Synthesis of novel chiral tridentate aminophenol ligands for enantioselective addition of diethylzinc to aldehydes

Article abstract of DOI:10.1016/j.tetasy.2008.06.027

Novel chiral tridentate aminophenol ligand (S)-3a was obtained by a Mannich-type reaction of cresol, paraformaldehyde, and (S)-1-(2-methoxyphenyl)-2-methylpropan-1-amine followed by a deprotection step. This tridentate aminophenol ligand shows high yield and enantioselectivity in the diethylzinc additions to a broad range of substrates, including alkyl, aryl, and α,β-unsaturated aldehydes.

Full text of DOI:10.1016/j.tetasy.2008.06.027

Tetrahedron: Asymmetry 19 (2008) 1670–1675
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Tetrahedron: Asymmetry
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Synthesis of novel chiral tridentate aminophenol ligands for
enantioselective addition of diethylzinc to aldehydes
b
Xiao-Feng Yang a,b, Takuji Hirose a, , Guang-You Zhang
*
a Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakura, Saitama 338-8570, Japan
b Department of Chemical Engineering, University of Jinan, 106 Jiwei Road, Jinan, Shandong Province 250022, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Novel chiral tridentate aminophenol ligand (S)-3a was obtained by a Mannich-type reaction of cresol,
paraformaldehyde, and (S)-1-(2-methoxyphenyl)-2-methylpropan-1-amine followed by a deprotection
step. This tridentate aminophenol ligand shows high yield and enantioselectivity in the diethylzinc addi-
Received 3 May 2008
Accepted 18 June 2008
Available online 28 July 2008
tions to a broad range of substrates, including alkyl, aryl, and
a
,b-unsaturated aldehydes.
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
(S)-19 followed by a deprotection step7 (Scheme 1). These ligands
are stable in air.
Over the last two decades, there has been a great deal of interest
in the synthesis of chiral ligands which work for the catalytic
asymmetric addition of diethylzinc to aldehydes since the first re-
port of Oguni.1 Most of the chiral ligands are based upon chiral
bidentate aminoalcohols,2 diols,3 and diamine derivatives.4 How-
ever, chiral tridentate ligands that effectively catalyze the diethyl-
zinc addition with high levels of enantioselectivity have scarcely
been reported.5 On the other hand, approximately 600 chiral li-
gands for the asymmetric addition reactions have been shown in
recent reviews6a–c and reports,6d–q although only a small number
of effective ligands were obtained by simple synthetic methods.
Furthermore, ligands suitable for the addition reactions to both
To investigate the catalytic properties of these two ligands, the
asymmetric addition of diethylzinc to benzaldehyde was first car-
ried out (Table 1). The tridentate aminophenol ligand 3a was cho-
sen for the initial experiments (Table 1, entries 1–8). The solvent
played an important role in the enantioselective process (Table 1,
entries 1–4). Toluene or toluene/hexane (1:1, v/v) gave the best re-
sults with 98%, 96% yields and 96%, 95% ee, respectively (Table 1,
entries 1 and 2). The presence of CH2Cl2 or THF lowered the ee va-
lue of the resulting alcohol (Table 1, entries 3 and 4). Therefore, tol-
uene was selected as the reaction solvent in the following
reactions. Optimization of the reaction temperature indicated that
room temperature favored a higher ee (Table 1, entries 1 and 5–7).
On the other hand, in the presence of 5 mol % of 3a the ee value of
the resulting alcohol decreases (Table 1, entry 8). The reaction con-
ditions of entry 1 were chosen as the optimal conditions for the fol-
lowing reactions. We also investigated the catalytic properties of
3b. Under the reaction condition optimized for 3a, the ethylation
using 3b providing 53% ee was quite slow, and 16% of the starting
benzaldehyde remained unreacted after 18 h (Table 1, entry 5).
With the above optimal results, ligand 3a was further used in
the asymmetric addition of diethylzinc to other aromatic alde-
hydes (Table 2, entries 2–13). Fortunately, 3a showed excellent
enantioselectivity of >93% ee for various tested naphthaldehydes
and para-, meta-, and ortho-substituted benzaldehydes, except
ortho-chloro and ortho-bromo benzaldehydes. Usually it is as-
sumed that the diethylzinc addition involves a transition state,
which is a Zn-complex containing the corresponding ligand and
the coordinated carbonyl compound.2c,10 A higher electronegative
substitution at the ortho-position of benzaldehyde would have a
great influence on the coordination of the carbonyl compound
to the Zn center possibly due to the electrostatics in this
complex. Therefore, ortho-chloro or ortho-bromo substitution has
aromatic and aliphatic or
a,b-unsaturated aldehydes are rare.
Therefore, easily accessible, stable, operationally simple, and effec-
tive ligands are still desirable. Herein, we report novel chiral tri-
dentate aminophenol ligands obtained by introducing another
phenolic hydroxyl group from cresol into a chiral aminophenol7
using a Mannich-type reaction for the asymmetric addition of
diethylzinc to aldehydes. The key features of these ligands include
(a) ease of preparation and high stability; (b) the ability to operate
at room temperature; and (c) versatility for a variety of aldehydes
to afford the high ee products with high chemical yields.
2. Results and discussion
Chiral tridentate aminophenol ligands 3 can be easily be ob-
tained by Mannich reaction8 of cresol, paraformaldehyde, and
* Corresponding author. Tel./fax: +81 48 858 3522.
E-mail address: hirose@apc.saitama-u.ac.jp (T. Hirose).
0957-4166/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2008.06.027

X.-F. Yang et al. / Tetrahedron: Asymmetry 19 (2008) 1670–1675
1671
R1
R1
OH
O
NH2
a, b
c
R1
N
H
OH
+
N
H
O
OH HO
3
1
2
1a: R1 = iPr
2a: R1 = iPr
3a: R1 = iPr
1b: R1 = tBu
2b: R1 = tBu
3b: R1 = tBu
Scheme 1. Synthesis of chiral tridentate aminophenol ligands 3. Reagents and conditions: (a) paraformaldehyde, LiCl/EtOH, reflux, 20 h; (b) NH2OHꢀHCl/MeOH, two steps,
55% overall yield; (c) AlBr3/dry toluene, 0 °C, 50 h, 92%.
