N-heterocyclic carbene-palladium(II)-1-methylimidazole complex-catalyzed Suzuki-Miyaura coupling of aryl sulfonates with arylboronic acids

Article abstract of DOI:10.1021/jo301270t

A well-defined NHC-Pd(II)-Im complex 1 was found to be an effective catalyst for the Suzuki-Miyaura coupling of aryl sulfonates including tosylates and phenylsulfonates with arylboronic acids, giving the desired coupling products in good to high yields. Acceptable yields can also be achieved even by using the less reactive mesylates as the substrates. It is worthy of noting here that this is the first example of NHC-Pd(II) complex-catalyzed Suzuki-Miyaura coupling of aryl sulfonates with arylboronic acids, enriching an inexpensive, convenient, and alternative method for the synthesis of biaryl compounds.

Full text of DOI:10.1021/jo301270t

Article
pubs.acs.org/joc
N‑Heterocyclic Carbene−Palladium(II)−1-Methylimidazole Complex-
Catalyzed Suzuki−Miyaura Coupling of Aryl Sulfonates with
Arylboronic Acids
Zhan-Yong Wang, Gao-Qi Chen, and Li-Xiong Shao*
College of Chemistry and Materials Engineering, Wenzhou University, Chashan University Town, Wenzhou, Zhejiang Province
325035, People’s Republic of China
S
* Supporting Information
ABSTRACT: A well-defined NHC−Pd(II)−Im complex 1 was found to be an
effective catalyst for the Suzuki−Miyaura coupling of aryl sulfonates including
tosylates and phenylsulfonates with arylboronic acids, giving the desired coupling
products in good to high yields. Acceptable yields can also be achieved even by
using the less reactive mesylates as the substrates. It is worthy of noting here that
this is the first example of NHC−Pd(II) complex-catalyzed Suzuki−Miyaura
coupling of aryl sulfonates with arylboronic acids, enriching an inexpensive,
convenient, and alternative method for the synthesis of biaryl compounds.
On the other hand, during the past two decades, N-
heterocyclic carbenes (NHCs) and their metal complexes,
usually with higher air and thermal stability, have become a big
challenge to phosphine−metal complexes since most phos-
phine ligands and their metal complexes are air-, thermal-, and/
or moisture-sensitive.6 However, in sharp contrast to the
abundant reports of NHC−metal complex-catalyzed Suzuki−
Miyaura coupling reactions of aryl halides,7 their applications
using aryl sulfonates as the partners are still limited and the
known methods involve complicated synthetic routes for the
NHC−metal catalysts.8 Therefore, there still remains much
room for improving the phosphine-free Suzuki−Miyaura
coupling of aryl sulfonates with arylboronic acids, especially
with respect to the easy availability of the metal complexes,
stability of the ligands, high catalytic activity of the complexes,
and substrate scope of the method.
INTRODUCTION
■
Transition-metal-catalyzed coupling reactions have been proven
to be versatile methods for the formation of carbon−carbon
bonds.1 Among them, the Suzuki−Miyaura coupling is
unarguably one of the most practical methods.2 Among the
electrophiles used in the transition-metal-catalyzed Suzuki−
Miyaura coupling reactions, aryl sulfonates are a class of
interesting and practical alternatives to aryl halides and triflates
because they can be readily prepared from cheap, commercially
available phenols and sulfonyl chlorides.3 In addition, aryl
sulfonates are more easily handled and usually less expensive
than the corresponding aryl triflates. However, aryl sulfonates
are generally less reactive in the metal-catalyzed coupling
reactions than the corresponding aryl chlorides and triflates,
and thus, much harsher reaction conditions have to be adopted
accordingly.4 For instance, to achieve an efficient Pd-catalyzed
Suzuki−Miyaura coupling reaction using aryl sulfonates as the
substrates, the expensive, less available, and air-sensitive
sterically hindered, electron-rich phosphine ligands have to be
employed to facilitate the corresponding transformations.3a−f In
the Ni-catalyzed transformations, usually high loadings of the
catalyst [1−10 mol % of Ni(0) or Ni(II)] and ancillary
phosphine ligands are mandatory for the successful cou-
plings.3g−r To overcome the drawbacks of using air-sensitive
and cost-expensive phosphine ligands, the most straightforward
way is to develop phosphine ligand-free methods. In 2011,
Recently, we found that N-heterocyclic carbene−palladium-
(II)−1-methylimidazole [NHC-Pd(II)-Im] complex 1 (Figure
1), easily prepared from commercially available PdCl2, 1-
methylimidazole, and IPr·HCl [1,3-bis(2,6-diisopropylphenyl)-
imidazolium chloride] in a one-step process in very high yield,
́
Alonso and Najera reported an oxime-derived palladacycle-
catalyzed phosphine-free Suzuki−Miyaura coupling of aryl
imidazolesulfonates with arylboronic acids and potassium
aryltrifluoroborates.5 However, this method uses the not readily
available oxime palladacycle catalyst and aryl imidazolesulfo-
nates, which were obtained by lengthy procedures. In addition,
this method is only limited to the more reactive, electron-
deficient aryl sulfonates such as aryl imidazolesulfonates.
Figure 1. NHC−Pd(II)−Im complex 1.
