Regio- and stereocontrolled reaction of arenes with ethyl propiolate catalyzed by palladium or platinum complexes with a bidentate phosphine ligand. an efficient and straightforward synthesis of (1z,3e)-1-aryl-1,3-butadienes

Article abstract of DOI:10.1246/bcsj.20120233

The reaction of mesitylene with ethyl propiolate in the presence of [Pd(dppe)(OAc)2] in TFA at 30 °C for 5 h gave diethyl (2E,4Z)-4-[(2,4,6- trimethylphenyl)methylene]-2-pentenedioate selectively. Screening several bidentate phosphines ligands showed that dppe and dppm ligands are good for the arylbutadiene formation. This reaction was applied to other electron-rich arenes and found to be effective for synthesis of arylbutadienes and extended -conjugated molecules. The regio- and stereoselective addition of an arene to propiolate was confirmed by NMR and single-crystal X-ray structural analyses of the products, suggesting that the arylbutadiene formation consisted of anti addition of an arene and a metal to the triple bond of ethyl propiolate, followed by syn addition to another molecule of ethyl propiolate. Similarly, the reaction of various arenes with ethyl propiolate in the presence of [Pt(dppe)(OTf )2] catalyst gave arylbutadienes selectively. In the Pd- or Pt-catalyzed reaction of arenes with ethyl propiolate, it was found that a bidentate ligand controlled the reaction to lead the formation of arylbutadienes.

Full text of DOI:10.1246/bcsj.20120233

© 2013 The Chemical Society of Japan
Bull. Chem. Soc. Jpn. Vol. 86, No. 1, 129-137 (2013)
129
Regio- and Stereocontrolled Reaction of Arenes with Ethyl Propiolate
Catalyzed by Palladium or Platinum Complexes with a Bidentate
Phosphine Ligand. An Efficient and Straightforward Synthesis
of (1Z,3E)-1-Aryl-1,3-butadienes
Juzo Oyamada, Mariko Sakai, Yasunori Yamada, and Tsugio Kitamura*
Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering,
Saga University, Honjo-machi, Saga 840-8502
Received August 27, 2012; E-mail: kitamura@cc.saga-u.ac.jp
The reaction of mesitylene with ethyl propiolate in the presence of [Pd(dppe)(OAc)2] in TFA at 30 °C for 5 h gave
diethyl (2E,4Z)-4-[(2,4,6-trimethylphenyl)methylene]-2-pentenedioate selectively. Screening several bidentate phos-
phines ligands showed that dppe and dppm ligands are good for the arylbutadiene formation. This reaction was applied to
other electron-rich arenes and found to be effective for synthesis of arylbutadienes and extended ³-conjugated molecules.
The regio- and stereoselective addition of an arene to propiolate was confirmed by NMR and single-crystal X-ray
structural analyses of the products, suggesting that the arylbutadiene formation consisted of anti addition of an arene and a
metal to the triple bond of ethyl propiolate, followed by syn addition to another molecule of ethyl propiolate. Similarly,
the reaction of various arenes with ethyl propiolate in the presence of [Pt(dppe)(OTf)2] catalyst gave arylbutadienes
selectively. In the Pd- or Pt-catalyzed reaction of arenes with ethyl propiolate, it was found that a bidentate ligand
controlled the reaction to lead the formation of arylbutadienes.
Generally C-H bonds are low in reactivity because of their
Ar H +
E
nonpolar and strong nature. Introduction of functional groups
into such C-H bonds requires prefunctionalization and there-
fore results in increasing reaction processes. However, if
direct functionalization of the C-H bonds can be conveniently
utilized for many synthetic processes, it will be a more efficient
process without prefunctionalization and reduce the reaction
steps and chemicals. From the viewpoint of green chemistry,
such direct functionalization of the C-H bonds attracts much
attention to many chemists and has been studied extensively.1
Hydroarylation of alkynes can formally be regarded as a
reaction in which both aryl and hydrogen moieties of an
aromatic compound add across a triple bond.2 Therefore,
hydroarylation of alkynes is one of the most effective methods
for direct C-H bond functionalization that provides a conven-
ient, clean, atom-economic and environmentally benign meth-
odology to aryl-substituted alkenes without requiring prefunc-
tionalization of arenes such as halogenation. We have found
that the hydroarylation of propiolic acids or propiolates in
trifluoroacetic acid (TFA) as solvent proceeds efficiently in the
presence of Pd(OAc)2, PtCl2/AgOTf, or K2[PtCl4]/AgOTf as a
catalyst to give cis-cinnamic acids or cinnamates regio- and
stereoselectively.3 As shown in Scheme 1, in the hydroaryla-
tion reaction, the cationic metal activates the alkyne to give an
arylvinyl metal complex via electrophilic aromatic substitu-
tion.4 The vinyl metal complex undergoes protonation to afford
a cis-arylalkene as a major product. In the Pd(OAc)2-catalyzed
hydroarylation reaction, the vinyl palladium complex can add
another alkyne to produce an arylbutadiene but this is a minor
process.
[M]+
[M]
E
E
Ar
Ar
E
E
[M]
H+
H+
H
E
Ar
Ar
E
major
E
minor
H
Scheme 1. Hydroarylation reaction of alkynes.
The formation of the arylbutadiene results in low selectivity
of hydroarylation and decreases the yield of hydroaryla-
tion products. However, we disclosed that the hydroarylation
using a palladium complex with a bidentate phosphine ligand,
[Pd(dppe)(OAc)2] (dppe: 1,2-bis(diphenylphosphino)ethane),
yielded the arylbutadiene predominantly.5 Inspired by this
result, we have considered the presence of cis- and trans-forms
of the arylvinyl metal complex with an alkyne ligand, where
the trans-form is considered to be more stable than the cis-form
due to the steric hindrance according to the experimental
results,3 as shown in Scheme 2. A larger population of the
trans-form gives the arylalkene by protonation, whereas only
the cis-form can undergo the alkyne addition leading to the
arylbutadiene. We imagined that the presence of the bidentate
phosphine ligand controls the equilibrium between the cis- and
Published on the web December 15, 2012; doi:10.1246/bcsj.20120233

130
Bull. Chem. Soc. Jpn. Vol. 86, No. 1 (2013)
Regio- and Stereocontrolled Reaction of Arenes with Ethyl Propiolate
trans-forms and the desirable cis-form of the vinyl metal
complex is fixed by the bidentate ligand. Addition of the vinyl-
metal bond to the alkyne triple bond then takes place to give the
arylbutadiene selectively. As a result, double insertion of the
alkyne into the aryl-hydrogen bond is achieved.
To verify the ligand effect of bidentate phosphine com-
pounds on the arylbutadiene formation, we examined in detail
the reaction of ethyl propiolate with arenes in the presence of
Pd or Pt complexes bearing a bidentate phosphine ligand. We
herein report our findings concerning the direct formation of
arylbutadienes from arenes and ethyl propiolate controlled by
Pd or Pt complexes with bidentate phosphines.
because we observed that TFA was effective for the hydro-
arylation reaction of 2 with arenes.3 The results are summarized
in Table 1. When the reaction of 1a (1 mmol) and 2 (2 mmol)
was conducted in the presence of [Pd(dppe)(OAc)2] (0.005
mmol) in TFA (1 mL) at 30 °C for 5 h, the desired arylbutadiene
3a was formed in 68% yield, together with hydroarylation
product 4a (14%) and bis-hydroarylation product 5a (4%)
(Entry 1). As the amount of 1a was increased to 2 and 3
mmoles, the yield of 3a increased to 83% (Entries 2 and 3).
