Elementary and efficient catalyst process for the Knoevenagel condensation of araldehydes with arylmethylidene malononitrile

Article abstract of DOI:10.1016/j.ica.2017.10.028

A comparative study of the Knoevenagel condensation of an aromatic aldehyde with an active methylene compound (e.g., malononitrile or ethyl cyanoacetate), using solvent free grindstone conditions and microwave irradiation is reported. Our solvent free app

Full text of DOI:10.1016/j.ica.2017.10.028

Accepted Manuscript
Research paper
Elementary and efficient Catalyst process for the Knoevenagel Condensation of
araldehydes with arylmethylidene malononitrile
Raja Jlassi, Ana P.C. Ribeiro, Gonçalo A.O. Tiago, Jiawei Wang, Marta S.
Krawczyk, L.M.D.R.S. Martins, Houcine Naïli, Armando J.L. Pombeiro, Walid
Rekik
PII:
S0020-1693(17)31175-1
https://doi.org/10.1016/j.ica.2017.10.028
ICA 17955
DOI:
Reference:
Inorganica Chimica Acta
To appear in:
Received Date:
Revised Date:
Accepted Date:
27 July 2017
16 October 2017
24 October 2017
Please cite this article as: R. Jlassi, A.P.C. Ribeiro, G.A.O. Tiago, J. Wang, M.S. Krawczyk, L.M.D.R.S. Martins,
H. Naïli, A.J.L. Pombeiro, W. Rekik, Elementary and efficient Catalyst process for the Knoevenagel Condensation
of araldehydes with arylmethylidene malononitrile, Inorganica Chimica Acta (2017), doi: https://doi.org/10.1016/
j.ica.2017.10.028
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Inorganica chimica acta
Elementary and efficient Catalyst process for the Knoevenagel
Condensation of araldehydes with arylmethylidene malononitrile
Raja Jlassi[a,b], Ana P. C. Ribeiro[a], Gonçalo A.O. Tiago[a], Jiawei Wang[a], Marta S.
Krawczyk [c], L.M.D.R.S. Martins[a, d], Houcine Naïli [b]*, Armando J. L. Pombeiro[a] and
Walid Rekik [b] *
a
Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa,
Av. Rovisco Pais, 1049–001 Lisbon, Portugal
b
Laboratoire de physico-chimie de l’Etat Solide, Département de Chimie, Faculté des
Sciences de Sfax, Université de Sfax, BP 1171, 3000 Sfax, Tunisie
c
Department of Analytical Chemistry, Faculty of Pharmacy, Wroclaw Medical University,
Borowska 211A, 50-556 Wroclaw, Poland
d
Chemical Engineering Department, Instituto Superior de Engenharia de Lisboa, Instituto
Politécnico de Lisboa, Rua Conselheiro Emídio Navarro, 1959-007 Lisboa, Portugal.
∗
Corresponding author:
E-mail address: walidrekik@lycos.com
(Walid Rekik) ;
houcine_naili@yahoo.com (Houcine Naili);
Tel: +216 97 34 11 85; fax: +216 74 274 437

Graphical abstract
Synopsis
The preparation of a new complex has been accomplished. The single-XRD shows that it
adopts a polymeric structure. The title compound is found to be a good catalyst for the
Knoevenagel condensation reaction.
Highlights:
•
•
•
A new Cd(II) complex derived from arylhydrazone has been elaborated.
The single X-ray diffraction showed polymer crystal structure.
The Cd(II) complex was found to be a good catalyst for the Knoevenagel condensation
reaction.

Abstract
A comparative study of the Knoevenagel condensation of an aromatic aldehyde with an active
methylene compound (e.g., malononitrile or ethyl cyanoacetate), using solvent free grindstone
conditions and microwave irradiation is reported. Our solvent free approaches led these
reactions to proceed faster, more cleanly and in higher yields. Moreover, they also allowed the
use of nitrobenzaldehydes, which failed to yield the desired products under traditional and
water based approaches. Thus, an efficient procedure for the Knoevenagel condensation of
aryl and heteroaromatic aldehydes with malononitrile.
using the complex
.
[CdNa2(µ-L2)]n 6.34H2O or commercial CdO as catalyst under solvent-free and very mild
conditions has been developed.
Key words: Knoevenagel condensation, grindstone technique, microwave, malononitrile;
solvent-free reaction.
Introduction
The Knoevenagel condensation is one of known C-C coupling reactions in Chemistry. In the
last couple of years its application ranged from pharmaceutical industry [1], to polymers [1]
and even the application of alternative solvents, such as ionic liquids [2], have been reported.
However, most of these methods have drawbacks like harsh reaction conditions, low yield,
long reaction time and the use of organic solvents which causes environmental waste and
pollution. Thus, the development of an alternative method, more particularly with the
application of novel, simple, efficient, cost-effective, high-yielding, and green methodologies
is highly desirable.
Grinding solvent-free reactions, as well as microwave-assisted reactions, offer the above
advantages, and the reactions are complete within minutes [1]. Moreover, the work-up is very
simple and does not require complicated purification procedure or the use of volatile organic

