Highly efficient copper/palladium-catalyzed tandem Ullman reaction/arylation of azoles via C-H activation: Synthesis of benzofuranyl and indolyl azoles from 2-(gem-dibromovinyl)phenols(anilines) with azoles

Article abstract of DOI:10.1016/j.tet.2011.06.044

In this paper, a novel and highly efficient copper/palladium-catalyzed tandem intramolecular Ullman-type C-O(N) coupling reaction of 2-(gem-dibromovinyl)phenols(anilines) followed by an intermolecular arylation of azoles through C-H activation has been developed. In the presence of CuBr with Pd(PPh₃)₂Cl₂ used as co-catalyst, and LiO ^tBu as a base, the one-pot reactions of 2-(gem-dibromovinyl)phenols and 2-(gem-dibromovinyl)anilines with a variety of azoles, including oxazoles, imidazoles, thiazoles, and oxadiazoles underwent smoothly in toluene at 100 °C to generate the corresponding biheteroaryl products in high yields. A tentative mechanism of copper/palladium-catalyzed tandem reaction was described.

Full text of DOI:10.1016/j.tet.2011.06.044

Tetrahedron 67 (2011) 5913e5919
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Highly efficient copper/palladium-catalyzed tandem Ullman reaction/arylation
of azoles via CeH activation: synthesis of benzofuranyl and indolyl azoles from
2-(gem-dibromovinyl)phenols(anilines) with azoles
,b,
Wei Chen a, Min Wang a, Pinhua Li a, Lei Wang a
*
a Department of Chemistry, Huaibei Normal University, Huaibei, Anhui 235000, PR China
b State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 30 April 2011
Received in revised form 4 June 2011
Accepted 16 June 2011
Available online 22 June 2011
In this paper, a novel and highly efficient copper/palladium-catalyzed tandem intramolecular Ullman-
type CeO(N) coupling reaction of 2-(gem-dibromovinyl)phenols(anilines) followed by an in-
termolecular arylation of azoles through CeH activation has been developed. In the presence of CuBr
with Pd(PPh3)2Cl2 used as co-catalyst, and LiOtBu as a base, the one-pot reactions of 2-(gem-di-
bromovinyl)phenols and 2-(gem-dibromovinyl)anilines with a variety of azoles, including oxazoles,
imidazoles, thiazoles, and oxadiazoles underwent smoothly in toluene at 100 ꢀC to generate the corre-
sponding biheteroaryl products in high yields. A tentative mechanism of copper/palladium-catalyzed
tandem reaction was described.
Keywords:
Pd(PPh3)2Cl2
CuBr
Tandem reaction
gem-Dibromovinyl compounds
Azoles
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
catalyzed CeH functionalization of heterocycles, especially azoles
has received much attention in the most recent years.6
The heteroaryl azole skeletons are key structural units in nu-
merous biologically active natural products and unnatural syn-
thetic materials.1 Over the last few years, considerable attention
has been directed toward the synthesis and functionalization of
organic compounds containing the biheteroaryl structural units.2
Transition-metal-catalyzed reactions, especially the palladium-
catalyzed organic transformations in construction of carbone
carbon and carboneheteroatom bonds have increasingly attracted
attention in the pharmaceutical and fine chemical industries.3 In
general, these carbonecarbon biheteroaryl linkages are achieved
via transition-metal-catalyzed cross-coupling reactions of hetero-
aryl halides or pseudohalides with heteroaryl organometallic re-
agents,4 which rank as the most powerful biheteroaryl formation
reactions in organic synthesis. However, reactivation of hetero-
aromatic carbon fragments with metal-containing functionalities
and halides may involve several tedious synthetic steps. Direct
transition-metal-catalyzed functionalization of CeH bonds in het-
erocycles has received extraordinary attention in modern organic
chemistry owing to its environmentally benign features and atom
economy,5 and transition metals, such as Pd-, Cu-, Co-, Ni-, and Mn-
Compared with the traditional multiple step synthesis, tandem/
domino reactions could enhance the efficiency of preparing the
target products from simple starting materials, avoid the separation
of intermediates, save the number of steps, and reduce the amount
of pollutant waste emission. Moreover, the versatility of the catalyst
system can also be exploited through different types of reactions
occurring in one-pot. So, most of the recently reported methodol-
ogies were based on the use of this type reactions.7 The versatility
of gem-dihaloolefins, owing to higher reactivity and easy accessi-
bility from inexpensive aldehydes, has been exploited,8 notably, as
a key unit for the synthesis of various heterocycles, such as indoles,9
benzothiophenes,10 benzofurans,11,9i,10b isocoumarins,12 and other
heterocycles13 through metal-catalyzed tandem Ullman-type or
SuzukieMiyaura coupling/amination, Suzuki, Sonogashira, Heck,
or intramolecular CeH activation. It is desirable to develop
the tandem reactions of gem-dihaloolefins with azoles through
an intermolecular CeH activation to generate biheteroaryl
compounds.14
Herein, we wish to report a mild and highly efficient copper/
palladium-catalyzed tandem reaction of intramolecular Ullman-
type CeO(N) coupling reaction of 2-(gem-dibromovinyl)phenols
and 2-(gem-dibromovinyl)anilines followed by a intermolecular
arylation of azoles through CeH activation. The reactions of
2-(gem-dibromovinyl)phenols and 2-(gem-dibromovinyl)anilines
* Corresponding author. Tel.: þ86 561 3802 069; fax: þ86 561 3090 518; e-mail
address: leiwang@chnu.edu.cn (L. Wang).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.06.044

5914
W. Chen et al. / Tetrahedron 67 (2011) 5913e5919
with a variety of azoles including oxazoles, imidazoles, thiazoles,
and oxadiazoles underwent smoothly in the presence of
Pd(PPh3)2Cl2/CuBr/LiOtBu in toluene, and generated the corre-
sponding benzofuranyl and indolyl azoles in high yields. This one-
pot sequential process provides a wide range of substrate applica-
bility, which is commercially available and easily prepared from
aromatic aldehydes, and in most cases, nearly quantitative yields
were obtained (Scheme 1).
examined, and the reaction with dppf, dppe, or PPh3 used a ligand
produced 3a in comparable yield over 97%. Meanwhile, P(tBu)3, and
P(Cy)3 delivered inferior yields to those of dppf, dppe, and PPh3
(Table 1, entries 5, and 11e14). Of particular note is the use of
phosphine-free conditions, which greatly simplifies the reaction
work-up procedure and avoids phosphine ligand emission, and
gratifyingly, 96% of the desired tandem reaction product 3a was
isolated (Table 1, entry 15). However, it should be noted that when
Pd(PPh3)2Cl2 was used as catalyst without CuBr, or CuBr/PPh3 was
used as catalyst without Pd(PPh3)2Cl2, the reaction generated
biheteroaryl product 3a only in 24% or 38% yield (Table 1, entries 16
and 17). Unfortunately, no desired product 3a was obtained when
the reaction was catalyzed by CuBr in the absence of Pd(PPh3)2Cl2
and PPh3 (Table 1, entry 18).
