A practical and green protocol for the synthesis of 2,3-dihydroquinazolin-4(1H)-ones using oxalic acid as organocatalyst

Article abstract of DOI:10.1007/s11164-016-2855-6

Abstract: An expeditious synthesis of 2,3-dihydroquinazolin-4(1H)-ones in the presence of oxalic acid as an environmentally friendly organocatalyst is reported. The salient features of the protocol are high yields, green reaction profile, shorter reaction times, and simple experimental and work-up procedure. Graphical Abstract: [Figure not available: see fulltext.].

Full text of DOI:10.1007/s11164-016-2855-6

Res Chem Intermed
DOI 10.1007/s11164-016-2855-6
A practical and green protocol for the synthesis of
2,3-dihydroquinazolin-4(1H)-ones using oxalic acid
as organocatalyst
Shrikrishna Karhale1 Dattatray Survase1
•
•
Rahul Bhat1 Panchsheela Ubale1 Vasant Helavi1
•
•
Received: 25 October 2016 / Accepted: 27 December 2016
Ó Springer Science+Business Media Dordrecht 2017
Abstract An expeditious synthesis of 2,3-dihydroquinazolin-4(1H)-ones in the pres-
ence of oxalic acid as an environmentally friendly organocatalyst is reported. The salient
features of the protocol are high yields, green reaction profile, shorter reaction times, and
simple experimental and work-up procedure.
Graphical Abstract
O
O
NH
NH
N
H
N
H
R
R
Oxalic Acid
(20 mol%)
NH4OAc
Water:Ethanol
O
O
CHO
80oC
CHO
O
NH
2
+
+
N
H
O
NH
2
R
R
Keywords Multi-component reactions Á Oxalic acid Á 2,3-Dihydroquinazolin-
4(1H)-ones Á Green protocol
&
Vasant Helavi
vbhelavi@gmail.com
1
Department of Chemistry, Rajaram College, Kolhapur 416004, Maharashtra, India
123

S. Karhale et al.
Introduction
The recent quest towards the implementation of green methodologies in synthetic
chemistry has spurred an extensive interest in the multicomponent reactions
(MCRs) for the generation of highly privileged scaffolds of molecular complexity
[1]. Such methodologies are able to manage dual goals such as environmental
protection, as well as economic benefit. The systematic improvements in such
methodologies are challenging benchmarks to organic chemist, and hence desperate
attempts have been made for the development of these methodologies [2, 3]. The
MCRs show remarkable significance in construction of diverse and complex organic
molecules in a single step, which includes all essential parts of the starting
materials. Furthermore, MCRs also have additional merits such as its exceptional
synthetic efficiency, high atom economy, decrease in waste generation and
formation of essential carbon–carbon and carbon-heteroatom bonds [4–8]. MCRs
using environmentally benign catalyst under mild reaction conditions in eco-
friendly solvent have become fundamental strategy in green synthetic methodolo-
gies [9, 10].
Recently, a great deal of attention has been focused on the use of organocatalysts
in synthetic chemistry [11–13]. Organocatalyzed reaction offers handy technique for
the synthesis of fundamental moieties having potential applications in the diverse
fields [14]. Organocatalysts are cost-effective, stable, non-toxic, easy to handle,
metal-free, and are often used in stoichiometric amounts [15]. The most exciting
features of organocatalysts include minimization of waste and environmentally safe
disposal [16, 17]. Oxalic acid is a strong acid since it has two carboxylic groups
joined directly to each other and thus is widely used as an efficient organocatalyst in
organic transformation [18–23]. Furthermore, oxalic acid is also used for the
preparation of low transition temperature mixtures (LTTMs) liquids [24, 25]. The
remarkable catalytic efficacy and hydrophilic nature of oxalic acid prompted us to
explore its catalytic utility in the MCRs leading to synthesis of biologically active
heterocyclic scaffolds.
