Synthesis and antimicrobial activities of some novel pyrido[2,3-d] pyrimidine derivatives

Article abstract of DOI:10.1080/10426500802095764

2-Amino-(6-phenoxathiin-2-yl)-4-phenyl-nicotinonitrile has been synthesized and used as a starting material to construct a novel series of annulated and substituted pyrido[2,3-d]pyrimidine systems. Antibacterial and antifungal activities of some synthesiz

Full text of DOI:10.1080/10426500802095764

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Phosphorus, Sulfur, and Silicon
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Synthesis and Antimicrobial
Activities of Some Novel
Pyrido[2,3- d ]pyrimidine
Derivatives
M. S. Behalo a
a Chemistry Department, Faculty of Science, Benha
University, Benha, Egypt
Version of record first published: 19 Dec 2008
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Some Novel Pyrido[2,3- d ]pyrimidine Derivatives, Phosphorus, Sulfur, and Silicon and
the Related Elements, 184:1, 206-219
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Phosphorus, Sulfur, and Silicon, 184:206–219, 2009
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500802095764
Synthesis and Antimicrobial Activities of Some Novel
Pyrido[2,3-d]pyrimidine Derivatives
M. S. Behalo
Chemistry Department, Faculty of Science, Benha University,
Benha, Egypt
2-Amino-(6-phenoxathiin-2-yl)-4-phenyl-nicotinonitrile has been synthesized and
used as a starting material to construct a novel series of annulated and substituted
pyrido[2,3-d]pyrimidine systems. Antibacterial and antifungal activities of some
synthesized compounds were evaluated and reported.
Keywords Antimicrobial activity; phenoxathiin; pyrido[2,3-d]pyrimidines
INTRODUCTION
In recent years considerable attention has been devoted to the synthe-
sis of pyridopyrimidine derivatives, as they possess such diverse phar-
macological properties as antitumor,1–5 antibacterial,6,7 antifolate,8,9
analgesic,10,11 and antifungal.12 Aminopyrido[2,3-d]pyrimidine deriva-
tives are also used as adenosine receptor antagonists.15–17 In addition,
phenoxathiin derivatives were found to be useful for the treatment of
microbial infections,18 asthmatic, and inflammatory conditions.19 Also,
phenoxathiins were found to be active as potential antihypertensive20
and antitumor agents.21 Several phenoxathiin pyridinium derivatives
acted as effective antifungal agents against Aspergillus and Candida.22
Considering the above reports in conjunction with our previous work
on the synthesis of phenoxathiin derivatives as antimicrobial agents,23
we thought it would be of interest to combine the above mentioned
heterocycles in a molecular framework to investigate a possible additive
effect of these rings regarding biological activity.
Received 17 November 2007; accepted 19 March 2008.
All strains were kindly supplied from the Botany Department, Faculty of Science,
Benha University, Egypt.
Address correspondence to M. S. Behalo, Chemistry Department, Faculty of Science,
Benha University, Egypt. E-mail: mohamedbehalo@hotmail.com
206

Pyrido[2,3-d]pyrimidines
207
RESULTS AND DISCUSSION
Chalcone 1 reacted with malononitrile in the presence of ammonium
acetate to afford 2-amino-6 (Phenoxathiin-2-yl)-4-phenylnicotinonitrile
2 as a key precursor for the synthesis of condensed heterocyclic com-
pounds of expected biological activity (Scheme 1). The structure as-
signed for compound 2 was based on the microanalytical and spectro-
scopic data. The IR spectrum displays absorption bands of C N and
NH2. Also, the 1H NMR spectrum revealed a signal at 5.2 ppm for the
NH2 group.
Heating of 2 with formic acid under reflux afforded pyrido[2,3-
d]pyimidine 3 (Scheme 2). The IR spectrum displays a lack of an ab-
sorption of C N and NH2 and presence of CO and NH absorption.
On the other hand, treatment of 2 with phenyl isothiocaynate under
reflux in pyridine furnished the corresponding pyridopyrimidinethione
derivative 5. The reaction is assumed to take place via formation of
thiourea intermediate 4 followed by cyclization at the adjacent C N
group.24
This investigation was extended to use 2 as a reactive intermedi-
ate for the synthesis of a wide range of biologically active heterocycles.
Thus, fusion of compound 2 with urea or thiourea results in the forma-
tion of 6a and 6b, respectively (Scheme 2).
Furthermore, treatment of 2 with carbon disulfide afforded a
reaction product that could be formulated as 7-(phenoxathiin-2-yl)-
5-phenyl-1H-pyrido[2,3-d]pyrimidine-2,4-dithione 7. The aminopyri-
dopyrimidine derivative 8 was synthesized by reaction of the nicotinon-
itrile 2 with formamide. Moreover, 2 reacted with triethyl orthoformate
in acetic anhydride and resulted in the formation of formimidate 9.
Cyclization of the latter with methyl amine afforded pyrido[2,
3-d]pyrimidine 10 (Scheme 3). Hydrazinolysis of 9 with hydrazine
hydrate or phenylhydrazine furnished 11a and 11b, respectively.
C6H5
S
COCH=CHC6H5
CN
CH2(CN)2
CH3CO2NH4
Ar
NH2
O
N
1
2
S
Ar =
O
SCHEME 1

