Bipyridine-modulated palladium-catalyzed oxidative heck-type reactions of arylboronic acids with olefins

Article abstract of DOI:10.1002/jccs.200900129

We have demonstrated that 4,4′-dimethyl 2,2′-bipyridine as ligand for Pd(II) catalysts was very efficient for oxidative Heck-type coupling reaction of arylboronic acids with olefins in DMA or CH₃CN under atm air at 80 °C. The presence of chelated bipyridine ligand isindispensable to achieve high reaction yields and to suppress the formation of biphenyl as homocoupled byproduct.

Full text of DOI:10.1002/jccs.200900129

Journal of the Chinese Chemical Society, 2009, 56, 873-880
873
Communication
Bipyridine-Modulated Palladium-catalyzed Oxidative Heck-type Reactions
of Arylboronic Acids with Olefins
Chien-Ming Hsu (
), Chih-Bin Li (
Department of Chemistry, Soochow University, Taipei 111, Taiwan, R.O.C.
) and Chia-Hsing Sun* (
)
We have demonstrated that 4,4¢-dimethyl 2,2¢-bipyridine as ligand for Pd(II) catalysts was very effi-
cient for oxidative Heck-type coupling reaction of arylboronic acids with olefins in DMA or CH3CN un-
der atm air at 80 °C. The presence of chelated bipyridine ligand isindispensable to achieve high reaction
yields and to suppress the formation of biphenyl as homocoupled byproduct.
Keywords: Bipyridine-modulated; 4,4¢-Dimethyl 2,2¢-bipyridine; Pd(II) catalysts; Oxidative
Heck-type coupling reaction; Arylboronic acids; Olefins.
INTRODUCTION
The transition metal-catalyzed cross-coupling reac-
their synthetic applications, it is intriguing to promote bi-
pyridine ligands for oxidative Heck reactions since bipyri-
dine ligands required are either commercially-available or
synthetically accessible. Herein we reported that 4,4¢-di-
methyl-2,2¢-bipyridine 1c was screened as the most supe-
rior ligand for for Pd(II) catalysts, it was very efficient for
oxidative Heck-type coupling reaction of arylboronic acids
with olefins in DMA or CH3CN under atm air at 80 °C in
high yields and without biphenyl as homo-coupled byprod-
uct.
tion of organoboronic acid and olefins, known as the oxida-
tive Heck reactions,1 is now growing rapidly as one of the
alternative tools for constructing C-C bonds, mainly be-
cause boronic acids are stable, low toxic, and commercially
available.2 Palladium-catalyzed oxidative Heck reactions3
have been extensively investigated by several research
groups including Larhed.’s in which a typical oxidative
Heck experiments was investigated in acetonitrile using.
p-Tolylboronic acid n-butyl acrylate N-methylmorpholine
(NMM) as base, ligand and 2% Pd(OAc)2 as the palladium
source.1d They found phenanthroline-class ligand, espe-
cially 2,9-dimthyl-1,10-phenanthroline (dmphen) ligand
provided high yields with good control over the regio-
chemistry and stereochemistry under open-air and at room
temperature.1d Other nitrogen-containing ligands such as
momodentate pyridine was ineffective, and both 2,2¢-bi-
pyridine and 6,6¢-dimethyl-2,2¢-bipyridine gave modest
production with Pd black formation for the latter. Generally
nitrogen-containing ligands, known to facilitate the reoxi-
dation of Pd(0) and stabilize Pd(II) complex thus formed,
are very cheap, air and moisture stable compared to their
phosphine counterparts.4 Nitrogen-containing ligands have
been found most successful when the reaction is run under
oxygen.1 Although the mechanistic aspect of the reaction is
not well-elucidated yet, based on the standpoint of better
understanding and control of oxidative Heck reactions and
RESULTS AND DISCUSSION
As illustrated in Table 1, several commercially avail-
able pyridine (1a) and bipyridine derivatives (1b-1k, ex-
cept 1f and 1j were prepared) were screened as potential
ligands, using a model cross-coupling reaction 1.0 mmol of
butyl acrylate and 2.0 mmol of phenylboronic acid in the
presence of 2 mol% of Pd(OAc)2, 2.4 mol% of ligand and
2.0 mmol of N-methylmorpholine (NMM) in 5.0 mL of
DMA at 80 °C in atm air. Ligand was found to be a crucial
factor in determining the yields of product 3a and biphenyl,
a homocoupled byproduct. Without ligand, only 2% of 3a
was produced with 18% of biphenyl isolated as the major
product (entry 1). Pyridine, a monodentate nitrogen ligand
did not work either. Among bidentate nitrogen ligands,
4,4¢-dimethyl-2,2¢-bipyridine 1c proved to be the most su-
perior one to give 3a in 96% yields, while 6,6¢-dimethyl-
2,2¢-bipyridine 1i gave considerably lower yields of 38%
* Corresponding author. E-mail: chsun@mail.scu.edu.tw

874 J. Chin. Chem. Soc., Vol. 56, No. 5, 2009
Hsu et al.
