Palladium-catalyzed heck reaction of aryl chlorides under mild conditions promoted by organic ionic bases

Article abstract of DOI:10.1021/jo201196a

An efficient Pd-catalyzed Heck reaction of aryl chlorides with olefins under mild conditions is described. High yields of products were achieved with n-Bu4N⁺OAc^- as base. Significantly, the temperature of the Heck reaction of diverse nonactivated aryl chlorides can be lowered to 80 °C. The new reaction system can also tolerate a wider range of olefins.

Full text of DOI:10.1021/jo201196a

NOTE
pubs.acs.org/joc
Palladium-Catalyzed Heck Reaction of Aryl Chlorides under Mild
Conditions Promoted by Organic Ionic Bases
Hua-Jian Xu,*,†,‡ Yong-Qiang Zhao,† and Xin-Feng Zhou†
†School of Medical Engineering and ‡Anhui Key Laboratory of Controllable Chemistry Reaction & Material Chemical Engineering,
Hefei University of Technology, Hefei 230009, P. R. China
S Supporting Information
b
ABSTRACT: An efficient Pd-catalyzed Heck reaction of aryl
chlorides with olefins under mild conditions is described. High
yields of products were achieved with n-Bu4N+OAcÀ as base.
Significantly, the temperature of the Heck reaction of diverse
nonactivated aryl chlorides can be lowered to 80 °C. The new reaction system can also tolerate a wider range of olefins.
he palladium-catalyzed Heck reaction of aryl/vinyl halides
with olefins is arguably one of the most important carbonÀ
to test the application of the organic ionic bases on the Heck
reactions. Herein, we reported an efficient palladium-catalyzed Heck
reaction of both unactivated and activated aryl chlorides promoted
by an organic ionic base n-Bu4N+OAcÀ (TBAE) under mild
conditions. In particular, our reaction temperature can now reach
80 °C for the coupling with unactivated aryl chlorides. To the best of
our knowledge, the reaction temperature of 80 °C is the lowest so far
reported Heck reaction of unactivated aryl chlorides (see the
Supporting Information for a compilation of recently described
reaction conditions).11 Moreover, because of the promotion of the
organic ionic base, the new reaction system can tolerate a wider
range of olefins as compared to many previously reported systems.
Initially, the reaction conditions were optimized starting from
chlorobenzene and styrene catalyzed by Pd(OAc)2 in 1,4-diox-
ane at 60 °C with various organic ionic bases under Ar as shown
in Table 1. It was observed that TBAE gave the best result in 60%
yield (Table 1, entries 1À4). Other solvents gave a lower yield
(Table 1, entries 5À8). To our surprise, 99% yield of the desired
product was obtained when the temperature was increased to
80 °C (Table 1, entry 10), but the yields only ranged from trace
to 29% when traditional inorganic bases were used at the same
temperature (Table 1, entries 11À13). Comparison of different
ligands and catalysts indicated that Dave-Phos was superior to
X-Phos and S-Phos (Table 1, entries 14À15) and Pd(OAc)2 was
superior to PdCl2 and Pd2(dba)3 (Table1, entries 16À17).
Optimization of the amount of TBAE and styrene showed that
an excess of TBAE (2.0 equiv) and styrene (1.5 equiv) (with
comparison of 1.0 equiv of aryl halides) are necessary to achieve
high yields (Table 1, entries 19 and 20). The reaction was also
sensitive to air (Table 1, entry 21).
T
carbon bond-forming processes in synthetic organic chemistry.1
Besides the standard aryl halides, various aryl sources such as aryl
triflates,2 diazonium salts,3 sulfonyl halides,4 aroyl halides,5 and
aromatic sulfinic acid sodium6 have been utilized, and highly
efficient catalytic systems have been developed. Because aryl
chlorides are more readily available and cheaper than other
substrates, more attention had been attracted to develop efficient
catalyst systems for the Heck reaction of aryl chlorides. Although
studies on Heck reaction of both activated aryl chlorides7 and
unactivated aryl chlorides8 have made significant progress in the
past few years, most of these catalytic systems for Heck reaction
of unactivated aryl chlorides require relatively harsh conditions
(T > 100 °C). Moreover, these reactions are inefficient for the
reaction of some aryl chlorides (e.g., 4-chlorobenzaldehyde) with
unactivated olefins (e.g., 1,1-disubstituted olefins, 1,2-disubsti-
tuted olefins, and alkyl monosubstituted alkenes). Therefore,
there is still a need to explore milder and more efficient catalyst
systems to improve the scope and utility of the Heck coupling
reaction of the aryl chloride substrates.
