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CH
2
OH
CHO
TEMPO, Cu(II) complexes
+
H
2
O
1/2 O
2
+
H
2
O, K
2
CO
3
, 80
O
C
d
n
4
r
4
n
g
|
0
R
R =
N
N
Cl
CH
3
Cu
N
N
R
F
Figure 2.14 Aerobic oxidation of alcohols catalyzed by copper(
II
)2-N-arylpyrrole-
carbaldimine-based catalyst systems.
R
N
O
Cu
N
O
HO
R
O
0.33 mol% Complex, 1.3 mol% TEMPO,
O
2
, Toluene, 100 °C
.
R = Ph,
-NO
2
Ph, isopropyl,
cyclohexyl, CH
2
Ph, CH
2
CH
2
Ph
p
-MePh,
p
Figure 2.15 Copper complexes of 3,5-di-tert-butylsalicylaldimine-derived ligands
used in the catalytic oxidation of benzyl alcohol.
(Figure 2.15). The catalysts are able to catalyze the aerobic oxidation of a
wide range of benzylic, allylic and primary aliphatic alcohols but perform
poorly with secondary aliphatic alcohols.
64,65
Multinuclear Cu(
II
)-triethanolaminate complexes have been reported to
catalyze the aerobic oxidation of alcohols in the presence of TEMPO or
acetamido-TEMPO (A and C in Figure 2.2) in acetonitrile.
66
Pombeiro and co-
workers utilized multinuclear Cu(
II
)-triethanolaminate complexes in the
TEMPO-assisted aerobic oxidation of benzyl alcohols in the presence of a
base in pure water.
67
The aerobic oxidation of benzylic alcohol in an aqueous
medium has also been performed with good catalytic yields by using a
dimeric copper complex of 3-(2-hydroxy-4-nitrophenylhydrazo)pentane-
2,4-dione (Figure 2.16).
68
A combination of a chloro-bridged dicopper(
II
) complex of phen,
[(phen)Cu(m-Cl)(Cl)]
2
, and TEMPO has been reported to catalyze the
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