Asymmetric hydrogenation of aromatic ketones using polymeric catalyst prepared from polymer-supported 1,2-diamine

Article abstract of DOI:10.1016/j.jorganchem.2006.03.050

tert-Butyloxycarbonyl (Boc) protected chiral 1,2-diamine monomers 3 were copolymerized with achiral vinyl monomers such as styrene, methacrylates, acrylates, methacrylamide, and acrylamide to give crosslinked polymers P2 containing chiral 1,2-diamine moie

Full text of DOI:10.1016/j.jorganchem.2006.03.050

Journal of Organometallic Chemistry 692 (2007) 487–494
www.elsevier.com/locate/jorganchem
Asymmetric hydrogenation of aromatic ketones using
polymeric catalyst prepared from polymer-supported 1,2-diamine
*
Shinichi Itsuno , Masahiro Chiba, Miyuki Takahashi, Yukihiro Arakawa, Naoki Haraguchi
Department of Materials Science, Toyohashi University of Technology, Tempaku-cho, Toyohashi 441-8580, Japan
Received 22 February 2006; received in revised form 16 March 2006; accepted 22 March 2006
Available online 1 September 2006
Abstract
tert-Butyloxycarbonyl (Boc) protected chiral 1,2-diamine monomers 3 were copolymerized with achiral vinyl monomers such as
styrene, methacrylates, acrylates, methacrylamide, and acrylamide to give crosslinked polymers P2 containing chiral 1,2-diamine
moieties. Deprotection of the Boc groups in the polymer afforded the crosslinked chiral 1,2-diamine polymer P3. The diamine polymer
was allowed to react with RuCl2/BINAP in DMF to form polymeric complex. Asymmetric hydrogenation of aromatic ketones smoothly
proceeded using the polymeric complex to give the corresponding secondary alcohol in quantitative yield with high level of enantiose-
lectivity up to 98% ee in a mixed solvent of DMF and 2-propanol. The polymeric catalyst can be recycled several times without loss of the
activity.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Asymmetric hydrogenation; Chiral 1,2-diamine; Polymer-support; Ketone; Methacrylate
1. Introduction
On the other hands, from a viewpoint of efficiency in
organic synthesis polymer-supported catalysts are extre-
mely useful for enantioselective reaction mainly due to
their easy separation from the reaction mixture. A consid-
erable number of papers on the immobilization of chiral
compound to polymer have been reported [12]. Polymer-
supported chiral compounds can be used as chiral auxil-
iary, reagent, or ligands for asymmetric catalyst. However
study on the immobilization of enantiopure 1,2-diphenyle-
thylenediamine is quite limited. Some unique method
should be required in order that the immobilization may
maintain primary amino groups in the 1,2-diamine struc-
ture. We have designed and synthesized enantiomerically
pure 1,2-diamine monomer 3 having 1,2-diphenylethylen-
ediamine structure. Vinylphenyl group in the chiral
monomer can be easily polymerized under radical polymer-
ization condition to give the polymer-supported chiral 1,2-
dimaine P3 after deprotection of Boc group in P2, which
can be utilized as chiral ligand for asymmetric catalyst in
the above reactions. We have chosen enantioselective
hydrogenation of unfunctionalized ketones as one of the
most important application of chiral 1,2-diamine as a
Chiral, enantiomerically pure 1,2-diamines and their
derivatives are currently used increasingly in asymmetric
synthesis [1]. Of chiral 1,2-diamines the most frequently
used enantiopure ones are 1,2-diphenylethylenediamine
(DPEN) and 1,2-diaminocyclohexane. These chiral 1,2-
diamines having C2-symmetry offer especially great prom-
ise as stereoselective reagents and catalysts for asymmetric
synthesis. Many examples of chiral catalyst systems con-
taining these 1,2-diamines involve those used for hydroge-
nation [2], epoxidation [3], Diels–Alder reactions [4], aldol
reactions [5], dihydroxylations of olefins [6], nucleophilic
additions of carbonyls [7], conjugate additions [8], proton-
ation of enolates [9], cyclopropanations [10], and aziridina-
tions [11]. The chiral catalysts derived from the
1,2-diamines showed excellent activity with high level of
asymmetric induction in various kinds of asymmetric
transformations including above mentioned reactions.
