A sustainable synthesis of 2-benzoxazyl and 2-benzothiazyl ketones from alkynyl bromides and 2-amino(thio)phenols promoted by a recyclable catalytic system

Article abstract of DOI:10.1002/cjoc.201100472

An environmentally and economically sustainable synthesis of 2-benzoxazyl ketones and 2-benzothiazyl ketones through FeCl₃·6H ₂O catalyzed tandem reactions of alkynyl bromides with 2-amino(thio)phenols in [bmim]BF₄ has been developed. Remarkable advantages of this new synthetic strategy include high efficiency, readily available starting materials, and recyclable catalyst and reaction medium. An environmentally and economically sustainable synthesis of 2-benzoxazyl ketones and 2-benzothiazyl ketones through FeCl₃·6H₂O catalyzed tandem reactions of alkynyl bromides with 2-amino(thio)phenols in [bmim]BF₄ has been developed. Remarkable advantages of this new synthetic strategy include high efficiency, readily available starting materials, and recyclable catalyst and reaction medium. Copyright

Full text of DOI:10.1002/cjoc.201100472

NOTE
DOI: 10.1002/cjoc.201100472
A Sustainable Synthesis of 2-Benzoxazyl and 2-Benzothiazyl
Ketones from Alkynyl Bromides and 2-Amino(thio)phenols
Promoted by a Recyclable Catalytic System
Cui, Liangyan(崔良艳)
He, Yan(何艳)
Fan, Xuesen*(范学森)
School of Chemistry and Environmental Science, Key Laboratory for Yellow River and Huai River Water
Environment and Pollution Control, Ministry of Education, Henan Key Laboratory of Environmental
Pollution Control, Henan Normal University, Xinxiang, Henan 453007, China
An environmentally and economically sustainable synthesis of 2-benzoxazyl ketones and 2-benzothiazyl ke-
tones through FeCl3•6H2O catalyzed tandem reactions of alkynyl bromides with 2-amino(thio)phenols in
[bmim]BF4 has been developed. Remarkable advantages of this new synthetic strategy include high efficiency,
readily available starting materials, and recyclable catalyst and reaction medium.
Keywords 2-benzoxazyl ketone, 2-benzothiazyl ketone, alkynyl bromide, FeCl3•6H2O, ionic liquid
Introduction
high solubility for many organic molecules as well as
metal catalysts, and the product can be separated easily
by extraction with non-polar organic solvents. Repeated
use of the metal catalyst solution and negligible metal
contamination of the product are advantages of the
method.
As a continuation of our research in utilizing FeCl3•
6H2O as an economical yet efficient oxidant and ionic
liquids as sustainable reaction media,[25] we envisioned
a new approach toward 2-benzoxazyl and 2-benzo-
thiazyl ketones through tandem reactions of alkynyl
bromides with 2-amino(thio)phenols under the promo-
tion of FeCl3•6H2O by using [bmim]BF4 as a recyclable
reaction medium. Herein, we report our preliminary
results in this regard.
To date, much attention has been paid toward the
synthesis of 2-benzoxazyl ketones and 2-benzothiazyl
ketones since they are not only ubiquitous structural
units in a wide variety of naturally occurring com-
pounds, but also versatile synthetic synthons toward
other biologically and synthetically interesting com-
pounds.[1-5] As a result, various synthetic methods to-
ward 2-benzoxazyl ketones and 2-benzothiazyl ketones
have been developed.[6-12] While literature methods are
generally efficient and reliable, they usually suffer from
expensive catalysts, specially made starting materials or
highly reactive organometallic precursors, which not
only preclude the presence of labile functional groups
on the substrates, but also entail delicate reaction condi-
tions.