However, increasing the amount of 2 did not improve the yield
of 3a (Entry 4). Use of an excess amount of 1a inhibited the
formation of 5a to give higher yields of 3a and 4a. The amount
of TFA in a mixed solvent of TFA and CH2Cl2 also affected the
selectivity of 3a (Entries 5-7). A small amount of TFA was
favorable for selective formation of 3a although the reaction
did not proceed in the absence of TFA. As a result, the best
result was obtained when 0.25 mL of TFA was used together
with 0.75 mL of CH2Cl2 (Entry 6). The reactions at 0 and 50 °C
gave similar results (Entries 8-10).
Results and Discussion
Effect of Bidentate Phosphine Ligands on Pd-Catalyzed
Reaction. First, we studied the reaction of mesitylene (1a)
with ethyl propiolate (2) in the presence of [Pd(dppe)(OAc)2]
as a catalyst. TFA was used as a solvent for this reaction
Next, we examined the palladium complexes with different
ligands using the best reaction conditions described in Entry 6,
Table 1. The results are given in Table 2. Bis(diphenylphos-
phino)methane (dppm) showed a similar effect of the ligand
with a high selectivity of 3a although the yield was not high
(Entry 1). Increasing the ratio of TFA improved the yield of 3a
(Entries 2 and 3). Longer alkyl-chained ligands, 1,3-bis(di-
phenylphosphino)propane (dppp) and 1,4-bis(diphenylphos-
phino)butane (dppb), resulted in a low selectivity of 3a
(Entries 4 and 5). This result suggests that a ridged structure
of the palladium complex is suitable for the formation of
arylbutadiene 3a. 2,2¤-Bipyridine (bpy) interrupted the reaction
(Entry 6). A combined catalyst of [Pd(dppm)Cl2] and AgOAc
showed the same results as [Pd(dppm)(OAc)2] (Entries 7-9),
while [Pd(dppm)Cl2] itself reduced the reactivity (Entry 10).
The reactions with [Pd(dppe)Cl2]/AgOAc and [Pd(dppe)-
(OTf)2] catalysts did not improved the yield of 3a (Entries
11 and 12). Interestingly, Pd(OAc)2 itself did not show prod-
uct selectivity in this solvent system (Entry 13) and a mono-
E
L
[M]
L
[M]
Ar
Ar
E
L
E
L
E
trans-form: sterically favored
cis-form
If L,L = a bidentate ligand,
only cis-form exists.
H+
H
E
Ar
E
P
Pd
Ar
P
E
E
E
Ar
E
H
Scheme 2. Effect of bidentate ligand in the hydroarylation
reaction.
Table 1. Optimization of Reaction Conditionsa)
[Pd(dppe)(OAc)2]
CO2Et
+
CO2Et
+
+
CO2Et
3a
EtO2C
CO2Et
TFA, CH2Cl2
CO2Et
2
1a
4a
5a
Yield/%b)
1a
/mmol
2
TFA
/mL
CH2Cl2
/mL
Temp
/°C
Time
/h
Entry
/mmol
3a
4a
5a
1
2
3
4
5
6
7
8
9
1
2
3
1
2
2
2
2
2
2
2
2
2
3
2
2
2
2
2
2
1
1
1
1
0.5
0.25
0.1
1
1
0.25
0
0
0
0
0.5
0.75
0.9
0
0
0.75
30
30
30
30
30
30
30
0
5
5
5
5
5
5
5
5
68
83
83
37
83
91
55
86
83
91
14
17
17
0
16
9
4
0
0
2
0
0
2
0
0
0
2
14
17
5
50
0
2.5
5
10
a) Reaction conditions: [Pd(dppe)(OAc)2] (0.005 mmol), 1a, 2, and solvent. b) Yields were determined by GC and based on
the least amount of the substrate.

J. Oyamada et al.
Table 2. Effect of Ligandsa)
Bull. Chem. Soc. Jpn. Vol. 86, No. 1 (2013)
131
Yield/%
TFA
/mL
CH2Cl2
/mL
Entry
Catalyst
3a
4a
5a
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
[Pd(dppm)(OAc)2]
[Pd(dppm)(OAc)2]
[Pd(dppm)(OAc)2]
[Pd(dppp)(OAc)2]
[Pd(dppb)(OAc)2]
[Pd(bpy)(OAc)2]
[Pd(dppm)Cl2]/AgOAc
[Pd(dppm)Cl2]/AgOAc
[Pd(dppm)Cl2]/AgOAc
[Pd(dppm)Cl2]
[Pd(dppe)Cl2]/AgOAc
[Pd(dppe)(OTf)2]
Pd(OAc)2
[Pd(PPh3)2(OAc)2]
[Pd(dppe)2(OAc)2]
0.25
0.5
1
0.25
0.25
0.25
0.25
0.5
0.75
0.5
0
0.75
0.75
0.75
0.75
0.5
53
84
86
57
19
1
54
81
85
47
71
81
20
18
1
5
5
6
23
29
3
2
3
4
1
8
9
37
36
0
2
0
0
1
1
0
3
1
1
0
0
0
3
3
0
1
0
0.25
0.25
0.25
0.25
0.25
0.25
0.75
0.75
0.75
0.75
0.75
0.75
a) Reaction conditions: Pd catalyst (0.005 mmol), mesitylene (2 mmol), ethyl propiolate (2 mmol), TFA, and CH2Cl2 at
30 °C for 5 h.
of arylbutadine 3d. 2,4,6-Trimethylphenol (1e) and 2-bromo-
mesitylene (1f) also gave the corresponding arylbutadines 3e
and 3f in good yields although a larger amount of TFA was
required in the case of 1f because of lower reactivity of 1f
(Entries 5 and 6). Use of [Pd(dppm)(OAc)2] improved the
selectivity but the yield of 3f was similar (Entry 7). The same
result was observed in the case of naphthalene (1g) (Entries 8
and 9). In the case of 2-methoxynaphthalene (1h), [Pd(dppe)-
(OAc)2] gave 3h in good yield (Entry 10). In the case of
naphthalene (1g) and p-xylene (1d), a larger amount of TFA
was required to complete the reaction because of their low
reactivity. When a larger amount of TFA was used, [Pd(dppe)-
(OAc)2] showed low selectivity while [Pd(dppm)(OAc)2] did
good selectivity. These results indicate that [Pd(dppm)(OAc)2]
is an effective catalyst for less reactive arenes which require a
large amount of TFA. In the case of arenes with an electron-
withdrawing group, arylbutadienes were not formed since
hydroarylation reaction did not take place due to low reactivity.
Although the hydroarylation reaction of propiolic acid with
benzene or toluene occurred under catalytic conditions using a
K2[PtCl4]/AgOTf catalytic system,6b,6e the reactions of 2 with
tert-butylbenzene did not proceed under the conditions shown
in the Entries 3 and 4 of Table 3. This result indicates that the
reactivity of Pd falls with the coordination of dppe. In addition,
substituted propiolates such as ethyl phenylpropiolate were not
effective in the present reaction.
[Pd(dppe)(OAc)2]
(0.005 mmol)
CO2Et
+
MeSO3H (0.25 mL)
CH2Cl2 (0.75 mL)
30 °C, 5 h
1a
(2 mmol)
2
(2 mmol)
CO2Et
+
CO2Et
CO2Et
3a
4a
4%
83%
Scheme 3. Hydroarylation in the presence of methanesul-
fonic acid.
dentate phosphine ligand, PPh3, was not effective for the
formation of 3a (Entry 14). A palladium complex, [Pd(dppe)2-
(OAc)2], doubly coordinated with dppe inhibited the reaction
(Entry 15).
The presence of TFA is essential for this reaction. To verify
the effect of the acid, we examined the reaction in the presence
of other organic acids such as acetic acid, formic acid, and
methanesulfonic acid. Among the acids examined, methane-
sulfonic acid promoted the reaction (Scheme 3). When the
reaction of 1a with 2 was conducted in the presence of
[Pd(dppe)(OAc)2] in MeSO3H and CH2Cl2 at 30 °C for 5 h, 3a
and 4a were formed in 83 and 4% yields, respectively.
