Asymmetric cyclopropanation of 2,5-dimethyl-2,4-hexadiene by copper catalysts bearing new bisoxazoline ligands.

Some new bisoxazoline ligands with an aryl group at the 4-position and gem-dimethyl groups at the 5-position on the oxazoline ring were prepared from arylglycines. Remarkable enhancement of the trans-selectivity (trans/cis = 87/13) and the enantioselectivity (96% ee for the trans product) was demonstrated for the asymmetric cyclopropanation of 2,5-dimethyl-2,4-hexadiene with tert-butyl diazoacetate catalyzed by the new copper-bisoxazoline complex.