Titanium 3,3′-Modified-Biphenolate Complexes Atropisomerically Controlled by TADDOLs: Novel Chiral Lewis Acid Catalysts for Asymmetric Methylation with an Achiral Methyl-Titanium Reagent

Abstract

Chiral Ti complexes, which are constituted of 3,3′-modified-biphenolate (BIPOLate) ligands atropisomerically controlled by (R)-TADDOLs, are shown to be novel chiral Lewis acid catalysts for the methylation reaction of aldehydes with an achiral methyl-titanium reagent. Thus, the chiral 3,3′-modified BIPOLate/TADDOLate-Ti complexes give enhanced enantioselectivities up to 100% enantiomeric excess.