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OH
O
R
1
R
3
R
1
R
3
10 mol% VO(acac)
2
, O
2
(1 atm)
CH
2
Cl
2
R
2
R
2
d
n
4
r
4
n
g
|
5
OH
O
72-97%
Scheme 6.32 Aerobic oxidation of hydroquinones to quinones catalyzed by
VO(acac)
2
.
2 H
+
+ O
2
H
2
O
2
V
4+
V
4+
V
4+
O
O
O
V
3+
V
4+
V
5+
OH
O
R
1
R
3
R
1
R
3
2 H
+
+
R
2
R
2
.
OH
O
Scheme 6.33 Plausible reaction mechanism for the oxidation of hydroquinones.
O
O
O
1 mol% VO(OEt)Cl
2
, O
2
(1 atm)
O
OH
R
2
R
3
R
1
+
or
R
1
EtOH
OEt
R
2
R
2
R
3
OEt
R
3
R
3
= H
O
= H
CO
2
Et
CO
2
Et
OH
1 mol% VO(OEt)Cl
2
, O
2
(1 atm)
EtOH, rt, 15 min
OH
OH
74%
Scheme 6.34 Aerobic cleavage of a-hydroxycarbonyls catalyzed by VO(OEt)Cl
2
.
R
1
HO
OH
O
O
R
3
2.4 mol% VOCl
3
, O
2
(1 atm)
+
R
1
R
2
R
3
R
4
R
2
R
4
AcOEt, rt
Scheme 6.35 Aerobic cleavage of tertiary glycols catalyzed by VOCl
3
.
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