An efficient one-pot three-component synthesis of pyrimido[4,5-d]pyrimidine derivatives in aqueous medium

Article abstract of DOI:10.1007/s10593-015-1769-3

[Figure not available: see fulltext.] A fast, efficient, and green synthesis of pyrimido[4,5-d]pyrimidine derivatives has been achieved via one-pot three-component reaction starting from 6-amino-N,N-dimethyluracil, phenylisothiocyanate or phenylisocyanate

Full text of DOI:10.1007/s10593-015-1769-3

DOI 10.1007/s10593-015-1769-3
Chemistry of Heterocyclic Compounds 2015, 51(8), 749–753
An efficient one-pot three-component synthesis
of pyrimido[4,5-d]pyrimidine derivatives in aqueous medium
Sreedhar Badvel1, Raveendra Reddy Gopireddy1, Thaslim Basha Shaik2,
Sudhamani Hasti2, Veera Reddy Tummaluru1*, Naga Raju Chamarthi2
1 Department of Chemistry, Vikrama Simhapuri University,
Nellore-524 003, Andhra Pradesh, India; e-mail: tvreddy.vsu@gmail.com.
2 Department of Chemistry, Sri Venkateswara University,
Tirupati-517 502, Andhra Pradesh, India; e-mail: thaslimsvu@gmail.com .
Published in Khimiya Geterotsiklicheskikh Soedinenii,
2015, 51(8), 749–753
Submitted February 7, 2015
Accepted after revision July 6, 2015
O
Reusable
PEG-SO3H
catalyst
Me
N
O
Ar
Me
O
N
N
O
N
Me
NH2
ArCHO
NCX
H2O, 
N
Me
N
H
X
A fast, efficient, and green synthesis of pyrimido[4,5-d]pyrimidine derivatives has been achieved via one-pot three-component reaction
starting from 6-amino-N,N-dimethyluracil, phenylisothiocyanate or phenylisocyanate, and aromatic aldehydes in the presence of poly-
ethylene glycol-bound sulfonic acid as a catalyst in water as solvent.
Keywords: 6-amino-N,N-dimethyluracil, phenylisocyanate, phenylisothiocyanate, Lewis acid, PEG-bound sulfonic acid, three-
component reaction.
Multicomponent reactions (MCRs) have recently gained
a considerable attention in organic synthesis, because they
involve simultaneous reaction of more than two starting
materials to yield a single product through one-pot
reaction. Good selectivity, minimum waste production, low
energy consumption, and high atom efficiency make MCRs
suitable for the synthesis of varied drug candidates with
augmented bioactivity.1
Nowadays, synthetic chemists try to avoid using hazardous
solvents, toxic and expensive reagents in their work for the
sake of environment and to choose environmentally benign
reusable catalysts and solvents, instead. Among the
environment friendly solvents for organic synthesis, water
is particularly good because it is cheap, non-toxic, non-
corrosive, non-flammable,2–5 offers good selectivity, and
can be easily separated from the organic products.
addition reactions,14–17 as well as three-component reac-
tions.18–20 Some of them use AcOH,14,19 p-toluenesulfonic
acid,20 and iodine17 as catalysts. One of the reported proce-
dures20 features water as solvent while a few others15,16,18
are solvent-free. Recently, Wang et al.21 reported a synthe-
sis of highly substituted pyrimido[4,5-d]pyrimidine deri-
vatives involving 6 steps. However, these methods require
extreme conditions like long reaction time, high energy,
and complex synthetic pathways. To overcome these
difficulties, we pursue to select a suitable, sustainable
catalyst for the synthesis of pyrimido[4,5-d]pyrimidines.
For years, the attention of organic chemists has been
focused on polymer-supported catalysts due to their low
cost, high catalytic activity, easy work-up procedure, and
recyclability.22 In the search for environmentally benign
polymer-supported catalysts they have come up with
polyethylene glycol-bound sulfonic acid (PEG–SO3H)23–28
which is attractive because of its acidic, non-volatile, non-
corrosive, economical, and recyclable nature. This
homogeneous catalyst has also been used for the synthesis
of the heterocyclic compounds.29,30 Herein, we report the
catalytic activity of PEG–SO3H for the synthesis of fused
uracil derivatives.
