Pyrimidines as block units in heterocycles: novel synthesis of pyrimidines and condensed pyrimidine derivatives

Article abstract of DOI:10.1007/s13738-019-01712-4

Compound 1 condensed with benzaldehyde to produce styryl pyrimidine 2. Pyridopyrimidines 5, 8 and 10 resulted from [4 + 2] cycloaddition (condensation) of 1 with malononitrile, ethyl cyanoacetate and/or ethyl acetoacetate. Compound 1 was also concerted to

Full text of DOI:10.1007/s13738-019-01712-4

Journal of the Iranian Chemical Society
https://doi.org/10.1007/s13738-019-01712-4
ORIGINAL PAPER
Pyrimidines as block units in heterocycles: novel synthesis
of pyrimidines and condensed pyrimidine derivatives
1
1
1
2
1
Wesam S. Shehab · Mohamed G. Assy · Hamed Y. Moustafa · Magda H. Abdellattif · Hamdi M. A. Rahman
Received: 8 October 2018 / Accepted: 7 June 2019
©
Iranian Chemical Society 2019
Abstract
Compound 1 condensed with benzaldehyde to produce styryl pyrimidine 2. Pyridopyrimidines 5, 8 and 10 resulted from
[
4+2] cycloaddition (condensation) of 1 with malononitrile, ethyl cyanoacetate and/or ethyl acetoacetate. Compound 1
was also concerted to pyridopyrimidine 14 through multistep reaction (hydrolysis, chlorination, isothiocyanate formation
and intramolecular cyclization). Bromopyrimidine 15 transformed into thiazolopyrimidine 17. Cyclization of bromomethyl
pyrimidine 15 resulted in imidazolopyrimidine 19. Upon reacting the compound 15 with ammonium acetate resulted in
amination aꢀording the amino derivative 20. Oxazolopyrimidine 21 was obtained as the result of the reaction of compound
1
with chloroacetic acid and p-nitrobenzaldehyde. Compound 21 was transformed into pyridopyrimidine 23 and pyridopy-
rimidine of type 25 when reacted with cyanoacetamide and/or phenylhydrazine, respectively. All of the tested compounds
showed good microbial activity against pathogenic microorganisms especially pyridopyrimidine derivative 21.
Keywords Pyridopyrimidines · Thiazolopyrimidine · Bromopyrimidine · Oxazolopyrimidine
Introduction
Because of the wide applicability of these heterocy-
cles, compounds and its novel derivatives encouraged and
enhance the chemists to contribute and synthesize a large
number of biologically active novel drugs and introduce
some easy and eꢂcient methods. From this point, we will
discuss and study new methods of synthesis of new con-
densed pyrimidine derivatives.
Pyrimidines are heterocyclic aromatic products containing
two nitrogen atoms and consider as a great interest because
they constitute an important class of natural and non-natural
products, Pyrimidines are a standout among the most vital
classes of biologically active [1–4]. It is an essential part of
DNA and RNA thus broadly conveyed in living beings [5].
Because of their inclusion as bases in DNA and RNA, they
have turned out to be imperative in the world of manufac-
tured organic chemistry. Over the last decades, condensed
pyrimidine compounds have been reported as antitumor [6,
Experimental
Chemistry
7
], analgesic, antiviral, anti-inꢁammatory [8, 9], anticancer
[
10–14], antimicrobial [15, 16], anti-HIV [17, 18], antineo-
Melting points were measured using an Electrothermal IA
9100 equipment with an open capillary tube and were uncor-
rected. All experiments were done using dry solvents. TLC
was performed on Merck Silica Gel 60F254 with detection
by way of UV light. The formed compounds had been puri-
ꢃed using recrystallization. The IR spectra (KBr disk) were
recorded on a Pye Unicam Sp-3-300 or a Shimadzu FTIR
plastic [19], antitubercular [20, 21], diuretic [22], antago-
nists of the human A A adenosine receptor [23, 24] and
2
calcium-sensing receptor antagonists [25].
*
Wesam S. Shehab
dr.wesamshehab@gmail.com
1
13
8
101 PC infrared spectrophotometer. The H NMR and
C
1
2
Department of Chemistry, Faculty of Science, Zagazig
University, Zagazig 44519, Egypt
NMR spectra were measured on a JEOL-JNM-LA 400 MHz
spectrometer using DMSO-d6 as a solvent. All chemical
shifts had been expressed on the δ (ppm) scale using TMS
as an internal well-known reference. The coupling constant
Chemistry Department, Science Faculty, Deanship
of Scientiꢃc Research, Taif University, Taif,
Kingdom of Saudi Arabia
Vol.:(0
1
123456789)
3

Journal of the Iranian Chemical Society
(
J) values are given in Hz. Analytical information was
7.97 (2H, s, NH exch. with D O), 9.23 (1H, s, NH exch.
2
2
acquired from the Microanalysis center at Cairo University,
Giza, Egypt.
with D O), 12.44 (1H, s, OH exch. with D O). Elemental
2
2
anal. calcd. for C H N O (431.45): C, 66.81; H, 4.91; N,
2
4
21
3
5
9
.74%. Found: C, 66.72; H, 4.86; N, 9.67%.
