Chemistry Reference
In-Depth Information
H
H
H
O
H
H
O
t
-Bu
O
K
O
H
t
-Bu
O
O
H
d
n
4
r
4
n
g
|
5
N
H
H
1) KOH or KO
Bu, aq MeOH
2) VOSO
4
-xH
2
O, MeOH
t
O
N
O
t
-Bu
OH
V
t
-Bu
O
O
t
-Bu
V
O
t
-Bu
cluster
4
O
OH
OH
1.25 mol% cluster
O
2
, toluene, rt
X
R'
XR'
X
R'
+
R
R
R
O
O
O
K
se l
40- >500
Scheme 6.13 Oxidative kinetic resolution of a-hydroxycarbonyls catalyzed by a
pentanuclear C
4
-symmetric cluster complex.
t
-Bu
O
(
)
n
O
N
O
5 mol% CuI
EtN(
V
Pr)
2
THF, DMF
i
+
OCH
3
X
O
O
CH
3
H
N
3
t
-Bu
t
-Bu
O
.
N
N
N
O
N
O
V
X
OCH
3
O
O
H
CH
3
PSS catalyst
t
-Bu
X = -OCH
2
- or -CH
2
OCH
2
-
O
OH
OH
5 mol% PSS catalys
t
O
2
,CHCl;
3
, rt
X
R'
XR'
X
R'
+
R
R
R
O
O
O
64-96%
ee
Scheme 6.14 Oxidative kinetic resolution of a-hydroxycarbonyls catalyzed by re-
cyclable vanadium complexes.
reused at
least
four
times without
a decrease
in reactivity or
enantioselectivity.
Unfortunately, asymmetric oxidation of a-hydroxy ketones provided
products with only moderate selectivity using the chiral vanadyl complexes
developed by Chen and co-workers.
20
Therefore, they undertook further in-
vestigations into the effective kinetic resolution of a-hydroxy ketones using
Search WWH ::
Custom Search