Synthesis and antimicrobial activity of some new 2-(3-chloro-1- benzothiophen-2-yl)-3-(substituted-phenyl)-4- (3H)-quinazolinones derivatives

Article abstract of DOI:10.1080/17415993.2011.575943

3-Chloro-1-benzothiophene-2-carbonylchloride 1 reacted with anthranilic acid in pyridine to give compound 2. The main aim of the work is to study the behavior of this 4H-3,1-benzoxazin-4-one toward nitrogen nucleophiles. The compound reacted with aromatic amines, hydroxylamine hydrochloride, formamide, thioglycolic acid, thiosemicarbazide and acid chlorides to give various 3-substituted quinazolinones, respectively. The structures of all the synthesized compounds were confirmed by spectral data and have been screened for antibacterial and antifungal activity.

Full text of DOI:10.1080/17415993.2011.575943

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Synthesis and antimicrobial
activity of some new 2-(3-chloro-1-
benzothiophen-2-yl)-3-(substituted-
phenyl)-4- (3H)-quinazolinones
derivatives
Gadada Naganagowda a & Amorn Petsom a
a Research Center for Bioorganic Chemistry, Department of
Chemistry, Faculty of Science , Chulalongkorn University , 254
Phayathai Road, Bangkok , 10330 , Thailand
Published online: 26 Apr 2011.
To cite this article: Gadada Naganagowda & Amorn Petsom (2011) Synthesis and
antimicrobial activity of some new 2-(3-chloro-1-benzothiophen-2-yl)-3-(substituted-
phenyl)-4- (3H)-quinazolinones derivatives, Journal of Sulfur Chemistry, 32:3, 223-233, DOI:
10.1080/17415993.2011.575943
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Journal of Sulfur Chemistry
Vol. 32, No. 3, June 2011, 223–233
Synthesis and antimicrobial activity of some new
2-(3-chloro-1-benzothiophen-2-yl)-3-(substituted-phenyl)-4-
(3H)-quinazolinones derivatives
Gadada Naganagowda and Amorn Petsom*
Research Center for Bioorganic Chemistry, Department of Chemistry, Faculty of Science, Chulalongkorn
University, 254 Phayathai Road, Bangkok 10330, Thailand
(Received 20 January 2011; final version received 24 March 2011)
3-Chloro-1-benzothiophene-2-carbonylchloride 1 reacted with anthranilic acid in pyridine to give com-
pound 2.Themainaim oftheworkistostudythebehaviorofthis4H-3,1-benzoxazin-4-onetowardnitrogen
nucleophiles. The compound reacted with aromatic amines, hydroxylamine hydrochloride, formamide,
thioglycolic acid, thiosemicarbazide and acid chlorides to give various 3-substituted quinazolinones,
respectively. The structures of all the synthesized compounds were confirmed by spectral data and have
been screened for antibacterial and antifungal activity.
NH2
R2
R3
R2
R3
N
R1
O
N
O
N
O
R1
S
S
CH3COOH
Reflux, 4h
2
3a–g
Cl
Cl
Keywords: benzothiophene; quinazolinones; antibacterial activity; antifungal activity
1. Introduction
Research programs for the discovery of new antimicrobial drugs for improving their efficacy are
under way in many laboratories. Reports of efficacy of heterocycles for their biological and phar-
macological activities are as old as recorded history (1).A number of heterocyclic moieties such as
thiophene, furan, pyridine, quinoline, etc., form an important pharmacophores in several clinically
used drugs and natural products, possessing biological properties (2). In particular, the literature
is well documented with the biological and pharmacological efficacy of quinazolinones and ben-
zothiophene derivatives (3). In view of these facts, the work of synthesis of heterocyclic analogs
*Corresponding author. Email: amorn.p@chula.ac.th
ISSN 1741-5993 print/ISSN 1741-6000 online
© 2011 Taylor & Francis
DOI: 10.1080/17415993.2011.575943
http://www.informaworld.com

224 G. Naganagowda and A. Petsom
of quinazolinones and the benzothiophene molecules and the investigation of their biological
activity was undertaken.
The quinazolinone nucleus has been found to possess varied pharmacological activities, viz.
anticonvulsant (4), bronchodilator (5, 6), anti-inflammatory (7–9), antimalarial (10), antituber-
culous (11), anti-HIV (12), narcotic antagonist (13), antitumor (14), tyrosine kinase inhibitor
(15), adenosine antagonist (16) and antimicrobial (17). Similarly, various substituted aromatic
amines are known to possess varied pharmacological activities such as anthelmintic and analgesic
activity (18–20). Prompted by the biological interest, and as a continuation of our search for
bioactive molecules, we report herein the synthesis of benzothiophene-containing quinazolin-
4-one derivatives via the formation of a benzoxazin-4-one key precursor. The investigation of
their possible antibacterial and antifungal activities and the relationship of molecular structure
and the resulting bioactivity are also discussed.
