Chemistry Reference
In-Depth Information
1a
(2 mol% )
air
OH
OH
O
+
R
1
R
2
R
1
R
2
R
1
R
2
h
ν
,rt
d
n
4
r
4
n
g
|
1
1b
(2 mol% )
air
OH
OH
O
+
R
1
R
2
rt, MS 5 Å
R
1
R
2
R
1
R
2
OH
OH
N
X
N
1a
: conv. = 64.7%
ee = 94.9%, k
rel
=11
1a
: conv. = 60.7%
ee = 9 0.6 %, k
rel
=11
Ru
O
O
Cl
: con v. = 55 .6%
e e = 94.3% , k
rel
=25
1b
: c onv. = 63.5%
ee = 9 5.3 %, k
rel
=12
1b
R
R
OH
OH
1a
:X=ON,R= Ph
1b
:X=H
2
O, R = Me
1a
: conv. = 57.8%
ee = 8 2.1 %, k
rel
=11
1a
: conv. = 65.3%
ee = >99.5%, k
rel
=20
OH
Br
OH
OH
.
1b
: conv. = 51.2%
ee = 93.5%, k
rel
=60
:conv.=58.2%
ee = 98 .3% , k
rel
=26
1b
:conv.= 60.9%
ee = 91.5%, k
rel
=12
1b
Scheme 9.3 Ru(salen)-catalyzed aerobic oxidative kinetic resolution of racemic
secondary alcohols.
could be performed with air at room temperature by using Cs
2
CO
3
-chloro-
form-modified conditions (Scheme 9.5).
10
These palladium-based aerobic
oxidations of alcohols is particularly described in Chapter 4.
Chen and co-workers
11
and Toste and co-workers
12
independently
reported that vanadium-Schiff base complexes serve as ecient catalysts for
the aerobic OKR of a-hydroxy esters and related compounds, albeit under a
dioxygen atmosphere. On the other hand, focusing on group 9 metals,
Ikariya and co-workers developed ecient chiral iridium and rhodium
complexes 3 for asymmetric transfer hydrogenation reactions in 1999
(Scheme 9.6).
13
Later, Heiden and Rauchfuss
14
and Ikariya and co-workers
15
independently discovered that these Cp*metal-amine complexes 3c are
oxidized by molecular oxygen to give Cp*iridium-amide complexes 4
(Scheme 9.7).
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