Alkynyl bromides are among the most versatile syn-
thetic building blocks. This has been best demonstrated
by their applications in the synthesis of a plethora of
biologically and synthetically interesting com-
pounds.[13-18] On the other hand, iron as an abundant,
economical and environmentally friendly metal has
shown increasing promise as catalyst in many organic
syntheses.[19] Among various iron compounds, FeCl3•
6H2O is extremely cheap and environmentally benign. It
has shown versatile reactivity and has been used as ei-
ther oxidant or Lewis acid in a wide variety of organic
reactions.[20] Meanwhile, room temperature ionic liquids
have gained increasing importance as environmentally
benign and recyclable reaction media.[21-24] They offer a
Experimental
General
Analytical thin layer chromatography (TLC) was
carried out by using silica gel 60 F254 pre-coated plates.
Visualization was accomplished with UV lamp. NMR
spectra were recorded by using TMS as internal stan-
dard and peak multiplicities are designed as follows: s
(singlet); d (doublet); t (triplet); m (multiplet); dd (dou-
blet of doublets); td (triplet of doublets); br s (broad
singlet), etc. and coupling constants were given in Hz.
Chemical shifts (δ) were expressed downfield from the
internal standard tetramethylsilane.
*
E-mail: xuesen.fan@htu.cn; Tel.: ＋86-373-3329261; Fax: ＋86-373-3326336
Received October 8, 2011; accepted December 1, 2011.
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cjoc.201100472 or from the author.
992
© 2012 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2012, 30, 992—996

A Sustainable Synthesis of 2-Benzoxazyl and 2-Benzothiazyl Ketones
Typical procedure for the preparation of 3a
Scheme 1
A mixture of 1-(2-bromoethynyl)benzene (1a, 1
mmol), 2-aminophenol (2a, 1 mmol) and FeCl3•6H2O
(0.1 mmol) in [bmim]BF4 (1 mL) was stirred at 80 ℃.
Upon completion as monitored by TLC, the mixture
was extracted with diethyl ether (10 mL×3). The resi-
due was concentrated and dried under reduced pressure
at 90 ℃ overnight to recover the catalytic system con-
taining Fe(III) and ionic liquid for reuse. The combined
organic phases were concentrated under vacuum. The
crude product was purified by column chromatography
eluting with ethyl acetate/hexane (3%—5%) to give
2-benzoxazyl phenyl ketone (3a). 3b—3m and 5a—5n
were obtained in a similar manner.
NH2
OH
Various conditions
Br
+
1a
2a
O
N
O
3a
Table 1 Optimization study for the synthesis of 3aa
Entry Ferric salts (equiv.)
Solvent Temp./℃ t/h Yieldb/%
1
2
3
4
5
6
7
8
9
FeCl3•6H2O (1)
[bmim]BF4
[bmim]BF4
60
60
60
60
60
60
60
60
60
60
80
100
80
6
6
56
56
51
46
57
51
52
51
—
Results and Discussion
FeCl3 (1)
Initially, 1-(2-bromoethynyl)benzene (1a) and
2-aminophenol (2a) were chosen as model substrates to
study the feasibility of our envisioned route. Firstly, the
mixture of 1a and 2a in [bmim]BF4 was stirred at 60 ℃
for 6 h in the presence of 1 equiv. of FeCl3•6H2O. To
our delight, the reaction proceeded smoothly to give
2-benzoxazyl phenyl ketone (3a) in 56% yield. To op-
timize the reaction, different ferric salts, solvents and
reaction temperatures were screened (Scheme 1, Table
1). In one set of the reactions, various Fe(III) salts were
tested and FeCl3•6H2O provided the maximum yield of
3a (Entries 1—4). The loadings of FeCl3•6H2O were
also analyzed. It turned out that increasing the amount
of FeCl3•6H2O from 1 equiv. to 2 equiv. did not im-
prove the reaction obviously (Entry 5). On the other
hand, FeCl3•6H2O in less than 1 equiv. resulted in mod-
erate yields of 3a (Entries 6—8). It was noticed that 3a
was obtained in 51% yield when only 0.1 equiv. of
FeCl3•6H2O were used (Table 1, Entry 8). In the ab-
sence of FeCl3•6H2O, however, no 3a was formed as
indicated by TLC analysis (Entry 9). On the other hand,
when the reaction was run under a nitrogen atmosphere
with 0.1 equiv. of FeCl3•6H2O, only trace amount of 3a
was observed (Entry 10). These results indicated that
the combination of catalytic amount of FeCl3•6H2O
with air serves as efficient oxidant for the formation of
3a. With FeCl3•6H2O as catalyst and air as stoichiomet-
ric oxidant, the present procedure represents a highly
economical and practical method for the preparation of
2-benzoxazyl ketones.