*
Corresponding author.
E-mail address: itsuno@tutms.tut.ac.jp (S. Itsuno).
0022-328X/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.03.050

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S. Itsuno et al. / Journal of Organometallic Chemistry 692 (2007) 487–494
ligand of the catalyst. Chiral free diamine is necessary to
prepare efficient catalyst for this reaction. Thus, the chiral
catalyst prepared from a combination of enantiopure 1,2-
diamine, RuCl2, and BINAP [13] shows powerful catalytic
activity in the asymmetric hydrogenation of ketones [2].
Previously we have reported that styrene based polymer-
supported 1,2-diamine P1 performed as a polymeric chiral
ligand of the catalyst for asymmetric hydrogenation of
ketones [14,15]. In order to investigate the polymer effect
on the enantioselective reaction we have prepared various
kinds of polymers containing the chiral 1,2-diamine struc-
ture. In this paper we have copolymerized the chiral mono-
mer 3 with various achiral vinyl monomers to give
crosslinked chiral 1,2-diamine polymers P3, which have
been applied to the preparation of the catalyst for the
asymmetric hydrogenation of aromatic ketones.
80 lmol). The ampoule was sealed after three cycles of
freeze–thaw under liquid nitrogen. Copolymerization was
carried out at 70 ꢁC. After 5 min stirring, viscosity of the
solution increased and gel was formed within 15 min. The
whole mixture was continued to be heated at the same tem-
perature for 24 h. The ampoule was opened and the result-
ing mixture was poured into methanol. The obtained
polymer P2a was washed with THF and methanol and
dried in vacuo.
The above polymer having Boc-NH groups was then
transferred to a flask containing 15 mL of 4 N HCl/THF
solution at room temperature and stirred for 5 h. The insol-
uble polymer was filtered and washed with THF, water and
THF again. The chiral 1,2-diamine hydrochloride polymer
was then treated with THF (20 mL)/triethylamine (20 mL)
mixture at room temperature for 12 h. The polymer P3a
was collected on a glass filter and washed with THF, water,
methanol and dried in vacuo at 40 ꢁC for 20 h. Free
primary amino groups on the polymer were detected by a
bromophenol blue test of the polymer [16].
2. Experimental
2.1. Materials
All reactions were carried out under an atmosphere of
dry nitrogen. N,N-Dimethylformamide (DMF) was freshly
distilled from calcium hydride under reduced pressure. All
ketones used were distilled from calcium hydride under
argon. Reactions were monitored by TLC using Merck
Precoated silica-gel plates (Merck 5554, 60F254). Column
chromatography was performed with a silica gel column
(Wakogel C-200, 100–200 mesh).
2.3.1. Copolymerization of 3a with methyl methacrylate
(MMA) followed by deprotection
The desired polymer-supported 1,2-diamine P3aMMA
was isolated in 91% yield. IR (KBr): 3530, 2994, 2950,
1727, 1516, 1146 cmꢀ1. Anal. Calc. for (C5H8O2)0.95
-
(C32H32N2O2)0.05: C 64.12, H 7.80, N 1.18. Found: C
64.37, H 7.89, N 1.16%.
2.3.2. Copolymerization of 3a with 2-hydroxyethyl
methacrylate (HEMA) followed by deprotection
2.2. Measurements
The desired polymer-supported 1,2-diamine P3aHEMA
was isolated in 95% yield. IR (KBr): 3500, 2950, 1728,
1H NMR (300 MHz) spectra were recorded on Varian
Mercury 300 spectrometer using tetramethylsilane as an
internal standard, and J values are recorded in hertz. 13C
NMR (100 MHz) and 31P NMR (162 MHz) spectra were
recorded on a Varian Inova 400 spectrometer. IR spectra
were recorded with a JEOL JIR-7000 FT-IR spectrometer
and are reported in reciprocal centimeter (cmꢀ1). Elemental
analyses were performed at the Microanalytical Center of
Kyoto University. HPLC analyses were performed with a
JASCO HPLC system composed of 3-line degasser DG-
980-50, HPLC pump PV 980, column oven CO-965,
equipped with a chiral column (CHIRALCEL OD, Daicel)
using hexane/2-propanol as an eluent. A UV detector
(JASCO UV-975) was used for the peak detection. GC
analyses of reaction conversion were performed with a
Shimadzu Capillary Gas Chromatograph 14A equipped
with a capillary column (Astec Chiraldex G-TA, 30 m ·
0.25 mm).
