Efficient palladium-catalyzed coupling of Baylis-Hillman acetates with an allylstannane

Article abstract of DOI:10.1055/s-0029-1218612

Acetates of Baylis-Hillman adducts derived from ethyl acrylate, methyl vinyl ketone, and acrylonitrile were coupled with allyltributylstannane using Pd(PPhor Pd(dba)as the catalyst at room temperature to afford the corresponding trisubstituted alka-1,5-di

Full text of DOI:10.1055/s-0029-1218612

PAPER
661
Efficient Palladium-Catalyzed Coupling of Baylis–Hillman Acetates with an
Allylstannane
Coupling
iof Bayl
n
is–Hillman
A
h
cetates
w
ith
y
an
A
llylstan
u
nane ng Park,a Young Bum Kwon,a Kyungmo Yang,a Hakjune Rhee,b Cheol Min Yoon*a
a
Department of Advanced Material Chemistry, Korea University, Jochiwon, Choongnam 339-700, South Korea
Fax +81(41)8675396; E-mail: cmyoon@korea.ac.kr
b
Department of Chemistry & Applied Chemistry, Hanyang University, Sangrok-Gu, Ansan, Kyunggi-Do 426-791, South Korea
Received 23 July 2009; revised 21 October 2009
corresponding trisubstituted alkenes 2 bearing terminal
C=C bonds in good to high yields (Scheme 1).
Abstract: Acetates of Baylis–Hillman adducts derived from ethyl
acrylate, methyl vinyl ketone, and acrylonitrile were coupled with
allyltributylstannane using Pd(PPh3)4 or Pd(dba)2 as the catalyst at
room temperature to afford the corresponding trisubstituted alka-
1,5-dienes in good to high yields.
E
OAc
Ar
A) Pd(PPh3)4
E
SnBu3
Ar
Key words: Baylis–Hillman acetates, allyltributylstannane, bis-p-
allylpalladium, 1,5-diene, allylation
B) Pd(dba)2, Ph3P
1
E = COOEt, COMe, CN
2
Scheme 1
The Baylis–Hillman reaction is an important carbon–car-
bon bond-forming reaction affording highly functional-
ized alkenes.1 Baylis–Hillman adducts and their acetates
are valuable synthetic intermediates for the synthesis of a
variety of heterocycles.2 They are also used as intermedi-
ates for the preparation of trisubstituted alkenes bearing
various functional groups by nucleophilic substitution3 or
a cross-coupling reaction with organometallics4–6 using
palladium and rhodium as a catalyst or alkyl halides using
zinc7 and trialkylindium.8 Organic compounds containing
a terminal C=C bond moiety are important for the con-
struction of target molecules, such as by metathesis. The
allylation of Baylis–Hillman adducts and their acetates is
one of the most important reactions for the preparation of
the 1,5-diene system. Two methods for the allylation of
Baylis–Hillman adducts or their acetates have been devel-
oped.9 One is the zinc-mediated allylation of Baylis–
Hillman acetates with excess allyl bromide and zinc and
the other is the boron trifluoride–diethyl ether mediated allyl-
ation of Baylis–Hillman adducts at 0 °C. However, these
two methods have their own disadvantages; limited scope
and anhydrous conditions. Recently, palladium-catalyzed
cross-coupling reactions have become one of the most
powerful and reliable methods for C–C bond formation.10
Among these, the Stille reaction has widely been applied
in organic synthesis because of the availability and stabil-
ity of organostannanes and their ample compatibility with
most organic functional groups.11 As a result of studies on
palladium-catalyzed reactions of Baylis–Hillman adducts
and their acetates, we report the cross-coupling reaction of
Baylis–Hillman acetates 1 with allyltributylstannane us-
ing tetrakis(triphenylphosphine)palladium(0) [Pd(PPh3)4]
or bis(dibenzylideneacetone)palladium(0) [Pd(dba)2] as
the catalyst at room temperature under argon to give the
The cross-coupling reaction of Baylis–Hillman acetate 1a
