Microwave-assisted TsOH/SiO2-catalyzed one-pot synthesis of novel fluoro-substituted coumarin hydrazones under solvent-free conditions

Article abstract of DOI:10.1016/j.jfluchem.2014.07.004

Sixteen novel fluoro-substituted coumarin hydrazones were synthesized from a series of ethyl 2-hydroxy-2-(trifluoromethyl)-2H-chromene-3-carboxylates with supported acid catalyst under microwave-assisted one-pot and solvent free conditions. The structures

Full text of DOI:10.1016/j.jfluchem.2014.07.004

Journal of Fluorine Chemistry 168 (2014) 1–8
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Microwave-assisted TsOH/SiO2-catalyzed one-pot synthesis of novel
fluoro-substituted coumarin hydrazones under solvent-free
conditions
Guo-Yu Yang a, Jing-Tian Yang b, Cai-Xia Wang a, Su-Fang Fan a, Pu-Hui Xie a, Cui-Lian Xu a,
*
a College of Sciences, Henan Agricultural University, Zhengzhou 450002, PR China
b Ecology Security and Protection Key Laboratory of Sichuan Province, Mianyang 621000, PR China
A R T I C L E I N F O
A B S T R A C T
Article history:
Sixteen novel fluoro-substituted coumarin hydrazones were synthesized from a series of ethyl 2-
hydroxy-2-(trifluoromethyl)-2H-chromene-3-carboxylates with supported acid catalyst under micro-
wave-assisted one-pot and solvent free conditions. The structures of synthesized compounds were
confirmed by IR, 1H NMR, 13C NMR, HRMS and single crystal X-ray diffraction. Compared with the
reported reaction conditions, the new method has the advantages of shorter reaction time, simple work-
up procedure and environmental friendliness. The supported catalyst can be recovered easily and reused
with little change in its activity.
Received 30 April 2014
Received in revised form 5 July 2014
Accepted 7 July 2014
Available online 15 July 2014
Keywords:
Microwave-assisted
One-pot synthesis
Coumarin hydrazones
Fluorine
ß 2014 Elsevier B.V. All rights reserved.
1. Introduction
detection of a few biologically relevant anions in dimethylsulph-
oxide [7]. However, in contrast to 3-acetylcoumarin hydrazones
Coumarin and its derivatives were reported to show a wide
range of valuable biological activities in medicinal and pharma-
ceutical areas, such as antimicrobial, anti-inflammatory, anti-
tubercular, platelet antiaggregator, anti-tumor, and antioxidant
properties [1]. Moreover, several of them have excellent fluores-
cent properties because of their large stokes shift. Therefore, they
are used as dyes, sensors, and probes in the field of materials
engineering [2]. The incorporation of fluorine-containing groups in
the compounds often results in the improvement of their
physiological properties [3]. Therefore, various fluoro-substituted
coumarins have been recently synthesized [4]. The synthetic
methods of fluoro-substituted coumarins mostly employ tradi-
tional techniques, thereby restricting the development of novel
coumarin derivatives containing fluorine.
Among various coumarin derivatives, coumarin hydrazones
have been under investigation in recent years, due to their usages
as pharmaceuticals [5], fluorescence sensor [6], chemoreceptors
[7] and precursors for coumarin pyrazoles [8]. For example, 3-(2,4-
dinitrophenylhydrazonoethyl)coumarin could be acted as an
intramolecular charge transfer (ICT) probe for the naked-eye
which were abundantly prepared, few papers have been reported
about the synthesis and application of 3-trifluoroacetylcoumarin
hydrazones owing to the unavailable precursors, 3-trifluoroace-
tylcoumarins [9].
Recently, many new methodologies have been employed in
every aspect of organic chemistry to make up for some
deficiency of classical synthesis. For instance, the approach of
microwave-assisted one-pot synthesis under solvent-free con-
ditions has been preferred in scientific community because it is
an efficient, rapid, and green synthetic method, and has been
extensively exploited to synthesize many valuable organic
compounds in the synthetic chemistry [10]. Furthermore,
another protocol, the heterogenization of
a homogeneous
catalyst, also be commonly used to overcome the catalyst-
product separation problem [11].
Li et al. [9] reported the successful synthesis of novel coumarin
fluorescent dyes, which can be used as an optical chemosensor.
However, the reported method has its drawbacks, such as longer
reaction time, use of poisonous solvent (chlorobenzene), purifica-
tion of the intermediates, and difficult separation of the catalyst
from the products. Therefore, it is particularly important to find a
novel strategy to synthesize fluoro-substituted coumarin hydra-
zones which have potentially unique biological activity due to the
introduction of fluorine atoms.
*
Corresponding author. Tel.: +86 371 63558138.
E-mail address: xucuilian666@126.com (C.-L. Xu).
http://dx.doi.org/10.1016/j.jfluchem.2014.07.004
0022-1139/ß 2014 Elsevier B.V. All rights reserved.

2
G.-Y. Yang et al. / Journal of Fluorine Chemistry 168 (2014) 1–8
HN
NH2
CO2Et
COCF3
TSOH/SiO2
MW
TSOH/SiO2
MW
OH
HN
N
C
O
O
CF3
O
CF3
1a
2a
O
O
step 1
step 2
3a
Scheme 1. Synthetic route of the compound 3a.
In continuation of our work to develop the green synthesis of
To determine the role of the catalyst under the microwave
conditions, an experiment in the absence of the catalyst was
designed (Table 1, entry 4). Surprisingly, ester 1a was successfully
transformed into ketone 2a with a conversion of 81% at 252 W of
microwave irradiation (MWI) for 8 min even without adding the
catalyst in step 1. However, when phenylhydrazine directly
reacted with the ketone 2a, not being isolated from the mixture,
in the absence of the catalyst at 252 W of microwave irradiation
(MWI) for 6 min in step 2, only trace target compound 3a was
obtained. HPLC analysis shows that many byproducts appeared in
the reaction mixture. Obviously, the catalyst TsOH is essential for
the formation of the hydrazone 3a in step 2.
To show the advantages of novel method, our results and
reaction conditions for one-pot synthesis of coumarin hydrazone
3a were compared with the data of the literature method [12]
(Table 1). Coumarin hydrazone 3a was formed with a yield of 75%
at 252 W of microwave irradiation for 6 min in step 1 and 6 min in
step 2 in the presence of 1 mol% TsOH/SiO2 (Table 1, entry 5).
However, the yield of coumarin hydrazone 3a was only 43% when
ester 1a was refluxed for 4 h in chlorobenzene in step 1 in the
presence of TsOH (1 mol%) to transform into the ketone 2a and
then the isolated ketone 2a reacted with phenylhydrazine under
the refluxing temperature for 1 h using chlorobenzene as solvent
and TsOH (1 mol%) as catalyst in the step 2 (Table 1, entry 1) [9].
The main reason of the lower yield in the above literature method
was the loss of the ketone 2a during the process of isolation.
