NiFe2O4 nanoparticles: A green and reusable heterogeneous catalyst for the synthesis of spiro[indole-3,2′-pyrrole]-2,5′(1H,1′H)-diones

Article abstract of DOI:10.3184/174751916X14640003438169

NiFe₂O₄ nanoparticles were used as an efficient catalyst for the preparation of spiro[indole-3,2′-pyrrole]-2,5′(1H,1′H)-diones by the multicomponent condensation reaction of arylamines, acetylenedicarboxylates and isatins under reflux conditions in ethanol.

Full text of DOI:10.3184/174751916X14640003438169

JOURNAL OF CHEMICAL RESEARCH 2016
VOL. 40 JULY, 397–399
RESEARCH PAPER 397
NiFe2O4 nanoparticles: A green and reusable heterogeneous catalyst for the
synthesis of spiro[indole-3,2'-pyrrole]-2,5'(1H,1'H)-diones
Roghaiieh Meghyasi, Javad Safaei-Ghomi* and Mahboubeh A. Sharif
Department of Chemistry, Qom Branch, Islamic Azad University, Iran
NiFe2O4 nanoparticles were used as an efficient catalyst for the preparation of spiro[indole-3,2'-pyrrole]-2,5'(1H,1'H)-diones by the multi-
component condensation reaction of arylamines, acetylenedicarboxylates and isatins under reflux conditions in ethanol.
Keywords: spiro[indole-3,2'-pyrrole]-2,5'(1H,1'H)-dione; isatin; NiFe2O4 nanoparticles; One-pot; robust catalyst
Introduction
received important attention in recent years. To overcome the
separation limitations of the nanocatalysts, magnetic materials
have used as recoverable catalysts.14,15
Herein we wish to report the synthesis of spiro[indole-
3,2'-pyrrole]-2,5'(1H,1'H)-diones by the multi-component
condensation reaction of arylamines, acetylenedicarboxylates
and isatins in the presence of NiFe2O4 nanoparticles under
reflux conditions in ethanol (Scheme 1).
Spirooxindoles represent an important class of compounds
owing to their wide range of biological activities such
as antiproliferative,1 anticancer,2 MDM2 inhibitors3 and
can also serve as synthetic intermediates for many kinds
of pharmaceuticals or drug precursors.4 Therefore, the
development of simple methods for the synthesis of
spirooxindoles is a major challenge and an interesting field in
chemistry. Multicomponent reaction is one of the most common
methods that have been utilised for the synthesis of a variety
of biologically active compounds. Undoubtedly, the synthesis
of spirooxindoles through multicomponent reactions (MCR)
has been paid much attention due to experimental simplicity,
excellent synthetic efficiency, inherent atom economy, and
low environmental impact.5,6 The synthesis of spirooxindoles
has been reported in the presence of diverse catalysts
including DBU,7 piperidine,8 ZnS nanoparticle,9 BF3·OEt2,10
p-toluenesulfonic acid11,12 and NaHCO3.13 However, some of
the reported methods tolerate disadvantages including long
reaction times, harsh reaction conditions and use of toxic and
non-reusable catalyst. Consequently, to avoid these limitations,
the searching of an efficient, easily available catalyst with high
catalytic activity for the preparation of spirooxindoles is still
favoured. Ideally, utilising environmental and green catalysts
which can be simply recycled at the end of reactions has
Results and discussion
To optimise the reaction conditions, the condensation reaction
of 4-methylaniline, dimethyl acetylenedicarboxylate and
isatin was selected as a model study to examine the effects of
the catalyst and solvent for the synthesis of spiro[indole-3,2'-
pyrrole]-2,5'(1H,1'H)-diones (Scheme 2). A wide variety of
catalysts including piperidine, ZnCl2, NiCl2, NiO, FeCl3, Fe3O4
and NiFe2O4 NPs were employed to test their efficacy for the
synthesis of spiro[indole-3,2'-pyrrole]-2,5'(1H,1'H)-diones.