The choice of base was also important and several bases for the
model reaction. LiOtBu was found to be the most effective one, and
the desired product 3a was generated in 96% isolated yield (Table 2,
entry 1). Other bases, such as KF, (iPr)2NH, K3PO4, Cs2CO3, DABCO,
Et3N, and KOtBu were substantially less effective (Table 2, entries
2e8).
Scheme 1.
2. Results and discussion
Initially, 2-(gem-dibromovinyl)phenol (1a) and benzoxazole
(2a) were chosen as the model substrates for surveying parameters
of the reaction condition, and the results were listed in Table 1.
When the model substrates were carried out in the presence of CuI
(10 mol %), Pd(OAc)2 (5 mol %), and PPh3 (10 mol %) with LiOtBu
used as a base in toluene at significantly milder reaction temper-
ature of 100 ꢀC for 10 h, to our delight, 2-(benzofuran-2-yl)ben-
zoxazole (3a) was obtained in 41% yield (Table 1, entry 1). By
screening the other palladium sources, such as PdCl2, Pd/C, and
Pd(PPh3)Cl2, it was revealed that Pd(PPh3)2Cl2 was the most ef-
fective one, affording the desired biheteroaryl product 3a in 73%
yield (Table 1, entries 2e4). When the copper source was switched
to CuBr, the desired product 3a was isolated in nearly quantitative
yield (98%, Table 1, entry 5). Other sources of the copper salt [e.g.,
CuCl, Cu2O, Cu(OAc)2, CuO, and Cu powder] were greatly inferior to
CuBr (Table 1, entries 6e10). Subsequently, several phosphine
ligands, such as P(tBu)3, P(Cy)3, PPh3, dppf, and dppe were
Table 2
Effect of base and solvent on the model reactiona
Br
CuBr (10 mol% )
Pd(PPh3)2Cl2 (5 mol%)
N
O
N
O
Br
+
base (4 equiv), solvent
100 oC, 10 h
O
OH
1a
3a
2a
Entry
Base
Solvent
Yield (%)b
1
2
3
4
5
6
7
8
LiOtBu
KF
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
DMF
96
74
47
42
37
33
25
15
34
42
52
77
(iPr)2NH
K3PO4
Cs2CO3
DABCO
Et3N
KOtBu
LiOtBu
LiOtBu
LiOtBu
LiOtBu
9
10
11
12
DCE
THF
1,4-Dioxane
Table 1
Effect of Pd, Cu sources and ligand on the model reactiona
a
Reaction conditions: 2-(gem-dibromovinyl)phenol 1a (0.50 mmol), benzoxazole
2a (0.50 mmol), CuBr (0.05 mmol), Pd(PPh3)2Cl2 (0.025 mmol), LiOtBu (2.0 mmol) in
toluene (2.0 mL) at 100 ꢀC for 10 h.
Br
N
O
N
O
[Cu] and/or [Pd]
Br
+
b
t
Isolated yields.
LiOBu (4 equiv), toluene
O
OH
1a
100 oC, 10 h
3a
2a
The solvent also plays an important role in the model tandem
reaction. Several solvents, such as DMF, DCE, THF, 1,4-dioxane, and
toluene were examined, and toluene was proved to be the most
efficient medium for the reaction (Table 2, entries 9e12 and 1).
Thus, the optimized reaction conditions for this tandem reaction
are CuBr (10 mol %) and Pd(PPh3)2Cl2 (5 mol %) with LiOtBu
(4 equiv) used as a base in toluene at 100 ꢀC for 10 h.
Under the above optimized reaction conditions, various
substituted 2-(gem-dibromovinyl)phenols and azoles, including
oxazoles, imidazoles, and thiazoles were used as substrates to
examine the generality of the reaction (Table 3). In the most of
cases, the expected biheteroaryl products were isolated in good to
excellent yields (Table 3, entries 1e9 and 11e13). 2-(gem-Dibro-
movinyl)phenol, substituted 2-(gem-dibromovinyl)phenols, such
as 4-chloro-2-(gem-dibromovinyl)phenol, 4,6-dichloro-2-(gem-
dibromovinyl)phenol, and 1-(2,2-dibromovinyl)-2-naphthalenol
reacted with benzoxazole smoothly under the present reaction
conditions to afford the corresponding products 3aed in 88e96%
yields (Table 3, entries 1e4). Benzoxazoles with both electron-
donating (5-Me, 6-Me) and electron-withdrawing (5-Cl, 6-Cl)
groups on the benzene rings, reacted with 2-(gem-dibromovinyl)
Entry
Pd Source
Cu Source
Ligand
Yield (%)b
1
2
3
4
5
6
7
8
Pd(OAc)2
PdCl2
Pd/C
CuI
CuI
CuI
CuI
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
P(tBu)3
P(Cy)3
dppf
dppe
d
41
35
21
73
98
47
35
44
22
28
62
88
98
97
96
24
38
NR
Pd(PPh3)Cl2
Pd(PPh3)Cl2
Pd(PPh3)Cl2
Pd(PPh3)Cl2
Pd(PPh3)Cl2
Pd(PPh3)Cl2
Pd(PPh3)Cl2
Pd(PPh3)Cl2
Pd(PPh3)Cl2
Pd(PPh3)Cl2
Pd(PPh3)Cl2
Pd(PPh3)Cl2
Pd(PPh3)Cl2
d
CuBr
CuCl
Cu2O
Cu(OAc)2
CuO
Cu powder
CuBr
CuBr
CuBr
CuBr
CuBr
d
9
10
11
12
13
14
15
16
17
18
d
CuBr
CuBr
PPh3
d
d
a
Reaction conditions: 2-(gem-dibromovinyl)phenol 1a (0.50 mmol), benzoxazole
2a (0.50 mmol), [Cu] (0.05 mmol), [Pd] (0.025 mmol), ligand (0.05 mmol), LiOtBu
(2.0 mmol) in toluene (2.0 mL) at 100 ꢀC for 10 h.
b
Isolated yields.

