Rh-catalyzed highly enantioselective formation of functionalized cyclopentanes and cyclopentanones.

A catalyst system, [Rh(COD)Cl](2)-BINAP-AgSbF(6), has been developed as a second-generation catalyst for the cycloisomerization of 1,6-enynes tethered by carbon chains. Cyclopentanes and cyclopentanones, which can contain functional groups, such as the 1,4-dienes, vinyl ether, aldehyde etc., were obtained from readily available starting materials in high yields and selectivities. Both regioselectivities and enantioselectivities are excellent: only 1,4-dienes were observed and in over 99% ee.