Enantioselective synthesis of optically active 3,3-diarylpropanoates by conjugate hydrosilylation with chiral Rh-bis(oxazolinyl)phenyl catalysts

Article abstract of DOI:10.1021/jo302357b

Conjugate hydrosilylation of 3,3-diarylacrylate derivatives catalyzed by chiral rhodium-bis(oxazolinyl)phenyl complexes (1 mol %) at 60 C for 2 h was investigated to prepare optically active 3,3-diarylpropanoate derivatives in high yields up to 99% yield and high enantioselectivities up to 99%.

Full text of DOI:10.1021/jo302357b

Article
pubs.acs.org/joc
Enantioselective Synthesis of Optically Active 3,3-Diarylpropanoates
by Conjugate Hydrosilylation with Chiral Rh-bis(oxazolinyl)phenyl
Catalysts
Kengou Itoh, Ayae Tsuruta, Jun-ichi Ito, Yoshihiko Yamamoto, and Hisao Nishiyama*
Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Chikusa, Nagoya 464-8603 Japan
S
* Supporting Information
ABSTRACT: Conjugate hydrosilylation of 3,3-diarylacrylate
derivatives catalyzed by chiral rhodium-bis(oxazolinyl)phenyl
complexes (1 mol %) at 60 °C for 2 h was investigated to
prepare optically active 3,3-diarylpropanoate derivatives in
high yields up to 99% yield and high enantioselectivities up to
99%.
new routes for synthesizing fine chemicals such as pharma-
ceutical compounds or functional materials can lead to the
development of new reagents or reactions.
Yamamoto et al. recently discovered a method for synthesiz-
ing 3,3-diarylacrylates with stereoselective control of cis and
trans isomers by copper-catalyzed conjugate addition of an
arylboronic acid to alkynoates (Scheme 2).5 Therefore, we
INTRODUCTION
■
Asymmetric conjugate reduction of 3,3-disubstituted α,β-
unsaturated carbonyl compounds has been extensively studied
to obtain optically active propanoates having a chiral carbon
center at the β-position (Scheme 1).1 For example, such a
Scheme 1. Asymmetric Conjugate Reduction of 3,3-
Disubstituted Acrylates
Scheme 2. Completely Stereoselective Preparation of 3,3-
Diaryl Substituted Acrylates Developed by Yamamoto
adopted this method to prepare 3,3-diarylacrylate substrates,
which are subsequently subjected to asymmetric conjugate
reduction to afford optically active 3,3-diarylpropanoates, as
precursors for various pharmaceutical compounds (Figure 1).6
In terms of the asymmetric conjugate reduction, Yun et al.
successfully demonstrated copper-catalyzed hydrosilylation of
3,3-diaryl-substituted acrylonitriles to produce 3,3-diarylpropio-
nitriles in high enantioselectivities.7 Yun et al. adopted the
Horner−Wadsworth−Emmons olefination reaction7a and also
Yamamoto’s method for stereoselective preparation of the
starting 3,3-diaryl-substituted nitriles.7b,c Andersson et al.
employed an iridium-catalyzed asymmetric hydrogenation
reaction for trisubstituted olefins including 3,3-diarylacrylate,
which afforded a little lower enantioselectivity compared to that
of alkyl- or aryl-substituted olefins where the unsaturated olefin
substrate was prepared by Heck reaction.8 In 2011, Correia et
al. reported stereoselective synthesis of 3,3-diaryl-substituted
conjugate reduction was realized by catalytic hydrosilylation
using a variety of metal catalysts.2,3 We have reported the
conjugate hydrosilylation of α,β-unsaturated esters using chiral
rhodium-bis(oxazolinyl)phenyl acetate complexes (1) [Rh-
(Phebox)(OAc)2(H2O)] as catalysts and hydrosilanes as
reducing agents.4 In the reaction, we adopted linear β,β-
aryl,alkyl- or alkyl,alkyl-substituted unsaturated compounds as
substrates.
Methods in organic synthesis often depend on the supply of
starting substrates. Once a new substrate can stably be supplied,
Received: October 29, 2012
Published: November 10, 2012
© 2012 American Chemical Society
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and enantioselectivity (entry 6). The benzyl catalyst 1d gave
decreased enantioselectivity (entry 7).
Next, the substrate scope was examined using ethyl acrylates
under the standard conditions as described in entry 1 of Table
1; 1.0 mmol of the acrylate, 1.5 equiv of diethoxymethylsilane, 1
mol % of the catalyst 1a, 60 °C, 2 h (Table 2). Reduction of the
Table 2. Asymmetric Conjugate Hydrosilylation of (E)-Ethyl
3-(Substituted aryl)-3-phenylacrylates 2 with Rh(Phebox-ip)
a
Complex 1a
Figure 1. Diaryl substituted chiral carbon atoms in pharmaceutical
compounds.
acrylates by Heck−Matsuda reaction followed by a conjugate
reduction to afford a psychoactive compound.9
RESULTS AND DISCUSSION
■
Conjugate hydrosilylation of (E)-3-(p-methoxyphenyl) and 3-
(phenyl) disubstituted acrylate 2a (1.0 mmol scale) was
examined with 1 mol % of Rh(Phebox-R) complexes 1 and
diethoxymethylsilane (1.5 mmol) in toluene at 60 °C (Table
1). The desired reaction took place within 1 h. After acidic
Table 1. Asymmetric Conjugate Hydrosilylation of (E)-Ethyl
3-(p-Methoxyphenyl)-3-phenylacrylate 2a with Rh(Phebox-
a
R) Complexes 1
entry
1
cat. (R)
time (h)
yield (%)
ee (%)
1a (ip)
1a (ip)
1a (ip)
1b (sb)
1b (sb)
1c (ph)
1d (bn)
2
2
97
94
97
96
96
90
94
95
95
96
94
94
93
79
b
2
c
3
10
2
4
b
5
d
2
6
12
2
7
a
Acrylate 2a (1.0 mmol), Rh(Phebox-R) cat. 1 (1 mol %),
(EtO)2MeSiH (1.5 mmol), toluene (2 mL) at 60 °C, then acidic
b
c
workup. (EtO)3SiH (1.5 mmol). Acrylate 2a (5.0 mmol, 1.41 g),
Rh(Phebox-ip) cat. 1a (0.2 mol %, 0.01 mmol, 5.4 mg), (EtO)2MeSiH
(7.5 mmol), toluene (10 mL) at 60 °C, 10 h, then acidic workup.
a
d
Acrylate 2 (1.0 mmol), Rh(Phebox-ip) cat. 1a (1 mol %),
Catalyst 1d (2 mol %).
