Silica-Supported Ni(II)–DABCO Complex: An Efficient and Reusable Catalyst for the Heck Reaction

Article abstract of DOI:10.1007/s10562-016-1880-9

Abstract: An interesting nickel-based catalyst supported on DABCO-functionalized silica was successfully prepared and evaluated as heterogeneous nanocatalyst in Heck cross coupling reaction of various aryl halides and methyl acrylate. The as-prepared nanocatalyst was well characterized by FT-IR, FE-SEM, TEM, XRD, SEM-EDX, ICP and TGA techniques and found to be highly efficient in the reaction system in terms of activity and recyclability. Graphical Abstract: This work provides an economical and heterogeneous catalytic system based nickel nanoparticle supported on DABCO functionalized silica for the Heck cross-coupling reaction of various aryl halides with methyl acrylate. [Figure not available: see fulltext.]

Full text of DOI:10.1007/s10562-016-1880-9

Catal Lett
DOI 10.1007/s10562-016-1880-9
Silica-Supported Ni(II)–DABCO Complex: An Eicient
and Reusable Catalyst for the Heck Reaction
Abdol R. Hajipour1,2 · Parisa Abolfathi1
Received: 7 August 2016 / Accepted: 25 September 2016
© Springer Science+Business Media New York 2016
Abstract An interesting nickel-based catalyst supported
on DABCO-functionalized silica was successfully pre-
pared and evaluated as heterogeneous nanocatalyst in Heck
cross coupling reaction of various aryl halides and methyl
acrylate. The as-prepared nanocatalyst was well charac-
terized by FT-IR, FE-SEM, TEM, XRD, SEM-EDX, ICP
and TGA techniques and found to be highly eicient in the
reaction system in terms of activity and recyclability.
Graphical Abstract This work provides an economical
and heterogeneous catalytic system based nickel nanoparti-
Keywords DABCO · Nickel(II) · Heterogenous catalyst ·
cle supported on DABCO functionalized silica for the Heck
cross-coupling reaction of various aryl halides with methyl
acrylate.
Mizoroki–Heck reaction
1 Introduction
Metal-catalyzed cross-coupling reactions are one of the
most important synthetic methods in organic synthesis [1].
Among the many diferent protocols for the synthesis of
carbon–carbon and carbon–heteroatom bonds, Palladium is
the most popular metal used for such reactions in both aca-
demic and large-scale synthesis [1, 2]. However, in modern
organic synthesis, considerable interest has been focused on
palladium-free conditions and development of available and
cost-efective transition metal catalysts [3–6]. Cross-cou-
pling of aryl halides and acrylates in Mizoroki–Heck reac-
tion is one of the most eicient routes for the vinylation of
aryl halides. Cross-coupling of aryl halides and acrylates in
Mizoroki–Heck reaction reaction is one of the most eicient
routes for the vinylation of aryl halides, which are an impor-
tant class of organic compounds and the building blocks of
a wide range of biological, pharmaceutical, polymer indus-
tries and medicinal chemistry [7–9]. Recently, nickel-based
catalytic systems have gained substantial interest in coupling
Electronic Supplementary Material The online version
of this article (doi:10.1007/s10562-016-1880-9) contains
supplementary material, which is available to authorized users.
* Abdol R. Hajipour
haji@cc.iut.ac.ir
1
Pharmaceutical Research Laboratory, Department
of Chemistry, Isfahan University of Technology,
Isfahan 84156, Iran
2
Department of Neuroscience, Medical School, University
of Wisconsin, 1300 University Avenue, Madison,
WI 53706-1532, USA
1 3

A. R. Hajipour, P. Abolfathi
Scheme 1 The nanocatalyst
preparation
Fig. 3 XRD patterns of Ni(II)–DABCO@SiO2 catalyst
Fig. 1 FT-IR spectra of pure silica (a), SiO2-C3H6-Cl (b), SiO2-
C3H6-DABCO (c)
Fig. 4 TGA analysis of Ni(II)–DABCO@SiO2 catalyst
Fig. 2 SEM-EDX spectrum of Ni(II)–DABCO@SiO2 catalyst
recyclability and high catalyst loading (up to 10 mol%) [17–
24]. Most of the issues associated with homogenous catalyst
can be solved by immobilizing the homogeneous catalysts
on various insoluble supports [25–32]. These solid-sup-
ported catalysts can be simply separated from reaction mix-
ture via iltration or centrifugation and successfully reused.
reactions, in particular, for Heck-type couplings [10–16]. It
should be noted that these reactions have been extensively
performed in a homogeneous phase, which have some major
limitations such as separation and puriication of the target
product from the reaction media, high toxicity, the lack of
1 3

