Synthesis and Biological Activities of Some Novel Spiro Heterocyclic Pyrrolizidine Derivatives of 11H-indeno[1,2-b]quinoxaline through 1,3-Dipolar Cycloaddition

Article abstract of DOI:10.14233/ajchem.2020.22630

The synthesis of spiropyrrolidines by the Knoevenagel condensation has been reported as highly bioactive natural and synthetic organic products. The synthesis was initiated by Knoevenagel condensation of indole-2-one with an appropriate benzaldehyde in pr

Full text of DOI:10.14233/ajchem.2020.22630

Asian Journal of Chemistry; Vol. 32, No. 5 (2020), 1255-1258
A
SIAN
J
OURNAL OF HEMISTRY
C
https://doi.org/10.14233/ajchem.2020.22630
Synthesis and Biological Activities of Some Novel Spiro Heterocyclic Pyrrolizidine
Derivatives of 11H-indeno[1,2-b]quinoxaline through 1,3-Dipolar Cycloaddition
1
2,*
1
3
NAKUL KUMAR , CHHAGAN LAL , BIJENDRA SINGH and ANGIK K. PATEL
1School of Chemical Science, Central University of Gujarat, Gandhinagar-382030, India
2Department of Chemistry, Harcourt Butler Technical University, Kanpur-208002, India
3Department of Chemistry, Mahisagar Science College, Lunawada-389230, India
*Corresponding author: E-mail: c.lal9940@gmail.com
Received: 10 January 2020;
Accepted: 20 March 2020;
Published online: 29 April 2020;
AJC-19866
The synthesis of spiropyrrolidines by the Knoevenagel condensation has been reported as highly bioactive natural and synthetic organic
products. The synthesis was initiated by Knoevenagel condensation of indole-2-one with an appropriate benzaldehyde in presence of L-
proline to afford spiropyrrolidines. Herein, a design and pathway of syntheses of a library of spiropyrrolidines bearing spiro heterocyclic
indeno[1,2-b]quinoxaline-11-one motifs were reported, which also demonstrated an exceptional inhibitory activity against the anticancer
cells. A novel series of dispiroindenoquinoxaline pyrrolizidines were synthesized by the condensation of indeno[1,2-b]quinoxalin-11-
one and starting material (a product of ninhydrin and aldehyde derivatives). The structure of the synthesized compounds was established
by spectral data.
Keywords: Spiropyrrolidines, Knoevenagel condensation, L-proline, Ninhydrin, Benzaldehyde, 1,3-Dipolar cycloaddition.
AChE inhibitory activity [6]. A serious consideration has been
concerned in recent years to the study of 1,3-dipolar cyclo-
addition reactions involving stabilized azomethineylides, which
can be easily obtained from β-amino acids and some carbonyl
compounds such as isatin, ninhydrin and indeno[1,2-b]quino-
xalin-11-one [7] (a product of reaction between ninhydrin and
o-phenylenediamine). This is associated to the fact that 1,3-
dipolar cycloaddition reactions provide the simplest route to
the synthesis of complex alkaloid-like compounds with spiro-
fused pyrrolidine or pyrrolizidine moiety, which have been
shown to exhibit a broad spectrum of biological activities [8-10].
Spiro-pyrrolidines and spiro pyrrolizidines derivatives are
subjected to highly bioactive characteristics due to their spiro
structures. Several works have described that spiropyrrolidines
compounds are highly potent receptors and exhibited interesting
fluorescent characteristics [11]. A substantial amount of liter-
ature is available about the 1,3-dipolar cycloaddition reactions
involving azomethineylides obtained from isatin, ninhydrin
and indeno[1,2-b] quinoxalin-11-one, but the results of every
new reaction and product are not obvious as it depends on
several many factors. Nitrogen containing spiro-heterocyclic
INTRODUCTION
In recent years, interest has been increased to the study of
the indeno[1,2-b] quinoxalin-11-one derivatives. In the present
work, we have reported a multicomponent reaction for the
synthesis of spiro 1,3-indenoquinoxaline by the condensation
of ninhydrin, phenylenediamine, l-proline and substituted alde-
hydes under reflux conditions. A 1,3-dipolar cycloaddition
reaction was found in the one-pot cascade process [1]. Ionova
et al. [2] reported the synthesis of spiropyrrolidines using
11H-indeno[1,2-b]quinoxalin-2-one by aldolcrotonic conden-
sation. In recent time, Sosnovskikh et al. [3] reported the regio-
and stereoselective 1,3-dipolar cycloaddition of indenoquin-
oxalinoneazomethineylides to β-nitrostyrenes, which involves
multicomponent reactions. Simiarly, Shi et al. [4] reported an
efficient regioselective synthesis of novel functionalized dispiro-
pyrrolidines via a three-component [3+2] cycloaddition reaction.
