Chemistry Reference
In-Depth Information
1
- BH
4
)
(BINAP)(1,2-diamine) by reducing
trans
- [RuCl
2
(
R
) - Tol - BINAP][(
R
,
R
) - dpen] with
NaBH
4
[296]. This complex avoided the strong basic hydrogenation conditions with the
similar results. A series of heteroaromatic ketones was also hydrogenated with excellent
yields and enantioselectivities using the
trans
- RuCl
2
[(
S
) - XylBINAP][(
S
) - daipen] cata-
lyst [297]. A recent study by Knight and others also revealed that the combination of a
Ru complex of racemic diphosphines and a chiral diamine can also result in
comparable or even superior selectivities [298]. Using
trans
- RuCl
2
[(
S
) - XylBINAP]
[(
S
)-daipen]/base combined catalyst, the asymmetric hydrogenation of aromatic-hetero-
aromatic ketones has been applied for the synthesis of chiral drugs, PDE-IV inhibitor
(Scheme 7.12) [299]. Analogous catalysts with other types of chiral ligands such as BICP
[46f] , Xylyl - PHANEPHOS [59c] , Xyl - P - Phos [300] , Xyl - TetraPHEMP [301] , and SDP
[302] are also effective to a much lesser degree. For example, the Ru complexes of BICP
type of ligands
22
and
23
combined with nonchiral 2-(alkylthio)amine or 1,2-diamine
have shown good performances for the highly enantioselective hydrogenation of aryl
ketones in the presence of alkoxides as the base [276]. A ternary system
consisting of RuCl
2
[(
R
,
R
) - BICP](tmeda), (
R
,
R
) - 1,2 - diphenylethylenediamine, and
KOH catalyzed the hydrogenation of an array of 2-acetylthiophene derivatives with
up to 93% ee [46].
turnover numbers. Noyori and others also reported the synthesis of
trans
- RuH(
η
FH
2
CO
O
FH
2
CO
O
trans
-RuCl
2
[(
R
)-XylBINAP][(
R
)-daipen]
O
iPrOH-THF, rt, 40 psi H
2
K
,
2
CO
3
OH
S
F
3
C
F
3
C
S
S/C
=1000
OMO
OMO
N
N
F
3
C
F
3
C
>99% ee
FH
2
CO
O
S
F
3
C
N
+
O
-
HO
N
F
3
C
FDE-IV inhibtor
Scheme 7.12.
Synthesis of FDE-IV inhibitor via asymmetric hydrogenation.
Zhou and others reported a highly effi cient dynamic kinetic resolution via asymmetric
hydrogenation of aryl aldehyde [304,305]. A series of chiral primary alcohols were pre-
pared in high selectivities using a Ru-SDP catalyst. This method was further demon-
strated in the practical synthesis of a leukotriene receptor antagonists and lipoxygenase
inhibitors BAY X 1005 (Scheme 7.13 ).