Then, we optimised the amount of NiFe2O4 NPs required;
the optimum amount was found to be 0.3 mol%. Also, we
examined the reaction in different solvents including water
DMF, acetonitrile and ethanol. Ethanol was found to be the best
solvent, in which the product was obtained in 93% yield (Table
1). Unfortunately, when the model reaction was carried out in
water, the desired product was only obtained in 60% yield.
R'
O
R
CO2
CO2
R
CO2
R'
+
NHAr
O
NPs
NiFe2O4
2 ArNH2
+
O
EtOH
HN
N
N
R
H
Ar
O
Scheme 1 Synthesis of spiro[indole-3,2'-pyrrole]-2,5'(1H,1'H)-diones using NiFe2O4 NPs.
Me
CO2
N
NH2
NH
O
Me
+
CO2
CO2
NPs
NiFe2O4
EtOH
+
O
HN
2
N
O
H
Me
O
Scheme 2 The model reaction for the preparation of 4d.
* Correspondent. E-mail: safaei@kashanu.ac.ir

398 JOURNAL OF CHEMICAL RESEARCH 2016
Table 1 Optimisation of reaction conditions using different catalystsa
Experimental
The products were isolated and characterised by physical and spectral
data. 1H NMR and 13C NMR spectra were recorded on Bruker
Avance-400 MHz spectrometers in the presence of tetramethylsilane
as internal standard. The IR spectra were recorded on FTIR Magna
550 apparatus using with KBr plates. Melting points were determined
on Electro thermal 9200, and are not corrected. The elemental
analyses (C, H, N) were obtained from a Carlo ERBA Model EA
1108 analyser. Powder X-ray diffraction (XRD) was carried out on a
Philips diffractometer of X’pert Company with monochromatised Cu
Kα radiation (λ = 1.5406 Å). Microscopic morphology of products was
visualised by SEM (MIRA 3 TESCAN).
Entry Solvent (reflux) Catalyst/mol%
Time/h
14
10
6
Yield/%b
trace
28
1
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
H2O
----------
2
piperidine (2)
ZnCl2 (3)
3
37
4
NiCl2 (4)
5
45
5
NiO (3)
4
55
6
FeCl3 (4)
4
40
7
Fe3O4 (3)
4
51
8
NiFe2O4 NPs (0.3)
NiFe2O4 NPs (0.3)
NiFe2O4 NPs (0.3)
NiFe2O4 NPs (0.2)
NiFe2O4 NPs (0.3)
NiFe2O4 NPs (0.4)
1.5
1.5
1.5
1.5
1.5
1.5
60
Preparation of NiFe2O4 nanoparticles
9
DMF
CH3CN
EtOH
EtOH
74
The NiFe2O4 nanoparticles were prepared according to the procedure
reported in the literature.16 3 M solution of sodium hydroxide (as the
precipitating agent) was slowly mixed with salt solutions of 0.4 M
ferric chloride (FeCl3. 6H2O) and 0.2 M nickel chloride (NiCl2·6H2O).
The pH of the solution was constantly monitored as the NaOH solution
was added dropwise. The reactants were constantly stirred using a
magnetic stirrer until a pH level of >12 was achieved. A specified
amount of oleic acid (2–3 drops for total reacting solution of 75 mL)
was added to the solution as the surfactant. The liquid precipitate
was then brought to a reaction temperature of 80 ºC and stirred for 40
min. The product was cooled to room temperature and then washed
twice with distilled water and ethanol to remove unwanted impurities
and the excess surfactant from the prepared sample. The sample was
centrifuged for 15 min at 2000 rpm and then dried overnight at above
80 ºC. The acquired substance was then grinded into a fine powder and
then annealed for 10 h at 600 ºC.
