Asymmetric Kinugasa Reaction of Cyclic Nitrones and NonracemicAcetylenes

摘要

Kinugasa reactions between chiral acetylenes and five-membered nitrones, achiral and bearing a stereogeniccenter in both enantiomeric forms, proceed in moderate to good yield with high diastereoselectivityaffording mostly one dominant product. The first step of the reaction is controlled by the configurationof the nitrone, whereas the protonation of intermediate enolate in the second step depends mainly on theconfiguration of the bridgehead carbon atom formed in the first step. In the case of the mismatched pair,the configuration at the C-6 center of the carbapenam skeleton may also be affected by the configurationof the stereogenic center in the acetylene portion.