Enantioselective addition of diethylzinc to aldehydes by chiral oxazolidine-titanium complex

Article abstract of DOI:10.2174/157017812803521180

A series of chiral oxazolidines derived from (1R, 2S)-cis-1-amino-2-indanol was found to be effective in promoting the asymmetric addition of diethylzinc to aldehydes. Among the ligands developed, it was found that ligand 1b in the presence of Ti(OⁱPr)₄ yielded the highest enantioselectivities when it was applied in the catalytic asymmetric addition of diethylzinc to aldehydes (up to 91% ee).

Full text of DOI:10.2174/157017812803521180

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644
Letters in Organic Chemistry, 2012, 9, 644-649
Enantioselective Addition of Diethylzinc to Aldehydes by Chiral
Oxazolidine–Titanium Complex
Nan Wuc, Rongcheng Bob, Rongli Zhanga, Xi Jianga, Yu Wanb, Zhou Xu*,a and Hui Wu*,b
aDepartment of Chemistry, Xuzhou Medical College, Xuzhou 221004, P. R. China
bCollege of Chemistry and Chemical Engineering, Xuzhou Normal University, Xuzhou 221116, P. R. China
cDepartment of Aviation Oil and Material, Xuzhou Airforce College, Xuzhou 221110, P. R. China
Received May 09, 2012: Revised August 01, 2012: Accepted August 08, 2012
Abstract: A series of chiral oxazolidines derived from (1R, 2S)-cis-1-amino-2-indanol was found to be effective in
promoting the asymmetric addition of diethylzinc to aldehydes. Among the ligands developed, it was found that ligand 1b
in the presence of Ti(OiPr)4 yielded the highest enantioselectivities when it was applied in the catalytic asymmetric addi-
tion of diethylzinc to aldehydes (up to 91% ee).
Keywords: Asymmetric alkynylation, enantioselectivity oxazolidine, secondary alcohol.
INTRODUCTION
with quantitative yields. With ligands 1a-1g (Fig. 1) in hand,
we examined the use of each in the ethylation of benzalde-
hyde. As the results shown in Figure 2, we found that ligand
1b gave the best result with 70% yield and 55% ee, respec-
tively. Although ligand 1g gave the highest ee, which may be
due to the presence of the chelating group of CN of the
ligand, it is not suitable to choose it as the ligand to catalyze
the reaction because the product is hard to separate from the
ligand. In this case, we chose ligand 1b for our further stud-
ies.
Chiral sec-alcohols are important and versatile building
blocks for many natural products and drugs [1-3]. One of the
most useful methods for the asymmetric preparation of sec-
alcohols is the enantioselective addition of dialkylzinc rea-
gent to aldehydes in the presence of chiral ligands [4]. A
wide variety of chiral catalysts, such as amino alcohols [5-
10], diamines [11-14], disulfonamides [15-19] and diols [20-
27] have been reported. Although so many chiral ligands
have been used to catalyze the reaction with good to excel-
lent selectivity, it is still desirable to develop new chiral
ligands which are greatly needed to probe how the chiral
catalysts act on the reaction and how to design new types of
chiral ligands more successfully. (1R, 2S)-cis-1-amino-2-
indanol has a special structure which has attracted much
attention. However, among the ligands developed, only a
few chiral ligands derived from (1R, 2S)-cis-1-amino-2-
indanol were found to be effective in promoting the
asymmetric addition of diethylzinc to aldehydes [28]. In the
long run, we aim to synthesize the ligands which are easily
prepared in short pathway from readily available starting
materials and to apply them in asymmetric transition proc-
esses [29-31]. With the interest in oxazolidine catalysts, we
have designed and synthesized chiral ligands derived from
(1R, 2S)-cis-1-amino-2-indanol and applied them in the
asymmetric alkynylzinc addition reactions [29]. Herein, we
reported the enantioselective addition of dialkylzinc reagents
to aldehydes in the presence of those ligands.
Then the effects of the reaction conditions, such as the
choice of solvents, the amount of ligand 1b, the reaction
temperature and the amount of Ti(OiPr)4 were investigated.
The results are shown in Table 1. At room temperature, the
best ee was obtained in hexane with 10 mmol % ligand (Ta-
ble 1, entry 5). Decreasing the amount of the ligand 1b to 5
mmol % gave only 52 % ee of the product (Table 1, entry 6)
and increasing the amount of ligand to 30 mol % improved
the selectivity only slightly (Table 1, entry 8). Lowering re-
action temperatures did not improve the enantioselectivities
(Table 1, entries 9-10). Addition of appropriate Ti(OiPr)4 to
the reaction provided a better effective catalytic system.
