FeCl3-promoted synthesis of 1,3,4-thiadiazoles under combined microwave and ultrasound irradiation in water

Article abstract of DOI:10.1007/s00706-012-0846-x

An eco-friendly and efficient synthesis of substituted 1,3,4-thiadiazole derivatives has been developed. This aqueous heterogeneous approach proceeds smoothly and quickly under combined microwave and ultrasound irradiation in the presence of FeCl₃.

Full text of DOI:10.1007/s00706-012-0846-x

Monatsh Chem (2013) 144:681–686
DOI 10.1007/s00706-012-0846-x
ORIGINAL PAPER
FeCl3-promoted synthesis of 1,3,4-thiadiazoles under combined
microwave and ultrasound irradiation in water
•
Huangdi Feng Xili Ying Yanqing Peng Erik V. Van der Eycken
•
•
•
•
Chuanduo Liu Shanshan Zhao Gonghua Song
•
Received: 29 February 2012 / Accepted: 19 August 2012 / Published online: 27 September 2012
Ó Springer-Verlag 2012
Abstract An eco-friendly and efficient synthesis of
substituted 1,3,4-thiadiazole derivatives has been devel-
oped. This aqueous heterogeneous approach proceeds
smoothly and quickly under combined microwave and
ultrasound irradiation in the presence of FeCl3.
Over the years, heterocycles have become important
synthetic intermediates that have found a variety of
applications in medicinal, agricultural, and materials
chemistry [11–13]. Although many important types of
heterocyclic compounds have been synthesized in aqueous
media [14–20], the synthesis of new and important types of
heterocyclic compounds in water still attracts wide atten-
tion. 1,3,4-Thiadiazoles are very important heterocycles
with great applicability in medicinal chemistry, agro-
chemistry, and so on. This core structure can be found in
compounds with wide-ranging biological applications
[21–27]. The literature reveals that most traditional syn-
thetic methods for the synthesis of 1,3,4-thiadiazole
derivatives suffer from one or more drawbacks, such as
laborious work-up, strongly acidic conditions, low yields,
and the use of organic solvents [28–32]. As part of
our continued interest in the application of combined
microwave and ultrasound irradiation (CMUI)-assisted
heterogeneous reactions [33–35], we here report a mild,
efficient, and environmentally benign approach for the
synthesis of substituted 1,3,4-thiadiazoles via intramolec-
ular cyclization or the three-component reaction of an
aldehyde, a phenylisothiocyanate, and hydrazine hydrate
under CMUI in a heterogeneous aqueous medium.
Keywords Microwave-assisted synthesis Á Ultrasound Á
Heterogeneous Á Water Á Oxidations
Introduction
The concept of ‘‘ideal chemistry’’ has been widely adopted
to meet the fundamental scientific principles of protecting
human health and the environment while simultaneously
achieving commercial value [1]. In this regard, the
replacement of organic solvents is one of the most
important goals. Although an ideal and universal green
solvent for all problems does not exist, water is a widely
explored green solvent [2–4]. Clearly, the development of a
sustainable approach for synthesizing biologically active
molecules is very important. In this field, combined
microwave and ultrasound irradiation has proven to be a
powerful tool for both speeding up chemical optimizations
and for efficiently preparing new compounds [5–10].
Results and discussion
H. Feng Á X. Ying Á Y. Peng Á C. Liu Á S. Zhao Á G. Song (&)
Shanghai Key Laboratory of Chemical Biology, East China
University of Science and Technology, 130 Meilong Road,
Shanghai 200237, China
In our initial study, we employed 1-benzylidenethiosemi-
carbazide (1a) as a model substrate in combination with 3
equiv. of FeCl3 to evaluate the efficiency of microwave and
ultrasound irradiation (Table 1, entries 1–3). The results
showed that a combination of microwave irradiation
at 200 W and ultrasound irradiation at 50 W gave the
highest yield after 3 min (Table 1, entry 1). Several control
e-mail: ghsong@ecust.edu.cn
H. Feng Á E. V. Van der Eycken
Laboratory for Organic and Microwave-Assisted Chemistry
(LOMAC), Department of Chemistry, Katholieke Universiteit
Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium
123

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H. Feng et al.
