Palladium-catalyzed decarboxylative C3-acylation of benzofurans and benzothiophenes with α-oxocarboxylic acids via direct sp2 C-H bond activation

Article abstract of DOI:10.1016/j.tet.2014.12.095

An efficient approach to decarboxylative C3-acylation of benzothiophenes or benzofurans with α-oxocarboxylic acids via palladium-catalyzed C-H bond activation was developed. This method was compatible with a variety of functional groups and provided an attractive route to 3-acylbenzothiophenes and 3-acylbenzofurans in good to high yields.

Full text of DOI:10.1016/j.tet.2014.12.095

Tetrahedron xxx (2015) 1e7
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Palladium-catalyzed decarboxylative C3-acylation of benzofurans
and benzothiophenes with
bond activation
a
-oxocarboxylic acids via direct sp2 CeH
,
a
a
a
,
a,b,
*
Wei-Jie Gong a, De-Xian Liu a , Fei-Long Li , Jun Gao , Hong-Xi Li , Jian-Ping Lang
*
*
a College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, PR China
b State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 210032, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
An efficient approach to decarboxylative C3-acylation of benzothiophenes or benzofurans with
a-ox-
Received 9 November 2014
Received in revised form 22 December 2014
Accepted 29 December 2014
Available online xxx
ocarboxylic acids via palladium-catalyzed CeH bond activation was developed. This method was com-
patible with a variety of functional groups and provided an attractive route to 3-acylbenzothiophenes
and 3-acylbenzofurans in good to high yields.
Ó 2015 Elsevier Ltd. All rights reserved.
Keywords:
Decarboxylation
Palladium(II)
Benzofuran
Benzothiophene
Acylation
a
-Oxocarboxylic acids
1. Introduction
with n-BuLi, dimethylformamide, and chloroacetone provided
2-acetylbenzothiophene.6f These methods required, a multistep
The (hetero)aryl ketones are fundamental building blocks for
natural products, medicinally-relevant molecules, and organic
functional materials.1 More specifically, acylbenzothiophene and
acylbenzofuran have attracted considerable attention in the phar-
maceutical chemistry.2 For example, the 3-acylbenzofuran de-
rivatives, benzbromarone, and amiodarone (Scheme 1), are
employed as the uricosuricagent3 and antiarrhythmic agents,4 re-
spectively. The aryl-benzothiophenyl ketone, raloxifene (Scheme 1),
can be used as the vasodilator.5 There are numerous synthetic
approaches6 to C2 or C3-acyl benzofuran and benzothiophene
derivatives, including palladium-catalyzed cross-coupling reaction
of arylboronic acids, carbon monoxide, and aryl iodides,6a photo-
reactions of arenecarbothioamides with benzofuran or benzothio-
phene in benzene,6b reduction, S-alkylation, re-oxidation, and
cyclization of 2-mercaptobenzoic acids,6c reaction of benzothio-
phene with carboxylic acids and trifluoroacetic anhydride in the
presence of H3PO4,6d reaction of o-thioalkyl and o-thioaryl
substituted phenyl radicals with alkynes.6e Reaction of thiophenol
synthesis of starting material, or the use of toxic carbon monoxide,
unstable diazo compounds, and pyrophoric n-BuLi, and led to the
formation of a mixture of regioisomers. Traditionally, the simple
and straightforward method for the synthesis of acylbenzothio-
phenes or benzofurans appeared to be the FriedeleCrafts acylation
reactions,7 which, however, involved the use of excess AlCl3, had
poor regioselectivity, and led to the formation of environmentally
harmful gaseous HCl. Therefore, screening out simple and practical
* Corresponding authors. Tel.: þ86 512 6588 2865; fax: þ86 512 6588 0328;
Scheme 1. Some structures of bioactive 3-acylbenzofuran and 3-acylbenzothiophene
derivatives.
e-mail address: jplang@suda.edu.cn (J.-P. Lang).
http://dx.doi.org/10.1016/j.tet.2014.12.095
0040-4020/Ó 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Gong, W.-J.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2014.12.095

2
W.-J. Gong et al. / Tetrahedron xxx (2015) 1e7
processes for the syntheses of acylbenzofuran and acylbenzothio-
phene remains a great challenge.
2. Results and discussion
In the past decade, the decarboxylative acylation of unactivated
Our investigation started with the decarboxylative cross-
coupling reaction of 2-(benzothiophen-2-yl)pyridine (1) and
2-oxophenylacetic acid (2a) in the presence of 10 mol % Pd(PPh3)4
with Ag2CO3 (2 equiv) as a decarboxylative reagent, K2S2O8
(2 equiv) as the co-oxidant in 1,4-dioxane/HOAc/DMSO at 120 ꢀC
under air (Table 1). After 21 h, the desired product phenyl(2-(pyr-
idin-2-yl)benzothiophen-3-yl)methanone (3a) could be obtained
in 84% yield (entry 1). Encouraged by this initial result, we began to
optimize the reaction conditions with respect to different palla-
dium catalysts, oxidants, and solvents. The screening of catalysts
indicated that for catalyzing the decarboxylative cross-coupling
reactions of 1 with 2a, Pd(PPh3)4 (entry 1) was more effective
than Pd(TFA)2 (TFA¼trifluoroacetate), PdCl2, Pd(OAc)2, and
Pd2(dba)3 (dba¼dibenzylideneacetone) (entries 2e5). For the oxi-
dants, Ag2O (entry 6) seemed better than Ag2CO3 (entry 1), AgOAc
and Cu(OAc)2 (entries 7 and 8). It was noted that the yield of
resulting product was dramatically increased from 87% to 96%
(entry 5) when tetrabutyl ammonium bromide (TBAB) was added
into the catalytic system (entry 10). The control experiments
showed that Pd(PPh3)4, Ag2O, and K2S2O8 were required for this
coupling reaction. As shown in Table 1 (entries 14e18), a strong
solvent dependence of the acylation was observed. The yield of the
desired product was very low in the absence of one of these three
reagents. Solvent screening revealed that the optimal results could
be obtained with a co-solvent of 1,4-dioxane/AcOH/DMSO in
a volume ratio of 7.5:1.5:1, providing the product (3a) in 96% yield.
The yield of 3a decreased with reduced amount of Ag2O or K2S2O8.
