Uses
2-Cyclopenten-1-one is a versatile electrophile employed in various addition reactions including conjugate addition of organocopper nucleophiles, Michael reaction with silyl enol ethers and siloxanes. It is also used in Diels-Alder cycloadditions and phosphoniosilylations.
Preparation
2-Cyclopentenones can be synthesized in a number of ways. One of the routes involves elimination of α-bromo-cyclopentanone using lithium carbonate and Claisen condensation-decarboxylation-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 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.
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