solvents [3-6]. This useful novel reaction tool relies on the power of the microwaves to reduce
the times of reaction and the energy consumption increasing the yields and selectivities of the
investigated reactions in many cases [7, 8].
Experimental
Equipment and materials
Grinding solvent-free reactions were performed in open vessels at room temperature using a
pestle and a mortar. Also, these reactions were without any mechanical stirring.
Furthermore, the reactions were monitored by thin layer chromatography (TLC) and all the
products were characterized by comparison with authentic samples on TLC.
The solvent-free microwave assisted reactions were performed in a focused Anton Paar
Monowave 300 reactor, using a 10-mL capacity reaction tube with a 13-mm internal diameter
and equipped with a rotational system and an IR temperature detector.1H (300 MHz) NMR
spectra were obtained at room temperature (RT) on a Bruker Advance II + 300
(UltraShieldTMMagnet) spectrometer using tetramethylsilane [Si(CH3)4] as an internal
reference.
.
Preparation of [CdNa2(µ-L2)]n 6.34H2O
Synthesis of Na2HL1
Na2HL1 is synthesized by aqueous diazotization of 2-aminoterephthalic acid (99%, Aldrich)
with subsequent coupling with 5,5-dimethylcyclohexane-1,3-dione (95%, Aldrich),
respectively [9].
Diazotization: A 20 mmol portion of 2-aminoterephthalic acid was dissolved in 50 mL of
water upon addition of 1.6 g (40 mmol) of crystalline NaOH (97%, Aldrich). The solution
was cooled in an ice bath to 0 °C and 20 mmol of NaNO2 (98%, Aldrich), were added with

subsequent addition of 4 mL HCl (33%, Aldrich), in portions of 0.4 mL for 1 h, under
vigorous stirring. During the reaction, the temperature of the mixture must not exceed +5°C.
The obtained diazonium salt was used for the next stage.
Azocoupling: 20 mmol of NaOH were added to a mixture of 20 mmol of 5,5-
dimethylcyclohexane-1,3-dione in 50 mL ethanol with 50 mL of water. The solution was
cooled in an ice bath, and a suspension of the diazonium salt was added in two equal portions
under rigorous stirring for 1 h. The formed yellow precipitate of 2-(2-(4,4-dimethyl-2,6-
dioxocyclohexylidene)hydrazinyl)terephthalate (Na2HL1)) was filtered off, recrystallized from
methanol and dried in air.
Coordination reaction
2 mmol of Na2HL1 were dissolved in 50 mL of a DMF (99.8%, Aldrich) mixture (1:1, v/v),
and then 2 mmol of Cd(CH3COO)2·H2O (98%, Aldrich), were added, and the system was
stirred for 5 min. After 2 days at room temperature, yellow crystals precipitated, by the slow
evaporation method, which were then filtered off and dried in air.
X-ray single crystal diffraction and structure determination
Crystallographic data for the studied crystal were collected at 100 K and processed with the
CrysAlis PRO program [10]. The crystal structure was solved by Patterson method using the
SHELXS-97 and refined by full-matrix least-squares on F2 using SHELXL-2013 program [11].
An analytical absorption corrections were introduced [10]. For preparation pictures a
graphical program DIAMOND [12] was used. In the structure H atoms of aromatic rings were
treated as riding atoms in geometrically idealized positions, with C—H = 0.95 and Uiso(H) =
1.2Ueq(C) as well as H atoms of methyl and methylene groups were introduced in positions
calculated from geometry, with C—H = 0.98 Å and Uiso(H) = 1.5Ueq(C), and C—H = 0.99 Å
and Uiso(H) = 1.2Ueq(C) respectively. The main crystallographic data are listed in Table 1.