Silica-Supported Ni(II)–DABCO Complex: An Eicient and Reusable Catalyst for the Heck Reaction
Supported catalysts are produced by the reaction of a modi-
ied surface with suitable functional groups on the catalyst
atoms. There are numerous modiication or heterogenization
methodologies for metallic species based on various sub-
strates such as silica [33, 34], polymers [35, 36], alumina
[37, 38], zeolites [39, 40], carbon nanotube [41–44] and
etc. Many diferent stabilizers such as Ligands [45], poly-
mers [46], ionic liquids (ILs) [47], and dendrimers [48] have
been developed as common metal-stabilizers in literature.
Grafting of the ionic liquids on the solid-supported catalysts
provides a material with a charged surface. It is found that
ILs is able to stabilize metallic species through electrostatic
interactions. In continuation of our investigations to improve
eco-friendly green solid catalyst [35, 49–52], The role of
DABCO was investigated by comparing the catalysis with
silica supported nickel(II), The DABCO grafted on silica as
an efective ligand and a quaternary ammonium salt, plays
an important role in increasing the stability and reactivity of
metal NPs through the synergistic efect of coordination and
electrostatic interactions.
2 Experimental
2.1 General Methods
All chemical reagents were purchased from Merck Chemi-
1
cal Company and used without further puriication. H-
NMR spectra were recorded on a Bruker 400 spectrometer
using deutrated CDCl3 as solvent and tetramethylsilane
(TMS) as internal standard. FT-IR spectroscopy (JASCO
FT-IR 680-Plus spectrophotometer) was employed for char-
acterization of products. Also we used Inductive coupled
plasma Perkin Elmer Optima 7300 DV. Gas chromatogra-
phy (GC) (BEIFIN 3420 gas chromatograph equipped with
a Varian CP SIL 5CB column: 30 m, 0.32 mm, 0.25 mm)
was used for consideration of reaction conversions and
yields. Scanning electron micrographs of the catalyst were
taken on [FE-SEM, HITACHI (S-4160)]. The 3-n-propyl-
1-azonia-4-azabicyclo[2.2.2]octane chloride (DABCO-
SIL) was prepared according to the literature method [54].
Compared with other ammonium salts, 1,4-Diazabicy-
clo[2.2.2]octane (DABCO) is known as an inexpensive, eco-
friendly, high reactive, easy to handle and non-toxic base
catalyst for various organic transformations [53]. The as-
prepared material was found to be an eicient and recyclable
nanocatalyst for Mizoroki–Heck coupling reaction of various
aryl halides with methyl acrylate giving quantitative yields.
2.2 Preparation of 3-Chloropropyl Functionalized
Silica
Silica-gel (1.5 g) was irst suspended in hydrochloric acid
for 24 h, washed several times with deionized water until
the pH value was then adjusted to 7, and dried under vac-
uum at 120 °C for 8 h. Then, A mixture of dry toluene
Fig. 5 SEM photographs
of Pure SiO2 (a) and Ni(II)–
DABCO@SiO2 (b–d)
1 3

A. R. Hajipour, P. Abolfathi
Fig. 6 TEM images of the fresh catalyst (a, b) and recovered catalyst (c)
(10 mL) and activated silica was reluxed for 24 h after
addition of 3-chloropropyltriethoxysilane (1.46 mL) and
triethylamine (as a catalyst, 0.2 mL). Afterward, the sol-
vent was decanted and the silica was washed thoroughly
with toluene, ethanol, deionized water and methanol. The
obtained product was then dried under vacuum drying at
60°C for 4 h.
2.4 Preparation of Ni(II)–DABCO@SiO2
For preparation of the catalyst, irstly, silica-DABCO
(0.5 g) was dispersed in methanol (20 mL). Afterward,
NiCl2 (0.25 mmol, 0.032 g) was added to this solution. The
mixture was reluxed for 24 h. After stirring, the catalyst
was iltered, washed several times with methanol to remove
unreacted NiCl2 and dried under vacuum at 50°C.
2.3 Preparation of Silica Grafted
n-Propyl-4-aza-1-azoniabicyclo[2.2.2]octane
chloride
3 Results and Discussion
3-Chloropropyl functionalized silica (1 g) was reacted with
1,4-diazabicyclo[2.2.2]octane (DABCO) (1.12 g, 10 mmol)
in dry acetone (40 mL) and reluxed for 36 h to obtain
DABCO chloride salt grafted on to the surface of silica
(SB-DABCO). Afterward, the reaction mixture was iltered
and washed successively with acetone, ethanol, and metha-
nol and dried at 50°C for 4 h under vacuum.
3.1 Preparation and Characterization of the Catalyst
The pathway to synthesize Ni(II)–DABCO@SiO2 is
schematically described in Scheme 1. The compound
synthesized was characterized using techniques including
elemental analysis (EA), Thermal gravimetric analyses
1 3