W. Chen et al. / Tetrahedron 67 (2011) 5913e5919
5915
Table 3
Scope of benzoxazoles, benzimidazoles, and benzothiazolesa
phenol or 4-chloro-2-(gem-dibromovinyl)phenol completely and
87e95% yields of the desired products 3eei were isolated (Table 3,
entries 5e9). It was worth noting that the present reaction
conditions were also suitable for the tandem reaction of benz-
imidazole, N-alkyl benzimidazoles, and N-aryl benzimidazoles
with 2-(gem-dibromovinyl)phenol. The results indicated that the
corresponding benzofuranyl benzimidazole derivatives 3jem
were obtained in 70e91% yields (Table 3, entries 10e13). It is
obvious that N-alkyl(aryl) benzimidazoles displayed higher re-
activity than that of benzimidazole (Table 3, entries 11e13 vs 10).
Notably, benzothiazole reacted with 2-(gem-dibromovinyl)phenol
and the expected product 3n was formed in 66% yield (Table 3,
entry 14).
To further extend the scope of azoles, the tandem Ullman re-
action of 2-(gem-dibromovinyl)phenol/arylation of azoles via CeH
activation of 1,3,4-oxadiazole derivatives were investigated, as
shown in Table 4. Various 2-aryl-1,3,4-oxadiazoles with either
electron-donating or electron-withdrawing groups on their ben-
zene rings displayed high reactivity to 2-(gem-dibromovinyl)phe-
nol and 4-chloro-2-(gem-dibromovinyl)phenol under the
optimized reaction conditions. The corresponding biheteroaryl
products 5aeg were obtained in excellent yields (Table 4, entries
1e7). The results also showed that the electronic and steric effect of
substituted groups on benzene rings had little impact on the yields
of the products.
Br
CuBr (10 mol% )
N
N
Pd(PPh3)2Cl2 (5 mol%)
R2
R2
R1
R1
+
Br
t
LiOBu (4 equiv), toluene
O
Y
Y
100 oC, 10 h
OH
3
2
1
Y = O, NH, NR, S
Entry
1
Product (3)
Yield (%)b
96
N
O
3a
3b
O
Cl
N
2
3
94
90
O
O
N
Cl
3c
O
O
Cl
N
O
4
3d
88
O
H3C
H3C
N
5
6
7
3e
3f
89
91
87
O
O
N
O
Table 4
The scope of 2-aryl-1,3,4-oxadiazolesa
Br
CuBr (10 mol% )
O
N
N
N
N
Pd(PPh3)2Cl2 (5 mol%)
Br
+
t
LiOBu (4 equiv), toluene
O
O
O
R3
R3
Cl
100 oC, 10 h
OH
N
O
4
5
1a
3g
O
H3C
Cl
Entry
Product (5)
Yield (%)b
95
N
N
N
8
3h
3i
93
95
70
1
2
3
4
5a
O
O
O
N
O
O
O
N
N
9
5b
5c
5d
92
86
94
Cl
Cl
O
O
N
N
N
10
3j
O
N
H
H3CO
H3C
O
O
N
N
N
11
12
13
3k
3l
83
91
O
N
O
O
C2H5
N
N
N
N
5
6
5e
90
O
O
O
H3C
CH2C6H5
N
N
N
3m
3n
87
66
5f
91
87
O
N
O
O
C6H5
CH3
Cl
N
S
N
N
14
7
5g
O
O
O
a
a
Reaction conditions: 2(gem-dibromovinyl)phenol (0.50 mmol), azole
(0.50 mmol), CuBr (0.05 mmol), Pd(PPh3)2Cl2 (0.025 mmol), LiOtBu (2.0 mmol) in
toluene (2.0 mL) at 100 ꢀC for 10 h.
Reaction conditions: 2-(gem-dibromovinyl)phenol (0.50 mmol), 1,3,4-
oxadiazole (0.50 mmol), CuBr (0.05 mmol), Pd(PPh3)2Cl2 (0.025 mmol), LiOtBu
(2.0 mmol) in toluene (2.0 mL) at 100 ꢀC for 10 h.
b
b
Isolated yields.
Isolated yields.

5916
W. Chen et al. / Tetrahedron 67 (2011) 5913e5919
Having developed a highly efficient procedure for the synthesis
When the tandem reaction was performed in the absence of
CuBr under the optimized conditions, only 24% yield of the product
was obtained. On the other hand, when the reaction was performed
in the absence of Pd(PPh3)2Cl2 without additional ligand, no de-
sired product was obtained. In addition, 1a could transform to 2-
bromobenzofuran (III) in nearly quantitative yield in the absence
of 2a under the present reaction conditions, but, no any 2-(bro-
moethynyl)phenol (VII) was detected. Presumably, the formation of
III was through an intramolecular Ullman reaction process. When
2a was added the above reaction system for additional 7 h under
same reaction conditions in one-pot, as expected, 3a was obtained
in 95% yield (Scheme 4). A prepared 2-bromobenzofuran (III) from
1a,10b could stoichiometrically transform to 3a under the present
conditions in the absence of CuBr (Scheme 4), which offered a fur-
ther proof for this proposed mechanism. On the basis of this evi-
dence, we believe that the Cu-catalyzed CeO coupling process
occurs prior to the Pd-catalyzed arylation of azole via CeH activa-
tion in this sequence.
of benzofuranyl azoles from 2-(gem-dibromovinyl)phenols and
azoles, we next expanded the scope of this methodology to 2-(gem-
dibromovinyl)anilines with azoles. Fortunately, the tandem Ullman
reaction 2-(gem-dibromovinyl)aniline, followed by arylation of
benzoxazole and 2-phenyl-1,3,4-oxadiazole proceeded well under
the present reaction conditions, affording the corresponding
indolyl azoles 6a and 6b in 93% and 84% yields, respectively
(Scheme 2).
Scheme 2. The reactions of 2-(gem-dibromovinyl)aniline with azoles.
