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promote a faster electron transfer between Shvo's catalyst 7 and the oxygen-
activating agent, Co(salophen) 9.
A variety of aliphatic and benzylic secondary substrates (including steri-
cally hindered alcohols) were reacted with this three-component catalytic
system (7-9). The reaction proceeded in excellent yields and with high
turnover frequencies (TOFs) (Table 7.1).
12
For example, TOFs 44000 h
1
were
observed for the dehydrogenation of 1-phenylethanol (Table 7.1, entry 1).
Reactive Z carbon-carbon double bonds were inert under these mild reaction
conditions (Table 7.1, entry 4). No epoxide formation was observed, or the
reduction of the double bond, despite the presence of ruthenium-hydride 7a.
Table 7.1 Ruthenium-catalyzed biomimetic aerobic oxidation of
secondary
alcohols.
7
(0.5 mol % )
2,6-dimethoxybenzoquinone
8
(20 mol % )
9
(2 mol %)
R
2
R
2
R
1
R
1
OH
O
air (1 atm), toluene, 1 00 °C
Me
P
h
O
H
O
Ph
N
Ph
Ph
Ph
Ph
N
N
Ph
Ph
Ru
Ru
CO
Co
OC
CO
H
OC
O
O
Shvo's catalyst
7
Co(salophen )
9
Reaction
time(h)
Yield
a,b
(%)
Entry
Substrate
Product
OH
O
1
1
89
OH
O
2
2
81
b
Ph
CO
2
Me
Ph
CO
2
Me
OH
O
3
1
92
C
6
H
13
C
6
H
13
OH
O
4
2.5
92
C
4
H
9
C
4
H
9
5
6
1
1
88
n=0
OH
O
92
n=1
7
1
95
c
n=1
n
n
8
1
92
n=2
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