Preparation and reaction of desymmetrised cobalt alkyne complexes

Prochiral alkyne hexacarbonyl dicobalt complexes are desymmetrised directly with brucine N-oxide in the presence of a phosphine or phosphite ligand to produce the corresponding phosphorus-containing pentacarbonyl complex with appreciable enantiomeric excess. In Pauson–Khand reactions, it is found that the enantiomeric integrity of the desymmetrised complex is conserved in the cyclopentenone product. Moreover, the major enantiomer obtained in these reactions is opposite to that from a direct brucine N-oxide promoted Pauson–Khand reaction, allowing the preparation of either enantiomeric cyclopentenone in enriched form from a single source of chirality.