A proposed mechanism of copper/palladium-catalyzed tandem
reaction through CeH activation was shown in Scheme 3. The re-
action occurs probably involving (1) an intramolecular Ullman-type
reaction of 2-(gem-dibromovinyl)phenol (1a), affording 2-
bromobenzofuran (III), and (2) an intermolecular arylation of
benzoxazole (2a) with obtained III through CeH activation,
affording biheteroaryl product 2-(benzofuran-2-yl)benzoxazole
(3a). Firstly, in the intramolecular classic Ullman reaction of 1a
catalyzed by CuIBr,15 1a reacted with CuIBr to form an intermediate
I through oxidative addition with the assistance of PPh3 as ligand
from the dissociation of Pd(PPh3)2Cl2. Then the obtained I un-
derwent an intramolecular transmetallation to generate II, which
followed by a reductive elimination to afford 2-bromobenzofuran
(III) and regenerate the CuIBr for next run. Subsequently, in the
intermolecular arylation of 2a with III catalyzed by Pd0 from its
precursor Pd(PPh3)2Cl2, 1a reacted with Pd0 to form intermediate
IV via oxidative addition. Then, IV reacted with V, which was
generated from the deprotonation of 2a by LiOtBu, and followed by
a transmetalation to generate intermediate VI. Finally, 3a was
produced via reductive elimination and Pd0 was regenerated to
complete this catalytic cycle.
Scheme 4.
3. Conclusions
In conclusion, we have developed a general, highly efficient
one-pot protocol for the synthesis of benzofuranyl and indolyl
azoles through a copper/palladium-catalyzed tandem reaction of
intramolecular Ullman-type CeO(N) coupling reaction of 2-(gem-
dibromovinyl)phenols and 2-(gem-dibromovinyl)anilines followed
by an intermolecular arylation of azoles through their CeH acti-
vation. The reactions of 2-(gem-dibromovinyl)phenols and
2-(gem-dibromovinyl)anilines with a variety of azoles including
oxazoles, imidazoles, thiazoles, and oxadiazoles underwent
smoothly in the presence of CuBr with Pd(PPh3)2Cl2 used as
co-catalyst, and LiOtBu as a base in toluene at 100 ꢀC for 10 h, and
the corresponding products were generated in high yields. This
reaction utilizes easily accessible gem-dibromovinyl substrates
and azoles, and provides a straightforward route to diverse
biheteroaryl compounds. Further investigation on the application
of this kind of catalyst system in organic synthesis is underway in
our laboratory.
4. Experimental
4.1. General methods
All reactions were carried out under nitrogen atmosphere. All
reagents were purchased from commercial suppliers and used after
further purification. 1H NMR, 13C NMR spectra were measured on
a Bruker Avance NMR spectrometer (400 MHz or 100 MHz, re-
spectively) with CDCl3 or DMSO-d6 as solvent and recorded in ppm
relative to internal tetramethylsilane standard. High resolution
mass spectroscopy data of the product were collected on a Waters
Micromass GCT instrument.
Scheme 3. Possible mechanism of Cu/Pd-catalyzed tandem reaction.

W. Chen et al. / Tetrahedron 67 (2011) 5913e5919
5917
4.2. General procedure for the synthesis of benzofuranyl and
indolyl azoles from 2-(gem-dibromovinyl)phenols and 2-
(gem-dibromovinyl)anilines with azoles
IR (KBr, cmꢁ1): 3022, 2921, 1637, 1248, 1160, 1065; HRMS (ESI)
([M]þ) calcd for C16H11NO2: 249.0790, found: 249.0795.
4.3.7. Compound 3g. White solid; mp 184e186 ꢀC; 1H NMR
Under the nitrogen atmosphere, an over-dried Schlenk tube
with a magnetic stirring bar was charged with 2-(gem-dibromo-
vinyl)phenol or 2-(gem-dibromovinyl)aniline (0.50 mmol), azole
(0.50 mmol), CuBr (0.05 mmol), Pd(PPh3)2Cl2 (0.025 mmol), LiOtBu
(2.0 mmol), and toluene (2.0 mL). The reaction vessel was placed in
an oil bath at 100 ꢀC and the mixture was stirred for 10 h, then it
was cooled to room temperature. The solvent was filtered and
concentrated under reduced pressure, and the residue was purified
by flash chromatography on silica gel (eluant: hexane/ethyl acetate)
to give the corresponding benzofuranyl or indolyl azole product.
(400 Hz, CDCl3):
d
¼7.68e7.65 (m, 2H), 7.55 (d, J¼8.8 Hz, 1H), 7.48 (s,
1H), 7.39e7.35 (m, 2H), 7.21 (d, J¼8.4 Hz, 1H), 2.52 (s, 3H); 13C NMR
(100 Hz, CDCl3):
d
¼154.3, 154.0, 150.7, 145.1, 139.3, 136.8, 129.5,
128.9, 127.0, 126.5, 121.6, 120.0, 113.0, 110.8, 108.9, 21.9; IR (KBr,
cmꢁ1): 3095, 2917, 1635, 1435, 1325, 1123, 1066; HRMS (ESI) ([M]þ)
calcd for C16H10NO2Cl: 283.0400, found: 283.0402.
4.3.8. Compound 3h. White solid; mp 179e181 ꢀC; 1H NMR
(400 Hz, CDCl3):
J¼8.4 Hz, 1H), 7.61 (s, 1H), 7.51 (d, J¼8.4 Hz, 1H), 7.45 (t, J¼7.6 Hz,
1H), 7.36e7.31 (m, 2H); 13C NMR (100 Hz, CDCl3):
148.9, 143.0, 142.7, 130.5, 127.3, 127.2, 126.0, 124.0, 122.3, 120.3,
112.1, 111.4, 110.9; IR (KBr, cmꢁ1): 3078, 2923, 1637, 1582, 1442,
1203, 1066; HRMS (ESI) ([M]þ) calcd for C15H8NO2Cl: 269.0244,
found: 269.0239.
d¼7.76 (s, 1H), 7.70 (d, J¼7.6 Hz, 1H), 7.64 (d,
d
¼156.5, 155.9,
4.3. Characterization data of benzofuranyl and indolyl azoles
4.3.1. Compound 3a. Pale yellow solid; mp 171e173 ꢀC; 1H NMR
(400 Hz, CDCl3):
d
¼7.83e7.80 (m, 1H), 7.69 (d, J¼7.6 Hz, 1H), 7.64 (d,
J¼8.4 Hz, 1H), 7.61e7.59 (m, 2H), 7.45e7.37 (m, 3H), 7.31 (t,
4.3.9. Compound 3i. White solid; mp 168e170 ꢀC; 1H NMR
J¼8.0 Hz, 1H); 13C NMR (100 Hz, CDCl3):
d¼155.8, 155.3, 150.3,
(400 Hz, CDCl3):
d
¼7.72e7.70 (m, 2H), 7.66e7.61 (m, 3H), 7.46 (t,
143.5, 141.5, 127.5, 126.9, 125.8, 125.0, 123.9, 122.2, 120.4, 112.0,
110.7, 110.3; IR (KBr, cmꢁ1): 3112, 3028, 1637, 1597, 1439, 1343, 1242,
1066; HRMS (ESI) ([M]þ) calcd for C15H9NO2: 235.0633, found:
235.0635.