.
Table 1: Crystallographic data for [CdNa2(µ-L2)]n 6.34H2O
.
formula
[CdNa2(µ-L2)]n 6.34H2O
Formula weight (g/mol)
Crystal system
Space group
a (Å)
933.18
Trigonal
P3221
19.865 (6)
19.865 (6)
13.110 (3)
120
b (Å)
c (Å)
γ (˚)
V (Å3)
4480 (3)
3
Z
Color
Yellow
calculated density
λ (MoKα) (Å)
calculated density
Measured reflections
Independent reflections
Reflections [I > 2σ (I)]
Domain of θ (˚)
Tmin and Tmax
Index ranges
1.038
0.71073
Analytical
12825
8180
6345
2.8- 30.8
0.916 – 0.984
-9 ≤ h ≤ 28
-17 ≤ k ≤ 18
-18 ≤ l ≤ 9
307
Number of parameters
R1
7.1%
wR2
GooF
17.3%
1.14
After the refinement of the positions of all atoms in the structure, on the difference Fourier
map additional maxima were observed close to the sodium atom, and were introduced as
oxygen atoms derived from disordered water molecules. The disorder was modelled over
several positions of O atoms, which were refined isotropically with partial occupation factors.
As a result of low s.o.f factors of particular components of H2O molecules the maxima from
H atoms were not observed on the difference Fourier map. Bond distances and angles

calculated from the final atomic coordinates, as well as probable hydrogen bonds, are listed in
Tables 2 and 3 respectively.
Table 2: Selected bond distances (Å) and angles (°)
distances (Å)
angles (°)
Dodecahedron CdO8
O1—Cd—O1iii
Cd—O1
Cd—O1iii
Cd—O2
Cd—O2iii
Cd—O3i
Cd—O3ii
Cd—O4i
Cd—O4ii
2.356 (5)
2.356 (5)
2.357 (5)
2.357 (5)
2.371 (5)
2.371 (5)
2.565 (5)
2.565 (5)
144.1 (10)
132.704 (5)
84.217 (5)
135.113(5)
80.173(8)
101.481(8)
74.917(6)
170.138(5)
99.546(6)
96.252(6)
O1iii—Cd—O4ii
O2—Cd—O4ii
O2iii—Cd—O3ii
O3i—Cd—O1
O3ii—Cd—O3i
O4i—Cd—O3ii
O4ii—Cd—O2iii
O2—Cd—O2iii
O2—Cd—O3ii
Octahedron NaO6
Na-O1
2.393 (6)
2.342 (6)
2.437 (6)
2.347 (6)
2.378 (11)
2.425 (15)
O3ii—Na—O1W
O5iii—Na—O1W
O3ii—Na—O5iii
O3ii—Na—O1
95.0 (3)
79.8 (3)
151.5 (2)
80.01 (19)
97.4 (2)
164.3 (3)
108.8 (4)
98.9 (4)
112.9 (5)
82.7 (4)
77.95 (19)
73.8 (2)
87.5 (3)
77.0 (2)
157.2 (4)
Na-O3i
Na-O4ii
Na-O5ii
Na-O1W
Na-O2W
O5iii—Na—O1
O1W—Na—O1
O3ii—Na—O2W
O5iii—Na—O2W
O1W—Na—O2W
O1—Na—O2W
O3ii—Na—O4iii
O5iii—Na—O4iii
O1W—Na—O4iii
O1—Na—O4iii
O2W—Na—O4iii
ligand HL
O1—C1
O2—C1
O3—C8
O4—C8
O6— C16
N1—N2
N2—C11
C1—C2
C2—C7
C2—C3
C3—C4
C4—C5
C4—N1
C5—C6
C6—C7
C5—C8
C11—C16
C11—C12
C12—O5
C12—C13
C13—C14
C15—C14
C15—C16
C17—C14
C18—C14
1.270 (8)
1.247 (8)
1.248 (8)
1.258 (8)
1.245 (10)
1.306 (8)
1.338 (9)
1.514 (10)
1.383 (11)
1.405 (10)
1.400 (10)
1.409 (10)
1.413 (8)
1.396 (9)
1.372 (10)
1.499 (10)
1.453 (11)
1.475 (10)
1.221 (9)
1.500 (9)
1.520 (10)
1.529 (11)
1.511 (10)
1.549 (10)
1.524 (12)
O2—C1—O1
O3—C8—C5
123.0 (7)
118.1 (6)
89.62 (19)
97.2 (4)
122.3 (6)
155.8 (5)
87.8 (4)
Naiv—O3—Cdv
C8—O3—Cdv
O3—C8—O4
C8—O4—Nav
C8—O4—Cdv
C12—O5—Nav
O6—C16—C11
N1—N2—C11
N2—C11—C12
C3—C2—C1
135.0 (5)
121.7 (7)
119.3 (6)
124.9 (7)
118.1 (7)
120.4 (6)
118.7 (7)
120.8 (6)
118.3 (6)
119.5 (6)
118.9 (6)
121.2 (6)
122.8 (6)
119.4 (7)
118.1 (6)
121.1 (6)
115.3 (6)
109.4 (7)
108.6 (6)
118.8 (7)
109.1 (6)
111.4 (7)
C6—C7—C2
C4—C3—C2
C3—C4—C5
C6—C5—C4
C3—C4—N1
C6—C5—C8
C7—C6—C5
C4—C5—C8
C11—C16—C15
C11—C12—C13
O5—C12—C11
C12—C13—C14
C13—C14—C18
C13—C14—C15
O6—C16—C15
C15—C14—C17
C18—C14—C15
Symmetry codes: : (i )= 1+x-y, 1-y, 1/3-z, (ii) = 1-y, 1+x-y, -1/3+z, (iii) = y, x, -z,(iv) = x-y, 1-y, 1/3-z,
(v) = -x+y, 1-x, 1/3+z