Silica-Supported Ni(II)–DABCO Complex: An Eicient and Reusable Catalyst for the Heck Reaction
Table 1 Efect of diferent parameters for the reaction of bromoben-
zene with methyl acrylate
(Fig. 4). The mass loss at temperatures below 100 °C was
due to the elimination of water molecules from the sur-
face of the silica material and the second mass loss above
300 °C was attributed to the decomposition of the organic
groups grafted to the silica surface. Thus, the TGA anal-
ysis results demonstrate that the catalyst is stable over
300 °C.
Entry
Solvent
T (°C)
Base
Yielda
1
DMF
DMF
DMF
DMF
DMF
DMSO
Toluene
EtOH
DMF
DMF
DMF
DMF
80
80
K2CO3
K3PO4
KOH
NaHCO3
NEt3
42
46
29
38
75
70
39
61
80
95
86b
95c
2
3
80
4
80
Size, shape and morphology of the nanocatalyst were
investigated using Scanning electron microscopy (FE-
SEM) and transmission electron microscopy (TEM) imag-
ing techniques (Fig. 5). As displayed in Fig. 6, TEM images
of the fresh catalyst conirm that nickel nanoparticles were
created in discrete spherical shape without any signs of
aggregations. The particle size histogram depicts that nano-
sized particles have average diameter ranging about 13 nm
(Fig. 6d), indicating that DABCO-SiO2 support can efec-
tively isolate adjacent Ni nanoparticles.The micrograph
obtained by SEM showed a clear change in morphology
after immobilization of organic groups on to the silica sup-
port (Fig. 5b). As shown in Fig. 5c, d, the organic compo-
nents with spherical morphology and nanometer-sized par-
ticles were created on the surface of silica.
5
80
6
80
NEt3
7
80
NEt3
8
80
NEt3
9
90
NEt3
10
11
12
100
100
100
NEt3
NEt3
NEt3
Reaction conditions: bromobenzene (1 mmol), methyl acrylate
(1.2 mmol), amount of catalyst (15 mg), time (4 h), base (3 mmol),
solvent (4 mL)
aIsolated yield
bAmount of catalyst used: 10 mg
cAmount of catalyst used: 18 mg
3.2 Catalytic Tests
(TGA), Inductively coupled plasma analysis (ICP),
FT-IR, TEM, SEM, EDX and XRD.
To evaluate the catalytic activity of the nanocatalyst and
to determine optimal conditions for Mizoroki–Heck cross-
coupling reaction, methyl acrylate and bromobenzene was
selected as model substrates and were examined under
diferent parameters such as bases, solvent, temperature
conditions and catalyst loading (Table 1). In our irst set
of experiments, the model reaction was performed in the
presence of DMF as a solvent and 15 mg of catalyst in dif-
ferent bases at 80°C. The results revealed that the yield of
product was enhanced to 75% when NEt3 was used as base.
Subsequently, we studied the impact of various solvets on
the eiciency of this procedure. On the basis of this study,
DMF was chosen as the most efective solvent for the reac-
tion. To obtain the optimum temperature, the model reac-
tion was also carry out at diferent temperatures and it was
found that reaction temperature plays a critical role in this
catalytic system. As you can see in Table 1, the best result
was obtained when the reaction was conducted at 100°C.
We also optimized the catalyst loading, employing difer-
ent amounts of catalyst. The good reaction time and higher
yield were observed when the model reaction was carried
out with 15 mg of catalyst. For less than this amount, there
was a signiicant decrease in the percentage yield of the
product. After optimization, Ni(II)–DABCO@SiO2 cata-
lysed Heck reactions were examined with various types
of aryl halides (chlorides, bromides and iodides). Results
summarized in Table 2 show that aryl iodides and aryl bro-
mides were efectively converted the corresponding Heck
The presence of the functional groups on the silica
surface can be observed by FT-IR Spectroscopy. In the
FT-IR spectrum depicted in Fig. 1, the absorption peak
at 1098 cm−1 corresponded to the Si–O–Si vibration. A
typical bond around 2924 cm−1 should be attributed to
aliphatic C–H bond stretching, the signal at 1468 cm−1
indicates aliphatic CH2 bending vibrations and the char-
acteristic peak at 1384 cm−1 represents C–N stretching
vibration. These facts revealed the successful immobili-
zation of DABCO on the silica surface.
The presence of the organic phase on the silica sur-
face was also conirmed by elemental analysis. Based
on the elemental analysis, the loading amount of nitro-
gen atom was 1.07 mmol g−1. The EDX results indicated
the presence of oxygen, nitrogen, silicon, chloride, car-
bon and nickel in the composites, which conirmed that
Ni(II)–DABCO@SiO2 have been successfully synthe-
sized (Fig. 2). Inductively coupled plasma (ICP) analysis
showed that the Ni content was 0.32 mmol g−1 in the inal
solid product. Figure 3 depicts the XRD pattern pattern
of catalyst that matched well with that of it (Reference
code: 01-079-2297) shows the presence of Ni(II) com-
plex on the amorphous silica support. The wide difrac-
tion peak at 2θ = 23° attributed to SiO2.
Thermal gravimetric analysis (TGA) was carried out to
study the thermal stability of nanocatalyst. TGA of silica/
DABCO shows two characteristic decomposition stages
1 3