Fe(NO2)3•9H2O (1) [bmim]BF4
Fe2(SO4)3•xH2O (1) [bmim]BF4
6
6
FeCl3•6H2O (2)
FeCl3•6H2O (0.5)
FeCl3•6H2O (0.2)
FeCl3•6H2O (0.1)
—
[bmim]BF4
[bmim]BF4
[bmim]BF4
[bmim]BF4
[bmim]BF4
[bmim]BF4
[bmim]BF4
[bmim]BF4
[bmim]PF6
6
6
10
10
10
10 FeCl3•6H2O (0.1)
11 FeCl3•6H2O (0.1)
12 FeCl3•6H2O (0.1)
13 FeCl3•6H2O (0.1)
a 1a and 2a (1 mmol), [bmim]BF4 (1 mL). b Isolated yields. c Un-
der nitrogen atmosphere.
10 Tracec
10
10
10
62
60
57
this reaction was explored (Table 2). It shows that all
the substrates studied undergo this reaction smoothly. In
comparison, substrates with electron-withdrawing
groups usually give the corresponding products in
higher yields than substrates with electron-donating
groups (Entries 5—7, 9—10). It is also demonstrated
that various functional groups, such as methyl, nitro,
cyano and halides, are well tolerated under the condi-
tions.
Encouraged by the above results, we then checked
the possibility of extending this method to the synthesis
of 2-benzothiazyl ketones (5) by using 2-aminothio-
phenols (4) as the substrates. Our following studies re-
vealed that 2-aminothiophenols are good substrates for
the tandem process. They reacted with various alkynyl
bromides smoothly and efficiently to give 2-benzo-
thiazyl ketones in high yields (Table 3). For alkynyl
bromides with either electron-poor or electron-rich
groups on the aromatic rings, the reactions proceeded
with almost equal efficiency (Entries 1—8). However,
the reactions were slowed down with 2-amino-3-chloro-
benzenethiol as the substrate (Entries 9—11). These
results indicated that electronic effect on the aryl rings
did not play a significant role in affecting the reaction,
probably due to the high reactivity of these substrates.
In further screening, we found that raising the tem-
perature from 60 to 80 ℃ increased the yield of 3a
from 51% to 62% (Entry 11). However, higher tem-
perature did not enhance the yield (Entry 12). Finally,
[bmim]PF6 was also tried as the medium for this reac-
tion. It showed similar efficiency as that of [bmim][BF4]
(Entry 13). In summary of the optimization, the reaction
of 1a and 2a in [bmim]BF4 in the presence of 0.1 equiv.
of FeCl3•6H2O at 80 ℃ afforded 3a in a yield of 62%
(Entry 11).
With the optimized reaction conditions, the scope of
Chin. J. Chem. 2012, 30, 992—996
© 2012 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
993

Cui, He & Fan
NOTE
Table 2 Preparation of various benzoxazyl ketones (3)a
Continued
Yieldb/%
Entry R1 in 1 R2 in 2
Product
Br
NH2
OH
FeCl3 6H2O (10%)
[bmim]BF4, 80 oC
+
R2
O
R1
O2N
N
1
2
10 3-NO2 4-CH3
73
O
CH3
O
3j
N
R1
O
O
N
R2
3
11
H
4-Cl
66
O
Cl
Entry R1 in 1 R2 in 2
Product
Yieldb/%
3k
O
O
N
N
N
1
2
3
4
5
6
7
8
H
H
H
H
H
H
H
H
62
67
66
70
75
76
74
65
76
O
12 4-Br 4-Cl
68
O
Cl
Br
Br
3a
3l
O
N
N
O
4-Br
O
O
Br
Br
13 3-Br 4-Cl
65
O
Cl
3b
3m
O
a 1 and 2 (1 mmol), FeCl3•6H2O (0.1 mmol), [bmim]BF4 (1 mL),
80 ℃, 10 h. b Isolated yields.
