Homogeneous catalytic asymmetric epoxidation (AE) is a welstudied
process that has been thoroughly investigated over the years
and whose state of the art has been recently reviewed.1 The
discovery of the TiIV-diethyl tartrate (DET) catalytic system
developed by Sharpless2 for the stereoselective epoxidation of allylic
alcohols has been a major landmark in AE. The substrate scope of
the reaction was further extended by Jacobsen3 and Katsuki4 with
MnIII-Salen complexes to the asymmetric epoxidation of unfunctionalized
di- and trisubstituted alkenes. More recently electronpoor
CdC double bonds such as those in enones have been
asymmetrically epoxidized under nucleophilic oxidation conditions.5,1b
While the AE of styrene derivatives can be performed with several
metal catalysts ranging from chiral iron and manganese porphyrins6
to RuIII,7 to organic catalysts,8 simple terminal unfunctionalized
alkenes are still challenging substrates for direct AE9 because of
their intrinsically low reactivity toward electrophilic oxidation, along
with the difficulty to control the prochiral faces of the simply
monosubstituted double bond.