Table 1 Optimizing the conditions
N
N
H
N
NH2
FeCl3
N
NH2
S
S
H2O, reflux
1a
2a
Entry
FeCl3/equiv.
Method
Time/min
Yielda/%
1
2
3
MW (200 W) ? US (50 W)
MW (150 W) ? US (50 W)
MW (200 W) ? US (40 W)
US (50 W) ? oil bath heating
MW (200 W)
3
86
77
63
47
28
45
85
69
82
56
3
3
3
3
3
4
3
90
20
240
3
5
3
6
3
Conventional reflux
7
2
MW (200 W) ? US (50 W)
MW (200 W) ? US (50 W)
MW (200 W) ? US (50 W)
MW (200 W) ? US (50 W)
8
1.5
3
3
9
4
10
3
2
Reactions were performed under reflux using 1-benzylidenethiosemicarbazide (1.0 mmol), FeCl3, and 6 cm3 water
a
Isolated yield
experiments were carried out in order to demonstrate the
superiority of CMUI over other methods (Table 1, entries 1,
4–6). The results clearly show that CMUI achieved the best
results in terms of both reaction time and yield. This drastic
acceleration effect may be attributed to a combination of
enforced heat transfer due to microwave irradiation and
intensive mass transfer at phase interfaces caused by soni-
cation. Regarding the concentrations of FeCl3, we found that
lower yields were obtained when using less than 3 equiv. of
FeCl3 (Table 1, entries 7, 8). As a compromise between eco-
efficiency and yield, 2 equiv. of FeCl3 were adopted for
further elaboration. The desired 5-phenyl-1,3,4-thiadiazol-
2-amine (2a) was obtained in 82 % yield after an increased
irradiation time of 4 min (Table 1, entry 9), while reducing
the irradiation time to 2 min resulted in a decreased yield of
56 % (Table 1, entry 10).
Table 2 Scope and limitations of the protocol
N
N
H
N
NH2
FeCl3, H2O
CMUI, reflux
N
NH2
R
S
R
S
1
2
Entry
R
Product 2 Reported yield/%
Yielda/%
1
2
3
4
5
6
7
8
H
2a
2b
2c
2d
2e
2f
65 [26]
80 [21]
58 [23]
70 [26]
84 [22]
62 [26]
60 [26]
85
90
89
85
84
73
88
4-F
3-NO2
4-Cl
2,4-di-Cl
4-CH3
4-OCH3
2g
3,4-OCH2O– 2h
Not mentioned [30] 86
Havingidentified the optimalconditions(Table 1, entry 7),
we next investigated the scope and limitation of the process
with variously substituted1-benzylidenethiosemicarbazides1
(Table 2). Both electron-withdrawing (Table 2, entries 2–5)
and electron-donating (Table 2, entries 6–8) groups were well
tolerated, although a slightly lower yield was obtained with a
para-methyl substituent (Table 2, entry 6).
Reactions were performed under reflux using 1 (1.0 mmol), FeCl3
(2.0 mmol), and 6 cm3 water for 3 min under CMUI (microwave:
200 W; ultrasound: 50 W)
a
Isolated yields
reacted rapidly and gave a high yield of 4 (Table 3, entries
6–8), while those with electron-withdrawing groups required
longer reaction times and gave lower yields (Table 3, entries
2–5). Interestingly, when the 1,3,4-thiadiazol-2-amines 2c
and 2e were used, increased yields of the desired compounds
4c and 4e were obtained when 2 mol % of concentrated
hydrochloric acid was added as a catalyst.