Therefore, the optimal reaction conditions were finally established
as follow: 10 mol % Pd(PPh3)4, 2.0 equiv of Ag2O, 2.0 equiv of
K2S2O8, and 1.0 equiv of TBAB in 7.5:1.5:1 1,4-dioxane/HOAc/DMSO
at 120 ꢀC under air.
arenes through metal-catalyzed CeH activation using a-oxocarbox-
ylic acids as acylating resources8 has been an attractive synthetic
method for the formation of aryl ketones. Such methods did not re-
quire the use of stoichiometric organometallic coupling reagents and
gave riseto CO2 instead of toxic metalcompounds. Geand co-workers
disclosed Pd-catalyzed decarboxylative C(sp2)eH acylation of acet-
anilides, or 2-phenylpyridines or benzoic acids with a-oxocarboxylic
acids.9 Afterthatthemetal-mediated decarboxylativeortho-acylation
of O-methyl ketoximes, phenylacetamides, O-phenyl carbamates,
O-methyl oximes, azoxybenzenes, azobenzenes, 2-aryloxypyridines,
cyclic enamides, (benzyl)(aryl)sulfane, and 2-phosphorylbiphenyl
with
a
-oxocarboxylic acids have been reported.10 As far as the
decarboxylative acylationofheteroarenesbyCeHfunctionalizationis
concerned, only indole, azole and their derivatives11 have been ex-
plored. Although the decarboxylative arylation of benzofuran or
benzothiophene has been well explored,12 the Pd-catalyzed decar-
boxylative acylation of C(sp2)eH bond has never been reported. Very
recently, Beller and co-workers13a reported ruthenium-catalyzed
carbonylative direct acylation of five-membered and condensed
heterocycles with toxic carbon monoxide and aryliodides in moder-
ate to good yields. Han and Pan et al.13b have demonstrated Pd-cat-
alyzed C3-acylation of benzofurans and benzothiophenes by
dehydrogenative coupling reaction using unstable aldehydes as ac-
ylating agents and chlorobenzene as a solvent. These limitations
promptedchemiststodevelopnewconvenientmethodologytoget3-
acylbenzofurans and 3-acylbenzofurans. As an extension of our pro-
ject on the oxidative decarboxylative coupling reactions,14 we herein
report an alternative protocol to achieve the C3-acylation of benzo-
furan and benzothiophene with the a-oxocarboxylic acid via palla-
dium-catalyzed C(sp2)eH activation.
Table 1
Optimization of the reaction conditions for the decarboxylative C3-acylation of 2-(benzothiophen-2-yl)pyridine with
a
-oxocarboxylic acida
Entry
Cat.
Oxidant
Co-oxidant
Additive
1,4-Dioxane/HOAc/DMSO
Yieldb (%)
1
2
3
4
5
6
7
8
Pd(PPh3)4
Pd(TFA)2
PdCl2
Pd(OAc)2
Pd2(dba)3
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Ag2CO3
Ag2CO3
Ag2CO3
Ag2CO3
Ag2CO3
Ag2O
AgOAc
Cu(OAc)2
Ag2O
K2S2O8
K2S2O8
K2S2O8
K2S2O8
K2S2O8
K2S2O8
K2S2O8
K2S2O8
(NH4)2S2O8
K2S2O8
K2S2O8
K2S2O8
7.5:1.5:1
7.5:1.5:1
7.5:1.5:1
7.5:1.5:1
7.5:1.5:1
7.5:1.5:1
7.5:1.5:1
7.5:1.5:1
7.5:1.5:1
7.5:1.5:1
7.5:1.5:1
7.5:1.5:1
7.5:1.5:1
1,4-Dioxane
DMSO
84
79
76
73
78
87
40
28
26
96
16
7
28
22
14
15
73
62
58
69
9
10
11
12
13
14
15
16
17
18
19c
20d
Ag2O
Ag2O
TBAB
TBAB
TBAB
TBAB
TBAB
TBAB
TBAB
TBAB
TBAB
TBAB
TBAB
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Ag2O
Ag2O
Ag2O
Ag2O
Ag2O
Ag2O
Ag2O
Ag2O
K2S2O8
K2S2O8
K2S2O8
K2S2O8
K2S2O8
K2S2O8
K2S2O8
HOAc
7:2:1
4:1:d
7.5:1.5:1
7.5:1.5:1
a
Reaction conditions: 1 (0.1 mmol), 2a (0.2 mmol), palladium reagent (0.01 mmol), oxidant (0.2 mmol), co-oxidant (0.2 mmol), 1.0 equiv of tetrabutyl ammonium bromide
(TBAB), solvent (1.5 mL), 120 ꢀC, 21 h.
b
GC yields.
Ag2O (1.0 equiv).
K2S2O8 (1.0 equiv).
c
d
Please cite this article in press as: Gong, W.-J.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2014.12.095

W.-J. Gong et al. / Tetrahedron xxx (2015) 1e7
3
With the optimized reaction conditions in hand, we turned our
attention to investigate the scope of the decarboxylative acylation
of 2-(benzothiophen-2-yl)pyridine with a-oxocarboxylic acids. The
2-arylglyoxylic acids proceeded smoothly to form the correspond-
ing 3-acylbenzofurans in more than 90% isolated yields (5ae5d and
5i). However, the moderate yields were observed for 2-arylglyoxylic
acids with electron-withdrawing groups such as fluoro (5e, 77%),
chloro (5f, 71%) or bromo groups (5g, 73%; 5h, 71%). It seemed that
the o-substituted chloro group on phenyl rings of 2-oxophenylacetic
acid did not hamper the decarboxylative acylation reaction
compatibility of substituted phenylglyoxylic acids was summarized
in Table 2. Various 2-arylglyoxylic acids containing different func-
tional groups in the aromatic ring showed high reactivity to give
the corresponding products in good to high yields (3ae3m).
Interestingly, high yields could be obtained with p-fiuoro (3e),
p-chloro (3f), p-bromo (3g), and m-bromo (3h) substituted phe-
nylglyoxylic acids, although it was not surprising that halogens
were tolerated under the reaction conditions. However, the re-
action did not show any obvious electronic preference. The
electron-rich and electron-deficient 2-arylglyoxylic acids afforded
the corresponding 3-acylbenzothiophene products 3be3j in
76e95% yield. Meanwhile, 2-(naphthalen-2-yl)-2-oxoacetic acid
underwent the reaction smoothly to give the product 3k in 84%
(5j, 90%). For the heteroaromatic
a-oxocarboxylic acids such as
2-thienylglyoxylic acid and 2-furylglyoxylic acid, the corresponding
2-thienyl- and 2-furyl-benzofuryl ketones were obtained in 74% and
79% isolated yields, respectively (Table 3).
According to the previous reports,10,11 we propose the possible
catalytic reaction mechanism (Scheme 2) to account for the
aforementioned results. Firstly, the ortho-palladation of 1 or 4 with
Pd(II) to provide the five-membered palladacycle intermediate I.
Secondly, the intermediate I reacts with the intermediate II, which
is formed from the silver-mediated decarboxylation of 2, to gen-
erate the acylePd(II) intermediate III. Thirdly, the intermediate III
undergoes the reductive elimination to produce the desired ketone
product and Pd(0). Finally, the regenerated Pd(0) catalyst can be re-
oxidized into the active Pd(II) catalyst with K2S2O8, thereby fur-
nishing the catalytic cycle.
yield. It is noteworthy that the heterocyclic a-keto acids such as
2-thienylglyoxylic acid and 2-furylglyoxylic acid also provided
bisheteroaryl ketone products (3l and 3m) in moderate yields
(64% and 67%).
