<P>Enantioselective epoxidation of olefins is a challenging and
useful synthetic transformation.
[
1]
Since
its introduction in the early nineties, Jacobsen’s catalyst
has proved reliable for highly enantioselective epoxidation of prochiral
olefins.
[
2]
Belonging to the
salen-ligand class,
[
3]
the
catalyst has a manganese core in a square planar geometry,
stabilised with a chlorine atom in the axial position.
[
2]
Several stoichiometric
oxidants have been used successfully,
[
4]
with
NaOCl the most frequently involved.
[
1a]
[
b]
[
5]
Easy
to prepare, the catalyst has become commercially available in both
enantiomeric forms.
[
6]
Applied also
for the enantioselective oxidation of sulfides to sulfoxides,
[
4e]
and for the oxidation of hydrocarbons
at the benzylic position,
[
4c]
the
catalyst has even been synthesised in a dimeric form for the epoxidation
of olefins under heterogeneous conditions.
[
7]
Recently,
it has provided the first example of didehydrogenation of secondary
hydroxylamines to the corresponding nitrones.
[
8]
</P>