with allyltributylstannane using the Pd(dba)2/Ph3P/LiCl
system in N,N-dimethylformamide–water12 gave the cou-
pling product 2a after 19 hours at 80 °C in 87% isolated
yield. Based on this result, systematic studies were con-
ducted to optimize the conditions for the reaction of ace-
tate 1a with allyltributylstannane by changing
temperature, palladium catalyst, and solvent (CH2Cl2,
H2O, DMF, THF, MeOH). We found that the optimum
system is Pd(PPh3)4 in N,N-dimethylformamide at room
temperature under an argon atmosphere. The acetate 1a
reacted with allyltributylstannane in the presence of
Pd(PPh3)4 (5 mol%) in N,N-dimethylformamide at room
temperature under argon to provide the cross-coupled alk-
ene 2a as a mixture of E- and Z-isomers (80:20), thus fa-
voring the E-isomer, in 92% isolated yield (Table 1, entry
1). The stereochemistry of the products 2a was estab-
lished by comparing 1H NMR parameters for the olefinic
and methylene protons with literature values.13 Due to dif-
ficulties in separating the two isomers of 2a by column
chromatography on silica gel, the ratio of E- and Z-iso-
mers was determined on the basis of the integration of iso-
meric olefinic protons and allylic methylene protons in the
1H NMR spectrum of the product. Encouraged by this re-
sult, the coupling reactions of various Baylis–Hillman
acetates containing ester 1b–g, ketone 1h–j, and nitrile
groups 1k–m with allyltributylstannane were attempted to
determine the scope and the limitations under these reac-
tion conditions (Table 1, Method A). The reaction of ace-
tates of Baylis–Hillman adducts 1b–f derived from ethyl
acrylate with allyltributylstannane under our conditions
gave the corresponding alkenes 2b–f as a mixture of E-
and Z-isomers favoring the E-isomer in high yields
(Table 1, entries 2–6). Baylis–Hillman acetates derived
from acrylonitrile 1k–m reacted with allyltributylstan-
nane to give the corresponding alkenes 2k–m as a mixture
of E- and Z-isomers favoring the Z-isomer in high yields.
SYNTHESIS 2010, No. 4, pp 0661–0665
x
x
.
x
x
.2
0
1
0
Advanced online publication: 16.12.2009
DOI: 10.1055/s-0029-1218612; Art ID: F09309SS
© Georg Thieme Verlag Stuttgart · New York

662
J. Park et al.
PAPER
O
OAc O
O
SnBu3
OEt
OEt
PhSnBu3
OEt
Pd(dba)2
60 °C
Pd(dba)2
r.t.
Ph
1a
4 86%
3 83%
Scheme 2
However, the reaction of Baylis–Hillman acetate 1g hav- 1,5-dienes 2h–j as a mixture of E- and Z-isomers favoring
ing a nitro group on the phenyl ring with allyltributylstan- the E-isomer in high yields.
nane under these condition gave a complicated mixture
according to TLC. After studies, the system using
Pd(dba)2 and triphenylphosphine in N,N-dimethylform-
Our catalytic systems were expanded to the coupling of
acetate 1a with tributyl(vinyl)stannane and tributyl(phe-
nyl)stannane. The reaction of Baylis–Hillman acetate 1a
amide–water was found to be the second optimum condi-
with tributyl(vinyl)stannane and tributyl(phenyl)stannane
tions. The acetate 1g reacted with allyltributylstannane
using a protocol of Pd(dba)2 (5 mol%) and triphenylphos-
phine (10 mol%) in N,N-dimethylformamide–water
using Pd(dba)2 (5 mol%) and triphenylphosphine (10
mol%) at room temperature under argon to afford the cou-
(99.5:0.5) at room temperature or 60 °C, respectively, un-
pling product 2g in 69% yield (Table 1, Method B). The
der argon (Method B) gave the corresponding coupling
acetates of Baylis–Hillman adducts 1h–j, derived from
products 3 and 4 (E-isomer only) in 83% and 86% yields,
methyl vinyl ketone (Table 1, entries 8–10), underwent
respectively (Scheme 2).
