Synthesis and in vitro cytotoxicity evaluation of new 2-thioxo-benzo[g]quinazolin-4(3h)-one derivatives

Article abstract of DOI:10.3987/COM-15-13282

Preparation of the titled 2-thioxo-benzo[g]quinazolin-4(3H)-ones (1-4) has been previously reported. In the present study, compounds (1-4) were elaborated in high and quantitative yields by simple modification on the reported synthetic route. Treatment of 2-thioxo-benzo[g]quinazolin-4(3H)-ones (1-4) with hydrazine hydrate or with different alkyl(heteroalkyl) halides afforded smoothly the target products 5, 6 or 7-28 in good and high yields. The in vitro cytotoxicity of compounds 1-28 was evaluated against colon HCT-116, hepatocellular Hep-G2, and breast MCF-7, prostate PC-3 and lung A-549 cancer cell lines, using MTT assay. The IC50-values of the target compounds are recorded in μg/mL and doxorubicin used as a reference drug. The results revealed that compounds 1, 3, 7, 10, 13, 14, 15, 16, 20, 21 and 22 had significant cytotoxic effects in relation to the reference drug. The structures of compounds 1-28 were elucidated by means of ¹H- and ¹³C-NMR and HREI mass spectrometry.

Full text of DOI:10.3987/COM-15-13282

HETEROCYCLES, Vol. 91, No. 9, 2015
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HETEROCYCLES, Vol. 91, No. 9, 2015, pp. 1735 - 1751. © 2015 The Japan Institute of Heterocyclic Chemistry
Received, 8th July, 2015, Accepted, 30th July, 2015, Published online, 6th August, 2015
DOI: 10.3987/COM-15-13282
SYNTHESIS AND IN VITRO CYTOTOXICITY EVALUATION OF NEW
2-THIOXO-BENZO[g]QUINAZOLIN-4(3H)-ONE DERIVATIVES
Rashad Al-Salahi,a* Rabab A. El Dib, b,c and Mohamed Marzouk a,d*
a
Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud
University, P.O. box 2457, Riyadh 11451, Saudi Arabia; Email:
salahi76@yahoo.com, msmarzouk@yahoo.co.uk
b
Department of Pharmacognosy, Faculty of Pharmacy, Helwan University, Cairo
11795, Egypt
c
Department of Pharmacognosy, College of Pharmacy, King Saud University,
P.O. Box 22452, Riyadh 11495, Saudi Arabia
d
Chemistry of Natural Products Group, Center of Excellence for Advanced
Sciences, National Research Centre, Dokki, Cairo 12622, Egypt
Abstract – Preparation of the titled 2-thioxo-benzo[g]quinazolin-4(3H)-ones
(1–4)ꢀ has been previously reported. In the present study, compounds (1–4) were
elaborated in high and quantitative yields by simple modification on the reported
synthetic route. Treatment of 2-thioxo-benzo[g]quinazolin-4(3H)-ones (1–4) with
hydrazine hydrate or with different alkyl(heteroalkyl) halides afforded smoothly
the target products 5, 6 or 7–28 in good and high yields. The in vitro cytotoxicity
of compounds 1–28 was evaluated against colon HCT-116, hepatocellular
Hep-G2, and breast MCF-7, prostate PC-3 and lung A-549 cancer cell lines, using
MTT assay. The IC50-values of the target compounds are recorded in μg/mL and
doxorubicin used as a reference drug. The results revealed that compounds 1, 3, 7,
10, 13, 14, 15, 16, 20, 21 and 22 had significant cytotoxic effects in relation to the
reference drug. The structures of compounds 1–28 were elucidated by means of
1H- and 13C-NMR and HREI mass spectrometry.
INTRODUCTION
Even though there are many therapeutic strategies, including chemotherapy have been developed for
treatment of cancer and much progress has been made to understand its biology, cancer is still a serious

