Chiral polyethers derived from BINOL and ECH as highly enantioselective and efficient catalysts for the borane reduction of prochiral ketones

Article abstract of DOI:10.1016/j.molcata.2015.01.007

Two novel polyethers derived from BINOL were synthesized and used to induce the enantioselective borane reduction of prochiral ketones. The polyethers gave the expected secondary alcohols with up to 98% yields and over 99% ee values. The recovered polyethers could be reused for many times to induce the enantioselective reduction of prochiral ketones without losing their enantioselective induction ability.

Full text of DOI:10.1016/j.molcata.2015.01.007

Journal of Molecular Catalysis A: Chemical 398 (2015) 407–412
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Journal of Molecular Catalysis A: Chemical
journal homepage: www.elsevier.com/locate/molcata
Chiral polyethers derived from BINOL and ECH as highly
enantioselective and efficient catalysts for the borane
reduction of prochiral ketones
An-Lin Zhang, Zeng-da Yu, Li-Wen Yang∗, Nian-Fa Yang∗, Dan Peng
Key Laboratory of Environmentally Friendly Chemistry and Applications of Ministry of Education, College of Chemistry, Xiangtan University,
Hunan 411105, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Two novel polyethers derived from BINOL were synthesized and used to induce the enantioselective
borane reduction of prochiral ketones. The polyethers gave the expected secondary alcohols with up to
98% yields and over 99% ee values. The recovered polyethers could be reused for many times to induce the
enantioselective reduction of prochiral ketones without losing their enantioselective induction ability.
© 2015 Elsevier B.V. All rights reserved.
Received 5 November 2014
Received in revised form 7 January 2015
Accepted 8 January 2015
Available online 13 January 2015
Keywords:
Polyether
BINOL
Epichlorohydrin
Reduction
Enantioselectivity
1. Introduction
a highly enantioselective monomeric catalyst and then the attach-
ment of this monomeric catalyst to a flexible and sterically irregular
Asymmetric synthesis of enantiomerically enriched secondary
alcohols has been widely studied, because chiral secondary alcohols
are important synthetic intermediates for various other function-
alities such as halide, amine, ester, and ether, and involved in
many natural products and pharmaceuticals [1]. Extensive activ-
ities in the field of asymmetric synthesis and catalysis have led to
the discovery of many highly enantioselective catalysts [2–5]. A
number of effective catalysts have been applied to pharmaceutical
and agricultural industries for the asymmetric synthesis of chiral
organic molecules. Since it is often quite expensive to prepare the
optically active catalysts, their easy recovery and reuse are highly
desirable. Because of the significant size difference between poly-
mers and small molecules, using polymer based catalysts greatly
simplifies both the recycle of the catalysts and purification of
the products [6–9]. Heterogeneous and homogeneous recyclable
stereoselective catalysts can be separated by simple filtration or
precipitation [10–16]. The traditional approach to constructing
polymer-supported chiral catalysts involves the development of
polymer backbone. Although a few polymer-supported catalysts
have been obtained in this way, a significant drop of enantios-
electivity is often observed when a monomeric chiral catalyst is
attached to a polymer support due to the changes in the microen-
vironment of the catalytic sites [17–20].
We have been working on asymmetric syntheses and catalysis
using chiral aminoalcohols prepared from chiral epichlorohydrin
(ECH), which was cheap and easily available [21,22]. In our previ-
ous study, it was found that an amino diol derived from (S)-ECH
served as an efficient catalyst for the enantioselective alkylation
of aldehydes and corresponding chiral secondary alcohols were
obtained with moderate to high enantiomeric excesses. We also
found that some polymer-supported catalysts derived from chi-
ral ECH gave moderate results for the enantioselective addition of
aldehydes with organometallic reagents [23,24].
Chiral 1,1-bi-2-naphthol (BINOL) has occupied a prominent
position because of its ability to form highly enantioselective cat-
alysts with main group elements [25,26], transition metals [27,28]
and rare earth elements [29,30]. Immobilization of BINOL has ear-
lier been achieved either by grafting onto a sterically irregular
polymer backbone [31–34] or by cross-linking copolymerization
[35]. However, the random orientation of ligands and the diffu-
sional limitations encountered in such systems make them less
∗
Corresponding authors. Tel.: +86 15200353035.