Ethyl 6‑methyl‑2‑oxo‑4‑phenyl‑1,2,3,4‑tetrahydropyrimi‑
dine‑5‑carboxylate (1) A mixture of ethyl acetoacetate
E t h y l 8 ‑ a m i n o ‑ 1 ‑ o x o ‑ 3 , 6 ‑ d i p h e n y l ‑ 2 , 3 ‑ d i h y ‑
dro‑1H‑pyrido[1,2‑c]pyrimidine‑4‑carboxylate (8) A mix-
ture of compound 2 (3.48 g, 10 mmol), ethyl cyanoacetate
(1.13 g, 10 mmol), sodium acetate (1.23 g, 15 mmol) and
(
(
1.30 g, 10 mmol), benzaldehyde (1.06 g, 10 mmol), urea
0.60 g, 10 mmol) and 4 drop conc. HCl in ethanol (20 ml)
was reꢁuxed for 8 h. After cooling at room temperature, the
formed precipitate ꢃltered oꢀ, then collected and recrys-
tallized from ethanol to aꢀord a pure white powder [26];
3 ml of Ac O in acetic acid (25 ml) was reꢁuxed for 16 h.
2
After cooling at room temperature, the formed precipitate
−
1
yield, 81%; MP: 204–205 °C; IR (KBr, cm ): 3244 (NH),
ꢃltered oꢀ, then collected and recrystallized from ethanol/
3
113 (NH), 1724 (C=O ester), 1701 (C=O pyrimidine ring),
water (50:50) to aꢀord a pure light brown; yield, 90%; MP:
1
−1
1
219 (C‒O). H-NMR (DMSO-d , 400 MHz) δ: 1.11 (3H, t,
178–179 °C; IR (KBr, cm ): 3236 (NH), 3086 (NH ), 1685
6
2
1
J=8 Hz, CH CH ), 2.25 (3H, s, CH ), 4.00 (2H, q, J=8 Hz,
(C=O), 1639 (C=O). H-NMR (DMSO-d , 400 MHz) δ:
2
3
3
6
CH CH ), 5.15 (1H, s, Ph‒CH), 7.22‒7.34 (5H, m, ArH’s),
1.18 (3H, t, J = 8 Hz, CH CH ), 4.07 (2H, q, J = 8 Hz,
2
3
2
3
7
.73 (1H, s, NH exch. with D O), 9.19 (1H, s, NH exch. with
CH CH ), 5.27 (1H, s, Ph‒CH), 7.27‒7.92 (11H, m,
2
2 3
D O). Elemental anal. calcd. for C H N O (260.29): C,
ArH’s, oleꢃnic proton), 7.96 (2H, s, NH exch. with D O),
2 2
2
14 16
2
3
6
1
4.60; H, 6.20; N, 10.76%. Found C, 64.48; H, 6.07; N,
9.23 (1H, s, NH exch. with D O). Elemental anal. calcd.
2
0.71%.
for C H N O (387.44): C, 71.30; H, 5.46; N, 10.85%.
2
3
21
3
3
1
3
Found: C, 71.18; H, 5.39; N, 10.78%. C-NMR (DMSO-
Ethyl 2‑oxo‑4‑phenyl‑6‑styryl‑1,2,3,4‑tetrahydropyrimi‑
dine‑5‑carboxylate (2) A mixture of compound 1 (2.78 g,
d , 100 MHz) δ: 165.6, 153.0, 145.0, 144.7, 136.3, 135.2,
6
133.9, 131.2, 129.6, 129.4, 129.0, 127.9, 127.6, 126.7,
1
0 mmol), benzaldehyde (1.06 g, 10 mmol) and catalyst
120.0, 102.5, 60.3, 54.4 and 14.4.
(
6.48 g ferric chloride powder) in acetonitrile (20 ml) was
reꢁuxed for 16 h. After cooling at room temperature, the
formed precipitate ꢃltered oꢀ, then collected and recrystal-
lized from ethanol/water (50:50) to aꢀord a pure beige pow-
Ethyl 7‑acetyl‑8‑hydroxy‑1‑oxo‑3,6‑diphenyl‑2,3‑dihy‑
dro‑1H‑pyrido[1,2‑c]pyrimidine‑4‑carboxylate (10) A mix-
ture of compound 2 (3.48 g, 10 mmol), ethyl acetoacetate
(1.30 g, 10 mmol), sodium acetate (1.23 g, 15 mmol) and
−1
der [27]; yield 88%; MP: 189–190 °C; IR (KBr, cm ): 3402
1
(
NH), 3244 (2NH), 1685 (C=O), 1639 (C=O). H-NMR
3 ml of Ac O in acetic acid (25 ml) was reꢁuxed for 16 h.
