021/ja00526a061 
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