Direct Three-Component Synthesis of α-Cyano Acrylates Involving Cascade Knoevenagel Reaction and Esterification

Article abstract of DOI:10.1002/cjoc.201500420

A direct three-component approach has been developed for the synthesis of α-cyano acrylates starting from aldehydes, alcohols and α-cyano acetamide by employing cyanuric chloride as an organocatalyst. A class of structurally diverse α-cyano acrylates have been provided with good to excellent yields via the cascade transformation of Knoevenagel condensation and amide esterification.

Full text of DOI:10.1002/cjoc.201500420

FULL PAPER
DOI: 10.1002/cjoc.201500420
Direct Three-Component Synthesis of α-Cyano Acrylates
Involving Cascade Knoevenagel Reaction and
Esterification
Yanfeng Jing, Jiaojiao Meng, Yunyun Liu,* and Jie-Ping Wan*
Key Laboratory of Functional Small Organic Molecules, Ministry of Education, and College of Chemistry and
Chemical Engineering, Jiangxi Normal University, Nanchang, Jiangxi 330022, China
A direct three-component approach has been developed for the synthesis of α-cyano acrylates starting from al-
dehydes, alcohols and α-cyano acetamide by employing cyanuric chloride as an organocatalyst. A class of structur-
ally diverse α-cyano acrylates have been provided with good to excellent yields via the cascade transformation of
Knoevenagel condensation and amide esterification.
Keywords three-component reaction, acrylates, organocatalysis, Knoevenagel reaction, amide esterification
Introduction
ric chloride (2,4,6-trichloro-1,3,5-triazine, TCT)[10] as
an organocatalyst without using any additional organic
solvent (Eq. 2, Scheme 1). The most noteworthy advan-
tage of this method lies in its expanded ability of gener-
ating the ester diversity by simply varying the alcohol
component.
Acrylates are a class of fundamental organic mole-
cules which display invaluable merits as main building
blocks in organic synthesis. Owing to their intrinsically
versatile reactivity, acrylates have been frequently em-
ployed in Michael addition,[1] olefin hydrogenation,[2]
C－H bond activation-based cross-coupling,[3] various
cycloaddtion reactions[4] as well as Baylis-Hillman re-
action.[5] More over, acrylates have been known as a
main fragment in many molecules possessing enriched
biological activity.[6] As a kind of particularly useful
acrylates, the α-cyano acrylates have been reported to
possess distinct synthetic application owing to the pres-
ence of cyano group.[7]
Scheme 1 Different routes to α-cyano acrylates
Previous: conventional Knoevenagel reaction
CO2R2
catalyst
R1
R2O2C
CN
(1)
CHO
R1
CN
solvent
limited availability to generate
product diversity
Present: multicomponent cascade Knoevenagel reaction
and amide esterification
As a classical approach, the Knoevenagel condensa-
tion of cyano methylene substrates with aldehydes has
been the dominant option in the preparation of α-cyano
acrylates (Eq. 1, Scheme 1).[8] In this method, the syn-
thesis of products containing different ester fragments
relies on the employment of different cyano acetates,
and the lack of diversity of commercially available re-
agents is therefore a serious restriction for generating
the ester-based product library. Therefore, devising al-
ternative synthetic approach allowing much easier ac-
cess to acrylates bearing diverse ester substructure is
presently an urgent issue. Base on our ongoing efforts in
developing diversity-oriented synthetic methods in the
form of multicomponent reactions,[9] we report herein
the first example on the synthesis of different alkyl
acrylates through the three-component reactions of al-
dehydes, alcohols and cyano acetamide by using cyanu-
CO2R2
R1 CHO
TCT
neat
R2OH
NC
CONH2
(2)
R1
CN
broadly available component and easy
generation of hight product diverstiy
Experimental
A 25 mL round bottom flask was charged with aryl
aldehyde 1 (1 mmol), cynano acetamide 2a (1 mmol),
TCT (0.5 mmol) and alcohol 3 (2 mL). The resulting
mixture was then heated at 80 ℃ (reflux for low b.p.
alcohol) for 12 h at open air atmosphere. After cooling
down to room temperature, 5 mL water was added and
the suspension was extracted with ethyl acetate (10 mL
×3). The combined organic layer was dried over anhy-
*
E-mail: chemliuyunyun@jxnu.edu.cn; wanjieping@jxnu.edu.cn
Received June 3, 2015; accepted July 1, 2015; published online August 12, 2015.