Received: June 18, 2012
© XXXX American Chemical Society
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was an effective catalyst for the Suzuki−Miyaura coupling of
aryl chlorides.9 These results prompted us to further investigate
its application toward the Suzuki−Miyaura coupling of more
challenging substrates such as aryl sulfonates. In our continuing
efforts on the development of more efficient and practical
methods in the presence of this complex,10 we report herein the
first example of NHC−Pd(II) complex-catalyzed Suzuki−
Miyaura coupling of aryl sulfonates including tosylates,
phenylsulfonates, and even the less reactive mesylates with
arylboronic acids.
Table 2. NHC−Pd(II)−Im Complex-1-Catalyzed Coupling
of Aryl Tosylates 2 with Arylboronic Acids 3 under the
Optimal Conditions
RESULTS AND DISCUSSION
■
Initial examinations were carried out using phenyl tosylate 2a
(0.75 mmol) and 4-methoxyphenylboronic acid 3a (0.90
mmol) as the model substrates in the presence of NHC−
Pd(II)−Im complex 1 (1.0 mol %) at 110 °C for 24 h to find
the most efficient base and solvent. Representative results are
shown in Table 1. In the first round, dioxane was chosen as the
Table 1. Optimization for the Reaction Conditions
a
entry
base
solvent
yield (%)
1
2
KF·2H2O
dioxane
dioxane
dioxane
dioxane
toluene
tBuOH
3
K3PO4·3H2O
Na3PO4·12H2O
KOtBu
14
7
3
4
7
5
K3PO4·3H2O
K3PO4·3H2O
K3PO4·3H2O
K3PO4·3H2O
K3PO4·3H2O
b
17
17
18
12
92
trace
6
7
DMF
8
DME
9
morpholine
morpholine
10
a
Unless otherwise specified, all reactions were carried out using 2
a
Unless otherwise specified, all reactions were carried out using 2a
(0.75 mmol), 3 (0.9 mmol), K3PO4·3H2O (2.5 equiv), and 1 (1.0 mol
%) in morpholine (2.0 mL) at 110 °C for 24 h. The temperature was
130 °C. The temperature was 120 °C.
b
(0.75 mmol), 3a (0.9 mmol), base (2.5 equiv), and 1 (1.0 mol %) in
solvent (2.0 mL) at 110 °C for 24h. No additional base was added.
b
c
solvent to evaluate the bases (Table 1, entries 1−4). It seems
that K3PO4·3H2O was the best base to give the corresponding
coupling product 4a in 14% yield (Table 1, entry 2). For all
other bases such as KOH, KOAc, KF·2H2O, NaOtBu, and
LiOtBu, only a trace of product 4a was observed. In the second
round, using K3PO4·3H2O as the base, a variety of solvents
were tested and it was found that the solvents used significantly
affected the reaction. For instance, similar yields were obtained
stituents on the aryl tosylates have some effect on the reaction.
For example, the reaction involving 2-methylphenyl tosylate 2e
gave the corresponding product 4e only in 40% yield probably
due to the steric hindrance (Table 2, entry 4). On the other
hand, sterically hindered substituents on the arylboronic acids
have less effect on the reactions. For example, the reactions
involving 2-methylphenylboronic acid 3b and 2-methoxyphe-
nylboronic acid 3d also gave products 4g and 4i in 80 and 82%
yields, respectively (Table 2, entries 6 and 8). Reaction
involving heteroaryl tosylate such as 3-pyridinyl tosylate 2h also
gave product 4r in 81% yield (Table 2, entry 18). 2-
Naphthylboronic acid 3i, as well as 1-naphthylboronic acid 3j,
was also a suitable reaction partner (Table 2, entries 19−21).
Subsequently, aryl phenylsulfonates 5 were also examined
under the similar reaction conditions (Table 3, entries 1−5).
To our delight, all reactions took place smoothly to give the
desired coupling products 4 in good to high yields at elevated
temperature (120 °C). Nosylates 5c and 5d were labile to
decompose under identical conditions, and no desired product
was observed (Table 3, entries 6 and 7).
t
when the reactions were performed in toluene, BuOH, DMF,
and DME (Table 1, entries 5−8). Finally, to our pleasure, the
yield was dramatically increased to 92% when morpholine was
chosen as the solvent (Table 1, entry 9). Further study showed
that the solvent, morpholine, cannot play the role of the
suitable base in this reaction, which suggests that the
introduction of K3PO4·3H2O as the additional base is also
essential (Table 1, entry 10).