and significant amount of biphenyl as homocoupled by-
product due to the steric hindrance of dimethyl at 6,6¢-posi-
tion of bipyridyl (entry 10). Stronger electron-donating
methoxy group, at 4,4¢-position, did not improve but re-
sulted in lower reaction yields (entry 5) and at 6,6¢-posi-
tion, gave very low yield of 11% (entry 11). Even lower re-
action yields of 51% were obtained with electron-with-
drawing groups –COOH (entry 8), -COOMe (entry 9) and
poor yield of 11% with the strongest electron-withdrawing
group –CF3 (entry 7). Slight electron-withdrawing phenyl
group, at 4,4¢-position, gave moderate yield of 75% (entry
6), but poor yield of 11% at 6,6¢-position (entry 12). When
increasing ligand 1c from 2.4 mol% to 4.5 mol%, it resulted
in a yield decrease of 3a by 11%. From our observation, it
may suggest that dimethyl group at 4,4¢-position (1c) of
bipyridyl will give a tight bidentate-Pd coordination bond-
ing which afforded a stable Pd complex with higher cata-
lytic activity. However, dimethoxyl group at 4,4¢-positoin
(1d) of bipyridyl will give a stronger bonding to inhibit the
catalytic activity of Pd complex. It is also clear that weaker
coordination bonding between N-Pd-N will lead to low re-
action efficacy as electron-withdrawng groups were at-
tached at 4,4¢-positoin (1d) of bipyridyl. Generally, steric
hindrance imposed by substituents at 6,6¢-position of bi-
pyridyl will destabilize the Pd complex and lower the cata-
lytic activity. The presence of chelated bipyridine ligand is
indispensable to achieve high reaction yields and to sup-
press the formation of biphenyl as homocoupled byprod-
uct.
Table 1. Ligand screenig on oxidative arylation of n-butyl
acrylate with phenylboronic acida
B(OH)2
CO2Bu
2 mmol% Pd(OAc)2
2.4 mmol% Ligand
DMA,NMM,Air,80oC,24h
CO2Bu
+
+
4a
2a
3a
Yield
Yield of
Entry
Ligand
No L
(%)b biphenyl (%)b
1
2
2
1
18
1
1a
1b
N
3
4
51
1
N
N
N
N
96
6c
1
1c
0c
1d
85d
H3CO
OCH3
5
6
88
75
1
1
1d
N
N
N
N
Ar
Ar
1e
1f
F3C
CF3
7
8
11
51
51
1
3
2
N
N
N
N
HOOC
COOH
1g
To optimize the reaction condition, solvents were
found to have profound effect on palladium catalytic activ-
ity (Table 2). Attempts on optimization with respect to sol-
vent showed that the reaction proceeded best in DMA
(96%), Other aprotic polar solvents such as acetonitrile,
DMF and DMSO, except NMP, proved to be effective also
with no more than 90% yields. The nopolar solvents such
as dioxane and toluene gave lower yields. Notably, both
electronic effect and steric effect were pronounced for sub-
stituted arylboronic acids. Generally, electron-donating
arylboronic acids with MeO- or Me- at 4-position (entry 2
and entry 3) gave significantly higher yields than those of
electron-withdrawing arylboronic acids with Me(C=O)- or
CF3- at 4-position (entry 5 and entry 7) and NO2- at 3-posi-
tion (entry 10). Steric hindrance was found to decrease sig-
nificantly the reaction yields at 2-position (entry 4 and en-
try 9). But unsubstituted arylboronic acid (entry 1) af-
H3COOC
COOCH3
9
1h
1i
N
N
N
N
38
7
10
11
39c
20c
11
11
1
1
1j
N
N
H3CO
Ar
OCH3
Ar
12 1k
N
N
a Reaction conditions: 1.0 mmol of olefin, 2.0 mmol of boronic
acid, 2 mol% of Pd(OAc)2, 2.4 mol% of ligand, 2.0 mmol of
NMM, 5.0 mL of DMA.