2. Results and discussion
The synthesis of the benzothiophene-containing quinazolin-4-one target compounds started with
the synthesis of 3-chloro-1-benzothiophene-2-carbonylchloride 1, which was prepared by the
reaction of cinnamic acid with thionyl chloride in dimethyl formamide (DMF) and dry pyri-
dine according to the reported method (21). It was then allowed to react with anthranilic acid in
dry pyridine to give 2-(3-chloro-1-benzothiophen-2-yl)-4H-3,1-benzoxazin-4-one 2 (Scheme 1).
Compound 2 showed peaks in its IR spectrum at 1710 and 1620 cm−1 corresponding to C=O and
C=N groups, respectively. The 1H-nuclear magnetic resonance (NMR) spectrum of compound 2
exhibited a multiplet between δ 8.12 and 7.40 ppm due to eight aromatic protons. Furthermore,
the structure of 2 was confirmed by the presence of a molecular ion peak in its mass spectrum
(MS) at m/z 313.75 corresponding to its molecular weight. Several amines (i.e. aromatic amines,
hydroxylamine hydrochloride and formamide) were selected in order to study the reactivity of
the benzoxazin-4-one moiety of compound 2 toward nitrogen nucleophiles. Upon reaction with
aromatic amines in refluxing glacial acetic acid, N-substituted quinazolinone derivatives 3a–g
were obtained. These compounds showed a multiplet between δ 8.12 and 7.10 ppm due to 11
aromatic protons in 1H-NMR spectra. Compound 2 was reacted with hydroxylamine hydrochlo-
ride, affording 2-(3-chloro-1-benzothiophen-2-yl)-3-hydroxyquinazolin-4(3H)-one (4). The IR
spectrum of compound 4 showed peaks near 3473 and 1711 cm−1 due to OH and C=O stretching
absorption frequencies. Acylation of compound 4 using acetic anhydride to give compound 5
1
which exhibited a singlet at δ 2.30 ppm in its H-NMR spectrum due to three protons of the
–CH3 group and a molecular ion peak at m/z 371.12 which is consistent with its assigned
structure. As the third example, compound 2 was also allowed to react with formamide,
resulting in compound 6 which showed a characteristic singlet at 11.29 ppm due to the N–H
proton.
As shown in Scheme 2, compound 2 was treated with hydrazine hydrate in a manner similar
to get 3-amino-2-(3-chloro-1-benzothiophen-2-yl)quinazolin-4(3H)-one 7. Based on Fourier-
transformed infrared (FTIR) analysis, compound 7 showed the peaks near 3130 cm−1 due to
NH stretching absorption frequencies. Compound 7 was allowed to react with chloroacetyl chlo-
ride in dry pyridine to get compound 8 which exhibited distinctive peaks at 3250 and 1713 cm−1
1
due to N–H and C=O stretching absorption frequencies in its IR spectrum. H-NMR spectrum
of compound 8 showed two singlet signals, one at δ4.16 ppm and the other at δ10.64 ppm due
to –CH2 and –CONH protons, respectively. Upon the reaction with acetyl chloride or benzoyl
chloride in dry acetone, compound 7 was converted to compound 9a and 9b, respectively. The
1H-NMR spectrum of compound 9a showed a singlet signal at δ2.01 ppm due to three pro-
tons of the –CH3 groups, while the formation of compound 9a was confirmed by its MS which

Journal of Sulfur Chemistry 225
Cl
Cl
O
S
1
O
OH
Pyridine
H2N
Reflux, 3h
O
N
O
S
NH2
R3
R2
2
Cl
CH3COOH
Reflux, 4h
HCONH2
Reflux, 4h
R1
CH3COOH
Reflux, 4h
NH2OH· HCl
R2
O
O
R3
R1
O
OH
NH
N
N
S
S
N
N
S
6
N
4
Cl
Cl
3a–g
Cl
Ac2O
Reflux, 2h
O
Compound
R1
R2
R3
3a
3b
3c
F
F
NO2
CH3
OCH3
Cl
Cl
H
H
H
H
-H
O
N
O
N
3d
3e
3f
H
H
H
H
H
S
H
5
H
Cl
3g
H
NO2
Scheme 1. General synthetic procedure for benzothiophene containing benzoxazin-4-one 2,
quinazolinone derivatives 3a–g and 4–6.
exhibited a molecular ion peak at m/z 369.82 corresponding to its molecular weight. Compound
2 undergoes hetero-ring opening when reacted with 2-mercaptoacetic acid or thiosemicarbazide,
leading to compound 10 or 11, respectively. Compound 2 was also allowed to react with o-
phenylenediamine. Interestingly, whenthereactionwasperformedinrefluxingethanol, compound
12 was obtained, but the reaction in refluxing acetic acid in the presence of sodium acetate,
gives compound 13. The structure of compounds 12 and 13 were also confirmed by IR, mass
1
spectral analysis, H and 13C-NMR and by combustion analysis as shown in the experimental
section.