208
M. S. Behalo
C6H5
O
HCOOH
NH
Ar
Ar
N
N
N
3
NH
C6H5
C6H5
C6H5NCS
C6H5
..
HN
C6H5
N
2
Ar
S
N
N
H
S
N
N
H
5
4
NH2
C6H5
N
NH2CXNH2
Ar
X
N
N
H
S
6a-b
6a: X = O, 6b: X = S
Ar =
SCHEME 2
O
The synthesized derivative 11a seemed to be an excellent target
for the synthesis of other desired heterocyclic derivatives through its
participation in a number of chemical reactions with various reagents.
Thus, pyrido[2,3-d]pyrimidine 11a was employed in the synthesis of
a triazole moiety fused to a pyrimidine ring as shown in Scheme 4.
Treatment of 11a with phenyl isothiocyanate afforded compound 12.
The structure of 12 was confirmed by the disappearance of the NH2
signal in the 1H NMR spectrum, which appeared at 6.3 ppm in 11a. Re-
action of 11a with diethyl oxalate gave 7-(phenoxathiin-2-yl)-9-phenyl-
1,3.3a,5,6-pentaazacyclopenta[a]-2-naphthoate (13). Its structure was
elucidated by the presence of a C O ester absorption band and the
1H NMR spectrum (cf. Experimental). Hydrolysis of the ester 13 with
sodium hydroxide furnished the corresponding acid 14.
The pyrido[2,3-d]pyrimidine 11a reacted with carbon disulfide to
afford the triazolethione derivative 15. Refluxing of 11a with ethyl
cyanoacetate in ethanol resulted in the formation of the nitrile 16.
Both elemental and spectroscopic data of 16 are consistent with the
assigned structure (cf. Experimental). Furthermore, refluxing of 11a

Pyrido[2,3-d]pyrimidines
209
NH2
C6H5
S
C6H5
CS2
HCONH2
N
NH
2
Ar
Ar
N
N
S
N
N
H
CH(OC2H5)3
7
8
NH
N
C6H5
C6H5
NH
N
C6H5
CH3
NHR
CN
RNHNH2
CH3NH2
Ar
N
N
CHOC H
Ar
N
2
5
Ar
N
N
N
10
9
11a-b
11a: R =H 11b: R = C6H5
SCHEME 3
CO2Et
NHC6H5
N
N
C6H5
C6H5
N
N
N
N
(CO2Et)2
C6H5NCS
11a
Ar
Ar
N
N
N
N
13
CS2
12
-
OH
S
CO2H
N
N
N
C6H5
C6H5
NH
N
N
Ar
Ar
N
N
N
N
15
14
SCHEME 4
with formic and acetic acid gave the corresponding triazoles 17a and
17b, respectively (Scheme 5).
On the other hand, the pyrido[2,3-d]pyrimidine 11a was employed
in the synthesis of a triazine moiety fused to a pyrimidine ring with
the aim of enhancement of the biological activity. Thus, the reaction of
equimolar amounts of 11a and chloroacetyl chloride gave the triazine
18, which in turn reacted with benzaldehyde in the presence of sodium

210
M. S. Behalo
R
N
CH2CN
N
N
N
C6H5
C6H5
N
NCCH2CO2Et
N
RCOOH
11a
Ar
Ar
N
N
N
N
17a-b
ClCOCH2Cl
16
17a: R = H,
17b: R = CH3
CHC6H5
O
O
O
O
N
N
N
C6H5
C6H5
C6H5
NH
NH
N
NH
N
C6H5CHO
Ar
N
Ar
Ar
N
N
N
N
N
N
20
18
19
SCHEME 5
acetate to give product 19. Finally, 11a reacted with oxalyl chloride to
give the triazinedione derivative 20 (Scheme 5).
Biological Activity
Some of the synthesized compounds were tested for their antimicrobial
activity. Chloramphenicol as an antibacterial agent and Terbinafan as
an antifungal agent were used as references to evaluate the potency
of the tested compounds under the same conditions. The tests were
carried out using the filter paper and hole plate method.25 Tested mi-
croorganisms were Gram positive (Bacillus subtilis and Rhadococcus
equii) and Gram negative bacteria (Salmonella typhimurium and
Escherichia coli). In addition, the antifungal activity against Fusar-
ium moniliforme and Fusarium solami was tested.
The sensitivity of the selected microorganisms to some synthe-
sized compounds was determined at different concentrations (125, 250,
500 µg/ml in 10% acetone) using the inhibition zone diameter as the
criterion for antimicrobial activity. The results (Table I) revealed that
compounds 3 and 13 possess the highest activity against Escherichia
coli among all the considered compounds, whereas compounds 6b and 7
showed the highest degree of inhibition of Bacillus subtilis. Compound
12 exhibited the maximum inhibition against Fusarium moniliforme
and Fusarium solami.