Considering that Schiff bases with heterocycles express
biological activities [36, 37], we next evaluated the scope of
the CMUI technology for the synthesis of 5-aryl-N-arylidene-
1,3,4-thiadiazol-2-amines 4 employing a variety of 5-substi-
tuted 1,3,4-thiadiazol-2-amines 2 in combination with
4-hydroxybenzaldehyde (3, Table 3). The result showed that
the1,3,4-thiadiazol-2-amines2 withelectron-donatinggroups
123

FeCl3-promoted synthesis of 1,3,4-thiadiazoles
683
Table 3 Synthesis of 5-aryl-N-arylidene-1,3,4-thiadiazol-2-amines
N
N
N
N
CHO
H2O
+
N
NH2
R
R
S
S
CMUI, reflux
HO
OH
2
3
4
Entry
R
Product 4
Time/min
Reported yield/%
Yielda/%
1
2
3
4
5
6
7
8
H
4a
4b
4c
4d
4e
4f
3
8
70 [28]
89
4-F
–
87
32 (88b)
3-NO2
4-Cl
10
10
10
30
3
Not mentioned [33]
–
77
24 (77c)
98
2,4-di-Cl
4-CH3
4-OCH3
–
–
4g
4h
65 [31]
–
90
3,4-OCH2O–
3
92
A mixture of 2 (1.0 mmol), 3 (1.0 mmol), and 6 cm3 water was brought to reflux upon CMUI (microwave: 200 W; ultrasound: 50 W) for the
indicated time (monitored by TLC)
a
Isolated yields
b
Added HCl and reacted for 5 min
c
Added HCl and reacted for 10 min
Encouraged by these results, we tried to explore the
CMUI approach for synthesizing other substituted 1,3,4-
thiadiazoles. Based on the literature [38–41], we found that
1,3,4-thiadiazoles could be obtained via a one-pot three-
component reaction of an aldehyde, a phenylisothiocya-
nate, and hydrazine hydrate in water under CMUI
(Table 4). Therefore, we next investigated the application
of our previous protocol applying a variety of aldehydes 5
containing electron-withdrawing (Table 4, entries 2–5) or
electron-donating (Table 4, entries 6–13) substituents. To
our satisfaction, all reactions worked well and provided the
desired products 8a–8m in good yields.
were carried out in a professional TCMC-102 microwave
apparatus (Nanjing Lingjiang Technological Development
Company, Nanjing, China) operating at a frequency of
2.45 GHz with continuous irradiation power from 0.0 to
500 W, and a FS-250 professional ultrasound apparatus
(Shanghai S.X. Ultrasonics, Shanghai, China) operating at a
frequency of 20 kHz with controllable irradiation power
from 10 to 100 W. The reactions were carried out in a 15 cm3
two-necked Pyrex flask placed in the microwave cavity with
the tip of the detachable horn immersed just under the liquid
surface. TLC analysis was performed on aluminum-backed
plates SIL G/UV254. The products were purified by filtration
and were identified by 1H NMR (DMSO-d6, 400 MHz) and
In conclusion, we have developed an efficient, simple,
and green procedure for the synthesis of 5-aryl-N-arylid-
ene-1,3,4-thiadiazol-2-amines and 5-aryl-N-phenyl-1,3,4-
thiadiazol-2-amines employing a FeCl3-promoted process
under combined microwave and ultrasound irradiation
(CMUI) in water. The CMUI provides extremely efficient
dielectric heating along with intensive mass transport in
these heterogeneous systems, making it an excellent
approach for achieving environmentally friendly and effi-
cient organic synthesis.
1
MS (EI). All new products were identified by H and 13C
NMR (DMSO-d6, 400 MHz) and high-resolution mass
spectra (EI). Melting points were measured with a digital
melting-point apparatus (WRR, Shanghai Precision and
Scientific Instruments, Shanghai, China).
General experimental procedure for the synthesis
of 5-aryl-1,3,4-thiadiazol-2-amines 2
A mixture of 1-arylidenethiosemicarbazide 1 (1 mmol),
FeCl3 (2 mmol), and 6 cm3 water was subjected to
microwave–ultrasound activation conditions. The ultra-
sound and microwave sources were switched on
successively (power levels: ultrasound 50 W, microwave
200 W). The mixture was irradiated simultaneously with
microwaves and ultrasound for 3 min. The suspension was
Experimental
All solvents and reagents were purchased from commercial
sources and were used without prior purification. All com-
bined microwave and ultrasound irradiation experiments
123

