Asymmetric Epoxidation of Allylic Alcohols Catalyzed by Vanadium–Binaphthylbishydroxamic Acid Complex

A vanadium–binaphthylbishydroxamic
acid (BBHA) complex-catalyzed
asymmetric epoxidation of allylic alcohols is described. The optically
active binaphthyl-based ligands BBHA 2a and 2b were synthesized from (S)-1,1′-binaphthyl-2,2′-dicarboxylic
acid and N-substituted-O-trimethylsilyl
(TMS)-protected hydroxylamines via a one-pot, three-step procedure.
The epoxidations of 2,3,3-trisubstituted allylic alcohols using the
vanadium complex of 2a were easily performed in toluene
with a TBHP water solution to afford (2R)-epoxy alcohols
in good to excellent enantioselectivities.