Pyrido[2,3-d]pyrimidines
211
TABLE I Responses of Various Micro-Organisms to Some
Synthesized Compounds[a]
B.
R.
S.
E.
F.
F.
Compound
subtilis
equii
typhimurium
coli
moniliforme solami
3
5
6a
6b
7
12
13
15
+
++
−
−
−
−
+
++
+
+
+
−
+
+
−
−
+
++
−
+ + +
+ + +
−
+
−
+
−
+
−
+
−
+
+
−
−
+ + +
−
+ + +
+
+
−
+
+ + +
+
++
+
+
−
+
+
20
−
+
−
−
+
Chloramphenicol
Terbinafan
+ + +
+ + +
+ + +
+ + +
+ + +
+ + +
aInhibition zone diameter d of either fungal growth or bacterial cells for each
compound: + + + > 12 mm, highly active; ++ > 9 mm, moderately active; + > 7 mm,
slightly active; − no inhibition observed.
It was observed that the activity of these compounds is similar to
that of the standard drugs (Chloramphenicol and Terbinafan). All other
compounds either do not exhibit any activity or are less active against
the tested species.
EXPERIMENTAL
Melting points of the prepared products are uncorrected. All reactions
were monitored by thin layer chromatography (TLC) carried out on
0.2 mm silica gel 60 F254 (Merck) plates. IR spectra in KBr were
recorded using a Perkin-Elmer 298 spectrophotometer. 1H and 13C
NMR spectra were obtained using a Varian Gemini 200 MHz and 50
MHz instrument. The solvent used for NMR analysis was DMSO-d6,
unless stated otherwise. Mass spectra were obtained using a Shimadzu
GCMS-QP 1000 EX mass spectrometer.
1-(Phenoxathiin-2-yl)-3-phenyl-propenone (1)
A mixture of 2-acetylphenoxathiin (0.01 mol), benzaldehyde (0.01 mol)
and NaOH (1g in 10 mL water) in EtOH (30 mL) was stirred at rt. for
about 3 h. The solid was washed, dried, and crystallized from ethanol
to give chalcone 1. Yield, 80%; m.p. 196–198◦C. IR: 1690 (C O), 1610
(C C) cm−1. 1H NMR (CDCl3): δ 6.41 (d, 1H, α-CH olefinic), 7.46 (d, 1H,

212
M. S. Behalo
β-CH olefinic), 7.13–7.90 (m, 12H, ArH). MS: m/z 330 (M+). Anal. calcd.
for C21H14O2S (330.40): C, 76.34; H, 4.27. Found: C, 76.26; H, 4.13.
2-Amino-6-(phenoxathiin-2-yl)-4-phenylnicotinonitrile (2)
A mixture of equimolar amounts of chalcone 1 and malononitrile (0.01
mol) in EtOH (30 mL) containing ammonium acetate (0.02 mol) was
heated under reflux for 6 h. The reaction mixture was concentrated,
cooled, and filtered, and the residue was crystallized from EtOH to
give 2. Yield, 75%; m.p. 228–230◦C. IR: ν 2225 (C N), 3345, 3320 cm−1
1
(NH2). H NMR (DMSO-d6): δ 5.24 (s, 2H, NH2, exchangeable), 6.94–
7.88 (m, 13H, ArH). 13C NMR: δ 105.6 (C-3), 115 (CN), 117.2 (C-5), 152
(C-4), 160.8 (C-6), 164.2 (C-2), 116.7, 118.2, 120.2, 121.3, 122, 122.8,
124.8, 126,127.6, 129, 130.4, 132.2, 136.2, 157.3, 158.2 (C-phenyl and
phenoxathiin moieties). MS: m/z 393 (M+). Anal. calcd. for C24H15N3OS
(393.46): C, 73.26; H, 3.84; N, 10.68. Found: C, 73.12; H, 3.65; N, 10.76.
7-(Phenoxathiin-2-yl)-5-phenyl-3H-pyrido[2,3-d]pyrimidin-4-
one (3)
Nicotinonitrile 2 (0.01 mol) was heated with an excess of formic acid
under reflux for 4 h. After cooling, the precipitated solid was filtered,
dried, and crystallized from EtOH. Yield, 60%; m.p. 232–234◦C. IR: ν
OH) cm−1. 1H NMR (DMSO-d6):
←
→
1610 (C N), 1680 (C O), 3300 (NH
δ 6.83–8.21 (m, 14H, ArH + pyrimidine-H), 8.57 (s, 1H, NH, exchange-
able). MS: m/z 421 (M+). Anal. calcd. for C25H15N3O2S (421.47): C,
71.24; H, 3.59; N, 9.97. Found: C, 71.33; H, 3.71; N, 10.12.
4-Imino-7-(phenoxathiin-2-yl)-3,5-diphenyl-3,4-dihydro-1H-
pyrido[2,3-d]pyrimidine-2-thione (5)
A mixture of 2 (0.01 mol) and phenyl isothiocyanate (0.01 mol) in pyri-
dine (15 mL) was refluxed for 5 h. After cooling, the reaction mixture
was poured into cold aqu. HCl. The solid product was filtered, dried,
and crystallized. IR: ν 1305 (C S), 3260 (NH) cm−1. 1H NMR (DMSO-
d6): δ 6.97-8.15 (m, 18H, ArH), 8.61, 8.94 (s, 2H, 2NH, exchangeable).
MS: m/z 528 (M+). Anal. calcd. for C31H20N4OS2 (528.65): C, 70.43; H,
3.81; N, 10.60. Found: C, 70.33; H, 3.66; N, 10.56.
Synthesis of 6a–b: General Procedure
Equimolar amounts of 2 and urea or thiourea (0.01 mol) were fused in
an oil bath for 2 h. After cooling, the product was treated with water,
filtered, dried, and crystallized to give 6a–b respectively.

