Modular amino acid amide chiral ligands for enantioselective addition of diethylzinc to aromatic aldehydes

Article abstract of DOI:10.1002/aoc.1785

Enantioselective addition of diethylzinc to a series of aromatic aldehydes was developed using a modular amino acid amide chiral ligand (2S)-3-phenyl-N-((R)-1-phenyl-ethyl)-2-(tosylamino)propanamide without using titanium complex. The catalytic system employing 10 mol% of 1g was found to promote the addition of diethylzinc (ZnEt₂) to a wide range of aromatic aldehydes with electron-donating and electron-withdrawing substituents, giving up to 82% ee of the corresponding secondary alcohol under mild conditions.

Full text of DOI:10.1002/aoc.1785

Full Paper
Received: 17 November 2010
Revised: 13 January 2011
Accepted: 1 February 2011
Published online in Wiley Online Library: 28 April 2011
(wileyonlinelibrary.com) DOI 10.1002/aoc.1785
Modular amino acid amide chiral ligands
for enantioselective addition of diethylzinc
to aromatic aldehydes
a,b∗
a,b
b
b
Shaohua Gou , Zhongbin Ye , Jing Chang , Guangjun Gou
b
and Mingming Feng
Enantioselective addition of diethylzinc to a series of aromatic aldehydes was developed using a modular amino acid amide
chiral ligand (2S)-3-phenyl-N-((R)-1-phenyl-ethyl)-2-(tosylamino)propanamide without using titanium complex. The catalytic
systememploying10 mol%of1gwasfoundtopromotetheadditionofdiethylzinc(ZnEt2)toawiderangeofaromaticaldehydes
with electron-donating and electron-withdrawing substituents, giving up to 82% ee of the corresponding secondary alcohol
under mild conditions. Copyright ꢀc 2011 John Wiley & Sons, Ltd.
Keywords: addition reaction; aldehyde; amide; diethylzinc; sulfonylamino
Introduction
32% ee with 91% yield employing the 1i–Ti(IV) complex in the
addition reaction of diethylzinc to benzaldehyde (Table 1, entry
Enantioselective addition of diorganozinc reagents to aldehydes
is a fundamental and successful area in the field of asymmetric
C–C bond formation reactions, natural products and biologically
9). We assumed that the titanium (IV) plays a disfavored role in
the addition reaction of diethylzinc (ZnEt2) to benzaldehyde.
Therefore, a series of chiral ligands, 1a – i, without Ti(i-OPr)4
was investigated under the same conditions according to the
bifunctional concept by adjusting the Lewis acid (center metal
titanium and zinc) of the catalyst systems (Table 1, entries 10–18).
It was found that a significant improvement was achieved when
[
1]
active compounds. Considerable progress has been made in
employing diethylzinc or dimethylzinc reagents as the chiral
source by many research groups using diverse chiral ligands,
[
2]
[3]
[4]
[5]
such as diols, diamines, aminothiols, aminodisulfides,
amino alcohols,[6] diphosphoryldiols,[7] phosphoramides and
aminodiselenides.[ Despite the achievements made in this field
of the addition of aldehydes, it is still necessary to develop new
types of catalytic system and to probe how the chiral catalysts
work for the addition of diethylzinc to aldehyde.
[8]
1
5 mol% 1g was employed in the enantioselective addition
of diethylzinc to benzaldehyde with 68% ee and 78% yield
Table 1, entry 16). Other catalyst systems, including bigger
9]
(
substituents (ligands 1b,c and 1e), a longer carbon chain (1d) and
stronger electron-withdrawing groups (1f), could also improve
the ee’s, although the yields were decreased dramatically (Table 1,
entries 10–15, 17 and 18). In addition, the ligand 1h, which
has different configuration to 1g, only gave 29% ee with 44%
yield under same conditions (Table 1, entry 17). The 1i, which
gave the highest ee with titanium (IV) complex, only gave
Recently, we reported the synthesis of chiral sulfonamide-
protected β-amino alcohol ligands and their application in the
enantioselective addition of diethylzinc to aromatic aldehydes
with good to excellent yields and enantioselectivities. Inspired
by the results, we continued to search for a new highly efficient
catalyst system for the enantioselective addition of diethylzinc
to aromatic aldehydes. The series of chiral ligands 1a–i (see
Fig. 1; 1a–d and g–i have been previously described, and 1e–f
are new compounds, see Experimental section for details) were
synthesized using L-phenylalanine and a chiral or achiral amine as
raw material.