J¼7.2 Hz, 1H), 7.37 (dd, J¼8.4, 1.6 Hz, 1H), 7.34 (t, J¼7.6 Hz, 1H); 13C
NMR (100 Hz, CDCl3):
d¼155.9, 155.9, 150.6, 143.1, 140.4, 131.4,
127.4, 127.2, 125.8, 124.0, 122.3, 120.9, 112.1, 111.3, 110.7; IR (KBr,
cmꢁ1): 3105, 2923, 1637, 1501, 1453, 1259, 1065; HRMS (ESI) ([M]þ)
calcd for C15H8NO2Cl: 269.0244, found: 269.0245.
4.3.2. Compound 3b. White solid; mp 193e195 ꢀC; 1H NMR
(400 Hz, CDCl3):
d
¼7.81e7.79 (m, 1H), 7.65 (d, J¼2.0 Hz, 1H),
4.3.10. Compound 3j. Pale yellow solid; mp 112e114 ꢀC; 1H NMR
7.60e7.58 (m, 1H), 7.55e7.51 (m, 2H), 7.40e7.35 (m, 3H); 13C NMR
(400 Hz, CDCl3):
d
¼8.42 (s, 1H), 7.91 (d, J¼7.6 Hz, 1H), 7.81 (d,
(100 Hz, CDCl3):
d
¼154.7, 154.1, 150.4, 144.9, 141.4, 129.6, 128.8,
J¼8.0 Hz, 1H), 7.66 (d, J¼7.2 Hz, 1H), 7.58 (d, J¼7.6 Hz, 1H), 7.44 (t,
127.1, 126.1, 125.2, 121.6, 120.6, 113.0, 110.7, 109.4; IR (KBr, cmꢁ1):
3096, 2921, 1630, 1584, 1439, 1158, 1061; HRMS (ESI) ([M]þ) calcd
for C15H8NO2Cl: 269.0244, found: 269.0246.
J¼8.0 Hz, 2H), 7.36 (t, J¼7.6 Hz, 2H), 6.76 (s, 1H); 13C NMR (100 Hz,
CDCl3):
d
¼151.7, 145.8, 143.7, 140.7, 132.1, 128.0, 124.6, 124.6, 123.9,
123.7,121.0,120.9,111.4,111.1, 92.9; IR (KBr, cmꢁ1): 3134, 2923,1627,
1494, 1224,1012; HRMS (ESI) ([M]þ) calcd for C15H10N2O: 234.0793,
found: 234.0790.
4.3.3. Compound 3c. White solid; mp 190e192 ꢀC; 1H NMR
(400 Hz, CDCl3):
d
¼7.85 (dd, J¼6.4, 2.4 Hz, 1H), 7.65e7.63 (m, 1H),
7.60e7.58 (m, 2H), 7.46e7.42 (m, 3H); 13C NMR (100 Hz, CDCl3):
4.3.11. Compound 3k. White solid; mp 137e139 ꢀC; 1H NMR
d
¼154.2, 150.5, 150.3, 145.8, 141.5, 129.8, 129.8, 126.9, 126.3, 125.3,
(400 Hz, CDCl3):
d
¼7.87 (d, J¼7.2 Hz, 1H), 7.72 (d, J¼8.0 Hz, 1H), 7.63
120.7, 120.2, 118.2, 110.9, 109.8; IR (KBr, cmꢁ1): 3069, 2922, 1574,
1441, 1292, 1160, 1072; HRMS (ESI) ([M]þ) calcd for C15H7NO2Cl2:
302.9854, found: 302.9852.
(d, J¼8.0 Hz, 1H), 7.54 (s, 1H), 7.46e7.39 (m, 2H), 7.36e7.32 (m, 3H),
4.67 (q, J¼7.2 Hz, 2H), 1.59 (t, J¼7.2 Hz, 3H); 13C NMR (100 Hz,
CDCl3):
d
¼155.1, 147.0, 143.4, 143.2, 135.4, 127.9, 125.7, 123.6, 123.4,
122.9, 121.8, 120.1, 111.6, 109.5, 108.4, 40.1, 15.5; IR (KBr, cmꢁ1):
2926, 2359, 1642, 1457, 1390, 1262; HRMS (ESI) ([M]þ) calcd for
C17H14N2O: 262.1106, found: 262.1107.
4.3.4. Compound 3d. Pale yellow solid; mp 166e167 ꢀC; 1H NMR
(400 Hz, CDCl3):
d
¼8.21 (d, J¼8.0 Hz, 1H), 8.10 (s, 1H), 7.98 (d,
J¼8.0 Hz, 1H), 7.88e7.82 (m, 2H), 7.78 (d, J¼9.2 Hz, 1H), 7.69e7.63
(m, 2H), 7.56 (t, J¼7.2 Hz, 1H), 7.43e7.40 (m, 2H); 13C NMR (100 Hz,
4.3.12. Compound 3l. White solid; mp 156e158 ꢀC; 1H NMR
(400 Hz, CDCl3):
(d, J¼8.0 Hz, 1H), 7.40 (s, 1H), 7.37e7.27 (m, 8H), 7.21e7.20 (m, 2H),
5.81 (s, 2H); 13C NMR (100 Hz, CDCl3):
136.2,136.1,128.9,127.8,127.8,126.3,125.8,123.7,123.6,123.1,121.8,
120.2, 111.6, 110.1, 108.6, 48.5; IR (KBr, cmꢁ1): 3061, 2922, 1641,
1595, 1437, 1257, 1167, 1072; HRMS (ESI) ([M]þ) calcd for
C22H16N2O: 324.1263, found: 324.1264.