In 2009, Liu et al. reported that Cu-catalyzed carbonÀnitrogen
cross-couplings of aryl iodides and aryl bromides could be promoted
by organic ionic bases at room temperature.9 These organic ionic
bases are composed of tetraalkylammonium or tetraalkylphospho-
nium cations and basic anions (e.g., n-Bu4N+OAcÀ). In comparison
to the traditionally used inorganic bases (e.g., K3PO4 and Cs2CO3),
the organic ionic bases have good solubility and are fully ionized in
organic solvents. Therefore, they can show much better perfor-
mance as compared to the inorganic bases in the transformations
carried out in organic solvents. In this context, it should be noted
that the choice of base has been found to have a crucial effect on the
rate and the yield of Heck reaction.8c,f The reason is that reductive
elimination of hydrogen halide from the Pd(II) center is the last step
in the Heck reaction catalytic cycle to regenerate the Pd(0)
catalyst.10 This step is promoted by the base, and that is why a base
must be used in the Heck coupling reaction. As a result, we decided
To explore the scope of the catalytic system, the reaction of
different aryl chlorides with styrene were carried out under
optimized conditions (2 mol % of Pd(OAc)2, 6 mol % of
Dave-Phos, 2 equiv of TBAE, 1,4-dioxane, 80 °C), and the
Received: June 15, 2011
Published: August 30, 2011
r
2011 American Chemical Society
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|

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NOTE
Table 1. Optimization of the Reaction Conditionsa
Table 2. Heck Couplings of Different Aryl Chlorides with
Styrenea
a Unless otherwise noted, the reactions were carried out with chlor-
obenzene (0.5 mmol), styrene (0.75 mmol), base (2.0 equiv), catalyst
(2 mol %), ligand (6 mol %), and solvent (1 mL) under Ar for 24 h.
b Determined by GC. c 1 mol % of Pd(OAc)2 and 3 mol % of Dave-Phos
e
were used. d With 1.5 equiv of TBAE. 1.2 equiv of styrene was used.
f Under air. TBPE = tetrabutylphosphonium acetate, TBPM = tetra-
butylphosphonium malonate, TBAP = tetrabutylammonium phosphate,
Cy = cyclohexyl.
a Reactions were carried out using Ar-Cl (0.5 mmol) and styrene
(0.75 mmol) at 80 °C under Ar for 24 h. b Yields are given for isolated
products. c At 100 °C, 48 h.
results were summarized in Table 2. It was observed that the
couplings of activated aryl chlorides with styrene proceeded
in excellent yields. The examples include 1-chloro-4-nitro-
benzene, 4-chlorobenzonitrile, and 4-chlorobenzaldehyde
(3aÀc). Even sterically hindered substrates such as 2-chloro-
benzaldehyde were also successfully coupled in excellent
yields (3d), although a higher temperature and a longer reaction
time were required. However, the reaction of 4-chlorobenzyl
cyanide, 4-chloroacetophenone, and 4-chlorobenzotrifluoride with
styrene only gave moderate yields (3eÀg). Interestingly, reactions
of unactivated aryl chlorides bearing a methyl or methoxy group
with styrene gave higher yields than activated aryl chlorides (3iÀk).
The reactions of different alkenes with 4-chlorobenzaldehyde
were subsequently investigated. It was clear that the reactions
of methyl-, ethyl-, n-butyl, and tert-butyl acrylate with 4-chloro-
benzaldehyde all gave the desired products in excellent yields
(3lÀo) in Table 3. Even styrene derivatives also reacted nicely
with 4-chlorobenzaldehyde. For example, 4-methystyrene and
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NOTE
Table 3. Heck Couplings of 4-Chlorobenzaldehyde with
chlorides can be lowered to 80 °C, and 4-chlorobenzaldehyde
can also react with various olefins to give desired products with
high yields.
