Eco-friendly Synthesis of 3-(Aryl)-2,6-diphenylpyrimidin-4(3H)-ones, Ethyl-1-(aryl)-1,6-dihydro-2-(aryl)-6-oxopyrimidine-4-carboxylates and 6-(4-Arylphenyl)-2-isopropylpyrimidin-4(3H)-one

Article abstract of DOI:10.14233/ajchem.2019.21784

In present communication, we report the synthesis of pyrimidin-4(3H)-one derivatives by microwave irradiation in good yields and less reaction time. All titled compounds were characterized by IR, NMR and Mass spectral analyses.

Full text of DOI:10.14233/ajchem.2019.21784

Asian Journal of Chemistry; Vol. 31, No. 4 (2019), 845-850
A
SIAN
J
OURNAL OF HEMISTRY
C
https://doi.org/10.14233/ajchem.2019.21784
Eco-friendly Synthesis of 3-(Aryl)-2,6-diphenylpyrimidin-4(3H)-ones, Ethyl-1-(aryl)-1,6-dihydro-
2-(aryl)-6-oxopyrimidine-4-carboxylates and 6-(4-Arylphenyl)-2-isopropylpyrimidin-4(3H)-one
1
2
1,*
KISHORE KUMAR ANANTOJU , LAXMINARAYANA EPPAKAYALA and THIRUMALA CHARY MARINGANTI
1Jawaharlal Nehru Technological University Hyderabad, Hyderabad-500085, India
2Sreenidhi Institute of Science and Technology (Autonomous), Ghatkesar, Hyderabad-501301, India
*Corresponding author: E-mail: mtcharya@yahoo.com
Received: 29 October 2018;
Accepted: 11 December 2018;
Published online: 27 February 2019;
AJC-19296
In present communication, we report the synthesis of pyrimidin-4(3H)-one derivatives by microwave irradiation in good yields and less
reaction time. All titled compounds were characterized by IR, NMR and Mass spectral analyses.
Keywords: Isopropylpyrimidine, Benzimidines, Isobutyramidine hydrochloride, Microwave reaction.
tumor [12], antineoplastic [13], anti-inflammatory [14], diuretic
[15], antimalaria [16], cardio-vascular [17],etc. In view of the
importance of these compounds we undertook synthesis of
some pyrimidine-4(3H)-one derivatives.
Choosing the environmentally benign conditions and solvents
are as important as, synthesis of biologically active compounds.
By choosing eco-friendly solvent like water or ethanol, we can
minimise the waste producing in reaction or workup. By choosing
the microwave reaction instead of traditional thermal heating,
we can save the power by minimizing the reaction time and also
the volume of solvent. Herein, we reported the synthesis of
microwave-assisted novel pyrimidine derivatives by using eco-
friendly solvent, ethanol.
INTRODUCTION
Heterocyclic compounds present in many of natural products
like vitamins, antibiotics and harmones [1,2]. In biologically
active compounds, pyrimidines are the most active class of
compounds. Pyrimidines are the nitrogen containing hetero-
cyclic aromatic compounds at 1,3-positions. Pyrimidine deriva-
tives are present in our living organisms in the form of nucleic
acid bases like adenine, uracil, thiamine and cytosine. Genetic
information is carried by these nucleic acid bases to synthesize
the various enzymes and proteins.
In the world, tuberculosis (TB) is one of the most effected
mycobacterial disease [3]. In last 40 years, robust new anti-
tuberculosis drugs with less side effects and new mechanisms
of action have not been progressed. The annual infection rate
in the developing countries is 20-50 times more than compare
with the developed countries. It indicates the importance of
synthesis of new antimicrobial drugs with variety of consequences
like less duration of therapy with minimum expenditure and
treatment with single dosage unit [4,5] than the giving multiple
drugs. To overcome these drawbacks, our efforts dedicated on
the development of new antibacterial compounds [6,7]. Pyrimi-
dine derivatives represent an important place in the medicinal
chemistry due to their wide range of biological activities [8,9].
Derivatives of pyrimidines are reported to have different pharma-
cological activities like anti-HIV [10],antitubercular [11], anti-
EXPERIMENTAL
All the chemical and reagents used were purchased from
Aldrich. All the solvents were of analytical grade. Thin-layer
chromatography (TLC) was checked by Merck AL silica gel
60 F254 plates and visualized under UV light. IR spectra were
recorded in KBr pellet with a Shimadzu spectrum gx FTIR
instrument and all the diagnostic, intense peaks are reported.