With the optimal reaction conditions in hand, we first set out
to examine its generality with aryl tosylates as the electrophiles
(Table 2). As can be seen from Table 2, most reactions
proceeded well to give the desired products 4 in good to high
yields under identical conditions. Sterically hindered sub-
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Table 3. NHC−Pd(II)−Im Complex-1-Catalyzed Coupling
of Aryl Sulfonates 5 with Arylboronic Acids 3 under the
Optimal Conditions
Table 5. NHC−Pd(II)−Im Complex-1-Catalyzed Coupling
of 4-Chlorophenyl Tosylate 2i
yield (%)
a
entry
5 (R1/R3)
5a (4-F/Ph)
3 (R2)
yield (%)
a
entry
3 (R2)
1 (mol %)
7
8
1
2
3
4
5
6
7
3a (4-MeO)
4f, 86
4j, 80
4v, 80
4a, 90
4w, 81
1
2
3
4
5
6
7
3l (4-F)
3l
1.0
3.0
5.0
5.0
5.0
5.0
5.0
7a, 7
7a, 6
8a, 50
8a, 66
8a, 95
8b, 83
8c, 80
8d, 86
8e, 75
5a
3e (3,5-Me2)
5a
3k (3-MeO)
3l
5b (H/Ph)
3a
3k
3a
3a
3c (4-Me)
3h (H)
3f (3-Me)
3g (3-F)
5b
5c (4-F/3-NO2C6H4)
5d (4-F/4-NO2C6H4)
a
All reactions were carried out using 5 (0.75 mmol), 3 (0.9 mmol),
K3PO4·3H2O (2.5 equiv), and 1 (1.0 mol %) in morpholine (2.0 mL)
at 120 °C for 24 h.
a
All reactions were carried out using 2i (0.75 mmol), 3 (1.8 mmol),
K3PO4·3H2O (5.0 equiv), and 1 (1.0−5.0 mol %) in morpholine (4.0
mL) at 130 °C for 24 h.
Except aryl tosylates and phenylsulfonates, the less reactive
aryl mesylates 6 were also tested under the similar reaction
conditions in order to improve the atom economy of this type
of Suzuki−Miyaura coupling (Table 4). As can be seen from
Table 4, by increasing the catalyst loading to 5.0 mol %, the
desired coupling products 4 can also be achieved in 46−62%
yields at 120 °C within 24 h.
product 8a was obtained in 50% yield, along with 7a in 7% yield
(Table 5, entry 1). Third, when the catalyst loading was
increased to 3.0 mol %, product 8a was increased to 66% yield,
along with 7a in 6% yield (Table 5, entry 2). Finally, the best
result was achieved when the catalyst loading was elevated to
5.0 mol %, giving product 8a in 95% yield as the sole one
(Table 5, entry 3). Under these optimal conditions (Table 5,
entry 3), a variety of arylboronic acids were tested and all
reactions gave the bis-coupled products 8 in good yields as the
sole products (Table 5, entries 4−7).
As can be seen from Table 1, morpholine was found to be
the only solvent for this type of Suzuki−Miyaura coupling
between aryl sulfonates and arylboronic acids. So we are
wondering if, in the reactions using morpholine as the solvent,
the imidazole moiety may be displaced by morpholine, which
will result in the real precatalyst. So in order to confirm this
assumption, two control experiments were carried out. First,
treatment of NHC−Pd(II)−Im complex 1 (0.2 mmol) in
morpholine (2.0 mL) at 110 °C for 24 h was carried out, and
complex 9 was achieved in 95% yield (Scheme 1), which may
Table 4. NHC−Pd(II)−Im Complex-1-Catalyzed Coupling
of Aryl Mesylates 6 with Arylboronic Acids 3 under the
Optimal Conditions
a
entry
6 (R1)
3 (R2)
yield (%)
1
2
6a (4-F)
6a (4-F)
6a (4-F)
6a (4-F)
6a (4-F)
6b (H)
6b
3a (4-MeO)
4f, 62
4h, 50
4k, 55
41, 50
4v, 61
4p, 52
4q, 46
4a, 51
4w, 47
4c, 47
4d, 50
3c (4-Me)
3
3f (3-Me)
Scheme 1. Transformtion of NHC−Pd(II)−Im Complex 1
in Morpholine
4
3g (3-F)
5
3k (3-MeO)
6
3f
7
3c
3a
3a
3a
3a
8
6b
9
6c (3-F)
6d (3-Me)
6e (4-iPr)
10
11
a
All reactions were carried out using 6 (0.75 mmol), 3 (0.9 mmol),
K3PO4·3H2O (2.5 equiv), and 1 (5.0 mol %) in morpholine (2.0 mL)
at 120 °C for 24 h.
suggest that the morpholine-derived complex 9 has great
stability over the 1-methylimidazole-derived complex 1 under
identical conditions. The structure of complex 9 was
unambiguously determined by X-ray single-crystal diffraction
(see Supporting Information for the details).11
Subsequently, complex-9-catalyzed reaction between phenyl
tosylate 2a and 4-methoxyphenylboronic acid 3a was
investigated under identical conditions, and product 4a was
Finally, 4-chlorophenyl tosylate 2i, as special bis-electro-
philes, was also tested in this type of Suzuki−Miyaura coupling
(Table 5). First, when the reaction between 4-chlorophenyl
tosylate 2i and 4-fluorophenylboronic acid 3l was carried out
under identical conditions, very low yields of both of the Cl-
coupled product 7a and the bis-coupled 8a were observed.