Different Olefinsa
’ EXPERIMENTAL SECTION
Experimental Procedures for Preparing Organic Ionic
Bases.9a Tetrabutylphosphonium Malonate (TBPM). A half-equimo-
lar quantity of malonic acid was allowed to react with aqueous tetra-
n-alkylphosphonium hydroxide (40%) in water by stirring for 3 h under
a nitrogen atmosphere. Dry salts were obtained after evaporation of the
solvent and finally dried in vacuo at least 24 h at 50 °C without further
purification. The sample was sealed in a vessel under N2 atmosphere: 1H
NMR (300 MHz, D2O) δ 3.00 (s, 2H), 2.27À1.86 (m, 16H), 1.66À1.15
(m, 32H), 0.82 (t, J = 7.2 Hz, 24H); 13C NMR (75 MHz, D2O) δ 177.1,
47.6, 23.3 (d, J = 15.2 Hz), 22.7 (d, J = 4.4 Hz), 17.3 (d, J = 48.2
Hz), 12.6.
Tetrabutylammonium Phosphate (TBAP). Phosphoric acid (85%)
(3.7028 g, 0.0321 mol) was allowed to react with aqueous tetrabutyl-
ammonium hydroxide (25%) (100 g, 0.0964 mol) in water by stirring
for 3 h under a nitrogen atmosphere. A white solid was obtained by
lyophilization. The product was dried in vacuo for at least 24 h at 30 °C
without further purification. The sample was sealed off in a vessel under
1
N2 atmosphere: H NMR (300 MHz, D2O) δ 3.15À3.10 (m, 24H),
1.63À1.53 (m, 24H), 1.35À1.23 (m, 24H), 0.90À0.85 (t, J = 7.3 Hz,
36H); 13C NMR (75 MHz, D2O, δ ppm) δ 58.1, 23.1, 19.1, 12.8.
Tetrabutylammonium Acetate (TBAE). KOAc (17.6562 g, 0.1800
mol) was allowed to react with tetrabutylammonium chloride (50 g,
0.1800 mol) in methanol (200 mL) by stirring for 1 day under a nitrogen
atmosphere and then passed through a fritted glass filter to remove the
inorganic salts (KCl) generated by the ion-exchange reaction. A white
solid was obtained by drying in vacuo for at least 24 h at 30 °C without
further purification. The sample was sealed off in a vessel under N2
1
atmosphere: H NMR (300 MHz, D2O) δ 3.20À2.83 (m, 8H), 1.80
(s, 3H), 1.54 (dt, J = 15.7, 7.9 Hz, 8H), 1.35À1.09 (m, 8H), 0.84 (t, J = 7.3
Hz, 12H); 13C NMR (75 MHz, D2O) δ 181.1, 58.1, 48.8, 23.1,
19.1, 12.8.
General Procedure for Heck Coupling of Different Aryl
Chlorides with Styrene (A). After standard cycles of evacuation
and backfilling with dry and pure argon, an oven-dried Schlenk tube
equipped with a magnetic stirring bar was charged with Pd(OAc)2
(2 mol %, 2.2 mg), Dave-Phos (6 mol %, 11.8 mg), the aryl chlorides if a
solid (0.5 mmol, 1 equiv), and TBAE (1 mmol, 0.301 g). The tube was
evacuated and backfilled with argon (this procedure was repeated three
times). Under a counter flow of argon, styrene (0.75 mmol, 86 μL), aryl
chlorides (if liquid), and 1,4-dioxane (1.0 mL) were added by syringe.
The tube was sealed, and the mixture was allowed to stir under argon at
80 °C for 24 h. Upon completion of the reaction, the mixture was diluted
with ethyl acetate and filtered through silica gel (which was rinsed with
EtOAc), and solvent was removed with the aid of a rotary evaporator.
The residue was purified by column chromatography on silica gel and
the product was dried under high vacuum for at least 0.5 h.
General Procedure for Heck Coupling of 4-Chlorobenzal-
dehyde with Different Olefins (B). After standard cycles of
evacuation and backfilling with dry and pure argon, an oven-dried
Schlenk tube equipped with a magnetic stirring bar was charged with
Pd(OAc)2 (2 mol %, 2.2 mg), Dave-Phos (6 mol %, 11.8 mg),
4-chlorobenzaldehyde (0.5 mmol, 70.3 mg), and TBAE (1 mmol,
0.301 g). The tube was evacuated and backfilled with argon (this
procedure was repeated three times). Under a counter flow of argon,
olefins (0.75 mmol) and 1,4-dioxane (1.0 mL) were added by syringe.