Heterocyclic motifs play a prominent role in the design
and synthesis of bioactive molecules. Pyrimidines and
fused pyrimidines have been found to possess diverse
biological activity.6–8 In particular, among pyrimido[4,5-d]-
pyrimidines, a class of annulated uracils, a wide range of
biologically active compounds like bronchodilators,9
antiallergic,10 cardiotonic,11,12 antihypertensive,13 and anti-
cancer14 agents have been found.
Initially we performed the reaction of a mixture con-
taining 6-amino-N,N-dimethyluracil (1) (1 mmol), phenyl-
isothiocyanate (2, X = S) (1 mmol), and benzaldehyde
The synthesis of pyrimido[4,5-d]pyrimidine derivatives
is less investigated. The known methods include cyclo-
0009-3122/15/5108-0749©2015 Springer Science+Business Media New York
749

Chemistry of Heterocyclic Compounds 2015, 51(8), 749–753
Scheme 1
(3, Ar = Ph) (1 mmol) in water at a temperature of up to
70°C in the absence of catalyst to obtain compound 4a
(Scheme 1). The reaction did not take place even after 3 h.
In order to identify the optimal reaction conditions, we
conducted the reaction in the presence of catalytic amount
of PEG–SO3H both in aqueous and non-aqueous media.
The PEG–SO3H-catalyzed synthesis of compound 4a
was performed using different amounts of the catalyst in
water. The results are summarized in Table 1. It was found
that 10 mol % of PEG-SO3H catalyzed the reaction most
efficiently in terms of yield and reaction time. A further
increase of the amount of catalyst made no improvement in
the yield. The role of solvent in the reaction was also
investigated. Interestingly, the target compound was
formed in good yields in both media, but the reaction time
is less in aqueous medium because the catalyst is water-
soluble.
In order to evaluate the efficiency of the present
methodology, we have checked different acid catalysts for
the synthesis of compound 4a as a model reaction, and
results of this study are presented in Table 2. It is clear
from the data shown that the present method is more
efficient in both in terms of yields and reaction time and
also compared with the aqueous p-TSA-catalyzed synthesis
described earlier.20
compared to isothiocyanate. The average time taken for the
synthesis of all the title compounds was 50–70 min.
Aldehydes having electron-withdrawing groups react in a
shorter time and with higher yield than those having
electron-donating groups owing to the higher electro-
philicity of the former.
The structure of the novel pyrimido[4,5-d]pyrimidine-
2,4,7(1H,3H,6H)-triones 4g–l was fully characterized by
IR, 1H and 13C NMR, and mass spectra, as well as
elemental analysis. In the IR spectra, stretching frequencies
at 1675–1690, 1711–1717, and 3218–3328 cm–1 confirmed
the presence of carbonyl functional groups and NH proton
in the molecule. In the 1H NMR spectra, the two singlets at
Table 2. Yield of compound 4a using different catalysts*
Catalyst
–
Time, min
420
Yield, %
No reaction
AcOH
360
20
45
40
55
42
68
82
Yb(OTf)3
I2
240
210
InCl3
190
NH2SO3H
p-TSA
160
Using these optimized conditions, we examined the
scope of the reactions using isothiocyanate or isocyanate
(2, X = S or O, respectively) with different aromatic
aldehydes 3. The results are presented in Table 3. Because
of the strong acidic nature of PEG–SO3H the electro-
philicity of the aldehyde increases, which facilitates the
attack by nucleophile and thus allows the reaction to be
complete in a shorter period of time. In the synthesis of the
target compounds 4a–l, isocyanate gave higher yields when
90
PEG–SO3H
50
* Catalyst load 10 mol %, for other conditions, see Table 1.
Table 3. Yields of PEG–SO3H-catalyzed synthesis
of pyrimido[4,5-d]pyrimidines 4a–l in water
X
Ar
Product
Yield, %
S
S
Ph
82
80
84
78
86
90
86
85
88
84
90
94
4a
4b
4c
4d
4e
4f
Table 1. The effect of catalyst load and solvent on the yield
and reaction time of PEG–SO3H-catalyzed synthesis
of compound 4a*
p-MeC6H4
p-ClC6H4
p-BrC6H4
p-MeOC6H4
p-NO2C6H4
Ph
S
Catalyst load, mol %
Solvent
H2O
Time, min
Yield, %
S
0
180
90
No reaction
S
1
H2O
76
86
90
34
38
35
30
S
5
H2O
60
O
O
O
O
O
O
4g
4h
4i
10
10
10
10
10
H2O
50
p-MeC6H4
p-ClC6H4
p-BrC6H4
p-MeOC6H4
p-NO2C6H4
CH2Cl2
MeOH
EtOH
THF
80
85
4j
90
100
4k
4l
* Compound 1 (1 mmol), compound 2 (1 mmol), compound 3 (1 mmol),
PEG–SO3H (10 mol %), water (10 ml), 70°C, 50 min.