[
6a]
4
6% ee with 83% yield without titanium (IV) complex (Table 3,
entry 18).
Next, we investigated the effect of different solvents (toluene,
CH2Cl2, THF, Et2O, hexaneandxylene)usingthe1gcatalystsystem
Table 2, entries 1–5). It was found that very low yield and only 3%
ee were obtained in Tetrahydrofuran (THF) (Table 2, entry 2), while
[
10]
(
9
3
9% yield and 35% ee could be afforded in Et2O (Table 2, entry
), which might be attributed to the different polarity. Moderate
Results and Discussion
Catalyst System Screening
∗
Correspondenceto:Shaohua Gou,StateKeyLaboratoryofOilandGasReservoir
Geology and Exploitation, Southwest Petroleum University, Chengdu 610500,
People’s Republic of China. E-mail: shaohuagou@swpu.edu.cn
In the preliminary studies, we investigated the addition reaction
of diethylzinc (ZnEt2) to benzaldehyde (2a) in the presence of
1
5 mol% chiral ligand (1a–i) combined with 15 mol% Ti(i-OPr)4
◦
a State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,
Southwest Petroleum University, Chengdu 610500, People’s Republic of China
(1 : 1 ratio) in dry toluene at 0 C under a nitrogen atmosphere
Table 1, entries 1–18). These titanium complexes (IV) had high
(
reactivity and gave good to excellent isolated yields (Table 1,
entries 1–9). However, the highest enantiomeric excess was only
b School of Chemistry and Chemical Engineering, Southwest Petroleum
University, Chengdu 610500, People’s Republic of China
Appl. Organometal. Chem. 2011, 25, 448–453
Copyright ꢀc 2011 John Wiley & Sons, Ltd.

Enantioselective addition of diethylzinc to aromatic aldehydes
O
O
Ph
O
Ph
Ph
N
Ph
Ph
N
NHTs
H
H
NHTs
1b
TsHN HN Ph
1
a
1c
F3C
O
O
Ph
Ph
O
CF3
Ph
Ph
N
Ph
Ph
N
H
H
NHTs
NHTs
1e
TsHN HN
1
d
1f
Ph
O
O
O
TsHN HN
N
Ph
N
Ph
H
H
NHTs
NHTs
1h
Figure 1. The structures of the chiral ligands for the addition of diethylzinc to aldehydes.
HO
1i
1
g
Table 1. Screening of the ligands 1a–i for the enantioselective
Table 2. Screening of the solvent enantioselective addition of
addition of diethylzinc to benzaldehyde
diethylzinc to benzaldehyde
Temperature
O
OH
*
◦
Entrya
Solvent
( C)
Time (h) Yield (%)b
Ee (%)c
1
5 mol% 1
H
+
ZnEt2
1
2
3
4
5
6
PhCH3
THF
0
0
0
0
0
0
24
24
24
24
24
24
78
trace
99
68(S)
3(S)
PhCH , 0°C
3
Et2O
35(S)
15(S)
18(S)
66(S)
2
a
3a
CH2Cl2
Hex
58
Entrya
Ligand
Ti(i-OPr)4 (mol%)
Yield (%)b
Ee (%)c
79
Xylene
73
1
2
3
4
5
6
7
8
9
1a
1b
1c
1d
1e
1f
15
15
15
15
15
15
15
15
15
0
93
86
89
88
87
90
95
86
91
69
57
41
68
20
71
78
44
83
13(S)
0
a
Conditions: concentration of 2a, 0.25 M in PhCH3; ZnEt2, 1.5 equiv. in
hexane solution; 1g, 15 mol%.