Encouraged by the high efficiency for the reactions of 2-(ben-
zothiophen-2-yl)pyridine with
a-oxocarboxylic acids described
above, we also investigated the decarboxylative acylation reactions
of 2-(benzofuran-2-yl)pyridine (4) with various phenylglyoxylic
acids under the optimal reaction conditions. The reaction of 4 and 2a
catalyzed by Pd(PPh3)4 in the presence of Ag2CO3 and K2S2O8 in 1,4-
dioxane/HOAc/DMSO produced phenyl(2-(pyridin-2-yl)benzofu-
ran-3-yl)methanone in 71% yield. When Ag2CO3 was replaced by
Ag2O, the similar reaction gave the product in 78% yield. In the case
of the solvent, the reaction carried out in 1,4-dioxane/HOAc/DMF
gave higher yields (90%) than that in 1,4-dioxane/HOAc/DMSO. The
2-arylglyoxylic acids containing different functional groups in the
aromatic ring also showed good reactivity to give the products in
good to high yields (5ae5m), using Ag2CO3 as a decarboxylative
reagent, K2S2O8 as a co-oxidant in 1,4-dioxane/HOAc/DMF (v/v/
v¼7.5:1.5:1) at 120 ꢀC in air. The electron-rich and -neutral
3. Conclusions
In summary, we have demonstrated an efficient approach to the
decarboxylative C3-acylation of benzofurans and benzothiophenes
with
a-oxocarboxylic acids via palladium-catalyzed CeH activa-
tion. The remarkable features of this methodology include good
product yields and wide tolerance of various functional groups. It
provides a highly versatile alternative to the existing methods for
building the biologically important C3-acylated benzofuran and
benzothiophene units. It is also applicable to the synthesis of more
pharmacologically important benzofuran and benzothiophene
derivatives.
Table 2
Palladium-catalyzed C3-acylation of 2-(benzo[b]thiophen-2-yl)pyridine with a
-oxocarboxylic acidsa
Please cite this article in press as: Gong, W.-J.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2014.12.095

4
W.-J. Gong et al. / Tetrahedron xxx (2015) 1e7
Table 3
Palladium-catalyzed C3-acylation of 2-(benzofuran-2-yl)pyridine with a
-oxocarboxylic acidsa
4. Experimental
4.1. General
internal standard. Resonance patterns were reported with the
notations of s (singlet), d (doublet), and m (multiplet). In addition,
coupling constants J were reported in hertz (Hz). The uncorrected
melting points were re-determined on a Mel-Temp II apparatus.
All reactions were performed under air atmosphere unless
stated otherwise. Commercially available reagents were used as
received without purification. Pyridine was distilled from CaH2.
2-(Benzo[b]thiophen-2-yl)pyridine and 2-(benzofuran-2-yl)pyri-
4.2. General procedure for the acylation of benzothiophene
or benzofuran with a-oxocarboxylic acid
dine were prepared according to the literature.13b
a-Oxocarboxylic
A sealed reaction tube equipped with a magnetic stirring bar
was charged with 2-(benzothiophen-2-yl)pyridine (0.1 mmol),
acids were synthesized according to the reported method.15 Col-
umn chromatography was carried out on silica gel (300e400
mesh). 1H NMR and 13C NMR spectra were recorded at ambient
temperature on a Varian NITYplus-400. CDCl3 and DMSO-d6 were
used as deuterated solvents. The chemical shifts d were reported as
parts per million (ppm) relative to, respectively, the TMS as the
a-oxocarboxylic acids (0.2 mmol), K2S2O8 (0.2 mmol), tetrabutyl
ammonium bromide (TBAB) (0.1 mmol), Ag2O (0.2 mmol), and
Pd(PPh3)4 (0.01 mmol) in 1,4-dioxane/HOAc/DMSO (1.5 mL; v/v/
v¼7.5:1.5:1). The reaction mixture was stirred vigorously at 120 ꢀC
in an oil bath for 21 h. Then it was cooled to room temperature and
diluted with ethyl acetate and filtered. After the filtrate was con-
centrated under reduced pressure, the residue was purified
through the flash column chromatography on silica gel to afford the
desired products.
4.2.1. 2-(Benzo[b]thiophen-2-yl)pyridine (1). 1H NMR (400 MHz,
CDCl3):
7.76e7.73 (m, 1H), 7.38e7.33 (m, 2H), 7.23e7.20 (m, 1H). 13C NMR
(400 MHz, CDCl3):
d¼8.65e8.63 (m, 1H), 7.88e7.86 (m, 2H), 7.82e7.80 (m, 2H),
d
¼152.5, 149.6, 144.6, 140.8, 140.6, 136.9, 125.2,
124.6, 124.3, 122.7, 122.7, 121.4, 119.8 ppm.
4.2.2. 2-(Benzofuran-2-yl)pyridine (4). 1H NMR (400 MHz, DMSO-
d6):
7.76e7.73 (m, 1H), 7.38e7.33 (m, 2H), 7.23e7.20 (m, 1H) ppm. 13
NMR (400 MHz, DMSO-d6):
¼155.3, 155.1, 150.4, 148.7, 137.7, 128.9,
125.8, 123.9, 123.9, 122.3, 120.0, 111.9, 105.2 ppm.
d
¼8.65e8.63 (m, 1H), 7.88e7.86 (m, 2H), 7.82e7.80 (m, 2H),
C
d
4.2.3. Phenyl(2-(pyridine-2-yl)benzo[b]thiophen-3-yl)methanone
(3a). Yellow solid. Mp 74e75 ꢀC. 1H NMR (400 MHz, CDCl3):
Scheme 2. The proposed reaction mechanism.
d¼8.48e8.47 (m, 1H), 7.92 (d, J¼4.0 Hz, 1H), 7.87 (d, J¼4.0 Hz, 2H),
Please cite this article in press as: Gong, W.-J.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2014.12.095

W.-J. Gong et al. / Tetrahedron xxx (2015) 1e7
5
7.63 (d, J¼8.0 Hz, 1H), 7.52e7.46 (m, 2H), 7.43e7.39 (m, 2H),
7.36e7.32 (m, 3H), 7.09e7.07 (m, 1H) ppm. 13C NMR (400 MHz,
7.70e7.64 (m, 2H), 7.57 (t, J¼8.0 Hz, 2H), 7.45e7.35 (m, 3H),
7.18e7.15 (m, 1H), 7.11e7.08 (m, 1H) ppm. 13C NMR (400 MHz,
CDCl3):
d
¼194.8, 151.2, 149.5, 143.8, 139.6, 139.5, 137.5, 136.5, 133.5,
CDCl3):
d
¼193.18,150.8,149.3,143.8,139.5,139.4,139.3,136.8,136.0,
133.1, 129.7, 128.6, 125.7, 125.1, 123.7, 122.8, 122.7, 122.3 ppm.
132.6, 132.0, 130.1, 128.3, 125.9, 125.4, 123.6, 123.0, 122.8, 122.7,
LCeMS (EI): m/z calcd [Mþ1]þ¼316.1; found: 316.1.
122.4 ppm. LCeMS (EI): m/z calcd [Mþ1]þ¼394.0; found: 394.0.