2
(
DMSO-d , 400 MHz δ: 1.18 (3H, t, J = 8 Hz, CH CH ),
After cooling at room temperature, the formed precipitate
ꢃltered oꢀ, then collected and recrystallized from ethanol/
water (50:50) to aꢀord a pure white powder; yield, 88%;
6
2
3
4
7
.07 (2H, q, J = 8 Hz, CH CH ), 5.27 (1H, s, Ph‒CH),
2 3
.27‒7.92 (12H, m, ArH’s, oleꢃnic proton), 7.96 (1H, s, NH
−
1
exch. with D O), 9.23 (1H, s, NH exch. with D O). Elemen-
MP: 165–166 °C; IR (KBr, cm ): 3304‒3232 br. (OH &
2
2
1
tal anal. calcd. for C H N O (348.40): C, 72.40; H, 5.79;
NH), 1685 (C=O), 1639 (C=O), 1597 (acid C=O). H-NMR
2
1
20
2
3
1
3
N, 8.04%. Found: C, 72.28; H, 5.66; N, 8.10%. C-NMR
(DMSO-d , 400 MHz) δ: 1.18 (3H, t, J =8 Hz, CH CH ),
6
2
3
(
DMSO-d , 100 MHz) δ: 165.7, 153.0, 144.9, 144.6, 136.3,
2.51 (3H, s, CH ), 4.07 (2H, q, J=8 Hz, CH CH ), 5.27 (1H,
6
3 2 3
1
1
35.2, 129.6, 129.4, 129.0, 128.8, 128.7, 127.6, 126.7,
s, Ph‒CH), 7.27‒7.96 (11H, m, ArH’s, oleꢃnic proton),
9.23 (1H, s, NH), 12.34 (1H, s, OH). Elemental anal. calcd.
for C H N O (430.46): C, 69.76; H, 5.15; N, 6.51%.
02.5, 60.3, 54.4 and 14.4.
2
5
22
2
5
8
‑Amino‑4‑(ethoxycarbonyl)‑1‑oxo‑3,6‑diphenyl‑2,3‑di‑
Found: C, 69.64; H, 5.11; N, 6.43%.
hydro‑1H‑pyrido[1,2‑c]pyrimidine‑7‑carboxylic acid (5) A
mixture of compound 2 (3.48 g, 10 mmol), malononitrile
4‑Phenyl‑7‑thioxo‑4,6,7,8‑tetrahydropyrido[4,3‑d]pyrim‑
idine‑2,5(1H,3H)‑dione (14) 6-Methyl-2-oxo-4-phenyl-
1,2,3,4-tetrahydro pyrimidine-5-carboxylic acid (2.32 gm,
10 mol) and 16 ml of thionyl chloride were left on reꢁux for
35 mints on a water bath [28–30]. The mixture was heated
on a water bath to remove the unreacted thionyl chloride.
The formed acid chloride was treated with ammonium
isothiocyanate (0.76 gm, 10 mol) in dioxane (25 ml) and
then was reꢁuxed for 6 h. After cooling at room tempera-
ture, the formed precipitate ꢃltered oꢀ, then collected and
recrystallized from acetone to aꢀord compound 14. Light
(
0.66 g, 10 mmol), sodium acetate (1.23 g, 15 mmol) and
3
ml of Ac O in acetic acid (25 ml) was reꢁuxed for 16 h.
2
After cooling at room temperature, the formed precipitate
ꢃltered oꢀ, then collected and recrystallized from ethanol/
water (50:50) to aꢀord a pure beige powder; yield, 90%;
−
1
MP: 177–178 °C; IR (KBr, cm ): 3394‒3086 br. (OH, NH
and NH ), 1685 (C=O), 1639 (C=O), 1507 (acid C=O).
2
1
H-NMR (DMSO-d , 400 MHz) δ: 1.18 (3H, t, J = 8 Hz,
6
CH CH ), 4.07 (2H, q, J = 8 Hz, CH CH ), 5.27 (1H, s,
2
3
2
3
Ph‒CH), 7.29‒7.92 (11H, m, ArH’s, olefinic proton),
1
3

Journal of the Iranian Chemical Society
Brown powder; yield, 73%; MP: 289–290 °C; IR (KBr,
(DMSO-d , 400 MHz) δ: 1.14 (3H, t, J=8 Hz, CH CH ),,
6 2 3
−
1
1
cm ): 3390‒3244 3(NH), 1693 br. 2 (C = O). H-NMR
4.06 (2H, q, J=8 Hz, CH CH ), 5.18 (1H, d, J=4 Hz, CH
2 3
(
DMSO-d , 400 MHz) δ: 2.51 (2H, s, CH ), 5.54 (1H,
pyrimidine ring), 5.22 (1H, d, J=4 Hz, Ph‒CH), 7.30‒7.86
(6H, m, ArH’s, oleꢃnic proton), 9.23 (1H, s, NH), 9.32 (1H,
s, NH). Elemental anal. calcd. for C H N O (301.30): C,
6
2
s, CH Ph), 7.29‒7.40 (5H, m, ArH’s), 8.00 (1H, s, NH),
8
.10 (1H, s, NH), 8.25 (1H, s, NH). Elemental anal. calcd.