(EtO)2MeSiH (1.5 mmol), toluene (2 mL), at 60 °C, 2 h, then
acidic workup.
workup, the desired conjugate reduction product, 3,3-diary-
lpropanoate 3a, was obtained in 97% yield with 95% ee (entry
1). Triethoxysilane gave almost the same result (entry 2). The
reduction of gram scale substrate was carried out with 0.2 mol
% (TON 500) of the catalyst 1a at 60 °C to proceed for 10 h,
giving the corresponding product in 97% and 96% ee (entry 3).
The secondary butyl catalyst 1b gave almost the same results as
those with the isopropyl catalyst 1a (entries 4 and 5). The
phenyl catalyst 1c retarded the reduction to give similar yield
substrates substituted at the para-position (2b−2e), at the
meta-position (2f−2i), and at the ortho-position (2j) proceeded
smoothly to give the corresponding propanoates 3b−3j in over
90% yields with 95−98% ee's. Large steric effects of the
substituents on the yields and ee's were not observed.
Reduction of the bulky 1-naphthyl acrylate 2k proceeded
smoothly under the same condition to give the highest ee of
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(1/10) to give 2a as white solids (2.56 g, 9.08 mmol, 88% yield); mp
48 °C; IR (KBr) ν 1717, 1600, 1255, 1154, 1034, 834 cm−1; 1H NMR
δ 1.11 (t, J = 7.2 Hz, 3H), 3.82 (s, 3H), 4.04 (q, J = 7.2 Hz, 2H), 6.31
(s, 1H, CCH), 6.84 (d, J = 9.0 Hz, 2H), 7.18−7.22 (m, 2H), 7.30
(d, J = 9.2 Hz, 2H), 7.35−7.40 (m, 3H) ppm; 13C NMR δ 14.2, 55.4,
59.9, 113.6, 115.2, 127.6, 127.8, 128.8, 129.5, 132.8, 139.0, 156.0,
160.4, 165.9 ppm; HRMS-FAB (m/z, M = C18H18O3) 305.1157 [M +
Na]+, calcd 305.1154.
99%, in comparison to that of 95% ee for 2-naphthyl one 2l. 9-
Phenanthrenyl acrylate 2m was also reduced, giving the product
with a high ee of 97%. Next, the Z-acrylates 4 and 5 were
reduced under the same standard conditions with catalyst 1a.
The absolute configurations of products 3a and 3e were
confirmed to be R, which is opposite to those of the
corresponding propanoates 3a and 3e derived from E-acrylates
2a and 2e, respectively. This phenomenon can be explained by
the fact that the Rh(Phebox) catalyst differentiates the prochiral
face of the α-carbon atom, but not that of the β-carbon atom.
Replacement of the ethyl ester, with the methyl and isopropyl
esters 6 and 8 gave similar high enantioselectivity for the
products 7 and 9, respectively (up to 98% ee). Comparing to
the case of asymmetric hydrogenation of the methyl ester 6,
even Andersson’s excellent iridium-catalyst system giving high
enantioselectivity resulted in 69% ee.8a
Heteroaromatic substituted esters were expected as raw
materials for some of the pharmaceutical compounds. However,
the starting pyridyl substituted esters, 10 and 11, were not
successfully synthesized by Yamamoto’s method. Therefore,
these esters were synthesized by the Horner−Wadsworth−
Emmons method, followed by separation of the Z and E
isomers by column chromatography. Unfortunately, the
conjugate hydrosilylation of both isomers did not smoothly
proceed under the standard conditions.
(E)-Ethyl 3-Phenyl-3-(p-tolyl)acrylate (2b).5 Colorless oil; IR
1
(KBr) ν 1723, 1608, 1266, 1160, 1038, 820, 700 cm−1; H NMR δ
1.11 (t, J = 7.2 Hz, 3H), 2.36 (s, 3H), 4.04 (q, J = 7.2 Hz, 2H), 6.35 (s,
1H), 7.10−7.25 (m, 6 H), 7.37−7.42 (m, 3H) ppm; 13C NMR δ 14.3,
21.6, 60.1, 116.4, 127.7, 127.9, 128.1, 128.9, 129.0, 137.8, 139.0, 139.5,
156.4, 166.0 ppm; HRMS-FAB (m/z, M = C18H19O2) 267.1398 [M +
H]+, calcd 267.1385.
(E)-Ethyl 3-(4-Chlorophenyl)-3-phenylacrylate (2c).5 Colorless
oil; IR (KBr) ν 1720, 1617, 1488, 1265, 1163, 1092, 1035, 830, 700
1
cm−1; H NMR δ 1.12 (t, J = 7.2 Hz, 3H), 4.05 (q, J = 7.2 Hz, 2H),
6.34 (s, 1H), 7.15−7.33 (m, 6H), 7.35−7.43 (m, 3H) ppm; 13C NMR
δ 14.2, 60.2, 117.6, 127.8, 128.1, 128.4, 128.8, 129.3, 135.2, 138.2,
139.0, 154.8, 165.5 ppm; HRMS-FAB (m/z, M = C17H15ClO2)
309.0672 [M + Na]+, calcd 309.0658.
(E)-Ethyl 4-(3-Ethoxy-3-oxo-1-phenylprop-1-en-1-yl)-
benzoate (2d). Colorless oil; IR (KBr) ν 1719, 1614, 1274, 1165,
1105, 1022, 776, 700 cm−1; 1H NMR δ 1.13 (t, J = 6.9 Hz, 3H), 1.40
(t, J = 7.05 Hz, 3H), 4.07 (q, J = 7.1 Hz, 2H), 4.38 (q, J = 7.1 Hz, 2H),
6.41 (s, 1H), 7.10−7.20 (m, 2H), 7.30−7.40 (m, 5H), 7.99 (d, J = 6.9
Hz, 2H) ppm; 13C NMR δ 14.1, 14.5, 60.3, 61.1, 118.9, 127.8, 128.0,
128.1, 128.8, 129.3, 130.7, 138.0, 144.7, 154.8, 165.4, 165.7 ppm;
HRMS-FAB (m/z, M = C20H20O4) 347.1249 [M + Na]+, calcd
347.1259.