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cjoc.201500420 or from the author.
1194
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Chin. J. Chem. 2015, 33, 1194—1198

Direct Three-Component Synthesis of α-Cyano Acrylates
drous Na2SO4 and filtered. The acquired solution was
then subjected to reduced pressure to remove the solvent.
Purification of the residue with silica gel column chro-
matography provided pure products with the elution of
mixed petroleum ether and ethyl acetate (V(PET)/V(EA)
＝80∶1).
NMR (400 MHz, CDCl3) δ: 8.06 (s, 1H), 7.93 (d, J＝
9.2 Hz, 2H), 6.68 (t, J＝9.2 Hz, 2H), 4.33 (q, J＝7.2 Hz,
2H), 3.10 (s, 6H), 1.37 (t, J＝7.6 Hz, 3H).
Ethyl
3-(2-chloropyridin-3-yl)-2-cyanoacrylate
1
(4l)[9e] White solid. m.p. 68－69 ℃; H NMR (400
MHz, CDCl3) δ: 8.60 (s, 1H), 8.54 (d, J＝6.4 Hz, 2H),
7.42－7.46 (m, 1H), 4.43 (q, J＝7.2 Hz, 2H), 1.42 (t,
J＝7.2 Hz, 3H).
Ethyl 2-cyano-3-phenylacrylate (4a)[9e] White
1
solid. m.p. 62－64 ℃; H NMR (400 MHz, CDCl3) δ:
8.26 (s, 1H), 7.99 (d, J＝7.2 Hz, 2H), 7.58－7.51 (m,
3H), 4.39 (q, J＝7.2 Hz, 2H), 1.40 (t, J＝7.2 Hz, 3H).
Ethyl 3-(4-chlorophenyl)-2-cyanoacrylate (4b)[9e]
Methyl 2-cyano-3-phenylacrylate (4m)[8h] White
solid. m.p. 89－90 ℃; H NMR (400 MHz, CDCl3) δ:
1
8.26 (s, 1H), 7.99 (d, J＝7.2 Hz, 2H) 7.55 (d, J＝6.8 Hz,
1H), 7.50 (t, J＝8.0 Hz, 2H), 3.94 (s, 3H).
1
White solid. m.p. 87－88 ℃; H NMR (400 MHz,
CDCl3) δ: 8.20 (s, 1H), 7.94 (d, J＝8.0 Hz, 2H), 7.48 (d,
J＝8.4 Hz, 2H), 4.39 (q, J＝7.2 Hz, 2H), 1.40 (t, J＝7.2
Hz, 3H).
Methyl 3-(4-chlorophenyl)-2-cyanoacrylate (4n)[8h]
1
White solid. m.p. 132－133 ℃; H NMR (400 MHz,
CDCl3) δ: 8.21 (s, 1H), 7.93 (d, J＝8.4 Hz, 2H), 7.48 (d,
J＝8.4 Hz, 2H), 3.94 (s, 3H).
Ethyl 3-(4-bromophenyl)-2-cyanoacrylate (4c)[9e]
1
White solid. m.p. 99－101 ℃; H NMR (400 MHz,
Methyl 2-cyano-3-p-tolylacrylate (4o)[12]
yellow solid. m.p. 112－113 ℃; H NMR (400 MHz,
CDCl3) δ: 8.18 (s, 1H), 7.90 (d, J＝8.0 Hz, 2H), 7.30 (d,
J＝7.8 Hz, 2H), 3.93 (s, 3H), 2.43 (s, 3H).
Pale
1
CDCl3) δ: 8.18 (s, 1H), 7.85 (d, J＝8.4 Hz, 2H), 7.64 (d,
J＝8.8 Hz, 2H), 4.39 (q, J＝6.8 Hz, 2H), 1.40 (t, J＝7.2
Hz, 3H).