CDCl3):
d¼155.4, 154.0, 150.4, 143.0, 141.7, 130.6, 129.0, 128.3, 127.6,
d¼7.92 (d, J¼8.4 Hz, 1H), 7.65 (d, J¼7.6 Hz, 1H), 7.57
127.1, 125.7, 125.4, 125.0, 123.4, 123.3, 120.3, 112.5, 110.7, 109.3; IR
(KBr, cmꢁ1): 3054, 2922, 1634, 1586, 1448, 1243, 1159; HRMS (ESI)
([M]þ) calcd for C19H11NO2: 285.0790, found: 285.0787.
d
¼155.1, 146.5, 144.1, 143.2,
4.3.5. Compound 3e. White solid; mp 142e144 ꢀC; 1H NMR
(400 Hz, CDCl3):
7.61e7.58 (m, 2H), 7.49e7.42 (m, 2H), 7.33 (t, J¼7.6 Hz, 1H),
7.25e7.19 (m, 1H), 2.50 (s, 3H); 13C NMR (100 Hz, CDCl3):
155.4, 148.6, 143.8, 141.8, 135.0, 127.5, 127.0, 126.8, 123.8, 122.2,
120.3, 112.0, 110.0, 109.9, 21.5; IR (KBr, cmꢁ1): 3061, 2922, 1641,
1595, 1437, 1167, 1072; HRMS (ESI) ([M]þ) calcd for C16H11NO2:
249.0790, found: 249.0794.
d
¼7.71 (d, J¼7.6 Hz, 1H), 7.65 (d, J¼8.4 Hz, 1H),
d
¼155.7,
4.3.13. Compound 3m. White solid; mp 143e145 ꢀC; 1H NMR
(400 Hz, CDCl3):
d¼7.96 (d, J¼8.0 Hz,1H), 7.68e7.65 (m, 3H), 7.57 (d,
J¼8.0 Hz, 1H), 7.48e7.46 (m, 3H), 7.39e7.27 (m, 3H), 7.22 (t,
J¼7.2 Hz, 1H), 7.14 (d, J¼8.0 Hz, 1H), 6.36 (s, 1H); 13C NMR (100 Hz,
CDCl3):
d
¼154.9, 145.8, 143.9, 142.9, 137.5, 136.2, 130.1, 129.7, 128.0,
127.7, 125.9, 124.1, 123.3, 123.3, 121.6, 120.3, 111.8, 110.3, 108.1; IR
(KBr, cmꢁ1): 3060, 2924, 1643, 1497, 1422, 1265; HRMS (ESI) ([M]þ)
calcd for C21H14N2O: 310.1106, found: 310.1105.
4.3.6. Compound 3f. White solid; mp 150e152 ꢀC; 1H NMR
(400 Hz, CDCl3):
2H), 7.33e7.29 (m, 1H), 7.20e7.18 (dd, J¼8.0, 0.4 Hz, 1H), 2.50 (s,
3H); 13C NMR (100 Hz, CDCl3):
¼155.7, 154.8, 150.7, 143.7, 139.4,
136.4, 127.5, 126.7, 126.3, 123.8, 122.1, 119.7, 112.0, 110.8, 109.7, 21.8;
d¼7.70e7.63 (m, 3H), 7.56 (s, 1H), 7.44e7.39 (m,
d
4.3.14. Compound 3n. Yellow solid; mp 216e218 ꢀC; 1H NMR
(400 Hz, CDCl3):
d
¼8.14 (d, J¼7.6 Hz, 1H), 7.95 (d, J¼8.0 Hz, 1H), 7.70

5918
W. Chen et al. / Tetrahedron 67 (2011) 5913e5919
(d, J¼7.6 Hz,1H), 7.64 (d, J¼7.6 Hz,1H), 7.55e7.53 (m, 2H), 7.46e7.41
1168, 1069; HRMS (ESI) ([M]þ) calcd for C16H9N2O2Cl: 296.0353,
found: 296.0355.
(m, 2H), 7.32 (t, J¼7.6 Hz, 1H); 13C NMR (100 Hz, CDCl3):
¼157.6,
d
155.5, 153.8, 149.7, 128.1, 126.7, 126.6, 126.5, 125.7, 123.8, 123.5,
122.1,121.7,111.9,107.6; IR (KBr, cmꢁ1): 3115, 3051,1586,1439,1243,
1152, 1004; HRMS (ESI) ([M]þ) calcd for C15H9NOS: 251.0405,
found: 251.0407.
4.3.22. Compound 6a. White solid; mp 167e169 ꢀC; 1H NMR
(400 Hz, DMSO-d6):
d
¼12.34 (s, 1H), 7.80e7.76 (m, 2H), 7.68 (d,
J¼8.0 Hz, 1H), 7.50 (d, J¼8.4 Hz, 1H), 7.42e7.40 (m, 2H), 7.34 (s, 1H),
7.27e7.24 (m, 1H), 7.11e7.07 (m, 1H); 13C NMR (100 Hz, DMSO-d6):
4.3.15. Compound 5a. White solid; mp 146e148 ꢀC; 1H NMR
d
¼157.9, 150.4, 141.9, 138.4, 127.9, 125.8, 125.4, 124.8, 124.7, 122.0,
(400 Hz, CDCl3):
d
¼8.16 (d, J¼6.8 Hz, 2H), 7.71 (d, J¼7.6 Hz, 1H),
120.8, 119.9, 112.8, 111.2, 105.9; IR (KBr, cmꢁ1): 3035, 1626, 1577,
1444, 1335, 1235, 1169; HRMS (ESI) ([M]þ) calcd for C15H10N2O:
234.0793, found: 234.0789.
7.64 (d, J¼8.4 Hz, 1H), 7.58e7.53 (m, 4H), 7.45 (t, J¼7.6 Hz, 1H), 7.33
(t, J¼7.6 Hz, 1H); 13C NMR (100 Hz, CDCl3):
¼164.5, 157.7, 155.7,
d
140.6, 132.0, 129.1, 127.2, 127.1, 127.1, 124.0, 123.3, 122.3, 112.0,
110.1; IR (KBr, cmꢁ1): 3068, 1632, 1548, 1484, 1442, 1176, 1075;
HRMS (ESI) ([M]þ) calcd for C16H10N2O2: 262.0742, found:
262.0746.