b Isolated yield.
c Performed at rt, 5.0 mL of CH3CN.
d 4.5 mmol% Ligand.

Bipyridine-Modulated Heck-type Reactions
J. Chin. Chem. Soc., Vol. 56, No. 5, 2009 875
forded the highest yields than the substituted ones. Unex-
pectedly, electron-releasing 4-butyl diminished while elec-
tron-withdrawing 4-fluoro enhanced the reaction yields.
In a typical reaction mechanism proposed for Heck-
type coupling reaction, aryl group is transferred to bipyri-
dine palladium(II) intermediate to form an aryl palladium
complex (Scheme I). Presumably, the reactivity of bipyri-
dine aryl-Pd complex is determined by a resultant elec-
tronic balance on p-donating and p-accepting ability of sub-
stituent on aryl ring. Electron-donating group will increase
p-donating ability, meanwhile decrease its p-accepting
ability of aryl ring, and reverse are the electron-withdraw-
ing groups.
Table 2. Solvent effect on oxidative arylation of n-butyl acrylate
with phenylboronic acida
2 mmol% Pd(OAc)2
H3C
CH3
CO2Bu
2.4 mmol%
N
N
CO2Bu
+
B(OH)2
Solvent,NMM,Air,80oC,24h
Entry
Solvent
Yield (%)b
1
2
3
4
5
6
7
CH3CN
DMF
DMA
DMSO
NMP
Dioxane
Toluene
90
91
96
92
63
61
61
The open vessel procedure employing 6,6¢-dimethyl-
2,2¢-bipyridine 1i was thereafter applied directly to a range
of olefins (4a-f), utilizing phenylboronic acid (2a) as the
arylating agent (Table 4). Both electron-poor and elec-
tron-rich olefins were coupled in moderate to good yields.
a Reaction conditions: 1.0 mmol of olefin, 2.0 mmol of boronic
acid, 2.0 mmol of NMM, 5.0 mL of solvent.
b Isolated yield.
Scheme I Proposed mechanism for Heck-type oxidative arylation of olefins

876 J. Chin. Chem. Soc., Vol. 56, No. 5, 2009
Hsu et al.
Table 3. Oxidative arylation of n-butyl acrylate with diverse
Table 4. Oxidative arylation of different olefins with phenyl-
arylboronic acida
boronic acida
2 mmol% Pd(OAc)2
Products & Yield
Entry
Boronic acid
(%)b
H3C
CH3
2.4 mmol%
R
3a, 96c
B(OH)2
1
2
2a
2b
N
N
R
B(OH)2
+
DMA,NMM,Air,80oC,24h
3b, 90c
3c, 86
H3CO
B(OH)2
Product & Yield
(%)b
Entry
Olefin
a/bd
3
4
2c
H3C
B(OH)2
OBu
O
CH3
1
2
4a
4b
3a, 96
1/99
2d
3d, 32c
B(OH)2
5b, 36
2/98
5/95
5b, 93 c
5
6
7
8
2e
2f
3e, 68
3f, 84
3g, 35c
3h, 33
H3COC
F
B(OH)2
CH3
N
3
4
4c
5c, 88
5d, 68
1/99
99/1
CH3
B(OH)2
O
2g
2h
F3C
B(OH)2
B(OH)2
O
4d
N
n-Bu
a Reaction conditions: 1.0 mmol of olefin, 2.0 mmol of boronic
acid, 2.0 mmol of NMM, 5.0 mL of DMA.
b Isolated yield.
OCH3
9
2i
2j
3i, 29
3j, 24
B(OH)2
c Solvent is CH3CN.
d Determined by NMR.