Second, when the reaction temperature was elevated to 130 °C,
C
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(for ESI). Other commercially obtained reagents were used without
further purification. Flash column chromatography was performed on
silica gel (300−400 mesh).
obtained in 88% yield (Scheme 2), which is comparable to the
result using NHC−Pd(II)−Im complex 1 as the catalyst (Table
General Procedure for the NHC−Pd(II)−Im Complex-1-
Catalyzed Suzuki−Miyaura Coupling of Aryl Sulfonates with
Arylboronic Acids. Under N2 atmosphere, aryl tosylates 2 (0.75
mmol), arylboronic acids 3 (0.9 mmol), NHC−Pd(II)−Im complex 1
(1.0 mol %), K3PO4·3H2O (2.5 equiv), and dried morpholine (2.0
mL) were successively added into a Schlenk reaction tube. The
mixture was stirred vigorously at the specified temperature for 24 h.
Then the solvent was removed under reduced pressure, and the
residue was purified by a flash column chromatography (SiO2) to give
the pure products.
Scheme 2. Complex-9-Catalyzed Reaction of 2a with 3a
under Identical Conditions
1
Compound 4a (ref 12): a white solid (127.1 mg, 94%); H NMR
1, entry 9). On the basis of the results described above, we can
conclude that morpholine-derived complex 9 may be the real
precatalyst for this type of Suzuki−Miyaura coupling between
aryl sulfonates and arylboronic acids.
(500 MHz, CDCl3, TMS) δ 7.56−7.52 (m, 4H), 7.41 (t, J = 7.5 Hz,
2H), 7.30 (t, J = 7.5 Hz, 1H), 6.97 (d, J = 8.5 Hz, 2H), 3.84 (s, 3H);
13C NMR (CDCl3, 75 MHz) δ 159.1, 140.8, 128.7, 128.1, 126.7, 126.6,
114.2, 55.3.
In addition, a similar complex such as 106e developed by
Organ’s group was also investigated for the reaction between
phenyl tosylate 2a and 4-methoxyphenylboronic acid 3a under
identical conditions (Scheme 3). In this case, product 4a was
1
Compound 4b (ref 13): a white solid (120.3 mg, 81%); H NMR
(500 MHz, CDCl3, TMS) δ 7.51 (d, J = 8.5, 2.0 Hz, 2H), 7.44 (d, J =
8.5 Hz, 2H), 7.22 (d, J = 8.5 Hz, 2H), 6.96 (d, J = 8.5 Hz, 2H), 3.84 (s,
3H), 2.38 (s, 3H); 13C NMR (CDCl3, 75 MHz) δ 158.9, 137.9, 136.3,
133.7, 129.4, 127.9, 126.5, 114.1, 55.2, 21.0.
1
Scheme 3. Complex-10-Catalyzed Reaction of 2a with 3a
under Identical Conditions
Compound 4c (ref 14): a pale yellow solid (131.8 mg, 89%); H
NMR (500 MHz, CDCl3, TMS) δ 7.52 (d, J = 9.0 Hz, 2H), 7.36−7.28
(m, 3H), 7.12 (d, J = 7.5 Hz, 1H), 6.96 (d, J = 9.0 Hz, 2H), 3.84 (s,
3H), 2.41 (s, 3H); 13C NMR (125 MHz, CDCl3) δ 159.1, 140.8,
138.3, 133.9, 128.6, 128.1, 127.6, 127.4, 123.8, 114.1, 55.3, 21.5.
1
Compound 4d (ref 15): a white solid (135.9 mg, 80%); H NMR
(500 MHz, CDCl3, TMS) δ 7.51 (d, J = 8.5 Hz, 2H), 7.48 (d, J = 8.0
Hz, 2H), 7.28 (d, J = 8.0 Hz, 2H), 6.96 (d, J = 8.5 Hz, 2H), 3.84 (s,
3H), 2.94 (hept, J = 7.0 Hz, 1H), 1.28 (d, J = 7.0 Hz, 6H); 13C NMR
(125 MHz, CDCl3) δ 158.9, 147.4, 138.4, 133.8, 128.0, 126.8, 126.6,
114.1, 55.3, 33.7, 24.0.
1
Compound 4e (ref 4e): a colorless oil (60.0 mg, 40%); H NMR
(500 MHz, CDCl3, TMS) δ 7.26−7.21 (m, 6H), 6.95 (d, J = 8.5 Hz,
2H), 3.85 (s, 3H), 2.27 (s, 3H); 13C NMR (CDCl3, 75 MHz) δ 158.5,
141.5, 135.4, 134.3, 130.3, 130.2, 129.9, 126.9, 125.7, 113.5, 55.2, 20.5.
observed in 91% yield, and further investigation showed that
complex 10 can also be transformed into complex 9 completely
under identical conditions.
1
Compound 4f (ref 4e): a white solid (142.9 mg, 94%); H NMR
(500 MHz, CDCl3, TMS) δ 7.50−7.46 (m, 4H), 7.10 (t, J = 8.5 Hz,
2H), 6.97 (d, J = 8.5 Hz, 2H), 3.85 (s, 3H); 13C NMR (CDCl3, 75
MHz) δ 162.1 (d, JC−F = 243.8 Hz), 159.1, 136.9 (d, JC−F = 3.0 Hz),
132.8, 128.1 (d, JC−F = 8.3 Hz), 128.0, 115.5 (d, JC−F = 21.0 Hz),
114.2, 55.3.
