Friday, 18 May 2007 - 9:10 AM
210 (Pfahler Hall)
409

Direct, Enantioselective Generation of (Z)-Disubstituted Allylic Alcohol

Luca Salvi, Sang-Jin Jeon, Ethan L. Fisher, Patrick J. Carroll, and Patrick J. Walsh. University of Pennsylvania, Philadelphia, PA

A novel catalytic asymmetric method for the synthesis of (Z)-disubstituted allylic alcohols will be presented. Our one-pot procedure entails hydroboration of chloro alkynes and addition of a hydride source (t-BuLi), which results in formation of a (Z)-vinylborane. Boron to zinc transmetalation of the vinyl group with ZnEt2 and addition of a chiral ligand and substrate aldehyde results in formation of racemic (Z)-allylic alcohols. Unfortunately, the LiCl (generated on addition of t-BuLi ) is a much faster catalyst than the asymmetric catalyst. We have found, however, that addition of TEEDA to inhibit the background reaction promoted by LiCl allows direct generation of enantioenriched (Z)-allylic alcohols for the first time.


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