A. R. Hajipour, P. Abolfathi
O
Table 2 Reaction of diverse
aryl halides with methyl
acrylate
X
OMe
Nano
NEt
3
catalyst,
OMe
O
R
oC
DMF,100
R
Entry
Ar–X
Product
Time/ h
Yield
O
I
1
3
97
OMe
O
MeO
I
OMe
2
3
4
5
3
1.5
4
94
98
95
87
MeO
O
OMe
O2N
I
O2N
O
Br
OMe
O
Me
O
Br
Br
Br
Br
Me
5
Me
O
O
Me
6
7
3.5
3.5
3
96
97
97
84
87
O
NC
OMe
NC
O
OMe
O2N
8
O2N
O
Cl
9
7
OMe
O
OMe
O2N
Cl
10
6
O2N
O
MeO
MeO
Cl
OMe
OMe
OMe
11
12
13
7
8
79
72a
67a
MeO
MeO
O
O
I
O2N
Br
10
O2N
O
O
Cl
Cl
14
15
15
15
31a
OMe
OMe
47b
Reaction conditions: aryl halide (1 mmol), methyl acrylate (1.2 mmol), base (3 mmol), solvent
(4 mL), Ni(II)-DABCO@SiO2 catalyst (15 mg), 100°C, According to isolated yields
aReaction conditions: aryl halide (1 mmol), methyl acrylate (1.2 mmol), base (3 mmol), solvent
(4 mL), ligand-Free Ni@SiO2 catalyst (15 mg), 100°C, Reactions were monitored using GC
bLigand-Free Ni@SiO2 catalyst (25 mg) was used at 120°C, Reaction was monitored using
GCReusability and Heterogeneity Test
1 3