The tube was sealed, and the mixture was allowed to stir under argon at
80 °C for 24 h. Upon completion of the reaction, the mixture was diluted
with ethyl acetate and filtered through silica gel (which was rinsed with
a Reactions were carried out using 4-chlorobenzaldehyde (0.5 mmol)
and olefins (0.75 mmol) at 80 °C under Ar for 24 h. b Yields are given for
isolated products. c At 100 °C, 48 h.
4-flourostyrene, respectively, gave the corresponding products
in 94% and 95% yield (3pÀq).
Note that alkyl-substituted terminal olefins are usually found
to have low reactivity in the documented Heck reactions.8j,12
However, it is gratifying that high reactivity was also observed for
the coupling of octene with 4-chlorobenzaldehyde (Table 3,
entry 7) in our newly developed protocol. Furthermore, 1,1-
disubstituted and 1,2-disubstituted olefins also gave moderate
yields in this catalytic system (3s,t).
In summary, we have developed an efficient protocol for the
Heck reaction of various aryl chlorides with a wide range of ole-
fins promoted by TBAE under mild conditions. TBAE was
shown to play an important role in these processes. High yields
were achieved with the organic ionic base. Significantly, the
reaction temperature of Heck reaction of unactivated aryl
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NOTE
EtOAc), and solvent was removed with the aid of a rotary evaporator.
The residue was purified by column chromatography on silica gel, and
the product was dried under high vacuum for at least 0.5 h.
(E)-Stilbene (3h).13 Following general procedure A, chlorobenzene
(0.5 mmol, 52 μL) was allowed to react with styene (0.75 mmol) for
24 h. The product was isolated as a white solid (89 mg, 99% yield). Spectral
data matched the literature description: mp 123.9À124.6 °C; 1H NMR
(400 MHz, CDCl) δ 7.51 (d, J = 7.2 Hz, 4H), 7.37À7.33 (m, 4H),
7.27À7.22 (m, 2H), 7.10 (s, 2H); 13C NMR (101 MHz, CDCl3) δ
137.4, 128.8, 128.7, 127.7, 126.6; EI-MS m/z = 180 (M+).
(E)-4-Nitrostilbene (3a).13 Following general procedure A, 1-chloro-
4-nitrobenzene (0.5 mmol, 78.8 mg) was allowed to react with styene
(0.75 mmol, 86 μL) for 24 h. The product was isolated as a yellow
solid (111 mg, 98% yield): mp 154.2À155.0 °C; 1H NMR (400 MHz,
CDCl3) δ 8.20 (d, J = 8.8 Hz, 2H), 7.60 (d, J = 8.8 Hz, 2H), 7.54 (d, J =
7.3 Hz, 2H), 7.41À7.37 (m, 2H), 7.34À7.32 (m, 1H), 7.25 (d, J = 16.3
Hz, 1H), 7.12 (d, J = 16.3 Hz, 1H); 13C NMR (101 MHz, CDCl3) δ
146.7, 143.8, 136.2, 133.3, 128.9, 128.8, 127.0, 126.8, 126.3, 124.1; EI-
MS m/z = 225 (M+).
(E)-4-Methylstilbene (3i).17 Following general procedure A, 4-methyl-
chlorobenzene (0.5 mmol, 59 μL) was allowed to react with styene
(0.75 mmol, 86 μL) for 24 h. The product was isolated as a white solid
(96 mg, 99% yield). Spectral data matched the literature description:
mp 121.7À122.3 °C; 1H NMR (400 MHz, CDCl3) δ 7.48 (d, J = 7.4
Hz, 2H), 7.39 (d, J = 8.0 Hz, 2H), 7.33 (t, J = 7.6 Hz, 2H), 7.24À7.20
(m, 1H), 7.14 (d, J = 7.9 Hz, 2H), 7.08 (d, J = 16.5 Hz, 1H), 7.03 (d,
J = 16.4 Hz, 1H), 2.34 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 137.6,
137.6, 134.6, 129.5, 128.7, 127.8, 127.5, 126.5, 126.5, 21.3; EI-MS m/z =
194 (M+).