684
H. Feng et al.
Table 4 Synthesis of 5-aryl-N-phenyl-1,3,4-thiadiazol-2-amines
CHO
NCS
N N
FeCl3,H2O
R
+
+
NH2NH2 H2O
R
N
H
CMUI, reflux
S
8
5
6
7
Entry
R
H
Product 8
Time/min
Reported yield/%
Yielda/%
1
8a
8b
8c
8d
8e
8f
4
85 [40]
79
75
76
74
74
83
71
76
75
73
85
85
84
2
4-CN
3
–
3
3-NO2
3.5
4
Not mentioned [42]
4
2,4-di-Cl
3-F
72 [43]
–
5
4
6
3-OCF3
2.5
3.5
4
–
7
4-OCH3
3,5-di-OCH3
3,4,5-tri-OCH3
4-CH3
8g
8h
8i
85 [44]
–
8
9
3.5
3.5
3.5
4
78 [30]
64 [44]
–
10
11
12
13
8j
4-CH(CH3)2
4-OH
8k
8l
87 [45]
75 [46]
2-OH
8m
4
A mixture of 5 (1.0 mmol), 6 (1.0 mmol), 7 (1.0 mmol), FeCl3 (2.0 mmol), and 6 cm3 water was brought to reflux upon CMUI (microwave:
200 W; ultrasound: 50 W) for the indicated time (monitored by TLC)
a
Isolated yields
130.2, 133.2, 163.5, 164.5, 165.4, 169.1, 174.8 ppm;
HRMS (EI): m/z calc’d for C15H10FN3OS (M ? H)
299.0529, found 299.0529.
filtered and the residue was washed with water and ethanol,
after which the residue was recrystallized from ethanol and
dried under vacuum to obtain the products 2.
4-[[5-(4-Chlorophenyl)-1,3,4-thiadiazol-2-ylimino]-
methyl]phenol (4d, C15H10ClN3OS)
General experimental procedure for the synthesis
of 5-aryl-N-arylidene-1,3,4-thiadiazol-2-amines 4
1
Yellow solid; m.p.: 251.3–252.4 °C; H NMR (400 MHz,
DMSO-d6): d = 6.94 (d, J = 8.4 Hz, 2H), 7.63 (d,
J = 8.4 Hz, 2H), 7.93 (d, J = 8.8 Hz, 2H), 7.98 (d,
J = 8.4 Hz, 2H), 8.89 (s, 1H), 10.65 (s, 1H) ppm; 13C
NMR (100 MHz, DMSO-d6): d = 116.3, 126.2, 128.4,
130.0, 133.3, 134.4, 136.3, 163.8, 164.5, 169.2, 175.0 ppm;
HRMS (EI): m/z calc’d for C15H10ClN3OS (M ? H)
315.0233, found 315.0236.
A mixture of 5-aryl-1,3,4-thiadiazol-2-amines 2 (1 mmol),
4-hydroxy-benzaldehyde 3 (1 mmol), and 6 cm3 water was
subjected to microwave-ultrasound activation conditions.
The ultrasound and microwave sources were switched on
successively (power level: ultrasound 50 W, microwave
200 W). The mixture was irradiated simultaneously with
microwaves and ultrasound for 3 min. The suspension was
filtered and the residue was washed with water and ethanol,
after which the residue was recrystallized from ethanol and
dried under vacuum to obtain the products 4.
4-[[5-(2,4-Dichlorophenyl)-1,3,4-thiadiazol-2-ylimino]-
methyl]phenol (4e, C15H9Cl2N3OS)
1
Yellow solid; m.p.: 255.1–256.6 °C; H NMR (400 MHz,
4-[[5-(4-Fluorophenyl)-1,3,4-thiadiazol-2-ylimino]-
methyl]phenol (4b, C15H10FN3OS)
DMSO-d6): d = 6.95 (d, J = 8.8 Hz, 2H), 7.65 (m, 1H),
7.92–7.95 (m, 3H), 8.21 (d, J = 8.4 Hz, 1H), 8.96 (s, 1H),
10.64 (s, 1H) ppm; 13C NMR (100 MHz, DMSO-d6):
d = 116.7, 126.3, 128.8, 130.7, 132.7, 132.3, 133.3, 135.0,
136.6, 156.0, 163.6, 169.4, 176.3 ppm; HRMS (EI):
m/z calc’d for C15H9Cl2N3OS (M ? H) 348.9842, found
348.9848.
