Silver-catalyzed oxidative coupling of aniline and ene carbonyl/acetylenic carbonyl compounds: An efficient route for the synthesis of quinolines

Article abstract of DOI:10.1002/asia.201402742

An efficient silver-mediated coupling of aniline with ene carbonyl/acetylenic carbonyl compounds for the synthesis of quinolines is reported. The transformation is effective for a broad range of substrates, thus enabling the expansion of substituent architectures on the heterocyclic framework. The electronic properties of the substituents on the amine have been investigated. It was found that molecules with both electron-donating and electron-withdrawing substituents were suitable substrates for this transformation, and the expected products were obtained in moderate to excellent yields. The use of a single catalytic system to mediate chemical transformations in a synthetic operation is important for the development of new atom-economic strategies and this strategy is efficient in building complex structures from simple starting materials in an environmentally benign fashion.

Full text of DOI:10.1002/asia.201402742

COMMUNICATION
DOI: 10.1002/asia.201402742
Silver-Catalyzed Oxidative Coupling of Aniline and Ene Carbonyl/Acetylenic
Carbonyl Compounds: An Efficient Route for the Synthesis of Quinolines
Xu Zhang* and Xuefeng Xu[a]
Abstract: An efficient silver-mediated coupling of aniline
with ene carbonyl/acetylenic carbonyl compounds for the
synthesis of quinolines is reported. The transformation is ef-
fective for a broad range of substrates, thus enabling the ex-
pansion of substituent architectures on the heterocyclic
framework. The electronic properties of the substituents on
the amine have been investigated. It was found that mole-
cules with both electron-donating and electron-withdrawing
substituents were suitable substrates for this transformation,
and the expected products were obtained in moderate to ex-
cellent yields. The use of a single catalytic system to mediate
chemical transformations in a synthetic operation is impor-
tant for the development of new atom-economic strategies
and this strategy is efficient in building complex structures
from simple starting materials in an environmentally benign
fashion.
nilic acids and ketones (or aldehydes) to form g-hydroxyqui-
noline derivatives.[7]
Strikingly, since 2005 there has been an unusual increment
in the number of reported procedures describing the con-
struction of quinolines that have a variety of functional
groups at different positions. Chen and co-workers discov-
ered a reversal in the standard regiochemistry of the
Skraup–Doebner–Von Miller quinoline synthesis when ani-
lines were condensed with g-aryl-b,g-unsaturated a-ketoest-
ers in refluxing trifluoroacetic acid (TFA).[8] Perumal and
co-workers demonstrated that phosphotungstic acid was an
effective catalyst for the Doebner–Miller quinaldine and
lepidine synthesis.[9] Bose and Kumar were also able to suc-
cessfully achieve the microwave-assisted synthesis of quino-
line and dihydroquinoline derivatives under solvent-free
conditions by Skraup synthesis.[10] Korivi and Cheng devel-
oped an efficient and convenient Ni-catalyzed cyclization of
2-iodoanilines with alkynyl aryl ketones to give 2,4-disubsti-
tuted quinolines.[11] The Pd-catalyzed approach to quinolines
from 2-iodoanilines was also described by Cho and Kim.[12]
Recently, Zhu and co-workers have reported a silver-
based system for the synthesis of quinolines through an oxi-
dative coupling/cyclization of N-arylimines and alkynes.[13]
The cross-coupling reactions can lead to an improved over-
all efficiency of the desired transformation. Thus, AgI is
a versatile reagent for oxidative coupling reactions in organ-
ic chemistry.[14] However, silver has received increased atten-
tion in organic synthesis by virtue of its expanding reactivity
patterns that have been discovered.[15] Generally, AgI re-
agents act as soft Lewis acids, and they preferentially coordi-
nate with soft Lewis bases, such as alkynes and allenes. The
activated alkynes or allenes become susceptible to be at-
tacked by various nucleophiles, such as alcohols, nitrogen,
carbon nucleophiles, carboxylic acids, ketones, and thiols.
