Preparation of enantiomerically pure p-substituted phenylethyl hydroperoxides by kinetic resolution and their use as enantioselective oxidants in the asymmetric Weitz–Scheffer epoxidation of E-chalcone

Abstract The kinetic resolution of a variety of secondary para -substituted phenylethyl hydroperoxides by Raphanus sativus L. (black radish peroxidase) in the presence of guaiacol is reported. The peroxidase enzyme recognized ( R )-configured alkyl aryl hydroperoxides, which furnished optically active ( S )-hydroperoxides and ( R )-alcohols. Kinetic resolution of tertiary hydroperoxides by the enzyme was unsuccessful. This study also shows how the optically active p -substituted ( S )-hydroperoxides obtained can be employed as enantioselective oxidants in the asymmetric Weitz–Scheffer epoxidation of E -chalcone in the presence of KF-Al 2 O 3 as a base. In all cases, a chalcone epoxide with the (α S ,β R )-configuration was obtained as the major isomer. Under the optimized reaction conditions, the enantiomeric excess of the chalcone epoxide was obtained in up to 49% in CH 3 CN at −40 °C.