5(S)
0
b
Isolated yields.
c
The ee was determined by chiral GC G-TA column, and the
8(S)
7(S)
0
(
S)-configuration was confirmed by comparison with the reported
[
2a,7b,11,12]
configuration.
1g
1h
1i
5(S)
32(S)
19(S)
37(S)
48(S)
9(S)
47(S)
29(S)
68(S)
29(S)
46(S)
The loading of 1g and ZnEt2, optimum temperature and the
concentration of 2a were also investigated using chiral ligand
g (Table 3, entries 1–10). Better enantioselectivity was not
obtained when lowering or increasing the concentration of 2a
Table 3, entries 2 and 3). Changing the loadings of ZnEt2 and
reaction temperature (20 or −20 C) also did not improve the
enantioselectivity (Table 3, entries 4–7). Better enantioselectivity
was obtained when the loading of 1g decreased from 20 to
10
11
12
13
14
15
16
17
18
1a
1b
1c
1d
1e
1f
0
1
0
0
(
0
◦
0
1g
1h
1i
0
0
1
0 mol%, although a longer reaction time was required (Table 3,
0
entry 9). Greater loading of 1g (increased from 15 to 25 mol%)
caused significant improvement in the reactivity (Table 3, entry
8). Smaller loading of 1g (5 mol%) gave very bad reactivity and
low enantioselectivity after 80 h (Table 3, entry 10). The optimal
catalyst system and reaction conditions were 10 mol% 1g, 1.5
a
Conditions: concentration of 2a, 0.25 M in PhCH3; ZnEt2, 1.5 equiv. in
hexane solution; reaction time, 24 h.
Isolated yields.
b
c
The ee was determined by chiral GC G-TA column, and the
S- or R-configuration was confirmed by comparison with the reported
◦
configuration.[
2a,7b,11,12]
equiv. ZnEt2 and 0.25 M of 2a in PhCH3 at 0 C.
Substrate Generality
To study the generality of the 1g catalyst system for the enan-
tioselective addition of diethylzinc to various aromatic aldehydes,
a number of aromatic aldehydes having electron-donating or
electron-withdrawing groups, a- and β-naphthaldehydes and (E)-
cinnamaldehyde were examined under the optimized conditions
yields and low ee’s could be produced employing CH2Cl2 and
hexane (Table 2, entries 4 and 5). Similar results were observed
with toluene and xylene (Table 3, entry 6 vs 1). The highest ee of
68% was obtained in toluene (Table 2, entry 1).
Appl. Organometal. Chem. 2011, 25, 448–453
Copyright ꢀc 2011 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/aoc

S. Gou et al.
Table 3. Optimization of the catalytic system for the enantioselective addition of diethylzinc to benzaldehyde catalyzed by 1g
Entrya
1g (mol%)
Concentration of 2a
ZnEt2 (equiv.)
Temperature ( C)
◦
Time (h)
Yield (%)b
Ee (%)c
1
2
3
4
5
6
7
8
9
15
15
15
15
15
15
15
25
10
5
0.25
0.5
1.5
1.5
1.5
1.8
1.0
1.5
1.5
1.5
1.5
1.5
0
0
24
10
48
24
48
48
10
20
40
80
78
83
49
68
43
38
88
94
71
40
68
63
57
67
54
71
54
65
75
66
0.1
0
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0
0
−20
20
0
0
10
0
a
b
c
Conditions: solvent, PhCH3; ZnEt2, hexane solution.
Isolated yields.