Ethyl 2-cyano-3-p-tolylacrylate (4d)[9e]
White
Methyl
2-cyano-3-(4-methoxyphenyl)acrylate
1
1
solid. m.p. 82－83 ℃; H NMR (400 MHz, CDCl3) δ:
8.21 (s, 1H), 7.90 (d, J＝8.4 Hz, 2H), 7.30 (d, J＝8.4
Hz, 2H), 4.37 (q, J＝7.2 Hz, 2H), 2.43 (s, 3H), 1.39 (t,
J＝7.2 Hz, 3H).
(4p)[8h] White solid. m.p. 104－105 ℃; H NMR
(400 MHz, CDCl3) δ: 8.18 (s, 1H), 8.00 (d, J＝8.8 Hz,
2H), 6.99 (d, J＝8.4 Hz, 2H), 3.92 (s, 3H), 3.89 (s, 3H).
Propyl 2-cyano-3-p-tolylacrylate (4q)[9e] Color-
less liquid. 1H NMR (400 MHz, CDCl3) δ: 8.21 (s, 1H),
7.90 (d, J＝8.4 Hz, 2H), 7.30 (d, J＝8.0 Hz, 2H), 4.27 (t,
J＝6.4 Hz, 2H), 2.43 (s, 3H), 1.83－1.74 (m, 2H), 1.02
(t, J＝7.2 Hz, 3H).
Ethyl 2-cyano-3-(4-methoxyphenyl)acrylate (4e)[9e]
1
Yellow solid. m.p. 94－95 ℃; H NMR (400 MHz,
CDCl3) δ: 8.17 (s, 1H), 8.00 (d, J＝8.4 Hz, 2H) 6.99 (d,
J＝8.4 Hz, 2H), 4.36 (q, J＝6.8 Hz, 2H), 3.89 (s, 3H),
1.39 (t, J＝7.2 Hz, 3H).
Isopropyl 2-cyano-3-phenylacrylate (4r)[9e] Yel-
low solid. m.p. 69－70 ℃; 1H NMR (400 MHz, CDCl3)
δ: 8.24 (s, 1H), 7.99 (t, J＝8.4 Hz, 2H), 7.56－7.49 (m,
3H), 5.24－5.18 (m, 1H), 1.38 (d, J＝6.4 Hz, 6H).
Ethyl 2-cyano-3-(3-methoxyphenyl)acrylate (4f)[8a]
1
Yellow liquid. H NMR (400 MHz, CDCl3) δ: 8.21 (s,
1H), 7.59 (s, 1H), 7.51 (d, J＝8.0 Hz, 1H), 7.40 (t, J＝
8.0 Hz, 1H), 7.12－7.09 (m, 1H), 4.38 (q, J＝8.0 Hz,
2H), 1.40 (t, J＝7.2 Hz, 3H).
Butyl 2-cyano-3-phenylacrylate (4s)[9e]
White
1
solid. m.p. 107－109 ℃; H NMR (400 MHz, CDCl3)
δ: 8.25 (s, 1H), 7.99 (d, J＝7.2 Hz, 2H), 7.58－7.49 (m,
3H), 4.33 (t, J＝6.4 Hz, 2H), 1.79－1.72 (m, 2H),
1.52－1.43 (m, 2H), 1.00－0.96 (m, 3H).
Ethyl 3-(2-chlorophenyl)-2-cyanoacrylate (4g)[9e]
1
White solid. m.p. 78－79 ℃; H NMR (400 MHz,
CDCl3) δ: 8.70 (s, 1H), 8.42 (d, J＝7.2 Hz, 1H), 7.52－
7.40 (m, 3H), 4.12 (q, J＝8.0 Hz, 2H), 1.41 (t, J＝6.4
Hz, 3H).
Pentyl 3-(4-chlorophenyl)-2-cyanoacrylate (4t)[9e]
1
White solid. m.p. 78－79 ℃; H NMR (400 MHz,
Ethyl 3-(2-bromophenyl)-2-cyanoacrylate (4h)[9e]
Pale yellow solid. m.p. 68－70 ℃; 1H NMR (400 MHz,
CDCl3) δ: 8.64 (s, 1H), 8.17 (d, J＝6.0 Hz, 1H) 7.71 (d,
J＝9.2 Hz, 1H), 7.47 (t, J＝7.6 Hz, 1H), 7.39 (t, J＝7.6
Hz, 1H), 4.41 (q, J＝7.2 Hz, 2H), 1.42 (t, J＝7.2 Hz,
3H).