750

Chemistry of Heterocyclic Compounds 2015, 51(8), 749–753
Scheme 2
2.35–3.25 and 3.12–3.56 ppm can be assigned the protons
of two methyl groups, and a broad singlet at 7.58–7.68 ppm
corresponds to the NH proton. The mass spectra of
compounds 4g–l showed the corresponding protonated mole-
cular ion signals. The identity of 7-thioxopyrimido[4,5-d]-
pyrimidine-2,4(1H,3H)-diones 4a–f described earlier20 was
likewise confirmed by their spectral and physical
characteristics.
Furthermore, we have also investigated the recyclability
of PEG–SO3H catalyst. Four consecutive cycles of catalyst
recovery and reaction showed almost the same catalytic
activity. In order to recover the catalyst, water was added to
the reaction mixture after completion of the reaction, and it
was shaken to dissolve PEG–SO3H. The insoluble com-
pound was filtered, extracted with ethyl acetate, and
recrystallized from ethanol. The aqueous filtrate containing
the catalyst was evaporated under reduced pressure, and the
resulting solid was washed with diethyl ether and dried
under reduced pressure. By using this recovered catalyst,
the reaction was carried out for next three cycles for the
synthesis of compound 4a, and in this process we have
observed the smooth decline of the isolated product yield
due to the decrease of the amount of PEG–SO3H catalyst
(less than 10 mol %) due to the recovery loss after each
cycle (Table 4).
in the presence of PEG–SO3H catalyst gives intermediate
B. Its subsequent cyclization and dehydration complete the
reaction.
In summary, we have established an efficient one-pot
three-component protocol for the synthesis of pyrimido[4,5-d]-
pyrimidine derivatives by environmentally benign and
economically viable PEG–SO3H catalyst in water as
solvent. Furthermore, short reaction times, excellent yields,
simple work-up procedure, and utilization of an
inexpensive and reusable catalyst are the advantages of the
present methodology. This methodology is a valuable
addition to the existing repertory of methods for the
synthesis of pyrimido[4,5-d]pyrimidine derivatives.
Experimental
FT-IR spectra were recorded on a Bruker ALPHA
1
spectrometer. H and 13C NMR spectra were recorded on a
Bruker AMX instrument (300 and 100 MHz, respectively)
in DMSO-d6 with TMS as internal standard. LC-MS
spectra were recorded on an Acquity Ultra Performance
Liquid Chromatography instrument coupled with an API 3000
mass spectrometer operating in electrospray positive
ionization mode. Elemental analysis was performed on a
Thermo Finnegan Flash EA 1112 instrument at University
of Hyderabad, Hyderabad, India. Melting points were
determined in open capillaries on Guna melting point appa-
ratus and are uncorrected. Silica gel column chromato-
graphy was performed using Merck 7734 silica gel (60–
120 mesh). TLC was done on Merck TLC plates. The
chemicals were purchased from Sigma-Aldrich Chemicals.
Preparation of PEG–SO3H. Chlorosulfonic acid
(0.11g, 10 mmol) was added to a solution of PEG (0.6 g,
1 mmol of SO3H groups) in CH2Cl2 (10 ml) at 0°C, and the
resulting solution was stirred at room temperature over-
night. Then, the solution was concentrated under vacuum,
and ether was added to it. The resulting precipitate was
filtered off and washed with ether to give 4.82 mg of PEG–
SO3H as a white solid.
A possible mechanism for the formation of product 4 is
shown in Scheme 2. Primarily, the intermediate A is
formed in situ from the reaction of 6-amino-N,N-dimethyl-
uracil 1 with phenylisothiocyanate or phenylisocyanate 2.
