Chemistry Reference
In-Depth Information
D-
xylo
R
1
R
2
O
O
P
Ph
2
P
O
O
O
O
O
=
O
O
O
O
O
R
2
R
1
Substrate
1b
Substrate
1d
60
% Conv
% ee
% Conv
% ee
R
1
= R
2
= H
R
1
= R
2
=
t
Bu
(
S
)
ax
(
R
)
ax
88.2
(
S
)
>99
(
R
)
a
b
c
d
84.1
(
S
)
98.8
(
R
)
100
100
100
100
98.3
(
S
)
97.6
(
R
)
91
(
S
)
94.3
(
R
)
100
100
100
100
D-
manno
O
O
R
1
R
1
P
O
O
TBDPSO
O
=
O
OTBDPS
O
O
P
e
R
1
=
t
Bu
f
R
1
= cyclohexyl
61e,f
O
D-
xylo
D-
ribo
O
O
P
O
P
O
O
O
P
H
H
O
O
O
g
R
1
=
t
Bu, R
2
= OMe
O
O
O
O
O
O
P
O
62b
62g
63b
63g
Figure 8.11
Phosphine-phosphite
60,
phosphinite-phosphite
61,
and phosphite-
phosphoramidites
62
and
63.
BF
4
/
61e
was used in the hydrogenation of
N-
(phenylethylidene)benzylamine (
5b
)
(Scheme 8.2) the ee was 76% [21].
Among the different mixed ligands, phosphite-phosphoroamidite ligands
62
-
63b,g
(Figure 8.11) - easily prepared in a few steps from commercial d-(
)-xylose
- have been successfully applied in the asymmetric hydrogenation reaction. High
activity and enantioselectivity up to
+
>
99% ee were obtained in asymmetric hydro-
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