1
5
15
3
4
for C H N O S (273.31): C, 57.13; H, 4.06; N, 15.37%.
59.80; H, 5.02; N, 13.95%. Found: C, 59.73; H, 5.06; N,
1
3
11
3
2
Found: C, 57.06; H, 4.01; N, 15.29; %.
13.90%.
Ethyl 6‑(bromomethyl)‑2‑oxo‑4‑phenyl‑1,2,3,4‑tetrahydro‑
Ethyl 6‑(aminomethyl)‑2‑oxo‑4‑phenyl‑1,2,3,4‑tetrahydro‑
pyrimidine‑5‑carboxylate (20) A mixture of compound 15
(3.39 g, 10 mmol) and ammonium acetate (0.77 g, 10 mmol)
in ethanol (20 ml) was reꢁuxed for 8 h. After cooling, the
mixture was poured into water. The formed precipitate ꢃl-
tered oꢀ, then collected and recrystallized from ethanol to
aꢀord a pure white powder; yield, 73%; MP: 180–181 °C;
pyrimidine‑5‑carboxylate (15) The compound 1 (2.78 g,
1
0 mmol) with 20 ml of glacial acetic acid was placed in
a 250-ml ꢁask, and then, 1.59 g (10 mmol, 0.498 ml) of
bromine in 10 ml glacial acetic acid was added slowly to the
ꢁ
ask under stirring. The temperature was maintained to be
from 0 to 5 C. After cooling at room temperature, the mix-
ture was poured into 450 ml water. The formed precipitate
ꢃltered oꢀ, then collected and recrystallized from ethanol to
aꢀord the target compound [31]. White powder; yield, 85%;
−
1
IR (KBr, cm ): 3371 (NH), 3205 (NH), 3097 (NH ), 1701
2
1
(C=O), 1685 (C=O). H-NMR (DMSO-d , 400 MHz) δ:
6
1.11 (3H, t, J=8 Hz, CH CH ), 2.5 (2H, s, CH ),4.07 (2H,
2
3
2
−
1
MP: 149–150 °C; IR (KBr, cm ): 3379 (NH), 3213 (NH),
q, J=8 Hz, CH CH ), 5.18 (1H, s, Ph‒CH), 7.23‒7.94 (7H,
2 3
1
1
685 (C=O), 1635 (C=O). H-NMR (DMSO-d6, 400 MHz)
m, ArH’s, NH proton), 8.01 (1H, s, NH exch. with D O),
2 2
δ: 1.14 (3H, t, J = 8 Hz, CH CH ), 4.07 (2H, q, J = 8 Hz,
9.77 (1H, s, NH exch. with D O). Elemental anal. calcd.
2
3
2
CH CH ), 4.66 (2H, d–d, J=8 Hz, J=8 Hz, CH ), 5.19 (1H,
for C H N O (275.31): C, 61.08; H, 6.22; N, 15.26%.
2
3
2
14 17
3
3
1
3
s, Ph‒CH), 7.23‒8.01 (5H, m, ArH’s,), 9.46 (1H, s, NH),
Found: C, 61.01; H, 6.16; N, 15.19%. C-NMR (DMSO-
9
.77 (1H, s, NH). Elemental anal. calcd. for C H BrN O
d , 100 MHz) δ: 164.6, 152.3, 146.8, 143.8, 129.1, 128.3,
1
4
15
2
3
6
(
339.19): C, 49.58; H, 4.46; N, 8.26%. Found: C, 49.48; H,
126.6, 99.1, 61.22, 54.0, 32.0 and 14.22.
4
.37; N, 8.17.
Ethyl 3‑hydroxy‑7‑(4‑nitrostyryl)‑5‑phenyl‑5H‑oxazolo[3,2‑a]
pyrimidine‑6‑carboxylate (21) A mixture of compound 1
(2.78 g, 10 mmol), p-nitrobenzaldehyde (1.55 g, 10 mmol),
chloroacetic acid (0.94 g, 10 mmol), sodium acetate (1.23 g,
E t h y l 3 , 5 ‑ d i o x o ‑ 7 ‑ p h e n y l ‑ 5 , 6 , 7 , 8 ‑ t e t r a h y ‑
dro‑3H‑thiazolo[3,4‑c]pyrimidine‑8‑carboxylate (17) A
mixture of compound 15 (3.39 g, 10 mmol) and ammo-
nium thiocyanate (0.76 g, 10 mmol) in butanol (25 ml) was
reꢁuxed for 8 h. After cooling, the mixture was poured into
water. The formed precipitate ꢃltered oꢀ, then collected
and recrystallized from ethanol/water (50:50) to aꢀord a
pure light yellow powder; yield, 67%; MP: 161–163 °C; IR
15 mmol) and 3 ml of Ac O in acetic acid (25 ml) was
2
reꢁuxed for 12 h. After cooling, the mixture was poured
into water. The formed precipitate ꢃltered oꢀ, then collected
and recrystallized from ethanol to aꢀord a pure light yellow
−1
powder; yield, 79%; MP: 192–194 °C; IR (KBr, cm ): 3244
−
1
1
(
(
KBr, cm ): 3309 (NH), 1701 (C=O), 1685 (C=O), 1639
br. (OH), 1724 (C=O) 1222 (C‒O). H-NMR (DMSO-d6,
1
C=O). H-NMR (DMSO-d , 400 MHz) δ: 1.28 (3H, t,
400 MHz) δ: 1.11 (3H, t, J=8 Hz, CH CH ), 4.00 (2H, q,
6
2
3
J=8 Hz, CH CH ), 4.16 (2H, q, J=8 Hz, CH CH ), 5.16
J=8 Hz, CH CH ), 5.14 (1H, s, Ph‒CH), 7.23‒7.72 (12H,
2
3
2
3
2 3
(
1H, d, J=4 Hz, CH pyrimidine ring), 5.21 (1H, d, J=4 Hz,
m, ArH’s, Oleꢃnic 3 protons), 9.18 (1H, s, OH exch. with
D O). Elemental anal. calcd. for C H N O (433.42): C,
Ph‒CH), 7.17‒7.79 (6H, m, ArH’s, oleꢃnic proton), 9.18
2
23 19
3
6
(
(
1H, s, NH). Elemental anal. calcd. for C H N O S
63.74; H, 4.42; N, 9.70. Found: C, 63.71; H, 4.32; N, 9.65%.