the coupling reaction with allyltributylstannane under the
second optimized conditions to give the corresponding
Table 1 Palladium-Catalyzed Allylation of Baylis–Hillman Acetates with Allyltributylstannane
Entry
Substrate 1
Producta 2
Methodb Time (h) Yieldc (%) Ratiod E/Z
CO2Et
CO2Et
CO2Et
OAc
CO2Et
1
1a
2a
A
A
0.5
0.5
92
86
80:20
86:14
OAc
OAc
O
2
3
1b
2b
2c
CO2Et
CO2Et
O
1c
A
0.5
91
83:17
CO2Et
OAc
CO2Et
4
5
6
1d
2d
2e
2f
A
A
A
0.5
0.5
2
91
94
85
88:12
87:13
84:16
CO2Et
OAc
CO2Et
1e
MeO
MeO
CO2Et
OAc
CO2Et
1f
Br
Br
OAc
CO2Et
CO2Et
7
1g
2g
B
3
69
80:20
NO2
NO2
Synthesis 2010, No. 4, 661–665 © Thieme Stuttgart · New York

PAPER
Coupling of Baylis–Hillman Acetates with an Allylstannane
663
Table 1 Palladium-Catalyzed Allylation of Baylis–Hillman Acetates with Allyltributylstannane (continued)
Entry
8
Substrate 1
Producta 2
Methodb Time (h) Yieldc (%) Ratiod E/Z
COMe
COMe
OAc
OAc
COMe
COMe
1h
2h
B
1.5
83
82:18
9
1i
2i
B
B
2
2
82
75
55:45
80:20
NO2
NO2
COMe
OAc
COMe
10
1j
2j
Br
Br
OAc
CN
11
12
13
1k
1l
2k
2l
A
A
A
3
2
1
68
66
89
37:63
24:86
5:95
CN
OAc
CN
CN
OAc
CN
1m
2m
CN
MeO
MeO
a All products were characterized by 1H NMR and IR spectroscopy.
b Method A: allyltributylstannane, Pd(PPh3)4 (5 mol%), DMF, r.t.; B: allyltributylstannane, Pd(dba)2 (5 mol%), Ph3P (10 mol%), DMF, r.t.
c Isolated yield.
d Ratio determined by 1H NMR spectroscopy.
The reaction of Baylis–Hillman acetates with allyltribu-
tylstannane seems to proceed as follows (Scheme 3). The
EWG
R
OAc
oxidative addition reaction of Baylis–Hillman acetate to
Pd(0) forms the p-allylpalladium complex 514 which is
EWG
Pd(0)
R
transmetalated with allyltributylstannane to produce bis-
p-allylpalladium complex 6.15,16 The bis-s-allylpalladium
complex 7 generated from 6 in the presence of the phos-
phine ligand is reductively eliminated to give the corre-
sponding coupled products 2 and Pd(0) species.
2
1
EWG
EWG
R
L
L
R
In conclusion, we have described efficient protocols for
the cross coupling of Baylis–Hillman acetates with allyl-
tributylstannane to give the corresponding 1,5-dienes as a
mixture of E- and Z-isomers in good to high yields. The
E-isomers are the major product for Baylis–Hillman ace-
tates derived from ethyl acrylate and methyl vinyl ketone,
and the Z-isomers are the major product for Baylis–
Hillman acetates derived from acrylonitrile. Our methods
offer several advantages, such as mild reaction conditions,
readily available reagents, and broad scope.
Pd
5
7
PdOAc
EWG
R
SnBu3
Pd
6
Scheme 3
IR spectra of samples were recorded on a Perkin-Elmer FT-IR 240-c
spectrometer using KBr disks. 1H NMR (300 MHz) and 13C NMR
(75 MHz) spectra were recorded on a Bruker 300 spectrometer in
CDCl3 using tetramethylsilane as an internal standard. High-resolu-
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664
J. Park et al.
PAPER
tion ESI-MS spectra were obtained on an IT-TOF (Shimadzu, Ja-
pan) at Korea Basic Science Institute. Column chromatography was
performed using Merck silica gel (230–400 mesh). All chemicals
were purchased from Sigma-Aldrich and used without further puri-
fication. All known compounds (2b, 2d, 2l and 2m) have physical,
spectroscopic, and analytic data identical to that given in the litera-
ture;9a for all new compounds, adequate characterization is given.
All products were obtained as oils unless otherwise stated.
13C NMR (75 MHz, CDCl3): d = 168.48, 139.48, 138.18, 135.74,
132.84, 130.23, 130.09, 129.39, 128.53, 126.45, 115.01, 60.89,
33.44, 27.10, 21.60, 14.52.
HRMS (ESI): m/z [M + H]+ calcd for C16H21O2: 245.1536; found:
245.1536.
Ethyl 2-(4-Methoxybenzylidene)hex-5-enoate (2e)
IR (neat): 3077, 2977, 2838, 1700, 1604, 1511, 1446, 1303, 1249,
1176, 1126, 1029, 914, 829 cm–1.