This molecule dispiroindenoquinoxaline pyrrolizines get atten-
tion of the researchers because of their multicomponent inter-
molecular 1,3-dipolar cycloaddition reactions [5]. Some new
dispiroindenoquinoxaline pyrrolizines has also showed the
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1256 Kumar et al.
Asian J. Chem.
compounds [12] have been recognized as an important class
of potentially bioactive compounds often constructed and
produced via 1,3-dipolar cycloaddition of azomethineylides.
In the present work, an insistence was given on developing a
constructive approach for assembling different moieties on a
multicomponent reaction platform for the synthesis of
spiroquinoxaline pyrrolizine derivatives. Multi-component
reactions (MCRs) are regarded as the tool box for the formation
and breakage of several carbon-carbon and carbon-heteroatom
bonds in one pot [13].Assisted by the choice of readily available
starting materials, ease of one-pot procedure and associated
atom economy, MCRs have been broadly employed in the
synthesis of a diversified array of valuable heterocyclic ensem-
bles [14]. It was expected that introduced indenoquinoxaline
to a chiral pyrrolidine or pyrrolizidine ring in the molecule,
through a spiro-atom at the C-3 position could lead to the form-
ation of chiral spiro-indenoquinoxalinepyrrolidine or spiro-
indenoquinoxaline pyrrolizidine systems, thus availing more
opportunities to the formation of a wide range of biologically
active compounds [15]. Hence, because of the predetermined
reasons and in continuous monitoring towards the synthesis of
various spiro heterocyclic compounds, herein reported, a mild,
early, and facile multi-component, one-pot synthesis of novel
heterocyclic chiral spiro-indenoquinoxaline pyrrolidine and
spiro-indenoquinoxaline pyrrolizidine systems through a catalyst
free, one-pot, four-components 1,3-dipolar cycloaddition reaction
of L-proline with ninhydrin, phenylenediamines and starting
materials synthesized by malononitrile and substituted aldehyde
[16].
g, 15 mmol) in 10 mL of acetic acid and 30 mL of methanol
as solvent stirred and refluxed for 1 h. The reaction was moni-
tored by TLC. The precipitate formed was filtered and washed
by methanol (three times) and dried under vacuum to yield
the pure compound as solid yellow coloured (Scheme-II).
O
O
MeOH
CH3COOH
NH2
NH2
N
N
OH
OH
Reflux,1h
O
O-Phenylene-
1,2-diamine
Ninhydrin
11H-Indeno[1,2-b]-
quinoxalin-11-one
Scheme-II
Synthesis of spiro pyrrolizidines:A series of spiro pyrro-
lizidines were synthesized by condensation of indenoquinoxa-
line and synthesized starting material (a product of ninhydrin
and aldehyde derivatives) with L-proline and acetonitrile used
as a solvent.A 10 mL of acetonitrile (as a solvent), indeno[1,2-
b]quinoxalin-11-one (232 mg), 2-benzylidenemalononitrile
(154 mg) and L-proline (127 mg) were added in a round bottom
flask. Reaction was refluxed for 3-4 h until the reaction mixture
becomes homogeneous. Reaction was optimized by TLC after
0.5, 1 and 2 h continuously. After completion the reaction, the
reaction mixture was washed with dichloromethane three times.
The compound was purified by column chromatography by
frictional collection and solvent evaporated by rota evaporator
in order to remove the by products if formed (Scheme-III).
2'-Phenyl-7',7a'-dihydrospiro[indeno[1,2-b]quino-
zaline-11,3'-pyrrolizine]-1',1'(2'H)-dicarbonitrile (spiro
indenoquinoxaline) (1) synthesized by following method
(Scheme-III): Colour: Light yellow solid, yield: 86%, 1H NMR
500 MHz (CDCl3) δH ppm: 8.22 (d, 1H), 7.84 (d, 1H), 7.66 (s,
1H), 7.44 (t, 1H), 7.24 (m, 1H), 5.45 (d, 1H), 5.29 (s, 1H),
4.65 (d, 1H), 2.68 (m, 1H), 2.30-1.96 (m, 2H), 1.68 (s, 1H),
1.26 (m, 1H), 0.87 (d, 1H). MS. m/z 438 (m+1).
EXPERIMENTAL
NMR spectra were recorded on a Bruker AVANCE III HD
500 MHz spectrometer using TMS as an internal standard.
CDCl3 was used as the solvent for dissolving the samples for
NMR. Chemical shifts are given in ppm. The chemicals were
obtained from Sigma-Aldrich and Spectrochem Pvt. Ltd. India
and used without further purification. Commercial grade
solvents were used through the experimental work. Analytical
thin layer chromatography was performed on silica gel coated
on aluminum sheets and monitored using UV light of wave-
length 254 nm. Column chromatography was performed on
60-120 mesh silica gel. Compounds were eluted by a mixture
of hexane and ethyl acetate as required.