Table 3: Geometry of hydrogen bonds (Å, °)
D–HˑˑˑA
D–H HˑˑˑA DˑˑˑA
D–HˑˑˑA
N1–H1ˑˑˑO4
0.88 1.95 2.606(8) 131
ˑˑˑO5
N1–H1
0.88 1.93 2.610(8) 133
0.98 2.58 3.507(10) 158
ˑˑˑO2vi
C17–H17B
Symmetry code: (vi) = -y+1, x-y+1, z+2/3
Results and discussion
Description of the crystal
The studied crystal has a three-dimensional polymeric structure that comprises of Cd2+ ions
connected to ligands (L), namely 2-(2-(4,4-dimethyl-2,6-
dioxocyclohexylidene)hydrazinyl)terephthalate [13], (Fig. 1). In the structure each cadmium
cation (lying in special position on the two-fold axis) is coordinated via carboxylate groups
{from terephthalate fragments} of four ligands in a bidentate way (Table. 2) resulting in the
formation of the eight-coordination sphere of Cd2+ that may be described as a distorted
dodecahedron DD-8 [14]. In the structure of ligand the six-membered ring of 4,4-dimethyl-
2,6-dioxocyclohexylidene fragment adopts approximately a half-chair conformation where
C11, C12, C13, C15 and C16 atoms are located in the same plane whereas C14 atom is
deviated of 0.65 (1) Å from the plane. Similarly, in the analogous fragments of the copper
polymeric structure [13] carbon atoms bonded to methyl groups are deviated of about 0.32
and 0.61 Å.

Figure 1: Cadmium polymeric structure. Symmetry codes: i 1+x-y, 1-y, 1/3-z, ii 1-y, 1+x-y, -
1/3+z, iii y, x, -z, iv x-y, 1-y, 1/3-z, v -x+y, 1-x, 1/3+z
In the studied crystal the intramolecular bifurcated hydrogen bond N1–H1···O4, N1–H1···O5
is observed forming two six-membered cyclic entities: O4/C8/C5/C4/N1/H1 and
O5/C12/C11/N2/N1/H1 (Fig. 1).
The polymeric structure is stabilized by the C–H···O intermolecular hydrogen bonds (Table.
3) as well as by the interactions of ligands with sodium cations via carbonyl O5 atom, and in a
monodentate manner via carboxylate O atoms: O1, O3 and O4, which also act as bridging
atoms between Cd2+ and Na+ ions. Additionally, sodium cations are involved in the
interactions with water molecules which form networks of O–H···O hydrogen bonds (not
discussed because of the complicated disorder of water molecules).
In the crystal the ribbons made up from ligands coordinated to cadmium and interacting with
sodium cations, (viewed down the c axis) stretch along [100], [010] and [110] directions (Fig.
2).

