Synthesis of novel coumarinyl-pyrido[2,3-d]pyrimidine-2,4-diones using task-specific magnetic ionic liquid, [AcMIm]FeCl4 as catalyst

Article abstract of DOI:10.1080/00397911.2019.1686526

An acid-functionalized magnetic ionic liquid, 1-acyl-3-methylimidazolium tetrachloroferrate, [AcMIm]-FeCl₄ has been utilized for the synthesis of a series of novel highly functionalized coumarinyl-pyrido[2,3-d]pyrimidine-2,4-dione derivatives (

Full text of DOI:10.1080/00397911.2019.1686526

Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic
Chemistry
ISSN: 0039-7911 (Print) 1532-2432 (Online) Journal homepage: https://www.tandfonline.com/loi/lsyc20
Synthesis of novel coumarinyl-
pyrido[2,3-d]pyrimidine-2,4-diones using task-
specific magnetic ionic liquid, [AcMIm]FeCl4 as
catalyst
Srinivasa Rao Ambati, Jeevan Lal Patel, Satish Gudala, Komal Chandrakar,
Santhosh Penta, S. P. Mahapatra & Subhash Banerjee
To cite this article: Srinivasa Rao Ambati, Jeevan Lal Patel, Satish Gudala, Komal Chandrakar,
Santhosh Penta, S. P. Mahapatra & Subhash Banerjee (2019): Synthesis of novel coumarinyl-
pyrido[2,3-d]pyrimidine-2,4-diones using task-specific magnetic ionic liquid, [AcMIm]FeCl4 as
catalyst, Synthetic Communications, DOI: 10.1080/00397911.2019.1686526
To link to this article: https://doi.org/10.1080/00397911.2019.1686526
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SYNTHETIC COMMUNICATIONSV
https://doi.org/10.1080/00397911.2019.1686526
Synthesis of novel coumarinyl-pyrido[2,3-d]pyrimidine-2,4-
diones using task-specific magnetic ionic liquid,
[AcMIm]FeCl4 as catalyst
Srinivasa Rao Ambatia,b, Jeevan Lal Patela, Satish Gudalaa, Komal Chandrakara,
Santhosh Pentaa, S. P. Mahapatraa, and Subhash Banerjeec
b
aDepartment of Chemistry, National Institute of Technology Raipur, Raipur, India; Department of
c
Research and Development, MSN R&D Center, Pashamylarram, India; Department of Chemistry, Guru
Ghasidas Vishwavidyalaya (A Central University), Bilaspur, India
ABSTRACT
ARTICLE HISTORY
Received 7 July 2019
An acid-functionalized magnetic ionic liquid, 1-acyl-3-methylimidazo-
lium tetrachloroferrate, [AcMIm]-FeCl4 has been utilized for the
synthesis of a series of novel highly functionalized coumarinyl-
pyrido[2,3-d]pyrimidine-2,4-dione derivatives (3a–3l) by the reactions
of various 3-chloro-3-(2-oxo-2H-chromen-3-yl)acrylaldehydes (1) with
functionalized aryl, 6-aminouracils. The major significant of the pre-
sent procedure is the use of task-specific acidic ionic liquid which
act as catalyst as well as reaction medium and thus avoiding use of
organic solvent and/or protic acid catalyst. The other major advan-
tages of the protocol are (i) shorter reaction time (1 h), (ii) easy work
up procedure, (iii) excellent yields of products (91–94%), and (iv)
recyclability of catalyst. The compounds (3a–3l) were identified using
KEYWORDS
b-Chloro coumarinyl
aldehydes; coumarinyl-
pyrido[2,3-d]pyrimidine-2,4-
diones; environmentally
benign synthesis; task-
specific acidic ionic liquid
1
FT-IR, H NMR, and 13C NMR and mass spectroscopic studies.
GRAPHICAL ABSTRACT
R1
R3
N
H
R3
N
FeCl4
COOH
O
O
O
O
F
R2
O
F
R1
MeN
N
N
O
N
Cl
[AcMIm]FeCl4
N
O
NH2
O
O
I
I
R2
3a to 3l
1
2
Introduction
Ionic liquids (ILs) have attracted significant interest as environmentally friendly or
green reaction media in organic synthesis because of their unique properties, such as
non-volatility, non-flammability, low vapor pressure, recyclability, excellent thermal
stability, and desirable solvating properties.[1] On the other hand, functionalized task-
specific ILs even more attractive due to presence of specific functionality which can ini-
tiate a particular reaction. Moreover, many reactions gain acceleration in ILs due to
CONTACT Santhosh Penta
spenta.che@nitrr.ac.in
Department of Chemistry, National Institute of Technology
Raipur, Raipur C.G-492010, India.
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/lsyc.
Supplemental data for this article can be accessed on the publisher’s website.
ß 2019 Taylor & Francis Group, LLC