1518, 1458, 1276, 1157 cmꢀ1
.
Anal. Calc. for
(C6H10O3)0.95(C32H32N2O2)0.05: C 59.46, H 7.59, N 0.95.
Found: C 60.01, H 7.55, N 0.98%.
2.3.3. Copolymerization of 3a with isopropyl methacrylate
(PMA) followed by deprotection
The desired polymer-supported 1,2-diamine P3aPMA
was isolated in 99% yield. IR (KBr): 3535, 2992, 2950,
1727, 1515, 1146 cmꢀ1. Anal. Calc. for (C7H12O2)0.95
-
(C32H32N2O2)0.05: C 68.06, H 9.00, N 0.96. Found: C
68.12, H 8.98, N 1.01%.
2.3.4. Copolymerization of 3a with butyl methacrylate
(BMA) followed by deprotection
The desired polymer-supported 1,2-diamine P3aBMA
was isolated in 93% yield. IR (KBr): 3530, 2994, 2950,
1727, 1516, 1146 cmꢀ1. Anal. Calc. for (C8H14O2)0.95
-
(C32H32N2O2)0.05: C 69.53, H 9.45, N 0.88. Found: C
69.66, H 9.50, N 0.85%.
2.3. General procedure for copolymerization of chiral
1,2-diamine monomer 3 with achiral monomer
2.3.5. Copolymerization of 3a with methyl acrylate (MA)
followed by deprotection
The desired polymer-supported 1,2-diamine P3aMA
was isolated in 76% yield. IR (KBr): 3448, 2952, 1736,
A 20 mL glass ampoule equipped with magnetic stirring
bar was charged with DMF (2.0 mL), 3 (0.295 mmol) [14],
achiral monomer (5.60 mmol), and AIBN (13 mg,

S. Itsuno et al. / Journal of Organometallic Chemistry 692 (2007) 487–494
489
1612, 1517, 1438, 1161 cmꢀ1. Anal. Calc. for (C4H6O2)0.95
(C32H32N2O2)0.05: C 61.41, H 6.97, N 1.33. Found: C 61.55,
H 7.03, N 1.29%.
-
The polymeric complex formation of P3aMMA and
RuCl2/(S)-BINAP was confirmed by gel-phase 31P NMR.
Short-time (20 min) polymerization of 3a with MMA
yielded a lightly crosslinked polymer P2aMMA, which
made it possible to take a gel-phase NMR. The obtained
soft gel polymer was treated with HCl/THF followed by
neutralization to give P3aMMA. Gel-phase 31P NMR of
the polymeric complex of P3aMMA and RuCl2/(S)-
BINAP was measured. 31P NMR (CDCl3): d = 46.3.
In the case of recycle use, after the product was removed
by filtration the polymeric catalyst used was quickly
washed with 2-propanol–DMF (1:1) on a glass filter. The
whole polymeric catalyst washed was returned to the origi-
nal autoclave and used for the next reaction.
2.3.6. Copolymerization of 3a with butylacrylate (BA)
followed by deprotection
The desired polymer-supported 1,2-diamine P3aBA was
isolated in 75% yield. IR (KBr): 3450, 2955, 1735, 1612,
1517, 1438, 1160 cmꢀ1. Anal. Calc. for (C7H12O2)0.95
-
(C32H32N2O2)0.05: C 68.06, H 9.00, N 0.96. Found: C
68.10, H 9.08, N 0.95%.
2.3.7. Copolymerization of 3a with N,N-dimethylacrylamide
(DMA) followed by deprotection
The desired polymer-supported 1,2-diamine P3aDMA
was isolated in 81% yield. IR (KBr): 3565, 2930, 1637,
2.5. Asymmetric hydrogenation of other aromatic ketones
1509, 1254, 1145 cmꢀ1. Anal. Calc. for (C5H9NO)0.95
-
(C32H32N2O2)0.05: C 64.63, H 8.67, N 12.47. Found: C
64.50, H 8.59, N 12.36%.