When the reaction was carried out in hexane at room tem-
perature with a reagent ratio of Et2Zn– benzaldehyde–
ligand–Ti(OiPr)4 = 4 : 1 : 0.1 : 0.25, the highest ee of the
product was obtained (Table 1, entry 12).
Under the optimized conditions (Table 1, entry 12), the
scope of the reactions catalyzed by 1b was investigated
(Scheme 1). As shown by the results summarized in Table 2,
moderate to good enantioselectivities were obtained for most
of the active aromatic aldehydes. Substituents of the alde-
hydes have important effects on the enantioselectivity. Those
containing electron-withdrawing groups at the para positions
gave better ees than those containing electron-donating ones
(Table 2, entries 1-9). Substituents at the ortho- position of
aldehydes gave poorer ee than benzaldehyde (Table 2, en-
tries 6-8 and 10). The cyano derivative gave the highest ee
(91%) in this series which may be due to the presence of the
RESULTS AND DISCUSSION
Ligands 1a-1g were synthesized via the reaction of (1R,
2S)-cis-1-amino-2-indanol and the aldehydes in one step
*Address correspondence to this author at the College of Chemistry and
Chemical Engineering, Xuzhou Normal University, Xuzhou 221116, P. R.
China; Tel: +86-516-852980403; Fax: +86 (0) 51683500431;
E-mail: xuzhou@xzmc.edu.cn
1875-6255/12 $58.00+.00
© 2012 Bentham Science Publishers

Enantioselective Addition of Diethylzinc to Aldehydes by Chiral
Letters in Organic Chemistry, 2012, Vol. 9, No. 9
645
Cl
F
F
HN
HN
HN
HN
O
O
O
O
1d
1a
1b
1c
CN
Me
NO2
HN
O
HN
HN
O
O
1g
1f
1e
Fig. (1). Ligands evaluated in this paper.
100
90
80
70
60
50
40
30
20
10
0
Yield
ee
1a 1b
1c
1d 1e
1f
1g
Fig. (2). Screening of ligands.
Table 1. Screening of the Reaction Conditionsa.
Entry
Ligand (mol%)
Ti(OiPr)4/Ligand
Solvent
Yield (%)b
ee (%)c
1
2
3
4
5
6
7
8
10
10
10
10
10
5
-
-
-
-
-
-
-
-
Et2O
DCM
52
16
64
18
60
38
51
52
24
29
31
0
THF
DMF
Hexane
Hexane
Hexane
Hexane
58
52
55
61
20
30

646 Letters in Organic Chemistry, 2012, Vol. 9, No. 9
Wu et al.
Table 1. contd….
Entry
9d
Ligand (mol%)
Ti(OiPr)4/Ligand
Solvent
Yield (%)b
ee (%)c
30
30
10
10
10
10
10
10
10
10
-
-
Hexane
Hexane
Hexane
Hexane
Hexane
Hexane
Hexane
Hexane
Hexane
Hexane
27
18
57
63
58
60
62
54
74
59
37
41
59
62
59
31
11
6
11
12
13
14
15
16
17
18
0.125
0.25
1.0
2.0
3.0
4.0
5.0
6.0
6
4
a The reaction conditions: benzaldehyde (0.5 mmol), Et2Zn (2.0 ml), 1b (0.05 mmol), Solvent (1.0 ml), room temperature, 24 h.
b Isolated yield.
c The ee was determined by Chiral HPLC: Daicel CHIRALPAD OD-H column (IPA : hexane = 3 : 97), flow: 0.5 mL/min, 30 oC, Retention time: tmajor = 24.90 min, tminor = 21.35 min
and the absolute configuration of the product is R [32].
d The reaction was carried out at 0 oC.
e The reaction was carried out at -25 oC.
chelating group of CN (Table 2, entry 5). Moderate ee (60%)
can also be obtained with aliphatic aldehyde (Table 2, entry
12).
good catalytic activities (63-95%) and enantioselectivities
(up to 91%) in the asymmetric addition reactions of dieth-
ylzinc to various aldehydes in the presence of Ti(OiPr)4. The
results of this paper would help to reveal the relationship
between ligand structure and ee values of the products. Fur-
ther investigation on the applications of these ligands for
other asymmetric reactions is underway.
Ti(OiPr)4/1b (10 mol%)
OH
R
CHO
R
Et2Zn, DCM, r.t
Scheme 1. Scopes of the reaction.