(E)-Ethyl 3-Phenyl-3-(4-(trifluoromethyl)phenyl)acrylate
(2e). Colorless oil; IR (KBr) ν 1724, 1325, 1169, 1127, 1068, 842,
1
700 cm−1; H NMR δ 1.13 (t, J = 7.1 Hz, 3H), 4.08 (q, J = 7.1 Hz,
2H), 6.39 (s, 1H), 7.18−7.22 (m, 2H), 7.38−7.42 (m, 5H), 7.58 (d, J
= 8.4 Hz, 2H) ppm; 13C NMR δ 14.2, 60.4, 119.2, 125.1 (CF3), 127.9,
128.3, 128.4, 128.8, 130.6, 131.1, 137.9, 144.1, 154.4, 165.4 ppm;
HRMS-FAB (m/z, M = C18H15F3O2) 340.0915 [M + Na]+, calcd
343.0922.
Finally, a proposed hydride attack transition structure is
shown in Figure 2, in which the hydride attacks the re face of
the acrylate (Ar1 > Ar2) to form the S absolute configuration.
(E)-Ethyl 3-(3-Methoxyphenyl)-3-phenylacrylate (2f). Color-
1
less oil; IR (KBr) ν 1718, 1598, 1277, 1162, 1040 cm−1; H NMR δ
1.12 (t, J = 7.2 Hz, 3H), 3.78 (s, 3H), 4.05 (q, J = 7.2 Hz, 2H), 6.36 (s,
1H, CCH), 6.83−6.92 (m, 3H), 7.18−7.25 (m, 3H), 7.35−7.42 (m,
3H) ppm; 13C NMR δ 14.2, 55.3, 60.1, 113.7, 114.6, 117.4, 120.7,
127.6, 127.9, 128.8, 129.1, 138.6, 141.9, 156.0, 159.1, 165.7 ppm;
HRMS-FAB (m/z, M = C18H18O3) 305.1141 [M + Na]+, calcd
305.1154.
(E)-Ethyl 3-Phenyl-3-(m-tolyl)acrylate (2g). Colorless oil; IR
(KBr) ν 1722, 1599, 1271, 1203, 1038, 699 cm−1; 1H NMR δ 1.22 (t, J
= 7.2 Hz, 3H), 2.33 (s, 3H), 4.05 (q, J = 7.2 Hz, 2H), 6.35 (s, 1H),
7.10−7.30 (m, 6H), 7.35−7.43 (m, 3H) ppm; 13C NMR δ 14.4, 21.7,
60.2, 117.3, 125.5, 127.8, 128.0, 128.2, 128.8, 129.0, 130.1, 137.9,
138.9, 140.7, 156.6, 165.9 ppm; HRMS-FAB (m/z, M = C18H19O2)
267.1376 [M + H]+, calcd 267.1385.
Figure 2. Hypothetical course of the hydride attack to 3,3-
diarylacrylate forming S absolute configuration.
Thus we have found highly enantioselective conjugate
reduction of 3,3-diaryl-substituted acrylates by hydrosilylation
with Rh(Phebox) complexes to produce optically active 3,3-
diaryl propanoates. Study is now underway on substrate scope
toward the corresponding enones, amides, and nitriles having
heteroaromatic rings.
(E)-Ethyl 3-(3-Chlorophenyl)-3-phenylacrylate (2h). Colorless
1
oil; IR (KBr) ν 1723, 1257, 1161, 1036, 874, 788 cm−1; H NMR δ
1.12 (t, J = 7.2 Hz, 3H), 4.05 (q, J = 7.2 Hz, 2H), 6.34 (s, 1H), 7.15−
7.45 (m, 9H) ppm; 13C NMR δ 14.2, 60.2, 118.4, 126.2, 127.8, 128.0,
128.2, 128.8, 129.1, 129.4, 134.2, 138.0, 142.4, 154.6, 165.4 ppm;
HRMS-FAB (m/z, M = C17H15ClO2) 309.0649 [M + Na]+, calcd
309.0658.
(E)-Ethyl 3-(3-Ethoxy-3-oxo-1-phenylprop-1-en-1-yl)-
benzoate (2i). Colorless oil; IR (KBr) ν 1719, 1614, 1274, 1165,
1105, 1022, 776, 700 cm−1; 1H NMR δ 1.13 (t, J = 7.2 Hz, 3H), 1.39
(t, J = 7.2 Hz, 3H), 4.07 (q, J = 7.1 Hz, 2H), 4.38 (q, J = 7.1 Hz, 2H),
6.40 (s, 1H), 7.20 (m, 2H), 7.36−7.45 (m, 5H), 8.00−8.10 (m, 2H)
ppm; 13C NMR δ 14.1, 14.5, 60.2, 61.2, 118.2, 127.7, 128.1, 128.2,
128.6, 128.8, 130.0, 130.5, 132.5, 138.1, 140.9, 155.4, 165.5, 165.7
ppm; HRMS-FAB (m/z, M = C20H20O4) 347.1249 [M + Na]+, calcd
347.1259.
EXPERIMENTAL SECTION
■
1H and 13C NMR were measured at 300 and 75 MHz in CDCl3,
respectively. HRMS were obtained on a double-focusing magnetic
sector mass spectrometer.