Quinazolinones are prominent class of aza-heterocyclic compounds which acts as
a core unit in the number of marketed drug products (Fig. 1). Quinazolinone
derivatives such as 2,3-dihydroquinazolin-4(1H)-ones are privileged structural
motifs having variety of applications in the biological, pharmacological and
Fig. 1 Examples of some important marketed drugs having quinazolinones framework. (Color
figure online)
123

A practical and green protocol for the synthesis of…
medicinal fields [26–32]. Owing to unique applicative profile, a number of protocols
have been developed for the synthesis of 2,3-dihydroquinazolin-4(1H)-ones. The
most common route for the synthesis of 2,3-dihydroquinazolin-4(1H)-ones includes
MCR of isatoic anhydride, ammonium acetate with aryl aldehydes. Variety of
catalysts have been reported for the synthesis of 2,3-dihydroquinazolin-4(1H)-ones
using this route [33–50]. However, some of these methods suffer from drawbacks
such as use of a metal-based catalyst, high reaction temperature, tedious catalyst
preparation, high expense, and toxic nature of catalyst. Therefore, the development
of a green and cost-effective method for synthesis is highly desirable.
As part of our research work in the development of sustainable methodologies for
the preparation of bioactive heterocycles [51, 52], herein we report green protocol
for synthesis of 2,3-dihydroquinazolin-4(1H)-ones by means of one-pot, three-
component reaction of isatoic anhydride, NH4OAc with various aromatic aldehydes
in the presence of oxalic acid as a catalyst.
Experimental
All chemicals were purchase from local supplier and used as received. Melting
points were determined by the open capillary method. The IR spectra were
measured on Bruker ALPHA FT-IR spectrometer in between the frequency range
1
500–4000 cm-1. The NMR spectra were recorded on Bruker AC (300 MHz for H
NMR and 75 MHz for 13C NMR) spectrometer using TMS as an internal standard in
DMSO-d6. Chemical shifts (d) are expressed in ppm.
Representative procedure for synthesis of 2,3-dihydroquinazolin-4(1H)-ones
Synthesis of 2,3-dihydroquinazolin-4(1H)-ones by using three-component reaction
of isatoic anhydride, NH4OAc and aryl aldehydes (method A)
In a 25-mL RB flask, a mixture of isatoic anhydride (1 mmol), aryl aldehyde
(1 mmol), ammonium acetate (1.2 mmol), and oxalic acid (20 mol%) in
ethanol:water (1:1, 4 mL) was stirred at 80 °C. Upon the completion of reaction
as indicated by TLC, the reaction mixture was allowed to cool at room temperature,
and water (5 mL) was added and stirred continuously until a solid was obtained in
the reaction flask. The resultant solid was filtered, washed with water, and then
dried. The solid was recrystallized by petroleum ether:ethyl acetate (70:30, v/v). All
the resulting products were pure and characterized by spectroscopic techniques.
Synthesis of 2,3-dihydroquinazolin-4(1H)-ones by using anthranilamide and aryl
aldehydes (method B)
In a 25-mL RB flask, a mixture of anthranilamide (1 mmol), aryl aldehyde
(1 mmol), and oxalic acid (20 mol%) in ethanol:water (1:1, 4 mL) was stirred at
80 °C. Upon the completion of reaction as indicated by TLC, the reaction mixture
was allowed to cool at room temperature, and water (5 mL) was added and stirred
123

S. Karhale et al.
continuously until a solid was obtained in the reaction flask. The resultant solid was
filtered, washed with water, and then dried. The solid was recrystallized by
petroleum ether:ethyl acetate (70:30, v/v). All the resulting products were pure and
characterized by spectroscopic techniques.