13
1H NMR and C NMR spectra were recorded in CDCl3 and
DMSO-d6 with a Varian Mercury plus 400 MHz instrument.
All the chemical shifts were reported in δ (ppm) using TMS as
an internal standard. The 1H NMR chemical shifts and coupling
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846 Anantoju et al.
Asian J. Chem.
constants were determined assuming first-order behaviour.
Mass spectra were recorded on a Shimadzu LCMS-QP 1000
mass spectrometer. Melting points were determined in open
glass capillaries on a Stuart SMP30 apparatus and are unco-
rrected. All the reactions were performed under inert atmos-
phere.
2,3,6-Aryl pyrimidin-4(3H)-ones (5a-h): N-Arynyl
benzimidines (3) (1 eq.) and ethyl 3-phenylpropiolate (4a) or
ethyl 3-(4-(trifluoromethyl)phenyl)propiolate (4b) (1.5 eq.) in
EtOH (5 mL) was irradiated in microwave at 150 °C for 2 h.
Reaction mixture was allowed to cooled to room temperature,
resultant solid was filtered and dried. Crude material was puri-
fied by trituration using pentane (Scheme-I).
Ethyl-1,6-dihydro-6-oxo-1,2-diarylpyrimidine-4-car-
boxylate (7a-d): N-arynyl benzimidines (3) (1 eq.) and diethyl
but-2-ynedioate (6) (1.5 eq.) in EtOH (5 mL) was stirred at
room temperature for 1 h. Reaction mixture was diluted with
water, extracted with EtOAc. Organic layer was washed with
water, brine dried over anhhydrous Na2SO4 and concentrated.
Crude material was purified by column chromatography using
40-50 % ethyl acetate in pet.-ether (Scheme-I).
6-Aryl-2-isopropylpyrimidin-4(3H)-ones (9a-b): Iso-
butyramidine hydrochloride (8) (1 eq.), Et3N (1 eq.) and ethyl
3-phenylpropiolate (4a) or ethyl 3-(4-(trifluoromethyl) phenyl)
propiolate (4b) (1.5 eq.) in EtOH (5 mL) was irradiated in
microwave at 150 ºC for 1 h. Reaction mixture was allowed to
cool to room temperature. Resultant solid was filtered and dried
(Scheme-I).
2,3,6-Triphenylpyrimidin-4(3H)-one (5a): White solid,
m.p. 312-315 °C, m.w. 324.38, m.f. C22H16N2O. 1H NMR (500
MHz, CDCl3): δ 6.35 (S, 1H), 6.85-6.87 (m, 2H), 7.05-7.10
(m, 5H), 7.15-7.17 (m, 4H), 7.18-7.2 (m, 2H), 7.25-7.28 (m,
13
2H). C NMR (100 MHz; CDCl3): 112.08, 127.66, 128.13,
128.61, 128.77, 128.84, 129.22, 129.45, 129.49, 133.2, 134.54,
138.62, 154.6, 161.08, 169.86. Mass (M+H): 325.22
3-(4-Fluorophenyl)-2,6-diphenylpyrimidin-4(3H)-one
(5b): Off-white solid, m.p. 314-316 °C, m.w. 342.37, m.f.
C22H15N2OF. IR (KBr, νmax, cm–1): 756, 852, 1159, 1405, 1511,
1652, 2852, 2922, 3058. 1H NMR (400 MHz, CDCl3): δ 6.34
(S, 1H), 6.76 (t, J = 7.6 Hz, 2H), 6.83-6.86 (m, 2H), 7.06-7.07
(d, J = 8.4 Hz, 2H), 7.17-7.24 (m, 5H), 7.26-7.29 (m, 3H). 13C
NMR (100 MHz; CDCl3): 112.08, 115.77, 116.0, 127.8,
R3
O
O
R3
NH
4
NaH, DMSO
CN
R1
NH2
R2
R1
NH
R2
RT, 2h
EtOH, M.W, 150°C, 2h
N
Step-1
Step-2
1
2
R1
N
O
3
R2
O
O
O
EtOH, RT, 2 h
8 examples
5
O
Step-3
6
O
O
R1=
F
O
N
R1
N
O
R2
F
4 examples
R2=
7
F
R3
O
O
F
F
R3
H, CF3
R3=
4
NH
NH2.HCl
N
Et3N, EtOH, M.W, 150°C, 1 h
N
H
O
9
8
Step-4
2 examples
Scheme-I

Vol. 31, No. 4 (2019)
Eco-friendly Synthesis of Pyrimidin-4(3H)-ones 847
128.29, 128.85, 129.14, 129.36, 129.6, 131.17, 131.26, 133.0,
134.36, 134.66, 134.7, 154.63, 160.47, 161.18, 162.97, 169.71.