Moreover, the isolation process of ketone 2a was very time-
consuming and inconvenient. The results show that the advan-
tages of our synthetic method of coumarin hydrazone over the
reported method include a shorter time of implementation, the
nonuse of the poisonous solvent and the simple procedure for
the unnecessary isolation of the intermediate ketone 2a.
coumarin derivatives [12], here we report a novel, clean, and
simple protocol for the synthesis of fluoro-substituted coumarin
hydrazones through the reaction of fluoro-substituted coumarin
esters with various hydrazines in the presence of TsOH/SiO2 as a
supported catalyst under solvent-free conditions.
2. Results and discussion
The reaction of compound 1a with phenylhydrazine was chosen
as a model reaction (Scheme 1). The reaction was carried out in two
steps under solid acidic and microwave conditions. In step 1,
fluoro-substituted coumarin ester 1a was transformed into fluoro-
substituted coumarin ketone 2a. Then the ketone 2a, which was
not isolated from the mixture, directly reacted with phenylhy-
drazine to give the title compound 3a.
As a comparison, three reactions using ethanol or chloroben-
zene [9] as solvent were run to confirm the efficiency of the novel
method (Table 1, entries 1–3). It should be mentioned that when
ester 1a was refluxed for 6 h in ethanol in step 1 in the presence of
TsOH (10 mol%), no transformation of ester 1a into ketone 2a was
observed, even though the transformation is achieved in chloro-
benzene. To our surprise, hydrazone 3a was obtained with a yield
of 80% when ketone 2a reacted with phenylhydrazine in ethanol
under the refluxing temperature for 4 h in step 2. The results show
that the transformation of ester 1a into ketone 2a which is a key
reagent in the whole reaction needs a high temperature.
Table 1
Effect of catalyst loading on the synthesis of compound 3a.
Entry
Catalyst
(mol%)
Time
Conversion
(%)e
Time
Yield (%)f
(min)
(min)
To optimize the reaction conditions, the effect of catalyst
loading on the one-pot reaction for the synthesis of the hydrazone
3a was investigated by varying catalyst loading from 1 mol% to
40 mol% (Table 1, entries 5–9). The results show that the yield of
hydrazone 3a increased from 75% to 84% for 1–30 mol% of catalyst
Step 1
Step 2
1a
2b
3c
4d
5d
6d
7d
8d
9d
1
10
10
–
240
360
–
86
0
60
–
43
–
–
240
6
80
8
81
83
86
88
93
94
Trace
75
1
6
6
10
20
30
40
4
6
78
Table 2
4
6
81
Effect of microwave power on the synthesis of compound 3a.
4
6
84
Entry
MW
(W)
Time
Conversion
(%)a
Time
Yield (%)b
4
6
82
(min)
(min)
a
Reaction conditions: ester 1a (3.00 mmol), phenylhydrazine (3.60 mmol), TsOH
Step 1
Step 2
(0.03 mmol), chlorobenzene (30 mL), at the refluxing temperature.
b
Reaction conditions: ester 1a (3.00 mmol), TsOH (0.3 mmol), ethanol (30 mL), at
1
2
3
126
252
406
10
4
82
93
97
15
6
80
84
81
the refluxing temperature.
c
Reaction conditions: ketone 2a (3.00 mmol), phenylhydrazine (3.60 mmol),
2
5
TsOH (0.3 mmol), ethanol (30 mL), at the refluxing temperature.
d
Reaction conditions: ester 1a (1.00 mmol), phenylhydrazine (1.20 mmol), at
Reaction conditions: ester 1a (1.00 mmol), phenylhydrazine (1.20 mmol), TsOH/
252 W of microwave irradiation.
SiO2 (30 mol %).
e
a
Determined via HPLC analysis of the crude reaction mixture.
Determined via HPLC analysis of the crude reaction mixture.
f
b
Isolated yields.
Isolated yields.

G.-Y. Yang et al. / Journal of Fluorine Chemistry 168 (2014) 1–8
3
Table 3
Preparation of products 3a–3p by using various compounds 1a–1p and hydrazines
under microwave conditions.
Entry R1
R2
Product 3 Time/min
Step 1 Step 2
Yield/%a
1
2
H
H
3a
3b
3c
3d
3e
3f
4
3
9
7
9
4
6
4
4
4
4
4
4
4
4
4
6
85
89
92
97
96
88
84
73
57
61
46
43
78
75
68
87
6-Cl
H
3.5
5
3
6-Br
H
4
6,8-Dichloro
H
4
5
6,8-Dibromo
H
10
6
8-CH3O
H
10
4
7
8-CH3CH2O
H
3g
3h
3i
8
H
H
H
H
H
H
H
H
H
4-F
9
9
4-Cl
9
10
11
12
13
14
15
16
4-Br
3j
10
14
17
5
Fig. 1. Ortep plot of hydrate 3-(trifluoroacetyl)-2H-chromen-2-one 2a (CCDC
3-NO2
3,5-Dichloro
4-CH3O
4-CH3
4-CF3
2,4-Dimethyl
3k
3l
967230).
3m
3n
3o
3p
4
5
loading. While continuously increasing the catalyst loading
resulted in the decrease of the yield of hydrazone 3a to 82%.
Therefore, 30 mol % was considered as the optimum catalyst
loading (Table 1, entry 8).
4
Reaction conditions: esters 1 (3.00 mmol), TsOH/SiO2 (30 mol %), corresponding
phenylhydrazines (3.60 mmol), at 252 W of microwave irradiation.
a
Isolated yields.
Moreover, the effect of microwave power on the yields of
hydrazone 3a was also monitored from 126 W to 406 W (Table 2,
entries 1–3). It can been seen from Table 2 that 252 W achieved the
best yield (84%). Therefore, 252 W was chosen as the optimum
microwave power.
To confirm the structure of the ketone 2a which was
synthesized in the absence of the catalyst TsOH/SiO2 (Table 1,
entry 4), the light yellow crystals for X-ray crystal diffraction
measurement were grown by slowly evaporating the ethyl acetate
and n-hexane (1:10, v/v) solution of the ketone 2a. The structure of
the ketone 2a is shown in Fig. 1. The result shows that ketone 2a
underwent a nucleophilic addition reaction with water to yield
hydrate in the process of crystal growth because of the strong
electronegativity of trifluoromethyl group, which is consistent
with the reported literature [13]. The possible mechanism of
transformation is shown in Scheme 2. As shown in Scheme 2, under
the promotion of MWI, the pyran ring of ester 1a is opened to form
+
COOEt
OH
COOEt
O-
COOEt
O
O
OH
OH
A1(E)
CF3
CF3
CF3
1a
A2
A3
O-
CF3
O
O
+
CF3
CF3
COOEt
-EtOH
COOEt
O
O
2a
OH
OH
A4(Z)
Scheme 2. Possible transformation mechanism of ester 1a into ketone 2a without catalyst.
R2
R2
HN NH2
CO2Et
COCF3
TSOH/SiO2
MW
TSOH/SiO2
MW
R1
R1
OH
HN
N
O
O
CF3
O
C CF3
1
2
R1
O
O
3
step 1
step 2
Scheme 3. Synthetic route of the compounds 3a–3p.