EXPERIMENTAL
In summary, ligand 1b which is readily prepared in one
step from commercially available starting materials, showed
All manipulations were carried out under an argon at-
mosphere in dried and degassed solvents. Diethylzinc was
Table 2. Scopes of the Reactiona.
Entry
R
Yield (%)b
Ee (%)c
1
2
4-Cl-C6H4
4-Br-C6H4
78
75
71
72
87
75
77
72
65
63
95
64
63
67
73
17
91
31
27
28
60
62
67
60
3
4-I-C6H4
4
4-OMe-C6H4
4-CN-C6H4
2-Me-3-Me-C6H3
2-OMe-3-OMe-C6H3
2-OMe-C6H4
3-F-C6H4
5
6
7
8
9
10
11
12
C6H5
2-naphthyl
Ph-CH2-CH2
a The reaction conditions: aldehydes (0.5 mmol), Et2Zn (2.0 ml), 1b (0.05 mmol), Solvent (1.0 ml), Ti(OiPr)4 (0.0125 mmol), room temperature, 24 h.
b Isolated yield after column chromatography.
c
Determinated by Chiral HPLC: Daicel CHIRALPAD AD-H or OD-H; the absolute configuration of the product is R by comparing with the literatures or based on comparison of
the elution order of HPLC analysis with those reported analogs [32, 33].

Enantioselective Addition of Diethylzinc to Aldehydes by Chiral
Letters in Organic Chemistry, 2012, Vol. 9, No. 9
647
purchased from Aldrich (St. Louis, MO). The reactions were
monitored by thin layer chromatography (TLC). NMR spec-
tra were measured in CDCl3 on a Varian-Inova-400 NMR
spectrometer with TMS as an internal reference. Optical ro-
tations were measured with a HORIBA SEPA-200 high sen-
sitivity polarimeter. Chiral HPLC analyses were carried out
on an Agilent 1100 instrument. Enantiomeric excess (ee)
determination was carried out using a chiral AD-H column
(4.6ꢀ250 mm) or OD-H column (4.6ꢀ250 mm) (Solvent,
7.29 (m, 3H), 7.24–7.12 (m, 3H), 7.03–6.95 (m, 1H), 5.11(s,
1H), 5.08 (d, J = 5.6 Hz, 1H), 4.93–4.90 (m, 1H), 3.32–3.20
(m, 2H), 2.53 (s, 1H); IR (cm–1) : 3293, 1689, 1592, 1456,
1384, 1167, 1049; MS [ESI] [M+H] found (expected):
256.2619 (256.1138).
o
25
Ligand 1e: White crystal. mp. 78–80 C; [ꢁ]D = + 69.5
1
1
(c 1.83, acetone); dr. 3.0:1 (determined by H NMR); H
NMR (400 MHz, CDCl3) ꢀ 7.49 (t, J = 8.4 Hz, 1H), 7.40 (d,
J = 8.0 Hz, 2H), 7.30–7.27 (m, 2H), 7.24–7.20 (m, 1H), 7.15
(d, J = 8.0 Hz, 2H), 5.09–5.08 (m, 2H), 4.93–4.90 (m, 1H),
3.27–3.24 (m, 2H), 2.40 (s, 1H), 2.33 (s, 3H); IR (cm–1) :
3290, 2946, 2897, 1458, 1447, 1102, 1021; MS [ESI] [M+]
found (expected): 252.1349 (252.1388).
o
hexane/isopropanol) at 25 C. UV detection, 254 nm. MS
were recorded on a Bruker Micro-TOF-QII spectrometer
using the ESI method. Melting points were determined using
a standard melting point apparatus (XT-5 Type) and uncor-
rected.
o
25
Ligand 1f: Yellow crystal. mp. 120–122 C; [ꢁ]D = +
91.3 (c 0.79, acetone); dr. 2.75 : 1 (determined by 1H NMR);
1H NMR (400 MHz, CDCl3) ꢀ 8.21 (d, J = 8.4 Hz, 2H), 7.66
(d, J = 8.4 Hz, 2H), 7.50 (t, J = 8.4 Hz,1H), 7.33–7.29 (m,
2H), 7.21–7.14 (m, 1H), 5.20 (s,1H), 5.10 (d, J = 5.6 Hz,
1H), 4.98–4.96(m, 1H), 3.34–3.21 (m, 2H), 2.51 (s, 1H); MS
[ESI] [M+H] found (expected): 283.1117 (283.1083).