Selected spectral data of representative compounds
2-Phenyl-2,3-dihydroquinazolin-4(1H)-one (Table 3, entry 1) Mp: 225–227 °C,
1H NMR (300 MHz, DMSO d6): d (ppm) d 8.19 (bs, 1H, NH), 7.61–7.64 (d, 1H,
J = 6.9 Hz, Ar–H), 7.34–7.49 (m, 5H, Ar–H), 7.20 (s, 1H, Ar–H), 7.01 (bs, 1H,
NH), 6.65–6.75 (t, 2H, J = 6.9 Hz, Ar–H), 5.75 (s, 1H, CH); 13C NMR (75 MHz,
DMSO d6): d 67.1, 114.8, 115.3, 117.5, 127.2, 127.7, 128.6, 128.8, 133.6, 141.9,
148.2, 164.1; IR (KBr) (cm-1): 3305, 3180, 3059, 3031, 1652, 1609 cm-1
.
2-(p-Tolyl)-2,3-dihydroquinazolin-4(1H)-one (Table 3, entry 9) Mp: 220–222 °C,
1H NMR (300 MHz, DMSO d6): d (ppm) d 8.00 (s, 1H, NH), 7.61–7.64 (d, 1H,
J = 7.8 Hz, Ar–H), 7.36–7.38 (d, 2H, J = 7.5 Hz, Ar–H), 7.13–7.20 (m, 3H, Ar–
H), 6.61–6.83 (m, 3H, NH, Ar–H), 5.70 (s, 1H, CH), 2.29 (s, 3H, CH3); 13C NMR
(75 MHz, DMSO d6): d 21.2, 67.2, 114.7, 115.2, 117.5, 127.2, 127.7, 133.5, 138.2,
138.6, 148.3, 164.4; IR (KBr) (cm-1): 3308, 3180, 3058, 3030, 2943, 1651,
1606 cm-1
.
2-(1H-Indol-3-yl)-2,3-dihydroquinazolin-4(1H)-one (Table 3, entry 11) Mp:
1
218–220 °C, H NMR (300 MHz, DMSO d6): d (ppm) 10.87 (s, 1H, Indole-H1),
10.37 (s, 1H, NH), 7.36–7.52 (m, 1H, Ar–H), 7.03–7.22 (m, 4H, Indole-H4, H5, H6,
H7), 6.88–6.96 (m, 1H, Ar–H), 6.85 (s, 1H, Indole-H2), 6.63–6.69 (m, 2H, Ar–H),
6.56 (s, 1H, NH), 5.81 (s, 1H, CH); 13C NMR (75 MHz, DMSO d6): d 55.5, 110.8,
112.1, 114.1, 121.6, 122.7, 124.9, 125.4, 126.0, 130.4, 132.3, 134.9, 141.6, 152.9,
163.9; IR (KBr) (cm-1): 3283, 3172, 3055, 2923, 1657, 1615 cm-1
.
2-(Pyridine-2-yl)-2,3-dihydroquinazolin-4(1H)-one (Table 3, entry 12) Mp:
1
186–188 °C, H NMR (300 MHz, DMSO d6:CDCl3): d (ppm) 8.51–8.53 (d, 1H,
J = 3.9 Hz, Pyridine-H3), 8.27 (s, 1H, NH), 7.50–7.77 (m, 3H, Pyridine-H4, H5,
H6), 7.15–7.29 (m, 3H, NH, Ar–H), 6.63–6.76 (m, 2H, Ar–H), 5.73 (s, 1H, CH); 13
C
NMR (75 MHz, DMSO d6:CDCl3): d 67.6, 114.9, 115.2, 117.6, 120.8, 123.6, 127.7,
133.6, 137.2, 147.7, 149.2, 160.3, 164.1; IR (KBr) (cm-1): 3328, 3182, 3051, 2928,
1665, 1650 cm-1
.
