Catalytic asymmetric dihydroxylation of olefins using a recoverable and reusable ligand

A free bis-cinchona alkaloid derivative ligand was prepared by a simple synthetic manipulation. With ligand/olefin mole ratio of 1%, the asymmetric dihydroxylation reactions of six olefins proceeded smoothly to give the chiral vicinal diols in high chemical yields and optical yields. The ligand itself could be recovered quantitatively by a simple operation and reused five times without loss of enantioselectivity.