Mass (M+H): 343.22.
20.99, 112.36, 122.1, 124.81, 125.14, 125.18, 127.7, 129.0,
129.2, 129.35, 129.60, 129.66, 131.06, 131.39, 134.38, 135.66,
136.83, 139.21, 153.31, 161.44, 169.48. Mass (M+H): 407.29.
Ethyl 1,6-dihydro-6-oxo-1,2-diphenylpyrimidine-4-
carboxylate (7a): Yellow solid, m.p. 284-286 °C, m.w. 320.34,
m.f. C19H16N2O3. 1H NMR (500 M Hz, CDCl3): δ 1.02 (t, J =
7.5 Hz, 3H), 4.03-4.07 (q, J = 7 Hz, 2H), 6.62 (s, 1H), 7.11-
7.12 (m, 2H), 7.16-7.19 (m, 2H), 7.24-7.25 (m, 3H), 7.27-
7.32 (m, 3H). Mass (M+H): 321.23.
Ethyl 1-(4-fluorophenyl)-1,6-dihydro-6-oxo-2-phenyl-
pyrimidine-4-carboxylate (7b): Pale brown solid, m.p. 295-
297 °C, m.w. 338.33, m.f. C19H15N2O3F. IR (KBr, νmax, cm–1):
852, 1014, 1216, 1509, 1647, 1740, 2923, 2996, 3050, 3327.
1H NMR (500 MHz, CDCl3): δ 1.11 (t, J = 7 Hz, 3H), 4.08-
4.13 (q, J = 7 Hz, 7.5 Hz, 2H), 6.64 (s, 1H), 6.96-7.0 (m, 2H),
7.1-7.12 (m, 2H), 7.2-7.25 (m, 3H), 7.27-7.3 (m, 2H). Mass
(M+H): 339.23.
Ethyl 1-(2,4-difluorophenyl)-1,6-dihydro-2-(2-methoxy-
phenyl)-6-oxopyrimidine-4-carboxylate (7c): Pale yellow
solid, m.p. 211-213 ºC, m.w. 386.35, m.f. C20H16N2O4F2. 1H NMR
(500 MHz, CDCl3): 1.18 (t, J = 7 Hz) and 1.24 (t, J = 7 Hz)
(together 3 H), 3.52 (s) and 3.69 (s) (together 3 H), 4.15 (q, J
= 7 Hz) and 4.22 (q, J = 7 Hz) (together 2H), 6.55-6.65 (m,
2H), 6.75-6.94 (m, 4H), 7.29-7.3 (m, 1.5 H), 7.39 (d, J = 8
Hz, 0.5 Hz). Mass (M+H): 387.24.
Ethyl 2-(2,4-difluorophenyl)-1-(4-fluorophenyl)-1,6-
dihydro-6-oxopyrimidine-4-carboxylate (7d): Pale brown
solid, 319-321 °C, m.w. 374.31, m.f. C19H13N2O3F3. 1H NMR
(500 MHz, CDCl3): 1.21 (t, J = 7 Hz, 3H), 4.16-4.20 (q, J = 7
Hz, 2H), 6.80-6.83 (m, 3H), 6.92-6.95 (t, J = 8.5 Hz, 2H),
7.12-7.13 (m, 1H), 7.29-7.32 (m, 2H). Mass (M+H): 375.26.
2-Isopropyl-6-phenylpyrimidin-4(3H)-one (9a): Off-
white solid, m.p. 302-304 °C, m.w. 214.26, m.f. C13H14N2O.
IR (KBr, νmax, cm–1):843, 949, 1174, 1231, 1388, 1670, 2974,
3440. 1H NMR (500 MHz, CDCl3): δ 1.4 (d, J = 7 Hz, 6H), 3.07
(m, 1H), 6.79 (s, 1H), 7.46-7.48 (m, 3H), 8.02-8.05 (m, 2H).
13C NMR (125 MHz; CDCl3):20.65, 34.60, 106.76, 127.22, 128.73,
130.68, 136.68, 163.28, 166.25, 166.31. Mass (M+H): 215.23.
