Synthesis of a Recyclable Chiral Ligand and Its Catalytic Performance for Asymmetric Dihydroxylation of Olefins

A novel recoverable and reusable chiral ligand for asymmetric dihydroxylation of olefins was prepared from 1,4-difluoroanthraquinone by two steps. The high enantioselectivity (80%～97%) and catalytic activity (80%～94%) were obtained in two different systems. The ligand not only exhibited the excellent enantioselectivity like free alkaloid derivative chiral ligands, but also could be recovered and reused as easily as polymer-supported ligands. What is more, the amount of the ligand was less than that of the polymer-supported ligands. In the asymmetric dihydroxylation of trans-ethyl cinnamate, the ligand could be used for 5 circles in the system of t-BuOH-H 2O/K 3Fe(CN) 6 (the average recovery was 93%) and for 8 circles in the system of Me 2CO-H 2O/NMO with consistent activity and enantioselectivity.