2-(Ferrocenyl)-2,3-dihydroquinazolin-4(1H)-one (Table 3, entry 13) Mp:
241–242 °C, 1H NMR (300 MHz, DMSO d6): d (ppm) 11.9 (s, 1H, NH),
8.07–8.09 (d, 1H, J = 7.5 Hz, Ar–H), 7.92 (s, 1H, NH), 7.55–7.70 (m, 1H, Ar–H),
7.15–7.41 (doublet of triplet, 1H, Ar–H), 6.62–6.74 (m, 1H, Ar–H), 5.54 (s, 1H,
CH), 5.24 (s, 1H, Cp), 4.48 (s, 1H, Cp), 4.15–4.18 (m, 5H, Cp), 4.07 (s, 2H, Cp); 13
C
NMR (75 MHz, DMSO d6): d 63.5, 66.4, 67.9, 68.6, 70.0, 76.5, 90.5, 114.8, 117.3,
121.0, 125.7, 126.2, 127.6, 133.5, 134.6, 149.6, 155.9, 162.5; IR (KBr) (cm-1):
3428, 3158, 3075, 3023, 1641, 1006 cm-1
.
123

A practical and green protocol for the synthesis of…
Results and discussion
To establish the most appropriate reaction conditions, initially the template reaction
between isatoic anhydride (1 mmol), benzaldehyde (1 mmol), and NH4OAc
(1.2 mmol) in the presence of oxalic acid (20 mol%) was carried out in various
solvents at 80 °C. The reaction proceeded scarcely in toluene, DMF, THF, EDC,
water, and ethanol providing the desired 2-phenyl-2,3-dihydroquinazolin-4(1H)-one
in lower yields (Table 1, entries 1–6). Surprisingly, it was observed that reaction
marches efficiently in mixed solvent system of ethanol:water (1:1, v:v) furnishing
the anticipated product in excellent yield (Table 1, entry 7).
Our next task was to optimize the catalyst loading. For this, we have carried out
the template reaction using different amounts of catalyst and the results are
summarized in Table 2. It was found that the quantity of catalyst had a significant
impact on the yield of reaction. When the quantity of oxalic acid was increased from
5 to 15 mol%, the yield of anticipated product was elevated significantly from 45 to
80% (Table 2, entries 1–3). To our delight, the excellent yield was achieved for
20 mol% of oxalic acid (Table 2, entry 4). Further increase in catalyst quantity did
not have a deep influence on yield of the desired product (Table 2, entries 5).
After the optimization of reaction conditions, we evaluated the scope and
generality of protocol by reacting isatoic anhydride, NH4OAc with various aromatic
aldehydes. The results are shown in Table 3. The reaction proceeded smoothly in all
the cases forming the corresponding 2,3-dihydroquinazolin-4(1H)-ones in good to
excellent yields (72–92%). It is worthy to note that aryl aldehyde with electron
donating, as well as electron withdrawing substituents reacted efficiently with equal
chemical reactivity (Table 3, entries 2–10). Interestingly, hetero-aromatic aldehydes
Table 1 Optimization of solvent in the synthesis of 2-phenyl-2,3-dihydroquinazolin-4(1H)-one
O
O
CHO
NH
Oxalic Acid, (20 mol%)
Solvent
O
NH4OAc
+
+
N
H
N
H
O
Entries
Reaction condition
Time (min)
Isolated yields (%)
1
2
3
4
5
6
7
Toluene/80 °C
DMF/80 °C
THF/80 °C
EDC/80 °C
Water/80 °C
Ethanol/80 °C
40
40
40
40
40
40
40
22
27
30
32
65
75
90
Ethanol:Water (1:1)/80 °C
Reaction conditions: isatoic anhydride (1 mmol), NH4OAc (1.2 mmol), benzaldehyde (1 mmol), and
oxalic acid (20 mol%) at the given conditions
123