1H NMR (300 MHz, CDCl3): d (E-isomer) = 1.32–1.37 (t, J = 7.2
Hz, 3 H), 2.30–2.35 (m, 2 H), 2.63–2.68 (m, 2 H), 3.84 (s, 3 H),
4.23–4.30 (q, J = 7.2 Hz, 2 H), 4.98–5.10 (m, 2 H), 5.87 (m, 1 H),
6.93 (d, J = 9 Hz, 2 H), 7.34 (d, J = 9 Hz, 2 H), 7.63 (s, 1 H).
13C NMR (75 MHz, CDCl3): d = 168.66, 159.88, 138.94, 131.19,
130.82, 129.07, 128.23, 114.96, 113.96, 60.79, 55.48, 33.22, 26.98,
14.53.
Ethyl 2-Benzylidenehex-5-enoate (2a); Typical Procedure for
Method A
A soln of Baylis–Hillman acetate 1a (99.3 mg, 0.4 mmol), allyl-
tributylstannane (132.4 mg, 0.4 mmol) and Pd(PPh3)4 (23.1 mg, 5
mol%) in DMF (3 mL) was stirred at r.t. under argon for 0.5 h. After
complete conversion (TLC), the mixture was quenched with dis-
tilled H2O (30 mL) and extracted with Et2O (2 × 30 mL). The com-
bined organic layers were washed with brine (20 mL), dried
(MgSO4), and evaporated under reduced pressure. The residue was
stirred with KF (2 equiv) in MeOH (3 mL) for 12 h, then concen-
trated and purified by column chromatography (silica gel, hexane–
EtOAc, 10:1) to give 2a (84.8 mg, 92%) as an oil.
HRMS (ESI): m/z [M + H]+ calcd for C16H21O3: 261.1485; found:
261.1484.
Ethyl 2-(4-Bromobenzylidene)hex-5-enoate (2f)
IR (neat): 3077, 2977, 2931, 2854, 1700, 1639, 1585, 1484, 1446,
1369, 1303, 1245, 1195, 1130, 1095, 1072 cm–1.
IR (neat): 3074, 2954, 2854, 1708, 1639, 1492, 1446, 1369, 1245,
1199, 1130, 1072, 1022 cm–1.
1H NMR (300 MHz, CDCl3): d (E-isomer) = 1.32–1.38 (t, J = 7.2
Hz, 3 H), 2.28–2.35 (m, 2 H), 2.62–2.67 (m, 2 H) 4.23–4.32 (q,
J = 7.2 Hz, 2 H), 4.96–5.09 (m, 2 H), 5.79–5.91 (m, 1 H), 7.34 (m,
5 H), 7.68 (s, 1 H).
1H NMR (300 MHz, CDCl3): d (E-isomer) = 1.32–1.37 (t, J = 7.2
Hz, 3 H), 2.25–2.32 (m, 2 H), 2.57–2.62 (m, 2 H), 4.23–4.31 (q,
J = 7.2 Hz, 2 H), 4.96–5.09 (m, 2 H), 5.76–5.89 (m, 1 H), 7.23 (d,
J = 8.1 Hz, 2 H), 7.49 (d, J = 8.4 Hz, 2 H), 7.59 (s 1 H).
13C NMR (75 MHz, CDCl3): d = 168.39, 139.29, 139.15, 135.78,
13C NMR (75 MHz, CDCl3): d = 168.18, 138.01, 134.70, 133.81,
133.03, 129.31, 128.57, 128.44, 115.03, 60.88, 33.33, 26.98, 14.49.
131.86, 131.33, 130.82, 122.66, 115.27, 61.08, 33.23, 26.99, 14.51.
HRMS (ESI): m/z [M + H]+ calcd for C15H19O2: 231.1380; found:
231.1381.
HRMS (ESI): m/z [M + H]+ calcd for C15H18BrO2: 309.0485; found:
309.0484.
Ethyl 2-(3-Nitrobenzylidene)hex-5-enoate (2g); Typical Proce-
dure for Method B
3-Benzylidenehept-6-en-2-one (2h)
IR (neat): 3065, 3025, 2914, 2843, 2206, 1730, 1637, 1485, 1436,
1214, 1071, 991, 916 cm–1.
