Stereoselective Pauson-Khand Reactions via the Chiral [(alkyne)Co2(CO)5{P(OMe)3}]
摘要:
Dicobalt hexacarbonyl complexes of menthyl-substituted propargyl alcohol react with PR(3) (R = OMe, Ph) to form diastereomeric mixtures of complexes 3. The isomeric complexes can be separated chromatographically. The isolated diastereomers can be used in the intra- and intermolecular Pauson-Khand reaction to give high yields of cyclopentenones with high diastereoselectivities or high enantioselectivities.
The trimethylphosphite substituted pentacarbonylpropargyldicobalt cation, [(CHCCH2) Co2(CO)5L]+ [L = P(OMe)3], is significantly more stable than its phosphine analogues (L = PPh3, PBu3), and has been converted to a series of ethers. (CHCCH2OR)Co2(CO)5L. Reaction of the (cholesteryl propargyl ether)hexacarbonyldicobalt complex with trimethylphosphite proceeds without stereoselectivity, and the product