E-mail addresses: yangliwen 0519@163.com (L.-W. Yang),
nfyang@mail.sdu.edu.cn (N.-F. Yang).
http://dx.doi.org/10.1016/j.molcata.2015.01.007
1381-1169/© 2015 Elsevier B.V. All rights reserved.

408
A.-L. Zhang et al. / Journal of Molecular Catalysis A: Chemical 398 (2015) 407–412
probable candidates for generating catalyst complexes in which
two or three BINOL ligands are bound to a central metal ion [36]. We
envisaged that the use of soluble polymer derived from BINOL and
ECH might allow the ligands to suitably orient themselves during
complexation leading to better catalysts. Given these, two BINOL-
derived chiral polyethers were designed and synthesised, and then
used for inducing the formation of the enantiomerically enriched
secondary alcohols. Boron based chiral reducing agents/catalysts
occupy a special place in chiral chemistry, particularly in asym-
metric reductions, because of their extensive use in efficiently and
conveniently transforming prochiral ketones into the correspond-
ing secondary alcohols with high enantioselectivities [37–41]. So
that the enantioselective metal-free borane reduction of prochi-
ral ketones was conducted to assess the catalytic activity of the
polyethers.
In a similar manner, compounds (S,S)-3-(glycidyloxy)-2,2ꢀ-
bis(methoxymethyloxy)-1, 1ꢀ-binaphthalene 6 were prepared from
(S)-3-hydroxy-2,2ꢀ-bis(methoxymethyloxy)-1, 1ꢀ-binaphthalene
4
and (S)- epichlorohydrin. Yield, 82%, [˛]20 365 = −671.02
(c = 10 mg/ml, THF), Elem. Anal. Calcd for C27H26O6: C 72.63,
H 5.87; Found: C 73.02, H 6.02. 1H NMR (CDCl3) ı 7.95–7.93
(d, J = 9.02 Hz, 1H, Ar H), 7.86–7.84 (d, J = 8.0 Hz, 1H, Ar H),
7.78–7.76 (d, J = 8.0 Hz, 1H, Ar H), 7.59–7.57 (d, J = 9.0 Hz, 1H,
Ar H), 7.36–7.13 (m, 7H, Ar H), 5.15–5.13 (d, J = 6.7 Hz, 1H, CH2),
5.01–4.99 (d, J = 6.6 Hz, 1H, CH2), 4.91–4.88 (t, J = 3.4 Hz, 1H, OCH2),
4.86–4.83 (t, J = 5.6 Hz, 2H, CH2), 4.46–4.43 (d, J = 10.7 Hz, 1H, CH),
4.21–4.17 (m, 1H, CH2), 3.48 (s, 1H, CH2), 3.18(s, 3H, CH3) 2.96 (s,
1H, CH2), 2.84 (s, 1H, CH2), 2.81 (s, 1H, CH2), 2.63 (s, 3H, CH3), 13
C
NMR (101 MHz, CDCl3) ı 152.5, 148.1, 145.0, 133.8, 132.2, 130.0,
129.7, 128.5, 127.9, 126.70, 126.6, 126.0, 125.9, 125.6, 125.3, 124.4,
123.8, 120.5, 116.7, 111.4, 99.7, 95.1, 57.5, 55.9.
2. Experimental
2.3. Solution anionic polymerization
2.1. General
A test tube with stir bar was charged with 10.00 mmol of 3-
(glycidyloxy)-2, 2ꢀ-bis(methoxymethyloxy)-1,1ꢀ-binaphthalene 5
or 6 (4.46 g), a desired amount (19 mg, 0.34 mmol for example) of
KOH and 1.25 ml xylene under argon atmosphere and then sealed
with rubber stopper. The test tube was put into an oil bath ther-
mostated at the desired temperature (such as 140 ◦C). The reaction
mixture was stirred for 48 h. During this time, the mixture turned
to auburn and got more and more viscous. After it was complete,
2 ml hydrochloric acid was added dropwise to the tube at 0 ◦C. After
being stirred for 24 h at room temperature. The THF solution was
poured into methanol (100 ml). The formed precipitate was filtered
and washed with methanol. The above-mentioned precipitation
process was repeated, then the obtained precipitate was dried
in vacuo at 50 ◦C to obtain polymer. yield 80–82%. 1H NMR ı/ppm:
8.02–7.10 [br, 11H, Ar H], 4.52–3.56[br, 2H, > CH2 , CHO ],
3.08–3.01 [br, 3H, CH2]. Poly-5, yield 80%, [˛]20 365 = −792.80
(c = 5 mg/ml, THF); Mn = 7.4 × 103; PDI = Mw/Mn = 2.11. Poly-6,
yield 82%, [˛]20 365 = 912.16 (c = 5 mg/ml, THF); Mn = 7.8 × 103;
PDI = Mw/Mn = 2.02.