2
S. R. AMBATI ET AL.
stabilization of charged intermediates or ions.[2] As consequences, ILs have been used in
many organic reactions—for example, three-component reactions[3] and carbon–carbon
bond-forming reactions, such as Michael addition,[4] Henry reaction,[5] Knoevenagel
condensation, and Heck reaction.[6] Recently, the discovery and development of transi-
tion-metal containing multifunctional ILs have emerged as a progressing area in the
field of IL-based research.[7] These materials have showed combined advantages of ILs
with the catalytic, spectroscopic, or magnetic[8] properties of metal ions. On the other
hand, iron has appeared as a promising and feasible catalyst for various organic trans-
formations because iron is one of the most inexpensive, high solubility in organic sol-
vents, excellent Lewis acidity, and non-pollutant metals on earth.[9] Very recently, few
organic transformations with iron-based magnetic ILs (MAILs) as the catalyst or reac-
tion media have been reported. In particular, 1-butyl-3- methylimidazolium tetrachloro-
ferrate ([BMIm]FeCl4) was employed as a catalyst in synthesis of quinazolines,
glycolysis of poly(ethylene terephthalate), Friedel–Crafts acylation, aryl-Grignard cross-
coupling of alkyl halides, and the dimerization of bicyclohepta-2,5-diene.[10] Recently,
we have demonstrated synthesis of and characterization of 1-acyl-3-methylimidazolium
tetrachloroferrate, [AcMIm]FeCl4 for the oxidative hydroxylation of aryl boronic acid,
and Friedal–Craft acylation reactions.[11]
On the other hand, nitrogen-containing heterocyclic molecules have shown a wide
spectrum of biological activities and frequently used in the pharmaceutical industries as
building blocks to design more potent compounds.[12] Accordingly, pyrido[2,3-d]pyrimi-
dine scaffold, an important structural motif, present in a number of compounds show-
ing a variety of biological properties, such as anticancer, antitumor, antimicrobial,
growth regulators, antipyretic, analgesic, antihistaminic, PDE4 inhibitors, adenosine kin-
ase inhibitor, and tyrosine kinase inhibitor[13] activities. On the other side, coumarin
(2 H-1-benzopyran-2-one) and its derivatives attracted much attention due to their
diverse pharmaceutical properties such as anti-HIV, anticancer, anti-influenza, antialz-
heimer, antituberculosis, antiviral, and antimicrobial activities.[14]
Surveying literature revealed that a number of approaches to the synthesis of pyr-
ido[2,3-d]pyrimidine-2,4-dione derivatives have been reported and are mostly based on
the reaction of 6-aminouraciles and suitable bifunctional electrophilic substrates, such as
acetylenic ketones and esters, a,b-unsaturated carbonyls and nitriles, 1,3-dicarbonyl
compounds, and condensation with aldehydes and active methylenes.[15–18] Among the
reported pyrido[2,3-d]pyrimidine-2,4-diones, synthesis of 3-cyclopropyl derivatives is
highly limited.
Results and discussions
As a part of our continuing interest to synthesize biologically active heterocycles[19] and
in developing task-specific ILs,[20] herein, we report the synthesis of highly functional-
ized coumarinyl-pyrido[2,3-d]pyrimidine-2,4-dione derivatives using a [AcMIm]FeCl4,
under organic solvent/acids/base/or ligand-free reaction conditions (Scheme 1).
The key intermediates 3-chloro-3-(2-oxo-2H-chromen-3-yl)acrylaldehyde (1) and
functionalized aryl, 6-aminouracils (2) were prepared according to the reported
method.[21] In our initial studies, 3-chloro-3-(2-oxo-2H-chromen-3-yl)acrylaldehyde (1a)