O2N
10
B(OH)2
tonitrile with butyl acrylate (entry 1), and 85% yield with
styrene (entry 2). Importantly, 4,4¢-dimethyl 2,2¢-bipyri-
dine performed better at higher temperature 80 °C to give
96% yield with butyl acrylate in DMA (entry 3), and 93%
yield with styrene in acetonitrile (entry 4). Both reactions
also afforded high regioselectivities.
a Reaction conditions: 1.0 mmol of olefin, 2.0 mmol of boronic
acid, 2.0 mmol of NMM, 5.0 mL of DMA.
b Isolated yield.
c Determined by NMR, a/b = 1/99.
The high reactivity of both electron-poor 4a and 4c pro-
duced excellent yields (93% and 88%) after 24 h at 80 °C
(entry 1 and entry 3, Table 4) with high regioselectivity
(99%) at b-position. The electron-rich olefin (4d) gave
lower yield (68%) with high regioselectivity at a-position.
Surprisingly styrene (4b) only afforded low yield (36%) in
DMA and high yield (93%) in acetonitrile with slightly
lower regioselectivity.
In conclusion, we have demonstrated that 4,4¢-dimeth-
yl 2,2¢-bipyridine as ligand for Pd(II) catalysts was very ef-
ficient for oxidative Heck-type coupling reaction of aryl-
boronic acids with olefins in DMAor CH3CN under atm air
at 80 °C. The presence of chelated bipyridine ligand is in-
dispensable to achieve high reaction yields and to suppress
the formation of biphenyl as homocoupled byproduct. The
catalytic activity was found sensitive to both electronic and
steric effect of substituents on the 2,2¢-bipyridine. Elec-
tron-withdrawing groups and steric hindrance will retard
the reaction, while the electron-donating groups will en-
hance it. However, too strong electron-donating group such
as methoxy group will result in lower yield than moderate
electron-donating group such as methyl group.
A comparison is made in Table 5 on chelated biden-
tate 4,4¢-dimethyl 2,2¢-bipyridine and 2,9-dimethyl-1,10-
phenanthroline as ligand in Heck-type reaction. 2,9-di-
methyl-1,10-phenanthroline was reported as a superior
ligand in which the reaction was performed at room tem-
perature to give 81% yield and high regioselectivity in ace-

Bipyridine-Modulated Heck-type Reactions
J. Chin. Chem. Soc., Vol. 56, No. 5, 2009 877
Table 5. Comparison of 4,4¢-dimethyl 2,2¢-bipyridine and 2,9-dimethyl-1,10-phenanthroline
as ligand in Heck-type reaction
Entry 11d Entry 21d
Entry 3
Entry 4
Ligand
Olefin
N
N
N
N
N
N
N
N
OnBu
OnBu
Solvent
Base
Temperature
Time
CH3CN
NMM
RT
CH3CN
NMM
RT
DMA
CH3CN
NMM
80 °C
24 h
NMM
80 °C
24 h
24 h
24 h
Yield
81%
85%
96%
93%
a/b
0/100
15/85
1/99
5/95
EXPERIMENTAL
Pale yellow liquid; 1H NMR (300 MHz, CDCl3): d 7.68 (d,
J = 16.2 Hz, 1H, ArCH), 7.52-7.48 (m, 2H, Ar), 7.37-7.34
(m, 3H, Ar), 6.43 (d, J = 15.9 Hz, 1H, CHCO2Bu), 4.20 (t, J
= 6.6 Hz, 2H, CO2CH2CH2), 1.73-1.63 (m, 2H, CO2CH2CH2),
1.47-1.39 (m, 2H, CH2CH3), 0.96 (t, J = 7.4 Hz, 3H,
CH2CH3); 13C NMR (75 MHz, CDCl3): d 166.9, 144.4,
134.3, 130.0, 128.7, 127.9, 118.1, 64.2, 30.6, 19.0, 13.6.
4-Methoxy-trans-cinnamic acid n-butyl ester (3b)7
1H NMR (300 MHz) and 13C NMR (75 MHz) spectra
were recorded on a Bruker AVA-300 spectrometer with
TMS as internal standard. All reagents were used directly
as obtained commercially. All products are known.
