3.8.5.3 Asymmetric Epoxidation
Sharpless epoxidation of allylic alcohols is one of the important processes in asymmetric catalysis. It provides an effective route for the transformation of prochiral allylic alcohols are to epoxy alcohols in the presence of Ti(Oi -Pr)4 , t -BuOOH and ( R,R ) or ( S,S )-diethyltartarate (Scheme 11).
 |
Scheme 11 |
The reaction proceeds through a dimeric complex having two titanium centers (Scheme 12). The allylic hydroxyl group coordinates with the metal thereby allowing the transfer of oxygen atom from one face only.
 |
Scheme 12 |
 |
Scheme 13 |