4.2.4. (2-(Pyridin-2-yl)benzo[b]thiophen-3-yl)(p-tolyl)methanone
4.2.11. (3-Methoxyphenyl)(2-(pyridin-2-yl)benzo[b]thiophen-3-yl)
(3b). Yellow solid. Mp 104e106 ꢀC. 1H NMR (400 MHz, CDCl3):
methanone (3i). Yellow solid. Mp 137e138 ꢀC. 1H NMR (400 MHz,
d
¼8.52 (d, J¼4.0 Hz, 1H), 7.91 (d, J¼8.0 Hz, 1H), 7.78 (d, J¼8.0 Hz,
CDCl3):
d
¼8.51e8.50 (m, 1H), 7.92 (d, J¼4.0 Hz, 1H), 7.64 (d,
2H), 7.58 (d, J¼8.0 Hz, 1H), 7.51e7.49 (m, 1H), 7.45e7.30 (m, 3H),
J¼4.0 Hz, 1H), 7.55e7.51 (m, 2H), 7.45e7.39 (m, 2H), 7.36e7.33 (m,
7.15e7.08 (m, 3H), 2.34 (s, 3H) ppm. 13C NMR (400 MHz, CDCl3):
2H), 7.19 (t, J¼4.0 Hz, 1H), 7.12e7.10 (m, 1H), 7.04e7.02 (m, 1H), 3.79
d
¼194.6, 151.2, 149.4, 144.7, 143.3, 139.6, 139.5, 136.6, 134.9, 133.4,
(s, 3H) ppm. 13C NMR (400 MHz, CDCl3):
d
¼194.5,159.8,151.1, 149.3,
129.9, 129.4, 125.7, 125.0, 123.7, 123.8, 122.7, 122.3, 21.7 ppm. LC-MS
143.5, 139.5, 139.5, 138.8, 136.7, 133.3, 129.6, 125.8, 125.1, 123.7,
122.9, 122.9, 122.8, 122.3, 120.4, 113.0, 55.4 ppm. LCeMS (EI): m/z
calcd [Mþ1]þ¼346.1; found: 346.1.
(EI): m/z calcd [Mþ1]þ¼330.1; found: 330.1.
4.2.5. (4-Methoxyphenyl)(2-(pyridin-2-yl)benzo[b]thiophen-3-yl)
methanone (3c). Yellow solid. Mp 99e100 ꢀC. 1H NMR (400 MHz,
4.2.12. (2-Chlorophenyl)(2-(pyridin-2-yl)benzo[b]thiophen-3-yl)
CDCl3):
d¼8.54e8.53 (m, 1H), 7.91 (d, J¼8.0 Hz, 1H), 7.86 (d,
methanone (3j). Yellow oil. 1H NMR (400 MHz, CDCl3):
J¼8.0 Hz, 2H), 7.58 (d, J¼8.0 Hz, 1H), 7.54e7.51 (m, 1H), 7.46e7.44
(m, 1H), 7.39 (t, J¼8.0 Hz, 1H), 7.34e7.31 (m, 1H), 7.13e7.10 (m, 1H),
6.82 (d, J¼8.0 Hz, 2H), 3.80 (s, 3H) ppm. 13C NMR (400 MHz, CDCl3):
d
¼8.49e8.48 (m, 1H), 8.00e7.98 (m, 1H), 7.91e7.90 (m, 1H),
7.58e7.55 (m, 1H), 7.49e7.47 (m, 1H), 7.45e7.43 (m, 2H), 7.41 (d,
J¼8.0 Hz,1H), 7.29e7.26 (m,1H), 7.22e7.19 (m,1H), 7.09 (t, J¼4.0 Hz,
d
¼193.5, 164.0, 151.2, 149.4, 143.0, 139.7, 139.6, 136.6, 133.4, 132.2,
1H), 7.07e7.04 (m, 1H) ppm. 13C NMR (400 MHz, CDCl3):
d
¼191.5,
130.3, 125.6, 123.0, 123.6, 122.8, 122.6, 122.3, 113.9, 55.4 ppm.
150.8,149.0,147.0,139.2,139.1,138.3,136.5,133.5,133.2,132.1,131.4,
130.7, 126.3,125.9,125.6, 124.2, 123.9, 122.1, 122.2 ppm. LCeMS (EI):
m/z calcd [Mþ1]þ¼350.0; found: 350.0.
LCeMS (EI): m/z calcd [Mþ1]þ¼346.1; found: 346.1.
4.2.6. [1,10-Biphenyl](2-(pyridin-2-yl)benzo[b]thiophen-3-yl)meth-
anone (3d). White solid. Mp 134e135 ꢀC. 1H NMR (400 MHz,
4.2.13. (Naphthalen-2-yl)(2-(pyridin-2-yl)benzo[b]thiophen-3-yl)
CDCl3):
1H), 7.58e7.56 (m, 5H), 7.50e7.35 (m, 6H), 7.14e7.11 (m, 1H) ppm.
13C NMR (400 MHz, CDCl3):
139.6, 139.5, 136.9, 136.1, 133.5, 130.3, 128.9, 128.3, 127.2, 125.8,
125.2, 123.7, 123.0, 123.0, 122.4 ppm. LCeMS (EI): m/z calcd
[Mþ1]þ¼392.1; found: 392.1.
d
¼8.54 (d, J¼4.0 Hz, 1H), 7.95e7.93 (m, 3H), 7.67e7.65 (m,
methanone (3k). Yellow solid. Mp 100e102 ꢀC. 1H NMR (400 MHz,
CDCl3):
d¼8.43e8.41 (m, 1H), 8.16 (d, J¼8.0 Hz,1H), 7.88 (d, J¼8.0 Hz,
d¼194.3,150.9, 149.2, 146.1, 143.1, 139.6,
2H), 7.82e7.78 (m, 1H), 7.73e7.63 (m, 6H), 7.58e7.49 (m, 3H),
7.45e7.41(m,1H), 7.30e7.27(m,1H)ppm.13CNMR(400MHz,CDCl3):
d
¼193.2, 167.1, 150.4, 149.9, 143.3, 139.2, 139.1, 138.0, 136.6, 132.8,
132.5, 132.2, 131.8, 131.2, 130.5, 128.2, 127.4, 126.6, 126.1, 124.0, 123.4,
122.7 ppm. LCeMS (EI): m/z calcd [Mþ1]þ¼366.1; found: 366.1.
