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 th at the enantiomeric integrity of the desymmetrised complex is conserved in the cyclopentenone product. Moreover, the major enantiomer obtained in thes e reactions is opposite to that from a direct brucine N-oxide promoted Paus on-Khand reaction, allowing the preparation of either enantiomeric cyclopen tenone in enriched form from a single source of chirality. (C) 2000 Elsevie r Science Ltd. All rights reserved.