The ee was determined by chiral GC G-TA column and the (S)-configuration was confirmed by comparison with the reported configuration.[2a,7b,11,12]
Table 4. Enantioselective addition of diethylzinc to various aromatic aldehydes catalyzed by 1g
O
OH
*
H
10 mol% 1g
+
ZnEt2
R
R
PhCH , 0°C
3
2a-n
3a-n
Entrya
Aldehyde
Time (h)
Yield (%)b
Ee (%)c
1
2
3
4
5
6
7
8
9
Benzaldehyde (2a)
40
60
60
60
60
40
40
40
40
40
40
60
40
40
71
51
48
38
41
76
74
60
69
76
60
37
83
85
75(S)
59(S)
50(S)
60(S)
57(S)d
71(S)
73(S)
65(S)
74(S)
76(S)
51(S)e
42(S)d
82(S)d
70(S)d
4-Methyl-benzaldehyde (2b)
2-Methyl-benzaldehyde (2c)
4-Methoxy-benzaldehyde (2d)
3-Methoxy-benzaldehyde (2e)
4-Fluoro-benzaldehyde (2f)
4-Chloro-benzaldehyde (2g)
2-Chloro-benzaldehyde (2h)
4-Bromobenzaldehyde (2i)
4-Iodobenzaldehyde (2j)
10
11
12
13
14
4-(Trifluoromethyl)benzaldehyde (2k)
(E)-Cinnamaldehyde (2l)
Naphthalene-2-carbaldehyde (2m)
Naphthalene-1-carbaldehyde (2n)
a
b
c
◦
Conditions: solvent, PhCH3; 0 C; concentration of 2, 0.25 M; ZnEt2, in hexane solution.
Isolated yields.
[2a,7b,11,12]
The ee was determined by chiral GC G-TA column, and the (S)-configuration was confirmed by comparison with the reported configuration.
d
e
[2a,7b,11,12]
The ee was determined by using a Chiral OD-H or OD column.
The ee was determined by using a Chiral OJ-H column.[2a,7b,11,12]
summarized in Table 3. In comparison to the results obtained
with 2a, the electron-donating substituents, the methyl group,
led to a decrease in the ee of the products 3b and c after a
longer time (Table 4, entries 2 and 3 vs entry 1). In the case of
stronger electron-donating substituents, the MeO group, lower
yields but comparable ee to 3b (Table 4, entries 4 and 5 vs entry
3a–n were obtained (Table 4), with electron-donating and bigger
substituted aromatic aldehydes giving less favorable results than
electron-withdrawing substituted aromatic aldehydes. These re-
sults revealed that the 1g catalyst system was effective for the
1,2-addition of diethylzinc to various aromatic aldehydes.
2
) were obtained. Electron-withdrawing groups (F, Cl, Br, I and
Catalytic Cycle Considerations
CF3, Table 4, entries 6–11) showed variation in the yields, but
no major differences in the ees of 3f–j. (E)-cinnamaldehyde only
gave 37% yield with 42% ee (Table 4, entry 12). Reaction of a-
and β-naphthaldehydes 2j and 2k resulted in up to 82 and 70%
ee, respectively (Table 4, entries 13 and 14). In general, moderate
to good yields and enantioselectivities of the secondary alcohols
According to previous works in the field of the enantioselective
addition of diethylzinc to aromatic aldehydes,[
complex might play multiple roles in the 1,2-addition reaction,
as described in our previous report. [ The expected active
species could be generated from the solution of 1g and ZnEt2
1–9]
the Zn (II)
6a]
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Copyright ꢀc 2011 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2011, 25, 448–453

Enantioselective addition of diethylzinc to aromatic aldehydes
by coordination between the TsNH and CONH groups.[6a,11–14]
When the benzaldehyde (2a) is added to the mixture, the metal
moiety (Zn) might act as a Lewis acid to activate the benzaldehyde
products were purified using column chromatography on silica
gel (EA-hexane) and recrystallized from a mixture of EA : hexane
(10 : 1 to 5 : 1, v/v). The corresponding products were obtained as
white solids in 85–87% yield.