10
11
12
13
81
91
93
EtOH
93
a4-methylaniline (4 mmol), dimethyl acetylenedicarboxylate (2 mmol) and isatin
(2 mmol).
bIsolated yield.
The above results obviously show the present catalytic
procedure is extendable to a wide variety of substrates to
construct a diversity-oriented library of spiro[indole-3,2'-
pyrrole]-2,5'(1H,1'H)-diones (Table 2). An important feature
of this method is that both electron-releasing and withdrawing
groups give excellent yields.
The recoverability of the nano-NiFe2O4 catalyst was
examined for the synthesis of product 4d and it was found that
product yields decreased to a small extent on each reuse (run
1, 93%; run 2, 93%; run 3, 92%; run 4, 92%; run 5, 91%). In
the recycling procedure of NiFe2O4 NPs, after completion of the
reaction, 10 mL ethanol was added and magnet was introduced
into the mixture in the form of a magnetic stirrer bar and
catalyst was separated magnetically.
Synthesis of spiro[indole-3,2'-pyrrole]-2,5'(1H,1'H)-diones (4a–h);
general procedure
A
solution of arylamine (4 mmol), and isatin (2.0 mmol),
acetylenedicarboxylate (2.0 mmol) and NiFe2O4 NPs (0.3 mol%)
as catalyst in 10 mL ethanol was refluxed for about 90 min. After
completion of the reaction, 10 mL ethanol added and magnet was
introduced into the mixture in the form of a magnetic stirrer bar and
catalyst was separated magnetically. The precipitated solid was filtered
and washed with ethanol to give the pure product.
Methyl
4'-(3-nitroanilino)-1'-(3-nitrophenyl)-2,5'-dioxo-1,1',2,5'-
tetrahydrospiro[indole-3,2'-pyrrole]-3'-carboxylate (4a): Yellow
solid; m.p. 236–238 °C, (lit.11 238–240 °C); IR νmax/cm–1 (KBr): 3345,
3277, 3115, 2949, 1727, 1693, 1652, 1615, 1526, 1482, 1265; 1H NMR
(400 MHz, DMSO-d6): δ 3.31 (3H, s, OCH3), 6.84 (d, J = 7.8 Hz, 1H,
ArH), 6.95 (t, J = 8 Hz, 1H, ArH), 7.12–7.15 (m, 2H, ArH), 7.29 (t, J =
8 Hz, 1 H, ArH), 7.42 (s, 1H, ArH), 7.50–7.53 (m, 3 H, ArH), 7.97–8.05
(m, 2H, ArH), 8.15 (s, 1, ArH), 9.20 (s, 1H, NH), 10.90 (s, 1H, NH)
ppm; 13C NMR (100 MHz, DMSO-d6): δ 51.2, 70.9, 109.8, 110.5, 115.8,
117.9, 120.6, 122.5, 124.5, 124.8, 127.8, 129.2, 130.6, 130.7, 132.5,
136.0, 140.5, 141.0, 143.2, 147.6, 147.9, 161.7, 165.5, 173.5 ppm; Anal.
In conclusion, we have developed a straightforward and
efficient approach to synthesis of spiro[indole-3,2'-pyrrole]-
2,5'(1H,1'H)-diones by the multi-component condensation
reaction of arylamines, acetylenedicarboxylates and isatins in
the presence of NiFe2O4 nanoparticles under reflux conditions in
ethanol. The method offers several advantages including rapid
assembly of heterocyclic molecules, cleaner reaction profiles,
high yields, shorter reaction times, simple experimental,
reusability of the catalyst and little catalyst loading.