4.3.23. Compound 6b. White solid; mp 154e157 ꢀC; 1H NMR
(400 Hz, DMSO-d6):
(m, 4H), 7.50 (d, J¼8.0 Hz, 1H), 7.33 (s, 1H), 7.29e7.25 (m, 1H),
7.13e7.09 (m, 1H); 13C NMR (100 Hz, DMSO-d6):
d¼12.34 (s, 1H), 8.14e8.12 (m, 2H), 7.70e7.64
d
¼163.8, 159.8,
4.3.16. Compound 5b. White solid; mp 175e177 ꢀC; 1H NMR
138.3, 132.5, 129.9, 127.8,127.1,124.8, 123.7, 122.0, 121.5, 120.9, 112.7,
105.6; IR (KBr, cmꢁ1): 3191, 2923, 1609, 1477, 1342, 1187; HRMS
(ESI) ([M]þ) calcd for C16H11N3O: 261.0902, found: 261.0900.
(400 Hz, CDCl3):
d
¼8.13 (d, J¼8.4 Hz, 2H), 7.74 (d, J¼7.6 Hz, 1H), 7.66
(d, J¼8.0 Hz,1H), 7.61 (s, 1H), 7.55 (d, J¼8.4 Hz, 2H), 7.48 (t, J¼7.6 Hz,
1H), 7.37 (t, J¼7.6 Hz, 1H); 13C NMR (100 Hz, CDCl3):
¼163.7, 157.8,
d
155.7, 140.3, 138.3, 129.5, 128.3, 127.2, 127.1, 124.1, 122.3, 121.7, 112.0,
110.4; IR (KBr, cmꢁ1): 3088, 1633, 1481, 1439, 1181, 1095, 1011;
HRMS (ESI) ([M]þ) calcd for C16H9N2O2Cl: 296.0353, found:
296.0354.
Acknowledgements
We gratefully acknowledge the financial support by the National
Natural Science Foundation of China (No. 20972057, 21002039).
4.3.17. Compound 5c. White solid; mp 164e166 ꢀC; 1H NMR
Supplementary data
(400 Hz, CDCl3):
d
¼8.12 (d, J¼8.8 Hz, 2H), 7.72 (d, J¼8.0 Hz,1H), 7.65
(d, J¼8.4 Hz, 1H), 7.56 (s, 1H), 7.46 (t, J¼7.6 Hz, 1H), 7.35 (t, J¼7.6 Hz,
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tet.2011.06.044. These data in-
clude MOL files and InChIKeys of the most important compounds
described in this article.
1H), 7.05 (d, J¼8.8 Hz, 2H), 3.91 (s, 3H); 13C NMR (100 Hz, CDCl3):
d
¼164.5, 162.5, 157.3, 155.6, 140.7, 128.9, 127.2, 126.9, 124.0, 122.2,
115.7,114.5,112.0,109.7, 55.4; IR (KBr, cmꢁ1): 3123,1642,1500,1437,
1262, 1177, 1016; HRMS (ESI) ([M]þ) calcd for C17H12N2O3:
292.0848, found: 292.0852.
References and notes
4.3.18. Compound 5d. White solid; mp 151e153 ꢀC; 1H NMR
1. (a) Keay, B. A.; Hopkins, J. M.; Dibble, P. W. In Comprehensive Heterocyclic
Chemistry III; Jones, G., Ramsden, C. A., Eds.; Elsevier: Amsterdam, 2008; Vol. 3,
pp 571e623; (b) Guzow, K.; Szmigiel, D.; Wroblewski, D.; Milewska, M.; Kar-
(400 Hz, CDCl3):
7.64 (d, J¼8.4 Hz, 1H), 7.56 (s, 1H), 7.45 (t, J¼7.2 Hz, 1H), 7.35e7.32
(m, 3H), 2.44 (s, 3H); 13C NMR (100 Hz, CDCl3):
d¼8.05 (d, J¼8.0 Hz, 2H), 7.71 (d, J¼7.6 Hz, 1H),
ꢀ
olczak, J.; Wiczk, W. J. Photochem. Photobiol., A 2007, 187, 87e96; (c) Szabelski,
M.; Rogiewicz, M.; Wiczk, W. Anal. Biochem. 2005, 342, 20e27; (d) Campiani, G.;
Butini, S.; Trotta, F.; Fattorusso, C.; Catalanotti, B.; Aiello, F.; Gemma, S.; Nacci,
V.; Novellino, E.; Stark, J.; Cagnotto, A.; Fumagalli, E.; Carnovali, F.; Cervo, L.;
Mennini, T. J. Med. Chem. 2003, 46, 3822e3839; (e) Hayashi, S.; Hirao, A.; Imai,
A.; Nakamura, H.; Murata, Y.; Ohashi, K.; Nakata, E. J. Med. Chem. 2009, 52,
610e625; (f) Dogan, H. N.; Duran, A.; Rollas, S.; Sener, G.; Uysal, M. K.; Gulen, D.
Bioorg. Med. Chem. 2002, 10, 2893e2898.
d¼164.7, 157.5,
155.6, 142.7, 140.6, 129.8, 127.2, 127.0, 127.0, 124.0, 122.2, 120.5,
112.0, 109.9, 21.6; IR (KBr, cmꢁ1): 3116, 1623, 1490, 1437, 1250,
1172, 1082; HRMS (ESI) ([M]þ) calcd for C17H12N2O2: 276.0899,
found: 276.0901.
2. (a) Thompson, M. J.; Adams, H.; Chen, B. J. Org. Chem. 2009, 74, 3856e3865; (b)
Shi, B.; Blake, A.; Campbell, I. B.; Judkins, B. D.; Moody, C. J. Chem. Commun.
2009, 3291e3294; (c) Da, Y.-X.; Yang, Z.; Quan, Z.-J.; Zhang, Z.; Wang, X.-C. J.
Heterocycl. Chem. 2009, 46, 737e741.
3. Tsuji, J. Palladium Reagents and Catalysis, New Perspective for the 21st Century;
Wiley-VCH: Weinheim, Germany, 2004.