1
Yellow solid; m.p.: 261.2–262.0 °C; H NMR (400 MHz,
DMSO-d6): d = 6.94 (d, J = 8.4 Hz, 2H), 7.41 (t,
J = 8.4 Hz, 2H), 7.93 (d, J = 8.8 Hz, 2H), 8.00–8.03
(m, 2H), 8.88 (s, 1H), 10.63 (s, 1H) ppm; 13C NMR
(100 MHz, DMSO-d6): d = 116.7, 117.2, 126.2, 127.3,
123

FeCl3-promoted synthesis of 1,3,4-thiadiazoles
685
4-[[5-(4-Methylphenyl)-1,3,4-thiadiazol-2-ylimino]-
methyl]phenol (4f, C16H13N3OS)
164.5 ppm; HRMS (EI): m/z calc’d for C14H10FN3S
(M ? H) 271.0579, found 271.0577.
1
Yellow solid; m.p.: 249.7–250.8 °C; H NMR (400 MHz,
N-Phenyl-5-[3-(trifluoromethoxy)phenyl]-1,3,4-thiadiazol-
2-amine (8f, C15H10F3N3OS)
DMSO-d6): d = 2.38 (s, 3H), 6.94 (d, J = 8.4 Hz, 2H),
7.37 (d, J = 8.0 Hz, 2H), 7.84 (d, J = 8.0 Hz, 2H), 7.92
(d, J = 8.4 Hz, 2H), 8.87 (s, 1H), 10.62 (s, 1H) ppm; 13C
NMR (100 MHz, DMSO-d6): d = 21.8, 116.7, 126.3,
127.6, 127.9, 130.5, 133.1, 141.8, 163.4, 165.7, 168.9,
174.3 ppm; HRMS (EI): m/z calc’d for C16H13N3OS
(M ? H) 295.0779, found 295.0760.
1
White solid; m.p.: 193.8–195.6 °C; H NMR (400 MHz,
DMSO-d6): d = 7.04 (t, J = 7.0 Hz, 1H), 7.38 (t,
J = 7.6 Hz, 2H), 7.51 (d, J = 9.3 Hz, 2H), 7.66 (d,
J = 8.1 Hz, 2H), 8.01 (d, J = 9.3 Hz, 2H), 10.58 (br s,
1H) ppm; 13C NMR (100 MHz, DMSO-d6): d = 118.1,
122.2, 122.7, 129.2, 129.6, 130.0, 140.8, 149.7, 156.5,
164.9 ppm; HRMS (EI): m/z calc’d for C15H10F3N3OS
(M ? H) 337.0497, found 337.0490.
4-[[5-(Benzo[d][1,3]dioxol-5-yl)-1,3,4-thiadiazol-2-ylimino]-
methyl]phenol (4h, C16H11N3O3S)
1
Yellow solid; m.p.: 250.2–251.1 °C; H NMR (400 MHz,
5-(3,5-Dimethoxyphenyl)-N-phenyl-1,3,4-thiadiazol-2-
amine (8h, C16H15N3O2S)
DMSO-d6): d = 6.15 (s, 2H), 6.94 (d, J = 8.8 Hz, 2H),
7.09 (d, J = 8.0 Hz, 1H), 7.46 (m, 1H), 7.51 (d,
J = 8.2 Hz, 1H), 7.92 (d, J = 8.4 Hz, 2H), 8.85 (s, 1H),
10.60 (s, 1H) ppm; 13C NMR (100 MHz, DMSO-d6):
d = 102.5, 107.1, 109.5, 116.7, 123.0, 124.6, 126.3, 133.1,
148.7, 150.3, 163.4, 165.3, 168.7, 174.1 ppm; HRMS (EI):
m/z calc’d for C16H11N3O3S (M ? H) 325.0521, found
325.0513.
1
White solid; m.p.: 192.3–194.2 °C; H NMR (400 MHz,
DMSO-d6): d = 3.82 (s, 6H), 6.64 (s, 1H), 6.98–7.05 (m,
3H), 7.37 (t, J = 7.0 Hz, 2H), 7.64 (d, J = 8.1 Hz, 2H)
ppm; 13C NMR (100 MHz, DMSO-d6): d = 56.0, 102.6,
105.2, 117.9, 122.6, 129.6, 132.5, 140.8, 157.9, 161.3,
164.5 ppm; HRMS (EI): m/z calc’d for C16H15N3O2S
(M ? H) 313.0885, found 313.0880.
