Toward the understanding of the mechanism and enantioselectivity of the Pauson–Khand reaction. Theoretical and experimental studies*

Semiempirical and density functional theory (DFT) calculations have been performed on the key steps of the commonly accepted mechanism of the Pauson–Khand reaction (PKR). In this context, the high reactivity of ynamine complexes in the cycloaddition process has been rationalized on the basis of an anomerically assisted dissociation of CO. Moreover, an explanation has been provided for the correlation between olefin strain and reactivity in the PKR. Inspired by these results, new selective syntheses of cyclopentanones and phenols based on PKR with cyclopropene have been developed. On the other hand, the theoretical analysis of phosphine-substituted dicobalt carbonyl complexes of alkynes has helped in the development of efficient chelating (P,N) and bridging (P,S) ligands for the stereochemical control of the reaction and in the understanding of their action modes.