(E)-4-Styrylbenzonitrile (3b).14 Following general procedure A,
4-chlorobenzonitrile (0.5 mmol, 68.8 mg) was allowed to react with
styene (0.75 mmol, 86 μL) for 24 h. The product was isolated as a white
solid (101 mg, 98% yield): mp 114.9À115.2 °C; 1H NMR (400 MHz,
CDCl3) δ 7.51À7.49 (m, 2H), 7.45À7.41 (m, 4H), 7.28 (t, J = 7.4 Hz,
1H), 7.24À7.18 (m, 1H), 7.09 (d, J = 16.3 Hz, 1H), 6.96 (d, J = 16.3 Hz,
1H); 13C NMR (101 MHz, CDCl3) δ 141.9, 136.3, 132.5, 132.4, 128.9,
128.7, 127.0, 126.9, 126.7, 119.1, 110.6; EI-MS m/z = 205 (M+).
(E)-4-Formylstilbene (3c).14 Following general procedure A, 4-chloro-
benzaldehyde (0.5 mmol, 70.3 mg) was allowed to react with styene
(0.75 mmol, 86 μL) for 24 h. The product was isolated as a white solid
(96 mg, 92% yield): mp 116.0À116.8 °C; 1H NMR (400 MHz, CDCl3)
δ 9.97 (s, 1H), 7.85 (d, J = 8.3 Hz, 2H), 7.63 (d, J = 8.3 Hz, 2H), 7.53 (d,
J = 7.2 Hz, 2H), 7.38 (t, J = 7.4 Hz, 2H), 7.32À7.28 (m, 1H), 7.24 (d,
qJ = 16.3 Hz, 1H), 7.12 (d, J = 16.3 Hz, 1H); 13C NMR (101 MHz,
CDCl3) δ 191.7, 143.4, 136.6, 135.3, 132.2, 130.3, 128.9, 128.6, 127.4,
126.9; EI-MS m/z = 208 (M+).
(E)-4-Methoxystilbene (3j).17 Following general procedure A,
4-chloroanisole (0.5 mmol, 62 μL) was allowed to react with styene
(0.75 mmol, 86 μL) for 24 h. The product was isolated as a white solid
(100 mg, 95% yield): mp 135.3À135.9 °C; 1H NMR (400 MHz,
CDCl3) δ 7.49À7.43 (m, 4H), 7.33 (t, J = 7.6 Hz, 2H), 7.24À7.20
(m, 1H), 7.06 (d, J = 16.3 Hz, 1H), 6.96 (d, J = 16.3 Hz, 1H), 6.89 (d, J =
8.8 Hz, 2H), 3.81 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 159.4, 137.7,
130.2, 128.7, 128.3, 127.8, 127.3, 126.7, 126.3, 114.2, 55.4; EI-MS m/z =
210 (M+).
(E)-3-Methoxystilbene (3k).17 Following general procedure A,
3-chloroanisole (0.5 mmol, 61 μL) was allowed to react with styene
(0.75 mmol, 86 μL) for 24 h. The product was isolated as a white solid
(100 mg, 95% yield): mp 31.3À32.9 °C; 1H NMR (300 MHz, CDCl3) δ
7.43 (d, J = 7.3 Hz, 2H), 7.27 (t, J = 7.4 Hz, 2H), 7.22À7.16 (m, 2H),
7.04À6.97 (m, 4H), 6.74 (d, J = 10.1 Hz, 1H), 3.76 (s, 3H); 13C NMR
(75 MHz, CDCl3) δ 160.0, 138.8, 137.3, 129.7, 129.1, 129.7, 128.7,
127.7, 126.6, 119.3, 113.4, 111.8, 55.3; EI-MS m/z = 210 (M+).
(E)-Methyl-3-(4-formylphenyl)acrylate (3l).18 Following general
procedure B, 4-chlorobenzaldehyde (0.5 mmol, 70.3 mg) was allowed
to react with methyl acrylate (0.75 mmol, 68 μL) for 24 h. The product
was isolated as a yellow solid (89.4 mg, 94% yield): mp 82.7À83.5 °C;
1H NMR (400 MHz, CDCl3) δ 10.03 (s, 1H), 7.90 (d, J = 8.0 Hz, 2H),
7.74À7.66 (m, 3H), 6.55 (d, J = 16.0 Hz, 1H), 3.83 (s, 3H); 13C NMR
(101 MHz, CDCl3) δ 191.4, 166.8, 143.1, 140.0, 137.2, 130.1, 128.5,
121.0, 51.9; EI-MS m/z = 190 (M+).
