Chemistry Reference
In-Depth Information
O
O
OH
O
{Ru[(
S
)-BINAP]Cl
2
}(DMF)
n
OMe
OMe
CH
2
Cl
2
, 50°C, 30 atm H
2
S
/
C
=250,92%
NH
2.
HCl
NH
2.
HCl
anti
-, (2
S
,3
S
)-
96% de, 95% ee
(7.34)
PMB
PMB
O
O
O
O
OH
O
Ru[(
S
)-SYNPHOS]Br
2
,100bar
t
BuOH/CH
2
Cl
2
H
2
TBDPSO
TBDPSO
O
t
Bu
O
t
Bu
(4/1), 50
o
C
4
4
80% yield, 97% de
(7.35)
OH
O
O
O
OMe
OMe
[NH
2
Me
2
][{RuCl(
R
-C3-TunePhos)}
2
(
μ
-Cl)
3
]
N
N
O
O
O
O
MeOH, 50
o
C, 100 bar H
2
anti
-, (2
R
,3
R
)-
94% de, >99% ee
(7.36)
7.3.2.1.3. γ - Keto Esters
A few γ-keto esters were also effi ciently hydrogenated
using chiral Ru catalysts featuring atropisomeric ligands although from prolonged reac-
tion time [263]. For example, with an
in situ
- generated Ru - BINAP catalyst from
Ru(BINAP)(OAc)
2
and HCl, a series of chiral lactones were effi ciently synthesized
through asymmetric hydrogenation of 4 - oxo - carboxylates (Eq. 7.37 ). Hydrogenation of
ethyl levulinate was performed with an Ru-(
R
)-SEGPHOS catalyst to give ethyl (
R
) - 4 -
hydroxypentanoate with up to 99% ee [21b].
O
O
H
+
In situ
Ru[(
R
-BINA) ]Cl
2
EtOH, 35
o
C, 100 atm H
2
OC
2
H
5
O
R
O
R
R=CH
3
,C
2
H
5
,
n
-C
8
H
17
,C
6
H
5
(7.37)
7.3.2.1.4. Amino Ketones
Chiral amino alcohols are important building blocks for a
large number of pharmaceutical and natural products [264]. The effi cient preparation of
enantiomerically pure amino alcohols is one of the most challenging tasks in organic
synthesis. Among various synthetic methods, transition metal-catalyzed asymmetric
hydrogenation of the corresponding
-amino ketones represents one of the most effec-
tive and promising approaches [1,18]. Remarkable success has been achieved by Noyori
and others in the hydrogenation of tertiary and protected amino ketones using Ru
catalysts. Particularly, the
trans
- RuCl
2
[(
R
) - XylBINAP][(
R
) - daipen] complex has been
α