226 G. Naganagowda and A. Petsom
O
N
O
Cl
O
N
R
S
O
N
O
Cl
NH
NH
2
Cl
NH
N
R-COCl
N
O
Cl
S
CH COCH
N
Pyridine
Reflux, 2 h
3
3
8
7
S
Reflux, 2 h
9a and b
Cl
Cl
9a, R= –CH3
9b, R= –C6H5
CH COOH
3
NH NH ·2H O
2
2
2
Reflux, 10 h
O
NH–CSNH
2
O
N
NH
O
COOH
NH NHCSNH
2
2
SH–CH –COOH
2
O
S
NH
O
S
CH COOH
3
S
Benzene
Reflux, 13 h
NH
O
Reflux, 5 h
S
2
Cl
11
Cl
Cl
10
NH
2
NH
2
CH COONa
3
Reflux, 5 h
C H OH
2
5
CH COOH
3
Reflux, 4 h
H N
2
O
O
S
NH
H N
N
2
NH
O
N
Cl
S
O
Cl
13
12
Scheme 2. Synthesis of quinazolinone derivatives.
3. Antimicrobial activity
3.1. Antibacterial activity
A cup plate method using Hi-Media agar medium was employed to study the antibacterial activity
of the synthesized compounds against two Gram-positive bacteria, Staphylococcus aureus-ATCC
25923 and Bacillus subtilis-ATCC 6633 and Gram-negative bacteria, Pseudomonas aeruginosa-
ATCC 10145 and Escherichia coli-ATCC 35218. Preparation of nutrient broth, subculture, base
layer medium, agar medium and peptone water is done as per the standard procedure (22). Each
test compound (50 mg) was dissolved in DMF (50 ml, 1000 μg/ml) to obtain a sample solution.
Sample volume for all the compounds was fixed at 0.1 ml. The cups were made by scooping
out agar medium with a sterilized cork borer in a Petri dish, which was previously inoculated
with the microorganisms. The solution of each test compound (0.1 ml) was added to the cups

Journal of Sulfur Chemistry 227
Table 1. Antibacterial activity of the tested compounds.
Zone of inhibition (mm)
Gram-positive bacteria
Gram-negative bacteria
Compound
Control
S. aureus
B. subtilis
P. aeruginosa
E. coli
DMF
DMF
DMF
DMF
Ampicillin
Streptomycin
2
3a
3b
3c
4
5
6
22
23
15
14
12
15
15
10
12
10
11
15
15
14
10
13
11
25
21
15
15
15
15
16
15
15
14
11
12
10
12
11
14
15
22
20
14
11
14
11
11
12
13
10
13
12
14
10
12
13
12
19
24
12
15
12
13
12
13
16
11
12
15
13
11
11
13
10
7
8
9a
9b
10
11
12
13
and Petri dishes and was subsequently incubated at 37◦C for 48 h. Ampicillin and streptomycin
were used as reference drugs and DMF as a control. The zone of inhibition produced by each
compound was measured in millimeter. As shown in Table 1, all tested compounds displayed
significant activities against S. aureus, B. subtilis, P. aeruginosa and E. coli, while only com-
pounds 4 and 6 were very active against B. subtilis and E. coli, when compared with standard
drugs.
3.2. Antifungal activity
The antifungal activity of the synthesized compounds was tested against four different fungi, i.e.
Candida albicans, Candida pannical, Aspergillus niger and Rhizopus oryzae by a filter paper disc
technique (23). The concentration of test compounds was 1000 μg/ml. After treatment for 48 h,
the zone of inhibition produced by each compound was measured in millimeter. Griseofulvin was
used as the standard antifungal agent and DMF as a control. The results of antifungal activity are
depicted in Table 2. Compounds 3b and 3c were very active against C. pannical and A. niger
while other compounds showed slight to moderate antifungal activity.
4. Conclusion
In conclusion, a new series of 2-(3-chloro-1-benzothiophen-2-yl)-3-(substituted-phenyl)-4-(3H)-
quinazolinones derivatives were synthesized, fully characterized and evaluated for their antibacte-
rialandantifungalactivities.Thenewlysynthesizedheterocyclicsexhibitedmoderateantibacterial
activity against S. aureus, B. subtilis, P. aeruginosa and E. coli and significant antifungal activity
against C. albicans, C. pannical and A. niger. It can be concluded that these classes of compounds
certainly hold great promise toward good active leads in medicinal chemistry. A further study to
acquire more information concerning pharmacological activity is in progress.

228 G. Naganagowda and A. Petsom
Table 2. Antifungal activity of the tested compounds.
Zone of inhibition (mm)
Compound
C. albicans
C. pannical
A. niger
R. oryzae
Control
DMF
DMF
DMF
DMF
Griseofulvin
2
3a
3b
3c
4
5
6
7
8
9a
9b
10
11
12
13
23
15
14
13
11
16
13
12
11
10
13
14
13
14
12
11
24
14
13
14
17
15
10
12
13
11
10
13
10
13
11
16
22
12
11
17
10
14
11
14
10
12
12
14
10
12
11
15
20
15
10
13
11
10
13
11
16
12
12
11
11
11
10
11
5. Experimental
All chemicals were of analytical grade, purchased from commercial suppliers and used as received
without further purification. Melting points were determined in open capillary and were uncor-
rected. FTIR spectra (KBr discs) were recorded using a Perkin-Elmer 237 spectrophotometer.
