Pauson-Khand reaction

Also known as: Pauson-Khand cycloaddition

Schematic of the Pauson-Khand cycloaddition. Reagents: terminal or internal alkyne, alkene, CO, and Cobalt catalyst. Products: α,β-cyclopentenone.

The Pauson-Khand reaction is an organic reaction used to convert an alkyne and alkene to a substituted cyclopentenone under an atmosphere of carbon monoxide and a dicobalt complex catalyst. This 2+2+1 cycloaddition reaction begins with the addition of the alkyne to the metal complex followed by ligand substitution of the alkene to expel a CO molecule. Alkene insertion follows and a subsequent CO insertion results in the formation of a carbonyl group. A series of reductive eliminations then yield the final cyclopentenone product and regenerates the cobalt catalyst.[1][2][3]


Mechanism of the Pauson-Khand cycloaddition.The catalytic cycle includes ligand substitution, alkene insertion, CO insertion, reductive elimination, and oxidative addition.


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Yamanaka, M.; Nakamura, E. J. Am. Chem. Soc. 2001, 123, 1703–1708.
Magnus, P.; Principe, L. M. Tetrahedron Letters 1985, 26, 4851–4854.

Other Cycloaddition Reactions: