1,4-Difluoroanthraquinone was obtained in 60% yield by Friedel-Crafts reaction of phthalic anhydride and 1,4-difluorobenzene in the presence of AlCl₃ followed by cyclization with polyphosphoric acid. Then the ligand (QN)₂AQN was prepared by nucleophilic substitution of 1,4-difluoroanthraquinone with the lithium salt of quinine in 85% yield. In the presence of benzyl N-chlorocarbamate (the oxidant and nitrogen source), five methyl cinnamates gave the vicinal amino alcohols via asymmetric aminohydroxylation (AA) catalyzed by (QN)₂AQN-OsO₄ complex in excellent enantioselectivities of 90%～96% ee, normal to high regioselectivities of 75∶25～98∶2 and good yields of 50%～70%. These results were comparable to those of the best catalyst reported for AA reaction. Due to the easy preparation and low cost, this new chiral ligand was applied to the catalytic asymmetric aminohydroxylation to produce enantioselective α-aminoacid esters.

Key words: asymmetric aminohydroxylation, chiral β-amino alcohol, α-aminoacid ester, (QN)₂AQN