(E)-2-Formylstilbene (3d).15 Followinggeneral procedure A, 2-chloro-
benzaldehyde (0.5 mmol, 70.3 mg) was allowed to react with styene
(0.75 mmol, 86 μL) for 48 h. The product was isolated as yellow oil (100
mg, 95% yield): 1H NMR (400 MHz, CDCl3) δ 10.30 (s, 1H), 8.03 (d,
qqJ = 16.2 Hz, 1H), 7.81 (d, J = 8.7 Hz, 1H), 7.69 (d, J = 7.8 Hz, 1H),
7.57À7.54 (m, 3H), 7.42À7.35 (m, 3H), 7.27À7.30 (m, 1H), 7.03 (d,
J = 16.2 Hz, 1H); 13C NMR (101 MHz, CDCl3) δ 192.7, 140.0, 137.0,
134.0, 133.7, 133.0, 132.4, 128.8, 128.4, 127.7, 127.2, 127.0, 124.8;
EI-MS m/z = 208 (M+).
(E)-2-(4-Styrylphenyl)acetonitrile (3e).16 Following general proce-
dure A, 4-chlorobenzyl cyanide (0.5 mmol, 64 μL) was allowed to react
with styene (0.75 mmol, 86 μL) for 48 h. The product was isolated as a
1
white solid (44 mg, 40% yield): mp 121.6À122.5 °C; H NMR (400
MHz, CDCl3) δ 7.53À7.50 (m, 4H), 7.36 (t, J = 7.5 Hz, 2H), 7.32À7.25
(m, 3H), 7.10 (m, 2H), 3.75 (s, 2H); 13C NMR (101 MHz, CDCl3) δ
137.3, 137.0, 129.6, 129.0, 128.8, 128.3, 127.9, 127.6, 127.2, 126.6, 117.8,
23.4; EI-MS m/z = 219 (M+).
(E)-Ethyl-3-(4-formylphenyl)acrylate (3m).19 Following general pro-
cedure B, 4-chlorobenzaldehyde (0.5 mmol, 70.3 mg) was allowed to
react with ethyl acrylate (0.75 mmol, 82 μL) for 24 h. The product was
1
isolated as a yellow solid (91 mg, 89% yield): mp 39.4À40.1 °C; H
(E)-4-Acetylstilbene (3f).8i Following general procedure A, 4-chloro-
acetophenone (0.5 mmol, 64 μL) was allowed to react with styene
(0.75 mmol, 86 μL) for 24 h. The product was isolated as a white solid
(82 mg, 74% yield): mp 141.3À142.0 °C; 1H NMR (400 MHz, CDCl3)
δ 7.96 (d, J = 8.4 Hz, 2H), 7.59 (d, J = 8.3 Hz, 2H), 7.55 (d, J = 7.4 Hz,
2H), 7.39 (t, J = 7.5 Hz, 2H), 7.32À7.29 (m, 1H), 7.24 (d, J = 16.5 Hz,
1H), 7.13 (d, J = 16.3 Hz, 1H), 2.61 (s, 3H); 13C NMR (101 MHz,
CDCl3) δ 197.4, 142.0, 136.7, 136.0, 131.5, 128.9, 128.8, 128.3, 127.5,
126.8, 126.5, 26.6; EI-MS m/z = 222 (M+)
NMR (400 MHz, CDCl3) δ 10.02 (s, 1H), 7.89 (d, J = 7.3 Hz, 2H),
7.71À7.66 (m, 3H), 6.54 (d, J = 16.1 Hz, 1H), 4.28 (q, J = 7.1 Hz, 2H),
1.35 (t, J = 7.1 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ 191.3, 166.2,
142.7, 140.1, 137.1, 130.1, 128.4, 121.4, 60.8, 14.2; EI-MS m/z = 204
(M+).