All reagents were used as supplied commercially unless other-
wise noted. THF and toluene were distilled from sodium under N2
before use. Optically active epichlorohydrin (ECH) was purchased
from Yueyang Branch Company, Shenzhen Yawangkangli Technol-
ogy Co., Ltd. 1H NMR and 13C NMR spectra were performed on a
Bruker ARX400 MHz spectrometer using tetramethylsilane(TMS)
as internal standard. Optical rotation data was measured on a
Perkin Elmer Model 341 LC Polarimeter at 365 nm. GPC analysis
was performed with a JASCO-GPC system consisting of DG-1580-
53 degasser, PU-980HPLC pump, UV-970 UV–vis detector, RI-930
RI detector, and CO-2065-plus column oven (at 38 ◦C) using two
connected Shodex GPC-KF-804L columns in THF (sample con-
centration = 1 wt %; flow rate = 1.0 ml/min). The molecular weight
was calibrated with a commercially available polystyrene. Melting
points were determined with a SGW X-4 melting point apparatus.
(S)-2,2ꢀ-bis(methoxymethoxy)-1,1ꢀ- binaphthyl 2, (S)-3-iodo-2,2ꢀ-
bis(methoxymethyl)-1,1ꢀ-bi-2-naphthol 3 and (S)-3-hydroxy-2,2ꢀ-
bis(methoxymethyl)-1,1ꢀ-bi-2-naphthol 4 were prepared accord-
ing to the literatures [42–44].
2.4. Typical procedure for the reduction of prochiral ketones
2.2. (S, R)-3-(glycidyloxy)-2,2ꢀ-bis(methoxymethyloxy)-1,1ꢀ-
binaphthalene 5
BH3/SMe2 (1.1 ml, 1 M) was added by syringe to a solution of
chiral polyether ligand Poly-6 (0.78 g, 0.1 mmol) in dry THF (5 ml)
under nitrogen at 0 ◦C. The mixture was stirred for 1 h at 0 ◦C and
then a solution of ketone (1 mmol) in dry THF (5 ml) was added
dropwise over a period of 1 h at the same temperature and stirred
for 6 h, the reaction mixture was then quenched by dropwise addi-
tion of 10% NH4Cl (5 ml). The alcohol product was isolated by
extraction with ethyl acetate (10 ml × 3). The organic phase was
washed with brine, dried over anhydrous sodium sulfate. After
concentration by rotatory evaporation, the product was purified
by column chromatography on silica gel (petroleum ether/ethyl
acetate 6:1) to afford the corresponding alcohol. The enantiomeric
excesses were determined by HPLC with a chiral column (Dai-
cel Chiralcel OD-H; eluent, hexane-isopropyl alcohol; UV detector,
254 nm).
To a solution of (S)-3-hydroxy-2,2ꢀ- bis(methoxymethyl)-1,1ꢀ-
bi-2-naphthol 4 (3.9 g, 10 mmol) in dry THF (30 ml), powdered
potassium hydroxide (2.24 g, 40 mmol) and tetrabutylammonium
bromide (0.32 g, 1 mmol) was added and stirred for 2 h at room tem-
perature. Then (R)-epichlorohydrin (1.84 g, 20 mmol) was added
and stirred for 20 h, mixture was extracted with ethyl acetate
and washed with a solution of 1:1 brine and water and the com-
bine organic layers were concentrated. Further purification was
accomplished using silica column chromatography with 20% ethyl
acetate in petroleum ether to give the corresponding epoxide. Yield,
84%, [˛]20 365 = −612.50 (c = 10 mg/ml, THF), Elem. Anal. Calcd for
C27H26O6: C 72.63, H 5.87; Found: C 72.82, H 5.81. 1H NMR (CDCl3)
ı 7.95–7.93 (d, J = 9.02 Hz, 1H, Ar H), 7.86–7.84 (d, J = 8.0 Hz, 1H,
Ar H), 7.78–7.76 (d, J = 8.0 Hz, 1H, Ar H), 7.59–7.56 (d, J = 9.0 Hz,
1H, Ar H), 7.36–7.12 (m, 7H, Ar H), 5.15–5.13 (d, J = 6.7 Hz, 1H,
CH2), 5.0–4.9 (d = 6.6 Hz, 1H, CH2), 4.91–4.90 (d, J = 6.4 Hz, 1H, CH2),
4.88–4.83 (dt, J = 5.6, 10.0 Hz, 2H, CH2), 4.46–4.43 (d, J = 10.7 Hz, 1H,
CH), 4.21–4.18 (m, 1H, CH2), 3.48 (s, 1H, CH2), 3.17 (s, 3H, CH3) 2.95
(s, 1H, CH2), 2.84 (s, 1H, CH2), 2.81 (s, 1H, CH2), 2.63 (s, 3H, CH3),
13C NMR (101 MHz, CDCl3) ı 152.5, 148.1, 145.0, 133.8, 132.2, 129.9,
129.7, 128.5, 127.9, 126.70, 126.6, 126.0, 125.8, 125.5, 125.3, 124.3,
123.7, 120.4, 116.8, 111.3, 99.6, 95.2, 57.4, 56.0.