General Experimental Procedure
A solution of ligand 1b (0.05 mmol) was dissolved in dry
hexane (2 ml) under Ar in a schlenk tube. Then diethylzinc
(2 mL, 1 M in hexane, 2.0 mmol) and Ti(OiPr)4 (0.0125
mmol) was added separately via a syringe. The reaction was
stirred at room temperature for 2 h. Then the aldehyde (0.5
mmol) was added and the reaction mixture was stirred for 24
h. The reaction was quenched with 1 M HCl (5 mL). The
mixture was extracted with ethyl acetate (EtOAc) (3 ꢀ 15
ml). The organic layer was dried over Na2SO4 and concen-
trated under vacuum. The residue was purified by flash col-
umn chromatography (silica gel H, EtOAc: Petroleum ether
= 1: 6) to give the pure product.
o
25
Ligand 1g: White solid. 119–121 C; [ꢁ]D = + 91.3 (c
1
0.71, acetone); dr. 2.78:1 (determined by H NMR); 1H
NMR (400 MHz, CDCl3) ꢀ 7.65 (d, J = 8.4 Hz, 2H), 7.60 (d,
J = 8.4 Hz, 2H), 7.51–7.48 (m, 2H), 7.31–7.29 (m, 2H), 5.16
(s, 1H), 5.08 (d, J = 5.6 Hz, 1H), 4.97–4.90 (m, 1H), 3.29–
3.20 (m, 2H), 2.49 (s, 1H); IR (cm–1) : 3273, 2229, 1554,
1044; MS [ESI] [M+] found (expected): 263.1275
(263.1184).
SPECTRAL DATA
1-(4-chlorophenyl)propan-1-ol [35-38]
Synthesis and the X-Ray crystal structure of ligand 1a
have been reported by us [29]. The other ligands are new
compounds. All of the chiral propanol derivatives are known
compounds.
Colorless oil, 78% yield. 63% ee determined by HPLC
analysis (Chiralcel OD-H column, IPA: hexane = 1 : 99).
Flow: 1.0 mL/min, 25oC, Retention time: tmajor = 12.27 min,
tminor = 14.13 min. H1 NMR (CDCl3, TMS): ꢀ 7.29 (q, J = 8.4
Hz, 4H), 4.58 (t, J = 6.4 Hz, 1H), 1.90 (s, 1H), 1.83–1.68 (m,
2H), 0.90 (t, J = 7.2 Hz, 3H).
o
25
Ligand 1a: White crystal. mp. 69–70 C; [ꢁ]D = + 82.8
(c 1.02, abs. EtOH); dr. 2.89:1 (determined by 1H NMR); 1H
NMR (400 MHz, CDCl3) ꢀ 8.58–7.07 (m, 9H), 5.12–5.07
(m, 2H), 4.81 (d, J = 4.4 Hz, 1H), 3.24–3.17 (m, 2H), 2.53
(s, 1H); IR (cm–1) : 3280, 1026, 895, 756; MS [ESI] [M+]
found (expected): 237.1165 (237.1154).
1-(4-bromophenyl)propan-1-ol [35, 37]
Colorless oil, 75% yield. 67% ee determined by HPLC
analysis (Chiralcel OD-H column, IPA: hexane = 3 : 97).
Flow: 0.5 mL/min, 25oC, Retention time: tmajor = 21.96 min,
tminor = 24.13 min. H1 NMR (CDCl3, TMS): ꢀ 7.37 (d, J = 8.4
Hz, 2H), 7.11 (d, J = 8.0 Hz, 2H), 4.46 (t, J = 6.4 Hz, 1H),
2.00 (s, 1H), 1.73–1.58 (m, 2H), 0.81 (t, J = 7.6 Hz, 3H).
Ligand 1b: White crystal. mp. 95–97 oC; [ꢁ]D25 = + 127.5
1
1
(c 0.51, acetone); dr. 2.44:1 (determined by H NMR); H
NMR (400 MHz, CDCl3) ꢀ 7.50–7.49 (m, 1H), 7.48–7.42
(m, 2H), 7.31–7.27 (m, 2H), 7.25–7.24 (m, 1H), 7.03 (t, J =
8.4 Hz, 2H), 5.10–5.08 (m, 2H), 4.95–4.92 (m, 1H), 3.32–
3.16 (m, 2H), 2.50 (1s, 1H); IR (cm–1) : 3300, 1604, 1509,
1439, 1221; MS [ESI] [M+] found (expected): 278.0972
(278.0957).