Figure 2: Packing diagram viewed down c axis
Grinding general procedure for the Knoevenagel condensation between aldehydes and
malononitrile
To understand which technique presents better results, we tested first the commercial salt and
.
the [CdNa2(µ-L2)]n 6.34H2O in solvent free conditions, using a mortar and a pestle.
Scheme 1: Synthesis of aldehydes with malonitrile and ethyl cyanoacetate uisng grindstone
method
Benzaldehyde was chosen for the initial assessment of the catalytic activity of the salt and
complex, and also the role that the additive will have in the reaction yield.

Without catalyst the yield, after 20 min, is only 5%, while the addition of the acid promotes
the reaction more intensively, producing 17% of product after 20 min. In the case of the
commercial salt, the highest value of yield produced without acid is 36%, while the addition
of the acid for the same amount of catalyst increases until 66%. In the case of CdHL the
behavior is similar, showing that the addition of acid is beneficial to the promotion of the
reaction (Table. 4).
Table 4: The effect of the amount of catalyst and of the nitric acid for the Knoevenagel
condensation, using benzaldehyde with malonitrile using the grindstone method. a
Nitric acid
amount
(mmol)
Catalyst amount
(mmol)
Yield
(%)
Nº
1
Catalyst
-
-
5
-
-
CdO
0.05
2
30
36
31
50
CdO
3
0.135
0.04
-
.
4
[CdNa2(µ-L2)]n 6.34H2O
-
.
5
[CdNa2(µ-L2)]n 6.34H2O
0.15
-
CdO
+
6
0.15+0.01
-
88
.
[CdNa2(µ-L2)]n 6.34H2O

7
8
-
-
0.05
0.005
0.005
17
40
66
79
61
95
CdO
CdO
9
0.34
0.034
0.02
.
10
11
12
[CdNa2(µ-L2)]n 6.34H2O
0.2
[CdNa2(µ-L2)]n 6.34H2O
0.3
0.03
.
CdO
+
0.15+0.01
0.016
[CdNa2(µ-L2)]n 6.34H2O
.
a Reaction conditions: All the reactions are carried out using benzaldehyde (1 mmol), malononitrile (1 mmol)
using a pestle and a mortar, room temperature, 20 min.
To improve further the yield, we tested a mixture made in situ and observed that the yield
increase to 88% without the additive and with the nitric acid reached 95%. This approach in
situ has been tested previous using ball milling for oxidation reactions. In the case of
Knoevenagel no report for the mixing in situ of 2 compounds that formed a very active specie.
To assess if for the same total molar amount, we can have different yields due to different
molar ratios of 2 metal from different sources, we tested 2 ratios and observed that increasing
the ratio of CdHL increased the yield. We tested the best catalyst, with the ratio (0.15/0.01), in
2
substituted aldehydes (Table. 5). The 4-hydroxybenzaldehyde and the 2-
hydroxybenzaldehyde were used. For the reaction without the additive and with 4-
hydroxybenzaldehyde reach 86% yield while the reaction with 2-hydroxybenzaldehyde
obtained 82%. Where we performed the same reactions using HNO3 as additive, all the yields
increase almost 10%. It is important to mention that we observed a trend, regarding the
presence of a substitute. As we can observe in the graph, the reaction with non-substituted
aldehyde always obtains higher yield that the ones with substituted groups. Between the
position para and orto, we observe a decrease in yield from the position 4 to 2, probably due

to steric hindrance where the OH group probably interacts with the aldehyde group,
deactivating partially the reactivity.
Table 5: The effect of the amount of catalyst and of the nitric acid for the Knoevenagel
condensation, using benzaldehyde and aldehydes derivatives with malonitrile using the
grindstone method. a
Nitric acid
amount
(mmol)
Yield
(%)
Catalyst amount
(mmol)
Nº
Aldeyde
Catalyst
1
2
3
4
5
-
-
-
-
5
-
O
0.005
17
88
95
82
CdO
+
-
0.016
-
0.15+0.01
[CdNa2(µ-
L2)]n 6.34H2O
.
O
CdO
+
[CdNa2(µ-
6
7
0.15+0.01
0.016
92
86
.
L2)]n 6.34H2O
OH
O
H
-
-
CdO
+
0.016
[CdNa2(µ-
8
0.15+0.01
94
.
L2)]n 6.34H2O
OH
a Reaction conditions: All the reactions are carried out using aldehyde (1 mmol), malononitrile (1 mmol) using a
pestle and a mortar, room temperature, 20 min.