4.2.7. (4-Fluorophenyl)(2-(pyridin-2-yl)benzo[b]thiophen-3-yl)
methanone (3e). Yellow solid. Mp 169e170 ꢀC. 1H NMR (400 MHz,
4.2.14. (2-(Pyridin-2-yl)benzo[b]thiophen-3-yl)(thiophen-2-yl)meth-
CDCl3):
d¼8.60e8.58 (m, 1H), 7.93e7.91 (m, 1H), 7.77 (t, J¼8.0 Hz,
anone (3l). Yellow solid. Mp 47e49 ꢀC. 1H NMR (400 MHz, CDCl3):
1H), 7.68e7.65 (m, 2H), 7.62e7.60 (m, 1H), 7.49e7.48 (m, 1H),
7.45e7.41 (m, 1H), 7.32e7.28 (m, 1H), 7.25e7.24 (m, 1H), 7.00e7.98
d
¼8.58e8.57 (m, 1H), 7.91 (d, J¼8.0 Hz, 1H), 7.74 (d, J¼8.0 Hz, 1H),
7.64e7.57 (m, 2H), 7.54e7.52 (m, 1H), 7.44e7.36 (m, 3H), 7.18e7.15
(m, 1H) ppm. 13C NMR (400 MHz, CDCl3):
d
¼193.1, 165.9 (d,
(m, 1H), 6.93e6.91 (m, 1H) ppm. 13C NMR (400 MHz, CDCl3):
J¼254.0 Hz), 150.9, 149.3, 143.3, 139.4 (d, J¼17.0 Hz), 136.9, 134.0 (d,
J¼3.0 Hz), 133.0, 132.3 (d, J¼10.0 Hz), 125.9, 125.3, 123.6, 123.0,
122.9, 122.4, 115.9, 115.7 ppm. LCeMS (EI): m/z calcd
[Mþ1]þ¼334.1; found: 334.0.
d
¼186.6, 151.1, 149.4, 144.7, 143.8, 139.5, 139.3, 136.8, 135.4, 135.2,
132.8,128.3,125.8,125.1,123.6,123.0,123.0,122.3 ppm. LCeMS (EI):
m/z calcd [Mþ1]þ¼322.0; found: 322.0.
4.2.15. (Furan-2-yl)(2-(pyridin-2-yl)benzo[b]thiophen-3-yl)meth-
4.2.8. (4-Chlorophenyl)(2-(pyridin-2-yl)benzo[b]thiophen-3-yl)
anone (3m). Yellow solid. Mp 108e109 ꢀC. 1H NMR (400 MHz,
methanone (3f). White solid. Mp 129e130 ꢀC. 1H NMR (400 MHz,
CDCl3):
d¼8.58e8.57 (m, 1H), 7.91 (d, J¼8.0 Hz, 1H), 7.81 (d,
CDCl3):
d¼8.47e8.46 (m, 1H), 7.92 (d, J¼8.0 Hz, 1H), 7.80 (d,
J¼8.0 Hz, 1H), 7.61 (t, J¼8.0 Hz, 1H), 7.51e7.48 (m, 2H), 7.42e7.40
J¼8.0 Hz, 2H), 7.63e7.55 (m, 2H), 7.46e7.34 (m, 3H), 7.30 (d,
(m, 2H), 7.19e7.16 (m, 1H), 6.92e6.91 (m, 1H) ppm. 13C NMR
J¼8.0 Hz, 2H), 7.14e7.11 (m, 1H) ppm. 13C NMR (400 MHz, CDCl3):
(400 MHz, CDCl3):
d
¼180.8, 152.9, 151.2, 149.2, 147.5, 144.5, 139.5,
d
¼193.3, 150.8, 149.2, 143.2, 139.8, 139.5, 139.3, 137.0, 136.0, 132.9,
139.2, 137.1, 132.1, 125.9, 125.3, 123.6, 123.3, 123.1, 122.3, 121.0,
130.9,128.9,125.9,125.3,123.6,123.1,122.9,122.4 ppm. LCeMS (EI):
m/z calcd [Mþ1]þ¼350.0; found: 350.0.
112.5 ppm. LCeMS (EI): m/z calcd [Mþ1]þ¼306.1; found: 306.0.
4.2.16. Phenyl(2-(pyridin-2-yl)benzofuran-3-yl)methanone
4.2.9. (4-Bromophenyl)(2-(pyridin-2-yl)benzo[b]thiophen-3-yl)
(5a). Yellow solid. Mp 146e147 ꢀC. 1H NMR (400 MHz, CDCl3):
methanone (3g). White solid. Mp 102e103 ꢀC. 1H NMR (400 MHz,
d
¼8.43e8.42 (m, 1H), 7.90 (d, J¼8.0 Hz, 2H), 7.84 (d, J¼8.0 Hz, 1H),
CDCl3):
(m, 2H), 7.63e7.56 (m, 2H), 7.48e7.34 (m, 5H), 7.14e7.11 (m,
1H) ppm. 13C NMR (400 MHz, CDCl3):
139.5, 139.3, 136.9, 136.4, 132.9, 131.9, 131.0, 128.6, 125.9, 125.3,
123.6, 123.0, 122.8, 122.4 ppm. LCeMS (EI): m/z calcd
[Mþ1]þ¼394.0; found: 394.0.
d¼8.46 (d, J¼4.0 Hz, 1H), 7.92 (d, J¼8.0 Hz, 1H), 7.73e7.71
7.70e7.64 (m, 2H), 7.56e7.48 (m, 2H), 7.43e7.34 (m, 3H), 7.30e7.28
(m, 1H), 7.17e7.14 (m, 1H) ppm. 13C NMR (400 MHz, CDCl3):
d¼195.5, 150.8, 149.2, 143.3,
d
¼192.4, 154.3, 153.2, 149.6, 147.9, 138.0, 136.7, 133.1, 129.6, 128.4,
128.2, 126.2, 124.0, 123.5, 122.2, 121.4, 118.6, 111.7 ppm. LC-MS (EI):
m/z calcd [Mþ1]þ¼300.1; found: 300.1.
4.2.17. (2-(Pyridin-2-yl)benzofuran-3-yl)(p-tolyl)methanone
4.2.10. (3-Bromophenyl)(2-(pyridin-2-yl)benzo[b]thiophen-3-yl)
(5b). Yellow solid. Mp 105e106 ꢀC. 1H NMR (400 MHz, CDCl3):
methanone (3h). Yellow solid. Mp 117e119 ꢀC. 1H NMR (400 MHz,
d
¼8.50e8.49 (m, 1H), 7.86 (d, J¼8.0 Hz, 1H), 7.82 (d, J¼4.0 Hz, 2H),
CDCl3):
d¼8.44e8.43 (m, 1H), 8.04 (s, 1H), 7.92 (d, J¼8.0 Hz, 1H),
7.72e7.69 (m, 1H), 7.65 (d, J¼4.0 Hz, 1H), 7.49 (d, J¼4.0 Hz, 1H),
Please cite this article in press as: Gong, W.-J.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2014.12.095

6
W.-J. Gong et al. / Tetrahedron xxx (2015) 1e7
7.41e7.39 (m, 1H), 7.27e7.25 (m, 1H), 7.20e7.16 (m, 3H), 2.37 (s,
3H) ppm. 13C NMR (400 MHz, CDCl3):
147.7, 144.2, 137.0, 135.3, 129.8, 129.2, 128.2, 126.2, 123.9, 123.4,
122.2, 121.4, 119.1, 111.7, 21.7 ppm. LCeMS (EI): m/z calcd
[Mþ1]þ¼314.1; found: 314.1.