1-(4-iodophenyl)propan-1-ol [32, 38]
Colorless oil, 71% yield. 73% ee determined by HPLC
analysis (Chiralcel OD-H column, IPA: hexane = 3 : 97).
Flow: 0.5 mL/min, 25oC, Retention time: tmajor = 26.97 min.
H1 NMR (CDCl3, TMS): ꢀ 7.67 (d, J = 8.0 Hz, 2H), 7.09 (d,
J = 8.0Hz, 2H), 4.57 (t, J = 6.4Hz, 1H), 1.80–1.68 (m, 3H),
0.91 (t, J = 7.2 Hz, 3H).
o
25
Ligand 1c: White crystal. mp. 118–120 C; [ꢁ]D = +
1
89.4 (c 2.11, acetone); dr. 3.03:1 (determined by H NMR);
1H NMR (400 MHz, CDCl3) ꢀ 7.49 (t, J = 8.4 Hz, 1H), 7.41–
7.38 (m, 2H), 7.35–7.28 (m, 4H), 7.23–7.21 (m, 1H), 5.08–
5.07 (m, 2H), 4.93–4.90 (m, 1H), 3.29–3.20 (m, 2H), 2.51 (s,
1H); IR (cm–1) : 3290, 1598, 1436, 1088, 1014; MS [ESI]
[M+Na] found (expected): 294.0707 (294.0662).
1-(4-methoxyphenyl)propan-1-ol [35, 36]
Ligand 1d: White solid. mp. 38–40 oC; [ꢁ]D25 = + 84.3 (c
Colorless oil, 72% yield. 17% ee determined by HPLC
analysis (Chiralcel OD-H column, IPA: hexane = 5 : 95).
Flow: 0.5 mL/min, 25oC, Retention time: tmajor = 21.87 min,
1
0.58, acetone); dr. 2.93:1 (determined by H NMR); 1H
NMR (400 MHz, CDCl3) ꢀ 7.49 (t, J = 7.8 Hz, 1H), 7.39–

648 Letters in Organic Chemistry, 2012, Vol. 9, No. 9
Wu et al.
tminor = 20.64 min. H1 NMR (CDCl3, TMS): ꢀ 7.18 (d, J = 8.4
Hz, 2H), 6.80 (d, J = 8.4 Hz, 2H), 4.47 (t, J = 6.4 Hz,1H),
3.73 (s, 3H), 1.80–1.52 (m, 3H), 0.82 (t, J = 7.2 Hz, 3H).
1-(naphthalen-2-yl)propan-1-ol [35, 36]
White solid, mp 33-35oC, 56% yield. 63% ee determined
by HPLC analysis (Chiralcel OD-H column, IPA: hexane =
10 : 90). Flow: 0.5 mL/min, 25oC, Retention time: tmajor
=
4-(1-hydroxypropyl)benzonitrile [37]
18.49 min, tminor = 21.55 min. H1 NMR (CDCl3, TMS): ꢀ
7.84–7.82 (m,3H ),7.67 (s,1H), 7.48–7.45 (m,3H), 4.76 (t, J
= 6.4 Hz,1H), 1.99 (s,1H), 1.94–1.81 (m,2H), 0.94 (t, J = 7.6
Hz, 3H).
Colorless oil, 87% yield. 91% ee determined by HPLC
analysis (Chiralcel OD-H column, IPA: hexane = 15 : 85).
Flow: 0.5 mL/min, 25oC, Retention time: tmajor = 12.11 min,
tminor = 15.62 min. H1 NMR (CDCl3, TMS): ꢀ 7.63 (d, J = 8.0
Hz, 2H), 7.45 (d, J = 8.0 Hz, 2H), 4.69 (t, J = 6.4 Hz,1H),
2.13 (s, 1H), 1.83–1.71 (m, 2H), 0.93 (t, J = 7.6 Hz,1H).
1-phenylpentan-3-ol [32, 39]
Colorless oil, 64% yield. 60% ee determined by HPLC
analysis (Chiralcel AD-H column, IPA: hexane = 3 : 97).
Flow: 1.0 mL/min, 25oC, Retention time: tmajor = 11.69 min,
tminor = 10.93 min. H1 NMR (CDCl3, TMS): ꢀ 7.30–7.25 (m,
2H), 7.21–7.16 (m, 3H), 3.55 (ddd, J = 12.2 Hz, 8.0 Hz, 4.5
Hz, 1H), 2.80 (ddd, J = 14.1 Hz, 9.8 Hz, 5.8 Hz, 1H), 2.67
(ddd, J = 13.8 Hz, 9.7 Hz, 6.7 Hz, 1H), 1.84–1.76 (m, 2H),
1.56–1.41 (m, 3H), 0.94 (t, J = 7.2 Hz, 3H).