CONCLUSIONS
■
In conclusion, to the best of our knowledge, the results
reported in this paper were the first examples of practical and
easily available NHC−Pd(II) complex that can catalyze the
phosphine-free Suzuki−Miyaura coupling of aryl sulfonates
with arylboronic acids. By using the readily prepared NHC−
Pd(II)−Im complex 1 as the catalyst, the phosphine-free
Suzuki−Miyaura coupling of the easy available and advanta-
geous aryl sulfonates with arylboronic acids can proceed
efficiently to afford the target coupling products. This reaction
can tolerate a broad scope of substrates. For instance, aryl and
heteroaryl tosylates, aryl phenylsulfonates, sterically hindered
arylboronic acids, and even the less reactive aryl mesylates can
all be employed as the substrates for the reaction. These results
will enrich the utilities of the NHC−Pd(II) complexes in
organic synthesis. Furthermore, the control experiments
showed that the real precatalyst is most possibly the NHC−
Pd(II)−morpholine complex.
1
Compound 4g (ref 16): a light yellow oil (112.1 mg, 80%); H
NMR (300 MHz, CDCl3, TMS) δ 7.27−7.20 (m, 6H), 7.08 (t, J = 8.7
Hz, 2H), 2.25 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 162.4 (d, JC−F
=
243.9 Hz), 140.9, 137.8 (d, JC−F = 3.5 Hz), 135.4, 130.7 (d, JC−F = 7.9
Hz), 130.3, 129.8, 127.4, 125.8, 114.9 (d, JC−F = 21.2 Hz), 20.4.
1
Compound 4h (ref 17): a pale yellow solid (132.7 mg, 95%); H
NMR (500 MHz, CDCl3, TMS) δ 7.53−7.50 (m, 2H), 7.43 (d, J = 8.0
Hz, 2H), 7.24−7.23 (m, 2H), 7.10 (t, J = 9.0 Hz, 2H), 2.38 (s, 3H);
13C NMR (125 MHz, CDCl3) δ 162.3 (d, JC−F = 244.4 Hz), 137.4,
137.3 (d, JC−F = 3.3 Hz), 137.0, 129.5, 128.4 (d, JC−F = 7.9 Hz), 126.8,
115.5 (d, JC−F = 21.3 Hz), 21.0.
1
Compound 4i (ref 17): a pale yellow solid (124.4 mg, 82%); H
NMR (500 MHz, CDCl3, TMS) δ 7.50−7.47 (m, 2H), 7.33−7.31 (m,
2H), 7.27−6.96 (m, 4H), 3.80 (s, 3H); 13C NMR (125 MHz, CDCl3)
δ 162.0 (d, JC−F = 244.3 Hz), 156.4, 134.4 (d, JC−F = 3.4 Hz), 131.1 (d,
JC−F = 7.9 Hz), 130.7, 129.7, 128.7, 120.9, 114.8 (d, JC−F = 21.1 Hz),
111.3, 55.5.
1
EXPERIMENTAL SECTION
Compound 4j: a colorless oil (139.4 mg, 93%); H NMR (500
■
MHz, CDCl3, TMS) δ 7.51 (dd, J = 8.5, 5.5 Hz, 2H), 7.15 (s, 2H),
7.09 (t, J = 8.5 Hz, 2H), 6.99 (s, 1H), 2.37 (s, 6H); 13C NMR (125
MHz, CDCl3) δ 162.4 (d, JC−F = 244.4 Hz), 140.3, 138.3, 137.6 (d,
General Remarks. Melting points are uncorrected. NMR spectra
were recorded at 300/500 (for H NMR) or 75/125 MHz (for 13C
1
1
NMR). H NMR and 13C NMR spectra recorded in CDCl3 solutions
JC−F = 3.1 Hz), 128.9, 128.7 (d, JC−F = 8.0 Hz), 125.0, 115.4 (d, JC−F
=
were referenced to TMS (0.00 ppm) and the residual solvent peak
(77.0 ppm), respectively. J values are in hertz. Organic solvents used
were dried by standard methods. The mass analyzer types for the high-
resolution mass spectra (HRMS) are FT-ICR (for EI) and quadrupole
21.3 Hz), 21.4; IR (ν) 1602, 1517, 1224, 1162, 1099, 1014, 860, 830,
796, 785, 698 cm−1; MS (EI, m/z) 200 [M+]; HRMS (EI) calcd for
C14H13F [M]+ 200.1001, found 200.1004.
D
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1
Compound 4k (ref 18): a pale yellow oil (127.2 mg, 91%); H
NMR (500 MHz, CDCl3, TMS) δ 7.53 (dd, J = 9.0, 5.5 Hz, 2H),
7.35−7.30 (m, 3H), 7.16 (d, J = 6.5 Hz, 1H), 7.11 (t, J = 9.0 Hz, 2H),
2.41 (s, 3H); 13C NMR (125 MHz, CDCl3) δ 162.4 (d, JC−F = 244.6
Hz), 140.3, 138.4, 137.5 (d, JC−F = 3.3 Hz), 128.7 (d, JC−F = 1.5 Hz),
128.6, 128.0, 115.5 (d, JC−F = 21.3 Hz), 21.5.
