Novel bis(oxazoline) ligands derived from camphoric acid for Cu-catalyzed asymmetric cyclopropanation

Novel bis(oxazoline) ligands with additional chiral centers in the linker between the oxazoline groups were conveniently synthesized and applied to Cu-catalyzed asymmetric cyclopropanation of olefin with diazoacetate. Enantiomeric excess up to 81% was obtained for 1,1-diphenylethylene; however, the enantioselectivity for styrene was poor. The chiral centers in the oxazoline group controlled the configuration of the products, while no significant matching or mismatching problem between the chiral centers of the main oxazoline groups and the camphor backbone was observed.