With the optimized reaction conditions in hand, we applied
this reaction to other arenes (Table 3). In all cases, the reac-
tions gave arylbutadienes 3 regio- and stereoselectively. In the
presence of [Pd(dppe)(OAc)2], pentamethylbenzene (1b) and
1,2,4,5-tetramethylbenzene (1c) gave the corresponding aryl-
butadienes 3 in good to high yields along with a small amount
of cinnamates 4 (Entries 1 and 2). In the case of p-xylene (1d)
(Entries 3 and 4), [Pd(dppm)Cl2]/AgOAc gave the better yield
Since this hydroarylation with a bidentate phosphine ligand
provides an arylbutadiene, this methodology can be applied to
an extended ³-conjugated molecule. The products 3a and 4a
obtained from the reaction of 1a with 2 also participated in this
reaction and afforded 3i and 3j in good yields, respectively
(Scheme 4). The reaction of 4a explains clearly that an excess
amount of 1a is required in the reaction of 1a with 2 to prevent
further reaction of 4a.
Regio- and Stereoselective Formation of Arylbutadienes.
The addition of arenes to propiolate 2 under the reaction con-
ditions proceeded regio- and stereoselectively. This fact is

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Bull. Chem. Soc. Jpn. Vol. 86, No. 1 (2013)
Regio- and Stereocontrolled Reaction of Arenes with Ethyl Propiolate
Table 3. The Reaction of 2 with Various Arenes 1 in the Presence of [Pd(dppe)(OAc)2] Catalysta)
[Pd(dppe)(OAc)2]
CO2Et
Ar
H
+
CO2Et
Ar
TFA, CH2Cl2
CO2Et
1
2
3
Solvent/mL
Product and isolated yield/%b)
Entry
1c)
Arene Ar-H
TFA
0.25
CH2Cl2
3
4
0.75
0.75
0.5
3b
3c
3d
82
76
40
4b
9
7
1b
H
2
3
0.25
0.5
4c
1c
H
H
4d
16
1d
4d),e)
5
1d
1
0.25
0
0.75
3d
3e
75
73
4d
4e
7
5
1e
1f
H
OH
6
1
0.5
3f
66
4f
12
H
Br
7d)
8
1f
1
0.5
0.5
0.5
3f
3g
69
53
4f
4g
2
18
H
1g
9d),f)
10
1g
1
0.25
0.5
0.75
3g
3h
67
70
4g
4h
8
11
H
1h
OMe
a) Reaction conditions: [Pd(dppe)(OAc)2] (0.005 mmol), arene 1 (2 mmol), 2 (2 mmol), TFA, and CH2Cl2 at 30 °C
for 5 h. b) Yields are based on 2. c) Pentamethylbenzene (1.1 mmol) was used. d) [Pd(dppm)Cl2] (0.005 mmol) and
AgOAc (0.02 mmol) were used. e) p-Xylene (3 mmol) was used. f) 10 h.
understood by clarifying the stereochemistry and absolute
structure of arylbutadienes 3. In the 1H NMR spectra of 1-aryl-
1,3-butadienes, the coupling constant J value is 15.8-15.9 Hz
for vicinal hydrogens of one olefinic double bond, showing
that this structure is trans configuration, as shown in Figure 1.
Concerning another double bond, differential NOE experiments
were conducted to determine the stereochemistry. Irradiation of
the hydrogen on the 4 position showed 16-20% enhancement
in intensity of the vinylic proton at the 2 position, indicating
that the hydrogens at the 2 and 4 positions are spatially close
(Figure 1). These results show that all arylbutadienes obtained
by this study have a (1E,3Z)-butadiene structure. Furthermore,
a single-crystal X-ray structural analysis was conducted.
Although most arylbutadienes were oil, fortunately arylbuta-
diene 3b from pentamethylbenzene was crystal. A single
crystal suitable for an X-ray analysis was obtained by slow
evaporation from a solution of arylbutadiene 3b in EtOH. The
ORTEP structure obtained by a single X-ray structural analysis
is depicted in Figure 2. From this result, it is clear that 3b has
the (1E,3Z)-1,3-butadiene structure.
The above structural analyses suggest that the arylbutadiene
formation consists of the initial anti addition of an arene and a
metal to the triple bond of ethyl propiolate and the subsequent
syn addition to another molecule of ethyl propiolate followed
by protonation.
Effect of Bidentate Phosphine Ligands on Pt-Catalyzed
Reaction. Since a cationic platinum catalyst showed a high
selectivity toward hydroarylation of alkynes compared with
a cationic palladium catalyst, arylbutadienes were hardly
formed in the Pt-catalyzed hydroarylation reaction.6 Then, to
evaluate the effect of a bidentate phosphine ligand on the
arylbutadiene formation, we examined the reaction of arenes
and ethyl propiolate in the presence of a platinum catalyst with
a bidentate phosphine ligand.

J. Oyamada et al.
Bull. Chem. Soc. Jpn. Vol. 86, No. 1 (2013)
133
NOE
+
CO2Et
EtO2C
J = 15.8−15.9 Hz
H
4
H
2
2
4a
(2 mmol)
(2 mmol)
E
Ar
1
3
[Pd(dppe)(OAc)2] (0.005 mmol)
CO2Et
E
H
TFA (0.5 mL), CH2Cl2 (0.5 mL) EtO2C
CO2Et
3i (72%)
Figure 1. Stereochemistry of 1-aryl-1,3-butadienes.
30 °C, 5 h
[Pd(dppe)(OAc)2]
(0.005 mmol)
EtO2C
+
CO2Et
EtO2C
3a
TFA (1 mL), 30 °C, 5 h
2
(2 mmol)
(2 mmol)
EtO2C
CO2Et
CO2Et
EtO2C
3j (76%)
Scheme 4. Application to extended ³-conjugated molecules.
Figure 2. ORTEP representation of 3b.
Table 4. Optimization of Reaction Conditions for Pt-Catalyzed Reaction of 1a with 2a)
Pt(II) catalyst
CO2Et
+
CO2Et
+
+
CO2Et
3a
EtO2C
CO2Et
CO2Et
TFA, CH2Cl2
2
1a
4a
5a
Yield/%b)
TFA
/mL
CH2Cl2
/mL
Entry
Catalyst
3a
4a
5a
1
2
3
4
5
6
7
8
9
[Pt(dppm)(OTf)2]
[Pt(dppm)(OTf)2]
[Pt(dppe)(OTf)2]
[Pt(dppe)(OTf)2]
[Pt(dppp)(OTf)2]
1
0
31
25
45
75
73
66
79
84
79
0
13
8
3
12
10
6
16
8
15
15
3
2
0
1
0
0
0
0.5
0.25
1
1
0.5
1
0.5
0.25
1
0.5
0.75
0
0
0.5
0
0.5
0.75
0
[Pt(dppp)(OTf)2]
[Pt(R-BINAP)(OTf)2]
[Pt(R-BINAP)(OTf)2]
[Pt(R-BINAP)(OTf)2]
[Pt(COD)Cl2]/2AgOTf
2
13
10
0
a) Reaction conditions: Pt catalyst (0.005 mmol), mesitylene (2 mmol), ethyl propiolate (2 mmol), TFA, and CH2Cl2 at 30 °C
for 5 h. b) Yields were determined by GC and based on the least amount of the substrate.
To determine optimum conditions, we first examined the
reaction of mesitylene and ethyl propiolate in the presence of
Pt(OTf)2 complex with bidentate ligands such as dppm, dppe,
dppp, and BINAP. The results are given in Table 4. In the case
of the dppm ligand, the yields of arylbutadiene 3a were only
31% and 25%, in TFA solvent and in a mixed solvent of TFA
and dichloromethane, respectively (Entries 1 and 2). Although
the reaction with the dppe ligand under the same conditions as
the Pd-catalyzed reaction did not give a good result (Entry 3),
the same reaction in TFA only afforded arylbutadiene 3a in
75% yield (Entry 4). The dppp ligand showed a similar effect
to the dppe ligand to give arylbutadiene 3a in 73% yield
(Entry 5), but use of a mixed solvent of TFA and dichloro-
methane decreased the yield to 66% (Entry 6). The BINAP
ligand as the bidentate ligand gave an excellent effect (Entries
7-9), but the COD ligand did not show a good effect due to its
loose coordination (Entry 10).
