Efficient synthesis of spiro[diindenopyridine-indoline]triones Catalyzed by PEG-OSO3H-H2O and [NMP]H2PO4

Article abstract of DOI:10.1080/00397911.2014.906616

One-pot, three-component synthesis of spiro[diindenopyridine-indoline]triones has been reported via the reaction of 1,3-indandione, aromatic amines, and isatins with (PEG-OSO₃H) as an efficient, polymeric acid surfactant-based catalyst in water and also in presence of acidic ionic liquid [NMP]H₂PO₄, which acts both as a medium and catalyst under conventional heating and ultrasonic irradiation. The reactions were complete in short reaction times with excellent yield of products. Surfactant-based PEG-OSO₃H could be recycled and reused several times without any significant loss of activity. The compounds exhibit fluorescence in methanol with large Stokes shift.

Full text of DOI:10.1080/00397911.2014.906616

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Efficient Synthesis of Spiro[Diindenopyridine-
Indoline]triones Catalysed by PEGOSO3H-H2O and
[NMP]H2PO4
Jayant Sindhu a , Harjinder Singh a & J. M. Khurana a
a Department of Chemistry , University of Delhi , Delhi , India
Accepted author version posted online: 25 Sep 2014.
To cite this article: Jayant Sindhu , Harjinder Singh & J. M. Khurana (2014): Efficient Synthesis of Spiro[Diindenopyridine-
Indoline]triones Catalysed by PEGOSO3H-H2O and [NMP]H2PO4 , Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, DOI: 10.1080/00397911.2014.906616
To link to this article: http://dx.doi.org/10.1080/00397911.2014.906616
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Efficient synthesis of spiro[diindenopyridine-indoline]triones catalysed by
PEGOSO3H-H2O and [NMP]H2PO4
Jayant Sindhu1, Harjinder Singh1, J. M. Khurana1
1Department of Chemistry, University of Delhi, Delhi, India
Corresponding author: E-mail: jmkhurana@chemistry.du.ac.in
Abstract
One-pot, three-component synthesis of spiro[diindenopyridine-indoline]triones has been
reported via the reaction of 1,3-indandione, aromatic amines and isatins with (PEG-
OSO3H) as an efficient, polymeric acid-surfactant based catalyst in water and also in
presence of acidic ionic liquid [NMP]H2PO4 which acts both as a medium and catalyst
under conventional heating and ultrasonic irradiation. The reactions were complete in
short reaction times with excellent yield of products. Surfactant based PEG-OSO3H could
be recycled and reused several times without any significant loss of activity. The
compounds exhibit fluorescence in methanol with large stroke shift.
KEYWORDS: Spiro compounds, Multicomponent reactions (MCRs), [NMP]H2PO4,
PEG-6000, Water, Biodegradable, Polymeric
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INTRODUCTION
The development of synthetic methods which are environmentally benign and yield
complex structures from simple and inexpensive starting materials are the main
challenges faced by modern organic chemists these days.[1] Multicomponent reactions
(MCRs) have emerged as a powerful synthetic tool to achieve synthetic efficiency, as
they have unique advantages such as atom economy, operational simplicity and have
played a significant role in modern synthetic chemistry. The use of eco-friendly,
economically viable, recyclable catalysts and reaction medium like water and ionic
liquids make the synthetic approach green and efficient. Reactions have been reported in
ionic liquids (ILs)[2] and also in task specific acidic ionic liquids which act as reaction
medium and/ or catalyst.[3] Development of immobilized catalysts that allow simple
workup procedures, easy separation of products and recyclability of the catalysts is an
important process.[4]
Sulfuric acid modified PEG-6000 (PEG-OSO3H) is an example of polyethylene glycol-
supported catalyst which is functionalized by sulfonic acid groups. It is biodegradable,
recyclable, non-volatile and non-corrosive organic acid that has been used for the
synthesis of heterocyclic compounds.[5] It also acts as a surfactant due to presence of long
chain functionalized by sulfonic acid groups and improves the solubility of the reactants
in water by acting as a phase transfer catalyst. Indenone fused heterocycles represent
important class of medicinally important compounds. Indenopyridines show biological
activities such as cytotoxic,[6] phosphodiesterase inhibitors,[7] adenosine A2a receptor
antagonist,[8] anti-inflammatory/ antiallergic,[9] coronary dilating,[10] and calcium
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modulation.[11] These compounds have also been investigated for the treatment of
hyperlipoproteinemia and arteriosclerosis,[12] as well as neurodegenerative diseases.[13]
Our group has been involved in the development of efficient, green, economical and new
methodologies for the synthesis of biologically important heterocycles.[14] The synthesis
of indenone fused pyridines has been reported with p-TSA in acetonitrile under reflux.[15]
Therefore, we decided to investigate the synthesis of indenone fused heterocycles under a
variety of green methodologies.