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SYNTHETIC COMMUNICATIONSV
3
R1
R3
H
R3
N
FeCl4
COOH
O
N
O
O
O
F
R2
O
F
R1
MeN
N
N
O
N
Cl
[AcMIm]FeCl4
N
O
NH2
O
O
I
I
R2
3a to 3l
1
2
R2
R3
Compound
R1
3a
3b
3c
3d
3e
3f
3g
3h
3i
Cyclo propyl
Cyclo propyl
Cyclo propyl
Cyclo propyl
Cyclo propyl
Cyclo propyl
Methyl
Methyl
Methyl
Methyl
Methyl
H
H
Br
H
H
Cl
H
H
Br
H
H
H
Br
Br
OMe
Cl
Cl
H
Br
Br
OMe
Cl
3j
3k
3l
Methyl
Cl
Cl
Scheme 1. Synthesis of coumarinyl pyrido[2,3-d]pyrimidine-2,4-dione derivatives using magnetic ionic
liquid, [AcMIm]FeCl4.
Table 1. Optimization of reaction conditions for the synthesis of title compounds.
Entry
Solvent/catalysta
Temperature (ꢀC)
Time (h)
Yields (%)b
1
2
3
4
5
6
7
8
Acetic acid
Trifluoro acetic acid
Ethanol
CH3CN
DMF
[AcMIm]Cl (20 mol %)
C2H5OH/FeCl3 (1 mol %)
C2H5OH/FeCl3 (1 mol %)
C2H5OH/FeCl3 (5 mol %)
CH3CN/FeCl3 (5 mol %)
CH3CN/FeCl3 (10 mol %)
Dioxane/FeCl3 (5 mol %)
[AcMIm]FeCl4 (10 mol %)
[AcMIm]FeCl4 (20 mol %)
[AcMIm]FeCl4 (20 mol %)
[AcMIm]FeCl4 (30 mol %)
Reflux
Reflux
Reflux
Reflux
Reflux
80 oC
RT
Reflux
Reflux
Reflux
Reflux
Reflux
RT
7.0
7.0
7.0
7.0
7.0
1.0
7.0
7.0
7.0
7.0
7.0
7.0
1.0
1.5
1.0
1.0
35
60
Trace
Trace
Trace
65
5
12
20
35
35
15
70
75
94
94
9
10
11
12
13
14
15
16
RT
60 ꢀC
80 ꢀC
aReagents and conditions: 1 (1.0 mmol), 2 (1.0 mmol), [AcMIm]FeCl4 (20 mol %, 67 mg), or organic solvents (2 mL),
bIsolated yields. All reactions were monitored with TLC.
with 6-amino-3-cyclopropyl-1-(2-fluoro-4-iodo-phenyl)-1H-pyrimidine-2,4-dione (2a)
and solvents/ionic liquids were used as a model substrates to optimize the reaction con-
ditions. As shown in Table 1, the [AcMIm]FeCl4 played an important role on the yield
of products. The reaction gave the highest yield (94%) at 60 ꢀC in the presence of
20 mol % of [AcMIm]FeCl4 (Table 1, entry 15).
Increasing the amount of [AcMIm]FeCl4 to 30 mol % and temperature, however, the
yield of 3a did not improve to a great extent (Table 1, entry 16). Other acidic solvents/
catalysts such as AcOH and TFA were also used to compare the reaction yields. In these