S. Karhale et al.
Table 2 Optimization of catalyst loading
O
O
CHO
Oxalic Acid
NH
O
NH4OAc
+
+
Ethanol:Water (1:1)
N
H
N
H
O
Entry
Catalyst (mol%)
Reaction time (min)
Isolated yields (%)
1
2
3
4
5
05
10
15
20
30
40
40
40
40
40
45
75
80
90
90
Reaction conditions: isatoic anhydride (1 mmol), NH4OAc (1.2 mmol), benzaldehyde (1 mmol), and
oxalic acid at the given conditions
Table 3 Oxalic acid catalyzed synthesis of 2,3-dihydroquinazolin-4(1H)-ones
O
O
CHO
NH
O
Oxalic acid (20 mol%)
NH OAc
4
+
+
N
H
Ethanol:Water (1:1), 80oC
N
H
O
R
3
1
2
4a-m
R
Entries Aryl aldehyde (2)
Product Time (min) Yielda (%) Mp (°C) [Ref.]
1
2
Benzaldehyde
4a
4b
4c
4d
4e
4f
40
35
38
45
44
40
50
48
45
55
90
92
90
88
87
92
86
90
87
84
225–227 [224–226] [40]
197–199 [198–200] [40]
191–193 [190–192] [40]
209–211 [210–211] [40]
203–204 [202–204] [41]
\300 [350–351] [42]
4-Nitrobenzaldehyde
3-Nitrobenzaldehyde
4-Chlorobenzaldehyde
4-Bromobenzaldehyde
4-Cyanobenzaldehyde
3
4
5
6
7
4-Hydroxybenzaldehyde
4-Methoxybenzaldehyde
4-Methylbenzaldehyde
4g
4h
4i
278–279 [277–279] [43]
182–183 [182–184] [40]
220–222 [221–222] [40]
186–188 [185–187] [41]
8
9
10
3,4,5-
4j
Trimethoxybenzaldehyde
11
12
13
Indole-3-carboxaldehyde
Pyridine-2-carboxaldehyde
Ferrocenecarboxaldehyde
4k
4l
65
60
70
81
72
75
218–220 [219–220] [42]
186–188 [187–188] [43]
241–242
4m
Reaction conditions: isatoic anhydride (1 mmol), NH4OAc (1.2 mmol), aryl aldehyde (1 mmol), and
oxalic acid (20 mol%) at the given conditions
a
Isolated yields
123

A practical and green protocol for the synthesis of…
O
O
CHO
NH
Oxalic Acid, (20 mol%)
NH2
+
N
H
Ethanol:Water (1:1), 80oC
NH2
R
5
2
6a-f
R
Scheme 1 Oxalic acid catalyzed reaction between anthranilamide and aromatic aldehydes
Table 4 Oxalic acid catalyzed reaction between anthranilamide and aromatic aldehydes
Entries
Aryl aldehyde (2)
Product
Time (min)
Isolated Yield (%)
1
2
3
4
5
6
Benzaldehyde
6a
6b
6c
6d
6e
6f
45
44
40
48
45
40
88
90
87
86
85
88
4-Nitrobenzaldehyde
3-Nitrobenzaldehyde
4-Chlorobenzaldehyde
4-Bromobenzaldehyde
4-Cyanobenzaldehyde
Reaction conditions: anthranilamide (1 mmol), aryl aldehyde (1 mmol), and oxalic acid (20 mol%) at
the given conditions
such as indole-3-carboxaldehyde (Table 3, entry 11) and sterically congested
pyridine-2-carboxaldehyde (Table 3, entry 12) were also well-tolerated providing
the desired products in moderate yields (81–72%). To our delight, ferrocenecar-
boxaldehyde (Table 3, entry 13) could also serve as a substrate providing moderate
yield (75%) of the expected product.
To broaden further the scope of the protocol, oxalic acid was scrutinized for
analogous synthesis of 2,3-dihydroquinazolin-4(1H)-ones using reaction of
anthranilamide and aryl aldehydes under the optimized reaction conditions
(Scheme 1). It was observed that oxalic acid efficiently catalyzes the reaction
between anthranilamide and aryl aldehydes providing the corresponding products in
good to excellent yield (Table 4).