Among the carbon nucleophiles, aromatic rings have unique
properties and have received attentions recently.[16] Al-
though there have been significant developments to obtain
several quinoline derivatives, different synthetic routes are
known to suffer from various problems, such as harsh condi-
tions, multiple steps, a large amount of promoters such as
a base, expensive and/or harmful metals, the oxidants for
the aromatization,[17] and the substrate availability, cost, stoi-
chiometric amount of additives, and functional group toler-
ance are limitations of the current methods for quinoline
synthesis. So, a simple and novel method for synthesizing
The quinoline moiety with different functional groups is
an important building block in the synthesis of various natu-
ral products. It has shown a broad range of biological activi-
ties and potential pharmaceutical applications.[1] Therefore,
the synthesis of substituted quinolines has been a subject of
great focus in organic chemistry.
To the best of our knowledge, there are seven main meth-
ods for the syntheses of quinoline: 1) The Combes synthesis
using anilines and b-diketones,[2] 2) the Conrad–Limpach
synthesis employing anilines and b-ketoesters,[3] 3) the
Doebner–Miller reaction involving anilines and a,b-unsatu-
rated carbonyl compounds;[4] 4) the Friexlꢀnder synthesis
using 2-aminobenzaldehyde and acetaldehyde,[5] 5) the Po-
varov reaction, which involves aniline, a benzaldehyde, and
an activated alkene (also known as the Aza-Diels–Alder re-
action),[6] 6) the Camps quinoline synthesis using 2-acylami-
noacetophenone and hydroxide ion, and the 7) the Niemen-
towski quinoline synthesis, which is the reaction of anthra-
[a] Dr. X. Zhang, X. Xu
School of Chemistry and Pharmacony Engineering
Nanyang Normal University
Wolong Wolong District, Nanyang City, Henan Province Road No.
1638
Fax : (+86)037763513540
E-mail: zhangxuedu@126.com
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/asia.201402742.
Chem. Asian J. 2014, 9, 3089 – 3093
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Xu Zhang and Xuefeng Xu
Table 1. Optimization of reaction conditions.[a]
quinoline and its derivatives is highly desirable and has
practical applications.
Herein, we wish to report on the synthesis of quinoline
derivatives by a AgOTf-mediated coupling reaction between
aniline with ene carbonyl/acetylenic carbonyl compounds
(Scheme 1). The starting materials are readily available
Entry
Catalyst
Additives
Solvent
Temp [o C]
Yield [%][b]
1
2
3
4
5
6
7
8
AgOTf
AgOTf
AgOTf
HOTf
HOTf
Toluene 80
Toluene 110
Toluene 110
Toluene 110
62
94
67
42
HOTf
HOTf
HOTf
HOTf
HOTf
CF3COOH
HCl
H2SO4
HOTf
HOTf
HOTf
AgOTf
AgOTf
AgOTf
AgOTf
AgOTf
AgOTf
AgOTf
Ag2CO3
Ag2SO4
AgCl
THF
MeOH
CCl4
80
60
80
48
NR[c]
NR
NR
74
H2O
100
9
Toluene 110
Toluene 110
Toluene 110
Toluene 110
Toluene 110
Toluene 110
Toluene 110
Toluene 110
10
11
12
13
14
15
16
NR
NR
82
NR
NR
46
Scheme 1. AgOTf-catalyzed aniline with ene carbonyl/acetylenic carbonyl
compounds.
Pd
ACHTUNGRTENN(UNG OAc)2 HOTf
PdCl2
HOTf
NR
from commercial vendors, and synthetically useful quinoline
derivatives were prepared in excellent yields. This strategy is
efficient in building complex structures from simple starting
materials in an environmentally benign fashion.
[a] Reaction conditions: amine (1.0 mmol), 1,3-diphenyl-propenone
(1.0 mmol), AgOTf (5 mmol%), HOTf (5 mmol%) under atmospheric
conditions. [b] Yields after silica-gel chromatography. [c] NR=no reac-
tion.