Typical Method for Preparation of Substrate 3,3-Diaryl
Acrylates. (E)-Ethyl 3-(4-Methoxyphenyl)-3-phenylacrylate
(2a).5 A mixture of ethyl phenylpropiolate (1.80 g, 10.3 mmol), p-
methoxyphenylboronic acid (2.52 g, 16.6 mmol), and CuOAc (7.2 mg,
0.059 mmol) in 20 mL of methanol was stirred overnight at room
temperature. The mixture was filtered through Celite-545, and the
filtrate was concentrated under vacuum pressure. The residue was
purified by silica gel column chromatography with EtOAc and hexane
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(E)-Ethyl 3-Phenyl-3-(o-tolyl)acrylate (2j). Colorless oil; IR
Typical Procedure for the Conjugate Hydrosilylation of 3,3-
Diarylacrylates. Reduction of (E)-Ethyl 3-(p-Methoxyphenyl)-3-
phenylacrylate 2a (Table 1, entry 1). To a solution of 2a (282 mg,
1.0 mmol) and Rh(Phebox-ip) 1a (5.4 mg, 0.01 mmol) in toluene (2.0
mL) was added diethoxymethylsilane (202 mg, 1.5 mmol) at 60 °C.
The mixture was stirred for 2 h. At 0 °C, THF (1 mL), MeOH (1
mL), and hydrochloric acid (1 N, 1 mL) were then added, and the
mixture was stirred for 1 h. The mixture was extracted with EtOAc,
and the extract was washed with aq NaHCO3 and saturated brine. The
organic layer was dried over MgSO4 and then concentrated to give the
residual oil, which was purified by silica gel column chromatography
with hexane and EtOAc (10/1) to give 3a as colorless oil (274 mg,
0.97 mmol, 97% yield); DAICEL CHIRALCEL OD-H, hexane/ipa =
97:3, 1 mL/min, 27 °C, tR = 7.9 min for R and 9.2 min for S, 95% ee;
1
(KBr) ν 1722, 1617, 1256, 1162, 1034, 763, 730 cm−1; H NMR δ
1.18 (t, J = 7.2 Hz, 3H), 2.07 (s, 3H), 4.12 (q, J = 7.1 Hz, 2H), 6.00 (s,
1H), 7.12−7.35 (m, 9H) ppm; 13C NMR δ 14.2, 20.5, 60.2, 119.9,
125.5, 127.4, 128.15, 128.17, 128.9, 129.3, 130.4, 135.7, 138.5, 141.6,
156.4, 166.0 ppm; HRMS-FAB (m/z, M = C18H18O2) 289.1195 [M +
Na]+, calcd 289.1204.
(E)-Ethyl 3-(Naphthalen-1-yl)-3-phenylacrylate (2k). White
solid; mp 55 °C; IR (KBr) ν 1720, 1614, 1275, 1162, 1032, 776,
1
699 cm−1; H NMR δ 1.20 (t, J = 6.9 Hz, 3H), 4.17 (q, J = 7.1 Hz,
2H), 6.20 (s, 1H), 7.27−7.44 (m, 9H), 7.85 (d, J = 7.8 Hz, 2H), 7.94
(d, J = 0.9 Hz, 1H) ppm; 13C NMR δ 14.2, 60.3, 121.1, 124.9, 125.5,
125.7, 126.2, 127.0, 127.6, 128.1, 128.3, 128.68, 128.70, 130.9, 133.5,
139.1, 139.5, 154.9, 165.9 ppm; HRMS-FAB (m/z, M = C21H18O2)
325.1209 [M + Na]+, calcd 325.1204.
[α]27 = −2.09 (c 1.00, CHCl3). For entry 3 of Table 1: 2a (1.41 g,
D
(E)-Ethyl 3-(Naphthalen-2-yl)-3-phenylacrylate (2l). White
5.00 mmol), Rh(Phebox-ip) 1a (5.34 mg, 0.0099 mmol), toluene (10
mL), (EtO)2MeSiH (1.01 g, 7.50 mmol), 60 °C, 10 h, the product 3a
(1.38 g, 4.85 mmol, 97%), 96% ee.
solid; mp 84 °C; IR (KBr) ν 1687, 1590, 1367, 1279, 1254, 1037,
1
823, 751, 700 cm−1. H NMR δ 1.14 (t, J = 7.2 Hz, 3H), 4.08 (q, J =
7.2 Hz, 2H), 6.50 (s, 1H), 7.20−7.80 (m, 12 H) ppm; 13C NMR δ
14.2, 60.1, 117.6, 124.9, 126.3, 126.7, 127.3, 127.7, 127.8, 128.0, 128.4,
128.6, 129.0, 132.7, 133.4, 137.8, 138.7, 156.1, 165.8 ppm; HRMS-
FAB (m/z, M = C21H18O2) 325.1209 [M + Na]+, calcd 325.1204.
(E)-Ethyl 3-(Phenanthren-9-yl)-3-phenylacrylate (2m). White
(S)-Ethyl 3-(4-Methoxyphenyl)-3-phenylpropanoate (3a).10
IR (KBr) ν 1732, 1510, 1250, 1154, 1033, 830 cm−1; 1H NMR δ 1.12
(t, J = 6.9 Hz, 3H), 3.02 (d, J = 8.4 Hz, 2H), 3.77 (s, 3H), 4.04 (q, J =
7.2 Hz, 2H), 4.50 (t, J = 8.1 Hz, 1H), 6.84 (d, J = 8.7 Hz, 2H), 7.17−
7.36 (m, 7H) ppm; 13C NMR δ 14.2, 41.1, 46.3, 55.2, 60.4, 113.7,
126.2, 127.3, 128.2, 128.4, 135.3, 143.5, 157.8, 171.5 ppm; HRMS-
FAB (m/z, M = C18H20O3) 307.1322 [M + Na]+, calcd 307.1310. The
racemic propanoate was prepared by hydrogenation of acrylates with
Pd/C catalyst under hydrogen atmosphere (1 atm) in ethanol.