CDCl3):
d
¼8.46e8.45 (m, 1H), 7.83e7.81 (m, 1H), 7.70e7.63 (m, 2H),
d¼191.9, 154.2, 152.7, 149.3,
7.57e7.55 (m,1H), 7.52 (s,1H), 7.42e7.40 (m, 2H), 7.31e7.29 (m,1H),
7.23e7.15 (m, 2H), 7.06e7.04 (m, 1H) ppm. 13C NMR (400 MHz,
CDCl3):
d
¼192.1, 159.7, 154.2, 153.6, 149.5, 148.0, 139.3, 136.5, 129.3,
128.2, 126.1, 124.0, 123.4, 122.7, 122.1, 121.4, 120.0, 118.5, 113.0, 111.6,
55.4 ppm. LCeMS (EI): m/z calcd [Mþ1]þ¼330.1; found: 330.1.
4.2.18. (4-Methoxyphenyl)(2-(pyridin-2-yl)benzofuran-3-yl)meth-
anone (5c). Yellow solid. Mp 44e45 ꢀC. 1H NMR (400 MHz, CDCl3):
4.2.25. (2-Chlorophenyl)(2-(pyridin-2-yl)benzofuran-3-yl)meth-
d
¼8.53e8.52 (m, 1H), 7.91 (d, J¼4.0 Hz, 2H), 7.86 (d, J¼8.0 Hz, 1H),
anone (5j). Yellow oil. 1H NMR (400 MHz, CDCl3):
d¼8.44e8.43 (m,
7.73e7.69 (m, 1H), 7.65 (d, J¼8.0 Hz, 1H), 7.49 (d, J¼8.0 Hz, 1H), 7.40
(t, J¼8.0 Hz, 1H), 7.28e7.25 (m, 1H), 7.21e7.19 (m, 1H), 6.87e6.84
1H), 7.83 (d, J¼8.0 Hz, 1H), 7.79 (d, J¼4.0 Hz, 1H), 7.70e7.67 (m, 1H),
7.64 (d, J¼4.0 Hz, 1H), 7.47e7.46 (m, 1H), 7.43 (t, J¼4.0 Hz, 1H),
7.36e7.33 (m, 1H), 7.31e7.30 (m, 1H), 7.27e7.24 (m, 1H), 7.19e7.17
(m, 1H), 7.13 (t, J¼4.0 Hz, 1H) ppm. 13C NMR (400 MHz, CDCl3):
(m, 2H), 3.83 (s, 3H) ppm. 13C NMR (400 MHz, CDCl3):
d¼190.8,
163.8, 154.2, 152.4, 149.4, 147.8, 136.9, 132.1, 130.8, 128.3, 126.2,
123.9, 123.4, 121.3, 119.0, 113.7, 113.6, 111.7, 55.5 ppm. LCeMS (EI):
m/z calcd [Mþ1]þ¼330.1; found: 330.1.
d
¼190.6, 156.5, 154.3, 148.8, 147.4, 139.3, 136.7, 132.3, 131.6, 130.4,
130.2, 127.2, 126.4, 126.3, 124.5, 123.9, 123.6, 122.1, 119.3, 111.7 ppm.
LCeMS (EI): m/z calcd [Mþ1]þ¼334.1; found: 334.0.
4.2.19. [1,10-Biphenyl](2-(pyridin-2-yl)benzofuran-3-yl)methanone
(5d). Yellow solid. Mp 129e130 ꢀC. 1H NMR (400 MHz, CDCl3):
4.2.26. (Naphthalen-2-yl)(2-(pyridin-2-yl)benzofuran-3-yl)meth-
d
¼8.46e8.45 (m, 1H), 7.98 (d, J¼8.0 Hz, 2H), 7.87 (d, J¼8.0 Hz, 1H),
anone (5k). Yellow solid. Mp 116e118 ꢀC. 1H NMR (400 MHz,
7.71e7.64 (m, 2H), 7.59e7.56 (m, 5H), 7.45e7.37 (m, 4H), 7.31e7.25
CDCl3):
d
¼8.88e8.86 (m, 1H), 8.12e8.11 (m, 1H), 7.86 (d, J¼8.0 Hz,
(m, 1H), 7.17e7.14 (m, 1H) ppm. 13C NMR (400 MHz, CDCl3):
2H), 7.74e7.62 (m, 5H), 7.58e7.54 (m, 1H), 7.50e7.40 (m, 2H),
d
¼191.9, 154.2, 153.2, 149.4, 147.8, 145.7, 139.8, 136.8, 136.7, 130.2,
7.33e7.30 (m, 1H), 7.19 (t, J¼8.0 Hz, 1H), 7.00e6.97 (m, 1H) ppm. 13
C
128.9, 128.2, 127.2, 127.0, 126.2, 124.0, 123.5, 122.1, 121.4, 118.7,
NMR (400 MHz, CDCl3):
d¼193.8, 155.4, 154.2, 149.3, 147.9, 136.8,
111.7 ppm. LCeMS (EI): m/z calcd [Mþ1]þ¼376.1; found: 376.1.
136.1, 133.7, 132.5, 131.0, 129.4, 128.2, 128.18, 127.9, 126.4, 126.1,
126.1, 124.2, 124.1, 123.3, 122.4, 121.7, 120.4, 111.6 ppm. LCeMS (EI):
m/z calcd [Mþ1]þ¼350.1; found: 350.1.
4.2.20. (4-Fluorophenyl)(2-(pyridin-2-yl)benzofuran-3-yl)meth-
anone (5e). Yellow solid. Mp 151e152 ꢀC. 1H NMR (400 MHz,
CDCl3):
d
¼8.40e8.39 (m, 1H), 7.95e7.91 (m, 2H), 7.85 (d, J¼8.0 Hz,
4.2.27. (2-(Pyridin-2-yl)benzofuran-3-yl)(thiophen-2-yl)methanone
1H), 7.70 (t, J¼8.0 Hz, 1H), 7.63 (d, J¼8.0 Hz, 1H), 7.55 (d, J¼8.0 Hz,
(5l). Yellow solid, mp 133e134 ꢀC. 1H NMR (400 MHz, CDCl3):
1H), 7.41 (t, J¼8.0 Hz, 1H), 7.31e7.26 (m, 1H), 7.17e7.14 (m, 1H), 7.02
d
¼8.60e8.58 (m, 1H), 7.93e7.91 (m, 1H), 7.77 (t, J¼8.0 Hz, 1H),
(t, J¼8.0 Hz, 2H) ppm. 13C NMR (400 MHz, CDCl3):
d¼190.8,165.7 (d,
7.68e7.65 (m, 2H), 7.62e7.60 (m, 1H), 7.49e7.48 (m, 1H), 7.42e7.41
(m, 1H), 7.32e7.29 (m, 1H), 7.25e7.24 (m, 1H), 7.00e6.98 (m,
J¼253.0 Hz), 154.2, 153.4, 149.5, 147.8, 136.7, 134.5 (d, J¼3.0 Hz),
132.1 (d, J¼9.0 Hz), 128.1, 126.2,124.1, 123.5, 122.0, 121.2, 118.2, 115.5
(d, J¼22.0 Hz), 116.7 ppm. LCeMS (EI): m/z calcd [Mþ1]þ¼318.1;
found: 318.1.