3. Result and discussion
Two new polyether ligands Poly-5 and Poly-6 were synthesized
from commercially available 1,1ꢀ-binaphthol (BINOL) as depicted in
Scheme 1. First, chiral (S)-BINOL 1 was reacted with chloromethyl
ether to give (S)-2,2ꢀ-bis(methoxymethyloxy)-1,1ꢀ-binaphthalene
2 [42]. (S)-3-iodo-2,2ꢀ-bis(methoxymethyl)-1,1ꢀ-bi-2-naphthol 3
was easily prepared from readily available 2 through a lithiation-
iodination sequence [43]. The copper-mediated(CuI) hydroxy-

A.-L. Zhang et al. / Journal of Molecular Catalysis A: Chemical 398 (2015) 407–412
409
Scheme 1. The synthetic route for the monomers 5 and 6.
lation of (S)-3-iodo-2,2ꢀ-bis(methoxymethyl)-1,1ꢀ-bi-2-naphthol
3 with hydroxide salts (KOH and NaOH) as nucleophiles to
directly form (S)-3-hydroxy-2,2ꢀ-bis(methoxymethyl)-1,1ꢀ-bi-2-
PDI = 2.11) (Fig. 1) and Poly-6 (Mn = 7800, PDI = 2.02) (Fig. 2) in high
yields, respectively.
It is well known that the enantioselectivity of borane reduction
is greatly affected by solvent, temperature, and the amount of cata-
lyst [45–48]. In order to evaluate the above effects, we investigated
the reduction of ketone with the chiral polyether ligand Poly-5
under various reaction conditions and compared the catalytic activ-
ity and enantioselectivity of polyether ligand Poly-6. The results are
summarized in Table 1. After extensively screening, we chose the
reaction media of THF, DCM and toluene to examine the solvent
effects. At room temperature, the reduction was completed within
6 h in THF and 12 h in toluene and 10 h in DCM with moderate ee
values (entries 1–3). As reaction time was shorted to 8 h in toluene,
naphthol
4 under mild conditions and in the presence of
1,10-phenanthroline-which is inexpensive and commercially
available [44]. The coupling of (S)-ECH or (R)-ECH with 4 was suc-
cessfully carried out using KOH as the depronation reagent to afford
the monomer 5 or 6 with good yield (80–82%) in the presence of
tetrabutylammonium bromide(TBAB) (Scheme 1). In most case, the
polymerization of optical 5 and 6 were carried out in bulk using KOH
as an initiator. In order to obtain higher molecular weight, the solu-
tion polymerization of 5 and 6 were conducted in xylene, followed
by deprotection of the MOM group to afford Poly-5 (Mn = 7400,
Fig. 1. Poly-(S,R)-3-(glycidyloxy)-2,2’-bis(methoxymethyloxy)-1,1’-binaphthalene Poly-5.

410
A.-L. Zhang et al. / Journal of Molecular Catalysis A: Chemical 398 (2015) 407–412
Table 1
Optimization and catalyst screening for the borane reduction of 2-bromoacetophenone. a
Entry
Ligand
Loading(mol%)
Solvent
Reactiontime(h)
Temp(◦C)
Yield/%b
Ee/%c,d,e
1
2
3
4
5
6
7
8
Poly-5
Poly-5
Poly-5
Poly-5
Poly-5
Poly-5
Poly-5
Poly-5
Poly-5
Poly-5
Poly-6
5
5
5
5
5
5
5
5
Toluene
THF
DCM
12
6
10
8
16
12
12
12
12
12
12
r.t.
r.t.
r.t.
r.t.
r.t.