Knoevenagel condensation under microwave irradiation conditions
One of the green chemistry principles is the necessity of minimize the use of energy, in order
to reduce the economic and environment impact of a chemical process. One step towards
energy efficiency is represented by alternative energy sources, such as microwave sources.
Although these technologies are not new, they are just recently emerging in process industry.
In this study we use microwave irradiation to promote a faster reaction with improved yields.
We tried two irradiation powers and used benzaldehyde as the test for our different catalysts.
The results are in table 6. We can observe that the increase in reactional time promotes an
increase in yields for all the reactions with different catalysts. In comparison with the solvent
free experiments, there is a slight decrease in the yield, most likely due to the effect of the
dispersion of the radiation (dipolar polarization), since the irradiation power applied is quite
small (7 W).
Table 6: Effect of irradiation power on Knoevenagel condensations yields(%) for several
catalysts vs. reaction time.
Entry
Catalyst
Time (min)
15
5
10
20
70W
1
2
3
CdO
14 %
38 %
73 %
20 %
43 %
73 %
29 %
47 %
80 %
37 %
59 %
82%
.
[CdNa2(µ-L2)]n 6.34H2O
CdO+[CdNa2(µ-L2)]n 6.34H2O
.
150 W
4
5
6
CdO
52 %
58 %
77 %
53 %
61 %
79 %
63 %
64 %
85 %
66 %
70 %
90%
.
[CdNa2(µ-L2)]n 6.34H2O
CdO+[CdNa2(µ-L2)]n 6.34H2O
.
The stirring in comparison with grinding leads to decrease in the yield. More studies have to
be performed to understand the role of the irradiation in the mechanism of the reaction.
In an alternative to improve the yield we tried to increase temperature, by increasing
irradiation applied to the medium. We observe that when 150 W of power was applied, the
temperature increased until 100ºC. We can observe an increase in the yield, but in comparison
with the solvent free procedure these values of yield are still smaller.

Conclusion
To sum up, we have synthesized the AHBD chelating ligand bearing β-diketone fragments as
well as carboxyl groups to obtain the polymeric CdII complex.
Regarding Knoevenagel condensation, it was found that a simple solvent-free method using a
mortar and a pestle, at room temperature, achieves higher yields than the microwave
technique. Therefore, the use of a solvent-free approach in fields such as synthesis in industry
or medicinal and pharmaceutical in order to generate molecules of biological interest using
Knoevenagel chemistry is a possibility to be explored.
Furthermore, the combination of both sources of metal to promote an increase in yield was
tested for the first time and an increment in the yield due to the mixture is also an issue worth
to be explored.
Supplementary data
CCDC 1542120 contains the supplementary crystallographic data for the title compound.
These data can be obtained free of charge from the Cambridge Crystallographic data centre,
12 Union Road, Cambridge CB2 1EZ, UK. E-mail: deposit@ccdc.cam.uc.uk.
Acknowledgements
The authors wish to thank Professor T. Lis for the crystallographic data collection performed
at the Faculty of Chemistry, University of Wroclaw, Poland.
FCT for projects UID/QUI/00100/2013, PTDC/QEQ-ERQ/1648/2014 and PTDC/QEQ-
QIN/3967/2014. APCR, GAOT and JW also acknowledge FCT for SFRH/BPD/90883/2012,
Ph.D. CATSUS PD/BD/ and Ph.D. CATSUS PD/BD/114397/2016 grants, respectively. The
authors also acknowledge the Portuguese NMR Network (IST-UL Centre) for access to the
NMR facility, and the IST Node of the Portuguese Network of mass-spectrometry (Dr.
Conceição Oliveira) for the ESI-MS measurements.