Table 1
Table 2
Enantioselective addition of diethylzinc to benzaldehyde catalyzed by chiral ligands
Enantioselective addition of diethylzinc to aldehydes catalyzed by the chiral ligand
3a–ba
3aa
Entry
Aldehyde (R2CHO)
Time (h)
Yieldb (%)
eeh (%)
O
H
chiral ligand
96c (R)
93f (R)
94d (R)
93d (R)
98d (R)
93f (+)
94c (R)
96c (R)
80c (R)
60c (R)
96c (R)
95e (R)
96e (R)
85f (R)
92f (R)
95e (R)
94e (R)
92g (R)
OH
Et
+
Et2Zn
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
C6H5CHO
3
3
3
3
3
3
3
3
3
3
3
2
2
2
2
3
3
4
98
80
98
95
97
87
95
92
92
93
95
93
97
96
98
81
98
82
Ph
H
Ph
p-NO2C6H4CHO
p-ClC6H4CHO
p-BrC6H4CHO
p-MeC6H4CHO
m-NO2C6H4CHO
m-ClC6H4CHO
m-MeC6H4CHO
o-ClC6H4CHO
o-BrC6H4CHO
o-MeC6H4CHO
Entry
Ligand
Reaction conditions
Yieldb (%)
eec,d (%)
1
2
3
4
5
6
7
8e
9
3a
3a
3a
3a
3a
3a
3a
3a
3b
Toluene, rt, 3 h
Toluene/hexane, rt, 3 h
CH2Cl2, rt, 14 h
98
96
82
10
97
90
—
96 (R)
95 (R)
88 (R)
3 (R)
92 (R)
94 (R)
—
THF, rt, 24 h
Toluene, 60 °C, 2 h
Toluene, 0–5 °C, 7 h
Toluene, ꢁ20 °C, 48 h
Toluene, rt, 3 h
a
-Naphthaldehyde
98
78
91 (R)
53 (R)
b-Naphthaldehyde
2-Furaldehyde
2-Thiophenealdehyde
C6H5CH2CH2CHO
E-C6H5CH@CHCHO
n-C9H19CHO
Toluene, rt, 18 h
a
Molar ratio PhCHO/Et2Zn/chiral ligand 3 = 1:1.2:0.1.
Isolated yields.
Based on HPLC analysis using Chiralcel OB-H.
b
c
d
The configuration of the main enantiomer was assigned according to the value
of the specific rotation.
a
e
Molar ratio aldehyde/Et2Zn/chiral ligand 3a = 1:1.2:0.1; reaction conditions:
In the presence of 5 mol % of 3a.
toluene, rt.
b
c
d
e
f
Isolated yields.
Based on HPLC analysis using Chiralcel OB-H.
Based on HPLC analysis using Chiralcel OJ.
Based on HPLC analysis using Chiralcel OD-H.
Based on HPLC analysis of its benzoate derivative using Chiralcel AD-H.
Based on HPLC analysis of its benzoate derivative using Chiralcel OD-H.
The configuration of the main enantiomer was assigned according to the value
an electrostatic effect in this complex besides steric hindrance
while ortho-methyl substitution has only steric hindrance, result-
ing in the difference of the substitution effect on the ee value
(80% ee for ortho-chlorobenzaldehyde, 60% ee for ortho-bromo-
benzaldehyde, and 96% ee for ortho-methylbenzaldehyde). The
heterocyclic aromatic aldehydes, 2-furaldehyde and 2-thiophene-
aldehyde provided (R)-1-furyl-1-propanol (96% yield, 85% ee) and
(R)-1-thienyl-1-propanol (98% yield, 92% ee) in good to excellent
enantioselectivity (Table 2, entries 13 and 14). It is known that in
the diethylzinc addition reaction, the enantioselectivity is usually
g
h
of the specific rotation.
lenging substrates. Apparently, excellent enantioselectivities were
observed with 92–95% ee (Table 2, entries 15–17). In comparison
with other tridentate ligands5 (Fig. 1), the following features of
the ligand 3a are noted: (1) For aromatic aldehydes, ligand 3a dis-
plays stereoselectivities of similar magnitude as ligand 6,5f and
higher than ligands 4,5a 5,5b 7,5c and 8;5g (2) for aliphatic (entries
much lower for aliphatic and a,b-unsaturated aldehydes than the
identical reaction with aromatic aldehydes. Compound 3a was
next examined in the addition of diethylzinc to these more chal-
tBu
Ph
OH
H
H
Ph
tBu
N
H
OH
Ph
Ph
tBu
N
H
N
OH
N
OH
tBu
OH
6
4
5
O
nBu
Ph
Pr
H
Ph
N
N
O
OH
OH
HN
HO
OH
7a
OH
7b
Ph
Ph
8
Figure 1.

1672
X.-F. Yang et al. / Tetrahedron: Asymmetry 19 (2008) 1670–1675
15 and 17) and
a,b-unsaturated (entry 16) aldehydes, ligand 3a
iPr
H
iPr
H
(95% ee, 92% ee, and 94% ee) shows higher enantioselecitivities
than those of ligands 55b and 65f (70–83% ee); (3) the catalytic
activities of ligand 3a appear to be higher than the other tridentate
ligands since the aldehydes required only 2–4 h at room tempera-
ture for complete conversion.
Et2Zn
N
N
Et2Zn
H
H
O
O
Zn
HO
PhCHO
OH
A
3a
The catalytic properties of ligand 3a were also examined for the
enantioselective additions of diphenylzinc to p-tolualdehyde and
phenylacetylene to benzaldehyde to provide the corresponding
alcohols in moderate to high yields but with only 4% and 6% ee,
respectively (Scheme 2).
iPr
H
O
Pri
H
Et
H
N
O
Zn
H
H
N
Zn
O
O
Zn
3a (10 mol%)
O
Zn Et
O
O
OH
Et2Zn (1.2 equiv)
H
Ph2Zn (0.6 equiv)
H
Ts-1-Re
toluene, r.t.
Ts-2-Si
56% yield
4% ee
B
C
3a (10 mol%)
Et2Zn (2.2 equiv)
O
OH
OZnEt
OZnEt
Ph
H
H
(2.4 equiv)
toluene, r.t.
Ph
Et
(R)
Ph
Et
(S)
94% yield
6% ee
iPr
H
iPr
H
N
Scheme 2. Phenylation of p-tolualdehyde and phenylethynylation of benzaldehyde
using tridentate ligand 3a.
