Monophosphite ligands derived from carbohydrates and H8-BINOL: Highly enantioselective Rh-catalyzed asymmetric hydrogenations

Article abstract of DOI:10.1016/j.tetasy.2004.11.087

A series of monophosphite ligands derived from carbohydrates and H ₈-BINOL have been synthesized. Excellent enantioselectivities (over 99% ee) were obtained when these ligands were applied in the Rh-catalyzed asymmetric hydrogenation of dimethy

Full text of DOI:10.1016/j.tetasy.2004.11.087

Tetrahedron:
Asymmetry
Tetrahedron: Asymmetry 16 (2005) 693–697
Monophosphite ligands derived from carbohydrates and
H8-BINOL: highly enantioselective Rh-catalyzed
asymmetric hydrogenations
Hanmin Huang,a Xiongcai Liu,a,b Huilin Chena and Zhuo Zhenga,*
aDalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
bThe Graduate School of Chinese Academy of Sciences, Beijing 100039, China
Received 2 November 2004; accepted 25 November 2004
Abstract—A series of monophosphite ligands derived from carbohydrates and H8-BINOL have been synthesized. Excellent enantio-
selectivities (over 99% ee) were obtained when these ligands were applied in the Rh-catalyzed asymmetric hydrogenation of dimethyl
itaconate and enamides.
Ó 2004 Elsevier Ltd. All rights reserved.
1. Introduction
enantioselectivity. We reasoned that this may attribute
to the additional groups contained in the carbohydrate
backbones to effectively restrain the rotation of M–P
bond by hemilabile coordination4 of the ligand to metal.
In view of these benefits of carbohydrate backbones, as
well as recent successes with H8-BINOL based ligands,5
we decided to design new monophosphites, which incor-
porated these advantageous features. Herein, we report
a new class of monophosphites, based on carbohydrates
with an appropriate configuration and H8-BINOL, as
ligands for the Rh-catalyzed enantioselective hydrogen-
ation of functionalized olefins with excellent
enantioselectivity (Fig. 1).
Catalytic asymmetric hydrogenation is one of the most
useful processes to synthesis of enantiopure compounds,
which has attracted a great deal of attention from both
academia and industry.1 As enantioselectivities and cat-
alytic activities are highly affected by chiral ligands, one
of the challenges in this area is to develop highly enan-
tioselective and inexpensive chiral ligands. In recent
years, some of the monodentate chiral phosphorus
ligands, which are easily prepared and highly enantio-
selective, have attracted much attention. A large variety
of chiral monophosphoramidites, monophosphites and
monophosphinites have been prepared and their appli-
cability in Rh-catalyzed asymmetric hydrogenation
demonstrated.2
2. Results and discussion
Recently, over the course of our studies in the field of
asymmetric synthesis and reactions, we have designed
and synthesized a new class of chiral monophosphite
ligands 1–3 from inexpensive carbohydrates and com-
mercially available BINOL, which have proven to be
excellent ligands in the Rh-catalyzed asymmetric hydro-
genation of functionalized olefins.3 Our previous studies
also demonstrated that the attached carbohydrate back-
bones in these ligands are important for achieving high
2.1. Synthesis of chiral monophosphite ligands
The novel ligands 4–6 were easily prepared by literature
procedures3 with H8-BINOL and the corresponding
monosaccharides with an appropriate configuration.
The RO–PCl2 intermediates were prepared by the reac-
tion of alcohols with PCl3 in the absence of Et3N. These
were then directly reacted with H8-BINOL in the pres-
ence of Et3N to afford the desired product (Scheme 1).
Ligands 4–6 were purified through a short silica gel
plug and were stable in the solid state. Their structures
were fully characterized by 1H, 13C, 31P NMR and
HRMS.