Using the [Pt(dppe)(OTf)2] catalyst which gave good results,
we examined the reaction of various aromatic substrates and
ethyl propiolate. The results are given in Table 5. Arylbuta-
diene 3a was isolated in 72-79% yield in the reactions of
mesitylene 1a with [Pt(dppe)(OTf)2], [Pt(dppp)(OTf)2], and
[Pt(R-BINAP)(OTf)2] catalysts under conditions similar to
mentioning above (Entries 1-3). In the case of pentamethyl-
benzene (1b), the reaction was conducted in a mixed sol-
vent of TFA and dichlorometane due to its low solubility.
In any cases of [Pt(dppe)(OTf)2], [Pt(dppp)(OTf)2], and [Pt(R-
BINAP)(OTf)2] catalysts, arylbutadiene 3b was obtained
in 74-79% yield (Entries 4-6). The reaction with 1,2,4,5-
tetramethylbenzene (1c) gave arylbutadiene 3c in 74% yield

134
Bull. Chem. Soc. Jpn. Vol. 86, No. 1 (2013)
Regio- and Stereocontrolled Reaction of Arenes with Ethyl Propiolate
E
Table 5. The Reaction of 2 with Various Arenes 1 in the
Presence of [Pt(dppe)(OTf)2]a)
Ar
E
H
3
P
P
E
[Pt(dppe)(OTf)2]
M+X
CO2Et
Ar
H
+
CO2Et
Ar
2
TFA, CH2Cl2
CO2Et
1
2
HX
3
TFA
/mL
CH2Cl2
/mL
Yield
E
Entry
1c)
Arene
Product
/%b)
Ar
P
P
E
M+
M+X
1a
1a
1a
1b
1b
1b
1c
1d
1e
1f
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0.25
0.25
0.25
0.35
0.5
0
3a
3a
3a
3b
3b
3b
3c
3d
3e
3f
73
72
79
74
74
79
74
32g)
75
75
37
2c),d)
3c),e)
4f)
P
P
E
Ar
H
5d),f)
6e)
7
8c)
9
10
11
E
P
M
H+
X
Ar
P
P
E
M
0.5
0.5
Ar
P
1g
3g
E
X
a) Reaction conditions: [Pt(dppe)(OTf)2] (0.005 mmol), arene
1 (2 mmol), 2 (2 mmol), TFA, and CH2Cl2 at 30 °C for 5 h.
b) Isolated yields based on 2. c) An arene 1 (3 mmol) was used.
d) [Pt(dppp)(OTf)2] was used instead of [Pt(dppe)(OTf)2].
e) [Pt(R-BINAP)(OTf)2] was used instead of [Pt(dppe)(OTf)2].
f) Pentamethylbenzene (1.1 mmol) was used. g) GC yield.
E
2
M = Pd, Pt
= a bidentate phosphine ligand
P
X = OCOCF3, OTf
P
E = CO2Et
Scheme 6. Possible mechanism for arylbutadiene formation.
[Pd(dppe)(OAc)2]
(0.005 mmol)
+
CO2Et
4b
(1 mmol)
CO2Et
Ar
it is thought that a similar mechanism holds even in the present
reaction. A possible mechanism concerning generation of
arylbutadienes 3 is shown in Scheme 6. First, a cationic Pd
or Pt catalyst with a bidentate ligand coordinates with ethyl
propiolate (2) and forms a highly electrophilic alkyne complex,
which undergoes aromatic electrophilic substitution with an
aromatic compound to give an arylvinylmetal intermediate. If
this intermediate causes protonation, hydroarylation product 4
will be generated, but the present reaction affords arylbutadiene
3 predominantly. Therefore, it is thought that the bidentate
ligand has two roles: control of protonation and promotion of
alkyne insertion. In this vinylmetal intermediate then, ligand
exchange with ethyl propiolate occurs to form an alkyne-
coordinated intermediate. In this intermediate, since the alkyne
and the arylvinyl group exist close due to the presence of the
bidentate ligand, insertion of the alkyne to the vinyl-metal
bond takes place easily in the syn manner. The resulting
arylbutadienylmetal intermediate undergoes protonation to
generate arylbutadiene 3 with concomitant regeneration of the
catalyst. Thus, the stereocontrolled arylbutadiene 3 is formed
by the anti addition and the syn addition to alkyne 2.
TFA (0.25 mL)
CH2Cl2 (0.75 mL)
30 °C, 5 h
2
(1.1 mmol)
Ar = Pentamethylphenyl
CO2Et
+
Ar
CO2Et
Ar
CO2Et
3b
4b
0% (by GC)
82%
Scheme 5. Attempted reaction of 4b with 2.
(Entry 7), but the reaction with p-xylene (1d) decreased in the
yield of arylbutadiene 3d to 32%, because of its low reactivity
(Entry 8). 2,4,6-Trimethylphenol (1e) and 2-bromomesitylene
(1f) also reacted effectively to give arylbutadienes 3e and 3f
in good yields, respectively (Entries 9 and 10). The reaction
with naphthalene (1b) resulted in a low yield (Entry 11).
Although the platinum catalyst causes the hydroarylation
reaction preferentially as compared with the palladium cata-
lyst, the above-mentioned results show that the formation of
arylbutadiene occurs preferentially when the platinum catalyst
has a suitable bidentate ligand.
Conclusion
Reaction Mechanism.
To check a possibility for the
formation of arylbutadienes 3 from hydroarylation products 4,
we examined the reaction of 4b with 2 (Scheme 5). However,
we could not detect the formation of 3b but found that the
starting material 4b remained unchanged. Therefore, this result
suggests that hydroarylation products 4 are not the intermedi-
ates for arylbutadienes 3.
In conclusion, we have demonstrated that the reaction of
arenes with ethyl propiolate in the presence of palladium or
platinum catalyst could be controlled by a bidentate phosphine
ligand. The bidentate phosphine ligand controls the reaction
regio- and stereoselectively to give the arylbutadienes by suc-
cessive reactions consisting of anti addition of an arene and a
metal to the triple bond of ethyl propiolate and syn addition to
another molecule of ethyl propiolate followed by protonation.
Since arylbutadienes 3 are also generated in low yield in the
Pd-catalyzed hydroarylation of 2 without a bidentate ligand,3,4

J. Oyamada et al.
Bull. Chem. Soc. Jpn. Vol. 86, No. 1 (2013)
135
Since this reaction provides arylbutadienes as well as ³-
conjugated aromatic olefins, this methodology will be useful
for organic synthesis directed to biological and material
science.
Ethyl (2Z)-3-(2,4,6-Trimethylphenyl)-2-propenoate (4a):3b
Colorless liquid. H NMR (300 MHz, CDCl3): ¤ 1.10 (t, J =
7.1 Hz, 3H, CH3), 2.16 (s, 6H, CH3), 2.27 (s, 3H, CH3), 4.03 (q,
J = 7.1 Hz, 2H, CH2), 6.11 (d, J = 12.0 Hz, 1H, vinyl), 6.84 (s,
2H, aryl), 7.02 (d, J = 12.0 Hz, 1H, vinyl). 13C NMR (75 MHz,
CDCl3): ¤ 13.94, 20.11, 21.01, 59.92, 122.77, 127.78, 132.77,
134.44, 136.65, 144.13, 165.47.