(E)-n-Butyl-3-(4-formylphenyl)acrylate (3n).14 Following general
procedure B, 4-chlorobenzaldehyde (0.5 mmol, 70.3 mg) was allowed
to react with n-butyl acrylate (0.75 mmol, 108 μL) for 24 h. The product
was isolated as a yellow solid (111 mg, 96% yield): mp 35.2À36.0 °C; 1H
NMR (400 MHz, CDCl3) δ 10.03 (s, 1H), 7.90 (d, J = 8.1 Hz, 2H),
7.72À7.67 (m, 3H), 6.56 (d, J = 16.1 Hz, 1H), 4.23 (t, J = 6.7 Hz, 2H),
(E)-1-Styryl-4-(trifluoromethyl)benzene (3g).9b Following general
procedure A, 4-chlorobenzotrifluoride (0.5 mmol, 66.8 μL) was allowed
to react with styene (0.75 mmol, 86 μL) for 24 h. The product was
isolated as a white solid (68 mg, 55% yield): mp 132.1À133.4 °C; 1H
NMR (400 MHz, CDCl3) δ 7.61À7.56 (m, 4H), 7.52 (d, J = 7.4 Hz,
2H), 7.37 (t, J = 7.5 Hz, 2H), 7.29 (t, J = 7.3 Hz, 1H), 7.18 (d, J = 16.4 Hz,
1H), 7.10 (d, J = 16.3 Hz, 1H); 13C NMR (101 MHz, CDCl3) δ 140.9,
136.7, 131.2, 129.5, 129.1, 128.8, 128.3, 127.2, 126.7, 126.8, 125.7 (q, 3J
(C, F) = 3.7 Hz), 123.0; EI-MS m/z = 248 (M+).
1.74À1.67 (m, 2H), 1.49À1.40 (m, 2H), 0.97 (t, J = 7.4 Hz, 3H); 13
C
NMR (101 MHz, CDCl3) δ 191.4, 166.4, 142.8, 140.1, 137.1, 130.1,
128.5, 121.5, 64.7, 30.7, 19.2, 13.7; EI-MS m/z = 232 (M+).
(E)-tert-Butyl-3-(4-formylphenyl)acrylate (3o).20 Following general
procedure B, 4-chlorobenzaldehyde (0.5 mmol, 70.3 mg) was allowed to
react with tert-butyl acrylate (0.75 mmol, 109 μL) for 24 h. The product
was isolated as a blue solid (99 mg, 85% yield): mp 108.7À109.5 °C; 1H
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NOTE
NMR (400 MHz, CDCl3) δ 10.02 (s, 1H), 7.89 (d, J = 8.2 Hz, 2H),
7.67À7.59 (m, 3H), 6.48 (d, J = 16.0 Hz, 1H), 1.55 (s, 9H); 13C NMR
(101 MHz, CDCl3) δ 191.4, 165.6, 141.8, 140.4, 137.0, 130.1, 128.4,
123.4, 81.0, 28.1; EI-MS m/z = 232 (M+).
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: hjxu@hfut.edu.cn.
(E)-4-(4-Methylstyryl)benzaldehyde (3p).21 Following general pro-
cedure B, 4-chlorobenzaldehyde (0.5 mmol, 70.3 mg) was allowed to
react with 4-methylphenylene (0.75 mmol, 98 μL) for 24 h. The product
was isolated as a yellow solid (105 mg, 94% yield): mp 182.1À182.8 °C;
1H NMR (400 MHz, CDCl3) δ 9.98 (s, 1H), 7.85 (d, J = 6.8 Hz, 2H),
7.62 (d, J = 8.3 Hz, 2H), 7.43 (d, J = 8.1 Hz, 2H), 7.25À7.18 (m, 3H),
7.08 (d, J = 16.3 Hz, 1H), 2.37 (s, 3H); 13C NMR (101 MHz, CDCl3) δ
191.6, 143.7, 138.6, 135.2, 133.8, 132.2, 130.2, 129.6, 126.9, 126.8, 126.4,
21.0; EI-MS m/z = 222 (M+).
’ ACKNOWLEDGMENT
We gratefully acknowledge financial support from the National
Natural Science Foundation of China (Nos. 20802015, 21072040,
and 21071040).
’ REFERENCES
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(E)-4-(4-Fluorostyryl)benzaldehyde (3q).22 Following general pro-
cedure B, 4-chlorobenzaldehyde (0.5 mmol, 70.3 mg) was allowed to
react with 4-fluorophenylene (0.75 mmol, 89 μL) for 24 h. The product
was isolated as a yellow solid (103 mg, 95% yield): mp 119.9À120.6 °C;
1H NMR (400 MHz, CDCl3) δ 9.99 (s, 1H), 7.86 (d, J = 8.2 Hz, 2H),
7.63 (d, J = 8.2 Hz, 2H), 7.51 (dd, J = 8.6, 5.4 Hz, 2H), 7.21 (d, J = 16.3
Hz, 1H), 7.10 À 7.02 (m, 3H); 13C NMR (101 MHz, CDCl3) δ 191.6,
162.8, (d, 1J (C, F) = 248.8 Hz), 143.3, 135.4, 132.8, 132.8, 130.9, 130.3,
128.5, 128.5, 127.1, 127.1, 126.9, 116.0, 115.8; EI-MS m/z = 226 (M+).