1-(2,3-dimethylphenyl)propan-1-ol [32]
Colorless oil, 75% yield. 31% ee determined by HPLC
analysis (Chiralcel OD-H column, IPA: hexane = 1 : 99).
Flow: 1.0 mL/min, 25oC, Retention time: tmajor = 13.63 min,
tminor = 20.19 min. H1 NMR (CDCl3, TMS): ꢀ 7.32 (d, J = 7.6
Hz, 1H), 7.12 (t, J = 7.6 Hz, 1H), 7.07(d, J = 7.6 Hz, 1H),
4.91 (t, J = 6.4 Hz), 2.29 (s, 3H), 2.22 (s, 3H), 1.78–1.71(m,
3H), 1.26(s, 3H), 0.98 (t, J = 7.2 Hz).
CONFLICT OF INTEREST
The author(s) confirm that this article content has no con-
flicts of interest.
1-(2,3-dimethoxyphenyl)propan-1-ol [32]
Colorless oil, 77% yield. 27% ee determined by HPLC
analysis (Chiralcel OD-H column, IPA: hexane = 5 : 95).
Flow: 0.5 mL/min, 25oC, Retention time: tmajor = 26.09 min,
tminor = 32.57 min. H1 NMR (CDCl3, TMS): ꢀ 7.04 (t, J = 8.0
Hz, 1H), 6.93 (d, J = 7.6 Hz, 1H), 6.84 (d, J = 7.6 Hz, 1H),
4.84 (t, J = 6.8 Hz,1H), 3.86 (s, 3H), 3.85 (s, 3H), 2.41 (s,
1H), 1.85–1.72 (m, 2H), 0.95 (t, J = 7.6 Hz, 3H).
ACKNOWLEDGEMENTS
We are grateful to the grants from the Natural Science
Foundation of Higher Education Institutions of Jiangsu Prov-
ince, China (No. 10KJB150018) and (No. 10KJA430050)
and Qin Lan Project in Jiangsu Province (NO. 08QLT001).
1-(2-methoxyphenyl)propan-1-ol [32]
REFERENCES
Colorless oil, 72% yield. 28% ee determined by HPLC
analysis (Chiralcel OD-H column, IPA: hexane = 5 : 95).
Flow: 0.5 ml/min, 25oC, Retention time: tmajor = 18.66 min,
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1
tminor = 20.63 min. H NMR ( 400 MHz, CDCl3) ꢀ 7.21 (d, J
= 7.6 Hz, 1H), 7.15 (t, J = 7.4 Hz, 1H), 6.87 (t, J = 7.4 Hz,
1H), 6.79 (d, J = 8.0 Hz, 1H), 4.71 (t, J = 6.6 Hz, 1H), 3.76
(s, 3H), 2.54 (s, 1H), 1.75–1.71 (m, 2H), 0.87 (t, J = 7.4 Hz,
3H).
[3]
[4]
1-(3-fluorophenyl)propan-1-ol [32, 39]
Colorless oil, 65% yield. 60% ee determined by HPLC
analysis (Chiralcel AD-H column, IPA: hexane = 3 : 97).
Flow: 1.0 mL/min, 25oC, Retention time: tmajor = 11.69 min,
tminor = 10.93 min. H1 NMR (CDCl3, TMS): ꢀ 7.32–7.27 (m,
1H), 7.10–7.05 (m, 2H), 6.95 (dt, J = 2.4 Hz, 8.5 Hz, 1H),
4.60 (t, J = 6.4 Hz,1H), 1.91 (s, 1H), 1.81–1.72 (m, 2H), 0.92
(t, J = 7.2 Hz, 3H).
[5]
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1-phenylpropan-1-ol [35-37]
Colorless oil, 63% yield. 62% ee determined by HPLC
analysis (Chiralcel OD-H column, IPA: hexane = 3 : 97).
Flow: 0.5 mL/min, 25oC, Retention time: tmajor = 24.90 min,
tminor = 21.35 min. H1 NMR (CDCl3, TMS): ꢀ 7.35–7.27 (m,
5H), 4.59 (t, J = 6.8 Hz,1H), 1.87 (s, 1H), 1.86–1.71 (m,
2H), 0.91 (t, J = 7.2 Hz, 3H).

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