A soln of Baylis–Hillman acetate 1g (117.3 mg, 0.4 mmol), allyl-
tributylstannane (132.4 mg, 0.4 mmol), Pd(dba)2 (11.5 mg, 5
mol%), and Ph3P (10.5 mg, 10 mol%) in DMF (3 mL) was stirred at
r.t. under argon for 3 h. After complete conversion (TLC), the mix-
ture was quenched with distilled H2O (30 mL) and extracted with
Et2O (2 × 30 mL). The combined organic layers were washed with
brine (20 mL), dried (MgSO4), and evaporated under reduced pres-
sure. The residue was stirred with KF (2 equiv) in MeOH (3 mL) for
12 h, then concentrated and purified by column chromatography
(silica gel, hexane–EtOAc, 10:1) to give 2g (76.3 mg, 69%) as an
oil.
1H NMR (300 MHz, CDCl3): d (E-isomer) = 1.34–1.39 (t, J = 6.9
Hz, 3 H), 2.34 (m, 2 H), 2.61 (m, 2 H), 4.27–4.34 (q, J = 7.2 Hz, 2
H), 4.99–5.11 (m, 2 H), 5.83 (m, 1 H), 7.57 (t, J = 8.1 Hz, 1 H), 7.65
(d, J = 7.8 Hz, 1 H), 7.68 (s, 1 H), 8.18 (d, J = 8.1 Hz, 1 H), 8.24 (s,
1 H).
1H NMR (300 MHz, CDCl3): d (E-isomer) = 2.20–2.28 (m, 2 H),
2.45 (s, 3 H), 2.59–2.64 (m, 2 H), 4.95–5.06 (m, 2 H), 5.78–5.87 (m,
1 H), 7.40 (m, 5 H), 7.50 (s, 1 H); d (Z-isomer) = 1.99 (s, 3 H), 2.27
(m, 2 H), 2.48 (m, 2 H), 4.99–5.09 (m, 2 H), 5.84 (m, 1 H), 6.71 (m,
1 H), 7.18–7.30 (m, 5 H).
3-(3-Nitrobenzylidene)hept-6-en-2-one (2i)
IR (neat): 3077, 2919, 2850, 1689, 1639, 1527, 1434, 1349, 1199,
1099, 998, 914, 809 cm–1.
1H NMR (300 MHz, CDCl3): d (E-isomer) = 2.19–2.26 (m, 2 H),
2.47 (s, 3 H), 2.55–2.60 (m, 2 H), 4.97–5.08 (m, 2 H), 5.80 (m, 1 H),
7.47 (s, 1 H), 7.57–7.70 (m, 1 H), 8.19–8.22 (d, J = 8.1 Hz, 1 H),
8.26 (s, 1 H); d (Z-isomer) = 2.07 (s, 3 H), 2.25–2.32 (m, 2 H), 2.49–
2.54 (m, 2 H), 5.03–5.12 (m, 2 H), 5.76–5.89 (m, 1 H), 6.63 (s, 1 H),
7.46–7.50 (m, 2 H), 8.08–8.15 (m, 3 H).
13C NMR (75 MHz, CDCl3): d = 199.65, 144.50, 137.98, 136.87,
135.07, 129.84, 124.15, 123.14, 115.70, 33.14, 29.82, 26.80.
HRMS (ESI): m/z [M + Na]+ calcd for C14H15NNaO3: 268.0944;
found: 278.0944.
13C NMR (75 MHz, CDCl3): d = 167.62, 148.55, 137.47, 136.29,
134.92, 130.63, 129.63, 129.10, 124.06, 122.93, 115.81, 61.31,
34.87, 27.22, 14.49.
HRMS (ESI): m/z [M + H]+ calcd for C15H18NO4: 276.1230; found:
276.1229.
3-(4-Bromobenzylidene)hept-6-en-2-one (2j)
Ethyl 2-(3-Methylbenzylidene)hex-5-enoate (2c)
IR (neat): 3074, 2977, 2873, 1700, 1635, 1604, 1446, 1373, 1261,
1230, 1199, 1126, 1095, 1025 cm–1.
1H NMR (300 MHz, CDCl3): d (E-isomer) = 1.33–1.38 (t, J = 6.9
Hz, 3 H), 2.29–2.35 (m, 2 H), 2.37 (s, 3 H), 2.61–2.67 (m, 2 H),
4.24–4.32 (q, J = 7.2 Hz, 2 H), 4.98–5.10 (m, 2 H), 5.80–5.94 (m, 1
H), 7.13–7.29 (m, 4 H), 7.67 (s, 1 H).