Then, nucleophilic attack of intermediate A to aldehyde 3
Table 4. Recyclability of the PEG–SO3H in the synthesis
of compound 4a
The number of recyclings
Time, min
Yield, %
0
1
2
3
18
18
18
18
92
90
86
80
1,3-Dimethyl-5,6-diphenyl-7-thioxo-5,6,7,8-tetrahydro-
pyrimido[4,5-d]pyrimidine-2,4(1H,3H)-dione (4a). A mixtu-
re of phenylisothiocyanate (2, X = S) (0.135 g, 0.89 mmol),
751

Chemistry of Heterocyclic Compounds 2015, 51(8), 749–753
6-amino-N,N-dimethyluracil (1) (0.155 g, 1.00 mmol), and
Yield 84%, mp 237–238°C. IR spectrum ν, cm–1: 3316,
1714, 1680. 1H NMR spectrum, δ, ppm: 3.14 (3H, s, CH3);
3.52 (3H, s, CH3); 5.68 (1H, s, 5-CH); 7.05–7.42 (9H, m,
H Ar); 7.60 (1H, s, NH). 13C NMR spectrum, δ, ppm: 29.2;
31.6; 35.4; 104.5; 123.3; 125.6 (2C); 126.3 (2C); 127.8
(2C); 128.1; 128.7 (2C); 129.4; 131.5; 138.4; 140.4; 148.4;
152.7. Mass spectrum, m/z: 441 [M+H]+. Found, %:
C 54.32; H 3.72; N 12.58. C20H17BrN4O3. Calculated, %:
C 54.44; H 3.88; N 12.70.
5-(4-Methoxyphenyl)-1,3-dimethyl-6-phenyl-5,8-dihydro-
pyrimido[4,5-d]pyrimidine-2,4,7(1H,3H,6H)-trione (4k).
Yield 90%, mp 220–231°C. IR spectrum ν, cm–1: 3325,
1712, 1675. 1H NMR spectrum, δ, ppm: 3.25 (3H, s, CH3);
3.56 (3H, s, CH3); 3.68 (3H, s, CH3O); 5.36 (1H, s, 5-CH);
7.08–7.34 (9H, m, H Ar); 7.66 (1H, s, NH). 13C NMR
spectrum, δ, ppm: 28.7; 31.3; 36.4; 53.8; 104.7; 123.6;
125.8 (2C); 126.6; 127.8 (2C); 128.3 (2C); 128.7; 129.5;
131.2; 136.4; 140.7; 148.4; 151.2; 153.5. Mass spectrum,
m/z: 393 [M+H]+. Found, %: C 64.10; H 5.04; N 14.16.
C21H20N4O4. Calculated, %: C 64.28; H 5.14; N 14.28.
1,3-Dimethyl-5-(4-nitrophenyl)-6-phenyl-5,8-dihydro-
pyrimido[4,5-d]pyrimidine-2,4,7(1H,3H,6H)-trione (4l).
Yield 94%, mp 222–223°C. IR spectrum ν, cm–1: 3328,
1715, 1683. 1H NMR spectrum, δ, ppm: 3.20 (3H, s, CH3);
3.50 (3H, s, CH3); 5.44 (1H, s, 5-CH); 7.10–7.42 (9H, m,
H Ar); 7.68 (1H, s, NH). 13C NMR spectrum, δ, ppm: 28.8;
31.5; 36.2; 106.2; 124.3; 125.1; 125.6 (2C); 126.8 (2C);
127.4; 128.5; 129.2 (2C); 131.4 (2C); 137.7; 141.8; 147.3;
152.4. Mass spectrum, m/z: 408 [M+H]+. Found, %:
C 58.82; H 4.06; N 17.08. C20H17N5O5. Calculated, %:
C 58.97; H 4.21; N 17.19.
benzaldehyde (3, Ar = Ph) (0.106 g, 1.00 mmol) in water
(10 ml) was refluxed in the presence of PEG–SO3H (0.6 g,
0.1 mmol). After the completion of the reaction (monitored
by TLC, eluent n-hexane–AcOEt, 3:1), the reaction mixture
was diluted with water (20 ml). The solid was separated by
filtration and washed with water, dried, and recrystallized
from ethanol. Yield 82%, mp 268–269°C (mp 269–
270°C19). Compounds 4b–l were synthesized analogously.
1,3-Dimethyl-5-(4-methylphenyl)-6-phenyl-7-thioxo-
5,6,7,8-tetrahydropyrimido[4,5-d]pyrimidine-2,4(1H,3H)-
dione (4b). Yield 80%, mp 271–272°C (mp 270–271°C19).
5-(4-Chlorophenyl)-1,3-dimethyl-6-phenyl-7-thioxo-
5,6,7,8-tetrahydropyrimido[4,5-d]pyrimidine-2,4(1H,3H)-
dione (4c). Yield 84%, mp 274–275°C (mp 275–276°C19).