1
5
14
2
4
1
3
318.35): C, 56.59; H, 4.43; N, 8.80%. Found: C, 56.49; H,
C-NMR (DMSO-d , 100 MHz) δ: 165.8, 152.5, 148.8,
6
4
.37; N, 8.75%.
145.3, 128.8, 128,6, 128.0, 127.9, 127.7, 127.0, 126.7,
26.5, 126.0, 119.1, 99.7, 59.6, 54.4, 18.2 and 14.5.
1
Ethyl 3,5‑dioxo‑7‑phenyl‑2,3,5,6,7,8‑hexahydroimidazo‑
1,5‑c]pyrimidine‑8‑carboxylate (19) A mixture of com-
pound 15 (3.39 g, 10 mmol) and potassium cyanate (0.81 g,
[
Ethyl 10‑amino‑3‑hydroxy‑8‑(4‑nitrophenyl)‑5‑phe‑
nyl‑5H,11aH‑oxazolo[3,2‑a]pyrido[1,2‑c]pyrimidine‑6‑car‑
boxylate (23) A mixture of compound 21 (4.33 g, 10 mmol),
cyanoacetamide (0.84 g, 10 mmol) and sodium hydroxide
(0.39 g, 10 mmol) ethanol (25 ml) was reꢁuxed for 8 h. After
1
0 mmol) in butanol (25 ml) was reꢁuxed for 8 h. After
cooling, the mixture was poured into water. The formed pre-
cipitate ꢃltered oꢀ, then collected and recrystallized from
ethanol/water (50:50) to aꢀord a pure white powder; yield,
cooling, the mixture was poured into HCl/H O (1:10). The
2
−
1
6
5%; MP: 207–208 °C; IR (KBr, cm ): 3397 (NH), 3240
formed precipitate ꢃltered oꢀ, then collected and recrystal-
1
(
NH), 1701 (C=O), 1685 (C=O), 1639 (C=O). H-NMR
lized from ethanol/water (50:50) to aꢀord a pure light yellow
1
3

Journal of the Iranian Chemical Society
−
1
powder; yield, 60%; m.p.: 214–216 °C; IR (KBr, cm ):
bacteria as stock cultures in the microbiology laboratory,
Faculty of Science, Zagazig University. The nutrient agar for
antibacterial was Müller–Hington agar (30.0% beef extract,
1.75% casein hydrolysate, 0.15% starch and 1.7% agar) for
antifungal (3% sucrose, 0.3% NaNO , 0.1% K HPO , 0.05%
3
244 br. (OH), 3113 (NH ), 1701 (C=O) 1222 (C‒O).
2
1
H-NMR (DMSO-d6, 400 MHz) δ: 1.11 (3H, t, J = 8 Hz,
CH CH ), 4.00 (2H, q, J = 8 Hz, CH CH ), 5.15 (1H, s,
2
3
2
3
Ph‒CH), 5.3 (1H, s, pyrimidine ring proton), 7.23‒7.34
3
2
4
(
12H, m, ArH’s, Oleꢃnic 3 protons), 7.73 (2H, s, NH exch.
KCl, 0.001% FeSO , 2% agar–agar) [33] were prepared and
2
4
ο
with D O), 9.18 (1H, s, OH exch. with D O). Elemental anal.
then cooled to 47 C and seeded with tested microorganisms.
2
2
calcd. for C H N O (474.47): C, 63.29; H, 4.67; N, 11.81.