6-(4-(Trifluoromethyl)phenyl)-2-isopropylpyrimidin-
4(3H)-one (9b): Pale brown solid, m.p. 204-206 °C, m.w. 282.26,
m.f. C14H13N2OF3. IR (KBr, νmax, cm–1): 835, 1115, 1326, 1667,
2974, 3144, 3438. 1H NMR (400 MHz, CDCl3): δ 1.43 (d, J =
6.8 Hz, 6H), 3.0-3.07 (m, 1H), 6.81 (s, 1H), 7.73 (d, J = 8.4 Hz,
2H), 8.13 (d, J = 8.4 Hz, 2H), 12.36 (br, 1H). 13C NMR (100
MHz; CDCl3): 20.58, 34.6, 107.88, 125.63, 127.52, 132.11,
132.43, 139.99, 161.73, 166.02, 166.77. Mass (M+H): 283.11.
3-(2,4-Difluorophenyl)-2-(2-methoxyphenyl)-6-phenyl-
pyrimidin-4(3H)-one (5c): White solid, m.p. 221-224 °C, m.w.
390.38, m.f. C23H16N2O2F2. IR (KBr, νmax, cm–1): 851, 954, 1106,
1
1256, 1383, 1498, 1655, 2842, 2932, 3072. H NMR (500
MHz, CDCl3): (Rotamers): 3.49 (s) and 3.68 (s) (together 3H),
6.33 (s) and 6.37 (s) (together 1H), 6.47-6.62 (m, 3H), 6.89 (t,
J = 7 Hz, 1H), 6.94-7.03 (m, 1H), 7.15 (d. J = 7 Hz, 2H),
7.21-7.29 (m, 3.5 H), 7.26-7.36 (d, J = 5 Hz, 1H), 7.48 (d, J =
7.5 Hz, 0.5 H). Mass (M+H): 391.28.
2,6-Diphenyl-3-p-tolylpyrimidin-4(3H)-one (5d): Pale
brown solid, m.p. 324-326 °C, m.w. 338.40, m.f. C23H18N2O.
1H NMR in (400 MHz, CDCl3): δ 2.19 (s, 3H), 6.33 (s, 1H),
6.71-6.73 (d, J = 8.4 Hz, 2H), 6.84-6.86 (d, J = 8.4 Hz, 2H),
7.05-7.07 (d, J = 8.8 Hz, 2H), 7.18-7.24 (m, 6H), 7.28-7.30
(d, J = 8.4 Hz, 2H). 13C NMR (100 MHz; CDCl3): 20.94,
112.03, 127.6, 128.07, 128.81, 129.06, 129.12, 129.19, 129.33,
129.38, 133.29, 134.65, 135.96, 138.69, 154.78, 161.23,
169.92. Mass (M+H): 339.26.
6-(4-(Trifluoromethyl)phenyl)-2,3-diphenylpyrimidin-
4(3H)-one (5e): White solid, m.p. 334-336 °C, m.w. 392.37,
m.f. C23H15N2OF3. IR (KBr, νmax, cm–1): 850, 1127, 1328, 1410,
1652, 2917, 3058, 3441. 1H NMR (400 MHz, CDCl3): δ 6.33
(s, 1H), 6.88 (d, J = 8 Hz, 2H), 7.10-7.18 (m, 5H), 7.22-7.25 (m,
3H), 7.28-7.30 (m, 2H), 7.47 (d, J = 8 Hz, 2H). 13C NMR (100
MHz; CDCl3): 112.28, 122.05, 124.76, 125.12, 125.15, 127.7,
129, 129.03, 129.18, 129.39, 129.63, 131.08, 131.41, 131.74,
134.23, 136.69, 138.28, 153.22, 161.32, 169.45. Mass (M+H):
393.32.
6-(4-(Trifluoromethyl)phenyl)-3-(4-fluorophenyl)-2-
phenylpyrimidin-4(3H)-one (5f): Off-white solid, m.p. 344-
346 °C, m.w. 410.36, m.f. C23H14N2OF4. IR (KBr, νmax, cm–1):
1
851, 1126, 1328, 1409, 1504, 1653, 2922, 3061, 3450. H
NMR (400 MHz, CDCl3): δ 6.31 (s, 1H), 6.77-6.82 (m, 2H),
6.89-6.93 (m, 2H), 7.16-7.20 (m, 3H), 7.29-7.74 (m, 4H), 7.5-
7.52 (d, J = 8 Hz, 2H). Mass (M+H): 411.25.
