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Keywords:

  • allylation;
  • asymmetric synthesis;
  • enantioselectivity;
  • lithium;
  • amines

Abstract

Catalytic asymmetric addition of nucleophiles to enals is a straightforward method towards enantioenriched allylic alcohols, which are important for the synthesis of natural and pharmaceutically active compounds. Reactive aryl lithiums, produced in situ from readily available and inexpensive aryl bromides and butyl lithium, were used to enantioselectively arylate a number of α-substituted cinnamaldehydes in the presence of tetramethylethylenediamine (TMEDA), AlCl3, and Ti(OiPr)4. This enabled enantioenriched linear trisubstituted allylic secondary alcohols in the catalysis of (S)-H8-BINOL-(TiOiPr)2 complex. TMEDA coordinated the lithium salt generated in situ during transmetallation and effectively inhibited the unwanted background reaction catalyzed by the Lewis acidic lithium salt.