A mild and green chemistry approach for the synthesis of symmetrical spirooxindole derivatives

Article abstract of DOI:10.1007/s13738-012-0187-z

A simple and eco-friendly synthesis of the biologically important spirooxindole scaffold was done by the reaction of isatin with activated pyrazolones in the presence of a catalytic amount of p-toluenesulfonic acid in water at room temperature. A variety of symmetrical spirooxindole derivatives were obtained with excellent yields within short reaction time. This method is of great value because of its environmentally benign character, high yield, and easy handling.

Full text of DOI:10.1007/s13738-012-0187-z

J IRAN CHEM SOC (2013) 10:521–525
DOI 10.1007/s13738-012-0187-z
ORIGINAL PAPER
A mild and green chemistry approach for the synthesis
of symmetrical spirooxindole derivatives
•
Abbas Rahmati Ali Hossein Rezayan
•
•
Meysam Alizadeh Ali Nikbakht
Received: 4 April 2012 / Accepted: 8 November 2012 / Published online: 23 November 2012
Ó Iranian Chemical Society 2012
Abstract A simple and eco-friendly synthesis of the
biologically important spirooxindole scaffold was done by
the reaction of isatin with activated pyrazolones in the
presence of a catalytic amount of p-toluenesulfonic acid in
water at room temperature. A variety of symmetrical spi-
rooxindole derivatives were obtained with excellent yields
within short reaction time. This method is of great value
because of its environmentally benign character, high
yield, and easy handling.
Spiro compounds have been the focus of considerable
attention due to their abundance in numerous natural sub-
stances as well as their extensive applications in biology
and pharmacology [5]. Therefore, in recent years, great
efforts have been devoted to the synthesis of these struc-
tural frameworks [6]. Compounds with indole moiety
exhibit a wide range of biological activities [7, 8]. The
spirooxindole core is featured in a number of natural
alkaloids as well as medicinally relevant compounds [9–
13]. In addition, it has been reported that participation of
the indole’s 3-carbon atom in the formation of spiroindo-
line derivatives with heterocycles highly enhances the
biological activity of the compound [14, 15]. Recently,
several methods for the synthesis of spirooxindole deriva-
tives via multi-component reactions in the presence of
different catalysts have been reported in the literature
[16–26].
Keywords Symmetrical spirooxindole Á Isatin Á
Green chemistry approach
Introduction
Multi-component reactions are synthetically important
processes in which three or more different starting mate-
rials react to give a final product in a one-pot procedure [1].
Such reactions are important tools in modern organic
synthesis to generate chemical libraries for screening pur-
poses because of their productivity, simple procedures and
convergence [2]. This methodology allows molecular
complex and diverse molecules to be created by the facile
formation of several new covalent bonds in one-pot
transformation [3, 4].
At the commencement of the new century, a shift in
emphasis in chemistry is apparent with the desire to develop
more environmental friendly routes to a myriad of materials.
This shift is most apparent in the growth of green chemistry
[27–29]. Green chemistry approaches not only hold out
significant potential for reduction of by-products, a reduc-
tion in the waste produced and lowering of energy costs, but
also in the development of new methodologies towards
previously unobtainable materials, using existing technolo-
gies [30]. The use of water as a solvent in organic chemistry
was rediscovered in the 1980s by Breslow [31], who showed
that hydrophobic effects can strongly enhance the rate of
organic reactions. The unique properties of water in aqueous
medium like high dielectric constant and cohesive energy
density showed an extraordinary effect on reaction rates.
Moreover, its cost-effectiveness, high abundance, non-
inflammability and non-toxic nature increased its applica-
bility [32–34]. As a result, development of organic reactions
A. Rahmati (&) Á M. Alizadeh Á A. Nikbakht
Department of Chemistry, University of Isfahan,
P.O. Box 81746-73441, Isfahan, Iran
e-mail: a.rahmati@sci.ui.ac.ir
A. H. Rezayan
Department of Life Science Engineering, Faculty of New
Science and Technology, University of Tehran, Tehran, Iran
123

522
J IRAN CHEM SOC (2013) 10:521–525
Scheme 1 Synthesis of
symmetrical spirooxindole
derivatives 3a–l
Me
NH
X
Me
O
O
Me
X
N
O
H2O, PTSA
r.t.
