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Ts
O
H
O
R
N
3
, KO-
t
-Bu
Ir
i-
PrO H, 30 ºC
H
2
Cl
R
d
n
4
r
4
n
g
|
1
3a
:M= Ir
3b
:M =Rh
Scheme 9.6 Asymmetric transfer hydrogenation using iridium- and rhodium-based
catalysts.
Ts
Ts
R
O
2
R
N
N
M
M
H
2
H
H
R
R
3c
4
Scheme 9.7 Oxidation of Cp*metal-amine complexes to the metal amide complexes
by O
2
.
Ms
4a
air
Ph
OH
O
H
O
N
+
Ir
R
1
R
2
THF, 30 ºC
R
1
R
2
R
1
R
2
N
Ph
H
4a
.
O
H
O
H
O
H
R
R = H
recovery = 48%
ee = 98%,
recovery = 50%
ee = >99%, k
r
el
= >100
recovery = 46%
ee = >99%, k
r
el
= 77.6
k
rel
= 91.3
R = OMe
recovery= 38%
ee = 98%,
k
rel
= 17.2
Scheme 9.8 Cp*iridium-chiral diamine catalyzed OKR of secondary alcohols.
enantioselective OKR of racemic secondary aromatic alcohols such as
1-phenylethanols, hydroxyindane and 1-hydroxytetralin in air under mild
conditions at 30 1C (Scheme 9.8). In particular, the resolution of the alcohols
proceeds with significant enantioselectivities at lower substrate concen-
tration (0.1-0.2 M).
The catalysis of OKR described above requires noble transition metals
such as ruthenium, palladium or iridium. In 2009, Sekar and co-workers
reported for the first time that an iron complex with chiral Schiff base ligand
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