Pyrido[2,3-d]pyrimidines
213
4-Amino-7-(phenoxathiin-2-yl)-5-phenyl-1H-pyrido[2,3-
d]pyrimidine-2-one (6a)
Yield, 60% (EtOH); m.p. 260–262◦C. IR: ν 1685 (C O), 3450–3200
(NH2 and NH) cm−1. 1H NMR (DMSO-d6): δ 6.22 (s, 2H, NH2, exchange-
able), 7.09–8.12 (m, 13H, Ar H), 8.87 (s, 1H, NH, exchangeable). 13C
NMR: δ 114.2 (C-4a), 116.3 (C-6), 150.7(C-5), 156 (C-7), 158.2 (C-8a),
161 (CO), 165.1 (C-4), (C-phenyl and phenoxathiin moieties as shown
for 2). Anal. calcd. for C25H16N4O2S (436.49): C, 68.79; H, 3.69; N, 12.84.
Found: C, 68.95; H, 3.78; N, 12.90.
4-Amino-7-(phenoxathiin-2-yl)-5-phenyl-1H-pyrido[2,3-
d]pyrimidine-2-thione (6b)
Yield, 62% (EtOHl); m.p. 266–268◦C. IR: ν 1260 (C S), 1610 (C N),
3370–3190 (NH2 and NH) cm−1. MS: m/z 452 (M+). Anal. calcd. for
C25H16N4OS2 (452.55): C, 66.35; H, 3.56; N, 12.38. Found: C, 66.41; H,
3.64; N, 12.42.
7-(Phenoxathiin-2-yl)-5-phenyl-1H-pyrido[2,3-d]pyrimidine-
2,4-dithione (7)
CS2 (0.015 mol) was added to a solution of 2 (0.01 mol) in DMF (20 mL).
Then MeONa [prepared from Na (0.5 g) and MeOH (10 mL)] was added.
The mixture was heated under reflux for 10 h, cooled, and poured into
cold water followed by addition of NaOH (10 mL) and left overnight.
The clear solution obtained by filtration was acidified with AcOH to give
a solid product, which was collected by filtration, dried, and crystallized
from benzene to give 7. Yield, 58%; m.p. 222–224◦C. IR: ν 3340–3260
1
(NH), 1290–1270 (2 C S) cm−1. H NMR (DMSO-d6): δ 6.89–8.13 (m,
13H, ArH), 8.66, 9.11 (2s, 2H, 2NH, exchangeable). 13C NMR: δ 116
(C-4a), 112.4 (C-6), 153.2 (C-5), 158.4 (C-7), 162 (C-8a), 180.3, 198.6 (2
CS), (C-phenyl and phenoxathiin moieties as shown for 2). Anal. calcd.
for C25H15N3OS3 (469.60): C, 63.94; H, 3.22; N, 8.95. Found: C, 64.19;
H, 3.41; N, 8.70.
4-Amino-7-(phenoxathiin-2-yl)-5-phenylpyrido[2,3-
d]pyrimidine (8)
Compound 2 (0.01 mol) in formamide (15 mL) was heated under reflux
for 8 h and left to be cooled. The solid product was filtered and crys-
tallized from EtOH to give 8. Yield, 70%; m.p. 280–282◦C. IR: ν 3390,
3340 (NH2), 1620 (C N) cm−1. 1H NMR (DMSO-d6): δ 6.41 (s, 2H, NH2,
exchangeable), 7.03-8.11 (m, 14H, ArH + pyrimidine H). 13C NMR: δ