3-Br
Table 3 Preparation of various benzothiazyl ketones (5)a
3c
Br
O
NH2
R3
N
FeCl3 6H2O (10%)
[bmim]BF4, 80 oC
R1
+
4-Cl
SH
O
Cl
1
4
3d
O
N
O
R1
N
S
4-CN
4-NO2
3-NO2
R3
5
O
NC
Entry R1 in 1 R3 in 4
Product
Yieldb/%
3e
O
O
N
N
1
2
3
4
H
H
H
H
H
81
85
84
80
S
O
O2N
O2N
5a
3f
O
O
N
N
4-Br
S
O
Br
3g
5b
O
O
N
N
4-CH3
4-OCH3
4-Br 4-CH3
4-NO2 4-CH3
S
O
CH3
H3C
Br
5c
3h
O
O
N
N
9
S
O
CH
H3CO
3
O2N
5d
3i
994
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© 2012 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2012, 30, 992—996

A Sustainable Synthesis of 2-Benzoxazyl and 2-Benzothiazyl Ketones
Continued
Continued
Yieldb/%
Entry R1 in 1 R3 in 4
Product
Yieldb/%
Entry R1 in 1 R3 in 4
Product
O
O
N
N
14 4-OCH3 5-CH3
76
S
4
5
6
7
8
9
4-OCH3
4-NO2
H
H
80
H3CO
S
H3CO
5n
5d
CH3
a 1 and 4 (1 mmol), FeCl3•6H2O (0.1 mmol), [bmim]BF4 (1 mL),
80 ℃, 6 h. b Isolated yields.
O
N
H
87
80
85
81
67
68
62
79
78
S
In contrast, steric hindrance seemed to be a key factor in
affecting the tandem process. As a further aspect, it is
noted that functional groups such as methyl, methoxy,
nitro and halides, were well compatible with the opti-
mized conditions.
O2N
5e
O
N
In addition to being broadly utilized as alternative
reaction media for sustainable chemistry, ionic liquids
are also known as efficient immobilizing agents to fa-
cilitate catalyst recycling. In this regard, we studied the
recyclability of Fe(III) together with [bmim]BF4 by us-
ing 1-(2-bromoethynyl)benzene (1a) and 2-amino thio-
phenol (4a) as model substrates. It turned out that
Fe(III)/[bmim]BF4 could be reused directly for a new
cycle after the ionic liquid phase was extracted with
diethyl ether (10 mL×3) and dried under vacuum at 90
℃ overnight. The recovered Fe(III)/[bmim]BF4 was
reused for 5 times and the corresponding reactions af-
forded 5a in yields of 80%, 76%, 75%, 70% and 55%
respectively. In these reactions, [bmim]BF4 not only
acted as the reaction medium, but also as an immobiliz-
ing agent for facilitating the catalyst recycling.