(2a) and engender other species. Then the product 3a could be
obtained by working up with aqua acid (HCl) and one catalytic
cycle accomplished.
(
S)-N-Benzhydryl-3-phenyl-2-(toluene-4-sulfonylamino)-
propionamide (1e)
Conclusion
11
7
7
8
In summary, the chiral ligand 1g, the sulfonamide-
protected
ethyl)-2-(tosylamino)propanamide
derivative
of
(2S)-3-phenyl-N-((R)-1-phenyl-
readily prepared in
8
O
several steps from commercially available (R)-α-phenylethylamine
and L-phenylalanine, showed good catalytic activities and
moderate enantioselectivities (up to 82% ee) with asymmetric
addition of diethylzinc to various aromatic aldehydes. Further
investigation on the applications of these ligands for other
asymmetric reactions is ongoing.
2
10
9
1
6
15
6
1
8
4
7
N
H
2
12
14
13
NH
S
1
0
8
11
9
7
5
O
3
17
Experimental Section
O
13
6
General Remarks
◦
20
White solid, 85% yield, m.p.181–183 C, [a]D = −13.32 (CH2Cl2).
All reactions were conducted in oven-dried glassware under an
inert atmosphere of nitrogen with anhydrous solvents unless
stated otherwise. The solvents were purified and dried according
to standard procedures. Analytical thin-layer chromatography
1
H NMR (300 MHz, CDCl3) δ (ppm) 7.55 (d, J = 8.4 Hz, 2H,
NH), 7.07–7.39 (m, 16H, ArH), 6.87–6.94 (m, 3H, ArH), 6.11 [d,
J = 8.1 Hz, 1H, -NHCH(Ph)2], 3.96 [dd, J1 = 6.6 Hz, J2 = 19.2 Hz,
1
2
H, -CH2CH(NHTS)CO-], 3.02–3.09 [m, 2H, PhCH2CH(TsNH)CO-],
(
(
TLC) was performed on alumina- or glass-backed silica plates
GF254, 250 micron thickness) and visualized with UV light. Flash
13
.38 (s, 3H, -NHTsPhCH3). C NMR (75 MHz, CDCl3) δ (ppm) 169.2
C1), 144.1 (C2), 141.1 (C3), 140.7 (C4),134.5 (C5), 129.5 (C6), 129.3
C7), 129.1 (C8), 128.7 (C9), 128.6 (C10), 127.6 (C11), 127.5 (C12),
(
(
column chromatography was carried out on silica gel 60 (250–400
mesh) under air pressure. Enantiomeric ratios of the products
were determined using chiral GC G-TA and HPLC OJ-H, OD-H or OD
columns(UVdetector,254 nm).Specificrotationsweredetermined
1
27.3 (C13), 57.2 (C14), 57.6 (C15), 38.2 (C16), 21.6 (C17) ppm.
+
HRMS (ESI): calcd for (M + 1) for C29H29N2O3S, 485.1899; found,
4
85.1908. Anal. calcd for C29H29N2O3S, C, 71.87%; found, 71.99%;
2
2
as [α]D (c = 0.5 g/ml in CH2Cl2). Melting points are uncorrected.
H NMR (300 MHz) and C NMR (75 MHz) chemical shifts in CDCl3
are quoted as δ values relative to TMS (δ = 0.00) and CDCl3
H, 5.82%, found, 5.96%; N, 5.78%, found, 5.96%.
1
13
(
S)-N-(3,5-Bis-trifluoromethyl-benzyl)-3-phenyl-2-(toluene-4-
sulfonylamino)-propionamide ( 1f)
(
δ = 77.0), respectively, in ppm and coupling constants in Hz.
The following abbreviations are used to indicate the multiplicity:
s, singlet; d, doublet; t, triplet; q, quartet; m, multiplet. High-
resolution mass spectra (HRMS) were obtained using positive
electrospray ionization (m/z values are given).
