Regiochemistry Pauson-Khand reaction

Robert, F., Milet, A., Gimbert, Y., Konya, D., Greene, A. E. Regiochemistry in the Pauson-Khand Reaction Has a Trans Effect Been... 

Schulte, J. H., Gleiter, R., Rominger, F. Regiochemistry of S-Alkyl-Substituted Alkynes in Pauson-Khand Reactions. Is a Correlation with X-ray Data and Charge Distribution Calculations of the Co2(CO)6-Alkyne Complexes Possible Org. Lett. 2002,4, 3301-3304. 

Similarly to the situation shown for cyclic systems above [Eq. (45)], the presence of substituents capable of acting as ligands to cobalt on an acyclic olefln may be highly beneficial. The reaction shown in Eq. (49) is merely one of a large number of examples that ecplore the effects of the position, nature, and number of heteroatoms on the alkene reaction partner on the yield and regiochemistry of both the intermolecular and intramolecular Pauson-Khand reactions [93, 105, 111]. 

Most Pauson-Khand reactions have been conducted with an alkene, an alk5me, and CO. However, PKRs have been developed with aUenynes (Scheme 17.36). Narasaka reported the first example of an intramolecular allenyne PKR catalyzed by an iron complex, and Brum-mond has extensively studied the allenic Pauson-Khand reaction. These reactions have been catalyzed by the combination of Mo(CO) and DMSO or by [Rh(CO)2Cl]2, and several examples are shown in Equations 17.77 and 17.78. - The reactions in Equations 17.77 and 17.78 illustrate the different regiochemistry of the products from reactions catalyzed by molybde num and rhodium. Computational studies indicate that different geometries of octahedral Mo(0), and square-planar Rh(I) species account for the different regioselectivities. ... 

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