*
Corresponding author. Tel.: +86 411 84669077; fax: +86 411
84684746; e-mail: zhengz@dicp.ac.cn
0957-4166/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2004.11.087

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H. Huang et al. / Tetrahedron: Asymmetry 16 (2005) 693–697
R
O
Ph
O
R
O
R
O
R
O
O
O
OR
O
O
O
O
O
O
O
R
O
O
O
P
O
P
P
R
O
R
O
Ph
O
O
O
R
R
2
1
3
O
Ph
Ph
O
R
R
R
O
OR
O
O
O
O
O
O
O
O
O
O
O
O
O
P
O
P
O
O
P
R
O
O
R
O
O
R
R
5a: R= CH3
5b: R= -(CH2)5-
4a: R= CH3
4b: R= -(CH2)5-
6a: R= CH3
6b: R= CH2Ph
Figure 1. Monophosphite ligands derived from carbohydrates.
R
R
O
R
O
O
Ph
Ph
O
O
R
O
O
O
OR
OH
(1) PCl3, THF
(2) Et3N,
O
O
OH or
or
O
O
HO
O
R
O
O
R
O
R
R
R
9a-b
8a-b
7a-b
R
O
R
O
O
Ph
Ph
O
R
O
O
O
OR
O
O
O
O
O
O
O
P
or
O
O
or
P
O
R
O
P
O
O
R
O
R
4
O
O
R
5
6
Scheme 1. The synthesis of the monophosphite ligands.
2.2. Asymmetric hydrogenation of enamides
monophosphite 4a has the highest capability of asym-
metric induction among 4–6 (Table 1, entry 1).
The performance of ligands 4–6 was thoroughly explored
in the Rh-catalyzed enantioselective hydrogen-
ation of enamides. In the first set of experiments, we
chose N-(1-phenylethenyl)acetamide 10a as a model sub-
strate for testing the catalytic performance of the catalyst
precursors containing with ligands 4–6. The catalyst was
prepared in situ by mixing [Rh(COD)2]BF4 and the
monophosphite ligand under an inert atmosphere. All
the hydrogenation reactions were typically carried out
at room temperature under 10 atm pressure of H2 and
with a substrate, Rh and ligand ratio of 1.0/0.01/0.022.
Although a standard reaction time of 12 h was chosen,
most of the reactions were complete within 3 h. Entries
1–6 in Table 1 summarize the results of the asymmetric
hydrogenation when employing our new ligands. The
reaction was carried out in CH2Cl2 with full conversion
and excellent enantioselectivities (96.4–99.0% ee) when
monophosphites 4–6 were used as ligands. The results
also demonstrated that the capability of asymmetric
induction of these ligands was again sensitive to the
carbohydrate moiety and that the D-fructose derived
With the best ligand 4a, we examined the Rh-catalyzed
enantioselective hydrogenation of a variety of enamides
under the optimal condition. In all cases, ligands 4a
exhibited excellent enantioselectivities (97.3–99.6% ee).
The electronic nature of the para-substituents in a-aryl-
enamides appeared to affect the enantioselectivity
observed. Hydrogenation of a-arylenamides with
electron-withdrawing substituents (Table 1, entries 7–
9) on the phenyl ring gave higher enantioselectivities
than those with electron-donating substituents (entry
10). Hydrogenation of 2-naphthyl derivative also gave
an excellent ee value (Table 1, entry 12). b-Substituted
isomeric mixtures of (E/Z) arylenamides were also re-
duced with excellent enantioselectivities (entries 13 and
14), regardless of the various b-substituents. It is notable
that the ee values obtained by the H8-BINOL derived
ligands 4a are higher than those obtained with the
BINOL derived parent ligands.3 This might be attrib-
uted to the larger torsion dihedral angle in H8-BINOL
derived ligands.5a

H. Huang et al. / Tetrahedron: Asymmetry 16 (2005) 693–697
695
Table 1. Rh-catalyzed asymmetric hydrogenation of enamides 10a
2, entry 1). These observations further demonstrate that
carbohydrate backbones are important to these
catalysts.
