Highly Enantioselective Synthesis of gamma-Hydroxy-alpha,beta-acetylenic Esters by Asymmetric Alkyne Addition to Aldehydes

摘要

gamma-Hydroxy-alpha,beta-acetylenic esters containing three adjacent and structurally very different functional groups are very useful in the synthesis of highly functionalized organic molecules.This class of compound is normally prepared by treatment of an alkyl propiolate with nBuLi at < -78 deg C followed by the addition of aldehydes,as originally reported by Midland etal.Recently,Shahi and Koide reported a milder method in which AgC ident to CCO_2Me was reacted with aldehydes in the presence of [Cp_2ZrCl_2] (Cp = cyclopenta-dienyl) and AgOTf (Tf = trifluoromethanesulfonyl) at room temperature.