214
M. S. Behalo
109.6 (C-4a), 118.2 (C-6), 150(C-5), 158.5 (C-7), 157 (C-2), 159 (C-8a),
167 (C-4), (C-phenyl and phenoxathiin moieties as shown for 2). MS:
m/z 420 (M+). Anal. calcd. for C25H16N4OS (420.49): C, 71.41; H, 3.84;
N, 13.32. Found: C, 71.31; H, 3.52; N, 13.11.
Ethyl N-[3-Cyano-6-(phenoxathiin-2-yl)-4-phenylpyridin-
2-yl]formimidiate (9)
A mixture of 2 (0.01 mol) and triethyl orthoformate (0.01 mol) in Ac2O
(5 mL) was refluxed for 6 h, then cooled and poured into cold water. The
precipitated solid was filtered, washed, dried, and crystallized from
EtOH to give 9. Yield, 80%; m.p. 195–197◦C. IR: ν 2215 (C N), 1620
(C N) cm−1. 1H NMR (DMSO-d6): δ 1.22–1.43 (t, 3H, OCH2CH3), 4.21-
4.33 (q, 2H, OCH2CH3), 7.11-8.15 (m, 13H, ArH), 8.37 (s, 1H, CH N).
13C NMR: δ 17 (CH3), 61(CH2),102.2 (C-3), 117.3 (CN), 118 (C-5), 151.4
(C-4), 159 (N CH), 161.2 (C-6), 168.3 (C-2), (C-phenyl and phenoxathiin
moieties as shown for 2). Anal. calcd. for C27H19N3O2S (449.52): C,
72.14; H, 4.26; N, 9.35. Found: C, 71.91; H, 4.11; N, 9.41.
4-Imino-3-methyl-7-(phenoxathiin-2-yl)-5-phenyl-3H-
pyrido[2,3-d]pyrimidine (10)
A mixture of 9 (0.01 mol) and methyl amine (0.01 mol) in EtOH (30 mL)
was heated under reflux for 8 h. After cooling, the reaction mixture
was poured into water and neutralized with dil. HCl. The collected
solid was crystallized from n-butanol. Yield, 65%; m.p. 210–212◦C. IR:
1
ν 3240–3200 (NH), 1615 (CN) cm−1. H NMR (CDCl3): δ 2.82 (s, 3H,
CH3), 7.03–7.84 (m, 14H, ArH + pyrimidine H) and 9.16 (s, 1H, NH,
exchangeable). Anal. calcd. for C26H18N4OS (434.51): C, 71.87; H, 4.18;
N, 12.89. Found: C, 71.99; H, 4.12; N, 12.73.
Synthesis of 11a–b: General Procedure
A mixture of 9 (0.01 mol) and hydrazine hydrate (0.01 mol) or phenyl-
hydrazine (0.01 mol) in EtOH (30 mL) was heated under reflux for
6 h. The reaction mixture was allowed to cool, poured into cold water,
and neutralized with AcOH. The solid product was filtered, washed
with water, dried, and crystallized from proper solvent to give 11a–b
respectively.