Silica-Supported Ni(II)–DABCO Complex: An Eicient and Reusable Catalyst for the Heck Reaction
obtained upon catalyst removal. The ICP analysis in good
agreement with these results, because only 0.043 ppm of Ni
being obtained in the hot iltrate aqueous solution. On the
other hand, TEM image of the reused catalyst demonstrates
that the structure of Ni/silica has no signiicant change in
comparison with fresh catalyst (Fig. 6c), Also, the observed
ICP analysis from the aqueous solution of reaction mixture
(after 6th run) displayed only a low amount of nickel metal
(0.088 ppm) was leach out from the catalyst, indicating
that the attachment between nickel nanoparticles and silica
matrix is suiciently strong (Fig. 7).
Fig. 7 Reusability of the catalyst in the Suzuki–Miyaura
4 Conclusions
products in excellent yields. Also, for the less active chlo-
robenzene and its derivatives a longer time was needed to
obtain a moderate yields. The electronic efect on the yields
and reaction times was also examined in this reaction sys-
tem. Overall, the coupling reaction of methyl aclylate with
electron withdrawing aryl halides gave better conversions
in shorter reaction times. In order to clarify the efect of
grafted DABCO on the catalyst performance, a new cata-
lytic system based on nickel immobilized onto silica sur-
face (Ni@SiO2) was easily prepared without the use of
DABCO section. This catalytic system was then applied
to the Heck coupling of various aryl halides with methyl
acrylate (Table 2, entry 12–15). It can be clearly seen that
our catalyst is superior to ligand-Free Ni@SiO2 catalyst
system in terms of reaction condition, reaction time and
yield, indicating that the DABCO as an important func-
tional entity acts as a highly stable linker or/and a chela-
tor to graft catalysts onto silica and increases the stability
and reactivity of Ni(II) species during the production pro-
cess by synergistic efect of coordination and electrostatic
interactions.
In conclusion, silica-DABCO-Ni(II) complex nanocatalyst
was successfully synthesized and well characterized by dif-
ferent techniques. The obtained product was then used as
heterogeneous catalyst for Heck–Mizoroki cross-coupling
reaction and exhibited a high catalytic activity and could be
easily recovered at least six times.
Acknowledgments We gratefully acknowledge the funding sup-
port received for this project from the Isfahan University of Technol-
ogy (IUT), IR of Iran, and Isfahan Science and Technology Town
(ISTT), IR of Iran. Further inancial support from the Center of Excel-
lence in Sensor and Green Chemistry Research (IUT) is gratefully
acknowledged.
References
1. Diederich F, Stang PJ (2008) John Wiley & Sons, New York
2. Tsuji J (2002) John Wiley & Sons, New York
3. Jana R, Pathak TP, Sigman MS (2011) Chem Rev
111:1417–1492
4. Wang L, Li P, Zhang Y (2004) Chem Commun 5:514–515
5. Yang CT, Zhang ZQ, Liu YC, Liu L (2011) Angew Chem Int Ed
123:3990–3993
The level of recyclability of catalyst is highly prefer-
able for its industrial applications. In order to studied this
issue, the recovery of the catalyst was examined by using
bromobenzene and methyl acrylate under optimized reac-
tion conditions. For this, after each run, the catalytic sys-
tem was separated from the reaction mixture by iltration
and washed with acetone several times, dried at 70°C, and
used for the next cycle. As shown in Fig. 5, this catalyst
system could be reusable at least for 6 times without any
signiicant decreasing in its catalytic performance until
the ifth reuse. However, the yield of the reaction in the
6th run declined to 74%. To probe the nature of the active
species, i.e., surface or leached Ni, a hot-iltration test was
performed by using of bromobenzene and methyl acrylate
as coupling partners. The solid catalyst was separated
from the reaction mixture after 1 h (34%, analyzed by GC)
and the iltrate was continued for an additional 3 h. After
this time, no further improvement in isolated yield was
6. Zhang L, Zuo Z, Leng X, Huang Z (2014) Angew Chem Int Ed
53:2696
7. Adeli M, Mehdipour E, Bavadi M (2010) J Appl Polym Sci
116:2188–2196
8. Magano J, Dunetz J (2011) Chem Rev 11:2177–2250
9. Nicolaou KC, Bulger PG, Sarlah D (2005) Angew Chem Int Ed
44:4442–4489
10. Bobes FG, Fu GC (2006) J Am Chem Soc 128:5360–5361
11. Leowanawat P, Zhang N, Resmerita AM, Rosen BM, Percec V
(2011) J Org Chem 76:9946–9995
12. Knappke CEI, von Wangelin AJ (2010) Angew Chem Int Ed
49:3568–3570
13. Hu X (2011) Chem Sci 2:1867–1886
14. Zultanski SL, Fu GC (2013) J Am Chem Soc 135:624–627
15. Zhang N, Hofman DJ, Gutsche N, Gupta J, Percec V (2012) J
Org Chem 77:5956–5964
16. Xian YL, Guo WH, He GZ, Pan Q, Zhang X (2014) Angew
Chem Int Ed 53:1
17. Matsubara R, Gutierrez AC, Jamison TF (2011) J Am Chem Soc
133:19020–19023
1 3