We have recently reported that 2-benzothiazyl ke-
tones (5) could be obtained from the condensation of
o-aminothiophenol and phenyl acetaldehyde under the
promotion of FeCl3•6H2O.[25d] To our knowledge,
phenyl acetaldehyde derivatives are scarcely commer-
cially available and are usually obtained through the
Darzens condensation and subsequent saponification of
α,β-epoxy ester followed by decarboxylation. This se-
quence of reactions is hard to deal with and the yields of
phenyl acetaldehydes are low. On the other hand, al-
kynyl bromides used herein can be easily prepared with
high yields from the condensation of aldehydes with
tetrabromomethane followed by base promoted dehy-
drobromination.[26] We have also reported that
2-benzoxazyl ketones and 2-benzothiazyl ketones could
be obtained from the reaction of 1,1-dibromoethenes
with 2-amino(thio)phenols promoted by TBAF•3H2O
and RuCl3 by using DMF as the reaction medium.[27] As
a polar aprotic organic solvent with high boiling point,
DMF is relatively toxic and difficult to be recovered.[28]
In addition, RuCl3 is much more expensive than FeCl3•
6H2O. Therefore, the utility and applicability of that
procedure is unfortunately compromised by loss of
Ru(III) catalyst and DMF. Compared with the above
mentioned protocols, procedure presented in this paper
not only has the advantage of starting from readily
available substrates and employing the much cheaper
4-Cl
4-Cl
S
Cl
5f
O
N
4-F
S
Cl
F
5g
O
N
4-CH3 4-Cl
S
Cl
H3C
5h
O
N
Cl
H
3-Cl
S
5i
O
Cl
N
10 4-CH3 3-Cl
S
H3C
H3C
5j
O
N
Cl
11 3-CH3 3-Cl
S
5k
O
N
12
4-F 5-CH3
S
F
CH3
5l
O
N
13 4-CH3 5-CH3
S
H3C
CH3
5m
Chin. J. Chem. 2012, 30, 992—996
© 2012 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
995

Cui, He & Fan
NOTE
[13] (a) Sharma, A.; Schwab, R. S.; Braga, A. L.; Barcellos, T.; Paixão,
M. W. Tetrahedron Lett. 2008, 49, 5172; (b) Braga, A. L.;
Reckziegel, A.; Menezes, P. H.; Stefani, H. A. Tetrahedron Lett.
1993, 34, 393.
[14] Hirano, S.; Fukudome, Y.; Tanaka, R.; Sato, F.; Urabe, H.
Tetrahedron 2006, 62, 3896.
FeCl3•6H2O as a catalyst, but also features other advan-
tages in that [bmim]BF4 is used as a sustainable and
recyclable reaction medium, and as an efficient immo-
bilizing agent for facilitating the catalyst recycling.
Conclusions
[15] Kuijpers, B. H. M.; Dijkmans, G. C. T.; Groothuys, S.; Quaedflieg,
P. J.; Blaauw, L. M.; Floris, R. H.; Delft, L.; Rutjes, F. P. J. T.
Synlett 2005, 3059.
[16] (a) Matsuyama, N.; Hirano, K.; Satoh, T.; Miura, M. Org. Lett. 2009,
11, 18; (b) Kawano, T.; Matsuyama, N.; Hirano, K.; Satoh, T.;
Miura, M. J. Org. Chem. 2010, 75, 1764.
[17] Yao, B.; Liang, Z.; Niu, T.; Zhang, Y. J. Org. Chem. 2009, 74, 4630.
[18] Hara, R.; Liu, Y.; Sun, W.; Takahashi, T. Tetrahedron Lett. 1997, 38,
4103.
In summary, an environmentally and economically
sustainable synthesis of 2-benzoxazyl ketones and
2-benzothiazyl ketones has been developed in this paper.
The synthetic procedure itself has such advantages as
high efficiency, mild reaction conditions and recyclable
catalyst and solvent. Current studies are in progress to
extend the synthetic potential of this novel procedure.
[19] (a) Shi, F.; Tse, M. K.; Li, Z. P.; Beller, M. Chem. Eur. J. 2008, 14,
8793; (b) Nakanishi, M.; Bolm, C. Adv. Synth. Catal. 2007, 349, 861;
(c) Oldenburg, P. D.; Shteinman, A. A.; Que, J. L. J. Am. Chem. Soc.
2005, 127, 15672; (d) Xu, X. B.; Liu, J.; Liang, L. F.; Li, H. F.; Li,
Y. Z. Adv. Synth. Catal. 2009, 351, 2599; (e) Mao, J. C.; Xie, G. L.;
Zhan, J. M.; Hua, Q. Q.; Shi, D. Q. Adv. Synth. Catal. 2009, 351,
1268; (f) Bolm, C.; Legros, J.; Le Paih, J.; Zani, L. Chem. Rev. 2004,
104, 6217; (g) Enthaler, S.; Junge, K.; Beller, M. Angew. Chem., Int.
Ed. 2008, 47, 3317; (h) Correa, A.; Mancheno, O. G.; Bolm, C.