4
S. R. AMBATI ET AL.
F
I
O
O
N
O
F
N
N
N
O
O
Fe(III)Cl
N
R
4
NH2
O
N
O
I
F
2
+
N
3
O
I
NH2
I
O
H
2
O
Cl
O
1
Fe(III)Cl
R
4
O
H
O
Cl
O
F
1
O
N
N
H
N
Cl
O
I
O
O
H
B
N
I
F
O
Fe(III)Cl
R
O
4
N
N
Cl
NH2
O
O
O
F
O
N
A
Cl
N
O
O
O
Fe(III)Cl
HOOC
R
4
Recyclable catalyst
R=
N
NMe
Scheme 2. The plausible mechanism for the synthesis of coumarinyl-pyrido[2,3-]pyrimidine-2,4-dione
derivatives.
cases, the products were isolated in poor yields (Table 1, entries 1 and 2). In ethanol,
CH3CN and DMF only a trace amount of 3a was obtained (Table 1, entries 3–5). The
reaction also initiated with [AcMIm]Cl and provided 65% of yield (entry 6, Table 1).
Since, iron salts are inexpensive, environmentally friendly and acting as a Lewis acid
property, the feasibility on FeCl3 alone catalyzed reaction was then examined. A range
of solvents and amount of Iron chloride were applied (Table 1, entry 7–12). Only 35%
isolated yield of desired product 3a was obtained when 5 mol % of FeCl3/CH3CN was
employed (Table 1, entry 10).
However, screening of various solvents and catalysts revealed that 20 mol % of
[AcMIm]FeCl4 provided the best result in terms of product yield (94%) and reaction
time (60 min). Thus, 20 mol % (67 mg) of [AcMIm]FeCl4 was chosen as a quantitative
catalyst as well as reaction medium to drive the reaction forward with maximum yield
of the product. Next, using optimum reaction conditions, we have synthesized series of
coumarinyl-pyrido[2,3-d]pyrimidine-2,4-dione derivatives (3a–l). The formation of

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SYNTHETIC COMMUNICATIONSV
5
100
80
60
40
20
0
1
2
3
4
5
6
7
Number of run
Figure 1. Reusability of [AcMIm]FeCl4 for the synthesis of 3a.
desired products was confirmed from their analytical and spectral data. For example,
the FT-IR spectrum of compound 4a showed three strong absorption peaks at 1724.28,
1653.19, and 1250.02 cmꢁ1 for lactone carbonyl, C¼N, and aryl ethers, respectively. The
1H NMR spectrum of compound 4a showed multiplets from d ¼ 0.76–1.08 for methy-
lene groups of cycloprapane moiety. Two doublets were observed at d ¼ 8.22 and
d ¼ 8.53 for pyridine ring protons. All the newly synthesized products were identified
by the spectroscopic data (3a–l). The proposed mechanism is outlined in Scheme 2. In
the first step, the carbonyl group and amine group are activated by ([AcMIm]FeCl4, for
a condensation reaction between 3-chloro-3-(2-oxo-2H-chromen-3-yl)acrylaldehyde 1,
and a 6-aminouracils 2 would give the imine intermediate A. This intermediate A,
which subsequently undergoes Michael type of reaction with itself via dehydrohalogina-
tion followed by cylization afforded the desired compound 3.
After the completion of reaction, diethyl ether was added to the reaction mixture to dis-
solve the organic products and IL was separated using external magnet, washed with ether,
dried in vacuum, and reused for subsequent reactions. The recyclability of [AcMIm]FeCl4
was investigated for the synthesis of compound 3a as model reaction and it was observed
the IL remained active up to seven runs (Fig. 1). The little loss in yield could possibly due
to the loss of IL and absorption of moisture during recycling process.
Conclusions
A task-specific acid-functionalized magnetic IL, [AcMIm]FeCl4, has been successfully
employed as an efficient, inexpensive, magnetically separable catalyst and reaction media
for the synthesis of coumarinyl-pyrido[2,3-d]pyrimidine-2,4-dione derivatives. The reac-
tions were very clean, high yielding (91–94%) and complete within very short time periods
(1 h). The IL was reused at least for seven times without significant loss in catalytic efficacy
and stability. To the best of our knowledge this the first example of use of [AcMIm]FeCl4
in one-pot synthesis of nitrogen-containing heterocyclic compounds, and we believe that
this finding will open up a new frontier in sustainable organic synthesis.