1H-NMR spectra were recorded on a Bruker Supercon FT-NMR spectrometer (at 500 MHz) using
DMSO-d6 as a solvent. 13C-NMR spectra at 100 MHz were recorded on a Bruker model ACF200
spectrophotometer. All chemical shifts were reported in parts per million (ppm) using residual
proton or carbon signal in deuterated solvents as internal references. MS are recorded on Schi-
madzu GC-MS. Elemental analysis (C, H, N and S) was performed on Perkin Elmer 240 analyzer
and all products were purified by recrystallization. The purity of the compounds was checked by
TLC on silica gel and further purification was performed through column chromatography (silica
gel, 60–120 meshes).
5.1. Preparation of 3-chloro-1-benzothiophene-2-carbonyl chloride (1)
Compound 1 was prepared according to the literature procedure (21), mp 112–114◦C (lit. mp
110–112◦C).
5.2. Preparation of 2-(3-chloro-1-benzothiophen-2-yl)-4H-3,1-benzoxazin-4-one (2)
A mixture of 1 (2.31 g, 0.01 mol) and anthranilic acid (1.37 g, 0.01 mol) in dry pyridine (30 ml) was
refluxed for 3 h. After the completion of the reaction (TLC monitoring), the reaction mixture was
cooled down to room temperature and then poured into cold diluted HCl (10%). The precipitate
was filtered, dried and recrystallized from toluene to give pure product 2 as a light yellow solid.
Yield: 67%; mp 267◦C; IR υ (cm−1): 1710 (C=O), 1620 (C=N), 1570 (C=C), 1070 (9C–Cl),
1
680 (C–S–C); H-NMR δ (ppm): 8.12–7.40 (m, 8H, Ar-CH); 13C-NMR δ (ppm): 164, 159.4,
141.9, 135.2, 131.6, 128.2, 126.7, 126.5, 125.9, 124.4, 124.3, 124.1, 122.8, 122.0, 119.9, 116.8;
MS, m/z: 313.75 (M+). Anal. Calcd. for C16H8ClNO2S: C, 61.25; H, 2.57; N, 4.45; S, 10.22;
found: C, 61.22; H, 2.54; N, 4.44; S, 10.21%.

Journal of Sulfur Chemistry 229
5.3. General procedure for synthesis of compounds 3a-g. Exemplary detail for
2-(3-chloro-1-benzothiophen-2-yl)-3-(3-chloro-4-fluorophenyl)quinazolin-4(3H)-one
(3a)
A mixture of 2 (3.13 g, 0.01 mol) and 3-chloro-4-fluoroaniline (2.18 g, 0.015 mol) in glacial acetic
acid (20 ml) was refluxed for 4 h. The reaction mixture was poured into crushed ice. The precipitate
was filtered, dried and recrystallized from ethanol to get compound 3a. Compounds 3b–g were
prepared by a similar methodology.
Yield: 66%; mp 261◦C; IR υ (cm−1): 1715 (C=O), 1622 (C=N), 1200 (C–F), 710 (C–Cl);
1H-NMR δ (ppm): 8.12–7.10 (m, 11H, Ar–CH); 13C-NMR δ (ppm): 164.2, 160.3, 154.4, 133.4,
131.6, 129.7, 128.2, 127.3, 126.7, 126.6, 125.9, 124.4, 124.3, 123.6, 122.8, 122.1, 120.9, 120.8,
119.5, 113.6, 44.5; MS, m/z: 441.30 (M+). Anal. Calcd. for C22H11Cl2N2OS: C, 59.88; H, 2.51;
N, 6.35; S, 7.27; found: C, 59.85; H, 2.50; N, 6.33; S, 7.25%.
5.3.1. 2-(3-Chloro-1-benzothiophen-2-yl)-3-(4-fluorophenyl)quinazolin-4(3H)-one (3b)
Yield 59%; mp 255◦C; IR υ (cm−1): 1712 (C=O), 1625 (C=N), 1207 (C–F); 1H-NMR δ (ppm):
8.10–7.12 (m, 12H, Ar–CH); 13C-NMR δ (ppm): 164.1, 162.9, 160.6, 144.5, 133.4, 131.6, 130.1,
130.1, 128.3, 127.3, 126.7, 126.7, 126.6, 125.9, 124.4, 124.3, 122.8, 122.2, 120.8, 119.4, 115.7,
115.7; MS, m/z: 406.85 (M+). Anal. Calcd. for C22H12ClFN2OS: C, 64.95; H, 2.97; N, 6.89; S,
7.88; found: C, 64.93; H, 2.95; N, 6.85; S, 7.86%.