17
6
2
F
6
11
Materials
13
4
F
9
F
1
1
L-Phenylalanine, diethylzinc (ZnEt2), PCl5, Ti(i-OPr)4, all aromatic
aldehydes and all amines were commercially available and used
without further purification, unless otherwise noted. 3-Phenyl-2-
O
7
5
S
8
1
0
12
5
HN
14
O
(toluene-4-sulfonylamino)propionylchloride(4a)wassynthesized
H
N
F
3
[
6a,10]
according to the literature.
are known compounds and were synthesized according to the
literature procedures.[
The ligands 1a–d and g–i
7
1
2
13
8
16
9
15
F
6a,10]
F
O
General Procedure for the Synthesis of Ligands 1e–f
◦
2
0
Slightly yellow solid, 87% yield, m.p.142–144 C, [a]D − 15.08
1
3-Phenyl-2-(toluene-4-sulfonylamino)-propionyl
chloride
(CH2Cl2). H NMR (300 MHz, CDCl3) δ (ppm) 7.71 (s, 1H, ArH), 7.50
(
405 mg, 1.2 mmol) was added to a solution of the corre-
(d, J = 5.4 Hz, 2H, NH), 7.24 (d, J = 8.1 Hz, 2H,ArH), 6.86–7.21
(m, 7H, ArH), 6.84 (d, J = 6.9 Hz, 2H), 4.51 [d, J = 6.0 Hz, 2H,
-CONHCH2(3,5,-CF3Ph)], 3.90 [dd, J1 = 6.3 Hz, J2 = 12.6 Hz, 1H,
TsNHCH(Bn)CONH-], 2.85–3.01 [m, 2H, PhCH2CH(TsNH)CONH-],
2.44 (s, 3H, -PhCH3) ppm. C NMR (75 MHz, CDCl3) δ (ppm) 170.7
(C1), 144.3 (C2), 141.1 (C2), 140.6 (C3), 134.7 (C4), 129.9 (C5), 129.0
(C6), 128.9 (C7), 127.5 (C8), 127.2 (9), 125.7 (C10), 125.1 (C11), 121.4
sponding amine (1.0 mmol) and Et3N (0.21 ml, 1.5 mmol) in
CH2Cl2 (10 ml) at 22 C. After stirring for 2 h (TLC), the reaction
mixture was diluted with CH2Cl2 (50 ml), washed with aqueous
HCl (1.0 M, 2 × 20 ml), aqueous K2CO3 (1.0 M, 2 × 20 ml) and then
brine (2 × 20 ml). The organic layer was dried over MgSO4, filtered
and evaporated to dryness on a rotary evaporator. The crude
◦
1
3
Appl. Organometal. Chem. 2011, 25, 448–453
Copyright ꢀc 2011 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/aoc

S. Gou et al.
(
C12), 120.2 (C13), 57.8 (C14), 50.2 (C15), 37.7 (C16), 22.6 (C17)
(S)-1-(2-Chloro-phenyl)-propan-1-ol (3h)2b,6a,7b,12–13
+
ppm. HRMS (ESI): calcd for (M + 1) for C25H23F6N2O3S, 545.1334;
Enantiomeric excess was determined on a chiral GC G-TA column
found, 545. 1349. Anal. calcd for C25H23F6N2O3S, C, 55.14%; found,
◦
(
135 C, 3.0 ml/min, tR = 11.2 min, tR = 11.7 min).
5
5.23%; H, 4.07%, found, 4.18%; N, 5.14%, found, 5.26%.
(
S)-1-(4-Bromo-phenyl)-propan-1-ol (3i)2b,6a
A Typical Procedure for the Catalytic Addition of Diethylzinc
to Aromatic Aldehydes
Enantiomeric excess was determined on a chiral GC G-TA column
◦
(130 C, 3.0 ml/min, tR = 15.9 min, tR = 15.2 min).