N
H
O
O
O
O
Zn
H
Zn
O
The currently accepted mechanism for the addition of dialkyl-
zinc to aldehydes2c,10 has been reviewed and applied to the present
system. In analogy to that established by Noyori and Yamakawa10c
for b-amino alcohol, an O,N,O-chelating six/six bicyclic zinc-com-
plex A is formed initially by the reaction of aminophenol (S)-3a
with diethylzinc. Once a new molecule of diethylzinc and aldehyde
coordinated, there were four possible forms of the 6/4/4 tricyclic
transition states (B–E) (Fig. 2). The transition states of the type D
and E should be less likely because of the increased steric hin-
Et Zn
O
Zn
Et
H
H
Ts-3-Si
Ts-4-Re
D
E
OZnEt
Ph
OZnEt
i
drance between the Pr group and the O–Zn–O–Zn ring structure.
Et
Et
Ph
Between the transition states of the type B and C, the most ener-
getically favorable should be type B, in which the aromatic ring
of the benzaldehyde is oriented far from the hindered ligand ‘cage’;
(R)-alcohol is thus preferentially formed.
(S)
(R)
Figure 2.
3. Conclusions
purchased at the highest quality and were purified by distillation
when necessary. Hexane and toluene were distilled and stored
on sodium wire before use.
2-(((S)-1-(2-Methoxyphenyl)-2-methylpropylamino)methyl)-4-
methylphenol (S)-2a and 2-(((S)-1-(2-methoxyphenyl)-2,2-
dimethylpropylamino)methyl)-4-methylphenol (S)-2b were syn-
thesized according to a literature procedure.8
In conclusion, we have prepared a new chiral tridentate amino-
phenol ligand 3a for the enantioselective addition of diethylzinc to
aldehydes. This tridentate aminophenol ligand provides good to
excellent yields and enantioselectivities in the reactions of diethyl-
zinc with a broad range of aromatic, aliphatic, and unsaturated
aldehydes.
4.1. Characterization of 2-(((S)-1-(2-methoxyphenyl)-2-
methylpropylamino)methyl)-4-methylphenol (S)-2a
4. Experimental
1H NMR spectra were recorded on Bruker AC300 or
DPX400 MHz in Molecular Analysis and Life Science Center (Sai-
tama University). The chemical shifts were reported in ppm down-
field from Me4Si in CDCl3 solution and the coupling constants were
given in Hertz. IR spectra were recorded on JASCO FT/IR 400. Enan-
tiomeric excess determination was carried out using a set of JASCO
LC 900 series with chiral columns. Optical rotations were measured
with a JASCO DIP-370 polarimeter. Melting points were deter-
mined with a Mitamura Riken Kogyo MEL-TEMP instrument and
are reported uncorrected. All commercially available reagents were
A yellow oil. ½a 2D3
¼ ꢁ18:6 (c 0.582, CHCl3). Enantiomeric purity
ꢂ
>99% ee was determined by HPLC analysis (CHIRALCEL OJ, 10% IPA
in hexane, 0.5 ml/min, 254 nm UV detector) at retention time:
t = 16.59 min. 1H NMR (400 MHz, CDCl3): d 7.29–7.25 (m, 1H, Ar),
7.05 (d, J = 7.2 Hz, 1H, Ar), 6.95–6.90 (m, 3H, Ar), 6.75 (d,
J = 8.4 Hz, 1H, Ar), 6.61 (s, 1H, ArCH2), 3.81 (s, 3H, ArOCH3), 3.69
(d, J = 13.6 Hz, 1H, ArCH), 3.54 (d, J = 13.6 Hz, 1H, ArCH2), 3.46 (d,
J = 8.8 Hz, 1H, ArCH2), 2.19 (s, 3H, ArCH3), 2.14–2.10 (m, 1H,
(CH3)2CH), 1.09 (d, J = 6.4 Hz, 3H, (CH3)2CH), 0.71 (d, J = 6.8 Hz,
3H, (CH3)2CH). 13C NMR (100 MHz, CDCl3): d 157.5 (Ar, COCH3),

X.-F. Yang et al. / Tetrahedron: Asymmetry 19 (2008) 1670–1675
1673
156.0 (Ar, COH), 129.8 (Ar, CH), 128.9 (Ar, C), 128.8 (Ar, CH), 128.2
(Ar, C), 127.7 (Ar, C), 122.8 (Ar, CH), 120.5 (Ar, CH), 115.9 (Ar, CH),
110.7 (Ar, CH), 55.2 (OCH3), 50.8 (ArCH), 32.2 ((CH3)2CH), 20.6
(ArCH3), 20.3 ((CH3)2CH), 20.3 ((CH3)2CH). IR (neat): 3349, 2956,
2923, 2871, 1829, 1792, 1771, 1717, 1684, 1671, 1652, 1635,
1617, 1599, 1576, 1520, 1419, 1397, 1362, 1338, 1084, 893, 815,
768 cmꢁ1. Anal. Calcd for C19H25NO2: C, 76.22; H, 8.42; N, 4.68.
Found: C, 76.11; H, 8.48; N, 4.46.
(Ar, C), 128.4 (Ar, C), 124.0 (Ar, C), 118.4 (Ar, CH), 116.7 (Ar, CH),
115.5 (Ar, CH), 65.9 (ArCH), 48.4 (ArCH2), 35.9 ((CH3)3C), 27.0
(ArCH3), 20.4 ((CH3)3C), 15.2 ((CH3)3C). IR (KBr): 2954, 2867,
2954, 2867, 1942, 1918, 1868, 1844, 1828, 1792, 1771, 1749,
1733, 1717, 1698, 1684, 1671, 1652, 1635, 1590, 1558, 1540,
1473, 1366, 1223, 1151, 1122, 1106, 1080, 1035, 943, 906,
816 cmꢁ1. Anal. Calcd for C19H25NO2: C, 76.22; H, 8.42; N, 4.68.
Found: C, 76.03; H, 8.42; N, 4.53.
4.2. Characterization of 2-(((S)-1-(2-methoxyphenyl)-2,2-
dimethylpropylamino)methyl)-4-methylphenol (S)-2b
4.5. Asymmetric addition of diethylzinc to aldehydes
4.5.1. General procedure for the enantioselective addition of
diethylzinc to aldehydes catalyzed by chiral ligands
A white solid. Mp: 142–144 °C. ½a D23
¼ þ6:6 (c 0.696, CHCl3).
ꢂ
Diethylzinc (1.2 ml, 1.0 M solution in hexane) was added to a
stirred solution of chiral ligand (0.1 mmol) in toluene (1.5 ml) un-
der N2 at room temperature. After stirring for 1 h, a solution of
aldehyde (1 mmol) in toluene (3.0 ml) was added dropwise. The
resulting mixture was monitored by TLC and when no more trace
of the aldehyde was detected, the reaction mixture was quenched
by saturated NH4Cl solution. The mixture was extracted three
times with ethyl acetate. The combined extracts were dried with
anhydrous Na2SO4. After filtering and concentration, the residue
was purified by TLC of silica gel to give the enantiomerically en-
riched alcohol. The ee values of the alcohol were determined by
chiral HPLC analysis.