General experimental procedure for the synthesis of 5-aryl-
N-phenyl-1,3,4-thiadiazol-2-amines 8
A mixture of aldehyde 5 (1 mmol), hydrazine hydrate 6
5-(4-Isopropylphenyl)-N-phenyl-1,3,4-thiadiazol-2-amine
(8k, C17H17N3S)
1
White solid; m.p.: 178.2–180.0 °C; H NMR (400 MHz,
(1 mmol), phenylisothiocyanate
7
(1 mmol), FeCl3
DMSO-d6): d = 1.23 (d, J = 6.8 Hz, 6H), 2.91–2.98 (m,
1H), 7.02 (t, J = 7.2 Hz, 1H), 7.37 (t, J = 8.6 Hz, 4H),
7.66 (d, J = 8.0 Hz, 2H), 7.77 (d, J = 8.0 Hz, 2H), 10.50
(br s, 1H) ppm; 13C NMR (100 MHz, DMSO-d6):
d = 24.1, 33.6, 117.9, 122.4, 127.3, 127.6, 128.5, 129.6,
140.8, 151.2, 158.1, 164.1 ppm; HRMS (EI): m/z calc’d for
C17H17N3S (M ? H) 295.1143, found 295.1140.
(2 mmol), and 6 cm3 water was subjected to microwave–
ultrasound activation conditions. The ultrasound and micro-
wave sources were switched on successively (power levels:
ultrasound 50 W, microwave 200 W). The mixture was
irradiated simultaneously by microwaves and ultrasound for
3 min. The suspension was filtered and the residue was
washed with water and ethanol, after which the residue was
recrystallized from ethanol and dried under vacuum to obtain
the products 8.
Acknowledgments Financial support for this work from the NSFC
(grant 20972052), the National Basic Research Program of China
(973 Program) (grant 2010CB126101), and the Shanghai Leading
Academic Discipline Project (project number: B507) is gratefully
acknowledged.
4-[5-(Phenylamino)-1,3,4-thiadiazol-2-yl]benzonitrile
(8b, C15H10N4S)
Light yellow solid; m.p.: 242.3– 243.5 °C; 1H NMR
(400 MHz, DMSO-d6): d = 7.06 (t, J = 7.2 Hz, 1H), 7.39
(t, J = 7.6 Hz, 2H), 7.67 (d, J = 7.9 Hz, 2H), 7.98 (d,
J = 8.7 Hz, 2H), 8.05 (d, J = 8.3 Hz, 2H), 10.71 (br s,
1H) ppm; 13C NMR (100 MHz, DMSO-d6): d = 112.6,
118.1, 122.8, 127.8, 129.6, 133.6, 140.6, 156.4, 165.5 ppm;
HRMS (EI): m/z calc’d for C15H10N4S (M ? H) 278.0626,
found 278.0623.
References
1. Anastas PT, Warner JC (1998) Green chemistry: theory and
practice. Oxford University Press, Oxford
2. Li CJ (2005) Chem Rev 105:3095
3. Li CJ (2008) Green Chem 10:151
4. Sheldon RA (2005) Green Chem 7:267
5. Dallinger D, Kappe CO (2007) Chem Rev 107:2563
6. Appukkuttan P, Mehta VP, Van der Eycken EV (2010) Chem Soc
Rev 39:1467
7. Kappe CO, Van der Eycken EV (2010) Chem Soc Rev 39:1280
8. Cravotto G, Cintas P (2006) Chem Soc Rev 35:180
9. Cravotto G, Cintas P (2007) Chem Eur J 13:1902
10. Mason TJ (1997) Chem Soc Rev 26:443
11. Martins MAP, Frizzo CP, Moreira DN, Zanatta N, Bonacorso HG
(2008) Chem Rev 108:2015
5-(3-Fluorophenyl)-N-phenyl-1,3,4-thiadiazol-2-amine
(8e, C14H10FN3S)
1
White solid; m.p.: 212.2–213.8 °C; H NMR (400 MHz,
DMSO-d6): d = 7.03 (t, J = 7.0 Hz, 1H), 7.34–7.37 (m,
4H), 7.65 (d, J = 8.1 Hz, 2H), 7.93 (t, J = 6.4 Hz, 2H),
10.54 (br s, 1H) ppm; 13C NMR (100 MHz, DMSO-d6):
d = 117.0, 117.9, 122.6, 127.4, 129.6, 140.8, 156.9, 162.2,
123