50
50
0
93
90
94
80
94
96
90
92
90
50
95
78
76
70
78
80
72
66
86
95
95
>99
Toluene
Toluene
Toluene
THF
Toluene
Toluene
Toluene
Toluene
9
10
11
10
15
10
0
0
0
a
Reaction was carried out on a 1.0 mmol scale in 5 ml of solvent, n(2-bromoacetophenone): n(BH3·THF) = 1.0: 1.1.
Isolated yields after purification by column chromatography (silica gel, 10% ethyl acetate in petroleum ether).
Determined by HPLC analysis using chiral column.
Absolute configurations were assigned by comparison with the sign of specific rotations reported in the literature.
(S)-product was isolated by column chromatography.
b
c
d
e
the yield of the product was decrease significantly (entry 4). No
expected increase of ee value was observed although a prolonged
time was used (entry 5). When the reaction temperature reached
50 ◦C, the ee values were 72% in toluene and 66% in THF (entries 6
and 7), respectively. By decreasing the reaction temperature to 0 ◦C,
the reaction was completed in toluene within 16 h and 86% ee was
obtained. The results showed that toluene is a more effective sol-
vent for the present reduction and the level of enantiometric excess
is sensitive to the reaction temperature. Subsequently, the catalyst
loading was investigated. It was observed that a increase in the cat-
alyst loading from 5 to 10 mol% at 0 ◦C resulted in a large increase
in the enantioselectivity (95% ee) and a slight loss of yield (entries 8
and 9). By further adding the amount of catalyst to up to 15 mol%, a
large decrease in the yield was seen (entry 10), although the ee val-
ues were not affected. As a compromise among catalyst loading, the
yield and the ee value, a polyether ligand Poly-5 loading of 10 mol%
provided the optimum level of enantioselectivity, which is presum-
ably because the rate of the catalyzed reaction in the presence of
10 mol% catalyst is sufficiently faster than the noncatalytic reduc-
tion with only BH3·SMe2. We also examined the effect of ligand
Poly-6 on the reduction of 2-bromoacetophenone, and surprisingly
excellent enantiometric excess (over 99%) was obtained. (entry 11).
These results indicate that the structural effect of polyether Poly-6
derived from BINOL increase the enantioselectivity of the catalyst
greatly.
Under the optimized reaction conditions, the chiral polyether
Poly-6 was applied to the asymmetric reduction of a variety of
aromatic ketones with BH3·SMe2 (Table 2). High yields and enan-
tioselectivities were obtained not only for the prochiral ketones
containing electron-donating group (entries 1–3) but also for those
with a substitution at the ortho position (entry 4), unlike most
of catalyst [49–52], of which the enantioselectivity was highly
dependent on steric effects. Over 99% ee values were also observed
for prochiral ketones with electron-withdrawing groups (entries
5–9). We also extended the reaction to the reduction of ketones
without substituent group under the same conditions, which gave
the modest ee values (entries 10, 12 and 14). Raising the amount
of catalyst resulted in a slightly increase in the ee values and
dramatically decrease in the yields (entries 11, 13 and 15). A sim-
ple heteroaromatic ketone 2-acetylpyridine could be reduced in
good ee under the influence of catalytic polyether Poly-6 (entry
16). The reduction of aliphatic ketones such as butan-2-one and
pentan-3-one gave only 65% and 60% ee, respectively (entries
17 and 18). These indicated that the reactivity and enantios-
electivity were significantly affected by a substituent atom of
ketone.
Fig. 2. Poly-(S,S)-3-(glycidyloxy)-2,2’-bis(methoxymethyloxy)-1,1’-binaphthalene Poly-6.