The polymeric catalyst was prepared from polymer-
supported chiral 1,2-diamine (0.01 mmol), RuCl2/
(S)-BINAP(dmf)n (0.01 mmol) and 2 mL of dry DMF.
Asymmetric hydrogenation of aromatic ketone (5.0 mmol)
was performed in 2-propanol (2 mL) and DMF (2 mL) in
the presence of a 1.0 M tert-BuOK solution in tert-BuOH
(0.1 mL) under hydrogen pressurized to 1 MPa. After the
reaction was completed, carefully venting the hydrogen
gas, then the reaction mixture was diluted with ethyl ace-
tate (10 mL). The obtained mixture was filtered through a
glass filter equipped with silica gel. The solvent of the fil-
trate was removed under reduced pressure and the yield
was determined by GC analysis.
2.3.8. Copolymerization of 3a with isopropylacrylamide
(PAA) followed by deprotection
The desired polymer-supported 1,2-diamine P3aPAA
was isolated in 99% yield. IR (KBr): 3520, 2930, 1635,
1510, 1254, 1145 cmꢀ1. Anal. Calc. for (C6H11NO)0.95
-
(C32H32N2O2)0.05: C 66.76, H 9.25, N 11.20. Found: C
66.84, H 9.18, N 11.32%.
2.4. Asymmetric hydrogenation of acetophenone with
polymeric catalyst prepared from (S,S)-P3aMMA
2.5.1. Asymmetric hydrogenation of propiophenone
A 20 mL Schlenk vessel equipped with a Teflon-coated
magnetic stirring bar was charged with polymer-supported
chiral 1,2-diamine P3aMMA (0.02 mmol), RuCl2/(S)-
BINAP(dmf)n (0.01 mmol) and 2 ml of dry DMF. The
above mixture was degassed and heated at 80 ꢁC for
2.5 h. After removal of DMF under reduced pressure to
dryness, the solid obtained was transferred to a 100 mL
glass autoclave equipped with a pressure gauge and a gas
inlet tube attached to a hydrogen source. Air present in
the autoclave was replaced by argon. A solution of ace-
tophenone (0.58 mL, 5 mmol) in a 1:1 mixture of 2-propa-
nol (2 mL) and DMF (2 mL), and a 1.0 M tert-BuOK
solution in tert-BuOH (0.1 mL), which had been degassed,
were added to the autoclave. Hydrogen was then intro-
duced into the autoclave and pressurized to 1 MPa. The
reaction mixture was stirred for 5 h at 30 ꢁC. After care-
fully venting the hydrogen gas, the reaction mixture was
diluted with ethyl acetate (10 mL) and filtered through a
glass filter equipped with silica gel. The solvent was
removed under reduced pressure and the yield determined
by GC was 100%. Enantioselectivity of 1-phenylethanol
[17] was determined by HPLC analysis using chiral station-
ary phase (CHIRALCEL OD, Daicel): hexane/2-propa-
nol = 20:1, flow rate, 0.4 mL/min, temperature 30 ꢁC,
tR(R) = 22.8 min, tR(S) = 25.9 min.
The enantiomeric excess of (R)-1-phenyl-1-propanol [17]
was determined by chiral HPLC: column, CHIRALCEL
OD; eluent, 1:20 2-propanol–hexane; temperature 30 ꢁC;
flow rate, 0.2 mL/min; tR(R) = 43.6 min, tR(S) = 46.9 min.
2.5.2. Asymmetric hydrogenation of butyrophenone
The enantiomeric excess of (R)-1-phenyl-1-butanol [18]
was determined by chiral HPLC: column, CHIRALCEL
OD; eluent, 1:99 2-propanol–hexane; temperature 30 ꢁC;
flow rate, 0.5 mL/min; tR(R) = 47.2 min, tR(S) = 52.0 min.
2.5.3. Asymmetric hydrogenation of valerophenone
The enantiomeric excess of (R)-1-phenyl-1-pentanol [19]
was determined by chiral HPLC: column, CHIRALCEL
OD; eluent, 1:99 2-propanol–hexane; temperature 30 ꢁC;
flow rate, 0.5 mL/min; tR(R) = 41.0 min, tR(S) = 45.7 min.