RESULTS AND DISCUSSION
We report herein the synthesis of indenone fused heterocycles by three-component
condensation of 1,3-indandione (1), 4-methoxyaniline (2) and isatin (3) in presence of
PEG-OSO3H as a non-corrosive organic acid catalyst and also in presence of Bronsted
acidic ionic liquid [NMP]H2PO4 under conventional heating and ultrasonic irradiation.
The optimization of the reaction conditions for the three component condensation was
carried out by attempting reactions of 1,3-indandione (1) (2.0 mmol), 4-methoxyaniline
(2) (1.0 mmol) and isatin (3) (1.0 mmol). This reaction was initially attempted in
presence of AcOH (30 mol%) and H2SO4 (30 mol%) in water under reflux for 60 min.
The reactions were incomplete as monitored by TLC (ethyl acetate: petroleum ether
(30:70, v/v)) but afforded the desired 5-(4-methoxyphenyl)-5H-spiro[diindeno[1,2-b:2',1'-
e]pyridine-11,3'-indoline]-2',10,12-trione (4a) in 60% and 74% yield respectively after
separation (Table 1, entries 1, 2) (eq. 1).
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The reaction was then attempted using PEG-OSO3H (30 mol%) acid as catalyst in water
under reflux. The reaction was much faster and complete in 10 min. After a simple work
up, it yielded the desired product 4a in excellent yield of 95% (Table 1, entry 3). The
above reaction was repeated at 80oC and was also complete in 10 min giving 97% yield
of the product 4a (Table 1, entry 4). However, the reaction carried out at 60oC under
otherwise identical conditions, required longer reaction time and resulted in poorer yield
(Table 1, entry 5). Also, the reaction attempted using lower loading of catalyst (20 mol%)
at 80oC required longer time and resulted in slightly poorer yield of the product (Table 1,
entry 6). When the reaction was attempted under solvent free conditions using 30 mol%
of PEG-OSO3H, the separation of product was not easy and gave lower yield of the
product 4a (Table 1, entry 7). The same reaction when then attempted using ultrasonic
irradiation at 40oC and resulted in 95% of 4a (Table 1, entry 8).
It can be inferred from Table 1, that the three component reaction yielded the product 4a
in a rapid reaction with high yield when attempted using 30 mol% of PEG-OSO3H as a
catalyst in water under conventional heating at 80oC (Table 1, entry 4) and also under
ultrasonic irradiation at 40oC (Table 1, entry 8). One clear advantage of the PEG-
OSO3H–water combination was that it afforded products that could be obtained by simple
filtration. Encouraged by these results, we investigated the scope of this reaction of 1,3-
indandione (1) with a range of other aromatic amines (2) having electron withdrawing
and electron releasing substituents and isatins (3) under conventional heating at 80oC
(Method A1) (Table 2, Scheme 1) and also under ultrasonic irradiation at 40oC (Method
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A2). All the products (4a-4n) were obtained in high yield and in short reaction time by
both methods as shown in Table 2.
The scope of this reaction was further explored by using Bronsted acidic ionic liquid
[NMP]H2PO4 which could be prepared in a single step without the application of organic
solvents.[16] Therefore, a model reaction of 1,3-indandione (1) (2.0 mmol), 4-
methoxyaniline (2) (1.0 mmol), and isatin (3) (1.0 mmol) was investigated with
[NMP]H2PO4 30 mol% at 60oC. The reaction was complete in 15 min and afforded 5-(4-
methoxyphenyl)-5H-spiro[diindeno[1,2-b:2',1'-e]pyridine-11,3'-indoline]-2',10,12-trione
(4a) in 92% yield after a simple workup. The same reaction was then carried out at 80oC
and 100oC in presence of ionic liquid [NMP]H2PO4 (30 mol %). The reactions were
complete in 10 min and yielded 95% and 94% of 4a respectively. The reaction was then
explored by reducing the catalyst loading (20%). The reaction was complete after 15 min
yielding 90% of 4a. When this reaction was attempted in presence of [NMP]H2PO4 (30
mol%) under ultrasonic irradiation at 40oC, it yielded the product 4a in 94% yield in 5
min.
The condensation of the three components in presence of [NMP]H2PO4 (30 mol %) under
conventional heating at 80oC and also under ultrasonic irradiation at 40oC proved to be
optimum conditions. These optimized reaction conditions were extended for a range of
aromatic amines (2) and different isatins (3) (Scheme 1). All the products were obtained
in high yields and in short reaction times by both of these methods (Method B1 &
Method B2) as shown in Table 3.