R2
R1
R2
R1
[Rh(COD)2]BF4 + L*
NHAc
11a-i
NHAc
10a-i
H2, CH2Cl2
3. Conclusions
Entry
Ligand
Substrate (R1, R2)
Ee% (config)b
1
4a
4b
5a
5b
6a
6b
4a
4a
4a
4a
4a
4a
4a
4a
10a (Ph, H)
10a (Ph, H)
99.0 (S)
98.6 (S)
97.3 (S)
96.4 (S)
97.1 (S)
98.5 (S)
99.3 (S)
99.6 (S)
99.5 (S)
98.9 (S)
99.3 (S)
99.5 (S)
97.3 (S)
99.0 (S)
In summary, a new class of monophosphite ligands 4–6
derived from carbohydrates and H8-BINOL has been
designed and synthesized. Excellent ee values were ob-
tained in the Rh-catalyzed asymmetric hydrogenation
of enamides and dimethyl itaconate. In contrast to the
other H8-BINOL derived monodentate ligands,2f,l,m
the ligands reported here are more efficient in the Rh-
catalyzed asymmetric hydrogenations. This may be
attributed to the function of the carbohydrate back-
bones attached in these ligands. The design and synthe-
sis of more effective chiral monophosphorus ligands
from carbohydrates and their applications in asymmet-
ric catalytic hydrogenation are currently in progress.
2
3
10a (Ph, H)
10a (Ph, H)
4
5
10a (Ph, H)
10a (Ph, H)
6
7
10b (p-FC6H4, H)
10c (p-BrC6H4, H)
10d (p-ClC6H4, H)
10e (p-CH3OC6H4, H)
10f (p-CF3C6H4, H)
10g (2-Naphthyl, H)
10h (Ph, Me)
8
9
10
11
12
13c
14d
10i (Ph, Et)
a Solvent: CH2Cl2; p(H2) = 10 atm; T = 20 °C; reaction time: 12 h;
substrate:[Rh(COD)2]BF4:L = 1:0.01:0.022; 100% conversion was
obtained in all cases.
b Determined by chiral capillary GC on a Varian Chirasil-L-Val col-
umn and a Supelco Chiral select 1000 column. The absolute config-
uration was assigned by comparison of the specific rotation with
reported data.
c E/Z = 67/33.
d E/Z = 40/60.
4. Experimental
4.1. General methods
All reactions were carried out under a N2 atmosphere.
Melting points were measured on a Metter FP5 melting
apparatus and are uncorrected. NMR spectra were mea-
sured on a Bruker DRX-400 NMR spectrometer. Opti-
cal rotations were measured with a JASCO P-1020
automatic polarimeter. High resolution mass spectra
were recorded on Applied Biosystems Mariner System
5303. Enantiomeric excess (ee) determination was car-
ried out using GC with a Supelco Chiral Select 1000, a
CP-chiralsil-L-Val capillary column and a c-DEX 225
chiral capillary column on an Agilent HP-4890 GC
instrument with FID as detector. All solvents were dried
and degassed by standard methods. 1,2:4,5-Di-O-isopro-
pylidene-b-D-fructopyranose 7a, 1,2:4,5-di-O-cyclohexyl-
idene-b-D-fructopyranose 7b, 1,2:5,6-di-O-isopropylid-
ene-D-glucose 8a, 1,2:4,5-di-O-cyclohexylidene-D-glu-
cose 8b, 1,3:4,6-di-O-benzyllidene–2–O-methyl-D-man-
nitol 9a, 1,3:4,6-di-O-benzyllidene–2–O-benzyl-D-man-
nitol 9b and (R)-2,20–dihydroxy-5,50,6,60,7,70,8,80-octa-
hydro-1,10-binaphthyl were prepared according to
the literature procedures.3,6 Enamides were synthesized
by using procedures describe elsewhere.7 All other chem-
icals were obtained commercially.