(S)-Ethyl 3-Phenyl-3-(p-tolyl)propanoate (3b).11 2b (270 mg,
1.02 mmol), 3b (246 mg, 0.92 mmol, 90% yield); colorless oil;
DAICEL CHIRALCEL OD-H, hexane/ipa = 99:1, 1 mL/min, 27 °C,
1
solid; mp 83 °C; IR (KBr) ν 1715, 1614, 1159, 750, 699 cm−1; H
NMR δ 1.22 (t, J = 7.1 Hz, 3H), 3.85 (s, 3H), 4.19 (q, J = 7.1 Hz, 2H),
6.30 (s, 1H), 7.28−7.30 (m, 3H), 7.39−7.49 (m, 3H), 7.57−7.72 (m,
4H), 7.88−7.92 (m, 2H), 8.66−8.71 (m, 4H) ppm; 13C NMR δ 14.2,
60.4, 121.0, 122.3, 122.7, 126.4, 126.5, 126.6, 126.7, 127.0, 127.6,
127.7, 128.4, 128.7, 128.8, 129.9, 130.2, 130.4, 130.8, 138.2, 138.5,
155.0, 166.0 ppm; HRMS-FAB (m/z, M = C25H20O2) 375.1370 [M +
Na]+, calcd 375.1361.
(Z)-Ethyl 3-(4-Methoxyphenyl)-3-phenylacrylate (4). Ethyl p-
methoxyphenylpropiolate (682 mg, 3.34 mmol), phenylboronic acid
(647 mg, 5.31 mmol), Cu(OAc)2 (16.3 mg, 0.089 mmol), MeOH (20
mL), 4 (826 mg, 2.93 mmol, 88%); colorless oil; IR (KBr) ν 1720,
1607, 1510, 1248, 834, 772 cm−1; 1H NMR δ 1.18 (t, J = 7.1 Hz, 3H),
3.85 (s, 3H), 4.10 (q, J = 7.2 Hz, 2H), 6.28 (s, 1H), 6.91 (d, J = 9.0
Hz, 2H), 7.16 (t, J = 9.0 Hz, 2H), 7.28−7.40 (m, 5H) ppm; 13C NMR
δ 14.3, 55.2, 60.0, 113.0, 116.6, 128.0, 128.3, 129.0, 130.6, 130.7, 141.2,
156.2, 159.3, 165.9 ppm; HRMS-FAB (m/z, M = C18H18O3) 305.1149
[M + Na]+, calcd 305.1154.
tR = 5.2 min for R and 6.1 min for S, 98% ee; [α]27 = +1.72 (c 0.99,
D
CHCl3); IR (KBr) ν 1735, 1254, 1154, 700 cm−1. 1H NMR δ 1.13 (t, J
= 7.2 Hz, 3H), 2.31 (s, 3H), 3.05 (d, J = 7.8 Hz, 2H), 4.05 (q, J = 7.2
Hz, 2H), 4.53 (t, J = 7.8 Hz, 1H), 7.08−7.33 (m, 9H) ppm; 13C NMR
δ 14.4, 21.3, 41.1, 46.9, 60.6, 126.4, 127.5, 127.6, 128.4, 129.2, 135.9,
140.4, 143.6, 171.7 ppm; HRMS-FAB (m/z, M = C18H20O2) 269.1533
[M + H]+, calcd 269.1542.
(S)-Ethyl 3-(4-Chlorophenyl)-3-phenylpropanoate (3c).12 2c
(287 mg, 1.00 mmol), 3c (268 mg, 0.927 mmol, 93% yield); colorless
oil; DAICEL CHIRALCEL OD-H, hexane/ipa = 99:1, 1 mL/min, 27
°C, tR = 9.7 min for R and 13.1 min for S, 98% ee; [α]20 = −1.58 (c
D
(Z)-Ethyl 3-Phenyl-3-(4-(trifluoromethyl)phenyl)acrylate (5).
Ethyl p-trifluoromethylphenylpropiolate (1.12 g, 4.61 mmol), phenyl-
boronic acid (841 mg, 6.89 mmol), Cu(OAc)2 (17.6 mg, 0.097 mmol),
MeOH (15 mL), 5 (580 mg, 1.81 mmol, 39%); brown solid; mp 58
1.00, CHCl3); IR (KBr) ν 1733, 1491, 1253, 1156, 1093, 1015, 823
1
cm−1; H NMR δ 1.13 (t, J = 7.2 Hz, 3H), 3.02 (d, J = 8.1 Hz, 2H),
4.04 (q, J = 7.2 Hz, 2H), 4.53 (t, J = 8.1 Hz, 1H), 7.15−7.40 (m, 9H)
ppm; 13C NMR δ 14.3, 40.8, 46.5, 60.6, 126.5, 127.3, 128.4, 128.8
(Cx2), 132.1, 141.7, 142.7, 171.2 ppm; HRMS-FAB (m/z, M =
C17H17ClO2) 311.0815 [M + Na]+, calcd 311.0815.
1
°C; IR (KBr) ν 1721, 1613, 1324, 1162, 1118, 837, 774 cm−1; H
NMR δ 1.13 (t, J = 7.2 Hz, 3H), 4.06 (q, J = 7.1 Hz, 2H), 6.44 (s, 1H),
7.24−7.28 (m, 2H), 7.32−7.34 (m, 5H), 7.65 (d, J = 7.8 Hz, 2H)
ppm; 13C NMR δ 14.1, 60.3, 118.0, 122.1, 124.7 (CF3), 126.7, 127.9,
128.4, 129.2, 129.5, 139.6, 142.5, 154.8, 165.3 ppm; HRMS-FAB (m/z,
M = C18H15F3O2) 343.0929 [M + Na]+, calcd 343.0922.
(S)-Ethyl 4-(3-Ethoxy-3-oxo-1-phenylpropyl)benzoate (3d).
