Chemistry Reference
In-Depth Information
OMe
OMe
Ni(cod)
2
(14 mol %), (
R
)-binap (
85
)
OMe
+
OMe
H
Al(Bu-
i
)
2
O
Toluene, rt,1 h
OH
137
:97%yield
97% ee
136
Scheme 9.31.
The fi rst example of catalytic enantioselective hydrostannation of cyclopropenes
using chiral rhodium catalysts was reported recently [72]. The reaction of
126
with
Me
3
SnH promoted by rhodium catalysts coordinated with chiral diphenylphosphinoben-
zoic acid-derived ligand
139
at − 30 ° C afforded the
trans
- cyclopropylstannane
138
in 94%
ee with excellent regioselectivity (Scheme 9.32 ).
Me
SnMe
3
Me
[RhCl(cod)]
2
(3 mol %),
139
H
+
H
SnMe
3
MeO
2
C
H
MeO
2
C
THF, -30
°C, 45 min
126
138
:90%yield
94% ee
Ph
Ph
O
O
NH
HN
PPh
2
Ph
2
P
(
R
,
R
)-
139
Scheme 9.32.
9.5. CONCLUSION
During the last decade, catalytic asymmetric hydrosilylation and hydroboration of car-
bon-carbon double bonds have been developed to expand their synthetic utilities by
exploiting new catalytic systems including substrates, reagents, and catalysts, as well as
to achieve very high catalytic activity and enantioselectivity. In the hydrosilylation reac-
tion, scopes of substrates have been broadened to enable new utilizations of asymmetric
hydrosilylation. For example, asymmetric hydrosilylation of olefi ns has been extended
to palladium-catalyzed hydrosilylation of 1,3-enynes, giving optically active allenylsi-
lanes and rhodium-catalyzed intramolecular cyclization/hydrosilylation of 1,6-dienes and
1,6-enynes giving a cyclic hydrosilylated product. Cyclopropenes,
meso
- hydrazines, and
heterofunctional allylic compounds as new substrates and pinacolborane as a new
hydroborating reagent have been successfully applied in the hydroboration reaction. It
has been also discovered that hydrostannanes are added to carbon-carbon double bonds
asymmetrically in the presence of a chiral catalyst. These asymmetric heterofunctional-
izations of olefi n are expected to be applied to industrial production of useful chiral
compounds in near future.