A.-L. Zhang et al. / Journal of Molecular Catalysis A: Chemical 398 (2015) 407–412
411
Table 2
Asymmetric reduction of prochiral ketone.a
Entry
R1
R2
Yield/%b
E.e./%c
>99
Config.d
1
2
3
4
5
6
7
8
9
10
11e
12
13e
14
15e
16
17
18
4-Methylphenyl
4-Methoxyphenyl
3-Methoxyphenyl
Phenyl
4-Chlorophenyl
4-Bromophenyl
4-Fluorophenyl
4-Nitrophenyl
4-Chlorophenyl
1-Naphthyl
1-Naphthyl
Phenyl
Phenyl
Phenyl
Phenyl
2-Pyridyl
Ethyl
Ethyl
H
H
H
Br
H
H
H
H
CH3
H
96
93
95
95
94
98
95
98
90
96
50
90
60
92
55
92
90
88
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
>99
>99
>99
>99
>99
>99
>99
>99
76
88
82
90
80
Fig. 3. Presumed transition state for borane reduction.
H
strates occurs through a macroheterocycle. The transition state I is
more favored than II because of the steric interactions between the
rigid plane of BINOL and ketones, and hence the attack of hydride
occurs on the Si-face of the electronically deficient carbonyl carbon
atom to form chiral secondary alcohols. Obviously a more in-depth
study is needed to elucidate the mechanism of the asymmetric
borane reduction.
CH3
CH3
H
H
H
90
89
65
60
H
CH3
a
n(Ketone): n(BH3.THF): n(Poly-6) = 1: 1.1: 0.1; reaction time: 12 h.
Isolated yields after purification by column chromatography (silica gel, 10% ethyl
b
acetate in petroleum ether).
4. Conclusion
c
Determined by HPLC analysis using chiral column.
d
Absolute configurations were assigned by comparison with the sign of specific
In conclusion, two new chiral polyether catalysts have been syn-
thesized from commercially available BINOL and epichlorohydrin.
The catalytic borane reduction of ketones with these new chi-
ral catalysts was investigated, and high enantioselectivities were
obtained (up to over 99%). The results showed that polyether Poly-
6 was a very efficient catalyst for the enantioselective borane
reduction of ketones. Meanwhile, catalyst Poly-6 can be recovered
and reused six times without any significant loss of activity. The
development of other asymmetric reactions using these polyethers
ligands is currently ongoing in our group.
rotations reported in the literature [53,54].
e
The amount of catalyst Poly-6 is 15 mol%.
Meanwhile, it is worth noting that the chiral polyether Poly-
6 can be easily separated and recycled. After the reduction was
completed, the reaction was quenched with water and extracted.
After evaporating the solvent, the product was isolated by being
redissolved in methanol resulting in the precipitate ligand Poly-
6 being obtained. Next, the polyether ligand Poly-6 was washed
several times with methanol and dried. Recycling of the polyether
ligand Poly-6 was tested by the reduction of 2-bromoacetophenone
(Table 3). The results show that ligand Poly-6 could be reused at
least six times with no loss of performance (ee over 99%).
The asymmetric borane reduction catalyzed by BINOL derived
ligands such as Poly-6 may be rationalized through a proposed
mechanism (Fig. 3). Owing to the blocking effect of the polyether
segment on the 3-position of BINOL unit, it is likely that two
borane molecules cannot complex with the oxygen atom on the
2-position of BINOL unit simultaneously to form a similar transi-
tion state proposed by Corey et al. [55–57]. Thus, we proposed that
the first borane molecule could combine to two oxygen atom to
form a seven-membered ring and that then the secondary borane
molecule can only combine to the oxygen atom on 2ꢀ-position of
BINOL unit. As a result the facial attack of hydride to ketone sub-
Acknowledgments
We gratefully thank the National Science Foundation of China
(21172186) and the Research Fund for the Doctoral Program of
Higher Education of China (No. 20134301110004) for financial sup-
port of this work.
Appendix A. Supplementary data
Supplementary data associated with this article can be
found, in the online version, at http://dx.doi.org/10.1016/j.molcata.
2015.01.007.
References
Table 3
[1] K. Soai, S. Niwa, Chem. Rev. 92 (1992) 833–856.
[2] I. Ojima (Ed.), Catalytic Asymmetric Synthesis, VCH, New York, 1993, pp.
103–158.
Recycling experiments of poly-6 in the reduction of 2-bromoacetophenone.
[3] R. Noyori, Asymmetric Catalysis in Organic Synthesis, John Wiley & Sons, New
York, 1994, pp. 56–82.
[4] L. Pu, H.-B. Yu, Chem. Rev. 101 (2001) 757–824.
[5] C.A. McNamara, M.J. Dixon, M. Bradley, Chem. Rev. 102 (2002) 3275–3300.
