Chemistry Reference
In-Depth Information
Carbon
Nitrogen
Oxygen
Copper
d
n
4
r
4
n
g
|
0
CH
2
OH
CHO
O
2
/ TEMPO/ H
2
O, 50
o
C
Figure 2.16 Oxidation of benzyl alcohol by a dinuclear copper complex of 3-(2-
hydroxy-4-nitrophenylhydrazo)pentane-2,4-dione in aqueous solution.
R
2
R
1
R
1
R
2
R
3
R
3
OH
HO
O
HN
N
HN
O
O
N
N
O
HN
HN
NH
O
OH
N
N
HO
HO
O
Si
Si
A
B
C
Figure 2.17 Ligands used in the aerobic oxidation of alcohols. A, alanyl-4,6-O-
ethylidene-b-
D
-glucopyranosylamine; B, N,N-di(pyridine-2-yl)-2,2-
bipyridine-6,6-diamine; and C, disiloxane-derived Schiff-base ligands.
.
oxidation of a range of both primary and secondary benzylic and aliphatic
alcohols in the presence of a base at room temperature in acetonitrile.
69
TEMPO-mediated aerobic oxidation of benzyl alcohols and its derivatives
catalyzed by a copper complex of a b-diketone azo derivative 3-(5-chloro-2-
hydroxy-3-sulfophenylhydrazo)pentane-2,4-dione ligand in aqueous medium
was reported.
70
The complex builds a three-dimensional supramolecular
architecture with hydrogen-bonded water molecules in its structure, as is
evident from the X-ray crystal structure. Copper(
II
) complexes of alkoxy-1,3,5-
triazapentadienato have been used as ecient catalysts for the TEMPO-
mediated aerobic oxidation of alcohols with high selectivities under mild
conditions.
71
Recently, copper complexes of the tetrapyridyl ligand N,N-
di(pyridin-2-yl)-2,2-bipyridine-6,6-diamine (B in Figure 2.17) have been re-
ported to serve as a catalyst in the oxidation of benzyl alcohol in the presence
of TEMPO and a base.
72
Mononuclear copper complexes of a salen-type
ligand containing a disiloxane unit (C in Figure 2.17) have been utilized in
the aerobic oxidation of alcohols that exhibit very high catalytic TONs of
aldehyde products.
73,74
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