2.5.4. Asymmetric hydrogenation of
40-methoxyacetophenone
The enantiomeric excess of (R)-1-(40-methoxyphe-
nyl)ethanol [17] was determined by chiral HPLC: column,
CHIRALCEL OD; eluent, 1:20 2-propanol–hexane; tem-
perature 30 ꢁC; flow rate, 0.4 mL/min; tR(R) = 39.8 min,
tR(S) = 43.1 min.

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S. Itsuno et al. / Journal of Organometallic Chemistry 692 (2007) 487–494
2.5.5. Asymmetric hydrogenation of 40-bromoacetophenone
The enantiomeric excess of (R)-1-(40-bromophenyl)etha-
nol [17] was determined by chiral HPLC: column, CHIRAL-
CEL OD; eluent, 1:20 2-propanol–hexane; temperature
30 ꢁC; flow rate, 0.2 mL/min; tR(R) = 50.3 min, tR(S) =
47.2 min.
2.5.6. Asymmetric hydrogenation of 20-methylacetophenone
The enantiomeric excess of (R)-1-(20-methylphenyl)etha-
nol [20] was determined by chiral HPLC: column, CHIRAL-
CEL AD; eluent, 1:20 2-propanol–hexane; temperature
30 ꢁC; flow rate, 0.3 mL/min; tR(R) = 30.8 min, tR(S) =
33.9 min.
2.5.7. Asymmetric hydrogenation of 1-acetonaphthone
The enantiomeric excess of 1-(1-naphthyl)ethanol [21]
was determined by chiral HPLC: column, CHIRALCEL
OD; eluent, 1:20 2-propanol–hexane; temperature 30 ꢁC;
flow rate, 0.5 mL/min; tR(R) = 47.4 min, tR(S) = 31.3 min.
Scheme 2. Polystyrene based polymer-support.
MMA in the presence of AIBN polymerization smoothly
occurred to become gel within 15 min since the chiral
monomer possesses two vinylphenyl groups as polymeriz-
able group and acted as crosslinking agent (Scheme 3).
The obtained gel (P2aMMA) was readily broken to granu-
lar solid which is insoluble in organic solvent. The polymer
however is swelled well in DMF and THF. The crosslinked
polymer P2aMMA was then treated with HCl/THF to
remove amino protecting group (Scheme 4). The Boc pro-
tecting groups in the polymer were readily removed to
afford the corresponding crosslinked polymer P3aMMA
after neutralization with a base. The polymer P3aMMA
contains free primary amino groups, which were detected
by bromophenol blue test [16]. As well as methyl methacry-
late other several methacrylates, acrylates, methacryla-
mides could be easily copolymerized with the same chiral
monomer 3 to give the crosslinked chiral polymers. In all
cases polymerization smoothly occurred and the gel formed
within 15 min to give the insoluble polymers in high yield.
Yield of the obtained crosslinked chiral polymers are listed
in Table 1.
3. Results and discussion
3.1. Synthesis of chiral monomer and its polymerization with
achiral vinyl monomer
We have prepared chiral monomer 3 [14,22] having two
4-vinylphenyl groups as polymerizable group (Scheme 1).
We have reported the copolymerization of the monomer
3 with styrene to give the chiral polymers P1 in high yield
(Scheme 2) [14]. Since the chiral monomer possesses vinyl-
phenyl group which can be copolymerized with other vinyl
monomers under radical condition. First, we studied
the copolymerization of 3a with methyl methacrylate
(MMA). DMF solution of the chiral monomer 3a and
Scheme 1. Synthesis of the chiral monomers 3.
Scheme 3. Copolymerization of 3 and achiral vinyl monomer.

S. Itsuno et al. / Journal of Organometallic Chemistry 692 (2007) 487–494
491
3.2. Asymmetric hydrogenation using polymeric catalyst
derived from P3
2-Propanol is known to be the best solvent for the
hydrogenation using RuCl2/(S)-BINAP/(S,S)-DPEN sys-
tem to give high enantioselectivity with quantitative con-
version for various kinds of ketones [23]. However,
unfortunately no reaction occurred in 2-propanol with
the catalyst prepared from P3aMMA, which was thor-
oughly shrank in the solvent (Table 2, entry 1). In order
to increase the affinity of the polymer with alcoholic sol-
vent we have prepared P3aHEMA bearing hydroxyl
pendant groups by copolymerization of 3a and 2-hydroxy-
ethyl methacrylate (HEMA). Although very low conver-
sion was observed in 5 h even in the case of the
hydroxylated polymer, after 24 h at 30 ꢁC the reaction pro-
ceeded to give the product chiral alcohol in quantitative
yield with the enantioselectivity of 65% (entry 2). We have
found that a mixed solvent system worked very well in the
case of polymeric catalyst derived from P1 [14,24]. By using
P1a acetophenone was completely hydrogenated within 5 h
to give (R)-1-phenylethanol with 76% ee (entry 15) [14]. We
have tested the enantioselective hydrogenation of acetoph-
enone by using the catalyst prepared from polymer-sup-
ported chiral 1,2-diamine P3a in the same solvent system.