686
H. Feng et al.
12. Candeias NR, Branco LC, Gois PMP, Afonso CAM, Trindade AF
(2009) Chem Rev 109:2703
30. Kumar D, Vaddula BR, Chang KH, Shah K (2011) Bioorg Med
Chem Lett 21:2320
13. Martins MAP, Frizzo CP, Moreira DN, Buriol L, Machado P
(2009) Chem Rev 109:4140
14. Peng YQ, Dou RL, Song GH (2006) Green Chem 8:573
15. Molteni V, Hamilton MM, Mao L, Crane CM, Termin AP,
Wilson DM (2002) Synthesis 1669
16. Tu SJ, Zhang Y, Jiang H, Jiang B, Zhang JU, Zhang JY, Jia RH,
Shi F (2007) Eur J Org Chem 73:1522
17. Cho CS, Kim JS, Oh BH, Kim TJ, Shim SC, Yoon NS (2000)
Tetrahedron 56:7747
31. Kumar V, Singh P (2010) Asian J Chem 22:6829
32. Mishra RM, Singh DV, Wahab A, Mishra AR (2004) Pestic Res J
16:7
33. Giri S, Singh H (1966) J Indian Chem Soc 43:281
34. Peng YQ, Song GH (2002) Green Chem 4:349
35. Peng YQ, Song GH (2003) Green Chem 5:704
36. Feng HD, Li Y, Van der Eycken EV, Peng YQ, Song GH (2012)
Tetrahedron Lett 53:1160
37. Supuranl CT, Popescu A, Ilisiu M, Costandachez A, Banciuz MD
(1996) Eur J Med Chem 31:439
38. Chohan ZH, Pervez H, Rauf A, Andrea S, Supuran CT (2002) J
Enzym Inhib Med Chem 17:117
39. Bonizzoni M, Fabbrizzi L, Taglietti A (2006) Eur J Org Chem
3567
40. Rostamizadeh S, Aryan R, Ghaieni HR (2008) Heteroatom Chem
19:320
41. Shelke S, Mhaske G, Gadakh S, Gill C (2010) Bioorg Med Chem
Lett 20:7200
42. Hussein AQ, El-Abadelah MM, Nazer MZ, Awadallah AM,
Rademacher P, Bandmann H (1994) Heterocycles 38:981
43. Dutta MM, Goswami BN, Kataky JCS (1987) J Indian Chem Soc
64:195
18. Cao H, Wang X, Jiang H, Zhu Q, Zhang M, Liu H (2008) Chem
Eur J 14:11623
19. Totlani VM, Peterson DG (2005) J Agric Food Chem 53:4130
20. Bose DS, Fatima L, Mereyala HB (2003) J Org Chem 68:587
21. Rajak H, Agarawal A, Parmar P, Thakur BS, Veerasamy R,
Sharma PC, Kharya MD (2011) Bioorg Med Chem Lett 21:5735
22. Han F, Wan R, Wang Y, Wang P, Wang JT (2010) Youji Huaxue
30:132
23. Chai B, Cao S, Wu Q, Song GH, Qian XH (2003) Yingyong
Huaxue 20:811
24. Rollas S, Kandemirli K, Shvets N, Dimoglo AS (2004) J Med
Chem 47:6760
25. Carvalho SA, Silva EFD, Santa-Rita RM, Castrod SLD, Fraga
CAM (2004) Bioorg Med Chem Lett 14:5967
26. Jatav V, Mishra P, Kashaw S, Stables JP (2008) Eur J Med Chem
43:135
27. T Nalan, G Aysel (2004) J Med Chem 47:6760
28. Pattan SR, Kittur BS, Sastry BS, Jadav SG, Thakur DK, Mad-
amwar SA, Shinde HV (2011) Indian J Chem Section B 50B:615
29. Bernstein J, Yale HL, Losee K, Holsing M, Martins J, Lott WA
(1951) J Am Chem Soc 73:906
44. Efimova YA, Karabanovich GG, Artamonova TV, Koldobskii GI
(2009) Russ J Org Chem 45:631
45. Liu ZX, Song ZS, Zhao JL, Zheng JY (2010) Phosphorus Sulfur
Silicon Relat Elem 185:2375
46. Sharabasappa S, Bhat KI, Jalihal PC, Kilarimath B (2009) J
Chem Pharm Sci 2:141
123