IR (neat): 3074, 2919, 2850, 1666, 1585, 1488, 1434, 1384, 1349,
1307, 1276, 1245, 1211, 1126, 1072, 1006, 910, 821 cm–1.
1H NMR (300 MHz, CDCl3): d (E-isomer) = 2.15–2.22 (m, 2 H),
2.43 (s, 3 H), 2.54–2.60 (m, 2 H), 4.95–5.05 (m, 2 H), 5.80 (m, 1 H),
7.24–7.27 (d, J = 8.1 Hz, 2 H), 7.41 (s, 1 H), 7.53–7.56 (d, J = 8.7
Hz, 2 H); d (Z-isomer) = 2.02 (s, 3 H), 2.24–2.29 (m, 2 H), 2.43–
2.48 (m, 2 H), 5.00–5.09 (m, 2 H), 5.80 (m, 1 H), 6.58 (s, 1 H), 7.04–
7.07 (d, J = 8.7 Hz, 2 H), 7.43–7.46 (d, J = 8.4 Hz, 2 H).
Synthesis 2010, No. 4, 661–665 © Thieme Stuttgart · New York

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Coupling of Baylis–Hillman Acetates with an Allylstannane
665
13C NMR (75 MHz, CDCl3): d = 199.98, 142.78, 138.72, 137.78,
2001, 42, 8341. (f) Drewes, S. E.; Emslie, N. D. J. Chem.
134.60, 131.91, 130.82, 122.97, 115.15, 33.03, 26.20, 25.77.
Soc., Perkin Trans. 1 1982, 2079. (g) Hoffmann, H. M. R.;
Rabe, J. Helv. Chim. Acta 1984, 67, 413. (h) Hoffmann, H.
M. R.; Rabe, J. J. Org. Chem. 1985, 50, 3849.
(i) Hoffmann, H. M. R.; Rabe, J. Angew. Chem., Int. Ed.
Engl. 1985, 24, 94. (j) Buchholz, R.; Hoffmann, H. M. R.
Helv. Chim. Acta 1991, 74, 1213. (k) Ameer, F.; Drewes, S.
E.; Hoole, R. F. A.; Kaye, P. T.; Pitchford, A. T. J. Chem.
Soc., Perkin Trans. 1 1985, 2713.
HRMS (ESI): m/z [M + H]+ calcd for C14H16BrO: 279.0379; found:
279.0379.
2-Benzylidenehex-5-enenitrile (2k)
IR (neat): 3440, 3077, 2923, 2850, 2210, 1731, 1643, 1496, 1446,
1299, 1214, 1072, 995, 917 cm–1.
1H NMR (300 MHz, CDCl3): d (Z-isomer) = 2.39–2.45 (m, 2 H),
2.49–2.52 (m, 2 H), 5.05–5.16 (m, 2 H), 5.80 (m, 1 H), 6.94 (s, 1 H),
7.38–7.45 (m, 3 H), 7.70–7.73 (m, 2 H).
(3) (a) Basavaiah, D.; Dharma Rao, P.; Suguna, H. R.
Tetrahedron 1996, 52, 8001. (b) Basavaiah, D.;
Jaganmohan Rao, A.; Satyanarayana, T. Chem. Rev. 2003,
103, 811. (c) O’Dell, D. K.; Nicholas, K. M. J. Org. Chem.
2003, 68, 6427.
Ethyl 2-Benzylidenepent-4-enoate (3)
IR (neat): 3081, 2981, 2923, 2854, 1708, 1635, 1446, 1369, 1265,
(4) Kabalka, G. W.; Venkataiah, B.; Dong, G. Org. Lett. 2003,
5, 3803.
1218, 1199, 1126, 1099, 1068, 1022, 914 cm–1.
1H NMR (300 MHz, CDCl3): d (E-isomer) = 1.24–1.29 (t, J = 7.2
Hz, 3 H), 3.30 (d, J = 5.4 Hz, 2 H), 4.24–4.31 (q, J = 7.2 Hz, 2 H),
5.08–5.14 (m, 2 H), 6.01 (m, 1 H), 7.33–7.40 (m, 5 H), 7.80 (s, 1 H).