As shown in Table 2 the polymeric chiral catalyst prepared
from P3aMMA performed well in the mixed solvent to give
(R)-1-phenylethanol in 78% ee with quantitative conver-
sion at 30 ꢁC (entry 4). Lowering the reaction temperature
to 10 ꢁC slightly higher enantioselectivity (80% ee) was
obtained after 24 h (entry 5). Temperature effect (entries
7–10) was also observed in the reaction using the catalysts
prepared from P3aPMA, P3aBMA. When XylBINAP [25]
was used instead of BINAP higher enantioselectivity (97%
ee) was obtained as expected from the low-molecular-
Scheme 4. Deprotection of Boc groups to give the chiral 1,2-diamine
polymers P3.
Table 1
Preparation of crosslinked polymer-supported chiral 1,2-diamine
Chiral 1,2-diamine polymer
R1
Yield (%)
R2
n
P3aMMA
P3bMMA
P3aHEMA
P3aPMA
P3aBMA
P3bBMA
P3bTBMA
P3aMA
OMe
OMe
OCH2CH2OH
OiPr
OBu
OBu
OtBu
OMe
OMe
OBu
OBu
NMe2
NMe2
NHiPr
NHiPr
Me
Me
Me
Me
Me
Me
Me
H
H
H
H
H
1
4
1
1
1
4
4
1
4
1
4
1
4
1
4
91
100
95
99
93
90
88
76
85
75
82
81
90
99
94
P3bMA
P3aBA
P3bBA
P3aDMA
P3bDMA
P3aPAA
P3bPAA
H
H
H
Table 2
Asymmetric hydrogenation of acetophenone with polymer-supported chiral catalyst prepared from P3aa
Entry
Chiral 1,2-diamine polymer
Temperature (ꢁC)
Time (h)
Conversion (%)
Ee (%)
Configuration
1b
2b
3
4
5
6c
7
P3aMMA
P3aHEMA
P3aHEMA
P3aMMA
P3aMMA
P3aMMA
P3aPMA
P3aPMA
P3aBMA
P3aBMA
P3aMA
30
30
30
30
10
30
15
30
15
30
30
30
30
30
30
24
24
5
5
24
5
24
5
36
5
5
5
0
>99
81
>99
96
>99
>99
71
>99
>99
81
–
–
65
74
78
80
97
80
76
79
76
73
77
76
72
76
R
R
R
R
R
R
R
R
R
R
R
R
R
R
8
9
10
11
12
13
14
15
a
P3aBA
>99
>99
80
P3aDMA
P3aPAA
Pla
5
5
5
>99
Reactions were conducted at 1 MPa of H2 using ketone (5 mmol), tert-BuOK(1 M, 100 lL), (S,S)-1,2-diamine polymer (0.02 mmol) and (S)-BINAP/
RuCl2 (0.01 mmol) in 2-propanol (2 mL) and DMF (2 mL).
b
Reaction was performed in 2-propanol.
XyIBINAP was used instead of BINAP.
c

492
S. Itsuno et al. / Journal of Organometallic Chemistry 692 (2007) 487–494
Table 3
Asymmetric hydrogenation of acetophenone with polymer-supported chiral catalyst prepared from p3ba
Entry
Chiral 1,2-diamine polymer
Temperature (ꢁC)
Time (h)
Conversionb (%)
Eec (%)
Configuration
1
2
3
4
5
6
7
a
P3bMMA
P3bBMA
P3bTBMA
P3bBA
30
30
30
30
30
30
30
5
5
5
5
5
5
5
>99
>99
>99
>99
95
77
79
79
78
78
77
77
R
R
R
R
R
R
R
P3bDMA
P3bPAA
P1b
85
>99
Reaction conditions: see footnote in Table 2.