Starting material was synthesized by the simple reaction
of malononitrile and substituted aldehyde with lithium bromide
(catalytic amount) and DMF as a solvent. Reaction was stirred
for 1 h at room temperature for 10 min. After the completion
of reaction, a mixture filtered by Whatman filter paper and
dried under vacuum (Scheme-I).
2'-(4-Fluorophenyl)-7',7a'-dihydrospiro[indeno[1,2-
b]quinoxaline-11,3'-pyrrolizine]-1',1'(2'H)-dicarbonitrile
(2): Colour: Dark yellow solid, yield: 84%, 1H NMR, 500 MHz,
(CDCl3) δH ppm: 8.22-8.19 (m, 1H), 7.85 (t, 1H), 7.80 (t, 1H),
7.71-7.67 (m, 1H), 7.45-7.41 (m, 1H), 7.36 (d, 1H), 7.26 (s,
1H), 7.14 (t, 1H), 5.45 (d, 1H), 5.30 (s, 1H), 4.60 (d, 1H),
2.70-2.67 (m, 1H), 2.31-2.28 (m, 1H), 2.16 (m, 1H), 2.05 (s,
1H), 2.00 (d, 1H), 1.58 (s, 1H), 1.26 (s, 1H). MS. m/z 457.
2'-(4-Bromophenyl)-7',7a'-dihydrospiro[indeno[1,2-
b]quinoxaline-11,3'-pyrrolizine]-1',1'(2'H)-dicarbonitrile
1
(3): Light yellow solid, yield: 83%, H NMR, 500 MHz,
(CDCl3) δH ppm: 8.20 (d, 1H), 7.95 (t, 1H), 7.85 (t, 1H), 7.80
(d, 1H), 7.71-7.67 (m, 1H), 7.6 (d, 1H), 7.52 (d, 1H), 7.26 (s,
1H), 5.41 (s, 1H), 4.59 (dd, 1H), 2.69-2.66 (m, 1H), 2.29 (d,
1H), 2.21-2.0 (m, 3H), 1.63-0.88 (m, 3H). MS. m/z 518.
2'-(4-Methoxyphenyl)-7',7a'-dihydrospiro[indeno[1,2-
b]quinoxaline-11,3'-pyrrolizine]-1',1'(2'H)-dicarbonitrile
(4): 1H NMR 500 MHz (CDCl3), δH ppm: 8.21 (s, 1H), 7.92
(d, 2H), 7.84-7.78 (m, 1H), 7.70-7.66 (m, 2H), 7.57 (d, 1H),
7.26 (s, 1H), 7.02-6.99 (m, 3H), 5.39 (d, 1H), 4.60 (dd, 1H),
3.91 (d, 1H), 3.84 (s, 1H), 2.69-2.65 (m, 1H), 2.29 (dd, 1H),
2.20-2.10 (m, 1H), 2.02-1.94 (m, 1H), 1.58 (d, 1H), 1.25 (s,
1H). MS. m/z 470 (m+1).
NC
CN
H
CHO
LiBr
NC
CN
DMF
Scheme-I
Synthesis of indeno[1,2-b]quinoxalin-11-one: A mixture
of o-phenylenediamine (1.782 g, 15 mmol), ninhydrin (2.672

Vol. 32, No. 5 (2020)
Synthesis and Biological Activities of Some Novel Spiro Heterocyclic Pyrrolizidine Derivatives 1257
NC
NC
N
N
NC
N
NC
5
NC
NC
NC
N
N
N
N
N
MeO
NC
N
H
CN
CN
1
4
H
NC
MeO
CN
H
O
N
CN
NC
F
N
H
CN
NC
H
CN
CN
NC
NC
NC
NC
N
Br
N
N
N
Cl
N
N
Cl
F
H
NC
6
CN
2
NC
NC
N
N
Br
N
3
Scheme-III: Synthetic route of novel spiro heterocyclic pyrrolizidine derivatives of 11H-indeno[1,2-b]quinoxaline
2'-(4-Cyanophenyl)-7',7a'-dihydrospiro[indeno[1,2-
b]quinoxaline-11,3'-pyrrolizine]-1',1'(2'H)-dicarbonitrile
(5): 1H NMR 500 MHz (CDCl3), δH ppm: 8.25-8.21 (M, 1H),
7.95 (d, 1H), 7.86-7.76 (m, 2H), 7.72-7.68 (m, 1H), 7.26 (t,
1H), 7.15 (s, 1H), 5.52 (d, 1H), 5.30 (s, 1H), 4.62 (d, 1H),
4.12 (d, 1H), 3.49 (s, 1H), 2.71-2.68 (m, 1H), 2.30 (d, 1H),
2.23-2.15 (m, 1H), 2.02 (s, 1H), 1.61 (d, 1H), 1.40 (s, 1H),
1.27-1.23 (m, 1H). MS. m/z 464.