The plausible mechanism for the synthesis of 2,3-dihydroquinazolin-4(1H)-ones
using both methods (method A & B) is shown in Scheme 2. In method A, initial
protonation of the carbonyl group of isatoic anhydride (I) by oxalic acid, followed
by the attack of NH4OAc results in the subsequent ring opening, and decarboxy-
lation provides anthranilamide intermediate (II). Further, activated aldehyde reacts
with (II) followed by removal of water to give imine intermediate (III). The
intramolecular nucleophilic attack of carboximidate nitrogen on imine carbon
followed by cyclization furnishes the anticipated 2,3-dihydroquinazolin-4(1H)-ones
(IV). Thus, we conclude that reaction proceeds through the formation of
anthranilamide intermediate [45]. In method B, oxalic acid activates the carbonyl
group of aromatic aldehyde, which then reacts with anthranilamide following the
similar pathway as depicted for method A.
123

S. Karhale et al.
Method A:
H
O+
O
O
H
O+
Oxalic acid
H+
NH4OAc
O
O
NH2
Ring Opening
-CO2
H
N
H
O
N
H
O
NH2
..
(II)
(I)
H+
O
O
O
O
-H+
-H2O
NH2
OH
NH
NH2
NH
N
H
N+
H2
NH+2
NH+
(IV)
(III)
Method B:
O
H
O+
O
O
NH2
..
Intramolecular
Cyclization
NH2
H
NH
..
NH2
NH+
-H+
N
H
Scheme 2 Mechanistic pathway for the synthesis of 2,3-dihydroquinazolin-4(1H)-ones
Table 5 Reusability of catalyst
for synthesis of 4a
Sr. no.
Cycles
Yield (%)
Catalyst recovered (%)
1
2
3
4
Fresh
90
88
85
82
94
91
88
86
1
2
3
Table 6 Comparison of oxalic acid with reported catalyst for synthesis of 2,3-dihydroquinazolin-4(1H)-
onesa
Sr. no. Catalyst used
Catalyst (mol%) Temp (°C) Time
Isolated yield (%) References
1
2
3
4
5
6
a
Oxalic acid
DBSA
20
20
3
80
42
40 min 90
3 h 68
45 min 95
2 h 88
This work
[34]
Ce(SO4)2Á4H2O
Al(MS)3Á4H2O
Molecular iodine 20
120
80
[36]
5
[40]
115
70
20 min 97
50 min 89
[44]
TBAB
10
[45]
The results belongs to method A
The reusability of oxalic acid was tested for the template reaction. After the
separation of product, the resulting filtrate was extracted with chloroform, the
aqueous layer containing oxalic acid was separated, and water was evaporated in
123

A practical and green protocol for the synthesis of…
vacuo to get crude oxalic acid. The recovered oxalic acid was reused three times
without significant decrease in the yield of desired product. The slight decrease in
the observed yield (Table 5) is attributed to inadequate recovery of the catalyst due
to the attrition during filtration.
In order to show the advantages of oxalic acid in comparison with other catalysts,
we have summarized several results for the preparation of 2,3-dihydroquinazolin-
4(1H)-ones (Table 6). The comparison of results reveals that oxalic acid is a highly
effective catalyst in terms of reaction time and yield than other reported catalysts.
Conclusion
We have described a one-pot, simple and efficient method for the multi-component
synthesis of 2,3-dihydroquinazolin-4(1H)-ones using isatoic anhydride, NH4OAc
with diverse aryl aldehydes using a catalytic amount of oxalic acid at 80 °C. The
present environmentally benign methodology follows the tenets of green chemistry
for synthesis of important scaffolds by using an easily available, inexpensive, water
soluble, and non-toxic organocatalyst. The method offers several advantages such as
high yields, cleaner reaction profiles, minimum waste generation, less environmen-
tal pollution, operational simplicity, shorter reaction times, and simple experimental
and work-up procedure.