4.3.19. Compound 5e. White solid; mp 115e117 ꢀC; 1H NMR
(400 Hz, CDCl3):
(d, J¼7.6 Hz, 1H), 7.55 (s, 1H), 7.45e7.39 (m, 2H), 7.36e7.30 (m, 2H),
2.44 (s, 3H); 13C NMR (100 Hz, CDCl3):
d
¼7.96e7.93 (m 2H), 7.69 (d, J¼7.6 Hz, 1H), 7.63
d
¼164.6, 157.6, 155.6, 140.5,
4. (a) Metal-Catalyzed Cross-Coupling Reactions; Diederich, F., Stang, P. J., Eds.;
138.9, 132.8, 128.9, 127.5, 127.1, 127.0, 124.1, 123.9, 123.0, 122.2,
112.0, 110.0, 21.2; IR (KBr, cmꢁ1): 3143, 1627, 1545, 1470, 1437, 1172,
1075; HRMS (ESI) ([M]þ) calcd for C17H12N2O2: 276.0899, found:
276.0902.
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Wiley-VCH: New York, NY, 1998; (b) Hassan, J.; Sevignon, M.; Gozzi, C.; Schulz,
€
E.; Lemaire, M. Chem. Rev. 2002, 102, 1359e1470; (c) Schnurch, M.; Flasik, R.;
Khan, A. F.; Spina, M.; Mihovilovic, M. D.; Stanetty, P. Eur. J. Org. Chem. 2006,
3283e3307; (d) Strotman, N. A.; Chobanian, H. R.; He, J.; Guo, Y.; Dormer, P. G.;
Jones, C. M.; Steves, J. E. J. Org. Chem. 2010, 75, 1733e1739.
5. For recent reviews, see: (a) Miura, M.; Satoh, T. In Handbook of CeH Trans-
formations; Dyker, G., Ed.; Wiley-VCH: Weinheim, 2005; Vol. 1, p 229; (b) Ac-
kermann, L.; Vicente, R. In Modern Arylation Methods; Ackermann, L., Ed.;
Wiley-VCH: Weinheim, 2009; p 311; (c) Bellina, F.; Rossi, R. Tetrahedron 2009,
65, 10269e10310; (d) McGlacken, G. P.; Bateman, L. M. Chem. Soc. Rev. 2009, 38,
2447e2464; (e) Seregin, I. V.; Gevorgyan, V. Chem. Soc. Rev. 2007, 36,
1173e1193; (f) Alberico, D.; Scott, M. E.; Lautens, M. Chem. Rev. 2007, 107,
174e238; (g) Campeau, L.-C.; Fagnou, K. Chem. Commun. 2006, 1253e1264; (h)
Ackermann, L.; Althammer, A. Angew. Chem., Int. Ed. 2007, 46, 1627e1629; (i)
4.3.20. Compound 5f. White solid; mp 111e113 ꢀC; 1H NMR
(400 Hz, CDCl3):
(d, J¼7.6 Hz, 1H), 7.55 (s, 1H), 7.43 (t, J¼7.6 Hz, 2H), 7.37e7.30 (m,
3H), 2.77 (s, 3H); 13C NMR (100 Hz, CDCl3):
d
¼8.05 (d, J¼7.6 Hz, 1H), 7.69 (d, J¼7.6 Hz, 1H), 7.63
d¼164.6, 157.1, 155.5,
140.5, 138.6, 131.7, 131.4, 128.9, 127.1, 126.9, 126.1, 123.9, 122.2, 122.1,
111.9, 110.0, 22.1; IR (KBr, cmꢁ1): 3063, 1623, 1538, 1440, 1172, 1046;
HRMS (ESI) ([M]þ) calcd for C17H12N2O2: 276.0899, found:
276.0898.
€
Ackermann, L.; Barfusser, S.; Pospech, J. Org. Lett. 2010, 12, 724e726; (j) Zhao,
D.; Wang, W.; Yang, F.; Lan, J.; Yang, L.; Gao, G.; You, J. Angew. Chem., Int. Ed.
2009, 48, 3296e3300; (k) Kawano, T.; Yoshizumi, T.; Hirano, K.; Satoh, T.;
Miura, M. Org. Lett. 2009, 11, 3072e3075; (l) Candito, D. A.; Lautens, M. Angew.
Chem., Int. Ed. 2009, 48, 6713e6716.
4.3.21. Compound 5g. White solid; mp 193e195 ꢀC; 1H NMR
6. (a) Zhao, X.; Wu, G.; Zhang, Y.; Wang, J. J. Am. Chem. Soc. 2011, 133, 3296e3299;
(b) Kitahara, M.; Umeda, N.; Hirano, K.; Satoh, T.; Miura, M. J. Am. Chem. Soc.
2011, 133, 2160e2162; (c) Kawano, T.; Hirano, K.; Satoh, T.; Miura, M. J. Am.
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Chem., Int. Ed. 2011, 50, 2178e2182; (e) Zhang, L.; Cheng, J.; Ohishi, T.; Hou, Z.
(400 Hz, CDCl3):
4H), 7.53 (s, 1H), 7.42e7.39 (m, 1H); 13C NMR (100 Hz, CDCl3):
¼164.7, 157.3, 154.0, 141.9, 132.2, 129.7, 129.2, 128.5, 127.4, 127.1,
123.1,121.7,113.1,109.4; IR (KBr, cmꢁ1): 3097,1623,1542,1432,1313,
d
¼8.16 (d, J¼6.8 Hz, 2H), 7.69 (s, 1H), 7.60e7.54 (m,
d

W. Chen et al. / Tetrahedron 67 (2011) 5913e5919
5919
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Angew. Chem., Int. Ed. 2010, 49, 8670e8673; (f) Kim, J. Y.; Cho, S. H.; Joseph, J.;
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J. C. Angew. Chem., Int. Ed. 2010, 49, 2282e2285; (i) Hachiya, H.; Hirano, K.;
Satoh, T.; Miura, M. Angew. Chem., Int. Ed. 2010, 49, 2202e2205; (j) Xi, P.-H.;
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7. (a) Tietze, L.-F.; Brasche, G.; Gericke, K. Domino Reactions in Organic Synthesis;
Wiley-VCH: Weinheim, 2006; (b) Ho, T.-L. Tandem Organic Reactions; Wiley-
Interscience: New York, NY, 1992; (c) Fogg, D. E.; Santos, E. N. Coord. Chem. Rev.
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driguez, S.; Qu, B.; Farina, V.; Senanayake, C. H.; Lu, B. Z. Org. Lett. 2006, 8,
3573e3575; (f) Chen, Y.; Xie, X.; Ma, D. J. Org. Chem. 2007, 72, 9329e9334; (g)
Ohta, Y.; Chiba, H.; Oishi, S.; Fujii, N.; Ohno, H. Org. Lett. 2008, 10, 3535e3538;
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