urally complex and diverse analogous the aldehyde derivatives
and indenoquinoxalines structure both are challenging and
interesting. Considering the potential biological activities of
spiropyrrolidines derivatives and stimulating by the growing
interest in multicomponent reactions, we have synthesized the
spiropyrrolidines compounds with the reaction of indenoquino-
xalines and aldehyde derivatives of malononitrile and L-proline.
When they were reacted acetonitrile and indenoquinoxaline
resulted in the 1,3-dipolar cycloaddition reaction to afford spiro
pyrrolizidines.
A series of spiroindenoxalinepyrrolidines derivatives were
synthesized through 1,3-dipolar cycloaddition reaction. In this
work, spiropyrrolidines were synthesized using Knoevenagel
condensation reaction [17]. Starting material was synthesized
by malononitrile and substituted aldehyde in acetic acid and
dimethyl formamide (DMF) as a solvent. It was challenging to
synthesize starting material with excellent yield and purity.
Biological activities: Moreover, spiro-pyrrolidines and
spiro-pyrrolizidines showed a partial resistance to chemo-
therapeutic agents with respect to the breast cancer cells MCF-
7 and lung cancer cell A-549 [18,19]. In this work, a series of
spiro-pyrrolizidines had been tested for cytotoxicity in the two
human cancer cell lines MCF-7 and non-small cell lung A-
549.
2'-(4-Chlorophenyl)-3a',4'-dihydro-2'H-spiro[indeno-
[1,2-b]quinoxaline-11,1'-pentalene]-3',3'(6a'H)-dicarbo-
1
nitrile (6): Colour: yellow, H NMR 500 MHz (CDCl3), δH
ppm: 8.20 (s, 1H), 7.85 (t, 1H), 7.80-7.77 (m, 1H), 7.72-7.67
(m, 1H), 7.58 (d, 1H), 7.52 (d, 1H), 7.39 (s, 1H), 7.26 (s, 1H),
7.21-7.16 (m, 1H), 5.42 (d, 1H), 5.30 (s, 1H), 5.29 (d, 1H),
2.70-2.66 (m, 1H), 2.30 (d, 1H), 2.20-2.18 (m, 1H) 2.14-2.10
(m, 1H), 2.04-1.95 (m, 1H), 1.58 (s, 1H), 1.25 (s, 1H). MS. m/z
473.
RESULTS AND DISCUSSION
Inspite of the enormous importance of heterocyclic indeno-
quinoxaline derivatives due to their biological activities, only
a few reports are available on the assembly of spiropyrrolidines
derivatives that incorporate both bioactive moieties in a single
structural framework. Consequently, the synthesis of struct-

1258 Kumar et al.
Asian J. Chem.
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of survival curve of the tested cell line. Amongst all the tested
compounds IV and VI showed a very high activity against breast
cancer MCF-7 andA-549 lung cancer cell line (Table-1). These
spiro-pyrrolidine compounds can be promising therapeutic
agents for A-549 lung adenocarcinoma cancer cell line.
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ANTICANCER ACTIVITY OF NOVEL SPIRO
HETEROCYCLIC PYRROLIZIDINE DERIVATIVES (1-6)
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Compound
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13 1.6
Lung cancer (A-549)
16 1.2
1
2
3
4
5
6
13 1.8
14 1.2
14 1.7
14 1.8
15 1.7
15 1.5
15 1.8
15 1.2
13 1.2
16 1.3
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In conclusion, a highly stereoselective and regioselective
synthesis and characterization of novel spiroindinoquinoxaline
pyrrolidines and spiroindenoquinoxaline pyrrolizidines
derivatives containing indenoquinoxaline moiety is reported.
The simplification of this method is established by the regio-
selective synthesis of 11H-indeno[1,2-b]quinoxalin-11-one,
and substituted aldehydes. Indeno[1,2-b]quinoxalin-11-one
have been employed as dipolarophiles for the first time in azo-
methineylide in 1,3-dipolar cycloaddition reactions. Thus, the
present methodoloy paves the way for the synthesis of a variety
of spiroheterocycles in high yields using easily available starting
materials.
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CONFLICT OF INTEREST
https://doi.org/10.1039/C9NJ00994A
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The authors declare that there is no conflict of interests
regarding the publication of this article.
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