To a solution of 1g (10.6 mg, 0.025 mmol) in PhCH3 (1.0 ml), a
solution of diethylzinc (1.0 M in hexane, 0.375 ml, 0.375 mmol) was
added under a nitrogen atmosphere at 0 C, and the reaction
(
S)-1-(4-Iodo-phenyl)-propan-1-ol (3j)2b,6a
◦
mixture was stirred for 30 min at room temperature (about
Enantiomeric excess was determined on a chiral GC G-TA column
(130 C, 3.0 ml/min, tR = 29.5 min, tR = 28.0 min).
◦
◦
◦
2
0 C). The reaction mixture was then cooled to 0 C, and the
corresponding aromatic aldehyde (0.25 mmol) was added and
stirring was continued for stated times. The reaction mixture was
S)-1-(4-Trifluoromethyl-phenyl)-propan-1-ol(3k)2b,6a,7b
(
◦
quenched with HCl (1.0 M, 2.0 ml) at 0 C, and the product was
Enantiomeric excess was determined on
a chiral HPLC
extractedwith(3×5 ml)ethylacetate. Thecombinedethylacetate
extracts were dried over Na2SO4 and evaporated to dryness
under vacuum pressure. The residue was purified by silica gel
column chromatography (hexane : ethyl acetate, 10 : 1, v/v) to
afford the secondary alcohol products. The enantioselectivities of
the reactions were determined by chiral GC G-TA, OJ-H or OD-H
columns. Compounds 3a–n are known compounds; they were
OJ-H (UV detector, 254 nm, hexane : i-PrOH = 98 : 2, 1.0 ml/min,
tR = 17.9 min, tR = 16.4 min).
(S)-(E)-1-Phenyl-pent-1-en-3-ol (3l)2b,6a,7b,11,12
Enantiomeric excess was determined on a chiral HPLC OD-
H (UV detector, 254 nm, hexane : i-PrOH = 9 : 1, 1.0 ml/min,
tR = 13.5 min, tR = 9.1 min).
1
13
characterized by comparing their H and C NMR spectra with
the literature.[
2a,6a,7b,11,12]
(
S)-2-Naphthalen-2-yl-propan-1-ol (3m)2b,6a,7b,11,12
(
S)-1-Phenyl-propan-1-ol (3a)2b,6a,7b,11,12
Enantiomeric excess was determined on a chiral HPLC OD-
H (UV detector, 254 nm, hexane : i-PrOH = 9 : 1, 1.0 ml/min,
t = 10.1 min, t = 9.4 min).
Enantiomeric excess was determined on a chiral GC G-TA column
◦
(100 C, 2.0 ml/min, tR = 9.0 min, tR = 9.2 min).
R
R
S)-1-p-Tolyl-propan-1-ol (3b)2b,6a,7b,11,12
(
S)-1-Naphthalen-2-yl-propan-1-ol (3n)2b,6a,7b,11,12
(
Enantiomeric excess was determined on a chiralcel HPLC OD
column (UV detector, 254 nm, 4 : 96 i-PrOH : hexane, 0.5 ml/min
tR = 31 min, tR = 27 min).
Enantiomeric excess was determined on a chiral GC G-TA column
◦
(115 C, 2.0 ml/min, tR = 13.7 min, tR = 13.4 min).
(
S)-1-o-Tolyl-propan-1-ol (3c)2b,6a,7b,11,12
Acknowledgment
Enantiomeric excess was determined on a chiral GC G-TA column
The authors gratefully acknowledge the Open Fund (no. PLN0908)
of the Key Laboratory of Oil and Gas Reservoir Geology
and Exploitation (Southwest Petroleum University) for financial
support.
◦
(115 C, 2.0 ml/min, tR = 14.2 min, tR = 12.7 min).
(
S)-1-(4-Methoxy-phenyl)-propan-1-ol (3d)2b,6a,11,12
Enantiomeric excess was determined on a chiral GC G-TA column
◦
(
110 C, 2.0 ml/min, tR = 41.1 min, tR = 39.7 min).
References
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