Formatting and funding sources
This research did not receive any specific grand from funding agencies in the public,
commercial or not-for-profit sectors.
Conflicts of interest
The authors declare no competing financial interest.
References
[1] L. Muralidhar, C.R. Girija, J. Saudi Chem. Soc. 18 (2014) 541–544.
[2] K. F. Shelke, R. E. Khadse, Der Pharma Chemica, 7(1) (2015) 191-196.
[3] [(a) A.K. Sinha, V. Kumar, A. Sharma, A. Sharma, R. Kumar Tetrahedron, 63 (2007), p.
11070. (b) Y. Hajbi, F. Suzenet, M. Khouili, S. Lazar, G. Gillaumet Tetrahedron, 63 (2007),
p. 8286.
[4] B.K. Pchelka, A. Loupy, A. Petit Tetrahedron, 62 (2006), p. 10968.
[5] M.C. Reid, J.H. Clark, D.J. Macquarrie Green Chem., 8 (2006), p. 437.
[6] G.G. Muccioli, J.H. Poupaert, J. Wouters, B. Norberg, W. Poppitz, G.K.E. Scriba, D.M.
Lambert Tetrahedron, 59 (2003), p. 1301.
[7] A. Loupy Microwave in Organic Synthesis Wiley-VCH, Weinheim (2006).
[8] C.O. Kappe, Chem. Soc. Rev., 37 (2008), p. 1127.
[9] a) M. N. Kopylovich, K. T. Mahmudov, M. F. C. Guedes da Silva, L. M. D. R. S. Martins,
M. L. Kuznetsov, T. F. S. Silva, J. J. R. F. Silva, A. J. L. Pombeiro, J. Phys. Org. Chem.
2011, 24, 764–773; b) M. N. Kopylovich, M. F. C. Guedes da Silva, L. M. D. R. S. Martins,
K. T. Mahmudov, A. J. L. Pombeiro, Polyhedron 50 (2013) 374–382; c) K. T. Mahmudov, M.
N. Kopylovich, M. F. C. Guedes da Silva, G. S. Mahmudova, M. Sutradhar, A. J. L.
Pombeiro, Polyhedron 60 (2013) 78–84; d) A. M. Maharramov, R. A. Aliyeva, I. A. Aliyev,
F. G. Pashaev, A. G. Gasanov, S. I. Azimova, R. K. Askerov, A. V. Kurbanov, K. T.

Mahmudov, Dyes Pigm. 85 (2010) 1–6; e) M. N. Kopylovich, K. T. Mahmudov, M. Haukka,
K. V. Luzyanin, A. J. L. Pombeiro, Inorg. Chim. Acta 374 (2011) 175–180; f) M. N.
Kopylovich, K. T. Mahmudov, M. F. C. Guedes da Silva, A. M. Kirillov, A. J. L. Pombeiro,
Dalton Trans. 40 (2011) 12472–12478; g) K. T. Mahmudov, A. M. Maharramov, R. A.
Aliyeva, I. A. Aliyev, R. K. Askerov, R. Batmaz, M. N. Kopylovich, A. J. L. Pombeiro, J.
Photochem. Photobiol. A 219 (2011) 159–165; h) K. T. Mahmudov, M. F. C. Guedes da
Silva, A. M. Kirillov, M. N. Kopylovich, A. Mizar, A. J. L. Pombeiro, Cryst. Growth Des. 13
(2013) 5076–5084; i) M. Sutradhar, L. M. Carrella, E. Rentschler, Eur. J. Inorg. Chem.
(2012) 4273–4278; j) M. Sutradhar, T. R. Barman, G. Mukherjee, M. G. B. Drew, S. Ghosh,
Inorg. Chim. Acta 363 (2010) 3376–3383; k) M. Sutradhar, A. J. L. Pombeiro, Coord. Chem.
Rev. 265 (2014) 89–124.
[10] Agilent (2011). CrysAlis PRO. Agilent Technologies, Yarnton, England.
[11] G. M. Sheldrick, Acta Cryst. A64 (2008) 112–122.
[12] K. Brandenburg, (2006). DIAMOND. Crystal Impact GbR, Bonn, Germany.
[13] R. Jlassi, A. P. C. Ribeiro, M. F. C. Guedes da Silva, K. T. Mahmudov, M. N.
Kopylovich, T. B. Anisimova, H. Naïli, G. A. O. Tiago and A. J.L.Pombeiro. Polynuclear
Copper(II) Complexes as Catalysts for the Peroxidative Oxidation of Cyclohexane in a Room-
Temperature Ionic Liquid. Eur. J. Inorg. Chem. (2014) 4541–4550.
[14] IUPAC Recommendation.