We initially performed the reaction of the amine
(1.0 mmol), 1,3-diphenylpropenone (1.0 mmol), in the pres-
ence of AgOTf (5 mmol%) and the additive HOTf
(5 mmol%) in toluene under atmospheric conditions. We
were pleased to find that the reaction in toluene at 808C for
4 h afforded the desired product with a yield of 62%
(Table 1, entry 1). Importantly, when the temperature was
raised to 1108C, the yield was increased to 94% for 4 h
(Table 1, entry 2). When the reaction was carried out in the
absence of AgOTf or HOTf, the yield decreased significant-
ly; this shows that AgOTf and HOTf are essential in the
course of the reaction (Table 1, entries 3 and 4). Solvent op-
timization revealed that other solvents (MeOH, CCl4, and
H2O) are non-operative and no products could be isolated
(Table 1, entries 5–7). When the additive was replaced by
TFA, the yield dropped to 74% for 4 h, thus emphasizing
the important role played by the counterion. No reactions
occurred when the additive was changed to other acids such
as HCl and H2SO4 (Table 1, entries 10 and 11), and the cata-
lyst was change to Ag2SO4 or AgCl (Table 1, entries 13 and
14). When Ag2CO3 was used as the catalyst the product was
obtained in moderate yield, the reason may be that Ag2CO3
and HOTf could generate the catalyst AgOTf. Following
these general conditions, we then examined the scope of this
reaction, and the results are summarized in Scheme 2.
With these optimized conditions in hand, the substrate
scope of the reaction was explored with a range of amines
with acrolein. Under our optimized conditions, substrates
with electron-donating or electron-withdrawing groups or
electron-neutral substituents were successfully transformed
into the corresponding quinolines (3a–d) in good yields
(Scheme 2). When acrolein was changed to phenylacrolein,
the yield somewhat improved (3e–k). A fluorine substituent
Scheme 2. Examples of quinoline derivatives synthesis. Reaction condi-
tions: amine (1.0 mmol), ene carbonyl compound (1.0 mmol), AgOTf
(5 mmol%), HOTf (5 mmol%) under atmospheric conditions. Yields
given after silica-gel chromatography.
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Xu Zhang and Xuefeng Xu
on the aryl of the amine (3h and 3j) was tolerated in this
transformation. In the case of 3j, lower yield was obtained;
this might be attributed to the electronic properties of the
substituent on the amine. With these encouraging results in
hand, we decided to further probe the reaction scope by em-
ploying enones. To our delight, all the substrates employed
afforded the corresponding quinolines (3l–t) in high yields
(Scheme 2). Amines with either an electron-donating or
electron-withdrawing character were able to give good
yields between 76–94% (Scheme 2). But the electronic
properties of the substituents on the amine exert certain in-
fluence on the yields. Lower yields were generally observed
for substrates with electron-withdrawing substituents as
compared with those with electron-donating substituents.
The broad scope of quinoline formation was demonstrated
by using amines with a variety of substituents, such as ortho-
À
À
À
À
substituents ( OC2H5), meta-substituents ( Me, F, Cl),
À
À
À
À
and para-substituents ( Me, OMe, F, and NO2), which
could afford good yields, as shown in Scheme 2. Finally, we
note that the acrylic acid ethyl ester also afforded the quino-
line products. However, the acrylic acid ethyl ester could
not react with amine under the standard reaction conditions.
Next, when the ene carbonyl compounds were replaced
by acetylenic carbonyl compounds, the desired products
were also obtained. However, it should be noted that when
the temperature was lowered to 808C, the yield greatly im-
proved. To show the synthetic utility of this method, a varie-
ty of amines were treated with propiolaldehyde, propiolic
acid ethylester, and alkynyl ketones under the optimized
conditions. Amines with either an electron-donating or elec-
tron-withdrawing character were able to give good yields be-
tween 76–94% (Scheme 3). But the electronic properties of
the substituents on the amine exert certain influence on the
yields. Lower yields were generally observed for substrates
with electron-withdrawing substituents as compared with
those with electron-donating substituents.
Scheme 3. Examples of quinoline derivatives synthesis. Reaction condi-
tions: amine (1.0 mmol), acetylenic carbonyl compound (1.0 mmol),
AgOTf (5 mmol%), HOTf (5 mmol%) under atmospheric conditions.
Yields given after silica-gel chromatography.
To explain how the silver system catalyzes the present
quinoline reaction, we propose the mechanism as shown in
Scheme 4. Firstly, the amine reacts with the C=O double
bond to generate an imine intermediate B and C, then the
silver salt serves as a Lewis acid to activate the double or
triple bond, and then nucleophilic attack and final oxidation
by air to generate the corresponding cyclization product. To
examine the silver salt could activate double or triple bond,
the imine intermediate B and C could get the corresponding
quinoline products under the standard reaction conditions
(Scheme 5, Equations (1) and (2)), thereby offering evi-
dence for the possibility of the pathway that the keto group
first undergoes condensation with the C=O double bond to
form an imine intermediate. However, it should be noted
that when the reaction was carried out under an atmosphere
of argon, the reaction was unsuccessful (Scheme 5, Equa-
tions (3) and (4)), as no quinoline products were formed;
this indicates that the final oxidation by air to generate the
corresponding cyclization product is essential.[18]
Scheme 4. Postulated reaction mechanism.
bonyl compounds has been reported. The transformation is
effective for a broad range of substrates, thus enabling the
expansion of substituent architectures on the heterocyclic
framework. The use of a single catalytic system to mediate
chemical transformations in a synthetic operation is impor-
tant for the development of new atom-economic strategies.