4
G.-Y. Yang et al. / Journal of Fluorine Chemistry 168 (2014) 1–8
Table 4
the intermediate A. There are four possible forms (A1, A2, A3, and
Crystal data and experimental details for compound 3p.
A4) in compound A. A1 which is E configuration and A2 are the two
resonance forms. A2 can be automatically converted into A3 by
rotation of the carbon–carbon single bond. A3 and A4 which is Z
configuration are also the two resonance forms. The loss of ethanol
gives ketone 2a from A4 by addition and elimination of the
phenolic hydroxyl to COOEt group. The E ! Z isomerization
occurred during the transformation of ester 1a into ketone 2a.
Furthermore, the isomerization can be accelerated by the acid
catalyst [13]. By HPLC and HRMS analysis we also found that
fluoro-substituted coumarin ketone 2a is a very active compound.
Besides the easy formation of the hydrate, it also can easily reacted
with an alcohol, such as methanol, to yield an acetal in the absence
of acid.
Various fluoro-substituted coumarin hydrazones were effi-
ciently synthesized using this novel method (Scheme 3). Hydra-
zines and ketones transformed from esters were easily converted
into the target compounds with moderate to good yields (Table 3).
The structures of esters and hydrazines are influential in the yields
of products. The fluoro-substituted esters 1 containing electron-
withdrawing groups (Table 3, entries 2–5) and hydrazines
Empirical formula
Formula weight
C19H15F3N2O2
360.33
˚
Wavelength
0.71073 A
Crystal system, space group
Unit cell dimensions
Triclinic, P-1
˚
a = 20.3573(13) A,
a= 94.046(6)8
˚
b = 10.0941(9) A,
b
= 107.172(7)8
˚
c = 10.2639(7) A,
g= 111.493(8)8
3
˚
Volume
880.22(12) A
Z, calculated density
Absorption coefficient
F(0 0 0)
2, 1.360 mg/m3
0.111 mmꢀ1
372.0
Crystal size
0.3 mm ꢁ 0.25 mm ꢁ 0.2 mm
6.06–52.748
2u range for data collection
Limiting indices
ꢀ11 2 h 2 12,
ꢀ12 2 k 2 12, ꢀ12 2 l 2 12
10,466/3597 [R(int) = 0.0374]
99.8%
Reflections collected/unique
Completeness to theta = 26.00
Absorption correction
None
Data/restraints/parameters
Goodness-of-fit on F^2
3597/54/267
1.027
Final R indices [I > 2sigma(I)]
R indices (all data)
R1 = 0.0647, wR2 = 0.1513
R1 = 0.1153, wR2 = 0.1844
ꢀ3
˚
Largest diff. peak and hole
0.26 and ꢀ0.21 e. A
Fig. 2. Crystal structure of compound 3p (CCDC 997808).
Fig. 3. Hydrogen bonds in compound 3p.

G.-Y. Yang et al. / Journal of Fluorine Chemistry 168 (2014) 1–8
5
Table 5
Experiment on the recycling of the TsOH/SiO2 catalyst.
Cycle
1
2
3
4
5
Yield/%a
87
85
86
83
82
Reaction conditions: ester 1a (3.00 mmol), TsOH/SiO2 (30 mol %), phenylhydrazine
(3.60 mmol), at 252 W of microwave irradiation for 4 min in step 1 and 6 min in
step 2.
a
Isolated yield of product.
The synthesized compounds were characterized by IR, 1H NMR,
13C NMR, and HRMS. The results show that these spectra data are in
good accordance with their structures. To further verify the
structure of these compounds, single crystal of coumarin
hydrazone 3p suitable for X-ray crystal diffraction measurement
were obtained by slow evaporation of a solution of 3p in ethanol.
The crystal data and experimental details of compound 3p were
summarized in Table 4. The crystal structure, intermolecular
hydrogen bonding and molecular packing of compound 3p are
shown in Figs. 2–4, respectively. It can be seen that the coumarin
hydrazone 3p has E geometry about the C55N imine bond and the
coumarin ring and the substituted benzene ring are approximately
perpendicular owing to that the dihedral angle between two rings
is 80.9588 (Fig. 2). Moreover, the structure of 3p contains
intermolecular hydrogen bond between H at N(2) and the oxygen
O(2) (Fig. 3). Molecules of compound 3p are packed through the
Fig. 4. View of the molecular packing in compound 3p.
containing electron-donating groups (Table 3, entries 13–14)
showed increased yields. These results show that the electron-
withdrawing groups in esters 1 and the electron-donating groups
in hydrazines are favorable to the synthesis of fluoro-substituted
coumarin hydrazones. It is due to that the electron-withdrawing
groups in esters 1 increase the electrophilicity of the carbon atom
of the carbonyl group in COCF3 and the electron-donating groups in
hydrazines improve the nucleophilicity of the nitrogen atom of the
amino group.
intermolecular hydrogen bond and
(Fig. 4).
p–p stacking interactions
The possibility of recycling the catalyst was examined using the
reaction of ester 1a and phenylhydrazine in the presence of the
TsOH/SiO2 (30%) catalyst at 252 W of microwave irradiation for
4 min in step 1 and 6 min in step 2. The yields of compound 3a for
the various runs are listed in Table 5. As shown in Table 5 the TsOH/
SiO2 catalyst could be recycled in subsequent reactions with slight
decrease of the activity.
+
OH
OH
O
+
H+
NH2
CF3
CF3
CF3
NH
O
O
O
O
O
O
2a
A
+
OH2
OH
CF3
OH
CF3
+
H+
NH
NH
NH
-H+
NH2
CF3
NH
NH
O
O
O
O
O
O
D
B
C
-H2
O
F3C
F3C
+
NH
+
-H+
N
NH
CF3
NH
NH
NH
O
O
O
O
O
O
E
3a
Scheme 4. Plausible mechanism for hydrazone synthesis using TsOH/SiO2.

6
G.-Y. Yang et al. / Journal of Fluorine Chemistry 168 (2014) 1–8
A plausible mechanism leading to the formation of fluoro-
4.3. The isolation procedure for the compound 2a
substituted coumarin hydrazone 3a is outlined in Scheme 4. The
acid catalyst first protonates the oxygen atom of the carbonyl
group in COCF3 to produce the intermediate A. A is a resonance
hybrid of two resonance forms. The nucleophilic addition of
hydrazine to A yields the intermediate B. Loss of a proton from B
then gives the intermediate C. The addition of H+ to the hydroxy
group of C yields the intermediate D. The intermediate D loses
water to give the intermediate E. E is also a resonance hybrid of two
resonance forms. The subsequent removal of proton from the
intermediate E yields the product 3a. During the catalytic process,
the acid TsOH have two uses. First, the electrophilicity of carbonyl
group in COCF3 is increased because the proton attacks the ketonic
oxygen in the carbon addition process. Second, the acid accelerates
the removal of the hydroxyl group from the amino alcohol addition
product (C) in the elimination process.