2.3. Asymmetric hydrogenation of dimethyl itaconate
Dimethyl itaconate was also hydrogenated with these
catalysts. As shown in Table 2, these monophosphites,
which we prepared, are efficient ligands for the asym-
metric hydrogenation reaction, with good to excellent
ee values (up to 99.5% ee) and full conversions being ob-
served in the hydrogenation of this substrate. However,
the enantioselectivities also proved to be influenced by
the structure of the carbohydrate backbones contained
in these ligands. The results in Table 2 show that the
D-fructose derived monophosphite 4a is the most effec-
tive ligand, which gave the best ee value 99.5% (Table
Table 2. Rh-catalyzed asymmetric hydrogenation of dimethyl itaco-
nate 12a
[Rh(COD)2]BF4 + L*
CO2Me
CO2Me
MeO2C
MeO2C
H2, CH2Cl2
12
13
4.2. General procedures for the synthesis of monopho-
sphite ligands 4–6
Entry
Ligand
Ee% (Config)b
1
2
3
4
5
6
4a
4b
5a
5b
6a
6b
99.5 (R)
96.3 (R)
95.6 (R)
95.0 (R)
97.0 (R)
96.1 (R)
To a stirred solution of 7, 8 or 9 (2.5 mmol) in THF
(5 mL) was slowly added PCl3 (218 lL, 2.5 mmol) as a
solution in THF (4 mL) at 0 °C and the resulting mix-
ture stirred for 1 h at room temperature. The reaction
mixture was then cooled to ꢀ10 °C and Et3N
(1.07 mL, 7.6 mmol) slowly added. The reaction mixture
was allowed to warm to room temperature, maintained
under these conditions for 0.25 h and then cooled to
0 °C, solid H8-BINOL was added and the resulting mix-
ture allowed to warm to room temperature and stirred
a Solvent: CH2Cl2; p(H2) = 10 atm; T = 20 °C; reaction time: 12 h;
substrate:[Rh(COD)2]BF4:L = 1:0.01:0.022; 100% conversion was
obtained in all cases.
b Determined by chiral capillary GC on a c-DEX 225 column. The
absolute configuration was assigned by comparison of the optical
rotation with reported data.

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H. Huang et al. / Tetrahedron: Asymmetry 16 (2005) 693–697
overnight prior to dilution with diethyl ether. The solids
were removed by filtration through a pad of Celite, the
solvent removed in vacuo and the residue purified by
flash chromatography (EtOAc–hexane, 1:20 ꢁ 1:10),
furnished the title ligands as a white foam in 75–85%
yield.
4.2.4. 1,2:5,6-Di-O-cyclohexylidene-3-O-((R)-2,20-O,O-
(5,50,6,60,7,70,8,80-octahydro-1,10-binaphthyl)dioxophos-
phite)-D-glucose, 5b. The above procedure was fol-
lowed using 8b and (R)-H8-BINOL. After work-up, it
10
gave 5b. Mp 106–107 °C; ½aꢂ ¼ ꢀ139:4 (c 0.90, THF);
D
1H NMR (DMSO-d6): d 1.33–1.70 (m, 28H), 2.21–2.25
(m, 2H), 2.67–2.73 (m, 2H), 2.87 (d, J = 5.2 Hz, 4H),
3.80 (dd, J = 8.4, 5.6 Hz, 1H), 4.04–4.17 (m, 3H),
4.77–4.79 (m, 2H), 5.95 (d, J = 3.6 Hz, 1H), 7.03 (d,
J = 8.0 Hz, 1H), 7.11 (d, J = 8.0 Hz, 1H), 7.20 (dd,
J = 13.8, 8.2 Hz, 2H); 13C NMR (DMSO-d6): d 21.98,
23.24, 23.59, 24.33, 24.65, 27.23, 28.43, 34.45, 35.17,
36.00, 66.29, 71.43, 77.31,77.52, 80.40, 83.29, 104.33,
108.94, 112.01, 118.61, 118.85, 127.06, 128.70, 129.26,
129.57, 133.70, 134.77, 137.00, 137.99, 145.47; 31P
NMR (DMSO-d6): d 144.10; HRMS (APCI) calcd for
C38H48O8P (M+1): 663.3081, found: 663.3074.
4.2.1.