(E)-4-(Oct-1-enyl)benzaldehyde (3r).23 Following general procedure
B, 4-chlorobenzaldehyde (0.5 mmol, 70.3 mg) was allowed to react with
1-octene (0.75 mmol, 118 μL) for 24 h. The product was isolated as
liquid (97 mg, 90% yield): 1H NMR (400 MHz, CDCl3) δ 9.94 (s, 1H),
7.79 (d, J = 8.3 Hz, 2H), 7.46 (d, J = 8.3 Hz, 2H), 6.42À6.40 (m, 2H),
2.24 (dd, J = 11.6, 8.3 Hz, 2H), 1.52À1.44(m, 2H), 1.34À1.26 (m, 6H),
0.89 (t, J = 6.6 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ 190.6, 143.1,
134.4, 133.9, 129.1, 127.9, 125.7, 125.3, 32.2, 30.7, 28.1, 27.9, 21.6, 13.1;
EI-MS m/z = 216 (M+).
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(E)-Methyl-3-(4-formylphenyl)-2-methylacrylate (3s).7h Following
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1
41.2À42.0 °C; H NMR (400 MHz, CDCl3) δ 10.03 (s, 1H), 7.91
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(d, J = 8.1 Hz, 2H), 7.71 (s, 1H), 7.54 (d, J = 8.1 Hz, 2H), 3.84 (s, 3H),
2.13 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 190.6, 167.6, 140.9, 136.4,
134.7, 130.0, 129.0, 128.7, 51.3, 13.2; EI-MS m/z = 204 (M+).
(E)-Butyl-3-(4-formylphenyl)-2-methylacrylate (3t).24 Following
general procedure B, 4-chlorobenzaldehyde (0.5 mmol, 70.3 mg) was
allowed to react with n-butyl methacrylate (0.75 mmol, 120 μL) for 24 h.
The product was isolated as a yellow liquid (63 mg, 51% yield): 1H NMR
(300 MHz, CDCl3) δ 10.02 (s, 1H), 7.90 (d, J = 8.0 Hz, 2H), 7.69 (s,
1H), 7.54 (d, J = 7.9 Hz, 2H), 4.23 (t, J = 6.6 Hz, 2H), 2.12 (s, 3H),
1.76À1.67 (m, 2H), 1.51À1.39 (m, 2H), 0.97 (t, J = 7.3 Hz, 2H); 13C
NMR (75 MHz, CDCl3) δ 191.6, 168.2, 142.1, 137.1, 135.6, 131.4,
130.1, 129.7, 126.9, 65.1, 30.7, 19.3, 14.2, 13.8; EI-MS m/z = 246 (M+).
(E)-Ethyl-3-(4-formylphenyl)-3-phenylacrylate (3u).25 Following
general procedure B, 4-chlorobenzaldehyde (0.5 mmol, 70.3 mg) was
allowed to react with ethyl cinnamate (0.75 mmol, 126 μL) for 48 h. The
product was isolated as yellow liquid (98 mg, 70% yield): 1H NMR (300
MHz, CDCl3) δ 10.03 (s, 1H), 7.84 (d, J = 8.2 Hz, 2H), 7.48À7.40 (m,
5H), 7.22 (d, J = 2.2 Hz, 2H), 6.43 (s, 1H), 4.07 (q, J = 7.1 Hz, 2H), 1.12
(t, J = 7.1 Hz, 3H); 13C NMR (75 MHz, CDCl3) δ 191.7, 165.7, 154.8,
146.7, 138.2, 136.6, 129.7, 129.1, 128.9, 128.5, 128.1, 119.9, 60.4, 14.0;
EI-MS m/z = 280 (M+).
(11) See the Supporting Information.
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’ ASSOCIATED CONTENT
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S
Supporting Information. References reported of chloro-
b
benzene with styrene and copies of H and 13C NMR spectra
for the products. This material is available free of charge via the
Internet at http://pubs.acs.org.
1
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The Journal of Organic Chemistry
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