Ethyl 2-hydroxy-2-(trifluoroacetyl)coumarin 1a (5 mmol),
TsOH/SiO2 (30 mol%) were thoroughly grinded in a mortar. The
mixture was placed in a little reaction tube and heated with a
microwave at 252 W. The sample was monitored by HPLC. After
completion of the transformation from 1a to 2a, the solid mixture
was extracted with methylene chloride (30 mL 3ꢁ). The CH2Cl2 of
the combined extract was removed under the reduced pressure.
The residue was recrystallized with ethyl acetate and n-hexane
(1:10, v/v) to afford the compound 2a.
Yield 80%, light yellow crystals, mp 115.3–116.4 8C. 1H NMR
(400 MHz, DMSO):
1H), 7.78 (td, J = 7.8, 1.2 Hz, 1H), 8.54 (s, 1H, CH55). 13C NMR
(100 MHz, CDCl3): = 116.04 (q, J = 288.4 Hz), 117.3, 117.8, 120.8,
d = 7.45–7.41 (m, 2H), 7.72 (dd, J = 8.0, 1.2 Hz,
d
125.3, 130.3, 135.7, 149.4, 155.5, 156.1, 179.0 (q, J = 37.0 Hz);
HRMS (ESI) calcd for C11H6O3F3 [M+H]+: m/z = 243.0191, found
243.0271.
3. Conclusion
4.4. Typical procedure for preparation of 3
In conclusion, we have developed a novel, greener, and efficient
method for the synthesis of new fluoro-substituted coumarin
hydrazones by using esters and hydrazines in the presence of
TsOH/SiO2 as a supported catalyst under microwave-assisted, one-
pot and solvent-free conditions. Compared with the reported
method, the current method provides hydrazones with moderate
and good yields in shorter reaction times and by simple procedure.
This method can also be used to synthesize other biological active
coumarin derivatives from available 3-(trifluoroacetyl) coumarins
as building blocks (work in progress).
Ethyl 2-hydroxy-2-(trifluoroacetyl)coumarins
1
(3 mmol),
TsOH/SiO2 (30 mol%) were thoroughly grinded in a mortar. The
mixture was placed in a little reaction tube and heated with a
microwave at 252 W. The sample was monitored by HPLC. After
completion of the transformation from 1 to 2, phenylhydrazines
(3.6 mmol) were added to the above mixture, grinded in a mortar,
and heated with a microwave at 252 W. When the reaction was
completed (traced by HPLC), the resulting mixture was extracted
with methylene chloride (20 mL 3ꢁ). The CH2Cl2 of the combined
extract was removed by reduced pressure distillation. The crude
product was recrystallized from ethyl alcohol and water (3:1, v/v)
to give compounds 3a–3p in moderate to good yields (43–97%).
4. Experimental
4.1. General
4.4.1. 3-(Phenylhydrazonotrifluoroethyl)coumarin (3a)
All starting materials and reagents used are commercially
available and were utilized without further purification. HPLC
analyses were performed on an Agilent 1200 HPLC (Chro-
matographic Column: XDB-C18 column with MeOH–H2O as
eluent) equipped with an Agilent 1200 UV detector. Melting
points were determined on an X-5 digital microscopic melting-
point apparatus (Beijing Tech Instruments Co., Beijing, China) and
are uncorrected. High resolution mass spectrometry were obtained
using a Waters Q-Tof MicroTM instrument. NMR were recorded on
Yield 85%, Chalky yellow powder, mp 194.8–196.4 8C. 1H NMR
(400 MHz, DMSO):
d = 6.94 (t, J = 8 Hz, 1H), 7.15 (d, J = 8 Hz, 2H),
7.30 (t, J = 8 Hz, 2H), 7.46 (t, J = 7.6 Hz, 1H), 7.55 (d, J = 8.4 Hz, 1H),
7.76 (t, J = 7.2 Hz, 1H), 7.86 (d, J = 7.6 Hz, 1H), 8.38 (s, 1H, CH55),
10.41 (s, 1H, NH). 13C NMR (100 MHz, DMSO):
d = 113.6, 116.6,
117.1, 118.8, 121.8, 121.9 (q, J = 269.9 Hz), 122.8 (q, J = 35.1 Hz),
125.1, 129.4, 129.6, 133.6, 143.7, 147.2, 154.1, 157.6; HRMS (ESI)
calcd for C17H11F3N2O2Na [M+Na]+: m/z = 355.0670, found
355.0673; IR (KBr, cmꢀ1):
n = 3436 (w), 3296 (m), 1700 (s),
a Bruker DPX-400 spectrometer. Chemical shifts (
ppm and J values are given in hertz. The IR spectra were recorded
d
) are reported in
1601 (m), 1562 (m), 1515 (w), 1495 (w), 1454 (w), 1342 (m), 1241
(s), 1188 (s), 1119 (s), 1064 (s), 976 (w), 951 (w), 752 (m), 693 (w),
458(w).
on a Nicolet IS10 FT-IR spectrometer and the frequencies are given
in cmꢀ1
. X-ray was recorded with Rigaku RAXIAS-IV type
diffractometer. X-ray data of compounds were collected by
4.4.2. 3-(Phenylhydrazonotrifluoroethyl)-6-(chloro)coumarin (3b)
Yield 89%, yellow powder, mp 175.1–177.3 8C. 1H NMR
graphite-monochromatized Mo K radiation at 291 K. The reaction
a
mixtures were heated with
a
microwave oven (Galanz,
(400 MHz, DMSO):
7.30 (t, J = 8 Hz, 2H), 7.60 (t, J = 7.6 Hz, 1H), 7.80 (dd, J = 8.8, 2.4 Hz,
1H), 7.98 (d, J = 2.4 Hz, 1H), 8.33 (s, 1H, CH55), 10.42 (s, 1H, NH). 13
NMR (100 MHz, DMSO): = 113.7, 118.4, 118.7, 120.1, 121.8 (q,
d = 6.95 (t, J = 8 Hz, 1H), 7.14 (d, J = 8 Hz, 2H),
G70F20CN3P-ZS (WO), Guangdong, China). The starting ethyl 2-
hydroxy-2-(trifluoroacetyl)coumarins 1 were prepared according
to described procedure [11c].
C
d
CCDC 967230 and CCDC 997808 contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge via http://www.ccdc.cam.ac.uk/data-request/cif.
J = 270.0 Hz), 121.9, 122.3 (q, J = 35.3 Hz), 128.5, 128.9, 129.5,
133.2, 143.6, 146.0, 152.8, 157.2; HRMS (ESI) calcd for
C
17H10ClF3N2O2Na [M+Na]+: m/z = 389.0281, found 389.0279; IR
(KBr, cmꢀ1
) n = 3431 (m), 1714 (w), 1604 (w), 1562 (w), 1336 (w),
4.2. The preparation of the catalyst TsOH/SiO2
1090 (s), 753 (w), 470 (m).