We found that this strategy is efficient in building complex
structures from simple starting materials in an environmen-
tally benign fashion. Simultaneously, the strategy reported
herein should be generally applicable to the coupling
chemistry with other functional partners. The diverse mech-
anistic manifolds implemented by using a single experimen-
tal protocol indicate the importance of stringent reactivity
analysis of each individual potentially reactive molecular
site.
In conclusion, a silver-based system for the synthesis of
quinolines between amines and ene carbonyl/acetylenic car-
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Xu Zhang and Xuefeng Xu
[1] a) P. Narender, U. Srinivas, M. Ravinder, B. A. Rao, C. Ramesh, K.
Harakishore, B. Gangadasu, U. S. N. Murthy, V. J. Rao, Bioorg. Med.
Chem. 2006, 14, 4600; b) M. Kidwai, K. R. Bhushan, P. Sapra, R. K.
Saxena, R. Gupta, Bioorg. Med. Chem. 2000, 8, 69; c) X. Franck, A.
Fournet, E. Prina, R. Mahieux, R. Hocquemiller, B. Figadere,
Bioorg. Med. Chem. Lett. 2004, 14, 3635; d) A. A. Joshi, S. S. Nar-
khede, C. L. Viswanathan, Bioorg. Med. Chem. Lett. 2005, 15, 73;
e) G. S. Dow, M. L. Koenig, L. Wolf, L. Gerena, M. Lopez-Sanchez,
T. H. Hudson, A. K. Bhattacharjee, Antimicrob. Agents Chemother.
2004, 48, 2624; f) C. Portela, C. M. M. Afonso, M. M. M. Pinta, M.
Ramos, Bioorg. Med. Chem. 2004, 12, 3313; g) A. Nayyar, A. Malde,
R. Jain, E. Coutinho, Bioorg. Med. Chem. 2006, 14, 847; h) A.
Nayyar, R. Jain, Curr. Med. Chem. 2006, 12, 1873; i) S. Rossiter,
J. M. Peron, P. J. Whitfield, K. Jones, Bioorg. Med. Chem. Lett. 2005,
15, 4806–4808.
[2] a) H. Skraup, Chem. Ber. 1880, 13, 2086; b) G. Caeiro, P. Magnoux,
J. M. Lopes, F. Lemos, F. Ramoa Ribeiro, J. Mol. Catal. A 2006, 249,
149.
[3] a) M.-E. Theoclitou, L. A. Robinson, Tetrahedron Lett. 2002, 43,
3907; b) M. R. W. Heinrich, W. Steglich, M. G. Banwell, Y. Kash-
man, Tetrahedron 2003, 59, 9239.
[4] a) J. S. Yadav, B. V. S. Reddy, K. Premalatha, M. S. R. Murty, J. Mol.
Catal.
A 2007, 271, 161; b) H. V. Mierde, P. van der Voort, D.
De Vos, F. Verpoort, Eur. J. Org. Chem. 2008, 1625; c) Z. Zhang, J.
Tan, Z. Wang, Org. Lett. 2008, 10, 173.
Scheme 5. Reactions for the mechanism of the silver-catalyzed oxidative
coupling of aniline and ene carbonyl/acetylenic carbonyl.
[5] L. Li, W. D. Jones, J. Am. Chem. Soc. 2007, 129, 10707.
[6] a) B. Gabriele, R. Mancuso, G. Salerno, G. Ruffolo, P. Plastina, J.
Org. Chem. 2007, 72, 6873; b) Y.-L. Zhao, W. Zhang, S. Wang, Q.
Liu, J. Org. Chem. 2007, 72, 4985; c) Q. Zhang, Z. Zhang, Z. H.