6-(4-(Trifluoromethyl)phenyl)-3-(2,4-difluorophenyl)-
2-(2-methoxyphenyl)pyrimidin-4(3H)-one (5g): white solid,
m.p. 239-241 °C, m.w. 458.38, m.f. C24H15N2O2F5. 1H NMR
(500 MHz at 100 °C, DMSO-d6): δ 3.6 (s, 3H), 6.2 (s, 1H), 6.76-
6.81 (m, 2H), 6.90-6.95 (m, 2H), 7.28 (t, J = 7.5 Hz, 1H), 7.39-
7.4 (m, 2H), 7.5 (d, J = 8 Hz, 2H), 7.62 (d, J = 8 Hz, 2H).13C
NMR (100 MHz; CDCl3) (Rotamers): 54.49, 55.11, 103.71,
103.95, 104.2, 104.44, 109.94, 110.23, 110.9, 111.16, 111.89,
111.96, 120.53, 121.96, 122.36, 122.48, 123.32, 123.42, 124.67,
125.07, 125.48, 125.51, 128.77, 128.88, 129.27, 130.36, 130.8,
130.9, 131.45, 131.66, 131.71, 131.84, 131.93, 135.98, 152.69,
152.91, 154.81, 155.22, 155.9, 158.28, 158.41, 160.42, 160.56,
161.67, 169.47. Mass (M+H): 459.28
RESULTS AND DISCUSSION
Herein, we report a new synthesis method of pyrmidinone
derivatives devoid of catalyst/reagent with less reaction time
and quantitative yield. We achieved good yield for pyrimidinoe
derivatives by condensation followed by cyclization of ethyl-
3-phenylpropiolate or diethylacetylene dicarboxylate with N-
phenylbenzimidine or isobutyramidine (Table-1). All the
reactions are carried out in environmentally benign solvent
EtOH.Although several reports available for the title molecules
(5a-h) in reagent free condition, the reaction takes place in
4-12 days [18]. Here we drastically reduced the reaction time
6-(4-(Trifluoromethyl)phenyl)-2-phenyl-3-p-tolyl-
pyrimidin-4(3H)-one (5h): Off-white solid, m.p. 302-304 °C,
m.w. 406.40, m.f. C24H17N2OF3. IR (KBr, νmax, cm–1): 850, 1129,
1
1321, 1411, 1539, 1655, 2920, 3055. H NMR (300 MHz,
CDCl3): δ 2.19 (s, 3H), 6.31 (s, 1H), 6.74 (d, J = 8.4 Hz, 2H),
6.88 (d, J = 8.1 Hz 2H), 7.17-7.25 (m, 5H), 7.29 (d, J = 8.4
Hz, 2H), 7.47 (d, J = 8.1 Hz, 2H). 13C NMR (100 MHz; CDCl3):

848 Anantoju et al.
Asian J. Chem.
TABLE-1
Entry-1
Entry-2
Product
Isolated yields (%)
NH
O
O
N
N
NH
81
O
4a
3a
5a
NH
NH
O
O
N
N
79
O
4a
F
3b
5b
F
O
NH
O
O
NH
O
N
N
F
84
O
F
4a
3c
F
5c
F
NH
NH
O
O
N
N
85
O
4a
3e
5d
CF3
NH
NH
O
O
F3C
N
75
4b
N
O
3a
5e
CF3
NH
NH
O
O
N
F3C
72
N
F
O
4b
3b
F
5f
from 4-12 days to 1 to 2 h by micro wave irradiation. The
reaction of ethyl-3-phenylpropiolate with N-phenylbenza-
midine or isobutyramidine, required product is precipitated
after the reaction is completed, we can get the pure compound
by simple filtration. So that we can avoid the environmentally
harmful solvents for column chromatography. Reaction of

Vol. 31, No. 4 (2019)
Eco-friendly Synthesis of Pyrimidin-4(3H)-ones 849
CF3
O
NH
NH
O
O
F3C
O
N
F
70
N
O
F
4b
3c
F
5g
F
CF3
NH
O
O
NH
F3C
N
88
4b
N
O
3e
5h
O
O
NH
NH
N
O
O
O
O
N
O
55
51
6
3a
7a
O
N
O
NH
NH
O
O
O
O
N
F
O
6
3b
F
7b
O
N
O
O
NH
O
O
O
O
O
NH
N
F
O
F
F
45
6
3c
F
7c
O
O
F
NH
F
N
O
O
O
O
NH
N
O
42
72
74
F
6
F
3d
F
7d
F
NH
NH2·HCl
O
O
N
4a
8
N
H
9a
O
CF3
NH
NH2·HCl
O
O
F3C
N
4b
8
N
H
O
9b

850 Anantoju et al.
Asian J. Chem.
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CONFLICT OF INTEREST
The authors declare that there is no conflict of interests
regarding the publication of this article.
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