A significant improvement in enantioselectivity, yield, and reactivity for the copper-bi-o-tolyl bisoxazoline-catalyzed asymmetric allylic oxidation of cyclic olefins using recoverable SBA-15 mesoporous silica material

A series of chiral bi-o-tolyl bisoxazoline ligands 1 and 2 were conveniently synthesized on a gram scale from inexpensive and commercially available 3-methyl benzoic acid in eight steps. The catalytic and induced asymmetric effects of the chiral copper (I) complexes of these ligands on the asymmetric allylic oxidation of cycloolefins were investigated in the presence of various nano-sized additives. When SBA-15 mesoporous silica was used in conjunction with these ligands very highly enantioselectivities (up to 97% ee) and excellent yields (up to 99%) of the corresponding chiral allylic esters were obtained in a reasonably short period of time.