Yan, Q. Liu, T. Y. Wang, Org. Lett. 2007, 9, 3651; d) M. J. Sandelier,
P. DeShong, Org. Lett. 2007, 9, 3209.
[7] a) X. Y. Liu, P. Ding, J.-S. Huang, C.-M. Che, Org. Lett. 2007, 9,
2645; b) M. Austin, O. J. Egan, R. Tully, A. C. Pratt, Org. Biomol.
Chem. 2007, 5, 3778; c) S. Atechian, R. Nock, R. D. Norcross, H.
Ratni, A. W. Thomas, J. Verron, R. Masciadri, Tetrahedron 2007, 63,
2811.
Experimental Section
General reaction procedure for the AgOTf-mediated coupling of amines
with ene carbonyl compounds
A round bottomed flask (50 mL) was charged with amine (1.1 mmol,
1.1 equiv), ene carbonyl compound (1 mmol, 1 equiv), AgOTf
(5 mmol%), HOTf (5 mmol%) in toluene (5 mL) under atmospheric
conditions. The mixture was stirred at 1108C for 4 h, the reaction was
cooled down to room temperature, diluted with dichloromethane
(10 mL), and washed with H2O (10 mL). The aqueous layer was extracted
twice with dichloromethane (10 mL) and the combined organic phases
were dried over Na2SO4. After evaporation of the solvents, the residue
was purified by silica-gel chromatography (dichloromethane/petroleum
ether=4:1, v/v).
[8] Y.-C. Wu, L. Liu, H.-J. Li, D. Wang, Y.-J. Chen, J. Org. Chem. 2006,
71, 6592.
[9] G. Sivaprasad, R. Rajesh, P. T. Perumal, Tetrahedron Lett. 2006, 47,
1783.
[10] D. S. Bose, R. K. Kumar, Tetrahedron Lett. 2006, 47, 813.
[11] R. P. Korivi, C.-H. Cheng, J. Org. Chem. 2006, 71, 7079.
[12] C. K. Cho, J. K. Kim, Tetrahedron Lett. 2007, 48, 3775.
[13] X. Zhang, B. Liu, X. Shu, Y. Gao, H. Lv, J. Zhu, J. Org. Chem. 2012,
77, 501.
[14] a) X. L. Li, J. B. Hewgley, C. A. Mulrooney, J. M. Yang, M. C. Ko-
zlowski, J. Org. Chem. 2003, 68, 5500; b) L. Menini, E. V. Gusev-
skaya, Chem. Commun. 2006, 209; c) O. Baslꢂ, C.-J. Li, Green
Chem. 2007, 9, 1047; d) Z. Li, D. S. Bohle, C.-J. Li, Proc. Natl. Acad.
Sci. USA 2006, 103, 8928; e) C.-J. Li, Acc. Chem. Res. 2009, 42, 335;
f) N. Borduas, D. A. Powell, J. Org. Chem. 2008, 73, 7822; g) M. P.
DeMartino, K. Chen, P. S. Baran, J. Am. Chem. Soc. 2008, 130,
11546; h) J. B. Hewgley, S. S. Stahl, M. C. Kozlowski, J. Am. Chem.
Soc. 2008, 130, 12232; i) L. Yang, Z. Lu, S. S. Stahl, Chem. Commun.
2009, 6460.
[15] a) A. Caballero, E. Despagnet-Ayoub, M. M. Dꢃaz-Requejo, A.
Dꢃaz-Rodrꢃguez, M. E. Gonzꢄlez-NfflÇez, R. Mello, B. K. MuÇoz, W.-
S. Ojo, G. Asensio, M. Etienne, P. J. Pꢂrez, Science 2011, 332, 835;
b) M. Naodovic, H. Yamamoto, Chem. Rev. 2008, 108, 3132; c) M.
lvarez-Corral, M. MuÇoz-Dorado, I. Rodrꢃguez-Garcꢃa, Chem.
Rev. 2008, 108, 3174; d) J.-M. Weibel, A. Blanc, P. Pale, Chem. Rev.
2008, 108, 3149; e) Y. Yamamoto, Chem. Rev. 2008, 108, 3199; f) S.
Yoshida, K. Fukui, S. Kikuchi, T. Yamada, J. Am. Chem. Soc. 2010,
132, 4072; g) C. H. Oh, S. Karmakar, H.-S. Park, Y.-C. Ahn, J. W.