Typical experimental procedure for the palladium-
catalyzed Heck-type cross-coupling reaction
Under an atmosphere of air, a mixture of Pd(OAc)2
(4.5 mg, 2.0 mmol%), bipyridine (2.4 mmol%), olefin (1.0
mmol), arylboronic acid (2.0 mmol), NMM (2.0 mmol) and
DMA (5.0 mL) were charged to a 25 mL round-buttom
flask and stirred at 80 °C for 24 h. After ordinary workup
and being evaporated by rotary evaporator, the residue was
purified by column chromatography to give the required
cross-coupled derivative (hexane/ethyl acetate).
Pale yellow liquid; 1H NMR (400 MHz, CDCl3): d 7.59 (d,
J = 15.9 Hz, 1H, ArCH), 7.42 (d, J = 8.8 Hz, 2H, Ar), 6.85
(d, J = 8.76 Hz, 2H, Ar), 6.27 (d, J = 15.9 Hz, 1H,
CHCO2Bu), 4.16 (t, J = 6.7 Hz, 2H, CO2CH2CH2), 3.77 (s,
3H, ArOCH3), 1.67-1.60 (m, 2H, CO2CH2CH2), 1.42-1.36
Trans-stilbene (5b)7
(m, 2H, CH2CH3), 0.92 (t, J = 7.4 Hz, 3H, CH2CH3); 13
C
NMR (100 MHz, CDCl3): d 167.3, 161.2, 144.1, 129.5,
127.1, 115.7, 114.2, 64.1, 55.2, 30.7, 19.1, 13.6.
4-Methyl-trans-cinnamic acid n-butyl ester (3c)7
1
White solid, mp = 121-124 °C; H NMR (400 MHz,
CDCl3): d 7.55 (d, J = 7.7 Hz, 4H, Ar), 7.38 (t, J = 7.4 Hz,
4H, Ar), 7.31-7.27 (m, 2H, Ar), 7.14 (s, 2H, ArCHCHAr);
13C NMR (100 MHz, CDCl3): d 137.3, 128.7, 128.6, 127.6,
126.
Pale yellow liquid; 1H NMR (300 MHz, CDCl3): d 7.65 (d,
J = 16.0 Hz, 1H, ArCH), 7.37 (d, J = 7.8 Hz, 2H, Ar), 7.13
(d, J = 7.8 Hz, 2H, Ar), 6.37 (d, J = 16.2 Hz, 1H,
CHCO2Bu), 4.18 (t, J = 6.6 Hz, 2H, CO2CH2CH2), 2.32 (s,
3H, ArCH3), 1.68-1.61 (m, 2H, CO2CH2CH2), 1.45-1.38
Trans-cinnamic acid n-butyl ester (3a)7

878 J. Chin. Chem. Soc., Vol. 56, No. 5, 2009
Hsu et al.
(m, 2H, CH2CH3), 0.95 (t, J = 7.5 Hz, 3H, CH2CH3); 13
C
Colourless liquid; 1H NMR (300 MHz, CDCl3): d 7.71 (d, J
= 16.2 Hz, 1H, ArCH), 7.64 (d, J = 7.8 Hz, 2H, Ar), 7.59 (d,
J = 7.8 Hz, 2H, Ar), 6.51 (d, J = 16.2 Hz, 1H, CHCO2Bu),
4.23 (t, J = 6.6 Hz, 2H, CO2CH2CH2), 1.73-1.65 (m, 2H,
CO2CH2CH2), 1.48-1.41 (m, 2H, CH2CH3), 0.97 (t, J = 7.5
Hz, 3H, CH2CH3); 13C NMR (75 MHz, CDCl3): d 166.3,
142.4, 137.7, 131.3, 127.9, 125.6, 121.8, 120.7, 64.5, 30.5,
19.0, 13.5.
NMR (75 MHz, CDCl3): d 166.9, 144.2, 140.2, 131.5,
129.3, 127.8, 116.9, 64.0, 30.6, 21.1, 19.0, 13.5.
