DIASTEREOSELECTIVITY IN THE INTERMOLECULAR PAUSON-KHAND REACTION OF CHIRAL 2-ALKYNOATES

Chiral 2-alkynoates have been readily prepared by condensation of seve ral cyclohexyl- or camphor-based alcohols with 2-alkynoic acids or the corresponding acid chlorides, The hexacarbonyldicobalt complexes obta ined therefrom reacted with olefins to afford the corresponding Pauson -Khand cyclopentenone adducts in good yields, with high regioselectivi ty, and with variable degrees of diastereoselectivity. In some instanc es, the degree of stereocontrol is superior to that observed for alkox yacetylenes, set that the viability of an enantioselective approach to the intermolecular Pauson-Khand reaction of electron-deficient alkyne s is demonstrated for the first time.