Chemistry Reference
In-Depth Information
TABLE 9.2. Palladium - Catalyzed Asymmetric Hydrosilylation of Cyclopentadiene
H
MeO
H
Me
Me
F
17
C
8
F
7
C
3
Me
Me
Fe
Fe
Ph
2
P
Ph
2
P
PPh
2
(
S
)-(
R
)-
37
(
S
)-(
R
)-
38
(
R
)-mop-phen (
40
)
NHSO
2
CF
3
PPh
2
(
S
)-
39
Me
Me
Ph
2
P
Ph
2
P
OMe
OMe
Me
Me
(
R
)-Ar-mop (
41
)
(
R
)-
42
Catalyst
(mol %
Pd)
Temp
( ° C)
Time
(h)
Yield
(%)
Entry Ligand L *
HSiX
3
% ee
References
1 . (
R
) - (
S
) - ppfa (
11
)
0.01
HSiMeCl
2
30
20
87
25 (
S
)
[24a]
2 . (
S
) - (
R
) -
37
0.02
HSiCl
3
0
2 0
7
60 (
R
)
[24b]
3 . (
S
) - (
R
) -
38
0.02
HSiCl
3
25
90
41
55 (
R
)
[24b]
4 . (
S
) -
12
0.1
HSiMeCl
2
− 20
40
35
71 (
S
)
[7d]
5 . (
S
) -
39
0.1
HSiMeCl
2
0
40
84
72 (
S
)
[7d]
6 . (
R
) - MeO - mop (
14
)
0.1
HSiCl
3
20
14
100
39 (
R
)
[26]
7 . (
R
) - H - mop (
13
)
0.1
HSiCl
3
20
3
91
28 (
R
)
[26]
8 . (
R
) - mop - phen (
40
)
0.1
HSiCl
3
20
120
99
80 (
R
)
[26]
9 . (
R
) - Ar - mop (
41
)
0.25
HSiCl
3
−
20
72
89
90 (
S
)
[27]
10. (
R
) -
42
0.25
HSiCl
3
−
30
168
75
91 (
S
)
[28]
ligand
11
, single regioisomer
53
was obtained with moderate enantioselectivities [24b,31].
Enantioselectivities were also improved by using Ar-mop ligand
41
and its dioctylated
derivative
42
[28]. Recently, a new type of chiral ferrocenylmonophosphine ligand
54
having two planar chiral ferrocenyl moieties on phosphorus atom was reported in the
hydrosilylation of 1,3 - decadiene (
52b
) [32] . The bis(ferrocenyl)monophosphine
54
((
S
) -
(
R
)-bisppfOMe) ligands were more enantioselective than Ar-mop ligands
41
and
42
. The
(
S
) - (
R
) - bisppfOMe
54d
containing bis(trifl uoromethyl)phenyl group was the most enan-
tioselective ligand to give 93% ee in the reaction of 1,3-decadiene (
52b
) (Table 9.4 ).
Enantiomerically enriched allenylsilanes were obtained by palladium-catalyzed
asymmetric hydrosilylation of 1-buten-3-ynes substituted with bulky groups at the alkyne
terminus (Scheme 9.11) [33]. The reaction with bisppfOMe ligand
54a
proceeded in
a 1,4-fashion to give allenyl(trichloro)silanes (
56
) with high regio- and enantio-
selectivities. High enantioselectivity (90% ee) was observed in the reaction of 5,5 - dimethyl -