Table 2 Synthesis of spiro[indole-3,2'-pyrrole]-2,5'(1H,1'H)-diones (4 a–h)a
Entry
Ar
R
Product
4a
4b
4c
4d
4e
4f
4g
4h
Time/min
100
90
Yield/%b
89
95
94
93
92
94
91
M.p./ °C Found
236–238
276–278
256–258
229–231
228–230
248–250
249–251
256–258
M.p./°C ref Reported
238–240 11
–
R'
H
NO2
Cl
H
H
Cl
CH3
Cl
1
2
3
4
5
6
7
8
3-NO2C6H4
4-CH3C6H4
4-OCH3C6H4
4-CH3C6H4
4-CH3C6H4
4-CH3C6H4
4-CH3C6H4
4-CH3C6H4
CH3
CH3
CH3
CH3
Et
Et
CH3
CH3
90
90
93
93
96
90
254–256 11
229–231 11
–
247–249 11
249–250 11
258–260 11
94
aArylamines, acetylenedicarboxylates and isatins with NiFe2O4 NPs (0.3 mol%).
bIsolated yield.

JOURNAL OF CHEMICAL RESEARCH 2016 399
calcd for C25H17N5O8: C, 58.26; H, 3.32; N, 13.59; found: C, 58.32; H,
3.38; N, 13.68%.
Methyl 5-methyl-4’-(4-methylanilino)-1’-(4-methylphenyl)-2,5’-dioxo-
1,1’,2,5’-tetrahydro spiro[indole-3,2’-pyrrole]-3’-carboxylate (4g):
Yellow solid, m.p. 249–251 ºC; (lit.11 249–250 ºC); IR νmax/cm–1 (KBr):
3361, 3273, 3023, 2950, 2912, 1672, 1632, 1545, 1515, 1495, 1432, 1391,
Methyl
4’-(4-methylanilino)-1’-(4-methylphenyl)-5-nitro-2,5’-dioxo-
1,1’,2,5’-tetrahydrospiro
[indole-3,2’-pyrrole]-3’-carboxylate
(4b):
Yellow solid; m.p. 276–278 °C; IR νmax/cm–1 (KBr): 3325, 3257,
1350, 1290, 1252, 1233, 1197, 1108; H NMR (400 MHz, DMSO-d6):
1
1
2947, 1722, 1691, 1650, 1612, 1523, 1480, 1350; H NMR (400 MHz,
δ 2.21–2.24 (6H, 2 CH3), 2.28 (s, 3H, CH3), 3.28 (s, 3H, OCH3), 6.64 (d,
J = 7.6 Hz, 1H, ArH), 6.87 (d, J = 7.6 Hz, 2H, ArH), 6.98 (d, J = 7.8 Hz,
1H, ArH), 7.03 (d, J = 7.8 Hz, 2H, ArH), 7.11–7.07 (m, 4H, ArH), 7.14 (s,
1H, ArH), 9.06 (s, 1H, NH), 10.64 (s, 1H, NH) ppm; 13C NMR (100 MHz,
DMSO-d6): δ 20.4, 20.5, 20.7, 50.7, 71.0, 105.9, 109.8, 122.2, 124.7, 125.6,
126.8, 128.4, 129.5, 130.3, 131.1, 132.4, 132.9, 137.2, 137.4, 140.4, 141.6,
162.3, 165.5, 174.1 ppm; Anal. calcd for C28H25N3O4: C, 71.93; H, 5.39; N,
8.99; found: C, 72.04; H, 5.48; N, 8.90%.
DMSO-d6): δ 2.24 (s, 3H, CH3), 2.28 (s, 3H, CH3), 3.28 (3H, s, OCH3),
6.74 (d, J = 7.8 Hz, 1H, ArH), 6.95 (d, J = 8 Hz, 2H, ArH), 7.02–7.20 (m,
6H, ArH), 7.56 (d, J = 8 Hz, 1H, ArH), 7.96 (s, 1H, ArH), 9.21 (s, 1H,
NH), 10.85 (s, 1H, NH) ppm; 13C NMR (100 MHz, DMSO-d6): δ 20.4,
20.5, 50.7, 70.6, 104.7, 111.4, 122.3, 124.6, 126.3, 126.9, 128.5, 129.5,
129.6, 129.7, 132.3, 133.2, 137.1, 137.5, 142.1, 142.3, 162.4, 165.2, 174.2
ppm; Anal. calcd for C27H22N4O6: C, 65.05; H, 4.45; N, 11.24; found: C,
65.15; H, 4.51; N, 11.32%.