N
R
+
O
2
N
N
N
N
N
O
H
1
2
X = Cl, Br, Me, OMe, NO2
O
, 79-89 %
3a-3l
R
R
R = H or
S
NH2
O
in water has become highly desirable in recent years to meet
environmental considerations.
white powder: 0.51 g, yield 79 %; M.P. [350; IR (KBr)
(mmax/cm-1): 3,503, 3,217, 1,705, 1,616, 1,559, 1,493, 1,328,
1,161; H NMR (400 MHz, DMSO-d6): dH 1.94 (6H, bs,
1
Therefore, design and development of facile and green
synthetic methods for new biologically active compounds
is the endless task for chemists. Hence, in continuing of our
research on the development of synthetic methods in het-
erocyclic chemistry and green chemistry methods [35–38],
we herein disclose a valid and efficient procedure for the
synthesis of new symmetrical spirooxindole derivatives
from the reaction of activated pyrazolones 1 with isatin 2 in
the presence of a catalytic amount of p-toluenesulfonic acid
(p-TsOH) in water at room temperature (Scheme 1).
2CH3), 3.67 (3H, s, OCH3), 6.81–7.88 (11H, m, ArH and
2(SO2NH2)), 10.70 (1H, s, NH) (ppm). 13C NMR (100 MHz,
DMSO-d6): dC 13.32, 50.07, 55.86 (OMe), 110.50, 110.55,
112.90, 113.92, 117.81, 118.60, 118.75, 127.37, 134.09,
135.20, 140.14, 149.51, 155.21, 175.82 (C=O) (ppm); MS,
m/z (%): 647 (M?, 8). Anal. Calcd for C29H25N7O7S2: C,
53.78; H, 3.89; N, 15.14; S, 9.90; Found: C, 53.53; H, 3.98;
N, 15.21; S, 10.02.
Compound 3a white powder: 0.37 g, yield 81 %;
M.P. [350; IR (KBr) (mmax/cm-1): 3,447, 3,150, 1,706,
1
1,616, 1,497, 1,305; H NMR (400 MHz, DMSO-d6): dH
1.98 (6H, bs, 2CH3), 6.83–7.92 (13H, m, ArH), 10.96 (1H,
s, NH) (ppm); MS, m/z (%): 459 (M?, 10); Anal. calcd for
C28H21N5O2: C, 73.19; H, 4.61; N, 15.24; Found: C, 73.16;
H, 4.70; N, 15.12.
Experimental section
General
Melting points were measured on an Electrothermal 9100
apparatus and are uncorrected. IR spectra were recorded on
a Shimadzu IR-470 spectrometer. 1H spectra were recorded
on a BRUKER DRX-400 AVANCE spectrometer at
400 MHz. NMR spectra were obtained on solution in
DMSO using TMS as internal standard. The chemicals
used in this work were purchased from Merck, Fluka and
Sigma-Aldrich Chemical Companies.
Compound 3b white powder: 0.39 g, yield 84 %;
M.P. [350; IR (KBr) (mmax/cm-1): 3,442, 3,155, 1,708,
1,612, 1,489, 1,302; H NMR (400 MHz, DMSO-d6): dH
1
2.07 (6H, bs, 2CH3), 2.20 (3H, s, CH3), 6.88–7.88 (13H, m,
ArH), 10.81 (1H, s, NH) (ppm); 13C NMR (100 MHz,
DMSO-d6): dC 11.83, 20.06 (Me), 50.69, 102.25, 110.43,
116.51, 122.83, 123.14, 127.15, 129.03, 129.56, 131.33,
135.42, 138.90, 141.21, 147.94, 175.44 (C=O) (ppm); MS,
m/z (%): 473 (M?, 4); Anal. calcd for C29H23N5O2: C,
73.56; H, 4.90; N, 14.79; Found: C, 73.38; H, 5.00; N,
14.71.