2-Methyl-trans-cinnamic acid n-butyl ester (3d)6
4-Butyl-trans-cinnamic acid n-butyl ester (3h)9
Pale yellow liquid; 1H NMR (400 MHz, CDCl3): d 7.97 (d,
J = 15.9 Hz, 1H, ArCH), 7.54-7.52 (m, 1H, Ar), 7.27-7.16
(m, 3H, Ar), 6.35 (d, J = 15.9 Hz, 1H, CHCO2Bu), 4.21 (t, J
= 6.7 Hz, 2H, CO2CH2CH2), 2.42 (s, 3H, ArCH3),
1.72-1.65 (m, 2H, CO2CH2CH2), 1.48-1.39 (m, 2H,
CH2CH3), 0.96 (t, J = 7.4 Hz, 3H, CH2CH3); 13C NMR (100
MHz, CDCl3): d 167.0, 142.1, 137.5, 133.3, 130.6, 129.8,
126.3, 126.2, 119.2, 64.3, 30.7, 19.6, 19.1, 13.6.
Pale yellow liquid; 1H NMR (300 MHz, CDCl3): d 7.69 (d,
J = 16.2 Hz, 1H, ArCH), 7.46 (d, J = 7.8 Hz, 2H, Ar), 7.20
(d, J =7.8 Hz, 2H, Ar), 6.43 (d, J = 16.2 Hz, 1H,
CHCO2Bu), 4.23 (t, J = 6.6 Hz, 2H, CO2CH2CH2), 2.64 (t,
2H, ArCH2), 1.74-1.60 (m, 4H, CO2CH2CH2), 1.50-1.34
4-Acetyl-trans-cinnamic acid n-butyl ester (3e)7
(m, 4H, CH2CH3), 0.97 (t, J = 7.5 Hz, 3H, CH2CH3); 13
C
NMR (75 MHz, CDCl3): d 167.1, 145.4, 144.4, 131.8,
128.8, 127.9, 117.0, 64.1, 35.4, 33.2, 30.7, 22.2, 19.1, 13.8,
13.6.
Pale yellow liquid; 1H NMR (300 MHz, CDCl3): d 7.96 (d,
J = 8.1 Hz, 1H, ArCH), 7.68 (d, J = 16.2 Hz, 2H, Ar), 7.60
(d, J = 8.4 Hz, 2H, Ar), 6.53 (d, J = 16.2 Hz, 1H,
CHCO2Bu), 4.22 (t, J = 6.6 Hz, 2H, CO2CH2CH2), 2.61 (s,
3H, COCH3), 1.75-1.65 (m, 2H, CO2CH2CH2), 1.51-1.38
2-Methoxy-trans-cinnamic acid n-butyl ester (3i)5
(m, 2H, CH2CH3), 0.97 (t, J = 7.5 Hz, 3H, CH2CH3); 13
C
Pale yellow liquid; 1H NMR (300 MHz, CDCl3): d 7.99 (d,
J = 16.2 Hz, 1H, ArCH), 7.51-7.48 (m, 1H, Ar), 7.35-7.30
(m, 1H, Ar), 6.97-6.88 (m, 2H, Ar), 6.53 (d, J = 15.9 Hz,
1H, CHCO2Bu), 4.20 (t, J = 6.6 Hz, 2H, CO2CH2CH2),
3.81 (s, 3H, ArOCH3), 1.73-1.64 (m, 2H, CO2CH2CH2),
1.47-1.39 (m, 2H, CH2CH3), 0.96 (t, J = 7.4 Hz, 3H,
CH2CH3); 13C NMR (75 MHz, CDCl3): d 167.5, 158.2,
139.8, 131.3, 128.7, 123.3, 120.5, 118.6, 111.0, 64.1, 55.3,
30.7, 19.1, 13.6.
NMR (75 MHz, CDCl3): d 197.1, 166.4, 142.8, 138.6,
137.8, 128.7, 128.0, 120.6, 64.5, 30.6, 26.5, 19.0, 13.6.