5.3.2. 2-(3-Chloro-1-benzothiophen-2-yl)-3-(4-nitrophenyl)quinazolin-4(3H)-one (3c)
Yield 76%; mp 240◦C; IR υ (cm−1): 1710 (C=O), 1624 (C=N), 1490 (Ar–NO2), 1072 (9C–Cl);
1H-NMR δ (ppm): 8.10–7.30 (m, 12H, Ar–CH); 13C-NMR δ (ppm): 164.6, 160.3, 144.5, 143.5,
138.8, 133.4, 131.6, 129.2, 129.2, 127.3, 126.7, 126.7, 126.6, 125.9, 124.4, 124.3, 124.1, 124.1,
122.8, 122.1, 120.8, 119.8; MS, m/z: 433.86 (M+). Anal. Calcd. for C22H12ClN3O3S: C, 60.90;
H, 2.97; N, 9.69; S, 7.39; found: C, 60.89; H, 2.95; N, 9.66, S, 7.38%.
5.3.3. 2-(3-Chloro-1-benzothiophen-2-yl)-3-(4-methylphenyl)quinazolin-4(3H)-one (3d)
Yield: 71%; mp 253◦C; IR υ (cm−1): 1714 (C=O), 1623 (C=N), 1071 (9C–Cl); 1H-NMR δ (ppm):
8.15–7.20 (m, 12H, Ar–CH), 2.35 (s, 3H, CH3); 13C-NMR δ (ppm): 164.3, 160, 144.5, 136.8,
133.4, 131.6, 129.7, 129.2, 129.2, 128.5, 128.5, 127.3, 126.7, 126.7, 126.6, 125.9, 124.4, 124.3,
122.8, 122.1, 120.8, 119.7, 21.5; MS, m/z: 402.89 (M+). Anal. Calcd. for C23H15ClOS: C, 68.57;
H, 3.75; N, 6.95; S, 7.96; found: C, 68.55; H, 3.70; N, 6.93; S,7.92%.
5.3.4. 2-(3-Chloro-1-benzothiophen-2-yl)-3-(4-methoxyphenyl)quinazolin-4(3H)-one (3e)
Yield: 70%; mp 243◦C; IR υ (cm−1): 1708 (C=O), 1621 (C=N), 1073 (9C–Cl); 1H-NMR δ (ppm):
8.10–7.33 (m, 12H, Ar–CH), 3.82 (s, 3H, OCH3); 13C-NMR δ (ppm): 164.5, 160.2, 158.9, 144.5,
133.4, 131.6, 128.8, 128.8, 127.3, 126.7, 126.7, 126.6, 125.9, 125.0, 124.4, 124.3, 122.8, 122.4,
120.8, 119.6, 114.5, 114.5, 55.6; MS, m/z: 418.89 (M+). Anal. Calcd. for C23H15ClN2O2S: C,
65.93; H, 3.61; N, 6.69; S, 7.65; found: C, 65.90; H, 3.60; N, 6.65; S, 7.62%.
5.3.5. 2-(3-Chloro-1-benzothiophen-2-yl)-3-(4-chlorophenyl)quinazolin-4(3H)-one (3f)
Yield: 69%; mp 233◦C; IR υ (cm−1): 1716 (C=O), 1625 (C=N), 1074 9C–Cl), 710 (C–Cl); 1H-
NMR δ (ppm): 8.20–7.45 (m, 12H,Ar–CH); 13C-NMR δ (ppm): 164.3, 160.1, 144.5, 133.4, 133.3,

230 G. Naganagowda and A. Petsom
131.6, 130.8, 130.9, 130.9, 129.0, 129.0, 127.3, 126.7, 126.7, 126.6, 125.9, 124.4, 124.3, 122.8,
122.3, 120.8, 119.9; MS, m/z: 423.31 (M+). Anal. Calcd. for C22H12ClN2OS: C, 62.42; H, 2.86;
N, 6.62; S, 7.57; found: C, 62.41; H, 2.81; N, 6.61; S, 7.53%.
5.3.6. 2-(3-Chloro-1-benzothiophen-2-yl)-3-(4-nitrophenyl)quinazolin-4(3H)-one (3g)
Yield: 68%; mp 243◦C; IR υ (cm−1): 1713 (C=O), 1622 (C=N), 1490 (Ar–NO2), 1069 (9C–Cl);
1H-NMR δ (ppm): 8.14–7.30 (m, 12H, Ar–CH); 13C-NMR δ (ppm): 164.6, 160.6, 144.5, 142.4,
135.0, 133.4, 133.3, 131.6, 126.7, 126.7, 127.3, 126.6, 125.9, 125.3, 125.2, 124.4, 124.3, 122.8,
122.5, 122.3, 120.8, 119.9; MS, m/z: 433.8 (M+). Anal. Calcd. for C22H12ClN3O3S: C, 60.90;
H, 2.97; N, 9.69; S, 7.39; found: C, 60.88; H, 2.95; N, 9.65; S, 7.35%.
5.4. Preparation of 2-(3-chloro-1-benzothiophen-2-yl)-3-hydroxyquinazolin-4(3H)-one (4)
A mixture of 2 (3.13 g, 0.01 mol), hydroxylamine hydrochloride (1.04 g, 0.015 mol) in glacial
aceticacid(20 ml)wasrefluxedfor4 h.Thereactionmixturewascooleddowntoroomtemperature
and poured onto crushed ice. The resulting precipitate was filtered, dried and recrystallized from
ethanol to get pure compound 4.