After solidiꢃcation, 5 mm diameter holes were punched by a
sterile cork borer. The investigated compounds, i.e., ligands
and their complexes, were introduced in holes (only 100 μL)
after being dissolved in DMSO at 10–3 M. These culture
25
22
4
6
13
Found: C, 63.19; H, 4.61; N, 11.71%. C-NMR (DMSO-d ,
6
1
1
6
00 MHz) δ: 165.8, 165.7, 152.6, 148.7, 145.1, 144.6, 136.3,
35.2, 129.4, 129.0, 128.8, 128.0, 127.6, 126.6, 102.5, 99.8,
0.3, 59.7, 54.4, 18.1 and 14.4.
ο
plates were then incubated at 37 C for 20 h for bacteria and
ο
for 5 days at 30 C for fungi. The activity was determined
3
‑ H y d r o x y ‑ 8 ‑ ( 4 ‑ n i t r o p h e n y l ) ‑ 5 ‑ p h e ‑
nyl‑7‑(phenylamino)‑5,7‑dihydro‑6H‑oxazolo[3,2‑a]
by measuring the diameter of the inhibition zone (in mm).
Microbial growth inhibition was calculated with reference
to the positive control, i.e., cefotaxime and amoxicillin/cla-
vulanic. The micro-dilution broth susceptibility assay was
used for the evaluation of the minimal inhibitory concentra-
pyrido[4,3‑d]pyrimidin‑6‑one (25) A mixture of compound
2
1 (4.33 g, 10 mmol), phenylhydrazine (1.08 g, 10 mmol),
sodium acetate (1.23 g, 15 mmol) and 3 ml of Ac O in acetic
2
ο
acid (25 ml) was reꢁuxed for 8 h. After cooling, the mixture
was poured into water. The formed precipitate ꢃltered oꢀ,
then collected and recrystallized from ethanol/water (50:50)
to aꢀord a pure light yellow powder; yield, 80%; m.p.: 228–
tion (MIC). After incubation at 37 C for 24 h, the ꢃrst tube
without turbidity was determined as the MIC.
−
1
2
30 °C; IR (KBr, cm ): 3444 br. (OH), 3298 (NH), 1693
Results and discussion
1
(
C=O) 1265 (C‒O). H-NMR (DMSO-d , 400 MHz) δ:
6
5
2
.15 (1H, s, Ph‒CH), 6.82‒8.24 (16H, m, ArH’s, Oleꢃnic
The present work shows an eꢂcient route to synthesize
condensed pyrimidines from pyrimidine of activated
methyl function. The synthesis of methylpyrimidine of
type 1 was carried out using a multicomponent reaction of
Biginelli-typed of benzaldehyde, urea and ethyl acetoac-
etate (Scheme 1) [26]. Compound 1 showed absorption
protons), 10.33 (H, s, NH exch. with D O), 10.89 (1H, s,
2
OH exch. with D O). Elemental anal. calcd. for C H N O
2
27 19
5
5
(
493.48): C, 65.72; H, 3.88; N, 14.19. Found: C, 65.65; H,
1
3
3
1
1
1
.81; N, 14.12%. C-NMR (DMSO-d , 100 MHz) δ: 146.4,
6
45.7, 144.8, 143.0, 136.9, 136.2, 134.1, 129.1, 128.8,
28.0, 127.6, 127.0, 126.4, 126.0, 124.5, 120.4, 119.2,
13.0, 112.4, 18.2 and 14.5.
−
1
−1
−1
bands at 3244, 3113 cm , 1724 cm and 1701 cm cor-
responding to 2NH and two C=O groups, respectively. Its
1
H NMR spectrum revealed the presence of two downꢃeld
In vitro antimicrobial activities
(D O exchangeable) signals at 9.19 ppm and 7.73 ppm for
2
the 2NH groups in addition to a signal at 5.16 ppm for the
Antimicrobial activity of the prepared compounds was inves-
tigated by a previously reported modiꢃed method of Beecher
and Wong [32], against diꢀerent bacterial and fungal species,
such as E. Coli ATCC11229, listeria ATCC8729, S. aureus
ATCC6538, Salmonella typhi ATCC14028 and Aspergil-
lus niger OC10. The tested microorganisms were isolated
from Egyptian soil and identiꢃed according to the standard
mycological and bacteriological keys for identiꢃcation of
PhCH‒CH system (pyrimidine ring proton).
The compound 1 condensed with benzaldehyde in the
presence of Lewis acid (iron-catalyzed) to form styryl pyrim-
idine 4 (Scheme 1) [27]. Compound 4 showed a stretching
−
1
−1
frequency at 3244 cm for NH in addition 1685 cm and
−
1
1639 cm due to the two C=O of a diꢀerent environment.
1
H NMR analysis revealed the absence of H of pyrimidine
5
in addition to the appearance of two (Exchangeable) signals
Scheme 1 Preparation of styryl pyrimidine-5-carboxylate derivative
1
3

Journal of the Iranian Chemical Society
of 2NH. 13C revealed two downꢃeld signals at 165 and
intramolecular cyclization via the addition of cyclic imino
group to cyano function, oxidation followed by cyanohy-
drolysis and subsequent [1,3H] shift (Scheme 2). Com-
pound 5 produced stretching frequencies at 3236, 1685,
1
53 ppm for the two carbonyl groups.