Chem. Soc. Rev. 2008, 37, 1108; (i) Sherry, B. D.; Fürstner, A. Acc.
Chem. Res. 2008, 41, 1500; (j) Chen, M. S.; White, M. C. Science
2010, 327, 566; (k) Zhu, S. F.; Cai, Y.; Mao, H. X.; Xie, J. H.; Zhou,
Q. L. Nature Chem. 2010, 2, 546.
[20] (a) Chai, G. B.; Lu, Z.; Fu, C. L.; Ma, S. M. Adv. Synth. Catal. 2009,
351, 1946; (b) Wu, W. Y.; Wang, J. C.; Tsai, F. Y. Green Chem.
2009, 11, 326; (c) Liu, Z. Q.; Wang, J. G.; Zhao, Y. K.; Zhou, B.
Adv. Synth. Catal. 2009, 351, 371; (d) Fan, J. M.; Gao, L. F.; Wang,
Z. Y. Chem. Commun. 2009, 5021; (e) Huang, W.; Zheng, P. Z.;
Zhang, Z. X.; Liu, R. T.; Chen, Z. X.; Zhou, X. G. J. Org. Chem.
2008, 73, 6845; (f) Huang, W.; Shen, Q. S.; Wang, J. L.; Zhou, X. G.
J. Org. Chem. 2008, 73, 1586; (g) Kischel, J.; Mertins, K.; Michalik,
D.; Zapf, A.; Beller, M. Adv. Synth. Catal. 2007, 349, 865.
[21] (a) Ranke, J.; Stolte, S.; Strörmann, R.; Arning, J.; Jastorff, B. Chem.
Rev. 2007, 107, 2183; (b) Zhong, T.; Le, Z. G.; Xie, Z. B.; Cao, X.;
Lü, X. X. Chin. J. Org. Chem. 2010, 30, 981.
Acknowledgement
This work was supported by the National Natural
Science Foundation of China (Nos. 20972042,
20911140238), Innovation Scientist and Technician
Troop Construction Projects of Henan Province (No.
104100510019) and PCSIRT (No. IRT1061).
References
[1] Chekler, E. L. P.; Katoch-Rouse, R.; Kiselyov, A. S.; Sherman, D.;
Ouyang, X. H.; Kim, K.; Wang, Y.; Hadari, Y. R.; Doody, J. F.
Bioorg. Med. Chem. Lett. 2008, 18, 4344.
[2] Gillis, J. C.; Brogden, R. N. Drugs 1997, 53, 139.
[3] Kellen, J. A. Curr. Drug Targets 2001, 2, 423.
[4] Tomaselli, G. Heart Drug 2001, 1, 183.
[5] Boger, D. L.; Miyauchi, H.; Hedrick, M. P. Bioorg. Med. Chem. Lett.
2001, 11, 1517.
[6] (a) Viaud, M. C.; Jamoneau, P.; Baudin, M.-L.; Savelon, L.;
Guillaumet, G. Tetrahedron 1997, 53, 5159; (b) Katritzky, A. R.;
Suzuki, K.; Singh, S. K.; He, H. Y. J. Org. Chem. 2003, 68, 5720; (c)
Chatani, N.; Fukuyama, T.; Tatamidani, H.; Kakiuchi, F.; Murai, S.
J. Org. Chem. 2000, 65, 4039; (d) Yang, X. L.; Xu, C. M.; Lin, S.
M.; Chen, J. X.; Ding, J. C.; Wu, H. X.; Su, W. K. J. Braz. Chem.
Soc. 2009, 21, 37; (e) Boga, C.; Stengel, R.; Abdayem, R.; Vecchio,
E. D.; Forlani, L.; Todesco, P. E. J. Org. Chem. 2004, 69, 8903.
[7] (a) Chinchilla, R.; Najera, C.; Yus, M. Chem. Rev. 2004, 104, 2667;
(b) Marcantonio, K. M.; Frey, L. F.; Murry, J. A.; Chen, C. Y.
Tetrahedron Lett. 2002, 43, 8845; (c) Frey, L. F.; Marcantonio, K.