(t, J = 7.5 Hz, 1H), 7.11−7.05 (m, 4H), 6.87 (dd, J = 8.0, 2.5 Hz, 1H),
3.83 (s, 3H); 13C NMR (125 MHz, CDCl3) δ 162.5 (d, JC−F = 244.9
Hz), 159.9, 141.7, 137.1 (d, JC−F = 3.1 Hz), 129.8, 128.7 (d, JC−F = 8.0
Hz), 119.5, 115.5 (d, JC−F = 21.3 Hz), 112.8, 112.5, 55.2.
Compound 4w (ref 24): a colorless oil (112.0 mg, 81%); 1H NMR
(500 MHz, CDCl3, TMS) δ 7.58 (d, J = 8.5 Hz, 2H), 7.41 (t, J = 7.5
Hz, 2H), 7.35−7.31 (m, 2H), 7.18−7.16 (m, 1H), 7.12 (t, J = 2.0 Hz,
1H), 6.88 (dd, J = 7.5, 2.5 Hz, 1H), 3.82 (s, 3H, OMe); 13C NMR
(125 MHz, CDCl3) δ 159.9, 142.7, 141.0, 129.7, 128.7, 127.4, 127.1,
119.6, 112.8, 112.6, 55.2.
1
Compound 4l: a colorless oil (122.3 mg, 86%); H NMR (500
MHz, CDCl3, TMS) δ 7.52 (dd, J = 8.5, 5.0 Hz, 2H), 7.38 (td, J = 8.0,
6.0 Hz, 1H), 7.31 (d, J = 7.5 Hz, 1H), 7.23 (dt, J = 10.0, 3.5 Hz, 1H),
7.13 (t, J = 8.5 Hz, 2H), 7.03 (td, J = 10.0, 2.5 Hz, 1H); 13C NMR
1
(125 MHz, CDCl3) δ 163.2 (d, JC−F = 244.4 Hz), 162.8 (d, JC−F
=
Compound 7a: a white solid (18.1 mg, 7%); mp 121−122 °C; H
245.9 Hz), 142.5 (d, JC−F = 7.8 Hz), 136.09 (d, JC−F = 3.0 Hz), 136.07
(d, JC−F =2.4 Hz), 130.3 (d, JC−F = 8.5 Hz), 128.7 (d, JC−F = 8.1 Hz),
NMR (500 MHz, CDCl3, TMS) δ 7.74 (d, J = 8.5 Hz, 2H), 7.47 (dd, J
= 8.5, 5.5 Hz, 2H), 7.43 (d, J = 8.5 Hz, 2H), 7.32 (d, J = 8.5 Hz, 2H),
7.10 (t, J = 8.5 Hz, 2H), 7.04 (d, J = 8.5 Hz, 2H), 2.45 (s, 3H); 13C
NMR (125 MHz, CDCl3) δ 162.6 (d, JC−F = 245.6 Hz), 149.0, 145.4,
139.2, 135.9 (d, JC−F = 3.3 Hz), 132.5, 129.8, 128.7 (d, JC−F = 8.0 Hz),
128.5, 128.1, 122.7, 115.7 (d, JC−F = 21.5 Hz), 21.7; IR (ν) 1596, 1493,
1378, 1248, 1206, 1190, 1180, 1159, 1091, 858, 826, 748, 727, 706,
677 cm−1; MS (ESI) 365 [M + Na]+; HRMS (ESI) calcd for
C19H15FO3SNa [M + Na]+ 365.0618, found 365.0627.
122.6 (d, JC−F = 2.8 Hz), 115.8 (d, JC−F = 21.5 Hz), 114.0 (d, JC−F
=
21.0 Hz), 113.9 (d, JC−F = 22.0 Hz); IR (ν) 1615, 1599, 1583, 1516,
1484, 1399, 1232, 1185, 1164, 881, 832, 780, 688 cm−1; MS (EI, m/z)
190 [M+]; HRMS (EI) calcd for C12H8F2 [M]+ 190.0594, found
190.0595.
Compound 4m (ref 19): a colorless oil (116.1 mg, 85%); 1H NMR
(300 MHz, CDCl3, TMS) δ 7.48 (d, J = 8.1 Hz, 2H), 7.39−7.36 (m,
2H), 7.31 (td, J = 7.2, 1.2 Hz, 1H), 7.25−7.22 (m, 2H), 7.15−7.13 (m,
1H), 2.41 (s, 3H), 2.39 (s, 3H); 13C NMR (125 MHz, CDCl3) δ
141.2, 138.5, 138.2, 136.9, 129.4, 128.6, 127.8, 127.7, 127.0, 124.1,
21.5, 21.1.
1
Compound 8a (ref 25): a white solid (190.2 mg, 95%); H NMR
(500 MHz, CDCl3, TMS) δ 7.61 (s, 4H), 7.59 (dd, J = 8.5, 5.5 Hz,
4H), 7.14 (t, J = 8.5 Hz, 4H); 13C NMR (125 MHz, CDCl3) δ 162.5
(d, JC−F = 245.1 Hz), 139.2, 136.7 (d, JC−F = 3.3 Hz), 128.6 (d, JC−F
=
1
Compound 4n (ref 20): a colorless oil (117.2 mg, 80%); H NMR
7.9 Hz), 127.4, 115.7 (d, JC−F = 21.3 Hz).
1
(500 MHz, CDCl3, TMS) δ 7.37 (d, J = 7.5 Hz, 1H), 7.36 (s, 1H),
7.30 (t, J = 7.5 Hz, 1H), 7.19 (s, 2H), 7.13 (d, J = 7.5 Hz, 1H), 6.98 (s,
1H), 2.40 (s, 3H), 2.37 (s, 6H); 13C NMR (125 MHz, CDCl3) δ
141.5, 141.4, 138.1, 128.8, 128.5, 128.0, 127.8, 125.1, 124.3, 21.5, 21.4.