CDCl3) δ: 8.19 (s, 1H), 7.93 (d, J＝8.8 Hz, 2H), 7.48 (d,
J＝8.8 Hz, 3H), 4.32 (t, J＝6.8 Hz, 2H), 1.80－1.73 (m,
2H), 1.42－1.36 (m, 4H), 0.93 (t, J＝7.2 Hz, 3H).
Cyclohexyl 3-(4-bromophenyl)-2-cyanoacrylate
1
(4u)[9e] Yellow solid. m.p. 144－145 ℃; H NMR
(400 MHz, CDCl3) δ: 8.16 (s, 1H), 7.85 (d, J＝8.4 Hz,
2H), 7.64 (d, J＝8.4 Hz, 2H), 5.02－4.96 (m, 1H),
1.93－1.90 (m, 2H), 1.81－1.78 (m, 2H), 1.66－1.54
(m, 3H), 1.48－1.33 (m, 3H).
Ethyl 2-cyano-3-(2,4-dichlorophenyl)acrylate (4i)[11]
1
White solid. m.p. 81－82 ℃; H NMR (400 MHz,
CDCl3) δ: 8.61 (s, 1H), 8.22 (d, J＝8.0 Hz, 1H) 7.53 (d,
J＝4.0 Hz, 1H), 7.41－7.39 (m, 1H), 4.41 (q, J＝6.4 Hz,
2H), 1.41 (t, J＝7.2 Hz, 3H).
Cyclohexyl 2-cyano-3-(p-tolyl)acrylate (4v)[9e]
1
White solid. m.p. 82－83 ℃; H NMR (400 MHz,
Ethyl 2-cyano-3-(furan-2-yl)acrylate (4j)[9e] Yel-
low solid, m.p. 68－69 ℃; 1H NMR (400 MHz, CDCl3)
δ: 8.02 (s, 1H), 7.76 (s, 1H), 7.40 (d, J＝3.6 Hz, 1H),
6.67 (s, 1H), 4.36 (q, J＝7.2 Hz, 2H), 1.38 (t, J＝7.2 Hz,
3H).
CDCl3) δ: 8.20 (s, 1H), 7.90 (d, J＝8.0 Hz, 2H), 7.30 (d,
J＝7.6 Hz, 2H), 5.01－4.96 (m, 1H), 2.43 (s, 3H),
1.92－1.90 (m, 2H), 1.81－1.79 (m, 2H), 1.67－1.55
(m, 3H), 1.47－1.33 (m, 3H).
Methyl 2-oxo-2H-chromene-3-carboxylate (5a)[13]
Pale yellow solid. m.p. 96－97 ℃; 1H NMR (400 MHz,
DMSO) δ: 8.58 (s, 1H), 7.68－7.64 (m, 2H), 7.38－7.33
Ethyl 2-cyano-3-(4-(dimethylamino)phenyl)acry-
late (4k)[9e] Yellow solid. m.p. 124－125 ℃; 1H
Chin. J. Chem. 2015, 33, 1194—1198
© 2015 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
1195

Jing et al.
FULL PAPER
(m, 2H), 3.96 (s, 3H).
L-Proline and morpholine could not catalyze the reac-
tion, either (Entries 12－13, Table 1). The results pro-
vided by the entries using different catalysts implied the
particular applicability of TCT as the catalyst for this
three-component synthesis.
Ethyl 2-oxo-2H-chromene-3-carboxylate (5b)[13]
1
White solid. m.p. 92－94 ℃; H NMR (400 MHz,
CDCl3) δ: 8.26 (s, 1H), 7.98 (d, J＝7.2 Hz, 2H), 7.56－
7.49 (m, 2H), 4.92 (q, J＝7.2 Hz, 2H), 1.41 (t, J＝6.4
Hz, 3H).
Ethyl 7-methoxy-2-oxo-2H-chromene-3-carboxy-
late (5c)[14] Pale yellow solid. m.p. 120.5－121.1 ℃;
1H NMR (400 MHz, CDCl3) δ: 8.52 (s, 1H), 7.15 (d,
J＝8.8 Hz, 1H), 6.90 (d, J＝8.0 Hz, 1H), 6.82 (s, 1H),
4.40 (q, J＝6.8 Hz, 2H), 3.91 (s, 3H), 1.40 (t, J＝6.4 Hz,
3H).