M.; Chen, C. Y.; Wallace, D. J.; Murry, J. A.; Tan, L.; Chen, W.;
Dolling, U. H.; Grabowski, E. J. J. Tetrahedron 2003, 59, 6363.
[8] Kernag, C. A.; Bobbitt, J. M.; McGrath, D. V. Tetrahedron Lett.
1999, 40, 1635.
[22] (a) Stolte, S.; Matzke, M.; Arning, J.; Böschen, A.; Pitner, W. R.;
Welz-Biermann, U.; Jastorff, B.; Ranke, R. Green Chem. 2007, 9,
1170; (b) Zhang, Y.; Jin, H.; You, X. W.; Shang, Z. C. Chin. J. Org.
Chem. 2011, 31, 387.
[23] (a) Afonso, C. A. M.; Branco, L. C.; Candeias, N. R.; Gois, P. M.
P.; Lourenco, N. M. T.; Mateus, N. M. M.; Rosa, J. N. Chem.
Commun. 2007, 2669; (b) Qin, J.; Zhang, J.; Wu, B.; Zheng, Z. G.;
Yang, M.; Yu, X. Q. Chin. J. Chem. 2009, 27, 1782; (c) Fan, X. S.;
He, Y.; Wang, Y. Y.; Zhang, X. Y.; Wang, J. J. Chin. J. Chem. 2011,
29, 773.
[24] Pârvulescu, V. I.; Hardacre, C. Chem. Rev. 2007, 107, 2615.
[25] (a) Fan, X. S.; Wang, Y. Y.; He, Y.; Zhang, X. Y.; Wang, J. J.
Tetrahedron Lett. 2010, 51, 3493; (b) Zhang, X. Y.; Li, X. Y. ; Li, D.
F.; Qu, Q. R.; Wang, J. J.; Loiseau, P. M.; Fan, X. S. Bioorg. Med.
Chem. Lett. 2009, 19, 6280; (c) Fan, X. S.; Feng, D.; Qu, Y. Y.;
Zhang, X. Y.; Wang, J. J.; Loiseau, P. M.; Andrei, G.; Snoeck, R.;
De Clercq, E. Bioorg. Med. Chem. Lett. 2010, 20, 809; (d) Fan, X. S.;
He, Y.; Wang, Y. Y.; Zhang, X. Y.; Wang, J. J. Tetrahedron Lett.
2011, 52, 899.
[9] Boudreau, J.; Doucette, M.; Ajjou, A. N. Tetrahedron Lett. 2006, 47,
1695.
[10] Dieter, R. K. Tetrahedron 1999, 55, 4177.
[11] (a) Schoenberg, A.; Heck, R. F. J. Am. Chem. Soc. 1974, 96, 7761;
(b) Sergeev, A.; Spannenber, G. A.; Beller, M. J. Am. Chem. Soc.
2008, 130, 15549; (c) Liu, J.; Peng, X.; Sun, W.; Zhao, Y.; Xia, C.
Org. Lett. 2008, 10, 3933; (d) Liu, Q.; Li, G.; He, J.; Liu, J.; Li, P.;
Lei, A. Angew. Chem. 2010, 122, 3443; (e) Zhang, Z.; Liu, Y.; Gong,
M.; Zhao, X.; Zhang, Y.; Wang, J. Angew. Chem. 2010, 122, 1157;
(f) Ambrosini, L. M.; Cernak, T. A.; Lambert, T. H. Synthesis 2010,
870.
[26] Okutani, M.; Mori, Y. J. Org. Chem. 2009, 74, 442.
[27] Fan, X. S.; He, Y.; Zhang, X. Y.; Guo, S. H.; Wang, Y. Y. Tetrahe-
dron 2011, 67, 6369.
[12] Wu, X. F.; Anbarasan, P.; Neumann, H.; Beller, M. Angew. Chem.,
Int. Ed. 2010, 49, 7316.
[28] Fischmeister, C.; Doucet, H. Green Chem. 2011, 13, 741.
(Lu, Y.)
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