Bis(oxazoline) as Chiral Ligand

C₂-Symmetric bisoxazoline 1 is a useful chiral ligand for enantiocontrol of metal-catalyzed reactions. For example, the chiral Cu(I) complex, which is generated from 1 and copper(I) triflate, is applied to asymmetric cyclopropanation of olefins and affords trans-diastereomers with high enantioselectivity.¹⁾ The reaction was used for total syntheses of (+)- and (-)-Scopadulcic acid A.²⁾

Recently, Cu(II) complex of 1 have been successfully employed as enantioselective Lewis acid catalyst in Diels-Alder reactions,³⁾ Aldol additions,⁴⁾ and Michael additions.⁵⁾