Chemistry Reference
In-Depth Information
[Pd Cl( -
C
3
H
5
)]
2
/L*
(1 mol % Pd)
p
H
t
-Bu
t
-Bu
+HSiC
3
¤
Cl
3
Si
Me
55
(
S
)-
56
L* =
54a
:90%eeat0 C
57
:92%eeat0 C
MeO
P
R*
R*
Ph
R* =
P
Fe
Fe
OMe
Fe
OMe
(
S
)-(
R
)-bisppfOMe (
54a
)
57
Scheme 9.11.
SiCl
3
Pd/(
S
)-MeO-mop (
14
)
Cl
3
Si
+
R
+
HSiCl
3
R
R
40 C
58
:R=
n
-C
6
H
13
60
>90% yield
59
(
59
/
60
=93/7)
1) EtOH/Et
3
N
2) H
2
O
2
KF/KHCO
3
OMe
Ph
2
P
OH
R
(
S
)-MeO-mop (
14
)
(
R
)-
61
:95%ee
Scheme 9.12.
which enantioselectivity was determined to be 95% ee after Tamao oxidation, in a
ratio of 7 to 93 (Scheme 9.12).
High enantioselectivity as well as high regioselectivity has also been achieved with
mop ligands in palladium-catalyzed asymmetric hydrosilylation of alkyl-substituted ter-
minal alkenes. Recently spiro phosphoramidite ligand
23
was found to show a moderate
enantioselectivity in the hydrosilylation of 1-hexene [19b].
Catalytic system of palladium/MeO-mop also showed high enantioselectivity and
catalytic activity in the hydrosilylation of cyclic alkenes, such as norbornene and
bicyclo[2.2.2]octene, 2,5-dihydrofuran, and norbornadiene [7c,36]. The hydrosilylation
of norbornene (
62
) gave
exo
- adduct exclusively (Scheme 9.13 ) The hydrosilylated
product was converted to
exo
- 2 - norbornanol (
64
) or
endo
- 2 - bromonorbornane (
65
) via
the corresponding pentafl uorosilicate. Chiral ferrocenylmonophosphines in addition to
MeO - mop (
14
) were found to be effective ligands for the reaction [15e,f]. Planar chiral