1
Experimental
All chemicals and solvents used in the reaction were
commercially available and used as received without further
purification. [Pd(dppe)(OAc)2],7 [Pd(dppp)(OAc)2],8 [Pd-
(PPh3)2(OAc)2],9 and [Pd(dppe)2(OAc)2]10 were prepared from
Pd(OAc)2 and the corresponding phosphine according to
the literature. [PdCl2(PhCN)2] was prepared from PdCl2 and
benzonitrile according to the literature.11 [Pd(dppm)Cl2] was
prepared from [PdCl2(PhCN)2] and dppm according to a
reported method.12 Thin layer chromatography (TLC) analyses
were carried out using TLC aluminum sheets (Silica gel 60
F254). Silica gel column chromatography was carried out using
Silica Gel 60 (spherical, 63-210 ¯m). 1H and 13C NMR spectra
were recorded on a JEOL JNM-AL 300 FT-NMR using tetra-
methylsilane (TMS) as an internal standard. Melting points
were measured with a YANACO micro melting apparatus and
are not corrected. GC analyses were performed on a Shimadzu
GC-14B equipped with a flame ionization detector using
capillary column (DB-1, 15 m © 0.53 mm i.d. © 1.5 mm film
thickness). GC yields were determined using n-heptadecane or
n-pentadecane as an internal standard. Elemental analyses were
performed by the Service Center of the Elemental Analysis of
Organic Compounds, Faculty of Science, Kyushu University.
Reaction of Mesitylene (1a) with Ethyl Propiolate (2) in
Diethyl 2,4,6-Trimethylbenzene-1,3-di[(2Z)-2-propeno-
1
nate] (5a):3b Colorless liquid. H NMR (300 MHz, CDCl3):
¤ 1.12 (t, J = 7.1 Hz, 6H, CH3), 2.05 (s, 3H, CH3), 2.15 (s, 6H,
CH3), 4.03 (q, J = 7.1 Hz, 4H, CH2), 6.12 (d, J = 11.9 Hz, 2H,
vinyl), 6.88 (s, 1H, aryl), 7.03 (d, J = 11.9 Hz, 2H, vinyl).
13C NMR (75 MHz, CDCl3): ¤ 13.98, 17.66, 20.17, 59.90,
122.68, 128.36, 130.97, 132.98, 133.46, 144.40, 165.38.
Genaral Procedure for [Pd(dppe)(OAc)2]- or [Pt(dppe)-
(OTf)2]-Catalyzed Reaction of an Arene with Ethyl Pro-
piolate (2). After a mixture of [Pd(dppe)(OAc)2] or [Pt(dppe)-
(OTf)2] (0.005 mmol), an arene (2 mmol), TFA, and CH2Cl2
was stirred on an ice/water bath for 10 min, ethyl propiolate (2)
(2 mmol) was added to the cold mixture (the amounts of
solvents are described in Tables 3 and 5). Again, the mixture
was stirred on an ice/water bath for 5 min. Then, the mixture
was stirred at 30 °C. After the reaction, the mixture was poured
into water (20 mL), neutralized by NaHCO3, and extracted with
CH2Cl2 (20 mL + 10 mL © 3). The organic layer was dried
over Na2SO4 and concentrated under reduced pressure. The
residue was purified by silica gel column chromatography
using EtOAc/hexane as eluent, affording arylbutadienes 3. In
the reaction using [Pd(dppm)Cl2] and AgOAc as the catalyst,
the catalyst was prepared by stirring a mixture of [Pd-
(dppm)Cl2] (0.005 mmol) and AgOAc (0.02 mmol) in TFA
and CH2Cl2 at room temperature for 30 min. Then, an arene
(2 mmol) was added and the mixture was stirred on an ice/
water bath for 10 min. After addition of ethyl propiolate
(2 mmol), the mixture was stirred on an ice/water bath for
5 min. Then, the mixture was stirred at 30 °C.
the Presence of a Pd or Pt Catalyst.
To a Pyrex tube
equipped with a magnetic stirring bar were added a Pd or Pt
catalyst (0.005 mmol), mesitylene (1a), TFA and CH2Cl2, and
then capped with a septum rubber. After the mixture was stirred
on an ice/water bath for 10 min, ethyl propiolate (2) was added
to the cold mixture (the amounts of starting materials and
solvents are described in Tables 1 and 4). Again, the mixture
was stirred on an ice/water bath for 5 min and then stirred
at 30 °C. After 5 h, n-heptadecane (ca. 0.15 g) as an internal
standard was added to the reaction mixture. The mixture
was poured into water (20 mL), neutralized with NaHCO3, and
extracted with Et2O (20 mL, 10 mL © 2). The ethereal layer
was analyzed by GC to determine the yields of the products
3a, 4a, and 5a. These products were isolated and purified by
column chromatography on silica gel with EtOAc/hexane as
eluent.
1
All products were characterized by H and 13C NMR. The
stereochemistry of arylbutadiene 3 was determined by coupling
constant in 1H NMR spectra and differential NOE experiments.
Diethyl
(2E,4Z)-4-[(Pentamethylphenyl)methylene]-2-
pentenedioate (3b):3b
Colorless crystals. Mp 79-81 °C
1
(MeOH). H NMR (300 MHz, CDCl3): ¤ 0.87 (t, J = 7.1 Hz,
3H, CH3), 1.32 (t, J = 7.1 Hz, 3H, CH3), 2.12 (s, 6H, CH3),
2.18 (s, 6H, CH3), 2.22 (s, 3H, CH3), 3.97 (q, J = 7.1 Hz, 2H,
CH2), 4.25 (q, J = 7.1 Hz, 2H, CH2), 6.20 (d, J = 15.8 Hz, 1H,
vinyl), 7.26 (s, 1H, vinyl), 7.49 (d, J = 15.8 Hz, 1H, vinyl).
13C NMR (75.5 MHz, CDCl3): ¤ 13.40, 14.26, 16.19, 16.66,
17.78, 60.47, 60.52, 120.41, 130.36, 132.04, 132.44, 133.98,
134.44, 141.47, 145.25, 166.01, 166.83.
In the case of [Pd(dppm)(OAc)2], the catalyst was prepared
in situ from [Pd(dppm)Cl2] and AgOAc. The effect of the
acids was examined by the same conditions as above, except
for TFA.
Diethyl (2E,4Z)-4-[(2,4,6-Trimethylphenyl)methylene]-2-
Diethyl (2E,4Z)-4-[(2,3,5,6-Tetramethylphenyl)methyl-
1
pentenedioate (3a):3b Colorless liquid. H NMR (300 MHz,
ene]-2-pentenedioate (3c):3b
Colorless liquid. 1H NMR
CDCl3): ¤ 0.90 (t, J = 7.1 Hz, 3H, CH3), 1.32 (t, J = 7.1 Hz,
3H, CH3), 2.15 (s, 6H, CH3), 2.26 (s, 3H, CH3), 3.99 (q,
J = 7.1 Hz, 2H, CH2), 4.25 (q, J = 7.1 Hz, 2H, CH2), 6.22 (d,
J = 15.9 Hz, 1H, vinyl), 6.83 (s, 2H, aryl), 7.15 (s, 1H, vinyl),
7.46 (d, J = 15.9 Hz, 1H, vinyl). 13C NMR (75.5 MHz, CDCl3):
¤ 13.44, 14.24, 20.08, 20.94, 60.49, 60.70, 120.72, 127.81,
132.05, 134.40, 135.15, 137.29, 141.36, 143.06, 166.03,
166.80.