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The possibility of recycling of the catalyst (PEG-OSO3H) was also examined using the
reaction of 1,3-indandione (1), 4-methoxyaniline (2) and isatin (3) under optimized
conditions. Upon completion of reaction, the product was filtered at suction pump and
washed with water. In order to recover the catalyst, H2O was removed under reduced
pressure and the resulting liquid was washed with diethyl ether and dried to recover PEG-
OSO3H. The recovered catalyst could be reused 4 times after which there was a
significant decrease in the activity of the catalyst (Fig. 1.).
All the synthesized compounds 4a-4n were characterized by 1H NMR, 13C NMR and
melting point. A plausible mechanism for the synthesis of 4 using PEG-OSO3H and
[NMP]H2PO4 as catalyst is depicted in Scheme 2.
All the compounds formed are deep red in colour. We examined their fluorescent
behaviour also. We observed that all compounds showed strong fluorescence in methanol
when excited at wavelength 268 nm as shown in Fig. 2. The photophysical properties of
all molecules are summarized in Table 4. Moreover, the UV–visible spectra of these
derivatives contain intense absorption maxima in the range of 264-274 nm. These
compounds exhibit emission bands in the range of 282-596 nm with stokes shift in the
range of 115 –142 nm.
CONCLUSION
We have reported an efficient and green methodology for the synthesis of indenone fused
pyridine heterocycles using PEG-OSO3H as a mild, biodegradable, recyclable, non-
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volatile and non-corrosive organic acid in water and also acidic ionic liquid [NMP]H2PO4
which acts as medium and catalyst under conventional heating and ultrasonic irradiation.
All the compounds exhibit strong fluorescence in methanol with large stokes shift.
EXPERIMENTAL
Structures of all of the compounds were identified by their spectral data. Silica gel 60 F254
(Precoated aluminium plates) from Merck were used to monitor reaction progress.
Melting points were determined on Buchi melting point 545 apparatus and are
uncorrected. The 1H and 13C NMR spectra were recorded on Jeol JNM ECX-400P at 400
MHz and 100 MHz respectively. The chemical shift values are recorded on δ scale and
the coupling constants (J) are in Hertz. Ultrasonic bath (54 KHz, 300 W, 3 Lt, capacity)
of Throughclean ultrasonic Pvt. Ltd. (India) was used for reactions under ultrasonic
irradiation. UV-Visible spectra were recorded on Analyticjena Specord UV-Visible
spectrophotometer, while fluorescence spectra were recorded on Carry eclipse
spectrophotometer. PEG(6000)-OSO3H and [NMP]H2PO4 were prepared by the reported
procedures [16].
General Procedure For Synthesis Of 5-(4-Methoxyphenyl)-5H-Spiro[Diindeno[1,2-
B:2',1'-E]Pyridine-11,3'-Indoline]-2',10,12-Trione (4a)
A mixture of indan-1,3-dione (2.0 mmol), isatin (1.0 mmol), 4-methoxyaniline (1.0
mmol), PEG-OSO3H (30 mol%, 1.8 g) as catalyst in water (10 mL) or [NMP]H2PO4 (30
mol%) was placed in a 50 mL round–bottomed flask. The mixture was heated in an oil
bath maintained at 80oC or in ultrasonic bath at 40oC for 5-15 min respectively. After
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completion of reaction as monitored by TLC using ethyl acetate: petroleum ether (30:70,
v/v) as eluent, the reaction mixture was allowed to cool to room temperature. The
precipitate formed was collected by filtration at pump, washed with water, followed by
cold ethanol and dried to yield pure 5-(4-methoxyphenyl)-5H-spiro[diindeno[1,2-b:2',1'-
e]pyridine-11,3'-indoline]-2',10,12-trione (4a) as red solid in high yields. mp >300 °C
(ethanol); 1H NMR (400 MHz, DMSO, d6) δH: 10.62 (1H, s, NH), 8.04-8.01 (1H, m, Ar-
H), 7.83-7.80 (1H, m, Ar-H), 7.38-7.36 (1H, m, Ar-H), 7.30-7.23 (6H, m, Ar-H), 7.19-
7.14 (3H, m, Ar-H), 6.89-6.84 (2H, m, Ar-H), 5.61 (2H, d, 3JHH = 7.2 Hz, ArH), 3.95
(3H, s, OCH3); 13C NMR (100 MHz, DMSO, d6) δC: 189.7, 177.7, 161.0, 156.3, 142.1,
136.2, 134.4, 132.5, 132.4, 131.1, 130.9, 130.3, 128.6, 124.5, 121.6, 121.5, 115.3, 115.2,
113.4, 111.4, 109.1, 55.8.
FUNDING
JS and HS thank UGC, New Delhi, India for the grant of Junior and Senior Research
Fellowships.
SUPPLEMENTARY MATERIAL
Supplemental data for this article can be accessed on the publisher's website.