Enantiomeric purity >99% ee was determined by HPLC analysis
(CHIRALCEL OJ, 10% IPA in hexane, 0.5 ml/min, 254 nm UV detec-
tor) at retention time: t = 14.13 min. 1H NMR (400 MHz, CDCl3): d
7.25–7.18 (m, 2H, Ar), 7.00–6.90 (m, 3H, Ar), 6.78 (d, J = 8.4 Hz,
1H, Ar), 6.63 (s, 1H, Ar), 4.20 (s, 1H, ArCH), 3.79 (s, 1H, ArOCH3),
3.67 (dd, J = 13.6 Hz, J = 33.6 Hz, 1H, ArCH2), 3.53 (d, J = 13.6 Hz,
1H, ArCH2), 2.19 (s, 3H, ArCH3), 0.94 (s, 9H, (CH3)3C). 13C NMR
(100 MHz, CDCl3): d 158.5 (Ar, COCH3), 155.7 (Ar, COH), 128.9
(Ar, C), 128.8 (Ar, CH), 128.2 (Ar, CH), 127.9 (Ar, C), 126.8 (Ar,
CH), 123.0 (Ar, C), 120.3 (Ar, CH), 115.9 (Ar, CH), 110.6 (Ar, CH),
61.7 (ArCH), 55.3 (ArOCH3), 51.2 (ArCH2), 35.2 ((CH3)3C), 28.2
(ArCH3), 26.6 ((CH3)3C), 20.3 ((CH3)3C). IR (KBr): 3306, 2931,
2870, 1868, 1844, 1792, 1771, 1733, 1717, 1684, 1670, 1652,
1635, 1598, 1558, 1540, 1521, 1474, 1457, 1419, 1339, 1291,
1187, 1125, 1056, 974, 881, 753 cmꢁ1. Anal. Calcd for C20H27NO2:
C, 76.64; H, 8.68; N, 4.47. Found: C, 76.32; H, 8.76; N, 4.13.
Chiral tridentate aminophenol ligands (S)-3a and (S)-3b were
synthesized according to a literature procedure.7
4.5.2. (R)-1-Phenyl-1-propanol
98% isolated yield. 96% ee determined by HPLC analysis (Chiral-
cel OB-H column, 10% IPA in hexane, 0.5 ml/min, 254 nm UV detec-
tor). Retention time: t = 14.47 min ((S)-isomer: t = 12.52 min).
½
a 2D3
ꢂ
¼ þ42:5 (c 0.49, CHCl3) (lit.5e
½
a 2D9
ꢂ
¼ þ41:9 (c 1.00, CHCl3),
96% ee for (R)). 1H NMR (400 MHz, CDCl3): d 7.27–7.16 (m, 5H),
4.76 (t, J = 6.4 Hz, 1H), 2.01 (s, 1H), 1.77–1.59 (m, 2H), 0.97 (t,
J = 7.2 Hz, 3H). 13C NMR (100 MHz, CDCl3): d 144.6, 128.3, 127.4,
125.9, 75.9, 31.8, 10.1.
4.3. Characterization of 2-((S)-1-(2-hydroxy-5-
methylbenzylamino)-2-methylpropyl)phenol (S)-3a
A white solid. Mp: 44–46 °C. ½a D23
¼ ꢁ19:0 (c 0.4, CHCl3). Enan-
ꢂ
tiomeric purity >99% ee was determined by HPLC analysis (CHI-
RALCEL OJ, 10% IPA in hexane, 0.5 ml/min, 254 nm UV detector)
at retention time: t = 19.32 min. 1H NMR (400 MHz, CDCl3): d
7.18–7.14 (m, 1H, Ar), 6.96–6.91 (m, 2H, Ar), 6.84–6.73 (m, 2H,
Ar), 6.72 (d, J = 8.4 Hz, 1H, Ar), 3.85 (d, J = 13.2 Hz, 1H, ArCH),
3.55 (d, J = 13.2 Hz, 1H, ArCH2), 3.45 (d, J = 7.2 Hz, 1H, ArCH2),
2.23 (s, 3H, ArCH3), 2.05–2.01 (m, 1H, (CH3)2CH), 0.98 (d,
J = 6.8 Hz, 3H, (CH3)2CH), 0.80 (d, J = 6.8 Hz, 3H, (CH3)2CH). 13C
NMR (100 MHz, CDCl3): d 157.0 (Ar, COH), 152.7 (Ar, COH), 131.2
(Ar, C), 130.2 (Ar, C), 129.5 (Ar, CH), 129.3 (Ar, CH), 128.3 (Ar,
CH), 124.2 (Ar, CH), 124.0 (Ar, C), 119.0 (Ar, CH), 116.5 (Ar, CH),
115.6 (Ar, CH), 68.8 (ArCH), 48.4 (ArCH2), 33.2 ((CH3)2CH), 20.4
(ArCH3), 19.9 ((CH3)2CH), 19.3 ((CH3)2CH). IR (KBr): 2960, 2923,
2871, 1868, 1844, 1829, 1792, 1771, 1733, 1698, 1684, 1652,
1635, 1616, 1558, 1540, 1507, 1456, 1078, 816, 754 cmꢁ1. Anal.
Calcd for C18H23NO2: C, 75.76; H, 8.12; N, 4.91. Found: C, 75.53;
H, 8.25; N, 4.69.
4.5.3. (R)-1-(4-Nitrophenyl)-1-propanol
80% isolated yield. 93% ee determined by HPLC analysis of its
benzoate (Chiralcel AD-H column, 10% IPA in hexane, 0.5 ml/min,
254 nm UV detector). Retention time: t = 19.35 min ((S)-isomer:
t = 42.16 min). ½a D23
ꢂ
¼ þ26:8 (c 0.32, CHCl3) (lit.6p
½
a 1D6
ꢂ
¼ ꢁ15:2 (c
1.52, CHCl3), 47% ee). 1H NMR (400 MHz, CDCl3): d 8.19 (d,
J = 8.8 Hz, 2H), 7.51 (d, J = 8.8 Hz, 2H), 4.75 (t, J = 6.4 Hz, 1H),
1.81–1.77 (m, 2H), 0.94 (t, J = 7.2 Hz, 3H). 13C NMR (100 MHz,
CDCl3): d 151.9, 147.2, 126.6, 123.6, 74.8, 32.1, 9.7.