Acknowledgements One of the author (SSK) thankful to UGC, New Delhi, for Teacher Fellowship [F.
No. 30-35/14 (WRO) dated: 11th June 2014] under the Faculty Development Programme. Author is also
thankful to Principal, Abasaheb Marathe Arts & New Commerce, Science College, Rajapur, Ratnagiri,
for encouragement and Head, Department of Chemistry, Rajaram College, Kolhapur for providing
necessary facilities.
References
1. H. Koga, T. Kitaoka, A. Isogai, Molecules 20, 1495 (2015)
2. R.A. Sheldon, I. Arends, U. Hanefeld, Green Chemistry and Catalysis (Wiely-VCH, Weinheim,
2007)
3. P. Anastas, N. Eghbali, Chem. Soc. Rev. 39, 301 (2010)
4. M.S. Singh, S. Chowdhury, RSC Adv. 2, 4547 (2012)
5. D.J. Ramon, M. Yus, Angew. Chem. Int. Ed. 44, 1602 (2005)
6. A. Domling, Chem. Rev. 106, 17 (2006)
7. R.K. Singh, R. Bala, R. Duvedi, S. Kumar, Iran. J. Catal. 5, 187 (2015)
8. A. Domling, I. Ugi, Angew. Chem. Int. Ed. 39, 3168 (2000)
9. A.J. Wangelin, H. Neumann, D. Gordes, S. Klaus, D. Strubing, M. Beller, Chem. Eur. J. 9, 4286
(2003)
10. M.B. Gawande, V.D.B. Bonifacio, R. Luque, P.S. Branco, R.S. Varma, Chem. Soc. Rev. 42, 5522
(2013)
11. K. Aghapoor, F. Mohsenzadeh, H.R. Darabi, H. Sayahi, Y. Balavar, Res. Chem. Intermed. 42, 407
(2016)
12. X. Liu, Y. Wang, D. Yang, J. Zhang, D. Liu, W. Su, Angew. Chem. Int. Ed. 55, 8100 (2016)
13. J. Zhang, X. Liu, X. Maa, R. Wang, Chem. Commun. 49, 9329 (2013)
14. S. Nazari, M. Keshavarz, B. Karami, N. Iravani, M. Vafaee-Nezhad, Chin. Chem. Lett. 25, 317
(2014)
15. S. Khaksar, S.M. Vahdat, R.N. Moghaddamnejad, Monatsh. Chem. 143, 1671 (2012)
123