Typical procedure for the preparation of 3i
4-(4,5-Dihydro-3-methyl-5-oxopyrazol-1-yl)benzenesul-
fonamide (0.51 g, 2 mmol), p-OMe-isatin (0.18 g, 1 mmol)
and p-TsOH (10 mol%) were successively added to a screw-
capped vial containing a magnetic stirring bar and water
(10 mL). Then reaction mixture stirred at room temperature
for 1 h. The reaction mixture was monitored by TLC method.
After completion of the reaction, the precipitate product was
filtered and washed with EtOH (10 mL) and dried at
room temperature. The final product 3i was obtained as a
Compound 3c white powder: 0.39 g, yield 82 %; M.P.
[350; IR (KBr) (mmax/cm-1): 3,449, 1,701, 1,610, 1,491,
1,307; H NMR (400 MHz, DMSO-d6): dH 1.99 (6H, bs,
2CH3), 3.70 (3H, s, OCH3), 6.80–7.84 (13H, m, ArH), 10.72
(1H, s, NH) (ppm); 13C NMR (100 MHz, DMSO-d6): dC
12.02, 50.83, 54.11 (OMe), 103.71, 110.43, 113.79, 122.35,
123.77, 126.99, 128.95, 129.73, 133.16, 139.51, 142.15,
147.31, 156.25, 176.08 (C=O) (ppm); MS, m/z (%): 489(M?,
1
123

J IRAN CHEM SOC (2013) 10:521–525
523
9); Anal. calcd for C29H23N5O3: C, 71,15; H, 4.74; N, 14.31;
Found: C, 70.99; H, 4.62; N, 14.29.
(6H, bs, 2CH3), 6.95–8.16 (15H, m, ArH and 2(SO2NH2)),
10.96 (1H, s, NH) (ppm). Anal. calcd for C28H22ClN7O6S2:
C, 51.57; H, 3.40; N, 15.04; S, 9.83; Found: C, 51.65; H,
3.47; N, 14.98; S, 10.00.
Compound 3d white powder: 0.41 g, yield 88 %;
M.P. [350; IR (KBr) (mmax/cm-1): 3,445, 3,141, 1,705,
1,619, 1,575, 1,498, 1,472, 1,308, 750, 682. MS, m/z (%):
495 (M??2, 5), 493 (M?, 14); 1H NMR (400 MHz,
DMSO-d6): dH 2.04 (6H, bs, 2CH3), 7.53–8.12 (13H, m,
ArH), 10.81 (1H, s, NH) (ppm). Anal. calcd for
C28H20ClN5O2: C, 68.08; H, 4.08; N, 14.18; Found: C,
68.23; H, 4.11; N, 14.25.
Compound 3k white powder: 0.59 g, yield 85 %; M.P.
[350; IR (KBr) (mmax/cm-1): 3,566, 3,241, 1,714, 1,624,
1,586, 1,497, 1,474, 1,368, 1,334, 1,160, 541; MS, m/z (%):
695 (M??2, 9), 697 (M?, 9); 1H NMR (400 MHz, DMSO-
d6): dH 2.03 (6H, bs, 2CH3), 6.83–7.88 (15H, m, ArH and
2(SO2NH2)), 10.86 (1H, s, NH) (ppm); Anal. calcd for
C28H22BrN7O6S2: C, 48.28; H, 3.18; N, 14.08; S, 9.21;
Found: C, 48.39; H, 3.20; N, 14.01; S, 9.38.
Compound 3e white powder: 0.47 g, yield 88 %; M.P.
[mmax/cm-1): 3,447, 3,142, 1,704, 1,618, 1,577, 1,497,
1
1,309, 757, 690; H NMR (400 MHz, DMSO-d6): dH 2.01
Compound 3l white powder: 0.57 g, yield 86 %; M.P.
[350; IR (KBr) (mmax/cm-1): 3,447, 3,157, 1,731, 1,624,
(6H, bs, 2CH3), 7.31–8.80 (13H, m, ArH), 10.86 (1H, s,
NH) (ppm). MS, m/z (%): 539 (M??2, 7), 537 (M?, 7);
Anal. calcd for C28H20BrN5O2: C, 62.46; H, 3.74; N,
13.01; Found: C, 62.30; H, 3.80; N, 13.13.