1,2:4,5-Di-O-isopropylidene-3-O-((R)-2,20-O,O-
(5,50,6,60,7,70,8,80-octahydro-1,10-binaphthyl)dioxophos-
phite)-D-fructose, 4a. The above procedure was follo-
wed using 7a and (R)-H8-BINOL. After work-up, it gave
10
1
4a. Mp 113–114 °C; ½aꢂ ¼ ꢀ184:5 (c 0.93, THF); H
D
NMR (DMSO-d6): d 1.29–1.40 (m, 14H), 1.73 (d,
J = 3.6 Hz, 6H), 2.12–2.16 (m, 2H), 2.62 (d,
J = 6.8 Hz, 2H), 2.79 (d, J = 2.0 Hz, 4H), 3.53 (d, J =
10.8 Hz, 1H), 3.66 (d, J = 9.2 Hz, 1H), 3.80 (d,
J = 12.4 Hz, 1H), 4.05 (d, J = 9.2 Hz, 1H), 4.36 (d,
J = 8.0 Hz, 1H), 4.59 (dd, J = 7.8, 1.8 Hz, 1H), 4.75
(dd, J = 10.6, 1.8 Hz, 1H), 6.93 (d, J = 8.0 Hz, 2H),
7.01 (dd, J = 15.6, 8.0 Hz, 2H); 13C NMR (DMSO-d6):
d 21.96, 24.59, 25.88, 26.10, 26.18, 27.22, 27.30, 28.44,
62.55, 70.54, 70.68, 73.41, 73.80, 104.74, 108.62,
108.94, 118.69, 118.95, 129.11, 129.60, 133.69, 133.99;
31P NMR (DMSO-d6): d 145.60; HRMS (APCI) calcd
for C32H40O8P (M+1): 583.2455, found: 583.2505.
4.2.5.
1,3:4,6-Di-O-benzyllidene-2-O-methyl-5-O-((R)-
2,20-O,O-(5,50,6,60,7,70,8,80-octahydro-1,10-binaphthyl)-
dioxophosphite)-D-mannitol, 6a. The above procedure
was followed using 9a and (R)-H8-BINOL. After
10
D
work-up, it gave 6a. Mp 133–134 °C; ½aꢂ ¼ ꢀ156:5
(c 0.87, THF); 1H NMR (DMSO-d6): d 1.50–1.75
(m, 8H), 2.11–2.81 (m, 4H), 3.42 (s, 3H), 3.61–3.92
(m, 4H), 4.12–4.59 (m, 4H), 5.51 (s, 1H), 5.77 (s,
1H), 6.96–7.48 (m, 14H); 13C NMR (DMSO-d6):
d 21.98, 22.08, 27.25, 28.43, 28.51, 58.18, 62.52, 62.72,
68.23, 68.37, 68.81, 76.26, 76.55, 99.96, 118.84, 119.03,
125.90, 127.32, 128.08, 128.19, 128.71, 128.82, 129.27,
129.56, 133. 79, 134.83, 137.00, 137.47, 137.65, 138.01,
144.97, 145.39; 31P NMR (DMSO-d6): d 145.42; HRMS
(APCI) calcd for C41H44O8P (M+1): 695.2768, found:
695.2740.
4.2.2. 1,2:4,5-Di-O-cyclohexylidene-3-O-((R)-2,20-O,O-
(5,50,6,60,7,70,8,80-octahydro-1,10-binaphthyl)dioxophos-
phite)-D-fructose, 4b. The above procedure was fol-
lowed using 7b and (R)-H8-BINOL. After work-up, it
10
gave 4b. Mp 62–63 °C; ½aꢂ ¼ ꢀ162:4 (c 0.91, THF);
D
1H NMR (DMSO-d6): d 1.34-1.82 (m, 28H), 2.22 (d,
J = 16.0 Hz, 2H), 2.71 (d, J = 11.6 Hz, 2H), 2.86–2.92
(m, 4H), 3.63 (d, J = 13.2 Hz, 1H), 3.77 (d, J = 8.8 Hz,
1H), 3.91 (d, J = 12.8 Hz, 1H), 4.17 (d, J = 8.8 Hz,
1H), 4.46 (d, J = 7.6 Hz, 1H), 4.69 (d, J = 7.6 Hz, 1H),
4.88 (d, J = 10.4 Hz, 1H), 6.99 (dd, J = 16.6, 8.0 Hz,
2H), 7.15 (d, J = 8.0 Hz, 1H), 7.22 (d, J = 8.0 Hz, 1H);
13C NMR (DMSO-d6): d 21.93, 22.06, 23.19, 23.34,
23.52, 24.58, 27.24, 28.49, 33.75, 35.15, 35.34, 35.53,
62.64, 70.09, 70.68, 70.88, 73.12, 73.56, 104.20, 109.18,
109.55, 118.62, 118.98, 118.98, 127.33, 128.74, 128.95,
129.56, 133.69, 134.80, 136.93, 137.99, 145.16, 145.42;
31P NMR (DMSO-d6): d 146.01; HRMS (APCI) calcd
for C38H48O8P (M+1): 663.3081, found: 663.3033.