S. Karhale et al.
16. A.R. Khorrami, P. Kiani, A. Bazgir, Monatsh. Chem. 142, 287 (2011)
17. X.Z. Lian, Y. Huang, Y.Q. Li, W.J. Zheng, Monatsh. Chem. 139, 129 (2008)
18. S. Chandrasekhar, K. Gopalaiah, Tetrahedron Lett. 44, 7437 (2003)
19. N.D. Kokare, J.N. Sangshetti, D.B. Shinde, Chin. Chem. Lett. 19, 1186 (2008)
20. J.N. Sangshetti, N.D. Kokare, D.B. Shinde, J. Heterocycl. Chem. 45, 1191 (2008)
21. N.D. Kokare, J.N. Sangshetti, D.B. Shinde, Chin. Chem. Lett. 18, 1309 (2007)
22. N.D. Kokare, J.N. Sangshetti, D.B. Shinde, Synthesis 18, 2829 (2007)
23. J.N. Sangshetti, N.D. Kokare, D.B. Shinde, Chin. J. Chem. 26, 1506 (2008)
24. D.R. Chandam, A.G. Mulik, D.R. Patil, A.P. Patravale, D.R. Kumbhar, M.B. Deshmukh, J. Mol. Liq.
219, 573 (2016)
25. D.R. Chandam, A.G. Mulik, D.R. Patil, M.B. Deshmukh, Res. Chem. Intermed. 42, 1411 (2016)
26. V.K. Pandey, S. Tusi, Z. Tusi, R. Raghubir, M. Dixit, M.N. Joshi, Indian J. Chem. B. 43, 180 (2004)
27. M.J. Hour, L.J. Huang, S.C. Kuo, Y. Xia, K. Bastow, Y. Nakanishi, E. Hamel, K.H. Lee, J. Med.
Chem. 43, 4479 (2000)
28. R.J. Alaimo, H.E. Russel, J. Med. Chem. 15, 335 (1972)
29. D.A. Erlanson, R.S. McDowell, T. O’Brien, J. Med. Chem. 47, 3463 (2004)
30. E. Hamel, C.M. Lin, J. Plowman, H.K. Wang, K.H. Lee, K.D. Paull, Biochem. Pharmacol. 51, 53
(1996)
31. K. Ozaki, Y. Yamada, T. Oine, T. Ishizuka, Y. Iwasawa, J. Med. Chem. 28, 568 (1985)
32. E. Jafari, M.R. Khajouei, F. Hassanzadeh, G.H. Hakimelahi, G.A. Khodarahmi, Res. Pharm. Sci. 11,
1 (2016)
33. A. Magyar, Z. Hell, Catal. Lett. 146, 1153 (2016)
34. B.H. Chen, J.T. Li, G.F. Chen, Ultrason. Sonochem. 23, 59 (2015)
35. J. Safari, S. Gandomi-Ravandi, J. Mol. Struct. 1072, 173 (2014)
36. A. Davoodnia, M. Khashi, N. Tavakoli-Hoseini, Chinese J. Catal. 35, 1054 (2014)
37. H.R. Shaterian, F. Rigi, Res. Chem. Intermed. 40, 2983 (2014)
38. J. Safari, S. Gandomi-Ravandi, J. Mol. Catal. A: Chem. 371, 135 (2013)
39. P. Yerram, R. Chowrasia, S. Seeka, S.J. Tangenda, Eur. J. Chem. 4, 462 (2013)
40. Z. Song, L. Liu, Y. Wang, X. Sun, Res. Chem. Intermed. 38, 1091 (2012)
41. S. Zhaleh, N. Hazeri, M.T. Maghsoodlou, Res. Chem. Intermed. 42, 6381 (2016)
42. J. Chen, D. Wu, F. He, M. Liu, H. Wu, J. Ding, W. Su, Tetrahedron Lett. 49, 3814 (2008)
43. S. Rostamizadeh, A.M. Amani, G.H. Mahdavinia, H. Sepehrian, S. Ebrahimi, Synthesis 8, 1356
(2010)
44. S. Rostamizadeh, A.M. Amani, R. Aryan, H.R. Ghaieni, N. Shadjou, Synth. Commun. 38, 3567
(2008)
45. M.A.B. Fard, A. Mobinikhaledi, M. Hamidinasab, Synth. React. Inorg. Metal Org. Nano Met. Chem.
44, 567 (2014)
46. Z. Karimi-Jaberi, R. Arjmandi, Monatsh. Chem. 142, 631 (2011)
47. K. Niknam, M.R. Mohammadizadeh, S. Mirzaee, Chin. J. Chem. 29, 1417 (2011)
48. M. Dabiri, P. Salehi, M. Bahramnejad, M. Alizadeh, Monatsh. Chem. 141, 877 (2010)
49. S. Li, Q. Zhang, Y. Peng, Monatsh. Chem. 146, 1859 (2015)
50. M.T. Maghsoodlou, N. Khorshidi, M.R. Mousavi, N. Hazeri, S.M. Habibi-Khorassani, Res. Chem.
Intermed. 41, 7497 (2015)
51. S. Karhale, K. Patil, C. Bhenki, G. Rashinkar, V. Helavi, Res. Chem. Intermed. 42, 7257 (2016)
52. D.N. Survase, H.V. Chavan, S.B. Dongare, V.B. Helavi, Synth. Commun. 46, 1665 (2016)
123