1H) ppm. 13C NMR (400 MHz, CDCl3):
d¼184.0, 154.2, 152.5, 149.3,
147.5, 144.8, 137.3, 134.8, 134.7, 128.1, 127.9, 126.4, 124.1, 123.7, 122.4,
121.3, 119.0, 111.8 ppm. LCeMS (EI): m/z calcd [Mþ1]þ¼306.1;
found: 306.0.
4.2.21. (4-Chlorophenyl)(2-(pyridin-2-yl)benzofuran-3-yl)meth-
anone (5f). Yellow solid. Mp 160e162 ꢀC. 1H NMR (400 MHz,
4.2.28. Furan-2-yl(2-(pyridin-2-yl)benzofuran-3-yl)methanone
CDCl3):
d
¼8.37e8.36 (m, 1H), 7.87e7.83 (m, 3H), 7.70 (t, J¼8.0 Hz,
(5m). Yellow solid, mp 143e144 ꢀC. 1H NMR (400 MHz, CDCl3):
1H), 7.63 (d, J¼8.0 Hz, 1H), 7.55 (d, J¼8.0 Hz, 1H), 7.41 (t, J¼8.0 Hz,
d
¼8.1e8.49 (m,1H), 7.89 (d, J¼8.0 Hz,1H), 7.72 (t, J¼8.0 Hz,1H), 7.69
1H), 7.33e7.29 (m, 3H), 7.17e7.13 (m, 1H) ppm. 13C NMR (400 MHz,
(d, J¼8.0 Hz, 1H), 7.62 (d, J¼8.0 Hz, 1H), 7.47 (br s, 1H), 7.41 (t,
J¼8.0 Hz, 1H), 7.33e7.30 (m, 1H), 7.22e7.19 (m, 1H), 7.07e7.06 (m,
CDCl3):
d
¼191.2, 154.2, 153.6, 149.6, 147.9, 139.3, 136.5, 136.5, 130.8,
128.7, 128.1, 126.2, 124.1, 123.5, 121.8, 121.2, 117.9, 111.7 ppm. LCeMS
1H), 6.44 (br s,1H) ppm. 13C NMR (400 MHz, CDCl3):
d
¼178.9, 154.2,
(EI): m/z calcd [Mþ1]þ¼334.1; found: 334.0.
153.9, 153.2, 149.4, 148.0, 146.8, 136.9, 127.8, 126.2, 124.1, 123.5,
122.2, 121.3, 119.6, 117.8, 112.4, 111.7 ppm. LCeMS (EI): m/z calcd
[Mþ1]þ¼290.1; found: 290.0.
4.2.22. (4-Bromophenyl)(2-(pyridin-2-yl)benzofuran-3-yl)meth-
anone (5g). Yellow solid. Mp 147e149 ꢀC. 1H NMR (400 MHz,
CDCl3):
d
¼8.37 (br, 1H), 7.87e7.86 (m, 1H), 7.76 (d, J¼8.0 Hz, 2H),
Acknowledgements
7.71 (t, J¼4.0 Hz, 1H), 7.63 (d, J¼8.0 Hz, 1H), 7.56e7.55 (m, 1H), 7.59
(d, J¼8.0 Hz, 2H), 7.43e7.40 (m, 1H), 7.31e7.28 (m, 1H), 7.16 (t,
The authors thank the financial supports from the National
Natural Science Foundation of China (21171124, 21171125, and
21371126) and State Key Laboratory of Organometallic Chemistry,
Shanghai Institute of Organic Chemistry, Chinese Academy of Sci-
ences (2015kf-07). J.-P.L. highly appreciates the financial supports
from the Qin-Lan Project and the ‘333’ Project of Jiangsu Province,
the Priority Academic Program Development of Jiangsu Higher
Education Institutions, and the ‘SooChow Scholar’ Program of
Soochow University. The authors also thank the useful suggestions
of the editor and the reviewers.
J¼4.0 Hz, 1H) ppm. 13C NMR (400 MHz, CDCl3):
¼191.4, 154.3,
d
153.7, 149.6, 147.9, 137.0, 136.5, 131.7, 130.9, 128.1, 126.2, 124.1, 123.5,
121.7, 121.2, 117.8, 111.7 ppm. LCeMS (EI): m/z calcd [Mþ1]þ¼378.0;
found: 378.0.
4.2.23. (3-Bromophenyl)(2-(pyridin-2-yl)benzofuran-3-yl)meth-
anone (5h). Yellow solid. Mp 112e114 ꢀC. 1H NMR (400 MHz,
CDCl3):
d
¼8.38e8.36 (m, 1H), 8.05e8.04 (m, 1H), 7.88e7.86 (m, 1H),
7.76e7.70 (m, 2H), 7.65e7.58 (m, 3H), 7.45e7.41 (m, 1H), 7.33e7.26
(m, 1H), 7.22e7.15 (m, 2H) ppm. 13C NMR (400 MHz, CDCl3):
d
¼190.9, 154.3, 154.0, 149.4, 147.7, 140.0, 136.6, 135.7, 132.1, 129.9,
128.1, 128.0, 126.3, 124.2, 123.6, 122.6, 121.9, 121.2, 117.8, 111.7 ppm.
Supplementary data
LC-MS (EI): m/z calcd [Mþ1]þ¼378.0; found: 378.0.
The 1H and 13C NMR spectra for the isolated products. Supple-
mentary data associated with this article can be found in the online
version, at http://dx.doi.org/10.1016/j.tet.2014.12.095.
4.2.24. (3-Methoxyphenyl)(2-(pyridin-2-yl)benzofuran-3-yl)meth-
anone (5i). Yellow solid. Mp 103e104 ꢀC. 1H NMR (400 MHz,
Please cite this article in press as: Gong, W.-J.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2014.12.095

W.-J. Gong et al. / Tetrahedron xxx (2015) 1e7
7
9. (a) Fang, P.; Li, M. Z.; Ge, H. B. J. Am. Chem. Soc. 2010, 132, 11898; (b) Li, M. Z.; Ge,
H. B. Org. Lett. 2010, 12, 3464; (c) Miao, J.; Ge, H. B. Org. Lett. 2013, 15, 2930.
10. (a) Kim, M.; Park, J.; Sharma, S.; Kim, A.; Park, E.; Kwak, J. H.; Jung, Y. H.; Kim, I.