4.2.6.
1,3:4,6-Di-O-benzyllidene-2-O-benzyl-5-O-((R)-
2,20-O,O-(5,50,6,60,7,70,8,80-octahydro-1,10-binaphthyl)di-
oxophosphite)-D-mannitol, 6b. The above procedure
was followed using 9b and (R)-H8-BINOL. After
10
D
work-up, it gave 6b. Mp 125–126 °C; ½aꢂ ¼ ꢀ148:9 (c
0.76, THF); 1H NMR (DMSO-d6): d 1.55–2.24 (m,
11H), 2.68–2.88 (m, 6H), 3.74–3.77 (m, 1H), 3.86–3.87
(m, 1H), 3.96–3.98 (m, 2H), 4.21–4.24 (m, 1H), 4.52–
4.57 (m, 2H), 4.64–4.73 (m, 3H), 5.60 (s, 1H), 5.74 (s,
1H), 7.02–7.53 (m, 20H); 13C NMR (DMSO-d6): d
21.95, 27.22, 28.48, 62.50, 62.69, 65.73, 68.60, 68.73,
71.25, 76.15, 76.42, 99.95, 118.84, 119.00, 125.86,
125.96, 127.28, 127.73, 127.83, 128.06, 128.28, 128.70,
129.26, 129.54, 133.76, 134.81, 136.98, 137.35, 137.59,
138.00, 144.92, 145.37; 31P NMR (DMSO-d6): d
145.46; HRMS (APCI) calcd for C47H48O8P (M+1):
771.3081, found: 771.3132.
4.2.3.
1,2:5,6-Di-O-isopropylidene-3-O-((R)-2,20-O,O-
(5,50,6,60,7,70,8,80-octahydro-1,10-binaphthyl)dioxophos-
phite)-D-glucose, 5a. The above procedure was follo-
wed using 8a and (R)-H8-BINOL. After work-up, it gave
10
1
5a. Mp 108–109 °C; ½aꢂ ¼ ꢀ168:6 (c 0.90, THF); H
D
NMR (DMSO-d6): d 1.30–1.72 (m, 20H), 2.12 (d,
J = 16.0 Hz, 2H), 2.60 (s, 2H), 2.78 (s, 4H), 3.71–
3.75 (m, 1H), 3.93–3.97 (m, 1H), 4.01–4.03 (m,
1H), 4.08–4.12 (m, 1H), 4.63–4.71 (m, 2H), 5.86–5.87
(d, J = 3.2 Hz, 1H), 6.98–7.05 (m, 2H), 7.11–7.15 (m,
2H); 13C NMR (DMSO-d6): d 21.88, 21.98, 25.29,
26.12, 26.57, 27.23, 28.43, 66.35, 71.72, 77.18, 77.36,
80.19, 83.70, 104.57, 108.46, 111.51, 118.77, 118.83,
126.97, 128.66, 129.26, 129.57, 133.70, 134.78, 136.97,
137.97, 145.45; 31P NMR (DMSO-d6): d 142.17; HRMS
(APCI) calcd for C32H40O8P (M+1): 583.2455, found:
583.2475.