Compound 8b (ref 26): a white solid (160.9 mg, 83%); H NMR
(500 MHz, CDCl3, TMS) δ 7.64 (s, 4H), 7.54 (d, J = 8.0 Hz, 4H),
7.26 (d, J = 8.0 Hz, 4H), 2.40 (s, 6H); 13C NMR (125 MHz, CDCl3) δ
139.8, 137.9, 137.1, 129.5, 127.2, 126.9, 21.1.
1
1
Compound 4o (ref 21): a white solid (151.2 mg, 96%); H NMR
Compound 8c (ref 26): a white solid (138.0 mg, 80%); H NMR
(500 MHz, CDCl3, TMS) δ 7.50 (d, J = 8.0 Hz, 2H), 7.47 (d, J = 8.0
Hz, 2H), 7.28 (d, J = 8.0 Hz, 2H), 7.22 (d, J = 8.0 Hz, 2H), 2.93 (hept,
J = 7.0 Hz, 1H), 2.37 (s, 3H), 1.28 (d, J = 7.0 Hz, 6H); 13C NMR (125
MHz, CDCl3) δ 147.6, 138.6, 138.3, 136.6, 129.4, 126.85, 126.83,
126.77, 33.8, 24.0, 21.1.
(500 MHz, CDCl3, TMS) δ 7.68 (s, 4H), 7.64 (d, J = 7.0 Hz, 4H),
7.46 (t, J = 7.5 Hz, 4H), 7.36 (t, J = 7.5 Hz, 2H); 13C NMR (125
MHz, CDCl3) δ 140.7, 140.1, 128.8, 127.5, 127.3, 127.0.
1
Compound 8d (ref 27): a white solid (166.0 mg, 86%); H NMR
(500 MHz, CDCl3, TMS) δ 7.65 (s, 4H), 7.45−7.43 (m, 4H), 7.34 (t,
J = 7.5 Hz, 2H), 7.17 (d, J = 7.5 Hz, 2H), 2.43 (s, 6H); 13C NMR (125
MHz, CDCl3) δ 140.7, 140.1, 138.4, 128.7, 128.1, 127.8, 127.4, 124.1,
21.5.
1
Compound 4p (ref 19): a colorless oil (103.0 mg, 82%); H NMR
(300 MHz, CDCl3, TMS) δ 7.57 (d, J = 7.8 Hz, 2H) 7.44−7.37 (m,
4H), 7.31 (t, J = 7.5 Hz, 2H), 7.15 (d, J = 7.5 Hz, 1H), 2.40 (s, 3H);
13C NMR (125 MHz, CDCl3) δ 141.4, 141.2, 138.3, 128.7, 128.6,
127.97, 127.95, 127.2, 127.1, 124.3, 21.5.
1
Compound 8e (ref 28): a white solid (149.7 mg, 75%); H NMR
(500 MHz, CDCl3, TMS) δ 7.62 (s, 4H), 7.38 (t, J = 5.0 Hz, 4H), 7.30
(dd, J = 9.0, 1.5 Hz, 2H), 7.05−7.01 (m, 2H); 13C NMR (125 MHz,
CDCl3) δ 163.2 (d, JC−F = 244.3 Hz), 142.7 (d, JC−F = 7.6 Hz), 139.3
(d, JC−F = 2.1 Hz), 130.3 (d, JC−F = 8.4 Hz), 127.5, 122.6 (d, JC−F = 2.6
Hz), 114.2 (d, JC−F = 21.1 Hz), 113.9 (d, JC−F = 22.0 Hz).
Compound 9: A yellow solid (124.1 mg, 95%); mp 150−151 °C;
1H NMR (300 MHz, CDCl3, TMS) δ 7.50 (t, J = 7.8 Hz, 2H), 7.34 (d,
J = 7.8 Hz, 4H), 7.09 (s, 2H), 3.60 (dd, J = 12.0, 3.3 Hz, 2H), 3.24 (td,
J = 12.0, 2.1 Hz, 2H), 3.10−3.01 (m, 6H), 2.50−2.46 (m, 3H), 1.44
(d, J = 6.6 Hz, 12H), 1.09 (d, J = 6.6 Hz, 12H); 13C NMR (75 MHz,
CDCl3) δ 157.0, 146.6, 135.0, 130.1, 124.8, 123.8, 67.6, 47.0, 28.7,
26.2, 23.1; IR (ν) 1727, 1698, 1464, 1345, 1234, 1208, 1116, 1098,
1012, 882, 802, 757, 742, 706 cm−1; MS (ESI) 652 [M + H]+; HRMS
(ESI) calcd for C31H46Cl2N3OPd [M + H]+ 652.2053, found
652.2040.