4.5.4. (R)-1-(4-Cholorophenyl)-1-propanol
98% isolated yield. 94% ee determined by HPLC analysis (Chiral-
cel OJ column, 3% IPA in hexane, 0.5 ml/min, 254 nm UV detector).
Retention time: t = 34.31 min ((S)-isomer: t = 32.58 min). ½a D23
¼
ꢂ
þ36:0 (c 0.8, CHCl3) (lit.6e
½
a 2D5
ꢂ
¼ þ37:3 (c 1.57, CHCl3), 96% ee
for (R)). 1H NMR (400 MHz, CDCl3): d 7.29 (d, J = 8.4 Hz, 2H), 7.24
(d, J = 8.8 Hz, 2H), 4.55 (t, J = 6.4 Hz, 1H), 2.12 (s, 1H), 1.80–1.66
(m, 2H), 0.88 (t, J = 7.2 Hz, 3H). 13C NMR (100 MHz, CDCl3): d
142.9, 133.0, 128.4, 127.3, 75.2, 31.9, 9.9.
4.4. Characterization of 2-((S)-1-(2-hydroxy-5-
methylbenzylamino)-2,2-dimethylpropyl)phenol (S)-3b
A white solid. Mp: 63–65 °C. ½a D23
¼ ꢁ22:5 (c 0.516, CHCl3).
ꢂ
4.5.5. (R)-1-(4-Bromophenyl)-1-propanol
95% isolated yield. 93% ee determined by HPLC analysis (Chiral-
cel OJ column, 3% IPA in hexane, 0.5 ml/min, 254 nm UV detector).
Enantiomeric purity >99% ee was determined by HPLC analysis
(CHIRALCEL OJ, 10% IPA in hexane, 0.5 ml/min, 254 nm UV detec-
tor) at retention time: t = 17.49 min. 1H NMR (400 MHz, CDCl3): d
7.11–7.07 (m, 1H, Ar), 6.89–6.83 (m, 2H, Ar), 6.78–6.70 (m, 3H,
Ar), 6.65 (d, J = 4.0 Hz, 1H, Ar), 3.78 (d, J = 12.8 Hz, 1H, ArCH),
3.44 (d, J = 12.8 Hz, 1H, ArCH2), 3.36 (s, 1H, ArCH2), 2.15 (s, 3H,
ArCH3), 0.85 (s, 9H, (CH3)3C). 13C NMR (100 MHz, CDCl3): d 157.9
(Ar, COH), 152.5 (Ar, COH), 131.5 (Ar, CH), 129.6 (Ar, CH), 129.4
Retention time: t = 40.05 min ((S)-isomer: t = 36.74 min). ½a D23
¼
ꢂ
þ15:0 (c 0.894, benzene) (lit.6j
½
a 2D5
ꢂ
¼ þ15:8 (c 1.49, benzene),
90.3% ee for (R)). 1H NMR (400 MHz, CDCl3): d 7.45 (d, J = 8.4 Hz,
2H), 7.20 (d, J = 8.4 Hz, 2H), 4.55 (t, J = 6.4 Hz, 1H), 2.03 (s, 1H),
1.79–1.68 (m, 2H), 0.89 (t, J = 7.2 Hz, 3H). 13C NMR (100 MHz,
CDCl3): d 143.5, 131.4, 127.7, 121.1, 75.2, 31.9, 9.9.

1674
X.-F. Yang et al. / Tetrahedron: Asymmetry 19 (2008) 1670–1675
4.5.6. (R)-1-4-Tolyl-1-propanol
4.5.12. (R)-1-2-Tolyl-1-propanol
97% isolated yield. 98% ee determined by HPLC analysis (Chiral-
cel OJ column, 3% IPA in hexane, 0.5 ml/min, 254 nm UV detector).
96% isolated yield. 96% ee determined by HPLC analysis (Chiral-
cel OB-H column, 5% IPA in hexane, 0.5 ml/min, 254 nm UV detec-
tor). Retention time: t = 16.08 min ((S)-isomer: t = 14.16 min).
Retention time: t = 34.82 min ((S)-isomer: t = 32.30 min). ½a D23
¼
ꢂ
þ41:2 (c 0.432, benzene) (lit.11
[a
]
D = +39.2 (c 5, benzene), 96% ee
½
a 2D3
ꢂ
¼ þ65:2 (c 0.77, benzene) (lit.11
[a]D = +58.5 (c 2, benzene),
for (R)). 1H NMR (400 MHz, CDCl3): d 7.21 (d, J = 8.0 Hz, 2H), 7.14
(d, J = 8.0 Hz, 2H), 4.52 (t, J = 6.4 Hz, 1H), 2.33 (s, 3H), 2.00 (s,
1H), 1.81–1.69 (m, 2H), 0.89 (t, J = 7.2 Hz, 3H). 13C NMR
(100 MHz, CDCl3): d 141.6, 137.0, 129.0, 125.9, 75.8, 31.7, 21.1,
10.1.
>99% ee for (R)). 1H NMR (400 MHz, CDCl3): d 7.36 (d, J = 7.6 Hz,
1H), 7.16–7.03 (m, 3H), 4.76 (t, J = 6.4 Hz, 1H), 2.25 (s, 3H), 1.81
(s, 1H), 1.70–1.63 (m, 2H), 0.89 (t, J = 7.6 Hz, 3H). 13C NMR
(100 MHz, CDCl3): d 142.7, 134.6, 130.3, 127.1, 126.2, 125.2, 72.0,
30.9, 19.0, 10.3.
4.5.13. (R)-1-(a-Naphthyl)-1-propanol
4.5.7. (3-Nitrophenyl)-1-propanol
93% isolated yield. 95% ee determined by HPLC analysis (Chiral-
cel OD-H column, 10% IPA in hexane, 0.5 ml/min, 254 nm UV
detector). Retention time: t = 35.46 min ((S)-isomer: t =
87% isolated yield. 93% ee determined by HPLC analysis of its
benzoate (Chiralcel AD-H column, 10% IPA in hexane, 0.5 ml/min,
254 nm UV detector). Retention time: tmajor = 15.63 min and
24.42 min). ½a 2D3
ꢂ
¼ þ49:7 (c 0.58, CHCl3) (lit.12
½
a 2D0
ꢂ
¼ þ52:6 (c
tminor = 19.32 min.
