Chemistry Reference
In-Depth Information
P
solv
H
2
O
Pt
+
*
F
O
P
R
H
2
O
2
F
F
F
F
CF
3
SO
-
R
H
H
P
O
H
P
solv
Catalytic cycle
Pt
+
F
Pt
+
O
*
*
O
F
F
H
P
P
O
F
F
F
H
H
CF
3
SO
-
F
F
F
F
CF
3
SO
-
R
H
H
P
R
Pt
+
F
O
*
F
H
P
O
F
H
F
F
CF
3
SO
-
Scheme 11.29.
HO
Polymer-supported catalyst
24
(5 mol
%)
O
O
O
N
*
H
H
+ 30% H
2
O
2
*
CH
2
Cl
2
/
t
BuOH
O
N
HO
20% ee
+ FeCl
2
24
Scheme 11.30.
11.3.5. Iron Catalyst
The development of not only more effi cient and selective but also sustainable reactions
has emerged as a research frontier in organic synthesis. In the fi eld of metal-catalyzed
reaction, iron-based catalysts are the most appealing due to the ubiquity and nontoxicity
of iron. Indeed, processes in nature utilize various iron-containing enzymes in biotrans-
formations. Thus, the improvement of asymmetric epoxidation catalysis of iron-based
complexes is a topic of current interests [45].
In 1999, Francis and Jacobsen investigated a library of 5760 ligand-metal complexes
by high-throughput combinatorial techniques and found that Fe
II
/peptide complex
24
supported on a polystyrene resin can promote the asymmetric epoxidation of
trans
-
β
-methylstyrene in the presence of aqueous hydrogen peroxide, albeit with the low
ee value of 20% (Scheme 11.30) [46]. On the other hand, in the course of studies on