Determined by GC analysis.
Determined by HPLC using Chiralcel OD.
b
c
Table 5
Asymmetric hydrogenation of aromatic ketones with RuCl2/(S)-BINAP/
(S,S)-DPEN in 2-propanol–DMFa
Table 4
Asymmetric hydrogenation of aromatic ketones with polymer-supported
chiral catalyst prepared from P3aMMAa
Ketone
Time (h)
1
Conversionb (%)
Eec (%)
Ketone
Time (h)
5
Conversionb (%)
>99
Eec (%)
78
>99
80
1
1
1
1
>99
>99
>99
>99
84
83
91
76
12
12
12
12
>99
>99
>99
>99
84
86
87
79
1
>99
50
12
>99
49
4
1
>99
>99
94d
12
12
>99
>99
94d
97
96
a
Reactions were conducted at 1 MPa of H2 using ketone (5 mmol), tert-
BuOK (1 M, 100 lL), (S,S)-1,2-diphenylethylenediamine (0.05 mmol) and
(S)-BINAP/RuCl2 (0.025 mmol).
a
Reaction conditions: see footnote in Table 2.
Determined by GO analysis.
Determined by HPLC using Chiralcel OD.
Determined by HPLC using Chiralcel AD.
b
c
b
Determined by GO analysis.
Determined by HPLC using Chiralcel OD.
c
d
d
Determined by HPLC using Chiralcel AD.

S. Itsuno et al. / Journal of Organometallic Chemistry 692 (2007) 487–494
493
Table 7
weight catalyst developed by Noyori et al. [3,26] (entry 6).
Polyacrylates (P3aMA, P3aBA) and polyacrylamides
(P3aDMA, P3aPAA) can be also used as polymer-support
for the same reaction (entries 11–14) to give the results sim-
ilar to that from P3aMMA.
Recycle use of polymeric catalyst in asymmetric hydrogenation of
acetophenone at 30 ꢁCa
Polymer
BINAP
BINAP
Run Time (h) Conversionb (%) Eec (%)
P1b
1
2
3
4
12
12
12
12
>99
>99
>99
>99
76
76
75
76
3.3. Asymmetric hydrogenation using polymeric catalyst
derived from P3b
P1b
XylBINAP
1
2
3
4
5
6
18
18
18
18
18
18
>99
>99
>99
>99
>99
>99
97
98
97
98
97
97
We have prepared another chiral monomer 3b having
longer methylene chain between chiral diamine and poly-
merizable group [22]. Copolymerization of 3b with methyl
methacrylate followed by deprotection gave an insoluble
polymer P3bMMA containing chiral 1,2-diamine moieties.
In this polymer 1,2-diamine moiety has conformationally
more flexible structure, which might cause a suitable com-
plex formation in the polymer network. Table 3 shows the
results obtained from the polymer-supported catalysts
derived from the methylene spacer type ligand P3b. In most
cases slightly increased enantioselectivities were obtained
compared to those from P3a in the asymmetric hydrogena-
tion of acetophenone.
P3aMMA BINAP
1
2
3
4
12
12
12
12
>99
>99
>99
>99
78
78
78
78
a
Reaction conditions: see footnote in Table 2.
Determined by GC analysis.
Determined by HPLC using Chiralcel OD.
b
c
catalyst. High level of asymmetric induction was observed
in all cases (Table 4). In order to compare these results and
those obtained from the corresponding low-molecular-
weight counterpart in solution system the same ketones
were hydrogenated by using RuCl2/(S)-BINAP/(S,S)-
DPEN in a mixed solvent of 2-propanol and DMF (Table
5). As shown in Table 5 the enantioselectivity values are
nearly equal to those from polymeric catalyst. Chiral cata-
lyst prepared from P3bBMA having longer methylene
chain spacer was also used for the reaction and the similar
results were attained as shown in Table 6.
