A new class of substituted aryl bis(oxazoline) ligands for highly enantioselective copper-catalyzed asymmetric aldol addition of dienolsilane to pyruvate and glyoxylate esters

A new class of bis(oxazoline) ligands are introduced that feature o-alkoxyaryl substituents and provide the highest enantioselectivities yet reported for the copper-catalyzed asymmetric dienosilane aldol addition to pyruvate and glyoxylate esters. Enantioselectivities up to 98% ee (before recrystallization) and isolated yields up to 91% were observed. Additionally, chloride counterions were found to be superior to triflate for this reaction.