[6] Q. Fan, C. Ren, C. Yeung, W. Hu, A.S.C. Chan, J. Am. Chem. Soc. 121 (1999)
7407–7408.
[7] R. Almansa, J.F. Collados, D. Guijarro, M. Yus, Tetrahedron: Asymmetry 24
(2013) 116–120.
[8] K. Matkiewicz, A. Bukowska, W. Bukowski, J. Mol. Catal. A: Chem. 368–369
(2013) 43–52.
[9] M. Benaglia, A. Puglisi, F. Cozzi, Chem. Rev. 103 (2003) 3401–3427.
[10] X.W. Wang, K.L. Ding, J. Am. Chem. Soc. 126 (2004) 10524–10525.
[11] L. Shi, X.W. Wang, C.A. Sandoval, M.X. Li, Q.Y. Qi, Z.T. Li, K.L. Ding, Angew.
Chem. Int. Ed. 45 (2006) 4108–4112.
Cycle
1
2
3
4
5
6
Recovery(%)a
Yield(%)b
Ee(%)c
92
90
>99
94
89
90
92
>99
90
90
88
92
95
94
>99
>99
>99
>99
a
Reaction was carried out on a 1.0 mmol scale in 5 ml toluene at 0 ◦C, molar of
PhCOCH2Br, BH3·SMe2, Poly-6= 1.0: 1.1: 0.1; reaction time: 12 h.
b
Isolated yield by column chromatography.
Determined by HPLC analysis using a Daicel Chiralcel column.
c

412
A.-L. Zhang et al. / Journal of Molecular Catalysis A: Chemical 398 (2015) 407–412
[12] Á. Zsigmond, S. Undrala, F. Notheisz, Á. Szollosy, J. Bakos, Appl. Catal. A: Gen.
303 (2006) 29–34.
[13] R.L. Augustine, P. Goel, N. Mahata, C. Reyes, S.K. Tanielyan, J. Mol. Catal. A:
Chem. 216 (2004) 189–197.
[14] B. Yi, Q.H. Fan, G.J. Deng, Y.M. Li, L.Q. Qiu, A.S.C. Chan, Org. Lett. 6 (2004)
1361–1364.
[15] G.J. Deng, Q.H. Fan, X.M. Chen, D.S. Liu, A.S.C. Chan, Chem. Commun. 15 (2002)
1570–1571.
[16] X.P. Hu, J.D. Huang, Q.H. Zeng, Z. Zheng, Chem. Commun. 29 (2006) 3–295.
[17] H.-B. Yu, Q.-S. Hu, L. Pu, Tetrahedron Lett. 41 (2000) 1681–1685.
[18] L. Pu, Chem. Rev. 98 (1998) 2405–2494.
[19] Y. Otomaru, T. Senda, T. Hayashi, Org. Lett. 6 (2004) 3357–3359.
[20] W.-S. Huang, Q.-S. Hu, L. Pu, J. Org. Chem. 64 (1999) 7940–7956.
[21] A. Zhang, L. Yang, N. Yang, Y. Liu, Tetrahedron: Asymmetry 25 (2014) 289–297.
[22] A.-L. Zhang, L.-W. Yang, N.-F. Yang, D.-C. Liu, J. Organomet. Chem. 768 (2014)
50–55.
[23] A. Zhang, N. Yang, L. Yang, D. Peng, Chem. Lett. 43 (2014) 462–464.
[24] C. Huang, N. Yang, A. Zhang, L. Yang, Polymer 53 (2012) 3514–3519.
[25] R.R. Milburn, S.M.S. Hussain, O. Prien, Z. Ahmed, V. Snieckus, Org. Lett. 9
(2007) 4403–4406.
[26] R. Takita, K. Yakura, T. Ohshima, M. Shibasaki, J. Am. Chem. Soc. 127 (2005)
13760–13761.
[35] H. Sellner, C. Faber, P.B. Rheiner, D. Seebach, Chem. Eur. J. 6 (2000) 3692–3705.
[36] D. Jayaprakash, H. Sasai, Tetrahedron: Asymmetry 12 (2001) 2589–2595.
[37] H.C. Brown, P.K. Jadhav, B. Singaram, in: R. Scheffold (Ed.), Modern Synthetic
Methods, 4, Springer, Heidelberg, 1986, pp. 307–356.