Pyrido[2,3-d]pyrimidines
215
3-Amino-4-imino-7-(phenoxathiin-2-yl)-5-phenyl-4H-
pyrido[2,3-d]pyrimidine (11a)
Yield, 78% (EtOH); m.p. 216–218◦C. IR: ν 3420–3350 (NH2),
3190 (NH), 1620 (C N) cm−1 1H NMR (DMSO-d6): δ 6.15 (s, 2H,
.
NH2exchangeable), 6.89–7.90 (m, 14H, ArH + pyrimidine H), 8.93 (s,
1H, NH exchangeable); 13C NMR, δ = 112.8 (C-4a), 116.2 (C-6), 151
(C-5), 160 (C-7), 162 (C-2), 163 (C-4), 165 (C-8a), (C-phenyl and phe-
noxathiin moieties as shown for 2). MS: m/z 435 (M+). Anal. calcd. for
C25H17N5OS (435.50): C, 68.95; H, 3.93; N, 16.08. Found: C, 68.71; H,
3.88; N, 15.81.
4-Imino-7-(phenoxathiin-2-yl)-5-phenyl-3-phenylamino-4H-
pyrido[2,3-d]pyrimidine (11b)
Yield, 67% (EtOH); m.p. 196–198◦C. IR: ν 3250–3200 (NH), 1600
(C N) cm−1. MS: m/z 511 (M+). Anal. calcd. for C31H21N5OS (511.60):
C, 72.78; H, 4.14; N, 13.69. Found: C, 72.92; H, 4.32; N, 13.37.
7-(Phenoxathiin-2-yl)-9-phenyl-2-phenylamino-1,3.3a,5,6-
pentaazacyclopenta[a]naphthalene (12)
A mixture of 11a (0.01 mol) and phenyl isothiocyanate (0.01 mol) in
EtOH (30 mL) was refluxed for 8 h. The reaction mixture was cooled
and filtered, and the resulting solid was crystallized from EtOH to give
12. Yield, 62%; m.p. 225–226◦C. IR: ν 3260 (NH), 1620 C N) cm−1. 1H
NMR (CDCl3): δ 6.94–8.33 (m, 14H, ArH + pyrimidine H), 10.17 (s, 1H,
NH, exchangeable). Anal. calcd. for C32H20N6OS (536.61): C, 71.62; H,
3.76; N, 15.66. Found: C, 71.86; H, 3.88; N, 15.91.
Ethyl 7-(Phenoxathiin-2-yl)-9-phenyl-1,3,3a,5,6-
pentaazacyclopenta[a]-2-naphthoate (13)
Equimolar amounts of 11a and diethyl oxalate (0.01 mol) in EtOH
(30 mL) were heated under reflux for 6 h. After cooling, the pre-
cipitated solid was filtered and crystallized from EtOH to give 13.
1
Yield, 72%; m.p. 231–233◦C. IR: ν 1730 (CO), 1615 (C N) cm−1. H
NMR (DMSO-d6): δ 1.23–1.31 (t, 3H, OCH2CH3), 4.21–4.29 (q, 2H,
OCH2CH3), 7.19–8.41 (m, 14H, ArH + pyrimidine H). Anal. calcd. for
C29H19N5O3S (517.56): C, 67.30; H, 3.70; N, 13.53. Found: C, 67.41; H,
3.77; N, 13.50.

216
M. S. Behalo
7-(Phenoxathiin-2-yl)-9-phenyl-1,3,3a,5,6-
pentaazacyclopenta[a]naphthalene-2-carboxylic Acid (14)
A mixture of 13 (0.01 mol) and NaOH (10%. 15 mL) was heated un-
der reflux for 6 h. The reaction mixture was cooled and poured into
cold water, then neutralized with HCl. The precipitated solid was col-
lected by filtration, dried, and crystallized from EtOH. Yield, 65%; m.p.
240–242◦C. IR: ν 3450 (OH), 1710 (C O) cm−1. 1H NMR (DMSO-d6): δ
6.84-8.35 (m, 14H, ArH + pyrimidine H), 10.22 (s, 1H, OH, exchange-
able). Anal. calcd. for C27H15N5O3S (489.51): C, 66.25; H, 3.09; N, 14.31.
Found: C, 66.34; H, 3.17; N, 14.43.
7-(Phenoxathiin-2-yl)-9-phenyl-1,3,3a,5,6-
pentaazacyclopenta[a]naphthalene-2-thione (15)
A mixture of 11a (0.01 mol) and CS2 (3 mL) in EtOH (30 mL) was
heated under reflux for 6 h. Once cooled, the precipitated solid was
filtered and crystallized from EtOH to give 15. Yield, 63%; m.p. 212–
214◦C. IR: ν 3300–3280 (NH), 1280 (C S), 1600 (C N) cm−1. 1H NMR
(CDCl3): δ 7.01–8.13 (m, 14H, ArH + pyrimidine H), 8.70 (s, 1H, NH, ex-
changeable). MS: m/z 477 (M+). Anal. calcd. for C26H15N5OS2 (477.56):
C, 65.39; H, 3.17; N, 14.66. Found: C, 65.46; H, 3.26; N, 14.51.
[7-(Phenoxathiin-2-yl)-9-phenyl-1,3,3a,5,6-
pentaazacyclopenta[a]naphthalene-2-yl]acetonitrile (16)
A mixture of 11a (0.01 mol) and ethyl cyanoacetate (0.01 mol) in EtOH
(30 mL) was heated under reflux for 6 h. Once cooled, the obtained solid
product was filtered and crystallized from EtOH to give 16. Yield, 67%;
m.p. 223-225 ◦C. IR: ν 2220 (C N), 1610 (C N) cm−1. 1H NMR (CDCl3):
δ 3.93 (s, 2H, CH2), 7.07-8.31 (m, 14H, ArH + pyrimidine H). 13C NMR:
δ 20.3 (CH2), 114.8 (CN), 119 (C-8), 121.8 (C-9a), 147.2(C-9b), 149.3
(C-9), 155.6 (C-5a), 156 (C-7), 157.2 (C-4), 161.1 (C-2), (C-phenyl and
phenoxathiin moieties as shown for 2). Anal. calcd. for C28H16N6OS
(484.53): C, 69.41; H, 3.33; N, 17.34. Found: C, 69.37; H, 3.27; N, 17.25.
Synthesis of 17a–b: General Method
A mixture of 11a (0.01 mol) and formic acid or AcOH (10 mL) was
heated under reflux for 8 h. The reaction mixture was cooled and poured
into cold water. The precipitated solid was filtered, washed, dried, and
crystallized from a proper solvent to give 17a–b respectively.