Methyl
5-chloro-4’-(4-methylanilino)-1’-(4-methylphenyl)-2,5’-
Methyl 5-chloro-4’-(4-methoxyanilino)-1’-(4-methoxyphenyl)-2,5’-
dioxo-1,1’,2,5’-tetrahydrospiro[indole-3,2’-pyrrole]-3’-carboxylate
(4c): Yellow solid; m.p. 256–258 °C, (lit.11 254–256 °C); IR νmax/cm–1
(KBr): 3331, 3250, 2953, 2835, 1730, 1624, 1510, 1475, 1360, 1302;
1H NMR (400 MHz, DMSO-d6): δ 3.26 (s, 3H, OCH3), 3.67 (s, 3H,
OCH3), 3.74 (s, 3H, OCH3), 6.74 (d, J = 7.8 Hz, 2H, ArH), 6.92–7.05
(m, 4H, ArH), 7.14 (m, 2H, ArH), 7.25 (d, J = 8 Hz, 2H, ArH), 7.56
(d, J = 7.6 Hz, 1H, ArH), 9.06 (s, 1H, NH), 10.83 (s, 1H, NH) ppm;
13C NMR (100 MHz, DMSO-d6): δ 50.7, 55.1, 55.2, 70.7, 103.2, 111.3,
113.1, 114.2, 124.3, 124.6, 126.2, 127.1, 128.3, 128.5, 129.7, 132.5,
142.2, 142.6, 156.2, 158.7, 162.3, 165.3, 174.2 ppm; Anal. calcd for
C27H22ClN3O6: C, 62.37; H, 4.26; N, 8.08; found: C, 62.45; H, 4.34; N,
8.02%.
dioxo-1,1’,2,5’-tetrahydro spiro[indole-3,2’-pyrrole]-3’-carboxylate
(4h): Yellow solid; m.p. 256–258 ºC; (lit.11 258–260 ºC); IR νmax/cm–1
(KBr): 3343, 3274, 3032, 2950, 2918, 1703, 1544, 1512, 1475, 1440,
1
1354, 1292, 1254, 1195; H NMR (400 MHz, DMSO-d6): δ 2.24 (s,
3H, CH3), 2.29 (s, 3H, CH3), 3.26 (s, 3H, OCH3), 6.76 (d, J = 7.8 Hz,
1H, ArH), 6.93 (d, J = 8 Hz, 2H, ArH), 7.08–7.15 (m, 6H, ArH), 7.25
(m, 2H, ArH), 9.11 (s, 1H, NH), 10.87 (s, 1H, NH) ppm; 13C NMR (100
MHz, DMSO-d6): δ 20.4, 20.5, 50.7, 70.8, 104.8, 111.4, 122.4, 124.7,
126.9, 128.0, 128.4, 129.6, 129.7, 129.8, 132.2, 133.1, 137.0, 137.6, 142.1,
142.2, 162.3, 165.3, 174.1 ppm; Anal. calcd for C27H22ClN3O4: C, 66.46;
H, 4.54; N, 8.61; found: C, 66.35; H, 4.50; N, 8.50%.
The authors acknowledge a reviewer who provided helpful
insights. The authors gratefully acknowledge the financial
support of this work by the Research Affairs Office of the Qom
Branch, Islamic Azad University, I. R. Iran. Also authors are
grateful to Dr. Hossein Shahbazi-Alavi for their help.