[38] P.V. Ramachandran, H.C. Brown, S. Pitre, Org. Lett. 3 (2001) 17–18.
[39] H. Zhou, S. Lu, R. Xie, A.S.C. Chan, T.K. Yang, Tetrahedron Lett. 42 (2001)
1107–1110.
[40] G. Delogu, D. Fabbri, C. Candia, A. Patti, S. Pedotti, Tetrahedron: Asymmetry 13
(2002) 891–898.
[41] B.T. Cho, O.K. Choi, D.J. Kim, Tetrahedron: Asymmetry 13 (2002) 697–703.
[42] C. Recsei, C.S.P. McErlean, Tetrahedron 68 (2012) 464–480.
[43] F. Yang, S. Wei, C.-A. Chen, P. Xi, L. Yang, J. Lan, H.-M. Gau, J. You, Chem. Eur. J.
14 (2008) 2223–2231.
[44] D. Zhao, N. Wu, S. Zhang, P. Xi, X. Su, J. Lan, J. You, Angew. Chem. Int. Ed. 48
(2009) 8729–8732.
[45] J.X. Xu, T.Z. Wei, Q.H. Zhang, J. Org. Chem. 68 (2003) 10146–10151.
[46] J.X. Xu, T.Z. Wei, Q.H. Zhang, J. Org. Chem. 69 (2004) 6860–6866.
[47] J.-J. Du, Z.-Y. Li, D.-M. Du, J.X. Xu, J. Mol. Catal. A: Chem. 284 (2008)
40–45.
[48] Y.-N. Niu, Z.-Y. Yan, G.-Q. Li, H.-L. Wei, G.-L. Gao, L.-Y. Wu, Y.-M. Liang,
Tetrahedron: Asymmetry 19 (2008) 912–920.
[49] J. Xu, X. Su, Q. Zhang, Tetrahedron: Asymmetry 14 (2003) 1781–1786.
[50] X.-F. Wu, C. Min, E. Nyamzundui, H.-B. Zhou, C. Dong, Tetrahedron:
Asymmetry 22 (2011) 1640–1643.
[27] V. Annamalai, E.F. DiMauro, P.J. Carroll, M.C. Kozlowski, J. Org. Chem. 68
(2003) 1973–1981.
[28] E.F. DiMauro, M.C. Kozlowski, Organometallics 21 (2002) 1454–1461.
[29] H. Sasai, T. Suzuki, N. Itoh, J.K. Tanaka, T. Date, K. Okamura, M. Shibasaki, J.
Am. Chem. Soc. 115 (1993) 10372–10373.
[30] D.V. Gribkov, K.C. Hultzsch, F. Hampel, J. Am. Chem. Soc. 128 (2006)
3748–3759;1;.
[31] S. Kobayashi, K. Kusakabe, H. Ishitani, Org. Lett. 2 (2000) 1225–1227.
[32] B.H. Lipshutz, Y.J. Shin, Tetrahedron Lett. 41 (2000) 9515–9521.
[33] S. Matsunaga, T. Ohshima, M. Shibasaki, Tetrahedron Lett. 41 (2000)
8473–8478.
[51] H.-H.J. Zou. Hu, J. Zhang, J.-S. You, D. Ma Lü, J. Mol. Catal. A: Chem. 242 (2005)
57–61.
[52] D.-M. Du, T. Fang, J. Xu, S.-W. Zhang, Org. Lett. 8 (2006) 1327–1330.
[53] Y.-M. Lin, I.-P. Fu, B.-J. Uang, Tetrahedron: Asymmetry 12 (2001) 3217–3221.
[54] G.-Q. Li, Z.-Y. Yan, Y.-N. Niu, L.-Y. Wu, H.-L. Wei, Y.-M. Liang, Tetrahedron:
Asymmetry 19 (2008) 816–821.
[55] E.J. Corey, C.J. Helal, Angew. Chem. Int. Ed. Engl. 37 (1998) 1986.
[56] Y.-X. Zhang, D.-M. Du, X. Chen, S.-F. Lü, W.-T. Hua, Tetrahedron: Asymmetry
15 (2004) 177–182.
[34] X. Yang, W. Su, D. Liu, H. Wang, J. Shen, C. Da, R. Wang, A.S.C. Chan,
Tetrahedron 56 (2000) 3511–3516.
[57] D. Basavaiah, K.V. Rao, B.S. Reddy, Tetrahedron: Asymmetry 18 (2007)
968–974.