Pyrido[2,3-d]pyrimidines
217
7-(Phenoxathiin-2-yl)-9-phenyl-1,3,3a,5,6-
pentaazacyclopenta[a]naphthalene (17a)
Yield, 65% (EtOH); m.p. 218–220◦C. IR: ν 1615 (C N) cm−1. MS: m/z
445 (M+). Anal. calcd. for C26H15N5OS (445.50): C, 70.10; H, 3.39; N,
15.72. Found: C, 70.19; H, 3.49; N, 15.77.
2-Methyl-7-(phenoxathiin-2-yl)-9-phenyl-1,3,3a,5,6-
pentaazacyclopenta[a]naphthalene (17b)
Yield, 64% (EtOH); m.p. 229–230◦C. IR: ν 1615 (C N) cm−1. 1H NMR
(CDCl3): δ 2.31 (s, 3H, CH3), 6.82-7.84(m, 14H, ArH + pyrimidine H).
Anal. calcd. for C27H17N5OS (459.52): C, 70.57; H, 3.73; N, 15.24. Found:
C, 70.42; H, 3.81; N, 15.13.
7-(Phenoxathiin-2-yl)-5-phenyl-3H-1,4,8,9,10a-
pentaazaphenanthren-2-one (18)
Compound 11a (0.01 mol) and chloroacetyl chloride (0.01 mol) were dis-
solved in dioxane (30 mL) and left at room temperature overnight. The
precipitated solid was collected by filtration and crystallized from EtOH
◦
←
to give 18. Yield, 73%; m.p. 253–255 C. IR: ν 3320–3260 (NH OH),
→
1685 (C O) cm−1. H NMR (CDCl3): δ 4.33 (s, 2H, CH2), 8.37 (s, 1H,
1
NH, exchangeable), 7.08–7.92 (m, 14H, ArH + pyrimidine H). MS: m/z
475 (M+). Anal. calcd. for C27H17N5O2S (475.52): C, 68.20; H, 3.60; N,
14.73. Found: C, 67.95; H, 3.81; N, 14.58.
3-Benzylidene-7-(phenoxathiin-2-yl)-5-phenyl-3H-1,4,8,9,
10a-pentaazaphenanthrene-2-one (19)
Benzaldehyde (0.01 mol) and NaOAc (0.5 g) were added to a solution
of 18 (0.01 mol) in AcOH (30 mL). The reaction mixture was heated
under reflux for 6 h and cooled. The solid product was filtered and
◦
crystallized from EtOH to give 19. Yield, 65%; m.p. 240-242 C. IR:
ν 3350-3240 (NH OH), 1680 (C O) cm−1. MS: m/z 563 (M+). Anal.
←
→
calcd. for C34H21N5O2S (563.63): C, 72.45; H, 3.76; N, 12.43. Found: C,
72.58; H, 3.81; N, 12.54.
7-(Phenoxathiin-2-yl)-5-phenyl-1,4,8,9,10a-
pentaazaphenanthrene-2,3-dione (20)
A mixture of 11a (0.01 mol) and oxalyl chloride (0.01 mol) in dry benzene
(30 mL) was heated under reflux for 10 h. The reaction mixture was
cooled, filtered and crystallized from dioxane to give 20. Yield, 70%; m.p.