1.3 g (7.6 mmol) of p-methyl benzenesulfonic acid was
dissolved in 20 mL of distilled water. 15 g of pretreated silica gel
was added to the above solution with stirring. The mixture was
stirred for 12 h at room temperature. Then, the solvent was
removed by evaporation. The solid obtained was dried at 120 8C for
5 h to obtain the supported catalyst TsOH/SiO2 (8%, w/w).
4.4.3. 3-(Phenylhydrazonotrifluoroethyl)-6-(bromo)coumarin (3c)
Yield 92%, yellow powder, mp 171.0–173.5 8C. 1H NMR
(400 MHz, DMSO):
d = 6.95 (t, J = 7.2 Hz, 1H), 7.15 (d, J = 8.0 Hz,
2H), 7.30 (t, J = 8.0 Hz, 2H), 7.53 (d, J = 8.8 Hz, 1H), 7.91 (dd, J = 8.8,
2.0 Hz, 1H), 8.11 (d, J = 2.4 Hz, 1H), 8.32 (s, 1H, CH55), 10.42 (s, 1H,
NH). 13C NMR (100 MHz, DMSO)
d 113.6, 116.6, 118.3, 118.9, 120.5,

G.-Y. Yang et al. / Journal of Fluorine Chemistry 168 (2014) 1–8
7
121.8(q, J = 269.9 Hz), 121.9, 122.3 (q, J = 35.2 Hz), 129.5, 131.5,
135.9, 143.6, 145.8, 153.1, 157.1; HRMS (ESI): calcd for
C17H11BrF3N2O2 [M+H]+: m/z = 410.9956, found 410.9953; IR
117.1, 118.8, 122.0 (q, J = 270.0 Hz), 122.9 (q, J = 35.6 Hz), 125.3,
129.7, 133.8, 140.4, 147.3, 154.2, 156.5, 157.7, 158.9; HRMS (ESI)
calcd for C17H11F4N2O2 [M+H]+: m/z = 351.0757, found 351.0752;
IR (KBr, cmꢀ1
) n 3283 (m), 1699 (s), 1611 (m), 1520 (m), 1504 (m),
(KBr, cmꢀ1
)
n
= 3293 (w), 1717 (s), 1603 (s), 1560 (m), 1493
(m), 1476 (m), 1335 (w), 1304 (w), 1259 (m), 1187 (s), 1151 (m),
1109 (m), 1064 (m), 1067 (m), 960 (w), 934 (w), 923 (w), 814 (w),
777 (w), 752 (m), 683 (m).
1400 (m), 1213 (m), 1189 (m), 1119 (m), 1071 (m), 978 (w), 956
(w), 945 (w), 831 (m), 782 (w), 760 (m), 469 (w).
4.4.9. 3-(4-Chlorophenylhydrazonotrifluoroethyl)coumarin (3i)
Yield 57%, yellow powder, mp 176.0–177.4 8C. 1H NMR
4.4.4. 3-(Phenylhydrazonotrifluoroethyl)-6,8-(dichloro)coumarin
(3d)
(400 MHz, DMSO):
d = 7.16 (d, J = 8.8 Hz, 2H), 7.35 (d, J = 8.8 Hz,
Yield 97%, yellow solid, mp 197.0–199.1 8C. 1H NMR (400 MHz,
2H), 7.47 (d, J = 7.6 Hz, 1H), 7.55 (d, J = 8.4 Hz, 1H), 7.77
(t, J = 7.6 Hz, 1H), 7.86 (d, J = 8.0 Hz, 1H), 8.40 (s, 1H, CH55), 10.51
(s, 1H, NH); 13C NMR (100 MHz, DMSO):
d = 115.4, 116.9, 117.2,
DMSO):
d = 6.96 (t, J = 7.6 Hz, 1H), 7.15 (d, J = 8.0 Hz, 2H), 7.31
(t, J = 7.6 Hz, 2H), 7.98 (d, J = 2.0 Hz, 1H), 8.12 (d, J = 2.0 Hz, 1H),
8.36 (s, 1H, CH55), 10.43 (s, 1H, NH). 13C NMR (100 MHz, DMSO):
119.0, 122.0 (q, J = 270.0 Hz), 124.0 (q, J = 35.2 Hz), 125.4, 125.6,
d
= 113.7, 119.1, 121.0, 121.2, 121.7 (q, J = 33.8 Hz), 121.8
129.6, 129.9, 134.0, 142.9, 147.6, 154.4, 157.8; HRMS (ESI) calcd for
(q, J = 269.9 Hz), 122.0, 127.7, 128.8, 129.5, 132.6, 143.5, 145.8,
C
17H11ClF3N2O2 [M+H]+: m/z = 367.0461, found 367.0454; IR (KBr,
148.5, 156.4; HRMS (ESI) calcd for C17H10Cl2F3N2O2 [M+H]+:
cmꢀ1):
n = 3444 (m), 1694 (s), 1661 (s), 1638 (s), 1611 (s), 1455 (s),
1400 (m), 1250 (w), 1193 (w), 1159 (w), 1122 (w), 1092 (m), 1089
(w), 972 (w), 953 (w), 823 (m), 784 (w), 757 (w), 591 (w).
m/z = 401.0071, found 401.0075; IR (KBr, cmꢀ1):
n
= 3441 (w),
1715 (s), 1603 (s), 1556 (s), 1488 (m), 1456 (m), 1335 (w), 1245 (s),
1225 (s), 1185 (s), 1147 (s), 1100 (s), 1067 (s), 984 (w), 931 (w),
837 (w), 775 (w), 749 (w), 730 (w), 681 (w), 477 (m).
4.4.10. 3-(4-Bromophenylhydrazonotrifluoroethyl)coumarin (3j)
Yield 61%, yellow powder, mp 171.5–172.3 8C. 1H NMR
4.4.5. 3-(Phenylhydrazonotrifluoroethyl)-6,8-(dibromo)coumarin
(3e)
(400 MHz, DMSO): d = 7.12 (d, J = 8.4 Hz, 2H), 7.47 (t, J = 8.8 Hz,
3H), 7.55 (d, J = 8.4 Hz, 1H), 7.77 (t, J = 8.0 Hz, 1H), 7.87 (d,
J = 7.6 Hz, 1H), 8.40 (s, 1H, CH55), 10.51 (s, 1H, NH); 13C NMR
Yield 96%, yellow powder, mp 175.3–178.0 8C. 1H NMR
(400 MHz, CDCl3):
d
= 7.02 (t, J = 7.2 Hz, 1H), 7.17 (d, J = 8.0 Hz,
(100 MHz, DMSO): d = 113.4, 115.9, 116.9, 117.1, 119.0, 122.0 (q,
2H), 7.26–7.32 (m, 2H), 7.70 (d, J = 2.4 Hz, 1H), 7.91 (s, 1H, NH),
7.99 (d, J = 2.0 Hz, 1H), 8.31 (s, 1H, CH55). 13C NMR (100 MHz,
J = 270.0 Hz), 124.1 (q, J = 35.2 Hz), 125.4, 129.9, 132.5, 134.0,
143.3, 147.6, 154.4, 157.8; HRMS (ESI) calcd for C17H11BrF3N2O2
[M+H]+: m/z = 410.9956, found 410.9951; IR (KBr, cmꢀ1):
n = 3460
CDCl3):
d
= 111.5, 114.2, 118.0, 118.4, 120.2, 121.5 (q, J = 271.2 Hz),
121.7 (q, J = 35.2 Hz), 123.0, 129.3, 130.5, 139.0, 142.6, 144.8,
149.9, 156.6; HRMS (ESI) calcd for C17H10Br2F3N2O2 [M+H]+: m/
(m), 1714 (s), 1602 (s), 1484 (w), 1401 (s), 1246 (m), 1182 (m),
1120 (m), 1066 (m), 961 (w), 824 (w), 756 (m), 470 (w).