2d (326 mg, 1.00 mmol), 3d (294 mg, 0.899 mmol, 90%); colorless
oil; DAICEL CHIRALCEL OD-H, hexane/ipa = 97:3, 1 mL/min, 27
°C, tR = 9.8 min for R and 11.5 min for S, 98% ee; [α]20 = 8.39 (c
D
(Z)-Methyl 3-(4-Methoxyphenyl)-3-phenylacrylate (6). Meth-
yl phenylpropiolate (748 mg, 4.67 mmol), p-methoxyphenylboronic
acid (1.0 g, 6.59 mmol), CuOAc (8.69 mg, 0.071 mmol), MeOH (20
mL), the product acrylate (1.02 g, 3.80 mmol, 81%); white solid; mp
70 °C; IR (KBr) ν 1724, 1597, 1269, 1158, 834, 700 cm−1; 1H NMR δ
3.60 (s, 3H), 3.82 (s, 3H), 6.29 (s, 1H), 6.84 (d, J = 8.7 Hz, 2H),
7.20−7.40 (m, 6H) ppm; 13C NMR δ 51.2, 55.4, 113.6, 114.5, 127.6,
127.9, 128.8, 129.6, 132.8, 138.8, 156.6, 160.5, 166.2 ppm; HRMS-
1.00, CHCl3); IR (KBr) ν 1718, 1609, 1277, 1105, 1022, 704 cm−1; 1H
NMR δ 1.12 (t, J = 7.2 Hz, 3H), 1.37 (t, J = 7.1 Hz, 3H), 3.07 (d, J =
7.8 Hz, 2H), 4.04 (q, J = 7.1 Hz, 2H), 4.35 (q, J = 7.1 Hz, 2H), 4.61 (t,
J = 7.95 Hz, 1H), 7.19−7.33 (m, 7H), 7.96 (d, J = 8.7 Hz, 2H) ppm;
13C NMR δ 14.2, 14.5, 40.5, 47.0, 60.6, 60.9, 126.6, 127.4, 127.5, 128.4,
128.6, 129.6, 142.4, 148.3, 166.0, 171.1 ppm; HRMS-FAB (m/z, M =
C20H22O4) 349.1426 [M + Na]+, calcd 349.1416.
+
(S)-Ethyl 3-Phenyl-3-(4-(trifluoromethyl)phenyl)propanoate
(3e). 2e (321 mg, 1.00 mmol), 3e (308 mg, 0.95 mmol, 95%);
colorless oil; DAICEL CHIRALCEL OD-H, hexane/ipa = 97:3, 1 mL/
FAB (m/z, M = C17H16O3) 291.0991 [M + Na] , calcd 291.0997.
(Z)-Isopropyl 3-(4-Methoxyphenyl)-3-phenylacrylate (8). Iso-
propyl phenylpropiolate (1.05 g, 5.56 mmol), p-methoxyphenylbor-
onic acid (1.2 g, 7.88 mmol), Cu(OAc)2 (9.95 mg, 0.0548 mmol),
MeOH (15 mL), 8 (1.10 g, 3.70 mmol, 67%); colorless oil; IR (KBr) ν
1715, 1600, 1510, 1254, 1166, 834, 700 cm−1; 1H NMR δ 1.09 (d, J =
6.3 Hz, 6H), 3.82 (s, 3H), 4.91 (q, J = 6.3 Hz, 1H), 6.29 (s, 1H), 6.84
(d, J = 9.0 Hz, 2H), 7.18−7.26 (m, 4H), 7.36−7.39 (m, 3H) ppm; 13C
NMR δ 21.8, 55.3, 67.1, 113.5, 115.8, 127.56, 127.63, 128.8, 129.4,
132.8, 139.1, 155.3, 160.3, 165.5 ppm; HRMS-FAB (m/z, M =
C19H20O3) 319.1312 [M + Na]+, calcd 319.1310.
min, 27 °C, tR = 5.7 min for R and 6.5 min for S, 97% ee; [α]20
=
D
−2.56 (c 1.00, CHCl3); IR (KBr) ν 1735, 1326, 1164, 1119, 1069, 700
1
cm−1; H NMR δ 1.13 (t, J = 6.9 Hz, 3H), 3.07 (d, J = 7.8 Hz, 2H),
4.05 (q, J = 7.0 Hz, 2H), 4.61 (t, J = 7.9 Hz, 1H), 7.20−7.37 (m, 7H),
7.54 (d, J = 8.1 Hz, 2H) ppm; 13C NMR δ 14.2, 40.5, 46.9, 60.7, 122.1,
125.3 (CF3), 126.7, 127.4, 127.8, 128.4, 128.5, 142.2, 147.2, 171.0
ppm; HRMS-FAB (m/z, M = C18H17F3O2) 345.1069 [M + Na]+,
calcd 345.1078.
10917
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The Journal of Organic Chemistry
Article
(S)-Ethyl 3-(3-Methoxyphenyl)-3-phenylpropanoate (3f).12
2f (282 mg, 1.00 mmol), the product (268 mg, 0.945 mmol, 94%
yield); colorless oil; DAICEL CHIRALCEL AS-H, hexane/ipa = 99:1,
1 mL/min, 27 °C, tR = 10.1 min for R and 12.4 min for S, 97% ee;
1017, 750, 703 cm−1; H NMR δ 1.11 (t, J = 7.1 Hz, 3H), 3.17 (m,
2H), 4.04 (q, J = 7.2 Hz, 2H), 4.73 (t, J = 8.0 Hz, 1H), 7.16−7.50 (m,
8H), 7.70−7.83 (m, 4H) ppm; 13C NMR δ 14.3, 40.8, 47.2, 60.5,
125.38, 125.42, 125.8, 126.3, 126.4, 127.3, 127.5, 127.6, 128.0, 128.3,
132.0, 133.2, 140.6, 143.0, 171.4 ppm; HRMS-FAB (m/z, M =
C21H20O2) 327.1365 [M + Na]+, calcd 327.1361.
1
[α]27 = +2.36 (c 1.01, CHCl3); IR (KBr) ν 1733, 1597, 1489, 1257,
D
1155, 1042, 868 cm−1; 1H NMR δ 1.12 (t, J = 7.2 Hz, 3H), 3.04 (d, J =
7.8 Hz, 2H), 3.76 (s, 3H), 4.04 (q, J = 7.2 Hz, 2H), 4.52 (t, J = 7.9 Hz,
1H), 6.70−6.90 (m, 3H), 7.15−7.33 (m, 6H) ppm;12 13C NMR δ
14.3, 40.8, 47.1, 55.1, 60.5, 111.3, 113.6, 119.8, 126.3, 127.4, 128.3,
129.3, 143.0, 144.8, 159.3, 171.4 ppm; HRMS-FAB (m/z, M =
C18H20O3) 307.1306 [M + Na]+, calcd 307.1310.
(S)-Ethyl 3-(Phenanthren-9-yl)-3-phenylpropanoate (3m).