A. R. Hajipour, P. Abolfathi
18. Tasker SZ, Gutierrez AC, Jamison TF (2014) Angew Chem Int
Ed 53:1858–1861
38. Kannisto H, Arve K, Pingel T, Hellman A, Harelind H, Eranen
K, Olsson E, Skoglundh M, Murzin DY (2013) Catal Sci Tech
3:644–653
19. Liu C, Tang S, Liu D, Yuan J, Zheng L, Meng L, Lei A (2012)
Angew Chem Int Ed 51:3638–3641
39. Kandepi VKM, Narender N (2012) Catal Sci Tech 2:471–487
40. Magne V, Garnier T, Danel M, Pale P, Chassaing S (2015) Org
Lett 17:4494–4497
20. Rosen BM, Quasdorf KW, Wilson DA, Zhang N, Resmerita AM,
Garg NK, Percec V (2010) Chem Rev 111:1346–1416
21. Han FS (2013) Chem Soc Rev 42:5270–5298
22. Zhao YL, Li Y, Li SM, Zhou YG, Sun FY, Gao LX, Han FS
(2011) Adv Synth Catal 353:1543–1550
41. Pan HB, Wai CM (2011) New J Chem 35:1649–1660
42. Cornelio B, Rance GA, Laronze-Cochard M, Fontana A, Sapi J,
Khlobystov AN (2013) J Mater Chem A 1:8737–8744
43. Rodriguez-Perez L, Pradel C, Serp P, Gomez M, Teuma E (2011)
ChemCatChem 3:749–754
23. Li XJ, Zhang JL, Geng Y, Jin
78:5078–5084
Z (2013) J Org Chem
24. Kuroda JI, Inamoto K, Hiroya K (2009) Eur J Org Chem
14:2251–2261
44. Sairanen E, Karinen R, Borghei M, Kauppinen EI, Lehtonen J
(2012) ChemCatChem 4:2055–2061
25. Sharma RK, Pandey A, Gulati S (2012) Polyhedron 45:86–93
26. Sharma RK, Pandey A, Gulati S (2012) Appl Catal A 431:33–41
27. Sharma RK, Gulati S (2012) J Mol Catal A Chem 363:291–303
28. Sharma RK, Rawat D (2012) Inorg Chem Commun 17:58–63
29. Sharma RK, Sharma C (2011) Catal Commun 12:327–331
30. Sharma RK, Sharma C (2010) J Mol Catal A Gen 332:53–58
31. Sharma RK, Sharma S (2014) Dalton Trans 43:1292–1304
32. Sharma RK, Sharma S, Gaba G (2014) RSC Adv 4:49198–49211
33. Isfahani AL, Mohammadpoor-Baltork I, Mirkhani V, Khosro-
pour AR, Moghadam M, Tangestaninejad S, Kia R (2013) Adv
Synth Catal 355:957–972
45. Amadio E, Scrivanti A, Chessa G, Matteoli U, Beghetto V, Ber-
toldini M, Rancan M, Dolmella A, Venzo A, Bertani R (2012) J
Organomet Chem 716:193–200
46. Ranganath KV, Onitsuka S, Kumar AK, Inanaga J (2013) Catal
Sci Tech 3:2161–2181
47. Xu Y, Zhang Z, Zheng J, Du Q, Li Y (2013) Appl Organomet
Chem 27:13–18
48. Ornelas C, Ruiz J, Salmon L, Astruc D (2008) Adv Synth Catal
350:837–845
49. Hajipour AR, Azizi G (2013) Green Chem 15: 1030–1034
50. Hajipour AR, Azizi G (2014) RSC Adv 4:20704–20708
51. Hajipour AR, Azizi G (2014) Chin J Catal 35: 1547–1554
52. Hajipour AR, Hosini DM, Mohammadsaleh F (2016) New J
Chem. doi:10.1039/c6nj00612d
34. Singh B, Jain SL, Rana BS, Khatri PK, Sinha AK, Sain B (2010)
ChemCatChem 2:1260–1264
35. Hajipour AR, Boostani E, Mohammadsaleh F (2015) RSC Adv
5:24742–24748
53. Beheshtia YS, Khorshidi M, Heravi MM, Baghernejad B (2010)
Eur J Chem 3:232–235
36. Kim JH, Kim JW, Shokouhimehr M, Lee YS (2005) J Org Chem
70:6714–6720
54. Hasaninejad A, Shekouhy M, Golzar N, Zare A, Doroodmand
MM (2011) Appl Catal A Gen 402:11–22
37. Nimkar A, Ramana M, Betkar R, Ranade P, Mundhe B (2016)
New J Chem 40:2541–2546
1 3