Ethyl 6-methyl-2-oxo-2H-chromene-3-carboxy-
late (5d)[15] Pale yellow solid. m.p. 94.4－95.4 ℃; 1H
NMR (400 MHz, CDCl3) δ: 8.48 (s, 1H), 7.45 (d, J＝
8.4 Hz, 1H), 7.40 (s, 1H), 7.24 (d, J＝7.2 Hz, 1H), 4.42
(q, J＝7.2 Hz, 2H), 2.43 (s, 3H), 1.41 (t, J＝6.8 Hz,
3H).
Under the optimized conditions, the scope of this
three-component method was investigated by using
structurally diverse aryl aldehydes and alcohols. As out-
lined in Table 2, the present method exhibited excellent
tolerance to the stereoselective synthesis of cyano acry-
lates 4[16] by subjecting various aryl aldehydes and al-
cohols. The substituents such as halogen, alkyl, alkoxyl,
amino and heteroayl in the aldehyde component as well
as alcohols with alkyls of different length, branched
alkyls and cyclic alkyl also displayed expected com-
patibility to this three-component transformation. Ali-
phatic aldehyde such as propionaldehyde, however, was not
tolerated. Most products were provided with good to
excellent yields. While the property of the substituted
group in the benzaldehyde displayed no evident impact
Results and Discussion
At the beginning, the tentative experiment by em-
ploying benzaldehyde 1a, cyano acetanitrile 2a and
ethanol 3a in the presence of TCT was found to
smoothly provide cyano acrylate 4a with excellent yield
(Entry 1, Table 1). Systematic optimization on the reac-
tion conditions was then conducted. However, neither
varying the loading of TCT nor varying the reaction
temperature was able to improve the result (Entries 2－
5). During the attempts of screening catalysts, it was
found that FeCl3 and AlCl3 could catalyze the transfor-
mation, but provided 4a with remarkably lower yield
(Entries 6－7, Table 1). On the other hand, acidic cata-
lysts such as AcOH, p-TSA, TFA, benzoic acid were not
able to catalyze this reaction (Entries 8－11, Table 1).
Table 2 Three-component synthesis of different cyano acrylates
CO2R
TCT
neat
Ar CHO
NC
CONH2
ROH
3
1
Ar
CN
2a
4
Ar
R
Product Yielda/%
Ph
Et
4a
4b
4c
4d
4e
4f
84
79
89
81
80
74
85
91
82
79
81
84
89
88
89
90
74
75
73
75
67
69
—
—
4-ClC6H4
Et
4-BrC6H4
Et
4-MeC6H4
4-MeOC6H4
3-MeOC6H4
2-ClC6H4
Et
Et
Et
Et
4g
4h
4i
Table 1 Optimization on reaction conditionsa
2-BrC6H4
Et
CO2Et
2,4-Cl2C6H4
Furyl-2-yl
Et
TCT
neat
Ph CHO
NC
CONH2
EtOH
3a
Et
4j
1a
Ph
CN
2a
4a
4-Me2NC6H4
Et
4k
4l
Yieldb/%
84
2-Chloropyridin-3-yl
Et
Entry
1
T/℃
80
80
80
60
90
80
80
80
80
80
80
80
80
Catalyst/equiv.
TCT
Ph
Me
Me
Me
Me
4m
4nl
4o
4p
4q
4r
4s
2c
3d
4
TCT
TCT
TCT
TCT
FeCl3
AlCl3
AcOH
p-TSA
CF3COOH
Benzoic acid
L-Proline
62
72
56
64
62
60
Trace
nr
nr
4-ClC6H4
4-MeC6H4
4-MeOC6H4
Ph
5
6
7
8
9e
10
11
12
13
n-pro
i-pro
Ph
Ph
n-Bu
Ph
n-pentyl
4t
4-BrC6H4
4-MeC6H4
Ph
Cyclohexyl 4u
Cyclohexyl 4v
nr
nr
nr
Ph
Nob
Morpholine
a General conditions: 1a (1.0 mmol), 2a (1.0 mmol), 3a (2 mL),
catalyst (0.5 mmol), stirred for 12 h. b Yield of isolated product.
c TCT was 0.3 equiv. d TCT was 0.7 equiv. e nr＝no reaction.