Yield: 67%; mp 231◦C; IR υ (cm−1): 3473 (OH), 1711 (C=O), 1620 (C=N); 1H-NMR δ (ppm):
10.47 (s, 1H, OH), 8.15–7.26 (m, 8H, Ar–CH); 13C-NMR δ (ppm): 163.8, 163.2, 144.5, 133.4,
131.6, 127.3, 126.7, 126.7, 126.6, 125.9, 124.4, 124.3, 122.8, 122, 120.8, 119.9; MS, m/z: 328.77
(M+). Anal. Calcd. for C16H9ClN2O2S: C, 58.45; H, 2.76; N, 8.52; S, 9.75; found: C, 58.40; H,
2.74; N, 8.51; S, 9.71%.
5.5. Preparation of 3-(acetyloxy)-2-(3-chloro-1-benzothiophen-2-yl)quinazolin-4(3H)-one(5)
A solution of compound 4 (3.28 g, 0.01 mol) in freshly distillated acetic anhydride (20 ml) was
gently refluxed for 2 h. The reaction solution was left to cool down to room temperature and
the resulting precipitate was filtered off, washed several times with light petroleum ether, dried
and then recrystallized from 1,4-diaxone. Purification by column chromatography [silica-gel,
petroleum ether/ethyl acetate (5:95)] yielded pure 5.
1
Yield: 77%; mp 255◦C; IR υ (cm−1): 1708, 1671 (C=O), 1625 (C=N); H-NMR δ (ppm):
8.14–7.15 (m, 8H, Ar–CH), 2.30 (s, 3H, CH3); 13C-NMR δ (ppm): 167.4, 164.1, 163.5, 144.5,
133.4, 131.6, 127.3, 126.7, 126.7, 126.6, 125.9, 124.4, 124.3, 122.8, 122, 120.8, 119.9, 19.2; MS,
m/z : 371.12 (M+). Anal. Calcd. for C18H11ClN2O3S: C, 58.30; H, 2.99; N, 7.55; S, 8.65; found:
C, 58.28; H, 2.95; N, 7.53; S, 8.63%.
5.6. Preparation of 2-(3-chloro-1-benzothiophen-2-yl)quinazolin-4(3H)-one (6)
A mixture of benzoxazin-4-one 2 (3.13 g, 0.01 mol) and formamide (10 ml) was refluxed for 3 h.
After cooling down to room temperature, the mixture was poured onto crushed ice. The resulting
precipitate was filtered, dried and recrystallized from ethanol. The solid was repurified by column
chromatography [silica, petroleum ether/ethyl acetate (80:20)], leading to pure 6.
Yield: 75%; mp 269◦C; IR υ (cm−1): 3170 (N–H), 1715 (C=O), 1628 (C=N); 1H-NMR δ (ppm):
11.29 (s, 1H, NH), 8.42–7.18 (m, 8H, Ar–CH); 13C-NMR δ (ppm): 164.6, 161.1, 144.5, 133.4,
131.6, 127.3, 126.7, 126.7, 126.6, 125.9, 124.4, 124.3, 122.8, 122, 120.8, 119.5; MS, m/z: 312.77
(M+). Anal. Calcd. for C16H9ClN2OS: C, 61.44; H, 2.90; N, 8.96; S, 10.25; found: C, 61.41; H,
2.88; N, 8.93; S, 10.21%.

Journal of Sulfur Chemistry 231
5.7. Preparation of 3-amino-2-(3-chloro-1-benzothiophen-2-yl)quinazolin-4(3H)-one (7)
A mixture of 2 (3.13 g, 0.01 mol) and hydrazine hydrate (0.01 mol) in glacial acetic acid (10 ml)
was refluxed for 10 h. The completion of the reaction was monitored by TLC technique. After
completion, the reaction mixture was cooled down to room temperature and then added to crushed
ice (100 g). The precipitate was filtered and recrystallized from ethanol. Purification by column
chromatography [silica, petroleum ether/ethyl acetate (70:30)] gave pure 7.
Yield: 67%; mp 276◦C; IR υ (cm−1): 3130 (NH2), 1723 (C=O), 1628 (C=N); 1H-NMR δ (ppm):
8.12–7.45 (m, 8H,Ar–CH), 5.68 (2H, NH2); 13C-NMR δ (ppm): 164.3, 160.1, 144.5, 133.4, 131.6,
127.3, 126.7, 126.7, 126.6, 125.9, 124.4, 124.3, 122.8, 122, 120.8, 119.9; MS, m/z: 327.78 (M+).
Anal. Calcd. for C16H10ClN3OS: C, 58.63; H, 3.07; N, 12.82; S, 9.78; found: C, 58.59; H, 3.05;
N, 12.79; S, 9.75%.