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Table 1. Reaction of 1,3-indandione (1), 4-methoxyaniline (2) and isatin (3) under
different conditionsa
Entry
Solvent
H2O
H2O
H2O
H2O
H2O
H2O
-
Catalyst (mol %) Temp (oC)
Time (min) Yield (%) (4a)
1
2
3
4
5
6
7
8
AcOH (30)
H2SO4 (30)
100
100
60
60
10
10
15
10
10
5
60b
74b
95
PEG-OSO3H (30) 100
PEG-OSO3H (30) 80
PEG-OSO3H (30) 60
PEG-OSO3H (20) 80
PEG-OSO3H (30) 100
PEG-OSO3H (30) 40
97
88
90
90
H2O
95c
aReaction carried out using 2.0 mmol of 1, 1.0 mmol of 2 and 1.0 mmol of 3
bIncomplete reaction
cReaction performed under ultrasonic irradiation
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Table 2. Synthesis of indenone-fused pyridines by condensation of inden-1,3-dione,
aromatic amines and isatins catalysed by PEG-OSO3Ha
Product Ar
R
Method A1b
Method A2c
Time (min) Yield (%) Time (min) Yield (%)
4a
4b
4c
4d
4e
4f
4-(OMe)C6H4
H
H
H
H
H
10
10
10
10
10
10
10
10
10
10
10
10
10
10
97
95
92
90
94
92
90
88
90
90
88
90
92
90
5
5
5
5
5
5
5
5
5
5
5
5
5
5
95
93
90
92
92
90
92
90
88
92
90
88
94
92
4-MeC6H4
4- (NO2)C6H4
4-BrC6H5
C6H5
4-(OMe)C6H4 NO2
4g
4h
4i
4-(NO2)C6H4
4-MeC6H4
4-BrC6H5
C6H5
NO2
NO2
NO2
NO2
Br
4j
4k
4l
4-MeC6H4
C6H5
Br
4m
4-(NO2)C6H4
Br
4n
4-(OMe)C6H4 Br
aReaction carried out using 2.0 mmol of 1, 1.0 mmol of 2 and 1.0 mmol of 3 in presence
of PEG-OSO3H (30 mol%)
bReaction performed under conventional heating at 80oC
cReaction performed under ultrasonic irradiation at 40oC
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Table 3. Synthesis of indenone-fused pyridines by condensation of inden-1,3-dione,
a
amine and isatin catalysed by [NMP]H2PO4
Product Ar
R
Method B1b
Method B2c
Time (min) Yield (%) Time (min) Yield (%)
4a
4b
4c
4d
4e
4f
4-(OMe)C6H4
H
H
H
H
H
10
10
10
10
15
10
15
10
10
10
10
15
15
10
95
92
90
94
92
90
92
90
90
92
90
92
88
92
5
94
91
92
92
90
92
90
88
92
90
92
90
90
94
4-MeC6H4
4-(NO2)C6H4
4-BrC6H5
C6H5
5
10
5
10
5
4-(OMe)C6H4 NO2
4g
4h
4i
4-(NO2)C6H4
4-MeC6H4
4-BrC6H5
C6H5
NO2
NO2
NO2
NO2
Br
10
5
5
4j
5
4k
4l
4-MeC6H4
C6H5
5
Br
10
5
4m
4-(NO2)C6H4
Br
4n
4-(OMe)C6H4 Br
5
aReaction carried out using 2.0 mmol of 1, 1.0 mmol of 2 and 1.0 mmol of 3 in presence
of [NMP]H2PO4 (30 mol%)
bReaction performed under conventional heating at 80oC
cReaction performed under ultrasonic irradiation at 40oC
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Table 4. Photophysical data of all compounds (4a – 4n) in methanol
Product λabs(nm)
ε x105 ( Lmol-1cm-1)
λem (nm)
407
387
387
407
402
403
402
403
409
407
408
405
406
404
Stoke shift (∆ν) nm
4a
4b
4c
4d
4e
4f
268
272
264
270
277
270
271
270
273
272
266
268
274
271
1.04
1.22
1.03
1.93
1.66
2.88
2.89
1.93
2.77
2.85
1.95
1.82
2.48
2.32
139
115
123
137
125
133
131
133
136
135
142
137
132
133
4g
4h
4i
4j
4k
4l
4m
4n
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Scheme 1. Synthesis of indenone-fused pyridine using one-pot four component
condensation of inden-1,3-dione, aromatic amines and isatins under conventional heating
and ultrasonic irradiation.
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Scheme 2. Proposed mechanism for the synthesis of spirodiindenopyridine-indolines 4.
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Figure 1. Recyclability of PEG-OSO3H for synthesis of compound 4a under
conventional heating.
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Figure 2. Fluorescence spectra of indenone fused pyridine hybrids (4a – 4n).
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