Ph
t-Bu
No
a Yield of isolated product based on aldehyde. b MeCN was used
as solvent and heated at reflux.
1196
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© 2015 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2015, 33, 1194—1198

Direct Three-Component Synthesis of α-Cyano Acrylates
on the reaction results, the heteroaryl-based furyl-2-
aldehyde was found to give corresponding product 4j
with relatively inferior yield. On the other hand, the
structure of alcohol also affected the formation of re-
lated products, a tendency was that the alcohols with
bulky hindrance generally led to the production of cor-
responding alkyl acrylates with slightly lower yield
(4q－4v, Table 2). Bulkyl alcohol such as t-BuOH and
low nucleophilic phenol were not able to participate in
the expect synthesis, which further supports the fact that
the nucleophilicity of the O-nucleophile is crucial for
the reaction.
In order to further investigate the utility of the three-
component protocol, we subsequently employed salical-
dehyde as the aldehyde component to the standard con-
ditions in the presence of alcohols and α-cyano aceta-
mide. Interestingly, the formation of chromenones 5 was
achieved via further cascade cyano hydration and in-
tramolecular esterification after the formation of cyano
intermediate of type 4 (Scheme 2). Different salicalde-
hydes and alcohols were also tolerable to this synthesis
by providing products 5 with good yields.
O
TCT(0.5 equiv.)
80 oC
NH2
EtOH
3a (2 mL)
CN
6a (0.5 mmol)
O
(4)
O
CN
4a, 68%
posed and outlined in Scheme 3. The Knoevenagel
condensation between aldehyde and cyano acetamides
provides olefin intermediate 6. The incorporation of 6 to
TCT can easily take place to provide another intermedi-
ate 7, which facilitates the nucleophilic incorporation of
alcohol to yield acrylates 4. The water provided by the
Knoevenagel condensation enables the hydration of the
cyano group to allow the second cyclic esterification
process in the synthesis of products 5.
Scheme 3 The proposed reaction mechanism
Cl
N
N
Scheme 2 Three-component synthesis of chromenones
Cl
N
TCT
Cl
OH
Ar CHO
H2N
Knowevenagel
condensation
1
TCT
neat
O
R2OH
3
CHO
NC
CONH2
R1
2a
1
Ar
CN
NC
CONH2
2a
HCl
6
H2O
O
O
5a: R1 = H,
5b: R1 = H,
R2 = Me, 65%
R2 = Et,
5c: R1 = 4-MeO, R2 = Et,
5d: R1 = 5-Me, R2 = Et,
ROH
3
OR2
R1
N
67%
64%
69%
CN
CO2R
O
N
O
NH
5
NH2
Ar
4
N
N
Ar
CN
7
To probe the possible reaction mechanism, related
control experiments were designed. Firstly, the reaction
of aldehyde 1a with cyano acetamide 2a was conducted
by using CH3CN as solvent in the presence of TCT. As
expected, without the presence of alcohol, Knoevenagel
product 6a was obtained (Eq. 3). Subsequently, subject-
ing 6a with EtOH under the standard TCT catalytic
conditions smoothly led to the production of 4a with
fair yield (Eq. 4). The results implied that the Knoeve-
nagel condensation was the initial and key transforma-
tion in the three-component cascade reactions.
H2N
N
NH2
Conclusions
In conclusion, by means of employing TCT as an
organocatalyst, we have successfully established a new
approach for the three-component synthesis of various
alkyl acrylates. Besides the advantage of using simple
starting materials, the present method is valuable by
allowing easy synthesis of products with significantly
broader product diversity than conventional Knoevena-
gel approach because of the abundant resource of the
key alcohol component.
According to the acquired results, a general reaction
mechanism involving the promotion of TCT was pro-
CHO
NH2
Acknowledgement
NC
TCT (0.5 equiv.)
CH3CN, 80 oC
O
This work is financially supported by National
Natural Science Foundation of China (No. 21202064)
and Natural Science Foundation of Jiangxi Province
(No. 20151BAB203008).
1a (1.0 mmol)
2a (1.0 mmol)
O
(3)
NH2
CN
References
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Chin. J. Chem. 2015, 33, 1194—1198
© 2015 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
1197

Jing et al.
FULL PAPER
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