(300 MHz, CDCl3): ¤ 0.84 (t, J = 7.1 Hz, 3H, CH3), 1.32 (t,
J = 7.1 Hz, 3H, CH3), 2.06 (s, 6H, CH3), 2.20 (s, 6H, CH3),
3.95 (q, J = 7.1 Hz, 2H, CH2), 4.25 (q, J = 7.1 Hz, 2H, CH2),
6.22 (d, J = 15.9 Hz, 1H, vinyl), 6.90 (s, 1H, aryl), 7.22 (s, 1H,
vinyl), 7.49 (d, J = 15.9 Hz, 1H, vinyl). 13C NMR (75.5 MHz,
CDCl3): ¤ 13.34, 14.26, 16.63, 19.78, 60.51, 60.54, 120.62,
130.86, 130.92, 133.27, 134.18, 134.93, 141.34, 144.42,
165.99, 166.83.

136
Bull. Chem. Soc. Jpn. Vol. 86, No. 1 (2013)
(2E,4Z)-4-[(2,5-Dimethylphenyl)methylene]-2-
Regio- and Stereocontrolled Reaction of Arenes with Ethyl Propiolate
Diethyl
Hz, 3H, CH3), 2.04 (s, 3H, CH3), 2.15 (s, 6H, CH3), 4.01
(q, J = 7.1 Hz, 2H, CH2), 4.03 (q, J = 7.1 Hz, 2H, CH2), 4.24
(q, J = 7.1 Hz, 2H, CH2), 6.13 (d, J = 11.9 Hz, 1H, vinyl), 6.22
(d, J = 15.9 Hz, 1H, vinyl), 6.87 (s, 1H, aryl), 6.99 (d, J = 11.9
Hz, 1H, vinyl), 7.15 (s, 1H, vinyl), 7.46 (d, J = 15.9 Hz, 1H,
vinyl). 13C NMR (75.5 MHz, CDCl3): ¤ 13.54, 13.99, 14.24,
17.77, 20.10, 59.86, 60.49, 60.76, 120.71, 122.89, 128.40,
131.71, 132.27, 133.18, 134.16, 134.18, 134.44, 141.38,
143.11, 143.78, 165.10, 165.96, 166.78.
pentenedioate (3d):5 Colorless liquid. H NMR (300 MHz,
CDCl3): ¤ 1.11 (t, J = 7.1 Hz, 3H, CH3), 1.32 (t, J = 7.1 Hz,
3H, CH3), 2.26 (s, 3H, CH3), 2.29 (s, 3H, CH3), 4.17 (q, J =
7.1 Hz, 2H, CH2), 4.24 (q, J = 7.1 Hz, 2H, CH2), 6.08 (d, J =
15.9 Hz, 1H, vinyl), 7.02-7.09 (m, 3H, aryl), 7.14 (s, 1H,
vinyl), 7.42 (d, J = 15.9 Hz, 1H, vinyl). 13C NMR (75.5 MHz,
CDCl3): ¤ 13.70, 14.25, 19.34, 20.79, 60.52, 61.17, 120.23,
128.28, 129.94, 130.08, 132.51, 133.74, 133.93, 135.09,
139.90, 142.32, 166.73, 167.29.
1
Tetraethyl
2,4,6-Trimethylbenzene-1,3-bis[(2E,4Z)-4-
Diethyl (2E,4Z)-4-[(3-Hydroxy-2,4,6-trimethylphenyl)-
methylene]-2-pentenedioate (3e):5 Yellow viscous liquid.
1H NMR (300 MHz, CDCl3): ¤ 0.92 (t, J = 7.1 Hz, 3H, CH3),
1.32 (t, J = 7.1 Hz, 3H, CH3), 2.08 (s, 6H, CH3), 2.20 (s, 3H,
CH3), 4.00 (q, J = 7.1 Hz, 2H, CH2), 4.25 (q, J = 7.1 Hz, 2H,
CH2), 4.77 (br s, 1H, OH), 6.23 (d, J = 15.9 Hz, 1H, vinyl),
6.79 (s, 1H, aryl), 7.12 (s, 1H, vinyl), 7.47 (d, J = 15.9 Hz,
1H, vinyl). 13C NMR (75.5 MHz, CDCl3): ¤ 13.16, 13.47,
14.23, 15.84, 19.45, 60.58, 60.76, 120.72, 120.79, 122.53,
126.78, 129.20, 133.49, 134.44, 141.37, 142.88, 149.89,
165.99, 166.87.
(ethoxycarbonyl)-2,4-pentadienoate] (3j):5
Light yellow
1
viscous liquid. H NMR (300 MHz, CDCl3): ¤ 0.99 (t, J = 7.1
Hz, 6H, CH3), 1.32 (t, J = 7.1 Hz, 6H, CH3), 2.04 (s, 3H, CH3),
2.15 (s, 6H, CH3), 4.03 (q, J = 7.1 Hz, 4H, CH2), 4.25 (q,
J = 7.1 Hz, 4H, CH2), 6.21 (d, J = 15.9 Hz, 2H, vinyl), 6.86 (s,
1H, aryl), 7.11 (s, 2H, vinyl), 7.46 (d, J = 15.9 Hz, 2H, vinyl).
13C NMR (75.5 MHz, CDCl3): ¤ 13.64, 14.25, 17.92, 20.12,
60.56, 60.79, 120.93, 128.53, 132.45, 132.48, 134.62, 134.89,
141.27, 142.47, 165.75, 166.73.
Ethyl (2Z)-3-(Pentamethylphenyl)-2-propenoate (4b):3b
Colorless crystals. 1H NMR (300 MHz, CDCl3): ¤ 1.10 (t,
J = 7.1 Hz, 3H, CH3), 2.14 (s, 6H, CH3), 2.20 (s, 6H, CH3),
2.22 (s, 3H, CH3), 4.02 (q, J = 7.1 Hz, 2H, CH2), 6.13 (d, J =
11.9 Hz, 1H, vinyl), 7.13 (d, J = 11.9 Hz, 1H, vinyl). 13C NMR
(75.5 MHz, CDCl3): ¤ 13.95, 16.35, 16.74, 17.59, 59.76,
122.09, 129.73, 131.87, 133.20, 133.93, 146.48, 165.39.
Ethyl (2Z)-3-(2,3,5,6-Tetramethylphenyl)-2-propenoate
Diethyl
(2E,4Z)-4-[(3-Bromo-2,4,6-trimethylphenyl)-
Colorless liquid.
methylene]-2-pentenedioate (3f):5
1H NMR (300 MHz, CDCl3): ¤ 0.90 (t, J = 7.1 Hz, 3H, CH3),
1.32 (t, J = 7.1 Hz, 3H, CH3), 2.11 (s, 3H, CH3), 2.29 (s, 3H,
CH3), 2.37 (s, 3H, CH3), 3.99 (q, J = 7.1 Hz, 2H, CH2), 4.24
(q, J = 7.1 Hz, 2H, CH2), 6.25 (d, J = 15.9 Hz, 1H, vinyl),
6.92 (s, 1H, aryl), 7.13 (s, 1H, vinyl), 7.46 (d, J = 15.9 Hz,
1H, vinyl). 13C NMR (75.5 MHz, CDCl3): ¤ 13.46, 14.26,
19.89, 21.50, 23.88, 60.61, 60.85, 121.44, 125.03, 129.33,
133.84, 133.93, 134.77, 135.06, 137.58, 140.89, 142.10,
165.64, 166.67.
1
(4c):3b Colorless liquid. H NMR (300 MHz, CDCl3): ¤ 1.07
(t, J = 7.1 Hz, 3H, CH3), 2.08 (s, 6H, CH3), 2.21 (s, 6H, CH3),
4.00 (q, J = 7.1 Hz, 2H, CH2), 6.14 (d, J = 11.9 Hz, 1H, vinyl),
6.90 (s, 1H, aryl), 7.09 (d, J = 11.9 Hz, 1H, vinyl). 13C NMR
(75.5 MHz, CDCl3): ¤ 13.86, 16.47, 19.93, 59.80, 122.44,
130.21, 130.51, 133.02, 135.69, 145.59, 165.43.