Kim, J. Am. Chem. Soc. 2010, 132, 1792; h) P. Tang, T. Furuya, T.
Ritter, J. Am. Chem. Soc. 2010, 132, 12150; i) S. Su, J. A. Porco, Jr.,
J. Am. Chem. Soc. 2007, 129, 7744; j) J. Llaveria, A. Beltrꢄn, M. M.
Dꢃaz-Requejo, M. I. Matheu, S. Castillón, P. J. Pꢂrez, Angew. Chem.
General reaction procedure for the AgOTf-mediated coupling of amines
with acetylenic carbonyl compounds
A round bottomed flask (50 mL) was charged with amine (1.1 mmol,
1.1 equiv), acetylenic carbonyl compounds (1 mmol, 1 equiv), AgOTf
(5 mmol%), HOTf (5 mmol%) in toluene (5 mL) under atmospheric
conditions. The mixture was stirred at 808C for 4 h, the reaction was
cooled down to room temperature, diluted with dichloromethane
(10 mL) and washed with H2O (10 mL). The aqueous layer was extracted
twice with dichloromethane (10 mL) and the combined organic phases
were dried over Na2SO4. After evaporation of the solvents, the residue
was purified by silica-gel chromatography (dichloromethane/petroleum
ether=4:1, v/v).
Acknowledgements
This paper is supported by the Science Foundation of Nanyang Normal
University (ZX2013030).
Keywords: acetylenic carbonyl compounds
heterocycles · silver · synthetic methods
· amines ·
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Xu Zhang and Xuefeng Xu
Int. Ed. 2010, 49, 7092; Angew. Chem. 2010, 122, 7246; k) J. Sun,
S. A. Kozmin, Angew. Chem. Int. Ed. 2006, 45, 4991; Angew. Chem.
2006, 118, 5113.
e) M. Suginome, T. Fukuda, Y. Ito, Org. Lett. 1999, 1, 1977; f) G.
Abbiati, E. M. Beccalli, G. Broggini, C. Zoni, Tetrahedron 2003, 59,
9887; g) K. Kobayashi, K. Yoneda, K. Miyamoto, O. Morikawa, K.
Hisatoshi, Tetrahedron 2004, 60, 11639; h) F. Zhao, X. yang, J. Liu,
Tetrahedron 2004, 60, 9945; i) B. Jiang, Y.-G. Si, J. Org. Chem. 2002,
67, 9449; j) B. R. McNaughton, B. L. Miller, Org. Lett. 2003, 5, 4257;
k) W. Du, D. P. Curran, Org. Lett. 2003, 5, 1765; l) K. Sangu, K. Fu-
chibe, T. Akiyama, Org. Lett. 2004, 6, 353.
[16] a) T. W. Lyons, M. S. Sanford, Chem. Rev. 2010, 110, 1147; b) L. Ac-
kermann, Chem. Rev. 2011, 111, 1315; c) J. Le Bras, J. Muzart,
Chem. Rev. 2011, 111, 1170; d) N. Kuhl, M. N. Hopkinson, J.
Wencel-Delord, F. Glorius, Angew. Chem. Int. Ed. 2012, 51, 10236;
Angew. Chem. 2012, 124, 10382; e) J. J. Mousseau, A. B. Charette,
Acc. Chem. Res. 2013, 46, 412.
[17] a) K. Panda, I. Siddiqui, P. K. Mahata, H. Ila, H. Junjappa, Synlett
2004, 449; b) T. Ishikawa, S. Manabe, T. Aikawa, T. Kudo, S. Saito,
Org. Lett. 2004, 6, 2361; c) C. Theeraladanon, M. Arisawa, A. Nishi-
da, M. Nakagawa, Tetrahedron 2004, 60, 3017; d) J. Ichikawa, Y.
Wada, H. Miyazaki, T. Mori, H. Kuroki, Org. Lett. 2003, 5, 1455;
[18] a) F. Xiao, Y. Chen, Y. Liu, J. Wang, Tetrahedron 2008, 64, 2755;
b) J. S. Damavandi, M. A. Zolfigol, B. Karami, Synth. Commun.
2001, 31, 3183.
Received: June 28, 2014
Revised: July 29, 2014
Published online: September 5, 2014
Chem. Asian J. 2014, 9, 3089 – 3093
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