z = 488.9061, found 488.9084; IR (KBr, cmꢀ1):
n = 3276 (w), 1734
(s), 1572 (w), 1550 (w), 1498 (w), 1442 (w), 1333 (w), 1227 (w),
1180 (m), 1108 (m), 1067 (m), 960 (w), 755 (w), 696 (w), 471 (w).
4.4.11. 3-(3-Nitrophenylhydrazonotrifluoroethyl)coumarin (3k)
Yield 46%, yellow powder, mp 149.5–151.7 8C. 1H NMR
(400 MHz, DMSO):
7.75 (d, J = 6.4 Hz, 2H), 7.85 (d, J = 7.6 Hz, 1H), 7.89 (s, 1H), 8.42 (s,
1H, CH55), 10.75 (s, 1H, NH); 13C NMR (100 MHz, DMSO):
= 107.9,
d = 7.45 (d, J = 7.6 Hz, 1H), 7.54–7.58 (m, 3H),
4.4.6. 3-(Phenylhydrazonotrifluoroethyl)-8-(methoxy)coumarin (3f)
Yield 88%, yellow powder, mp 175.8–178.0 8C. 1H NMR
d
(400 MHz, DMSO):
7.15 (d, J = 8.4 Hz, 2H), 7.30 (t, J = 7.6 Hz, 2H), 7.40 (s, 2H),
7.44–7.46 (m, 1H), 8.35 (s, 1H, CH55), 10.39 (s, 1H, NH); 13C NMR
d
= 3.97 (s, 3H, CH3), 6.94 (t, J = 7.2 Hz, 1H),
116.0, 116.5, 116.7, 118.6, 119.6, 121.5 (q, J = 270.0 Hz), 125.3,
125.7 (q, J = 35.2 Hz), 129.8, 131.1, 133.9, 144.9, 147.6, 148.8,
154.2, 157.5; HRMS (ESI) calcd for C17H11F3N3O4 [M+H]+: m/
z = 378.0702, found 378.0696; IR (KBr, cmꢀ1):
n = 3427 (s), 1693
(100 MHz, DMSO):
d
= 56.5, 113.6, 115.7, 117.4, 119.3, 120.6,
121.8, 122.0 (q, J = 269.8 Hz), 122.8 (q, J = 32.2 Hz), 125.1, 129.5,
143.4, 143.7, 146.7, 147.4, 157.4; HRMS (ESI) calcd for
C18H14F3N2O3 [M+H]+: m/z = 363.0957, found 363.0952; IR (KBr,
(m), 1661 (m), 1613 (s), 1530 (m), 1454 (m), 1400 (m), 1350 (m),
1191 (w), 1125 (w), 1062 (w), 765 (w), 669 (w), 613 (w), 461 (w).
cmꢀ1
)
n
= 3433 (s), 3311 (m), 2974 (w), 1727 (s), 1598 (s), 1472
4.4.12. 3-(3,5-Dichlorophenylhydrazonotrifluoroethyl)coumarin (3l)
Yield 43%, yellow powder, mp 183.4–185.0 8C. 1H NMR
(m), 1350 (m), 1183 (s), 1105 (s), 929 (m), 756 (m), 696 (m), 466 (s).
(400 MHz, DMSO):
d = 7.11 (s, 3H), 7.47 (t, J = 7.6 Hz, 1H), 7.55
4.4.7. 3-(Phenylhydrazonotrifluoroethyl)-8-(ethoxy)coumarin (3g)
Yield 84%, yellow powder, mp 166.3–168.0 8C. 1H NMR
(d, J = 8.0 Hz, 1H), 7.78 (t, J = 8.0 Hz, 1H), 7.86 (d, J = 7.6 Hz, 1H),
8.42 (s, 1H, CH55), 10.61 (s, 1H, NH); 13C NMR (100 MHz, DMSO):
(400 MHz, DMSO):
d
= 1.44 (t, J = 6.8 Hz, 3H), 4.24 (q, J = 6.8 Hz,
d = 112.1, 116.4, 116.8, 118.6, 120.8, 121.4 (q, J = 270.7 Hz), 125.5,
2H), 6.94 (t, J = 7.2 Hz, 1H), 7.16 (d, J = 8.0 Hz, 2H), 7.31 (t, J = 7.6 Hz,
2H), 7.34–7.44 (m, 3H), 8.34 (s, 1H, CH55), 10.39 (s, 1H, NH); 13C
126.2 (q, J = 35.3 Hz), 129.8, 134.1, 135.1, 146.0, 147.8, 154.2,
157.4; HRMS (ESI) calcd for C17H10Cl2F2N2O2 [M+H]+: m/
z = 401.0071, found 401.0070; IR (KBr, cmꢀ1):
n = 3443 (s), 1707
NMR (100 MHz, DMSO):
d
= 14.8, 64.7, 113.6, 116.5, 117.3, 119.4,
120.5, 121.7, 121.9 (q, J = 270.0 Hz), 122.8 (q, J = 35.2 Hz), 125.0,
(m), 1593 (s), 1567 (m), 1454 (w), 1344 (w), 1252 (m), 1189 (s),
1078 (s), 803 (w), 758 (w), 475 (w).
129.4, 143.5, 143.7, 145.9, 147.3, 157.4; HRMS (ESI) calcd for
C
19H15F3N2O3Na [M+Na]+: m/z = 399.0932, found 399.0930; IR
(KBr, cmꢀ1
)
n
= 3282 (m), 2983 (w), 1707 (s), 1601 (s), 1470 (m),
4.4.13. 3-(4-Methoxylphenylhydrazonotrifluoroethyl)coumarin (3m)
Yield 78%, yellow powder, mp 159.0–159.8 8C. 1H NMR
1349 (m), 1278 (m), 1248 (m), 1189 (m), 1151 (m), 1099 (m), 1059
(m), 967 (w), 940 (w), 736 (m), 696 (m), 493 (s).
