Chemistry Reference
In-Depth Information
TABLE 7.12. Asymmetric Hydrogenation of 2 - Alkoxycarbonylcycloalkanones
OH
O
OH
O
O
O
Chiral Ru catalyst
+
OR
OR
OR
H
2
n
n
n
syn
anti
% ee of
the
Anti
Product
(Confi g.)
Reaction
Conditions
Catalyst
n
R
S
/
C
Anti
:
Syn
Reference
Ru[(
R
) - BINAP]
Cl(C
6
H
6
)Cl
1
Me
1170
CH
2
Cl
2
, 50 ° C,
100 atm H
2
99:1
93 (
R,R
)
18d
Ru[(+) - (TetraMe -
BITIANP)]
Cl
2
(DMF)
n
1
Me
1000
MeOH, 70 ° C,
100 atm H
2
93:7
99 (
R,R
)
195b
[Ru(+) - (TetraMe -
BITIOP)
(cymene)I]I
1
Me
1000
MeOH,
CF
3
COOH,
80 ° C, 100 atm H
2
94:6
99 (
S,S
)
196
Ru[(
R
) - C
4
-
TunePhos)]
Cl
2
(DMF)
n
1
Me
200
MeOH, 60 ° C,
750 psi H
2
N/A
96.8 (
R,R
)
23a
Ru[(
R
) - MeO -
BIPHEP)]
Cl
2
(DMF)
n
1
Me
200
MeOH, 60 ° C,
750 psi H
2
N/A
97.5 (
R,R
)
23a
Ru(
89
)Br
2
1
Et
200
CH
2
Cl
2
/EtOH,
50 ° C, 50 atm H
2
99:1
90.9 (
R,R
)
82a
Ru [(
R,R
) -
i
Pr - BPE]
Br
2
1
Me
500
MeOH/H
2
O (9:1),
35 ° C, 60 psi H
2
24:1
98.3 (
S,S
)
28a
Ru[(
R,R
) -
t
BuBisP * ]
Br
2
1
Me
200
MeOH/H
2
O (10:1),
70 ° C, 6 atm H
2
70:13
96
240
Ru[(
R
) - BINAP]
Cl(C
6
H
6
)Cl
2
Et
500
CH
2
Cl
2
, 50 ° C,
100 atm H
2
95 : 5
90 (
R,R
)
257
Ru[(
R
) - BINAP]
Cl(C
6
H
6
)Cl
3
Et
500
CH
2
Cl
2
, 50 ° C,
100 atm H
2
93:7
93 (
R,R
)
257
selectivity for the asymmetric hydrogenation of racemic
- keto esters through
dynamic kinetic resolution, but few ligands provided
anti
- selective hydrogenation. Using
Ru-BINAP complex as catalyst and hydrochloride salt of racemic
α
- amino
β
- keto esters
as substrate, high enantioselectivities and diastereoselectivities were achieved for the
anti -
hydrogenation product (Eq. 7.34). The reverse
syn
/
anti
selectivity was believed
to be attributed to the unprotected amino group, which coordinated with Ru and
served as a stronger directing substituent than the ester group [261]. Excellent dynamic
kinetic resolution was observed for
anti
-selective hydrogenation of racemic
α
- amino
β
α
-