13C NMR (75 MHz, CDCl3): d = 168.06, 140.19, 135.69, 135.52,
130.52, 129.27, 128.57, 128.43, 115.67, 60.88, 31.65, 14.29.
HRMS (ESI): m/z [M + Na]+ calcd for C14H16NaO2: 239.1043;
found: 239.1044.
(5) (a) Navarre, L.; Darses, S.; Genet, J.-P. Chem. Commun.
2004, 1108. (b) Navarre, L.; Darses, S.; Genet, J.-P. Adv.
Synth. Catal. 2006, 348, 317.
(6) Kabalka, G. W.; Dong, G.; Venkataiah, B.; Chen, C. J. Org.
Chem. 2005, 70, 9207.
(7) Das, B.; Banerjee, J.; Mahender, G.; Majhi, A. Org. Lett.
2004, 6, 3349.
(8) Ranu, B. C.; Chattopadhyay, K.; Jana, R. Tetrahedron Lett.
2007, 48, 3847.
(9) (a) Yadav, J. S.; Subba Reddy, B. V.; Mandal, S. S.; Singh,
A. P.; Basak, A. K. Synthesis 2008, 1943. (b) Srihari, P.;
Singh, A. P.; Basak, A. K.; Yadav, J. S. Tetrahedron Lett.
2007, 48, 5999.
(10) (a) Metal-Catalyzed Cross-Coupling Reactions; Diedrich,
F.; Stang, P. J., Eds.; Wiley-VCH: Weinheim, 1998.
(b) Hassan, J.; Sevignon, M.; Gozzi, C.; Schulz, E.; Lemaire,
M. Chem. Rev. 2002, 102, 1359.
Ethyl 2-Benzylidene-3-phenylpropanoate (4)
IR (neat): 3081, 3062, 3027, 2981, 2931, 1708, 1631, 1600, 1492,
1450, 1365, 1257, 1199, 1091, 1025, 933, 860 cm–1.
1H NMR (300 MHz, CDCl3): d (E-isomer) = 1.32–1.37 (t, J = 3.6
Hz, 3 H), 3.96 (s, 2 H), 4.17–4.24 (q, J = 7.5 Hz, 2 H), 7.20–7.38
(m, 10 H), 7.94 (s, 1 H).
13C NMR (75 MHz, CDCl3): d = 168.28, 140.85, 140.58, 139.69,
135.58, 131.27, 129.30, 128.79, 128.69, 128.16, 126.18, 61.02,
33.30, 14.38.
(11) (a) Stille, J. K. Angew. Chem., Int. Ed. Engl. 1986, 25, 508.
(b) Mitchell, T. N. Synthesis 1992, 803. (c) Ritter, K.
Synthesis 1993, 735.
HRMS (ESI): m/z [M + Na]+ calcd for C18H18NaO2: 289.1199;
(12) Mendez, M.; Cuerva, J. M.; Gomez-Bengoa, E.; Cardenas,
D. J.; Echavarren, A. M. Chem. Eur. J. 2002, 8, 3620.
(13) (a) Basavaiah, D.; Sarma, P. K. S.; Bhavani, A. K. D.
J. Chem. Soc., Chem. Commun. 1994, 1091. (b) Basavaiah,
D.; Pandiaraju, S.; Padmaja, K. Synlett 1996, 393.
(c) Basavaiah, D.; Krishnamacharyulu, M.; Suguna, H. R.;
Pandiaraju, S. Tetrahedron Lett. 1997, 38, 2141.
(d) Shanmugam, P.; Singh, P. R. Synlett 2001, 1314.
(14) (a) Mandai, T.; Matsumoto, T.; Tsuji, J. Tetrahedron Lett.
1993, 34, 2513. (b) Al-Masum, M.; Meguro, M.;
Yamamoto, Y. Tetrahedron Lett. 1997, 38, 6071.
(15) (a) Nakamura, H.; Iwama, H.; Yamamoto, Y. Chem.
Commun. 1996, 1459. (b) Nakamura, H.; Iwama, H.;
Yamamoto, Y. J. Am. Chem. Soc. 1996, 118, 6641; and
references cited therein.
found: 289.1199.
Acknowledgment
This work was financially supported by Korea University Grant.
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Synthesis 2010, No. 4, 661–665 © Thieme Stuttgart · New York