Methyl 4’-(4-methylanilino)-1’-(4-methylphenyl)-2,5’-dioxo-1,1’,2,5’-
tetrahydrospiro[indole-3,2’-pyrrole]-3’-carboxylate
(4d):
Yellow
solid; m.p. 229–231 °C (lit.11 229–231 °C); IR νmax/cm–1 (KBr): 3294,
1
3192, 3091, 2943, 1712, 1674, 1623, 1512, 1474; H NMR (400 MHz,
DMSO-d6): δ 2.21 (s, 3H, CH3), 2.28 (s, 3H, CH3), 3.22 (s, 3H, OCH3),
6.86 (d, J = 7.8 Hz, 1H, ArH), 6.92 (d, J = 8 Hz, 2H, ArH), 7.05 (t,
J = 7.8 Hz, 1H), 7.08–7.15 (m, 6 H, ArH), 7.18 (t, J = 8 Hz, 1H, ArH),
7.35 (d, J = 7.8 Hz, 1 H, ArH), 9.08 (s, 1H, NH), 10.75 (s, 1H, NH)
ppm; 13C NMR (100 MHz, DMSO-d6): δ 20.4, 20.5, 50.6, 71.0, 105.7,
110.1, 122.0, 122.1, 124.3, 125.7, 127.0, 128.5, 129.5, 129.9, 132.3,
132.9, 137.3, 137.5, 141.7, 143.2, 162.2, 165.6, 174.1 ppm; Anal. calcd
for C27H23N3O4: C, 71.51; H, 5.11; N, 9.27; found: C, 71.55; H, 5.02; N,
9.38%.
Electronic Supplementary Information
The spectral data are available through:
stl.publisher.ingentaconnect.com/content/stl/jcr/supp-data
Received 26 February 2016; accepted 16 April 2016
Paper 1603945 doi: 10.3184/174751916X14640003438169
Published online: 13 June 2016
Ethyl 4’-(4-methylanilino)-1’-(4-methylphenyl)-2,5’-dioxo-1,1’,2,5’-
tetrahydrospiro[indole-3,2’-pyrrole]-3’-carboxylate (4e): Yellow solid;
m.p. 228–230 °C; IR νmax/cm–1 (KBr): 3335, 3283, 3032, 2914, 1700,
1544, 1512, 1473, 1442, 1376, 1346, 1293, 1252; 1H NMR (400 MHz,
DMSO-d6): δ 0.97 (t, J = 7.2 Hz, 3H, CH3); 2.19 (s, 3 H, CH3), 2.24
(s, 3 H, CH3), 3.92–4.02 (m, 2H, OCH2), 6.71 (d, J = 8 Hz, 1 H, ArH),
6.84 (d, J = 8.4 Hz, 2H, ArH), 7.06–7.10 (m, 6H, ArH), 7.17–7.50 (m,
3H), 9.08 (s, 1H, NH), 10.80 (s, 1H, NH) ppm; 13C NMR (100 MHz,
DMSO-d6): δ 13.1, 20.4, 20.5, 59.7, 70.9, 105.2, 111.3, 121.9, 124.8,
126.2, 126.7, 128.2, 128.4, 129.6, 129.7, 132.4, 132.7, 137.1, 137.6, 142.1,
142.2, 161.7, 165.4, 174.1 ppm; Anal. calcd for C28H25N3O4: C, 71.93; H,
5.39; N, 8.99; found: C, 71.99; H, 5.48; N, 8.85%.
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3
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1,1’,2,5’-tetrahydrospiro [indole-3,2’-pyrrole]-3’-carboxylate (4f):
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3332, 3281, 3032, 2913, 1703, 1542, 1517, 1477, 1441, 1376, 1346,
1293, 1252, 854, 812, 774; 1H NMR (400 MHz, DMSO-d6): δ 0.66 (t,
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132.3, 132.8, 137.0, 137.6, 142.1, 142.3, 161.8, 165.5, 174.2 ppm; Anal.
calcd for C28H24ClN3O4: C, 67.00; H, 4.82; N, 8.37; found: C, 67.09; H,
4.73; N, 8.24%.
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