½
a 2D3
ꢂ
¼ þ31:3 (c 0.16, CHCl3) (lit.6p
½
a 1D6
ꢂ
¼
2.55, CHCl3), 93.5% ee for (R)). 1H NMR (400 MHz, CDCl3): d 8.08
(d, J = 7.6 Hz, 1H), 7.85 (d, J = 8.8 Hz, 1H), 7.75 (d, J = 8.4 Hz, 1H),
7.60 (d, J = 6.8 Hz, 1H), 7.48–7.43 (m, 3H), 5.35 (t, J = 7.2 Hz, 1H),
2.07 (s, 1H), 2.01–1.86 (m, 2H), 1.00 (t, J = 7.2 Hz, 3H). 13C NMR
(100 MHz, CDCl3): d 140.2, 133.8, 130.5, 128.9, 127.8, 125.9,
125.5, 125.4, 123.2, 122.9, 72.6, 31.1, 10.5.
ꢁ28:3 (c 1.35, CHCl3), >99% ee). 1H NMR (400 MHz, CDCl3): d
8.21 (s, 1H), 8.11 (d, J = 8.0 Hz, 1H), 7.68 (d, J = 8.0 Hz, 1H), 7.51
(d, J = 8.0 Hz, 1H), 4.74 (t, J = 6.4 Hz, 1H), 1.85–1.76 (m, 2H), 0.94
(t, J = 7.2 Hz, 3H). 13C NMR (100 MHz, CDCl3): d 148.3, 146.7,
132.1, 129.3, 122.3, 120.9, 74.7, 32.1, 9.7.
4.5.8. (R)-1-(3-Cholorophenyl)-1-propanol
4.5.14. (R)-1-(b-Naphthyl)-1-propanol
95% isolated yield. 94% ee determined by HPLC analysis (Chiral-
cel OB-H column, 10% IPA in hexane, 0.5 ml/min, 254 nm UV detec-
tor). Retention time: t = 13.63 min ((S)-isomer: t = 12.10 min).
97% isolated yield. 96% ee determined by HPLC analysis (Chiral-
cel OD-H column, 10% IPA in hexane, 0.5 ml/min, 254 nm UV
detector). Retention time: t = 24.01 min ((S)-isomer: t =
a 2D3
ꢂ
¼ þ34:5 (c 0.77, CHCl3) (lit.6e
½
a 2D5
ꢂ
¼ þ32:1 (c 1.30, CHCl3),
21.25 min). ½a 2D3
ꢂ
¼ þ27:0 (c 0.762, benzene) (lit.12
½
a 2D0
ꢂ
¼ þ27:5
½
94% ee for (R)). 1H NMR (400 MHz, CDCl3): d 7.33 (s, 1H), 7.28–
7.18 (m, 3H), 4.55 (t, J = 6.4 Hz, 1H), 2.17 (s, 1H), 1.80–1.68 (m,
2H), 0.90 (t, J = 7.6 Hz, 3H). 13C NMR (100 MHz, CDCl3): d 146.6,
134.3, 129.6, 127.5, 126.1, 124.1, 75.3, 31.9, 9.9.
(c 3.80, benzene), 96.1% ee for (R)). 1H NMR (400 MHz, CDCl3): d
7.73–7.71 (m, 3H), 7.65 (s, 1H), 7.40–7.35 (m, 3H), 4.63 (t,
J = 6.4 Hz, 1H), 2.08 (s, 1H), 1.83–1.70 (m, 2H), 0.83 (t, J = 7.2 Hz,
3H). 13C NMR (100 MHz, CDCl3): d 141.9, 133.2, 132.9, 128.2,
127.9, 127.6, 126.0, 125.7, 124.7, 124.1, 76.0, 31.7, 10.1.
4.5.9. (R)-1-3-Tolyl-1-propanol
4.5.15. (R)-1-Furyl-1-propanol
92% isolated yield. 96% ee determined by HPLC analysis (Chiral-
cel OB-H column, 5% IPA in hexane, 0.5 ml/min, 254 nm UV detec-
tor). Retention time: t = 16.63 min ((S)-isomer: t = 14.25 min).
96% isolated yield. 85% ee determined by HPLC analysis of its
benzoate (Chiralcel AD-H column, 2% IPA in hexane, 0.5 ml/min,
254 nm UV detector). Retention time: t = 13.45 min ((S)-isomer:
½
a 2D3
ꢂ
¼ þ35:6 (c 0.91, CHCl3) (lit.6e
½
a 2D5
ꢂ
¼ þ37:9 (c 1.76, CHCl3),
t = 15.39 min). ½a D23
ꢂ
¼ þ18:5 (c 0.876, CHCl3) (lit.5e
½
a 2D0
ꢂ
¼ þ25:9
95% ee for (R)). 1H NMR (400 MHz, CDCl3): d 7.14 (t, J = 7.6 Hz,
1H), 7.04–6.99 (m, 3H), 4.44 (t, J = 6.4 Hz, 1H), 2.27 (s, 3H), 2.02
(s, 1H), 1.75–1.61 (m, 2H), 0.82 (t, J = 7.6 Hz, 3H). 13C NMR
(100 MHz, CDCl3): d 144.6, 137.9, 128.2, 128.1, 126.6, 123.0, 75.9,
31.8, 21.4, 10.2.
(c 2.10, CHCl3), 90% ee for (R)). 1H NMR (400 MHz, CDCl3): d
7.29–7.28 (m, 1H), 6.25–6.24 (m, 1H), 6.15–6.14 (m, 1H), 4.51 (t,
J = 6.8 Hz, 1H), 2.14 (s, 1H), 1.85–1.73 (m, 2H), 0.86 (t, J = 7.2 Hz,
3H). 13C NMR (100 MHz, CDCl3): d 156.7, 141.8, 110.0, 105.8,
69.1, 28.6, 9.9.
4.5.10. (R)-1-(2-Cholorophenyl)-1-propanol
4.5.16. (R)-1-Thienyl-1-propanol
92% isolated yield. 80% ee determined by HPLC analysis (Chiral-
cel OB-H column, 3% IPA in hexane, 0.5 ml/min, 254 nm UV detec-
tor). Retention time: t = 17.69 min ((S)-isomer: t = 15.97 min).