1
Compound 4q (ref 19): a white solid (103.2 mg, 82%); H NMR
(500 MHz, CDCl3, TMS) δ 7.57 (dd, J = 8.0, 1.0 Hz, 2H), 7.49 (d, J =
8.0 Hz, 2H), 7.42 (t, J = 8.0 Hz, 2H), 7.31 (t, J = 8.00 Hz, 1H), 7.24
(d, J = 8.0 Hz, 2H), 2.39 (s, 3H); 13C NMR (125 MHz, CDCl3) δ
141.2, 138.4, 137.0, 129.5, 128.7, 126.98, 126.96, 126.9, 21.1.
1
Compound 4r (ref 4e): a pale yellow solid (112.3 mg, 81%); H
NMR (300 MHz, CDCl3, TMS) δ 8.81 (s, 1H), 8.54 (d, J = 4.8 Hz,
1H), 7.81 (d, J = 8.1 Hz, 1H), 7.51 (d, J = 8.4 Hz, 2H), 7.31 (dd, J =
8.1, 4.8 Hz, 1H), 7.00 (d, J = 8.4 Hz, 2H), 3.86 (s, 3H); 13C NMR (75
MHz, CDCl3) δ 159.6, 147.8, 147.7, 136.1, 133.7, 130.0, 128.1, 123.4,
114.4, 55.2.
1
Compound 4s (ref 19): a white solid (123.4 mg, 81%); H NMR
(500 MHz, CDCl3, TMS) δ 8.04 (s, 1H), 7.92−7.86 (m, 3H), 7.85−
7.71 (m, 3H), 7.52−7.46 (m, 4H), 7.39−7.36 (m, 1H); 13C NMR
(125 MHz, CDCl3) δ 141.1, 138.6, 133.7, 132.6, 128.8, 128.4, 128.2,
127.6, 127.4, 127.3, 126.3, 125.9, 125.8, 125.6.
1
ASSOCIATED CONTENT
Compound 4t (ref 22): a white solid (156.5 mg, 94%); H NMR
■
(500 MHz, CDCl3, TMS) δ 7.97 (s, 1H), 7.90−7.84 (m, 3H), 7.69−
7.64 (m, 3H), 7.52−7.46 (m, 2H), 7.18−7.14 (m, 2H); 13C NMR
(125 MHz, CDCl3) δ 162.5 (d, JC−F = 245.1 Hz), 137.6, 137.2 (d, JC−F
= 3.3 Hz), 133.6, 132.5, 128.9 (d, JC−F = 8.0 Hz), 128.5, 128.1, 127.6,
126.4, 126.0, 125.6, 125.4, 115.7 (d, JC−F = 21.3 Hz).
S
* Supporting Information
1H and 13C NMR spectra of compounds 4, 7a, 8, and 9. X-ray
data of compound 9 in CIF format. This material is available
free of charge via the Internet at http://pubs.acs.org.
1
Compound 4u (ref 23): a white solid (141.8 mg, 85%); H NMR
(500 MHz, CDCl3, TMS) δ 7.92−7.83 (m, 3H), 7.53--7.38 (m, 6H),
AUTHOR INFORMATION
7.20−7.16 (m, 2H).13C NMR (125 MHz, CDCl3) δ 162.3 (d, JC−F
=
■
244.6 Hz), 139.2, 136.7 (d, JC−F = 3.3 Hz), 133.8, 131.7, 131.6 (d, JC−F
= 7.9 Hz), 128.3, 127.8, 127.0, 126.1, 125.83, 125.76, 125.3, 115.2 (d,
JC−F = 21.1 Hz).
Corresponding Author
*Fax: 86-577-86689300. E-mail: shaolix@wzu.edu.cn.
1
Notes
Compound 4v (ref 4e): a light yellow oil (120.6 mg, 80%); H
NMR (500 MHz, CDCl3, TMS) δ 7.51 (dd, J = 8.0, 5.0 Hz, 2H), 7.32
The authors declare no competing financial interest.
E
dx.doi.org/10.1021/jo301270t | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
Chem. Res. 2008, 41, 1440−1449. (d) Fortman, G. C.; Nolan, S. P.
ACKNOWLEDGMENTS
■
Chem. Soc. Rev. 2011, 40, 5151−5169. (e) Valente, C.; Çalimsiz, S.;
Financial support from the Natural Science Foundation of
Zhejiang Province (No. LY12B02012) and the Opening
Foundation of Zhejiang Provincial Top Key Discipline (No.
1000612001) is greatly appreciated.
Hoi, K. H.; Mallik, D.; Sayah, M.; Organ, M. G. Angew. Chem., Int. Ed.
2012, 51, 3314−3332.
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(11) Crystal data of 9: empirical formula C62H92Cl4N6O3Pd2;
molecular weight = 1324.02; color, habit: colorless, prismatic; crystal
system: monoclinic; lattice type: primitive; lattice parameters: a =
16.4227(16) Å, b = 18.4780(19) Å, c = 25.266(3) Å, α = 90°, β =
103.557(2)o, γ = 90°, V = 7453.5(13) Å3; space group: P2(1)/c; Z = 4;
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residuals: R; Rw: 0.0581, 0.2081. CCDC-881917 contains the
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dx.doi.org/10.1021/jo301270t | J. Org. Chem. XXXX, XXX, XXX−XXX

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