5.8. Preparation of 2-chloro-N-[2-(3-chloro-1-benzothiophen-2-yl)-4-oxoquinazolin-
3(4H)-yl] acetamide (8)
Compound 7 (3.27 g, 0.01 mol) was reacted with chloroacetyl chloride (1.12 g, 0.81 ml, 0.01 mol)
in pyridine (10 ml) under reflux for about 2 h. The reaction mixture was then poured over an
ice/HCl mixture. The resulting precipitate was filtered and recrystallized from toluene to get
pure 8.
Yield: 65%; mp 266◦C; IR υ (cm−1): 3250 (N–H), 1713, 1668 (C=O), 1622 (C=N); 1H-NMR
δ (ppm): 10.64 (s, 1H, NH), 8.13–7.67 (m, 8H, Ar–CH), 4.16 (s, 2H, CH2); 13C-NMR δ (ppm):
166.2, 164.4, 160.1, 144.5, 133.4, 131.6, 127.3, 126.7, 126.7, 126.6, 125.9, 124.4, 124.3, 122.8,
122, 120.8, 119.9, 40.5; MS, m/z: 404.26 (M+). Anal. Calcd. for C18H11Cl2N2O2S: C, 53.48; H,
2.74; N, 10.39; S, 7.93; found: C, 53.44; H, 2.72; N, 10.36; S, 7.91%.
5.9. General procedure for synthesis of compounds 9a–b. Exemplary detail for
N-[2-(3-chloro-1-benzothiophen-2-yl)-4-oxoquinazolin-3(4H)-yl]acetamide (9a)
Compound 7 (3.27 g, 0.01 mol) was treated with benzoyl chloride (1.40 g, 1.15 ml, 0.01 mol) in
dry acetone (30 ml) under reflux for 3 h. Excess of solvent was removed and the solid obtained,
filtered, dried recrystallized from 1,4-diaxone. Purification by column chromatography [silica,
petroleum ether/ethyl acetate (50:50)] afforded pure white crystal of 9a. Similarly, compound 9b
was prepared with little change in refluxed time and reaction work-up.
Yield: 66%; mp 259◦C; IR υ (cm−1): 3150 (N–H), 1719 (C=O), 1642 (C=O, CONH), 1629
1
(C=N); H-NMR δ (ppm): 10.72 (s, 1H, CONH), 8.32–7.89 (m, 8H, Ar–CH), 2.01 (s, 2H,
CH3); 13C-NMR δ (ppm): 168, 164.3, 160.1, 144.3, 133.4, 131.6, 127.3, 126.7, 126.7, 126.6,
125.9, 124.4, 124.3, 122.8, 122, 120.8, 119.9, 20.3; MS, m/z: 369.82 (M+). Anal. Calcd. for
C18H12ClN3O2S: C, 58.46; H, 3.27; N, 11.36; S, 8.67; found: C, 58.40; H, 3.22; N, 11.31;
S, 8.62%.
5.9.1. N-[2-(3-Chloro-1-benzothiophen-2-yl)-4-oxoquinazolin-3(4H)-yl]benzamide (9b)
Yield: 64%; mp 273◦C; IR υ (cm−1): 3150 (N–H), 1711 (C=O), 1639 (C=O, CONH), 1623 (C=N),
1570 (C=C), 686 (C–S–C); 1H-NMR δ (ppm): 11.03 (s, 1H, CONH), 8.18–7.34 (m, 13H,Ar–CH);
13C-NMR δ (ppm): 164.5, 164.3, 160.2, 144.5, 133.4, 132.1, 132.0, 131.6, 128.8, 128.8, 127.5,
127.5, 127.3, 126.7, 126.7, 126.6, 125.9, 124.4, 124.3, 122.8, 122, 120.8, 119.4; MS, m/z: 431.80
(M+). Anal. Calcd. for C23H14ClN3O2S: C, 63.93; H, 3.27; N, 9.73; S, 7.42; found: C, 63.91; H,
3.22; N, 9.70; S, 7.39%.

232 G. Naganagowda and A. Petsom
5.10. Preparation of {[(2-{[(3-chloro-1-benzothiophen-2-yl)carbonyl]amino}
phenyl)carbonyl]sulfanyl}acetic acid (10)
A mixture of benzoxazin-4-one 2 (3.13 g, 0.01 mol) and thioglycolic acid (0.92 g, 0.91 ml,
0.01 mol) in dry benzene (30 ml) was refluxed for 13 h. The reaction mixture was concentrated to
dryness and the residue was recrystallized from ethanol to give a pure compound 10.
Yield: 63%; mp 280◦C; IR υ (cm−1): 3120 (N–H), 1722, 1710 (C=O), 1640 (C=O, CONH);
1H-NMR δ (ppm): 12.50 (s, 1H, OH), 10.16 (s, 1H, CONH), 8.12–7.24 (m, 8H, Ar–CH), 2.86
(s, 2H, SCH2); 13C-NMR δ (ppm): 191.3, 173.2, 161.4, 141.6, 138.5, 135.9, 134.3, 133.4, 129.9,
126.7, 125.8, 124.5, 124.4, 124.3, 122.8, 119.5, 117.1, 39.1; MS, m/z: 405.55 (M+). Anal. Calcd.
for C18H12ClNO4S2: C, 53.27; H, 2.98; N, 3.45; S,15.80; found: C, 53.24; H, 2.91; N, 3.42; S,
15.79%.