98% isolated yield. 92% ee determined by HPLC analysis of its
benzoate (Chiralcel AD-H column, 2% IPA in hexane, 0.5 ml/min,
254 nm UV detector). Retention time: t = 15.15 min ((S)-isomer:
a 2D3
ꢂ
¼ þ44:4 (c 0.69, CHCl3) (lit.6p
½
a 1D6
ꢂ
¼ ꢁ50:2 (c 2.10, CHCl3),
t = 20.03 min). ½a D23
ꢂ
¼ þ23:9 (c 0.876, CHCl3) (lit.5e
½
a 2D0
ꢂ
¼ þ26:4
½
92% ee for (S)). 1H NMR (400 MHz, CDCl3): d 7.52 (dd, J = 1.6 Hz,
J = 7.6 Hz, 1H), 7.32–7.25 (m, 2H), 7.20–7.16 (m, 1H), 5.04 (dd,
J = 4.8 Hz, J = 7.6 Hz, 1H), 2.24 (s, 1H), 1.85–1.68 (m, 2H), 0.97 (t,
J = 7.2 Hz, 3H). 13C NMR (100 MHz, CDCl3): d 141.9, 131.9, 129.3,
128.3, 127.1, 126.9, 71.9, 30.4, 10.0.
(c 2.20, CHCl3), 95% ee for (R)). 1H NMR (400 MHz, CDCl3): d
7.24–7.20 (m, 1H), 6.94–6.92 (m, 2H), 4.76 (t, J = 6.8 Hz, 1H), 2.65
(s, 1H), 1.89–1.77 (m, 2H), 0.92 (t, J = 7.6 Hz, 3H). 13C NMR
(100 MHz, CDCl3): d 148.6, 126.4, 124.3, 123.6, 71.5, 32.1, 10.0.
4.5.17. (R)-1-Phenyl-3-pentanol
4.5.11. (R)-1-(2-Bromophenyl)-1-propanol
81% isolated yield. 95% ee determined by HPLC analysis (Chiral-
cel OD-H column, 10% IPA in hexane, 0.5 ml/min, 254 nm UV
detector). Retention time: t = 18.70 min ((S)-isomer: t =
93% isolated yield. 60% ee determined by HPLC analysis (Chiral-
cel OB-H column, 2% IPA in hexane, 0.5 ml/min, 254 nm UV detec-
tor). Retention time: t = 23.51 min ((S)-isomer: t = 21.84 min).
28.69 min). ½a 2D3
ꢂ
¼ ꢁ21:1 (c 0.114, EtOH) (lit.5e
½
a 2D9
ꢂ
¼ ꢁ23:4 (c
½
a 2D3
ꢂ
¼ þ35:5 (c 0.72, benzene) (lit.12
½
a 2D0
ꢂ
¼ þ54:2 (c 2.46, ben-
1.00, EtOH), 81% ee for (R), lit.13
[
a]
D = ꢁ21.2 (c 7.72, EtOH), 94%
zene), 85% ee for (R)). 1H NMR (400 MHz, CDCl3): d 7.53–7.49 (m,
2H), 7.34–7.30 (m, 1H), 7.13–7.09 (m, 1H), 4.99 (t, J = 5.6 Hz, 1H),
2.16 (s, 1H), 1.87–1.64 (m, 2H), 0.99 (t, J = 7.2 Hz, 3H). 13C NMR
(100 MHz, CDCl3): d 143.5, 132.6, 128.7, 127.6, 127.4, 122.1, 74.1,
30.5, 10.0.
ee for (R)). 1H NMR (400 MHz, CDCl3): d 7.31–7.17 (m, 5H), 3.59–
3.53 (m, 1H), 2.84–2.77 (m, 1H), 2.71–2.64 (m, 1H), 1.85–1.66
(m, 2H), 1.59–1.46 (m, 2H), 1.26 (s, 1H), 0.95 (t, J = 7.2 Hz, 3H).
13C NMR (100 MHz, CDCl3): d 142.2, 128.4, 125.8, 72.7, 38.6, 32.1,
30.3, 9.8.

X.-F. Yang et al. / Tetrahedron: Asymmetry 19 (2008) 1670–1675
1675
3. (a) Schmidt, B.; Seebach, D. Angew. Chem., Int. Ed. Engl. 1991, 30, 1321–1323; (b)
Harada, T.; Kanda, K. Org. Lett. 2006, 8, 3817–3819; (c) Hatano, M.; Miyamoto,
T.; Ishihara, K. J. Org. Chem. 2006, 71, 6474–6484.
4. (a) Soai, K.; Niwa, S.; Yamada, Y. Tetrahedron Lett. 1987, 28, 4841–4842; (b)
Richmond, M. L.; Seto, C. T. J. Org. Chem. 2003, 68, 7505–7508; (c) Bayardon, J.;
Sinou, D.; Holczknecht, O.; Mercs, L.; Pozzi, G. Tetrahedron: Asymmetry 2005, 16,
2319–2327.
5. (a) Corey, E. J.; Hannon, F. J. Tetrahedron Lett. 1987, 28, 5237–5240; (b) Corey, E.
J.; Yuen, P.-W.; Hannon, F. J.; Wierda, D. A. J. Org. Chem. 1990, 55, 784–786; (c)
Cherng, Y.-J.; Fang, J.-M.; Lu, T.-J. J. Org. Chem. 1999, 64, 3207–3212; (d)
Goanvic, D. L.; Holler, M.; Pale, P. Tetrahedron: Asymmetry 2002, 13, 119–121;
(e) Danilova, T. I.; Rozenberg, V. I.; Sergeeva, E. V.; Starikova, Z. A.; Bräse, S.
Tetrahedron: Asymmetry 2003, 14, 2013–2019; (f) Tanaka, T.; Yasuda, Y.;
Hayashi, M. J. Org. Chem. 2006, 71, 7091–7093; (g) Kelsen, V.; Pierrat, P.; Gros, P.
C. Tetrahedron 2007, 63, 10693–10697.
4.5.18. (R)-(E)-1-Phenylpent-1-en-3-ol
98% isolated yield. 94% ee determined by HPLC analysis (Chiral-
cel OD-H column, 10% IPA in hexane, 0.5 ml/min, 254 nm UV
detector). Retention time: t = 19.20 min ((S)-isomer: t =
30.03 min). ½a 2D3
ꢂ
¼ þ7:1 (c 0.764, CHCl3) (lit.5e
½
a 2D8
ꢂ
¼ þ6:1 (c
1.01, CHCl3), 75% ee for (R)). 1H NMR (400 MHz, CDCl3): d 7.38–
7.36 (m, 2H), 7.32–7.28 (m, 2H), 7.24–7.20 (m, 1H), 6.55 (d, J =
15.6 Hz, 1H), 6.20 (dd, J = 6.4 Hz, J = 15.6 Hz, 1H), 4.19 (q, J = 6.4
Hz, 1H), 1.69–1.60 (m, 2H), 0.96 (t, J = 7.2 Hz, 3H). 13C NMR
(100 MHz, CDCl3): d 136.7, 132.3, 130.3, 128.5, 127.5, 126.4, 74.3,
30.2, 9.7.
