Catalytic Asymmetric Synthesis of Chiral Propargylic Alcohols For the Intramolecular Pauson-Khand Cycloaddition

Several methods for the catalytic asymmetric alkyne addition to aldehydes arc Used to prepare die propargylic alcohol-based chiral en-ynes Protection Idle propargylic alcohols with either an acetyl or a methyl group allows the resulting en-ynes to undergo the intramolecular Pauson-K hand reaction to form the corresponding optically active 5 5- and 5,6-fused bicyclic products with high diastereoselectivity and high enantiomeric purity In the major product, the propargylic substituent and the bridgehead hydrogen are ers, with respect to each other on the fused bicyclic Hugs Hie enantiomeric purity of the propargylic alcohols generated from the asymmetric alkyne addition is maintained in the cycloaddition products The allylic ethers of the chital propargylic alcohols are prepared which can also undergo the highly diastereoselective Pauson-K hand cycloaddition with retention of the high enantiomeric purity This study has shown that the we of the substituents at the propargylic position as well as on the alkyne is important for the diastereoselectivity with the greater bulkiness of the substitutents giving higher diastereoselectivity