Highly enantioselective addition of methyl propiolate to aldehydes catalyzed by a titanium(IV) complex of a β-hydroxy amide
摘要:
Three chiral beta-hydroxy amide ligands were prepared by the reaction of benzyl chloride with amino alcohols derived from L-tyrosine. The titanium(IV) complex of chiral ligand 4a was found to be an effective catalyst for the asymmetric addition of methyl propiolate, to aliphatic and aromatic aldehydes. The gamma-hydroxy-alpha,beta-acetylenic esters were obtained in excellent enantiomeric excesses (up to 94% ee) under optimized conditions. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.