Malononitrile added its nucleophile’s methylene to the
exocyclic polarized double bond of 2 to furnish pyridopy-
rimidine 5. Compound 5 formed from 2 and malononitrile
through the formation of non-isolable Michael adduct 3,
−
1
1
1639 cm for NH and two C=O groups. The H NMR of
Scheme 2 Heterocyclization of styryl pyrimidine 2 by [4+2] cycloaddition in acidic medium
1
3

Journal of the Iranian Chemical Society
target 5 contained three downꢃeld (D O Exchangeable)
Exchangeable) signals at 9.77 ppm and 8.01 ppm due to
2NH protons.
2
signals for COOH, NH and NH protons.
2
As depicted in (Scheme 2), ethyl cyanoacetate and com-
pounds 2 underwent [4+2] cycloaddition in acidic medium
to furnish compound 8. Compound 8 showed characteris-
The synthesis of oxazolopyrimidine derivative 21 was
performed by reaction of three components at the one-pot
reaction of compound 1, chloroacetic acid and p-nitroben-
zaldehyde in presence of Ac O/CH COONa mixture using
tic stretching frequencies at 3236, 1681 and 1639 for NH
2
3
1
and the two C=O groups. H NMR analysis shows (D O
acetic acid as a solvent (Scheme 5). Compound 21 resonate
2
Exchangeable) signals at δ 9.23 ppm and 7.96 ppm for NH
at high δ value (D O Exchangeable) due to OH group. IR
2
−
1
−1
and NH protons.
showed characteristic peaks at 3244 cm and 1647 cm
2
13
Acidic-mediated cyclocondensation of 2 and ethyl ace-
toacetate produced hydroxyl pyridopyrimidine 10 via path-
way a while rout b not detected (Scheme 2). IR spectrum of
due to OH and C=O groups. C provided a downꢃeld signal
at δ 165 ppm and 152 ppm due to carbonyl carbons of the
diꢀerent electronic environment.
−
1
1
0 displayed characteristic frequencies at 3394 cm broad
[4+2] cycloaddition of cyanoacetamide and 21 generated
pyridopyrimidine 23 (Scheme 5). Compound 23 contained
−1
−1
(
OH), 1685 cm and 1635 cm due to the two C=O groups.
1
Its H NMR provides two downꢃeld signals at 12.34 ppm
and 9.23 ppm for OH and NH groups, respectively.
a downꢃeld two (D O exchangeable) signals at 7.18 ppm
2
and 7.73 ppm due to OH and NH protons. IR spectrum
2
−
1
−1
Upon hydrolysis treatment of 1 with sodium hydroxide
and subjected the product to thionyl chloride followed by
ammonium thiocyanate resulted in hydrolysis chlorination,
followed by formation of isothiocyanate and subsequent
showed a stretching frequency at 3244 cm , 1705 cm and
−
1
13
1647 cm for NH, CO and C=N groups. C produced a
downꢃeld signal at 165 ppm for C=O group.
Pyrimidine of type 21 was subjected to react with phe-
addition of CH to heteroallene system leading to pyridopy-
nylhydrazine to produce pyridopyrimidine 25. The chemi-
3
rimidine 14 (Scheme 3).
cal shift of protons was located at 10.89 ppm, 10.33 (D O
2
1
Compound 14 provides H NMR spectrum involving
exchangeable) for OH and NH groups. Also, the disappear-
downꢃeld signals for 3NH. Also, the IR spectrum showed a
ance of ester protons potentiates the proposed structure. IR
−
1
−1
13
broad peak at 1693 cm for carbonyl groups.
spectrum showed a signal at 1639 cm for C=O group. C
produced a signal at 196 ppm for CO group.
Brominating of pyrimidine 1 resulted in bromomethyl
pyrimidine 15 (Scheme 4) [31]. Bromomethyl pyrimidine
undergoes substitution reaction with NH SCN in butanol
Screening of antimicrobial activity
4
to produce thiazole-cyclization 17 in addition to the trans-
1
esteriꢃcation. H NMR of 17 revealed signals for NH and
Some synthesized compounds were assessed by screening
them in vitro growth inhibitory activity contrary to the vari-
ety of strains of bacteria and fungi. The susceptibility of
certain strains of bacterium, such as, E. Coli ATCC11229,
Listrea ATCC8729, S. aureus ATCC6538, and Salmonella
typhi ATCC14028 and antifungal screening was studied
against, Aspergillus niger screening were studied against
toward compounds 1, 2, 8, 15, 20 and 21 and judged by
measuring size of the inhibitions diameter (Table 1). The
results of the antibacterial study of these compounds have
inhibitory action against all types of bacteria and fungi
(Fig. 1).
(
PhCH‒CH) system. IR spectrum produces a broadband at
−
1
1
685 cm due to C=O groups.
Upon reꢁuxing the compound 15 and KNC=O resulted
in imidazole cyclization aꢀording imidazolopyrimidine 19
(
Scheme 4). Compound 19 contained two downꢃeld signals
for 2NH in addition to (PhCH‒CH) protons. IR spectrum
−
1
displayed stretching frequency broadband at 1685 cm due
to C=O groups.