4.3. General procedures for asymmetric hydrogenation
In a nitrogen-filled glove box, to a solution of
[Rh(COD)2]BF4 (2.0 mg, 0.005 mmol) in anhydrous
and degassed CH2Cl2 (1 mL) was added the ligand
(0.011 mmol). After stirring the mixture for 30 min, a
substrate (0.5 mmol) dissolved in CH2Cl2 (1 mL) was
added. The reaction mixture was then transferred to
an autoclave. The autoclave was purged three times with
hydrogen and the pressure set to the desired pressure;

H. Huang et al. / Tetrahedron: Asymmetry 16 (2005) 693–697
697
2002, 13, 115; (n) van den Berg, M.; Haak, R. M.;
Minnaard, A. J.; de Vries, A. H. M.; de Vries, J. G.;
Feringa, B. L. Adv. Synth. Catal. 2002, 344, 1003;
(o) Claver, C.; Fernandez, E.; Gillon, A.; Heslop, K.;
Hyett, D. J.; Martorell, A.; Orpen, A. G.; Pringle, P. G.
Chem. Commun. 2000, 961; (p) Reetz, M. T.; Mehler, G.
Angew. Chem., Int. Ed. 2000, 39, 3889; (q) van den Berg,
M.; Minnaard, A. J.; Schudde, E. P.; van Esch, J.; de Vries,
J. G.; Feringa, B. L. J. Am. Chem. Soc. 2000, 122,
11539.
hydrogenation was performed at room temperature for
12 h. After carefully releasing the hydrogen, the reaction
mixture was passed through a short silica gel plug to re-
move the catalyst. The resulting solution was directly
used for chiral GC to determine enantiomeric excesses.
Acknowledgements
Financial support from the National Science Founda-
tion of China (29933050, 20472083) is gratefully
acknowledged.
3. (a) Huang, H.; Liu, X.; Chen, S.; Chen, H.; Zheng, Z.
Tetrahedron: Asymmetry 2004, 15, 2011; (b) Huang, H.;
Zheng, Z.; Luo, H.; Bai, C.; Hu, X.; Chen, H. J. Org. Chem.
2004, 69, 2355; (c) Huang, H.; Zheng, Z.; Luo, H.; Bai, C.;
Hu, X.; Chen, H. Org. Lett. 2003, 2, 4137.
References
4. For review of hemilabile ligands, see: Bader, A.; Lindler, E.
Coord. Chem. Rev. 1991, 108, 27.
1. For recent reviews, see (a) Tang, W.; Zhang, X. Chem. Rev.
2003, 103, 3029; (b) Ohkuma, T.; Kitamura, M.; Noyori,
R. In Catalytic Asymmetric Synthesis; Ojima, I., Ed., 2nd
ed.; Wiley-VCH: Weinheim, 2000, p 1; (c) Brown, J. M. In
Comprehensive Asymmetric Catalysis; Jacobsen, E. N.,
Pfaltz, A., Yamamoto, H., Eds.; Springer: Berlin, 1999; p
121.
5. (a) For a recent review, see Au-Yeung, T. T.-L.; Chan
S.-S.; Chan, A. S. C. Adv. Synth. Catal. 2003, 345, 537; (b)
Gergely, I.; Hegedus, C.; Gulyas, H.; Szollosy, A.; Mon-
sees, A.; Riemeier, T.; Bakos, J. Tetrahedron: Asymmetry
2003, 14, 1087; (c) Wang, B.; Feng, X.; Huang, Y.; Liu, H.;
Cui, X.; Jiang, Y. J. Org. Chem. 2002, 67, 2175; (d) Long,
J.; Hu, J.; Shen, X.; Ji, B.; Ding, K. J. Am. Chem. Soc. 2002,
124, 10; (e) Matsunaga, S.; Das, J.; Roels, J.; Vogl, E. M.;
Yamamoto, N.; Iida, T.; Yamaguchi, K.; Shibasaki, M. J.