2m (353 mg, 1.00 mmol), 3m (353 mg, 0.99 mmol, 99%); white
solid; mp 74 °C; DAICEL CHIRALCEL AD-H, hexane/ipa = 97:3, 1
mL/min, 27 °C, tR = 7.1 min for R and 7.9 min for S, 97% ee; [α]27
=
D
+157.9 (c 1.00, CHCl3); IR (KBr) ν 1714, 1297, 1267, 1148, 1026,
1
748, 701 cm−1; H NMR δ 1.12 (t, J = 7.1 Hz, 3H), 3.13−3.34 (m,
(S)-Ethyl 3-Phenyl-3-(m-tolyl)propanoate (3g). 2g (270 mg,
1.00 mmol), 3g (253 mg, 0.94 mmol, 94% yield); colorless oil;
DAICEL CHIRALCEL OD-H, hexane/ipa = 99:1, 1 mL/min, 27 °C,
2H), 4.01−4.12 (m, 2H), 5.37 (t, J = 7.8 Hz, 1H), 7.14−7.35 (m, 4H),
7.51−7.66 (m, 4H), 7.69 (s, 1H), 7.87 (m, 1H), 8.15 (m, 1H), 8.65
(m, 1H), 8.70 (m, 1H) ppm; 13C NMR δ 14.3, 41.6, 43.1, 60.6, 122.2,
122.9, 124.4, 124.8, 126.0, 126.3, 126.4, 126.47, 126.50, 127.7, 128.3,
128.4, 129.6, 130.5, 130.7, 131.1, 136.6, 142.9, 171.5 ppm; HRMS-
FAB (m/z, M = C25H22O2) 377.1509 [M + Na]+, calcd 377.1517.
(R)-Ethyl 3-(4-Methoxyphenyl)-3-phenylpropanoate ((R)-3a).
4 (282 mg, 1.00 mmol), 3a (262 mg, 0.924 mmol, 92% yield);
colorless oil; DAICEL CHIRALCEL OD-H, hexane/ipa = 97:3, 1 mL/
tR = 8.0 min for R and 8.4 min for S, 95% ee; [α]27 = +2.37 (c 1.11,
D
CHCl3); IR (KBr) ν 1736, 1255, 1155, 706 cm−1; 1H NMR δ 1.12 (t, J
= 7.2 Hz, 3H), 2.31 (s, 3H), 3.04 (d, J = 8.1 Hz, 2H), 4.04 (q, J = 7.2
Hz, 2H), 4.52 (t, J = 8.1 Hz, 1H), 6.97−7.10 (m, 3H), 7.13−7.34 (m,
6H) ppm; 13C NMR δ 14.4, 21.8, 41.1, 47.2, 124.5, 126.4, 127.2, 127.6,
128.3, 128.4, 138.0, 143.3, 143.5, 171.7 ppm; HRMS-FAB (m/z, M =
C18H20O2) 269.1546 [M + H]+, calcd 269.1542.
min, 27 °C, tR = 7.7 min for R and 9.4 min for S, 97% ee; [α]27
+3.18 (c 1.00, CHCl3).
=
(S)-Ethyl 3-(3-Chlorophenyl)-3-phenylpropanoate (3h). 2h
(286 mg, 1.00 mol), 3h (261 mg, 0.906 mmol, 91% yield); colorless
oil; DAICEL CHIRALCEL OD-H, hexane/ipa = 97:3, 1 mL/min, 27
°C, tR = 6.4 min for R and 7.9 min for S, 97% ee; [α]24D = 0.54 (c 0.99,
CHCl3); IR (KBr) ν 1733, 1252, 1157, 1082, 1029, 781, 701 cm−1; 1H
NMR δ 1.13 (t, J = 7.2 Hz, 3H), 3.03 (d, J = 8.1 Hz, 2H), 4.05 (q, J =
7.2 Hz, 2H), 4.52 (t, J = 7.9 Hz, 1H), 7.10−7.33 (m, 9H) ppm; 13C
NMR δ 14.2, 40.6, 46.8, 60.6, 125.7, 126.5, 126.6, 127.4, 127.7, 128.4,
129.6, 134.1, 142.4, 145.2, 171.8 ppm; HRMS-FAB (m/z, M =
C17H17ClO2) 311.0811 [M + Na]+, calcd 311.0815.
(S)-Ethyl 3-(3-Ethoxy-3-oxo-1-phenylpropyl)benzoate (3i). 2i
(327 mg, 1.01 mmol), 3i (311 mg, 0.954 mmol, 95%); colorless oil;
DAICEL CHIRALCEL OD-H, hexane/ipa = 97:3, 1 mL/min, 27 °C,
tR = 11.3 min for R and 12.5 min for S, 98% ee; [α]20D = 3.53 (c 1.00,
CHCl3); IR (KBr) ν 1721, 1280, 1186, 1105, 753, 701 cm−1; 1H NMR
δ 1.12 (t, J = 7.2 Hz, 3H), 1.39 (t, J = 7.2 Hz, 3H), 3.09 (d, J = 8.1 Hz,
2H), 4.04 (q, J = 7.1 Hz, 2H), 4.36 (q, J = 7.2 Hz, 2H), 4.61 (t, J = 8.0
Hz, 1H), 7.16−7.45 (m, 6H), 7.88 (d, J = 7.2 Hz, 1H), 7.96 (s, 1H)
ppm;13 13C NMR δ 14.2, 14.5, 40.7, 46.9, 60.6, 61.0, 126.5, 127.4,
127.6, 128.36, 128.41, 130.5, 132.1, 142.6, 143.5, 166.2, 171.2 ppm;
HRMS-FAB (m/z, M = C20H22O4) 349.1426 [M + Na]+, calcd
349.1416.
D
(R)-Ethyl 3-Phenyl-3-(4-(trifluoromethyl)phenyl)propanoate
((R)-3e). 5 (321 mg, 1.00 mmol), 3e (310 mg, 0.963 mmol, 96%
yield); brown oil; DAICEL CHIRALCEL OD-H, hexane/ipa = 97:3, 1
mL/min, 27 °C, tR = 5.7 min for R and 6.8 min for S, 97% ee; [α]26
+2.18 (c 1.00, CHCl3).