(400 MHz, DMSO):
d = 3.71 (s, 3H, CH3), 6.90 (d, J = 8.8 Hz, 2H),
7.08 (d, J = 8.8 Hz, 2H), 7.45 (t, J = 8.0 Hz, 1H), 7.53 (d, J = 8.4 Hz,
1H), 7.75 (td, J = 7.6, 1.6 Hz, 1H), 7.85 (dd, J = 7.6, 1.2 Hz, 1H), 8.34
(s, 1H, CH55), 10.26 (s, 1H, NH); 13C NMR (100 MHz, DMSO):
4.4.8. 3-(4-Fluorophenylhydrazonotrifluoroethyl)coumarin (3h)
Yield 73%, yellow powder, mp 180.3–182.2 8C. 1H NMR
(400 MHz, DMSO):
d
= 7.15 (d, J = 6.8 Hz, 4H), 7.46 (t, J = 7.2 Hz,
d = 55.4, 114.7, 114.8, 116.5, 117.3, 118.8, 121.3 (q, J = 35.2 Hz),
1H), 7.55 (d, J = 8.0 Hz, 1H), 7.77 (td, J = 7.6, 1.6 Hz, 1H), 7.86 (dd,
J = 7.8, 1.2 Hz, 1H), 8.37 (s, 1H, CH55), 10.43 (s, 1H, NH); 13C NMR
122.1 (q, J = 269.6 Hz), 125.0, 129.5, 133.5, 137.4, 147.0, 154.0,
154.6, 157.6; HRMS (ESI) calcd for C18H13F3N2O3Na [M+Na]+: m/
z = 385.0776, found 385.0778; IR (KBr, cmꢀ1):
n = 3455 (m), 3125
(100 MHz, DMSO):
d
= 115.0 (d, J = 7.8 Hz), 116.1, 116.3, 116.7,

8
G.-Y. Yang et al. / Journal of Fluorine Chemistry 168 (2014) 1–8
(m), 1705 (m), 1610 (m), 1520 (m), 1400 (s), 1355 (s), 1239 (m),
1193 (w), 1111 (m), 1070 (m), 977 (w), 825 (m), 782 (w), 760 (w),
669 (w).
Acknowledgements
This work was supported by the Education Foundation of Henan
Province (2006150011), the National Natural Science Foundation
(21102037), and Key Science and Technology Foundation of Henan
Province (112101110200).
4.4.14. 3-(4-Methylphenylhydrazonotrifluoroethyl)coumarin (3n)
Yield 75%, yellow powder, mp 172.5–174.0 8C. 1H NMR
(400 MHz, DMSO):
d = 2.24 (s, 3H), 7.05 (d, J = 8.0 Hz, 2H), 7.11
(d, J = 8.0 Hz, 2H), 7.45 (t, J = 7.6 Hz, 1H), 7.54 (d, J = 8.0 Hz, 1H),
7.76 (t, J = 8.0 Hz, 1H), 7.85 (d, J = 7.6 Hz, 1H), 8.36 (s, 1H, CH55),
Appendix A. Supplementary data
10.33 (s, 1H, NH); 13C NMR (100 MHz, DMSO):
d = 20.5, 113.6,
116.6, 117.2, 118.8, 122.0 (q, J = 35.1 Hz), 122.0 (q, J = 269.8 Hz),
125.1, 129.6, 129.9, 130.5, 133.6, 141.4, 147.1, 154.1, 157.6; HRMS
(ESI) calcd for C18H14F3N2O2 [M+H]+: m/z = 347.1007, found
347.1005; IR (KBr, cmꢀ1
) n = 3298 (s), 3038 (w), 2923 (w), 1707
Supplementary material related to this article can be found, in the
online version, at http://dx.doi.org/10.1016/j.jfluchem.2014.07.004.
(s), 1611 (s), 1587 (s), 1569 (s), 1524 (s), 1457 (m), 1352 (s), 1310
(m), 1298 (m), 1284 (m), 1247 (s), 1222 (s), 1186 (s), 1159 (s), 1142
(s), 978 (s), 957 (m), 815 (s), 758 (s), 610 (w).
References
[1] (a) G. Melagraki, A. Afantitis, O. Igglessi-Markopoulou, A. Detsi, M. Koufaki, C.
Kontogiorgis, D.J. Hadjipavlou-Litina, Eur. J. Med. Chem. 44 (2009) 3020–3026;
(b) T. Smyth, V.N. Ramachandran, W.F. Smyth, Int. J. Antimicrob. Agents 33 (2009)
421–426;
4.4.15. 3-(4-Trifluomethylphenylhydrazonotrifluoroethyl)coumarin
(3o)
´
(c) S. Vilar, E. Quezada, L. Santana, E. Uriarte, M. Yanez, N. Fraiz, C. Alcaide, E. Cano,
Yield 68%, yellow powder, mp 185.4–187.2 8C. 1H NMR
F. Orallo, Bioorg. Med. Chem. Lett. 16 (2006) 257–261;
(d) H. Chen, S. Li, Y.C. Yao, L.K. Zhou, J.P. Zhao, Y.J. Gu, K.R. Wang, X.L. Li., Bioorg.
Med. Chem. Lett. 23 (2013) 4785–4789;
(400 MHz, DMSO):
d = 7.30 (d, J = 8.4 Hz, 2H), 7.47 (t, J = 7.6 Hz,
1H), 7.56 (d, J = 8.4 Hz, 1H), 7.66 (d, J = 8.4 Hz, 2H), 7.78 (t,
J = 8.0 Hz, 1H), 7.87 (d, J = 7.6 Hz, 1H), 8.43 (s, 1H, CH55), 10.73 (s,
(e) Y. Zhang, B.Q. Zou, Z.F. Chen, Y.M. Pan, H.S. Wang, H. Liang, Yi.F X.H., Bioorg.
Med. Chem. Lett. 21 (2011) 6811–6815.
[2] (a) A. Mahapatra, K. Maiti, P. Sahoo, P.K. Nandi, J. Lumin. 143 (2013) 349–354;
(b) S. Zhu, W.Y. Lin, L. Yuan., Dyes Pigments 99 (2013) 465–471;
(c) R.M. Christie, K.M. Morgan, M. Saiful Islam, Dyes Pigments 76 (2008)
741–747;
(d) C.P. Kulatilleke, S.A. de Silva, Y. Eliav, Polyhedron 25 (2006) 2593–2596.
[3] (a) R.V. Patel, P. Kumari, D.P. Rajani, K.H. Chikhalia, J. Fluor. Chem. 132 (2011)
617–627;
1H, NH); 13C NMR (100 MHz, DMSO):
d = 113.6, 116.7(d, J = 2.6 Hz),
118.6, 119.5, 121.6 (q, J = 270.6 Hz), 121.7 (q, J = 31.7 Hz), 124.8 (q,
J = 269.2 Hz), 125.3, 125.5 (q, J = 34.9 Hz), 126.9 (q, J = 3.8 Hz),
129.7, 133.9, 146.9, 147.5, 154.1, 157.5; HRMS (ESI) calcd for
C
18H11F6N2O2 [M+H]+: m/z = 401.0725, found 401.0722; IR (KBr,
cmꢀ1):
n = 3298 (m), 1701 (s), 1611 (s), 1569 (m), 1531 (m), 1458
(b) H.K. Wu, J.Q. Zhong, H.M. Shen, H.X. Shi, J. Fluor. Chem. 156 (2013) 5–8;
(c) B.N. Prasanna Kumar, K.N. Mohana, L. Mallesha, J. Fluor. Chem. 156 (2013)
15–20.