Am. Chem. Soc. 2000, 122, 2252; (f) Uemura, T.; Zhang, X.;
Matsumura, K.; Sayo, N.; Kumobashi, H.; Ohta, T.;
Nozaki, K.; Takaya, H. J. Org. Chem. 1996, 61, 5510; (g)
Xiao, J.; Nefkens, S. C. A.; Jessop, P. G.; Ikariya, T.;
Noyori, R. Tetrahedron Lett. 1996, 37, 2813; (h) Zhang, X.;
Mashima, K.; Koyano, K.; Sayo, N.; Kumobayashi, H.;
Akutagawa, S.; Takaya, H. J. Chem. Soc., Perkin Trans. 1
1994, 2309; (i) Zhang, X.; Uemura, T.; Matsumura, K.;
Sayo, N.; Kumobayashi, H.; Takaya, H. Synlett 1994, 501;
(j) Zhang, X.; Kumobayashi, H.; Takaya, H. Tetrahedron:
Asymmetry 1994, 5, 1179; (k) Zhang, X.; Taketomi, T.;
Yoshizumi, T.; Kumobayashi, H.; Akutagawa, S.; Mush-
ima, K.; Takaya, H. J. Am. Chem. Soc. 1993, 115, 3318;
2. (a) Reetz, M. T.; Sell, T.; Meiswinkel, A.; Mehler, G.
Angew. Chem., Int. Ed. 2003, 42, 790; (b) Pena, D.;
Minnaard, A. J.; de Vries, A. H. M.; de Vries, J. G.;
Feringa, B. L. Org. Lett. 2003, 5, 475; (c) Reetz, M. T.;
Goossen, L. J.; Meiswinkel, A.; Paetzold, J.; Jensen, J. F.
Org. Lett. 2003, 5, 3099; (d) Jia, X.; Li, X.; Xu, Li.; Shi, Q.;
Yao, X.; Chan, A. S. C. J. Org. Chem. 2003, 68, 4539; (e)
Hannen, P.; Militzer, H.-C.; Vogl, E. M.; Rampf, F. A.
Chem. Commun. 2003, 2210; (f) Li, X.; Jia, X.; Lu, G.; Au-
Yeung, T. T.-L.; Lam, K.-H.; Lo, T. W. H.; Chan, A. S. C.
Tetrahedron: Asymmetry 2003, 14, 2687; (g) Hu, A.-G.; Fu,
Y.; Xie, J.-H.; Zhou, H.; Wang, L.-X.; Zhou, Q.-L. Angew.
Chem., Int. Ed. 2002, 41, 2348; (h) Pena, D. M.; Minnaard,
A. J.; de Vries, J. G.; Feringa, B. L. J. Am. Chem. Soc.
2002, 124, 14552; (i) Fu, Y.; Xie, J.-H.; Hu, A.-G.; Zhou,
H.; Wang, L.-X.; Zhou, Q.-L. Chem. Commun. 2002, 480;
(j) Reetz, M. T.; Mehler, G.; Meiswinkel, A.; Sell, T.
Tetrahedron Lett. 2002, 43, 7941; (k) Junge, K.; Oehme, G.;
Monsees, A.; Riermeier, T.; Dingerdissen, U.; Beller, M.
Tetrahedron Lett. 2002, 43, 4977; (l) Jia, X.; Guo, R.; Li, X.;
Yao, X.; Chan, A. S. C. Tetrahedron Lett. 2002, 43, 5541;
(m) Zeng, Q.; Liu, H.; Cui, X.; Mi, A.; Jiang, Y.; Li, X.;
Choi, M. C. K.; Chan, A. S. C. Tetrahedron: Asymmetry
´
For carbohydrates-derived chiral ligands, see (l) Dieguez,
M.; Pamies, O.; Claver, C. Chem. Rev. 2004, 104, 3189.
`
6. Cram, D. J.; Helgeson, R. C.; Peacock, S. C.; Kaplan, L. J.;
Domeier, L. A.; Moreau, P.; Kaga, k.; Mayer, J. M.; Chao,
Y.; Siegel, M.; Hoffman, D. H.; Sogah, G. D. Y. J. Org.
Chem. 1978, 43, 1930.
7. Burk, M. J.; Casy, G.; Johnson, N. B. J. Org. Chem. 1998,
63, 6084.