Diethyl (2E,4Z)-4-(1-Naphthylmethylidene)-2-pentene-
dioate (3g):5
Yellow viscous liquid. 1H NMR (300 MHz,
Ethyl (2Z)-3-(2,5-Dimethylphenyl)-2-propenoate (4d):3b
1
CDCl3): ¤ 0.91 (t, J = 7.1 Hz, 3H, CH3), 1.33 (t, J = 7.1 Hz,
3H, CH3), 4.05 (q, J = 7.1 Hz, 2H, CH2), 4.26 (q, J = 7.1 Hz,
2H, CH2), 6.18 (d, J = 15.8 Hz, 1H, vinyl), 7.38-7.58 (m, 5H,
naphthyl and vinyl), 7.65 (s, 1H, vinyl), 7.82-7.96 (m, 3H,
naphthyl). 13C NMR (75.5 MHz, CDCl3): ¤ 13.56, 14.27,
60.59, 61.14, 120.96, 124.09, 125.07, 126.08, 126.23,
126.69, 128.58, 129.57, 131.20, 132.45, 133.32, 134.25,
138.97, 141.90, 166.67, 167.02.
Diethyl (2E,4Z)-4-(2-Methoxy-1-naphthylmethylidene)-2-
pentenedioate (3h):5 Light yellow solid. 1H NMR (300 MHz,
CDCl3): ¤ 0.75 (t, J = 7.1 Hz, 3H, CH3), 1.33 (t, J = 7.1 Hz,
3H, CH3), 3.90 (s, 3H, OCH3), 3.91 (q, J = 7.1 Hz, 2H, CH2),
4.26 (d, J = 7.1 Hz, 2H, CH2), 6.39 (d, J = 15.8 Hz, 1H, vinyl),
7.24 (d, J = 9.2 Hz, 1H, aryl), 7.35 (dd, J = 6.9, 8.1 Hz, 1H,
aryl), 7.47 (dd, J = 6.9, 8.4 Hz, 1H, aryl), 7.50 (s, 1H, vinyl),
7.59 (d, J = 15.8 Hz, 1H, vinyl), 7.78 (d, J = 8.1 Hz, 1H, aryl),
7.79 (d, J = 8.4 Hz, 1H, aryl), 7.84 (d, J = 9.2 Hz, 1H, aryl).
13C NMR (75.5 MHz, CDCl3): ¤ 13.28, 14.23, 56.00, 60.35,
60.41, 112.50, 118.20, 120.29, 123.59, 123.80, 127.04, 128.28,
128.59, 130.73, 132.09, 133.86, 137.64, 142.51, 154.22,
166.18, 166.98.
Colorless liquid. H NMR (300 MHz, CDCl3): ¤ 1.15 (t, J =
7.1 Hz, 3H, CH3), 2.23 (s, 3H, CH3), 2.30 (s, 3H, CH3), 4.09 (q,
J = 7.1 Hz, 2H, CH2), 6.00 (d, J = 12.1 Hz, 1H, vinyl), 7.00-
7.07 (m, 2H, aryl), 7.08 (d, J = 12.1 Hz, 1H, vinyl), 7.12 (s,
1H, aryl). 13C NMR (75.5 MHz, CDCl3): ¤ 13.92, 19.29, 20.85,
60.02, 120.99, 129.06, 129.24, 129.52, 132.59, 134.44, 134.86,
142.81, 166.07.
Ethyl (2Z)-3-(3-Hydroxy-2,4,6-trimethylphenyl)-2-prope-
noate (4e):3b Colorless liquid. 1H NMR (300 MHz, CDCl3): ¤
1.12 (t, J = 7.1 Hz, 3H, CH3), 2.09 (s, 6H, CH3), 2.17 (s, 3H,
CH3), 4.04 (q, J = 7.1 Hz, 2H, CH2), 4.65 (br s, 1H, OH), 6.13
(d, J = 11.9 Hz, 1H, vinyl), 6.79 (s, 1H, aryl), 7.00 (d, J = 11.9
Hz, 1H, vinyl). 13C NMR (75.5 MHz, CDCl3): ¤ 12.95, 13.93,
15.84, 19.51, 59.99, 120.23, 121.93, 122.72, 126.03, 129.09,
134.20, 144.07, 149.77, 165.42.
Ethyl (2Z)-3-(3-Bromo-2,4,6-trimethylphenyl)-2-prope-
1
noate (4f):3b Colorless liquid. H NMR (300 MHz, CDCl3):
¤ 1.09 (t, J = 7.1 Hz, 3H, CH3), 2.11 (s, 3H, CH3), 2.30 (s, 3H,
CH3), 2.40 (s, 3H, CH3), 4.02 (q, J = 7.1 Hz, 2H, CH2), 6.13
(d, J = 11.9 Hz, 1H, vinyl), 6.93 (s, 1H, aryl), 7.02 (d, J =
11.9 Hz, 1H, vinyl). 13C NMR (75.5 MHz, CDCl3): ¤ 13.88,
19.91, 21.24, 23.91, 60.07, 123.24, 125.02, 129.27, 133.18,
134.34, 134.58, 136.92, 143.59, 165.17.
Diethyl (2E,4Z)-4-{3-[(1Z)-2-(Ethoxycarbonyl)ethenyl]-
2,4,6-trimethylbenzylidene}-2-pentenedioate (3i):5 Color-
less viscous liquid. 1H NMR (300 MHz, CDCl3): ¤ 0.96 (t, J =
7.1 Hz, 3H, CH3), 1.14 (t, J = 7.1 Hz, 3H, CH3), 1.32 (t, J = 7.1
Ethyl (2Z)-3-(1-Naphthyl)-2-propenoate (4g):3b Colorless
1
liquid. H NMR (300 MHz, CDCl3): ¤ 1.00 (t, J = 7.1 Hz, 3H,

J. Oyamada et al.
Bull. Chem. Soc. Jpn. Vol. 86, No. 1 (2013)
137
S. Murai, Springer, Berlin, 1999, Vol. 3, pp. 47-79. doi:10.1007/
3-540-68525-1_3. c) G. Dyker, Angew. Chem., Int. Ed. 1999, 38,
1698. d) Y. Guari, S. Sabo-Etienne, B. Chaudret, Eur. J. Inorg.
Chem. 1999, 1047. e) R. H. Crabtree, J. Chem. Soc., Dalton Trans.
2001, 2437. f) C. Jia, T. Kitamura, Y. Fujiwara, Acc. Chem. Res.
2001, 34, 633. g) V. Ritleng, C. Sirlin, M. Pfeffer, Chem. Rev.
2002, 102, 1731. h) F. Kakiuchi, S. Murai, Acc. Chem. Res. 2002,
35, 826. i) F. Kakiuchi, N. Chatani, Adv. Synth. Catal. 2003, 345,
1077. j) D. Alberico, M. E. Scott, M. Lautens, Chem. Rev. 2007,
107, 174. k) F. Kakiuchi, T. Kochi, Synthesis 2008, 3013. l) X.
Chen, K. M. Engle, D.-H. Wang, J.-Q. Yu, Angew. Chem., Int. Ed.
2009, 48, 5094. m) L. Ackermann, R. Vicente, A. R. Kapdi,
Angew. Chem., Int. Ed. 2009, 48, 9792. n) T. W. Lyons, M. S.
Sanford, Chem. Rev. 2010, 110, 1147. o) C. S. Yeung, V. M. Dong,
Chem. Rev. 2011, 111, 1215. p) M. Klussmann, D. Sureshkumar,
Synthesis 2011, 353.
CH3), 4.00 (q, J = 7.1 Hz, 2H, CH2), 6.23 (d, J = 12.1 Hz,
1H, vinyl), 7.41-7.50 (m, 4H, naphthyl), 7.54 (d, J = 12.1 Hz,
1H, vinyl), 7.80-7.90 (m, 3H, naphthyl). 13C NMR (75.5
MHz, CDCl3): ¤ 13.77, 60.09, 122.77, 124.36, 124.95, 125.79,
126.19, 126.48, 128.49, 128.66, 131.04, 133.00, 133.22,
141.80, 165.88.