5-(4-Bromophenyl)-1,3-dimethyl-6-phenyl-7-thioxo-
5,6,7,8-tetrahydropyrimido[4,5-d]pyrimidine-2,4(1H,3H)-
dione (4d). Yield 78%, mp 278–279°C (mp 279–280°C19).
5-(4-Methoxyphenyl)-1,3-dimethyl-6-phenyl-7-thioxo-
5,6,7,8-tetrahydropyrimido[4,5-d]pyrimidine-2,4(1H,3H)-
dione (4e). Yield 86%, mp 271–272°C (mp 270–271°C19).
1,3-Dimethyl-(4-nitrophenyl)-6-phenyl-7-thioxo-5,6,7,8-
tetrahydropyrimido[4,5-d]pyrimidine-2,4(1H,3H)-dione
(4f). Yield 90%, mp 272–273°C (mp 273–274°C19).
1,3-Dimethyl-5,6-diphenyl-5,8-dihydropyrimido[4,5-d]-
pyrimidine-2,4,7(1H,3H,6H)-trione (4g). Yield 86%,
mp 224–225°C. IR spectrum ν, cm–1: 3218, 1717, 1690.
1H NMR spectrum, δ, ppm: 3.05 (3H, s, CH3); 3.12 (3H, s,
CH3); 5.40 (1H, s, 5-CH); 7.22–7.38 (10H, m, H Ar); 7.58
(1H, s, NH). 13C NMR spectrum, δ, ppm: 28.6; 31.2; 105.3;
123.8 (2C); 124.3; 125.4; 126.5; 128.2 (2C); 129.4 (2C);
131.5 (2C); 137.7; 140.4; 146.5; 148.3; 151.2; 153.8. Mass
spectrum, m/z: 363 [M+H]+. Found, %: C 66.12; H 4.88;
N 14.28. C20H18N4O3. Calculated, %: C 66.29; H 5.01;
N 15.46.
The authors thank to Vikrama Simhapuri University,
Nellore, for providing the lab facilities and University of
Hyderabad, Hyderabad, for recording the NMR spectra
and performing elemental analysis.
1,3-Dimethyl-5-(4-methylphenyl)-6-phenyl-5,8-dihydro-
pyrimido[4,5-d]pyrimidine-2,4,7(1H,3H,6H)-trione (4h).
Yield 85%, mp 218–219°C. IR spectrum ν, cm–1: 3323,
1711, 1684. 1H NMR spectrum, δ, ppm: 2.35 (3H, s, CH3);
3.40 (3H, s, CH3); 3.54 (3H, s, CH3); 5.56 (1H, s, 5-CH);
7.05–7.44 (9H, m, H Ar); 7.64 (1H, s, NH). 13C NMR
spectrum, δ, ppm: 22.3; 27.8; 30.4; 37.2; 105.3; 121.2
(2C); 123.5; 126.8 (2C); 128.5 (2C); 130.4 (2C); 135.4;
139.4 (2C); 144.7; 148.4; 151.5; 154.7. Mass spectrum, m/z:
377 [M+H]+. Found, %: C 66.88; H 5.10; N 14.66.
C21H20N4O3. Calculated, %: C 67.01; H 5.36; N 14.88.
5-(4-Chlorophenyl)-1,3-dimethyl-6-phenyl-5,8-dihydro-
pyrimido[4,5-d]pyrimidine-2,4,7(1H,3H,6H)-trione (4i).
Yield 88%, mp 226–227°C. IR spectrum ν, cm–1: 3325,
1715, 1678. 1H NMR spectrum, δ, ppm (J, HZ): 3.18 (3H, s,
CH3); 3.48 (3H, s, CH3); 5.66 (1H, s, 5-CH); 7.06–7.40
(9H, m, H Ar); 7.65 (1H, s, NH). 13C NMR spectrum,
δ, ppm: 28.5; 31.5; 36.4; 106.3; 125.4; 126.4 (2C); 126.7
(2C); 127.4; 128.2 (2C); 128.7 (2C); 130.4; 136.3; 142.4;
144.5; 149.8; 153.4. Mass spectrum, m/z: 397 [M+H]+.
Found, %: C 60.32; H 4.18; N 14.02. C20H17ClN4O3.
Calculated, %: C 60.53; H 4.32; N 14.12.
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