Trans-4-fluoro-cinnamic acid n-butyl ester (3f)8
Pale yellow liquid; 1H NMR (300 MHz, CDCl3): d 7.63 (d,
J = 16.0 Hz, 1H, ArCH), 7.50 (dd, J = 8.6, 5.4 Hz, 2H, Ar),
7.05 (d, J = 8.6 Hz, 2H, Ar), 6.35 (d, J = 16.0 Hz, 1H,
CHCO2Bu), 4.20 (t, J = 6.7 Hz, 2H, CO2CH2CH2), 1.71-
1.63 (m, 2H, CO2CH2CH2), 1.47-1.39 (m, 2H, CH2CH3),
0.96 (t, J = 7.5 Hz, 3H, CH2CH3); 13C NMR (75 MHz,
CDCl3): d 166.0 (d, J = 103.3 Hz), 162.0, 143.0, 130.6,
129.7, 106.0 (d, J = 21.8 Hz), 64.3, 30.6, 19.0, 13.6.
4-Trifluormethyl-trans-cinnamic acid n-butyl ester
(3g)6
3-Nitro-trans-cinnamic acid n-butyl ester (3j)10
White solid, mp = 63-65 °C; 1H NMR (300 MHz, CDCl3): d
8.21 (d, J = 16.2 Hz, 2H, Ar), 7.70 (d, J = 16.2 Hz, 1H,
ArCH), 7.62 (d, J = 16.2 Hz, 2H, Ar), 6.57 (d, J = 15.9 Hz,
1H, CHCO2Bu), 4.23 (t, J = 6.6 Hz, 2H, CO2CH2CH2),

Bipyridine-Modulated Heck-type Reactions
J. Chin. Chem. Soc., Vol. 56, No. 5, 2009 879
1
1.73-1.66 (m, 2H, CO2CH2CH2), 1.49-1.41 (m, 2H,
CH2CH3), 0.97 (t, J = 7.4 Hz, 3H, CH2CH3); 13C NMR (75
MHz, CDCl3): d 165.9, 148.4, 141.4, 136.0, 133.4, 129.7,
124.2, 122.2, 121.2, 64.5, 30.5, 19.0, 13.5.
White solid, mp = 117-118 °C; H NMR (300 MHz,
CDCl3): d 8.03 (d, 2H, J = 7.5 Hz), 7.70 (t, 2H, J = 8.1 Hz),
6.78 (d, 2H, J = 8.3 Hz), 4.06 (s, 6H); 13C NMR (75 MHz,
CDCl3): d 163.3, 153.4, 139.1, 113.5, 110.8, 53.1.
4,4¢-Di(trifluoromethyl)-2,2¢-bypyridine (1f)14
(E)-N,N-dimethylcinnamamide (5c)11
Light yellow solid, mp = 78-80 °C; 1H NMR (300 MHz,
CDCl3): d 8.88 (d, J = 5.1 Hz, 2H), 8.73 (s, 2H), 7.58 (d, J =
3.9 Hz, 2H); 13C NMR (75 MHz, CDCl3): d 156.1, 150.3,
139.6 (d, J = 34.1 Hz), 124.6, 119.9 (d, J = 3.0 Hz), 117.1
(d, J = 3.3 Hz).
Pale yellow liquid; 1H NMR (300 MHz, CDCl3): d 7.67 (d,
J = 15.5 Hz, 1H, ArCH), 7.54-7.51 (m, 2H, Ar), 7.39-7.36
(m, 3H, Ar), 6.89 (d, J = 15.5 Hz, 1H, COCH), 3.16 (s, 3H,
CH3), 3.06 (s, 3H, CH3); 13C NMR (75 MHz, CDCl3): d
166.7, 142.3, 135.1, 129.4, 128.6, 127.6, 117.2, 37.3, 35.8.
N-(1-Phenylethenyl)-2-pyrrolidinone (5d)1d
ACKNOWLEDGMENT
We thank Soochow University for supporting this
work.
Received July 7, 2009.
REFERENCES
Colourless liquid; 1H NMR (300 MHz, CDCl3): d 7.34 (m,
2H, Ar), 7.17 (m, 3H, Ar), 5.42 (s, 1H, CCH2), 5.27 (s, 1H,
CCH2), 3.57 (dd, 2H, J = 7.0, J = 7.1 Hz), 2.53 (dd, 2H, J =
8.2, J = 7.9 Hz), 2.12-2.04 (m, 2H); 13C NMR (75 MHz,
CDCl3): d 173.8, 133.9, 130.5, 128.6, 127.6, 125.6, 49.7,
31.2, 20.5, 17.7.
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