=
D
(S)-Methyl 3-(4-Methoxyphenyl)-3-phenylpropanoate (7).13
6 (269 mg, 1.00 mmol), 7 (258 mg, 0.95 mmol, 95% yield); white
solid; mp 49 °C; DAICEL CHIRALCEL OD-H, hexane/ipa = 97:3, 1
mL/min, 27 °C, tR = 9.6 min for R and 12.9 min for S, 98% ee; [α]28
D
= −3.16 (c 1.01, CHCl3); Lit13 [α]20D = −14.3 (c 0.51, CHCl3) for R;
IR (KBr) ν 1736, 1511, 1257, 1156, 1026, 831, 700 cm−1; 1H NMR δ
3.04 (d, J = 8.1 Hz, 2H), 3.59 (s, 3H), 3.77 (s, 3H), 4.52 (t, J = 8.0 Hz,
1H), 6.82 (d, J = 8.4 Hz, 2H), 7.10−7.35 (m, 7H) ppm; 13C NMR δ
40.8, 46.2, 51.7, 55.2, 113.7, 126.2, 127.3, 128.30, 128.34, 135.3, 143.5,
157.7, 172.0 ppm; HRMS-FAB (m/z, M = C17H18O3) 293.1145 [M +
Na]+, calcd 293.1154.
(S)-Isopropyl 3-(4-Methoxyphenyl)-3-phenylpropanoate (9).
8 (297 mg, 1.00 mmol), 9 (293 mg, 0.98 mmol, 98% yield); colorless
oil; DAICEL CHIRALCEL AD-H, hexane/ipa = 99:1, 1 mL/min, 27
°C, tR = 9.5 min for S and 10.3 min for R, 97% ee; [α]26 = −2.92 (c
D
1
1.01, CHCl3). IR (KBr) ν 1728, 1511,1251, 1107, 828, 700 cm−1; H
(S)-Ethyl 3-Phenyl-3-(o-tolyl)propanoate (3j). 2j (267 mg, 1.00
mmol), 3j (247 mg, 0.922 mmol, 92% yield); colorless oil; DAICEL
CHIRALCEL OD-H, hexane/ipa = 97:3, 1 mL/min, 27 °C, tR = 5.8
min for S and 7.1 min for R, 97% ee; [α]24D = +71.4 (c 1.01, CHCl3);
NMR δ 1.08 (d, J = 6.0 Hz, 6H), 2.99 (d, J = 8.4 Hz, 2H), 3.76 (s,
3H), 4.48 (t, J = 8.3 Hz, 1H), 4.89 (q, J = 6.0 Hz, 1H), 6.81(d, J = 8.7
Hz, 2H), 7.13−7.29 (m, 7H) ppm; 13C NMR δ 21.8, 41.4, 46.8, 55.2,
67.7, 113.6, 126.2, 127.4, 128.2, 128.4, 135.3, 143.5, 157.7, 171.0 ppm;
HRMS-FAB (m/z, M = C19H22O3) 321.1472 [M + Na]+, calcd
321.1467.
1
IR (KBr) ν 1734, 1253, 1155, 752, 700 cm−1. H NMR δ 1.12 (t, J =
7.1 Hz, 3H), 2.30 (s, 3H), 3.03 (d, J = 7.2 Hz, 2H), 4.04 (q, J = 7.1 Hz,
2H), 4.74 (t, J = 8.0 Hz, 1H), 7.10−7.30 (m, 9H) ppm; 13C NMR δ
14.2, 20.0, 41.3, 43.1, 60.4, 125.8, 126.0, 126,1, 126.3, 127.7, 128.2,
130.4, 136.1, 140.9, 142.8, 171.5 ppm; HRMS-FAB (m/z, M =
C18H20O2) 291.1351 [M + Na]+, calcd 291.1361.
(S)-Ethyl 3-(Naphthalen-1-yl)-3-phenylpropanoate (3k). 2k
(302 mg, 1.00 mol), 3k (293 mg, 0.961 mmol, 96%); colorless oil;
DAICEL CHIRALCEL OD-H, hexane/ipa = 97:3, 1 mL/min, 27 °C,
tR = 9.7 min for R and 17.5 min for S, 99% ee; [α]24D = +16.8 (c 1.01,
CHCl3); IR (KBr) ν 1731, 1250, 1155, 1029, 779, 700 cm−1; 1H NMR
δ 1.11 (t, J = 7.2 Hz, 3H), 3.15−3.25 (m, 2H), 4.05 (q, J = 7.1 Hz,
2H), 5.38 (t, J = 7.9 Hz, 1H), 7.13−7.30 (m, 5H), 7.39−7.50 (m, 4H),
7.74 (d, J = 7.2 Hz, 1H), 7.83 (d, J = 9.6 Hz, 1H), 8.14 (d, J = 9.6 Hz,
1H) ppm; 13C NMR δ 14.3, 41.5, 42.7, 60.5, 123.5, 123.9, 125.0, 125.3,
125.9, 126.3, 127.2, 127.6, 128.3, 128.6, 131.3, 133.8, 138.6, 143.1,
171.5 ppm; HRMS-FAB (m/z, M = C21H20O2) 327.1365 [M + Na]+,
calcd 327.1361.
ASSOCIATED CONTENT
■
S
* Supporting Information
1H and 13C NMR spectra and HPLC charts of the products.
This material is available free of charge via the Internet at
http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: hnishi@apchem.nagoya-u.ac.jp.
Notes
The authors declare no competing financial interest.
(S)-Ethyl 3-(Naphthalen-2-yl)-3-phenylpropanoate (3l). 2l
(303 mg, 1.00 mmol), the product (294 mg, 0.966 mmol, 96%);
white solid; mp 75 °C; DAICEL CHIRALCEL OD-H, hexane/ipa =
97:3, 1 mL/min, 27 °C, tR = 8.2 min for R and 11.2 min for S, 95% ee;
ACKNOWLEDGMENTS
■
This research was partly supported by the Japan Society for the
Promotion of Science (No. 22245014).
[α]25 = +38.8 (c 1.01, CHCl3); IR (KBr) ν 1723, 1373, 1267, 1151,
D
10918
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Article
REFERENCES
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