Chemistry Reference
In-Depth Information
Table 5.1 Chemoselective hydrogenation reaction of a,b-unsaturated ketones to
a,b-unsaturated alcohols catalyzed by Au
25
(SR)
18
nanocluster catalysts.
R
3
R
3
Au
25
(SR)
18
,r.t.
R
1
R
2
R
1
R
2
OH
UA
H
2
, toluene/ethanol,
d
n
9
r
4
n
g
|
3
O
Conversion (%)
Au
25
Entry
Substrates
Selectivity for UA
Au
25/
Fe
2
O
3
Au
25/
TiO
2
CHO
1
100
38
49
46
H
3
C
2
100
43
53
51
CHO
H
3
C
CHO
CH
3
3
100
44
54
53
H
3
C
H
3
C
4
100
39
52
52
CHO
H
2
C
H
3
C
CH
3
O
5
100
29
45
44
H
3
C
91
a
6
46 47 47
a
The selectivity for unsaturated alcohol (UA) is 90% (free Au
25
(SR)
18
catalyst, denoted as Au
25
), 92%
(Au
25
(SR)
18
/Fe
2
O
3
catalyst, Au
25
/Fe
2
O
3
), and 91% (Au
25
(SR)
18
/TiO
2
catalyst, Au
25
/TiO
2
), respectively.
Adapted with permission from ref. 39.
CHO
H
2
C
O
O
Ph
Ph
.
Au
25
(SR)
18
H
2
,r.t.
N
N
Yield: ~18%
Stereoselectivity: 100%
HO
O
H
Ketone
Exo-alcohol
Scheme 5.4 Stereoselective hydrogenation reaction of bicyclic ketone to exo-alcohol
catalyzed by Au
25
(SR)
18
nanocluster catalysts.
a,b-unsaturated ketones and aldehydes; moderate yields and high selectivity
were obtained (Table 5.1).
Zhu et al.
40
further expanded the Au
25
(SR)
18
nanocluster catalyst for
stereoselective hydrogenation of a bicyclic ketone (i.e., 7-(phenylmethyl)-3-
oxa-7-azabicyclo [3.3.1] nonan-9-one) to exo-alcohol (Scheme 5.4). The
stereoselective hydrogenation was run at room temperature in an ethanol/
toluene (5 : 1, v/v) mixed solvent using H
2
(1 atm) as hydrogen source;
18%
conversion of the bicyclic ketone with 100% selectivity for the exo-alcohol
was obtained; note that the stereoselective product was determined by
nuclear magnetic resonance (NMR) spectroscopy.
40
The high stereoselectivity
(100%) was rationalized to be effected by the atomic spatial restraints and the
unique core-shell configuration of the Au
25
(SR)
18
nanocluster.
B
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