1
1,497, 1,337, 1,161; MS, m/z (%): 662 (M?, 10). H NMR
(400 MHz, DMSO-d6): dH 2.09 (6H, bs, 2CH3), 7.03–8.32
(15H, m, ArH and 2(SO2NH2)), 11.35 (1H, s, NH) (ppm);
Anal. calcd for C28H22N8O8S2: C, 50.75; H, 3.35; N, 16.91;
S, 9.68; Found: C, 50.89; H, 3.31; N, 17.01; S, 9.52.
Compound 3f white powder: 0.45 g, yield 89 %; M.P.
[350; IR (KBr) (mmax/cm-1): 3,447, 3,157, 1,712, 1,626,
1,497, 1,459, 1,402, 1,338, 693; 1H NMR (400 MHz,
DMSO-d6): dH 2.07 (6H, bs, 2CH3), 7.35–8.32 (13H, m,
ArH), 11.35 (1H, s, NH) (ppm); MS, m/z (%): 504 (M?,
18); Anal. calcd for C28H20N6O4: C, 66.66; H, 4.00; N,
16.66; Found: C, 66.40; H, 3.97; N, 16.72.
Results and discussion
In this communication, we wish to highlight our findings
on the p-TsOH acid catalysed reaction of activated pyraz-
olones with isatin. The reaction conditions are mild and
carried out in water as a green solvent. In a typical reaction,
the reaction of 2 mol of 3-methyl-1-phenyl-1H-pyrazol-
5(4H)-one 1a with indoline-2,3-dione 2a in the presence of
p-TsOH acid (10 mol%) in water at room temperature
resulted in the formation of symmetrical spirooxindole
derivatives 3a in 89 % yield within 1 h. In view of the
emerging importance of the catalytic process to replace the
stoichiometric reagents we studied the optimized reaction
conditions with 10 mol% of the catalyst.
Compound 3g white powder: 0.50 g, yield 81 %; M.P.
[350; IR (KBr) (mmax/cm-1): 3,526, 3,064, 3,064, 1,709,
1,619, 1,561, 1,497, 1,325, 1,159; 1H NMR (400 MHz,
DMSO-d6): dH 1.96 (6H, bs, 2CH3), 6.81–7.97 (16H, m,
ArH, 2SO2NH2), 10.71 (1H, s, NH) (ppm). MS, m/z (%):
617 (M?, 12). Anal. calcd for C28H23N7O6S2: C, 54.45; H,
3.75; N, 15.87; S, 10.38; Found: C, 54.06; H, 3.90; N,
16.00; S, 10.50.
Compound 3h white powder: 0.50 g, yield 80 %;
M.P. [350; IR (KBr) (mmax/cm-1): 3,528, 3,212, 1,709,
1,620, 1,591, 1,561, 1,494, 1,328, 1,161. MS, m/z (%): 631
(M?, 7). 1H NMR (400 MHz, DMSO-d6): dH 1.92 (6H, bs,
2CH3), 2.24 (3H, s, CH3), 6.79–7.97 (15H, m, ArH
and 2(SO2NH2)), 10.93 (1H, s, NH) (ppm). 13C NMR
(100 MHz, DMSO-d6): dC 13.01, 19.21 (Me), 50.49,
106.32, 114.92, 121.80, 125.41, 127.37, 128.32, 131.98,
134.11, 134.82, 135.20, 140.14, 142.86, 149.51, 175.29
(C=O) (ppm); Anal. calcd for C29H25N7O6S2: C, 55.14; H,
3.99; N, 15.52; S, 10.15; Found: C, 54.98; H, 3.94; N,
16.02; S, 10.29.
To further expand the scope of the suggested procedure,
a wide range of isatins 2 with electron donating and elec-
tron withdrawing groups were used successfully and effi-
ciently to react with pyrazolones 1 under the same reaction
conditions to give the corresponding substituted symmet-
rical spirooxindole derivatives 3a–f. Furthermore, we
extended our studies to the use of 4-(4,5-dihydro-3-methyl-
5-oxopyrazol-1-yl)benzenesulfonamide 2b instead of pyr-
azolone with electron donating and electron withdrawing
groups on isatin 1. As indicated in Scheme 2, products
3 g–l were obtained in high yields.
1
Compound 3j white powder: 0.55 g, yield 84 %; M.P.