6
S. R. AMBATI ET AL.
Experimental
General
All the reagents and solvents were pure, purchased from commercial sources and were
used without further purification unless otherwise stated. Melting points were deter-
mined in open capillaries with a “Cintex” melting point apparatus (Mumbai, India) and
were uncorrected. CHNS analysis was carried out using Carlo Erba EA 1108 automatic
elemental analyzer. The purity of the compounds was checked using TLC plates
(E.Merck Mumbai, India). IR spectra (KBr) were recorded on a Thermo Nicolet Nexus
1
670 spectrophotometer. H NMR spectra were recorded on a Bruker WM-400 spec-
trometer in d ppm using TMS as standard. Mass spectra (EI-MS) were determined on
Perkin Elmer (SCIEX API-2000, ESI) at 12.5 eV.
General procedure for the synthesis of coumarinyl-pyrido[2,3-d]pyrimidine-2,4-
dione derivatives using acidic, magnetic ionic liquid: (3a–3l)
In a typical experimental procedure, chloroacrylaldehydes (1 mmol) and various 6-
amino uraciles (1 mmol) were taken in a magnetic acidic ionic liquid, [AcMIM]FeCl4
(20 mol %, 67 mg). The reaction solution was allowed to stir at 60 ꢀC temperature until
completion of the reaction. The reactions were monitored using TLC. After the reaction,
final derivatives were easily extracted by washing the ionic liquid layer with diethyl
ether (5 ꢂ 5 mL) using external magnetic field. The combined organic layer was dried
over anhydrous sodium sulfate and evaporated using rotavapor to get the desired prod-
ucts. The crude product was purified by recrystallization from absolute ethanol.
3-Cyclopropyl-1-(2-fluoro-4-iodophenyl)-5-(2-oxo-2H-chromen-3-yl)pyrido[2,3-d]
pyrimidine-2,4(1H,3H)-dione: (3a)
Yield (94%); mp: 246–250jC; IR (KBr, cmꢁ1), 1724.28 and 1653.19 (C¼O), 1491.21
1
(C¼C), 1353 (C–F), 1250.02 (aryl ethers, C–O–C); H NMR (400 MHz, DMSO-d6, d
ppm): 0.76–1.08 (m, 4H, –CH2), 2.77–2.79 (m,1H, –CH), 7.40–7.48 (m, 3H, Ar-H), 7.58
(d, J ¼ 7.6 Hz, 1H, Ar-H), 7.69–7.73 (m, 1H, Ar-H), 7.84 (d, J ¼ 8.4 Hz, 1H, Ar-H) , 8.02
(d, J ¼ 9.2 Hz, 1H, Ar-H), 8.12 (s, 1H, C-4 of coumarin), 8.23 (d, J ¼ 8.0 Hz, 1H, pyri-
dine-H) , 8.53 (d, J ¼ 8.0 Hz, 1H, pyridine-H). 13C NMR (DMSO-d6, d ppm): d
3
3
8.10–8.29, 24.11, 96.96 (d, JCF ¼ 9), 111.23, 114.53, 121.41, 122.09 (d, JCF ¼ 18),
2
2
122.95, 124.29, 125.70 (d, JCF ¼ 49), 127.28, 129.28, 130.045 (d, JCF ¼ 25), 133.23,
1
134.49, 134.63, 146.10, 147.05, 148.36, 149.37, 150.31, 152.45 (d, JCF ¼ 269), 156.35,
159.72, 162.52, 163.37.ESI-MS: 568 [M þ H]. Anal. Calcd for C25H15FIN3O4: C,52.93; H,
2.67; N, 7.41; Found: C, 52.87; H, 2.79; N, 7.47.
Full experimental detail, H NMR, 13C NMR, and Mass spectral copies. This material
1
can be found via the “Supplementary Content” section of this article’s webpage.’
Acknowledgments
The authors are thankful to the Director, NIT Raipur for providing facilities. S. A. thanks the
Head, MSN, R&D center for encouragement and valuable suggestions.

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