6. (a) Pu, L.; Yu, H.-B. Chem. Rev. 2001, 101, 757–824; (b) Soai, K.; Shibata, T. In
Comprehensive Asymmetric Catalysis; Jacobsen, E. N., Pfaltz, A., Yamamoto, H.,
Eds.; Springer: Berlin, 1999; pp 911–922; (c) Noyori, R. Asymmetric Catalysis in
Organic Synthesis; Wiley: New York, 1994; (d) Bulut, A.; Aslan, A.; Izgü, E. Ç;
Dogan, Ö. Tetrahedron: Asymmetry 2007, 18, 1013–1016; (e) Bisai, A.; Singh, P.
K.; Singh, V. K. Tetrahedron 2007, 63, 598–601; (f) Jiang, F.-Y.; Liu, B.; Dong,
Z.-B.; Li, J.-S. J. Org. Chem. 2007, 692, 4377–4380; (g) Sugiyawa, S.; Aoki, Yn;
Ishii, K. Tetrahedron: Asymmetry 2006, 17, 2847–2856; (h) Hui, A.; Zhang, J.;
Fan, J.; Wang, Z. Tetrahedron: Asymmetry 2006, 17, 2101–2107; (i) Lin, R.-X.;
Chen, C. J. Mol. Catal. A: Chem. 2006, 243, 89–98; (j) Guo, Q.-S.; Liu, B.; Lu, Y.-N.;
Jiang, F.-Y.; Song, H.-B.; Li, J.-S. Tetrahedron: Asymmetry 2005, 16, 3667–3671;
(k) Milburn, R. R.; Shakil Hussain, S. M.; Prien, O.; Ahmed, Z.; Snieckus, V. Org.
Lett. 2007, 9, 4403–4406; (l) Liu, S.; Wolf, C. Org. Lett. 2007, 9, 2965–2968; (m)
Wang, M.-C.; Zhang, Q.-J.; Zhao, W.-X.; Wang, X.-D.; Ding, X.; Jing, T.-T.; Song,
M.-P. J. Org. Chem. 2008, 73, 168–176; (n) Huang, Z.; Lai, H.; Qin, Y. J. Org. Chem.
2007, 72, 1373–1378; (o) Blay, G.; Fernández, I.; Marco-Aleixandre, A.; Pedro, J.
R. Tetrahedron: Asymmetry 2005, 16, 1207–1213; (p) Chen, Y.-J.; Lin, R.-X.;
Chen, C. Tetrahedron: Asymmetry 2004, 15, 3561–3571; (q) Mao, J.; Wan, B.;
Wang, R.; Wu, F.; Lu, S. J. Org. Chem. 2004, 69, 9123–9127.
4.5.19. (R)-3-Dodecanol6o
82% isolated yield. 92% ee determined by HPLC analysis of its
benzoate (Chiralcel OD-H column, 2% IPA in hexane, 0.5 ml/min,
254 nm UV detector). Retention time: t = 10.96 min ((S)-isomer:
t = 9.60 min). 1H NMR (300 MHz, CDCl3): d 3.49–3.42 (m, 1H),
1.60–1.20 (m, 18H), 0.99–0.79 (m, 6H).
4.5.20. (R)-(4-Methylphenyl)phenylmethanol14
56% isolated yield. 4% ee determined by HPLC analysis (Chiralcel
OB-H column, 10% IPA in hexane, 0.5 ml/min, 254 nm UV detector).
Retention time: t = 28.51 min ((S)-isomer: t = 47.31 min). 1H NMR
(400 MHz, CDCl3): d 7.36–7.23 (m, 7H), 7.12–7.11 (m, 2H), 5.36
(s, 1H), 2.32 (s, 3H). 13C NMR (100 MHz, CDCl3): d 142.6, 139.4,
139.3, 137.1, 129.1, 128.3, 127.3, 127.2, 127.1, 79.7, 21.2.
7. (a) Yang, X.-F.; Wang, Z.-H.; Koshizawa, T.; Yasutake, M.; Zhang, G.-Y.; Hirose,
T. Tetrahedron: Asymmetry 2007, 18, 1257–1263; (b) Yang, X.-F.; Hirose, T.;
Zhang, G.-Y. Tetrahedron: Asymmetry 2007, 18, 2668–2673.
4.5.21. (S)-1,3-Diphenyl-prop-2-yn-1-ol7b
94% isolated yield. 6% ee determined by HPLC analysis (Chiralcel
OB-H column, 10% IPA in hexane, 0.5 ml/min, 254 nm UV detector).
Retention time: t = 52.33 min ((R)-isomer: t = 59.83 min). 1H NMR
(400 MHz, CDCl3): d 7.59–7.57 (m, 2H), 7.46–7.19 (m, 8H), 5.64
(s, 1H), 2.81 (br, 1H). 13C NMR (100 MHz, CDCl3): d 140.6, 131.7,
128.6, 128.5, 128.3, 128.2, 126.7, 122.4, 88.8, 86.5, 64.9.
8. Banphavichit, V.; Bhanthumnavin, W.; Vilaivan, T. Tetrahedron 2007, 63, 8727–
8734.
9. Bernardinelli, G.; Fernandez, D.; Gosmini, R.; Meier, P.; Ripa, A.; Schupfer, P.;
Treptow, B.; Kundig, E. P. Chirality 2000, 12, 529–539.
10. (a) Lutz, F.; Igarashi, T.; Kinoshita, T.; Asahina, M.; Tsukiyama, K.; Kawasaki, T.;
Soai, K. J. Am. Chem. Soc. 2008, 130, 2956–2958; (b) Kitamura, M.; Okada, S.;
Suga, S.; Noyori, R. J. Am. Chem. Soc. 1989, 111, 4028–4036; (c) Kitamura, M.;
Suga, S.; Oka, H.; Noyori, R. J. Am. Chem. Soc. 1998, 120, 9800–9809; (d)
Yamakawa, M.; Noyori, R. J. Am. Chem. Soc. 1995, 117, 6327–6335.
11. Cardellicchio, C.; Ciccarella, G.; Naso, F.; Perna, F.; Tortorella, P. Tetrahedron
1999, 55, 14685–14692.
References
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