218
M. S. Behalo
◦
216–218 C. IR: ν 3360–3230 (NH OH), 1710–1680 (2 C O) cm−1. 1H
←
→
NMR (CDCl3): δ 6.91-8.12 (m, 14H, ArH + pyrimidine H), 9.58 (s, 1H,
NH, exchangeable). Anal. calcd. for C27H15N5O3S (489.51): C, 66.25; H,
3.09; N, 14.31. Found: C, 65.88; H, 3.22; N, 14.30.
REFERENCES
[1] L. Cordeu, E. Cubedo, E. Bandres, A. Rebollo, X. Saenz, H. Chozas, M. V. Dominguez,
M. Echeveria, B. Mendivil, C. Sanmartin, J. A. Palop, M. Font, and J. G. Foncillas,
Bioorg. Med. Chem., 15, 1659 (2007).
[2] C. M. Viturro and D. Dominguez, Tetrahedron Lett., 48, 4707 (2007).
[3] N. R. Mohamed, M. M. T. El-Saidi, Y. M. Ali, and M. H. Elnagdi, Bioorg. Med. Chem.,
15, 6227 (2007).
[4] C. Sanmartin, M. Echeveria, B. Mendivil, L. Cordeu, E. Cubedo, J. G. Foncillas,
M. Font, and J. A. Palop, Bioorg. Med. Chem., 13, 2031 (2005).
[5] M. Zink, H. Lanig, and R. Troschutz, Eur. J. Med. Chem., 39, 1079 (2004).
[6] S. R. Kanth, G. V. Reddy, K. H. Kishore, P. S. Rao, B. Narsaiah, and U. S. N. Murthy,
Eur. J. Med. Chem., 41, 1011 (2006).
[7] U. Girreser, D. Heber, and M. Schutt, Tetrahedron, 60, 11511 (2004).
[8] J. Quiroga, H. Insuasty, B. Insuasty, R. Abonia, A. S. Cobo, and M. Nogueras,
Tetrahedron, 58, 4873 (2002).
[9] J. I. DeGraw, P. H. Christie, W. T. Clowell, and F. M. Sirotank, J. Med. Chem., 35,
320 (1992).
[10] H. Sladoska, A. Sabiniarz, B. Filipek, M. Kardasz, and D. Maciag, Farmaco, 58, 25
(2003).
[11] M. Cowart, C. Lee, G. A. Gfesser, E. K. Bayburt, S. S. Bhagwat, A. O. Stewart, K. L.
Kohlhaas, C. T. Wismer, J. Mikusa, C. Zhu, K. M. Alexander, M. F. Jarvis, and E. A.
Kowaluuk, Bioorg. Med. Chem. Lett., 11, 83 (2001).
[12] G. Singh, A. K. Yadav, and K. Mishraa, Indian J. Chem., 41, 430 (2002).
[13] C. Z. Zheng, Y. Mao, C. Lee, J. K. Pratt, J. R. Koenig, R. J. Perner, M. Cowart, G. A.
Gfesser, S. Mcgaraughty, K. L. Chu, C. Zhu, H. Yu, K. L. Kohlhaas, K. M. Alexander,
C. T. Wismer, J. Mikusa, M. F. Jarvis, E. A. Kowaluuk, and A. O. Stewart, Bioorg.
Med. Chem. Lett., 13, 3041 (2003).
[14] M. A. Matulenko, C. Lee, M. Jiang, R. R. Frey, M. Cowart, E. K. Bayburt,
S. Domenico, G. A. Gfesser, A. Gomtsyan, G. Z. Zheng, J. A. Mckie, A. O. Stewart,
K. L. Kohlhaas, K. M. Alexander, R. D. Snyder, E. A. Kowaluuk, and S. S. Bhagwat,
Bioorg. Med. Chem., 13, 3705 (2005).
[15] J. Bulicz, D. C. G. Bertarelli, D. Baumert, F. Fulle, C. E. Muller, and D. Heber,
Bioorg. Med. Chem., 14, 2837 (2006).
[16] R. Perner, C. Lee, M. Jiang, S. Domenico, E. K. Bayburt, K. M. Alexander, K. L.
Kohlhaas, M. F. Jarvis, E. A. Kowaluuk, and S. S. Bhagwat, Bioorg. Med. Chem.
Lett., 15, 2803 (2005).
[17] B. D. Palmer, J. B. Smaill, G. W. Rewcastle, E. M. Dobrusin, A. Kraker, C. W. Moore,
R. W. Steinkampf, and W. A. Denny, Bioorg. Med. Chem. Lett., 15, 1931 (2005).
[18] T. L. James, K. E. Lind, Z. Du, M. B. Peterlin, K. Fujinaga, R. K. Guy, P. Madrid, and
M. Mayer, PCT Int. Appl. WO 03 62, 388 (2003); Chemical Abstracts, 139, 143903
(2003).

Pyrido[2,3-d]pyrimidines
219
[19] Y. Girard, P. Hamel, and D. Delorme, US Pat. 5036067 (1990); Chemical Abstracts,
115, 232258 (1991).
[20] J. J. Tegeler, H. H. Ong, and J. A. Profitt, J. Heterocycl. Chem., 20, 867 (1983).
[21] G. W. Rewcastle, G. J. Atwell, B. D. Palmer, P. D. Boyd, B.C. Baguley, and W. A.
Denny, J. Med. Chem., 34, 491 (1991).
[22] C. T. Supuran, A. Scozzafava, F. Briganti, G. Loloiu, and O. Maior, J. Enzyme Inhib.,
31, 291 (1998); Chemical Abstracts, 130, 49076 (1999).
[23] Y. A. Issac, E. G. El-Karim, S. G. Donia, and M. S. Behalo, Sulfur Lett., 25, 183
(2002).
[24] M. S. El-Gaby, S. M. Abedel-Gawad, M. M. Ghorab, H. I. Heiba, and H. M. Aly,
Phosphorous, Sulfur, and Silicon, 181, 279 (2006).
[25] C. Leifer, S. Chidbouree, S. Hampson, S. Workman, D. Sigee, H. A. S. Epton, and
A. Harbour, J Appl. Bact., 78, 97 (1995).