Upon dealing bromomethyl pyrimidine 15 with ammo-
nium acetate in reꢁuxing ethanol resulted in debromina-
tion 20, and none of pyrrolopyrimidine was obtained [may
be due to the involvement of carbonyl in ring resonance]
All the tested compounds have antibacterial activity
against Gram-negative (Escherichia coli) and Gram-positive
(
Scheme 4). Compound 20 produced two downꢃeld (D O
2
Scheme 3 Formation of pyridopyrimidine 14
1
3

Journal of the Iranian Chemical Society
Scheme 4 Synthesis of fused pyrimidine derivatives
(
Staphylococcus aureus) bacteria except compound 20
the pathogenic bacteria and fungi showed the most sensitive
pathogens dedicated the minimum inhibitory concentration
(MIC).
which had antibacterial activity against Gram-negative bac-
teria only. Compound 21 showed the highest antibacterial
activity. All the tested compounds had no antifungal activity.
Conclusion
Determination of MIC for the most sensitive
organisms
Our present investigation is centered on the studies of syn-
thesis, reactions, spectral analysis and biological activi-
ties of condensed pyrimidine derivatives. The procedure
proved more beneꢃcial than those previously reported in
the literature. Compound 21 exhibited the most potent
antibacterial. The ꢃndings demonstrate the potential for
condensed pyrimidine derivatives to serve as lead com-
pounds for further development as medicinal agents.
The antimicrobial potency of the synthetic compounds was
determined against the most sensitive bacteria and fungi
(
Table 2 and Fig. 2). The lowest MIC against these com-
pounds recorded the data in (Tables 2, 3, 4, 5, 6). These
results ensured that the activity of synthetic compound 21 on
1
3

Journal of the Iranian Chemical Society
Scheme 5 The synthesis of oxazolopyrimidine and pyridopyrimidine derivatives
Table 1 Averages of inhibition
Compounds
Microorganisms
growth diameter (mm) of the
tested compounds and standards
against selected Gram-positive,
Gram-negative bacteria and one
fungi strain
Fungi
Gram-negative bacteria
Gram-positive bacteria
A. niger
Listeria
E. coli
S. auruas
S. typhi
5+3 ± 0.12
3
6
+1
± 0.14
± 0.24
9
7
3
+3
± 0.28
± 0.24
± 0.11
NA
1
NA
NA
NA
NA
NA
NA
NA
NA
+
3
+3
+3
+1
1
2
8
2
2
5
7.5 ± 0.5
NA
+
+
3
2
+2
+1
1
5
4
± 0.21
± 0.13
4.5 ± 0.19
2
± 0.1
+1
+3
3
4
5
1
± 0.16
± 0.13
± 0.18
7.5 ± 0.23
NA
NA
NA
+2
0
NA
0
9
+
1
+3
NS
+3
3
± 0.11
± 0.3
NS
NS
Amoxicillin/clavulanic
Cefotaxime
1.7
NA
NA
NA
1.4
NA
NA
NA no activity, data are expressed in the form of mean± standard deviation (SD). Statistical signiꢃcance
NS
+1
+2
+3
P
P not signiꢃcant, P < 0.05; P P signiꢃcant, P > 0.05; P P highly signiꢃcant, P > 0.01; P P very
highly signiꢃcant, P > 0.001; student’s t-test (Paired)
1
3

Journal of the Iranian Chemical Society
Fig. 1 Statistical representation
for biological activity of the
prepared compounds
9
8
7
6
5
4
3
2
1
0
listeria
E.coli
S.auruas
S.typhi
A.niger
Tested compounds
Table 3 Of one-way ANOVA:
E. coli versus samples
Table 2 Determination of MIC for the most sensitive organisms
Compounds Mean Grouping
Compounds Listeria
E. coli
S. typhi
S. auraus
2
1
1
8
2
2
0.08
0.08
0.16
0.16
0.16
0.16
A
A
B
B
B
B
5
1
1
2
8
2
2
0.16± 0.012 0.16± 0.02
0.08± 0.011 0.08± 0.01
0.16± 0.025 0.16± 0.025 0.24± 0.031 0.16± 0.025
0
0
0.16± 0.012
0.12± 0.011
5
1
0
1
0.16± 0.033 0.16± 0.03
0.16± 0.01
0.08± 0.01 0.08± 0.02
0
0
0
0.16± 0.033
0
0.12± 0.01
0
0
Means that do not share a letter
are signiꢃcantly diꢀerent
Grouping information using the
Fisher LSD method and 95%
conꢃdence interval
Fig. 2 MIC for the most
sensitive bacteria of the tested
compounds
bacteria
0
0
0
.25
.2
.15
.1
0
Listeria
E.coli
0
S typhi
S.auraus
.05
0
1
15
21
8
20
2
Tested compounds
1
3

Journal of the Iranian Chemical Society
Table 4 Of one-way ANOVA:
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0.16
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A
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B
B
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