5.11. Preparation of N-[2-({2-[(amino-sulfanylidyne) methyl] hydrazine} carbonyl)
phenyl]-3-chloro-1-benzothiophene-2-carboxamide (11)
A mixture of 2 (3.13 g, 0.01 mol) and thiosemicarbazide (0.91 g, 0.01 mol) in glacial acetic acid
(20 ml) was refluxed for 5 h. The completion of the reaction was monitored by TLC technique.
After completion, the reaction mixture was cooled down to room temperature and then added to
crushed ice (100 g). The resulting precipitate was filtered and recrystallized from 1,4-diaxone to
get pure compound 11.
Yield: 62%; mp 280◦C; IR υ (cm−1): 3130 (N–H), 1721 (C=O), 1632 (C=O, CONH), 1218
(C=S); 1H-NMR δ (ppm): 10.68 (s, 1H, CONH), 10.20 (s, 1H, CONH), 9.47 (s, 2H, NH2), 8.14–
7.13 (m, 8H, Ar–CH), 1.96 (s, 1H, CSNH); 13C-NMR δ (ppm): 182.2, 164.3, 161.4, 141.5, 137.6,
135.3, 133.1, 132.3, 129.9, 127.7, 126.7, 124.4, 124.4, 124.3, 123.2, 122.8, 119.4; MS, m/z:
404.89 (M+). Anal. Calcd. for C17H13ClN4O2S2: C, 50.43; H, 3.24; N, 13.84; S, 15.84; found:
C, 50.41; H, 3.20; N, 13.80; S, 15.80%.
5.12. Preparation of N-{2-[(2-aminophenyl)carbamoyl]phenyl}-3-chloro-1-
benzothiophene-2-carboxamide (12)
A mixture of benzoxazin-4-one 2 (3.13 g, 0.01 mol) and o-phenylenediamine (1.08 g, 0.01 mol)
in ethanol (20 ml) was refluxed for 5 h. The excess of alcohol was removed and the reaction
mixture was left to cool. The solid that obtained was filtered, dried and recrystallized from
methanol. Purification by column chromatography [silica, petroleum ether/ethyl acetate (5:95)]
led to pure 12.
Yield: 61%; mp 241◦C; IR υ (cm−1): 3345 (Ar–NH2), 3046 (N–H), 1710 (C=O), 1634 (C=O,
1
AMIDE); H-NMR δ (ppm): 10.22 (s, 1H, CONH), 9.46 (s, 1H, CONH), 8.12–7.25 (m, 12H,
Ar–CH), 5.16 (2H, NH2); 13C-NMR δ (ppm): 167.1, 161.7, 149.2, 141.6, 137.9, 135.9, 133.4,
132.3, 129.9, 127.7, 126.7, 125.5, 125.1, 124.4, 124.4, 124.3, 123.2, 122.8, 122.8, 119.4, 118.9,
114.5; MS, m/z: 421.80 (M+). Anal. Calcd. for C23H14ClN3O2S: C, 63.93; H, 3.27; N, 9.73; S,
7.42; found: C, 63.90; H, 3.24; N, 9.71; S, 7.40%.
5.13. Preparation of 3-(2-aminophenyl)-2-[(3-chloro-1-benzothiophen-2-yl)carbonyl]
quinazolin-4(3H)-one (13)
A mixture of 2 (3.13 g, 0.01 mol) and o-phenylenediamine (1.08 g, 0.01 mol) and anhydrous
sodium acetate (0.5 g, 0.01 mol) in glacial acetic acid (20 ml) was refluxed for 4 h. The reaction
mixture was cooled down to room temperature and then poured onto crushed ice. The solid was

Journal of Sulfur Chemistry 233
filtered, dried and recrystallized from methanol. Purification by column chromatography [silica,
petroleum ether/ethyl acetate (10:90)] yielded pure 13.
Yield: 69%; mp 266◦C; IR υ (cm−1): 3345 (Ar–NH2), 1722 (C=O), 1639 (C=O, AMIDE);
1H-NMR δ (ppm): 8.23–7.32 (m, 12H,Ar–CH), 5.24 (2H, NH2); 13C-NMR δ (ppm): 164.2, 160.1,
144.3, 134.1, 133.4, 131.6, 126.8, 126.7, 126.7, 127.3, 126.6, 125.9, 125.1, 124.4, 124.3, 122.8,
122, 120.8, 119.9, 118.9, 114.7, 114.5; MS, m/z: 431.75 (M+).Anal. Calcd. for C22H16ClN3O2S:
C, 62.63; H, 3.82; N, 9.96; S, 7.60; found: C, 62.60; H, 3.80; N, 9.92; S, 7.58%.
Acknowledgement
The authors are thankful for being provided laboratory facilities to carry out the synthesis and pharmacological activity
of the compounds.
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