(w), 1330 (s), 1251 (m), 1165 (s), 1110 (s), 1062 (s), 952 (w), 838 (s),
784 (w), 757 (s), 721 (w), 610 (w).
[4] (a) S.J. Yan, J. Lin, Chin. J. Org. Chem. 30 (2010) 465–468;
(b) X.J. Li, J.W. Zhao, Z.W. Wang, J.W. Han, J. Zhao, S.Z. Zhu, Tetrahedron 68 (2012)
8011–8017;
4.4.16. 3-(2,4-Dimethylphenylhydrazonotrifluoroethyl)coumarin
(3p)
(c) V.O. Iaroshenko, F. Erben, S. Mkrtchyan, A. Hakobyan, M. Vilches-Herrera, S.
Dudkin, A. Bunescu, A. Villinger, V.Y. Sosnovskikh, P. Langer, Tetrahedron 67
(2011) 7946–7955;
Yield 87%, yellow powder, mp 153.7–155.0 8C. 1H NMR
(d) X.B. Chen, H.T. Xi, X.Q. Sun, Chin. J. Org. Chem. 31 (2011) 544–547.
[5] T. Nasr, S. Bondock, M. Youns, Eur. J. Med. Chem. 76 (2014) 539–548.
[6] (a) D. Maity, D. Karthigeyan, T.K. Kundu, T. Govindaraju, Sens. Actuators B 176
(2013) 831–837;
(b) H.X. Xu, X.Q. Wang, C. Zhang, Y.P. Wu, Z.P. Liu, Inorg. Chem. Commun. 34
(2013) 8–11;
(c) J.M. An, Z.Y. Yang, M.H. Yan, T.R. Li, J. Lumin. 139 (2013) 79–83.
[7] K.K. Upadhyay, R.K. Mishra, A. Kumar, J.Z. Zhao, R. Prasad, J. Mol. Struct. 963 (2010)
228–233.
[8] I.I. Padilla-martinez, I.Y. Flores-Larios, E.V. Garcia-Baez, J. Gonzalez, A. Cruz, F.J.
Martinez-Martinez, Molecules 16 (2011) 915–932.
[9] H.Q. Li, L. Cai, J.X. Li, Y.X. Hu, P.P. Zhou, J.M. Zhang, Dyes Pigments 91 (2011)
309–316.
[10] (a) A. Rauf, S. Sharma, S. Gangal, Arkivoc 16 (2007) 137–147;
(b) J.S. Yadav, B.V.S. Reddy, R.S. Rao, V. Naveenkumar, K. Nagaiah, Synthesis-
Stuttgart 10 (2003) 1610–1614;
(400 MHz, DMSO):
d = 2.18 (s, 3H, CH3), 2.23 (s, 3H, CH3), 6.95
(s, 1H), 6.99 (d, J = 8.4 Hz, 1H), 7.17 (d, J = 8.4 Hz, 1H), 7.44 (t,
J = 7.6 Hz, 1H), 7.52 (d, J = 8.4 Hz, 1H), 7.73 (td, J = 7.8, 1.2 Hz, 1H),
7.86 (dd, J = 7.6, 1.2 Hz, 1H), 8.38 (s, 1H, CH55), 9.58 (s, 1H, NH); 13
C
NMR (100 MHz, DMSO):
d = 17.62, 20.42, 116.5, 117.2, 117.4,
118.8, 122.1 (q, J = 270.1 Hz), 122.4 (q, J = 34.8 Hz), 125.0, 125.6,
127.3, 129.4, 131.6, 131.9, 133.4, 139.3, 146.5, 154.0, 157.6; HRMS
(ESI) calcd for C19H16F3N2O2 [M+H]+: m/z = 361.1164, found
361.1161; IR (KBr, cmꢀ1):
(s), 1568 (s), 1520 (s), 1489 (m), 1458 (s), 1349 (s), 1300 (m), 1260
(s), 1237 (m), 1219 (m), 1165 (s), 1145 (s), 1124 (s), 1069 (m), 976
(m), 957 (m), 826 (s), 779 (w), 760 (s), 746 (w).
n = 3293 (w), 3031 (w), 1707 (s), 1608
(c) J.A. Seijas, M.P. Vazquez-Tato, J. Crecente-Campo, Tetrahedron 64 (2008)
9280–9285;
5. The reusability of the catalyst
(d) A.S. Ren, X.J. Yang, J. Hong, X.C. Yu, Synlett 15 (2008) 2376–2378;
(e) M.B.M. Reddy, M.A. Pasha, Synth. Commun. 40 (2010) 1895–1898.
[11] (a) G. Mohammadi Ziarani, A.R. Badiei, M. Azizi, Sci. Iran 18 (2011) 453–457;
(b) X.Y. Sheng, J.R. Gao, L. Han, Y.X. Jia, W.J. Sheng, Microporous Mesoporous
Mater. 143 (2011) 73–77;
After completing the reaction from ester 1a to hydrazone 3a
(3.00 mmol ester 1a, 30 mol % TsOH/SiO2, 3.60 mmol phenylhy-
drazine, at 252 W of microwave irradiation for 4 min in step 1 and
6 min in step 2), the resulting mixture was extracted with
methylene chloride (20 mL 3ꢁ). Then the methylene chloride
was removed from the combined extract under reduced pressure.
The product was recrystallized from ethyl alcohol and water (3:1,
v/v). The recovered catalyst was thoroughly washed with
methylene chloride until the products were completely removed
from the catalyst (detected on TLC). Then the catalyst was dried in
an oven at 120 8C for 4 h. The dried catalyst was weighed and
reused for the next run. In every run the same ratio of the ester-to-
catalyst and ester-to-hydrazine was kept.
(c) K. Niknam, D. Saberi, M.N. Sefat, Tetrahedron Lett. 51 (2010) 2959–2962;
(d) G.H. Mahdavinia, M.A. Bigdeli, Y.S. Hayeniaz, Chin. Chem. Lett. 20 (2009)
539–541;
(e) R. Maggi, G. Martra, C.G. Piscopo, G. Alberto, G. Sartori, J. Catal. 294 (2012)
19–28.
[12] (a) G.Y. Yang, C.X. Wang, S.F. Fan, L.J. Zhao, D. Wang, C.L. Xu, Synth. Commun. 43
(2013) 1263–1269;
(b) G.Y. Yang, J.T. Yang, C.X. Wang, S.F. Fan, P.H. Xie, C.L. Xu, Heterocycles 87
(2013) 1327–1336;
(c) C.L. Xu, G.Y. Yang, C.X. Wang, S.F. Fan, L.X. Xie, Y. Gao., Molecules 18 (2013)
11964–11977.
[13] D.L. Chizhov, V.Y. Sosnovskikh, M.V. Pryadeina, Y.V. Burgart, V.I. Saloutin, V.N.
Charushin, Synlett 2 (2008) 281–285.