3.4. Asymmetric hydrogenation of various aromatic ketones
Various aromatic ketones other than acetophenone were
also subjected to the same reaction using P3aMMA derived
Table 6
Asymmetric hydrogenation of aromatic ketones with polymer-supported
chiral catalyst prepared from P3bBMAa
Ketone
Time (h)
Conversionb (%)
Eec (%)
5
5
>99
>99
79
(80)e
(84)e
(91)e
(76)e
77d
3.5. Recyclability of the polymer-supported catalyst
Since the catalysts used in this article are all made of
crosslinked insoluble polymer, the separation of the cata-
lyst and solvent containing resulting product is easy to
do by simple filtration. After the removal of the solvent
including the product, the remaining polymeric catalyst
was ready to use for the following reaction. Table 7 shows
the results of repeated use of the polymeric catalyst in the
asymmetric hydrogenation of acetophenone. In the case
of P1b/RuCl2/XylBINAP combination high level of
enantioselectivity with quantitative conversion was main-
tained until six recycling.
12
12
12
>99
>99
>99
83
88
84
4. Conclusion
12
>99
96
(97)e
We have prepared enantiomerically pure 1,2-diamine
monomers 3, which were copolymerized with various kinds
of achiral vinyl monomers including styrene, methacry-
lates, acrylates, methacrylamide, and acrylamide to give
polymer-supported chiral 1,2-diamine P3 after the removal
of Boc protecting groups. The diamine polymer was
allowed to react with RuCl2–BINAP to form polymeric
chiral complex in DMF. Enantioselective hydrogenation
a
Reaction conditions: see footnote in Table 2.
Determined by GC analysis.
Determined by HPLC using Chiralcel OD.
P3bMMA was used as polymeric 1,2-diamine.
b
c
d
e
RuCl2/(S)-BINAP/(S,S)-DPEN was used as a catalyst in DMF–2-
propanol.

494
S. Itsuno et al. / Journal of Organometallic Chemistry 692 (2007) 487–494
Yamamoto (Eds.), Comprehensive Asymmetric Catalysis II, Springer,
Berlin, 1999, p. 581.
[11] E. Jacobsen, Aziridination, in: E.N. Jacobsen, A. Pfaltz, H.
Yamamoto (Eds.), Comprehensive Asymmetric Catalysis II, Springer,
Berlin, 1999, p. 607.
[12] (a) Reviews on asymmetric reaction using polymer-supported cata-
lyst, see: S. Itsuno, N. Haraguchi, Y. Arakawa, Recent Res. Devel.
Organic Chem. 9 (2005) 27;
of aromatic ketones successfully occurred by using the
polymeric catalyst in 2-propanol/DMF (1:1). The enanti-
oselectivities obtained with the polymeric catalyst exhibited
almost the same level as those obtained from the low-
molecular-weight counterpart in solution system. Since
the polymers have crosslinked structure the insoluble poly-
meric catalyst could be easily separated from the reaction
mixture and recycled several times without loss of its
activity.
(b) S. Itsuno, in: J.C. Salamone (Ed.), Polymeric Materials Encyclo-
pedia, vol. 10, CRC Press, Boca Raton, 1996, p. 8078;
(c) T.J. Dickerson, N.N. Read, K.D. Janda, Chem. Rev. 102 (2002)
3325;
(d) Q.-H. Fan, Y.-M. Li, A.S. Chan, Chem. Rev. 102 (2002) 3385;
(e) N.E. Leadbeater, M. Marco, Chem. Rev. 102 (2002) 3217.
[13] BINAP = 2,20-Bis(diphenylphosphino)-1,10-binaphthyl.
[14] S. Itsuno, A. Tsuji, M. Takahashi, J. Polym. Sci.: Part A: Polym.
Chem. 42 (2004) 4556.
[15] M. Takahashi, A. Tsuji, M. Chiba, S. Itsuno, React. Funct. Polym.
65 (2005) 1.
[16] (a) V. Krchnak, J. Vagner, M. Lebl, Int. J. Pept. Protein Res. 32
(1988) 415;
Acknowledgements
This work was supported by a Grant-in-Aid for Scien-
tific Research in Priority Areas (No. 16033230, ‘‘Reaction
Control of Dynamic Complexes’’) from the Ministry of
Education, Culture, Sports, Science, and Technology,
Japan.
(b) V. Krchnak, J. Vagner, P. Safar, M. Lebl, Collect Czech Chem.
Commun. 53 (1988) 2542.
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