S. Chem. Commun. 2013, 925; (b) Park, J.; Kim, M.; Sharma, S.; Park, E.; Kim, A.;
Lee, S. H.; Kwak, J. H.; Jung, Y. H.; Kim, I. S. Chem. Commun. 2013, 1654; (c)
Sharma, S.; Kim, A.; Park, E.; Park, J.; Kim, M.; Kwak, J. H.; Lee, S. H.; Jung, Y. H.;
Kim, I. S. Adv. Synth. Catal. 2013, 355, 667; (d) Yang, Z. Y.; Chen, X.; Liu, J. D.; Gui,
Q. W.; Xie, K.; Li, M. M.; Tan, Z. Chem. Commun. 2013, 1560; (e) Li, H. J.; Li, P. H.;
Zhao, Q.; Wang, L. Chem. Commun. 2013, 9170; (f) Li, Z. Y.; Li, D. D.; Wang, G. W.
J. Org. Chem. 2013, 78, 10414; (g) Yao, J.; Feng, R.; Wu, Z.; Liu, Z.; Zhang, Y. Adv.
Synth. Catal. 2013, 355, 1517; (h) Wang, H.; Guo, L. N.; Duan, X. H. Org. Lett. 2012,
14, 4358; (i) Xu, B.; Liu, W.; Kuang, C. X. Eur. J. Org. Chem. 2014, 2576; (j) Ma, Y.
N.; Tian, Q. P.; Zhang, H. Y.; Zhou, A. X.; Yang, S. D. Org. Chem. Front. 2014, 1, 284.
11. (a) Yu, L.; Li, P. P.; Wang, L. Chem. Commun. 2013, 2368; (b) Wang, C. P.; Wang, S.
Y.; Li, H.; Yan, J. B.; Chi, H. J.; Chen, X. C.; Zhang, Z. Q. Org. Biomol. Chem. 2014, 12,
1721; (c) Pan, C. D.; Jin, H. M.; Liu, X.; Cheng, Y. Y.; Zhu, C. J. Chem. Commun.
2013, 2933; (d) Yang, K.; Zhang, C.; Wang, P.; Zhang, Y.; Ge, H. B. Chem.dEur. J.
2014, 20, 7241.
12. (a) Roger, J.; Gottumukkala, A. L.; Doucet, H. ChemCatChem 2010, 2, 20 and
references cited therein; (b) Tang, D.-T. D.; Collins, K. D.; Ernst, J. B.; Glorius, F.
Angew. Chem., Int. Ed. 2014, 53, 1809; (c) Wu, Y.; Wang, J.; Mao, F.; Kwong, F. Y.
Chem. Asian J. 2014, 9, 26; (d) Funaki, K.; Sato, T.; Oi, S. Org. Lett. 2012, 14, 6186;
(e) Biajoli, A. F. P.; Penha, E. T. d.; Correia, C. R. D. RSC Adv. 2012, 2, 11930.
13. (a) Pospech, J.; Tlili, A.; Spannenberg, A.; Neumann, H.; Beller, M. Chem.dEur. J.
2014, 20, 3135; (b) Zhao, J. C.; Fang, H.; Xie, C.; Han, J. L.; Li, G. G.; Pan, Y. Asian J.
Org. Chem. 2013, 2, 1044.
References and notes
1. (a) Dadiboyena, S. Eur. J. Med. Chem. 2012, 51, 17; (b) Waterman, P. G.;
Mohammad, I. J. Chem. Soc., Chem. Commun. 1984, 1280; (c) Matsumoto, K.;
Choshi, T.; Hourai, M.; Zamami, Y.; Sasaki, K.; Abe, T.; Ishikura, M.; Hatae, N.;
Iwamura, T.; Tohyama, S.; Nobuhiro, J.; Hibino, S. Bioorg. Med. Chem. Lett. 2012,
22, 4762; (d) Clive, D. L. J.; Cheng, P. Tetrahedron 2013, 69, 5067; (e) Cheng, P.;
Clive, D. L. J.; Fernandopulle, S.; Chen, Z. Chem. Commun. 2013, 558; (f) Yama-
naka, K.; Ryan, K. S.; Gulder, T. A. M.; Hughes, C. C.; Moore, B. S. J. Am. Chem. Soc.
2012, 134, 12434; (g) Nicolaou, K. C.; Simmons, N. L.; Chen, J. S.; Haste, N. M.;
Nizet, V. Tetrahedron Lett. 2011, 52, 2041; (h) Kanakis, A. A.; Sarli, V. Org. Lett.
2010, 12, 4872.
2. (a) Jiang, X.; Liu, W.; Zhang, W.; Jiang, F.; Gao, Z.; Zhuang, H.; Fu, L. Eur. J. Med.
Chem. 2011, 46, 3526; (b) Flynn, B. L.; Gill, G. S.; Grobelny, D. W.; Chaplin, J. H.;
Paul, D.; Leske, A. F.; Lavranos, T. C.; Chalmers, D. K.; Charman, S. A.; Kostewicz,
E.; Shackleford, D. M.; Morizzi, J.; Hamel, E.; Jung, M. K.; Kremmidiotis, G. J.
Med. Chem. 2011, 54, 6014.
3. Heel, R. C.; Brogden, R. N.; Speight, T. M.; Avery, G. S. Drugs 1977, 14, 349.
4. Mason, J. J. N. Engl. J. Med. 1987, 316, 455.
5. Balfour, J. A.; Goa, K. L. Drug Aging 1998, 12, 335.
6. (a) Ishiyama, T.; Kizaki, H.; Miyaura, N.; Suzuki, A. Tetrahedron Lett. 1993, 34,
7595; (b) Oda, K.; Machida, M. Chem. Pharm. Bull. 1993, 41, 1299; (c) Gallagher,
T.; Pardoe, D. A.; Porter, R. A. Tetrahedron Lett. 2000, 41, 5415; (d) Pal, S.; Khan,
M. A.; Bindu, P.; Dubey, P. Beilstein J. Org. Chem. 2007, 3, 35; (e) Leardini, R.;
Pedulli, G. F.; Tundo, A.; Zanardi, G. J. Chem. Soc., Chem. Commun. 1985, 1390; (f)
Basha, A.; Brooks, D. W. J. Org. Chem. 1993, 58, 1293.
7. (a) Mitsumori, S.; Tsuri, T.; Honma, T.; Hiramatsu, Y.; Okada, T.; Hashizume, H.;
Kida, S.; Inagaki, M.; Arimura, A.; Yasui, K. J. Med. Chem. 2003, 46, 2446; (b)
Gaertner, R. J. Am. Chem. Soc. 1952, 74, 2185.
14. (a) Liu, D. X.; Li, F. L.; Li, H. X.; Gong, W. J.; Gao, J.; Lang, J. P. Eur. J. Org. Chem.
2014, 4817; (b) Liu, D. X.; Li, F. L.; Li, H. X.; Gao, J.; Lang, J. P. Tetrahedron 2014,
70, 2416.
15. Zhuang, J.; Wang, C. Q.; Xie, F.; Zhang, W. B. Tetrahedron 2009, 65, 9797.
8. (a) Gooßen, L. J.; Rudolphi, F.; Oppel, C.; Rodríguez, N. Angew. Chem., Int. Ed.
2008, 47, 3043; (b) Li, M. Z.; Wang, C.; Ge, H. B. Org. Lett. 2011, 13, 2062.
Please cite this article in press as: Gong, W.-J.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2014.12.095