Ethyl (2Z)-3-(2-Methoxy-1-naphthyl)-2-propenoate (4h):
1
Light yellow liquid. H NMR (300 MHz, CDCl3): ¤ 0.86 (t,
J = 7.1 Hz, 3H, CH3), 3.90 (q, J = 7.1 Hz, 2H, CH2), 3.91 (s,
3H, OCH3), 6.32 (d, J = 11.9 Hz, 1H, vinyl), 7.26 (d, J = 9.0
Hz, 1H, naphthyl), 7.26 (d, J = 11.9 Hz, 1H, vinyl), 7.32 (dd,
J = 6.9, 8.1 Hz, 1H, naphthyl), 7.42 (dd, J = 6.9, 8.4 Hz, 1H,
naphthyl), 7.77 (d, J = 8.1 Hz, 1H, naphthyl), 7.77 (d, J =
8.4 Hz, 1H, naphthyl), 7.81 (d, J = 9.0 Hz, 1H, naphthyl).
13C NMR (75.5 MHz, CDCl3): ¤ 13.62, 56.27, 59.84, 112.77,
119.19, 123.51, 123.94, 124.28, 126.53, 128.16, 128.63,
129.68, 131.91, 137.44, 153.52, 165.94. MS (EI, m/z): 256
(M+, 40), 225 (15), 211 (15), 197 (33), 183 (100), 168 (38),
153 (29), 139 (44). IR (neat, cm¹1): 3058 (w), 2980 (m), 2840
(w), 1725 (n (C=O), s), 1623 (m), 1592 (m), 1510 (m), 1466
(m), 1268 (s), 1184 (s), 1086 (m), 1025 (m), 808 (m), 749 (m).
Anal. Calcd for C16H16O3: C, 74.98; H, 6.29%. Found: C,
75.00; H, 6.30%.
2
For reviews on hydroarylation of alkynes, see: a) C. Jia, T.
Kitamura, Y. Fujiwara, J. Synth. Org. Chem., Jpn. 2001, 59, 1052.
b) C. Nevado, A. M. Echavarren, Synthesis 2005, 167. c) T.
Kitamura, Eur. J. Org. Chem. 2009, 1111. d) X. Wang, L. Zhou, W.
Lu, Curr. Org. Chem. 2010, 14, 289. e) P. de Mendoza, A. M.
Echavarren, Pure Appl. Chem. 2010, 82, 801.
3
a) C. Jia, D. Piao, J. Oyamada, W. Lu, T. Kitamura, Y.
Fujiwara, Science 2000, 287, 1992. b) C. Jia, W. Lu, J. Oyamada,
T. Kitamura, K. Matsuda, M. Irie, Y. Fujiwara, J. Am. Chem. Soc.
2000, 122, 7252. c) C. Jia, D. Piao, T. Kitamura, Y. Fujiwara,
J. Org. Chem. 2000, 65, 7516. d) W. Lu, C. Jia, T. Kitamura, Y.
Fujiwara, Org. Lett. 2000, 2, 2927. e) J. Oyamada, W. Lu, C. Jia, T.
Kitamura, Y. Fujiwara, Chem. Lett. 2002, 20. f) J. Oyamada, C.
Jia, Y. Fujiwara, T. Kitamura, Chem. Lett. 2002, 380. g) T.
Kitamura, K. Yamamoto, M. Kotani, J. Oyamada, C. Jia, Y.
Fujiwara, Bull. Chem. Soc. Jpn. 2003, 76, 1889. h) M. Kotani, K.
Yamamoto, J. Oyamada, Y. Fujiwara, T. Kitamura, Synthesis 2004,
1466.
A Single-Crystal X-ray Anaylsis of 3b. A suitable single
crystal of 3b for an X-ray analysis was obtained by slow
evaporation of a solution of 3b in EtOH. Data were collected
on a Rigaku Saturn724 diffractometer using multilayer mirror
monochromated Mo K¡ radiation. All diagrams and calcula-
tions were performed using the CrystalStructure13 crystallo-
graphic software package except for refinement, which was
performed using SHELXL-97.14 Crystal data: C21H28O4,
ꢀ
Mr = 344.45, triclinic, space group P1 (#2), a = 8.178(3) ¡,
b = 11.007(5) ¡, c = 11.659(5) ¡, ¡ = 103.952(6)°, ¢ =
4
6440.
5
J. A. Tunge, L. N. Foresee, Organometallics 2005, 24,
92.334(5)°,
£ = 98.757(7)°, V = 1003.4(7) ¡3,
Z = 2,
¹3
¹1
D
calcd = 1.140 g cm
,
Mo K¡ radiation ® = 0.774 cm ,
For a preliminary report, see: J. Oyamada, T. Kitamura,
4505 reflections measured [(I > 2.00·(I)), 226 variables, R1
(I > 2.00·(I)) = 0.0687, R (all reflections) = 0.1015, wR2 (all
reflections) = 0.2436, goodness of fit indicator = 1.058. The
details of the X-ray structure determination is described in
Supporting Information. Crystallographic data have been
deposited with Cambridge Crystallographic Data Centre:
Deposition number CCDC 902760 for compound 3b. Copies
of the data can be obtained free of charge via http://www.ccdc.
cam.ac.uk/conts/retrieving.html (or from the Cambridge Crys-
tallographic Data Centre, 12, Union Road, Cambridge, CB2
1EZ, U.K.; Fax: +44 1223 336033; e-mail: deposit@ccdc.
cam.ac.uk).
Chem. Commun. 2008, 4992.
a) J. Oyamada, T. Kitamura, Tetrahedron Lett. 2005, 46,
6
3823. b) J. Oyamada, T. Kitamura, Chem. Lett. 2005, 34, 1430.
c) J. Oyamada, T. Kitamura, Tetrahedron 2007, 63, 12754.
d) J. Oyamada, T. Kitamura, Tetrahedron 2009, 65, 3842. e) J.
Oyamada, T. Hashimoto, T. Kitamura, J. Organomet. Chem. 2009,
694, 3626.
7
A. Marson, A. B. van Oort, W. P. Mul, Eur. J. Inorg. Chem.
2002, 3028.
8
P. Wehman, H. M. A. van Donge, A. Hagos, P. C. J. Kamer,
P. W. N. M. van Leeuwen, J. Organomet. Chem. 1997, 535, 183.
9
T. A. Stephenson, S. M. Morehouse, A. R. Powell, J. P.
Heffer, G. Wilkinson, J. Chem. Soc. 1965, 3632.
10 C. Bianchini, H. M. Lee, A. Meli, W. Oberhauser, M.
Peruzzini, F. Vizza, Organometallics 2002, 21, 16.
11 J. R. Doyle, P. E. Slade, H. B. Jonassen, R. N. Rhoda,
Inorg. Synth. 1960, 6, 216.
12 A. R. Sanger, J. Chem. Soc., Dalton Trans. 1977, 1971.
13 CrystalStructure 3.8.2: Crystal Structure Analysis Package,
Rigaku and Rigaku/MSC, The Woodlands, TX 77381, USA,
2007.
Supporting Information
NOE difference spectra of 3b-3j and details of the X-ray
structure determination of 3b. This material is available free of
charge on the web at http://www.csj.jp/journals/bcsj/.
References
1
For recent reviews on direct C-H functionalization, see:
a) A. E. Shilov, G. B. Shul’pin, Chem. Rev. 1997, 97, 2879. b) F.
Kakiuchi, S. Murai, in Activation of Unreactive Bonds and
Organic Synthesis in Topics in Organometallic Chemistry, ed. by
14 G. M. Sheldrick, SHELXL-97, Program for the Refinement
of Crystal Structures, University of Göttingen, Germany, 1997.