[350; IR (KBr) (mmax/cm-1): 3,460, 1,716, 1,620, 1,497,
1,401, 1,329, 1,160, 609; MS, m/z (%): 653 (M??2, 12),
All the products are characterized by their IR, mass, H
NMR spectra and elemental analysis. 13C NMR because of
low solubility of products could not obtained for all of
products. The mass spectra of these compounds displayed
1
651 (M?, 4); H NMR (400 MHz, DMSO-d6): dH 2.07
123

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J IRAN CHEM SOC (2013) 10:521–525
NH
NH
NH
NH
Cl
Me
Me
Me
MeO
Me
O
N
O
N
O
N
O
Me
Me
Me
Me
Me
N
N
N
N
N
N
N
N
N
N
N
N
N
O
O
O
O
3a
3c
3b
3d
NH
NH
Me
NH
NH
O
O
N
Br
Me
O2N
Me
Me
Me
Me
Me
O
N
O
Me
Me
N
N
N
N
N
N
N
N
N
N
N
O
O
N
N
N
O
O
3h
3g
3e
3f
O S
O
O S
O
O S
O
O S
O
NH2
NH2
NH2
NH2
NH
NH
NH
NH
Br
Me
Cl
Me
O2N
MeO
Me
O
N
O
O
N
O
Me
Me
Me
Me
Me
N
N
N
N
N
N
N
N
N
N
N
N
N
N
O
O
O
O
O S
O
O S O
NH2
O S
O
O S O
O S
O
O S
O
O S
O
O S
O
NH2
NH2
NH2
NH2
NH2
NH2
NH2
3j
3i
3k
3l
3j 3k 3l
85
3a
3g
81 80
Product
3b
3e
3h 3i
79 84
3c
82
3d
3f
Yeild (%) 81 84
86
88 88 89
Scheme 2 Synthesis of symmetrical spirooxindoles via the reaction of isatin with activated pyrazolones in the presence of p-TsOH in water
1
molecular ion peaks at the appropriate m/z values. The H
NMR spectrum of 3a consisted of a singlet for two CH3
groups at d = 1.95, a multiplet for the 14 aromatic ring
protons (d = 6.81–7.88) and at d = 11.70, a singlet for the
NH proton of isatin ring. The elemental analysis data con-
firmed the ratio of original elements in molecular formula.
A plausible mechanism pathway for the formation of
spirooxindole derivatives 3a–l is shown in Scheme 3. The
first step involves the formation of intermediate 4 from
condensation reaction between 3-methyl-1-phenyl-pyr-
azolone 1 with isatin 2. Then, the second molecule of
3-methyl-1-phenyl-pyrazolone 1 attacked via Michael
addition to intermediate 4 to give the intermediate 6, which
followed by cycloaddition and dehydration to form the
desired product 3a–l (Scheme 3).
Conclusion
In conclusion, we have successfully developed a simple
and green method for the synthesis of symmetrical spiro-
oxindoles through the reaction of isatin with 2 mol of
activated pyrazolones in the presence of a catalytic amount
of p-TsOH in aqueous media at room temperature. The
method offered several advantages such as high yields,
broader substrate scope, a safe, cheap, simple workup and
environmentally benign procedure, which makes the
introduced procedure a useful and attractive process for the
synthesis of these important compounds. We hope that this
approach may be of value to others seeking novel synthetic
fragments with unique properties for medicinal chemistry
programs.
123

J IRAN CHEM SOC (2013) 10:521–525
525
X
NH
O
O
H
Me
Me
X
H
-H2O
+
H
O
N
O
N
N
R
N
O
N
R
H
1
2
4
X
NH
X
NH
NH
X
NH
O
X
Me
Me
Me
Me
N
O
Me
N
H
Me
O
N
O
Me
Me
N
N
N
N
N
N
-H2O
O
H
O
H
O
+
O
N
N
R
N
N
N
N
N
O
HO
OH
R
R
R
7
R
R
5
3a-3l
R
6
R
Scheme 3 Proposed mechanism for the synthesis of symmetrical spirooxindole derivatives 3a–l
Acknowledgments We gratefully acknowledge the financial
support from the Research Council of the University of Isfahan.
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