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HETEROCYCLES, Vol. 991, No.. 99, 2015
threat to human health worldwide. Design and developing of new bioactive molecules is one of the most
important research areas in the field of medicinal chemistry. Many chemotherapeutic agents were
examined, but some of them have been found unsuitable for therapeutic application due to their
carcinogenic and mutagenic effects.1,2 Numerous research studies and several review articles have
appeared in literature describing in detail the chemical and biological properties of benzoquinazolines.3-9
Many of benzoquinazolines played an important role in construction of many bioactive compounds used
as thymidylate synthase inhibitors,10 antiviral,11 antiinflammatory,12 antidepressive,13 analgesic,14
antineoplastic and antimonoamine oxidase agents.15 Currently, high systemic toxicity and drug resistance
accompanied with anticancer agents limit the successful findings in most cases. Consequently, a
number of new strategies are being developed to make structural modifications to newly elaborated active
compounds in order to improve their therapeutic indices and reduce their toxicity.
In continuation of research on benzoquinazolines chemistry and as a part of our interest in the search for
active anticancer agents, we report herein the synthesis and study of the cytotoxic effects of a new series
of 2-thioxo-benzo[g]quinazolin-4(3H)-one derivatives (1–28).
RESULTS AND DISCUSSION
Procedure for synthesis of benzo[g]quinazolines 1–4 (Scheme 1) has been reported in the literature,16,17
and simply modified by our research group to obtain the final products in highly or quantitative yields.
We have used N,N-dimethylformamide (DMF) as solvent for increasing the solubility of
3-amino-2-naphthoic acid and triethylamine as basic medium for the reaction. The structure of
compounds 1-3 was characterized by NMR and HRMS analyses.
The new compounds (4–28) presented in this study retain the basic skeleton of benzo[g]quinazoline with
an alkyl(aryl) substituent linked to the N-atom at position 3. Hydrazinolysis of compounds 1 and 2 in
DMF under reflux condition for 24 h furnished the corresponding compounds 5 and 6 in good yields.
To prepare the benzo[g]quinazoline derivatives (7–28), each of compounds 1‒3 was individually allowed
to react with an appropriate alkyl(heteroalkyl) halide in the presence of K2CO3 at 80 oC for 20 h in DMF
(Scheme 1). The benzo[g]quinazolines 7–28 were obtained as amorphous powder of different colours in
good to high yields and their structures were confirmed by NMR and HRMS spectrometry.
It is worth mentioning that all benzo[g]quinazolin-4(3H)-ones were newly synthesized except for their
three 2-thioxo derivatives (1‒3) and compound 22, which have been reported in the literature.16,17 The
synthesis of all products was established through reporting of the physical properties and their identities
were proved by the determination of their accurate molecular masses using HREI-MS analysis.

HETEROCYCLES, Vol. 91, No. 9, 2015
1737
O
O
N
O
R
N
R
NH2NH2
reflux, 24 h
N
OH
R-NCS, DMF, Et3N
reflux, 3-5 h
N
H
NH2
S
NH
NH2
1 (R= butyl)
2 (R= allyl)
3 (R= phenyl)
98%
95%
90%
5 (R=butyl) 72%
6 (R=allyl) 70%
4 (R=cyclohexyl) 31%
O
O
R
R
R1-X, DMF, K2CO3
80 oC, 20 h
N
N
N
S
R1
N
S
H
7-15 (R=butyl)
16-21 (R=allyl)
22-28 (R=phenyl)
1 (R= butyl)
2 (R=allyl)
3 (R= phenyl)
Scheme 1. Synthetic routes for 2-thioxo-benzo[g]benzoquinazolines (1-28)
Table 1. Synthesized 2-thioxo-benzo[g]quinazolines (7-28)
R1
ethyl
Yields (%)
16 (88)
17 (79)
19 (78)
20 (62)
21 (71)
26 (80)
18 (81)
12 (87)
24 (84)
9 (82)
7 ( 73)
8 (85)
22 (72)
23 (77)
25 (81)
27 (72)
28 (69)
allyl
4-chlorobenzyl
2-morpholinoethyl
3-(phthalimid-2-yl)propyl
2-piperidinoethyl
3-methoxybenzyl
4-cyanobenzyl
3-cyanobenzyl
benzyl
11 (74)
14 (88)
15 (90)
13 (86)
10 (85)
1
Final confirmation of the chemical structures was achieved by H- and 13C NMR spectroscopy and
matching with the corresponding data of structurally related compounds in the literature.18-20 Basically,
the essential building of the benzo[g]quinazoline structure was simply deduced from the three pairs of
identical two signals each, in the range of δ 8.85‒7.50 ppm in the 1H NMR spectra for all products (1‒28).

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HETEROCYCLES, Vol. 991, No.. 99, 2015
The first pair was interpreted at about δ 8.80 and 8.20 in the form of two singlets, describable for H-5 and
H-10 of the inner benzene ring.19 In addition, the other two pairs of aromatic signals were described as
two broad-doublets at about δ 8.20 and 8.10 for H-6 and H-9 and two broad-triplets at about δ 7.66 and
7.55 for H-8 and H-7, respectively, of the outer benzene ring. Similar pattern was observed in case of
the 2-thioxo (1‒4) and 2-hydrazinyl (5,6) derivatives with slight upfield shift of all corresponding
1
resonances. Moreover, H NMR spectra of 2-thioxo derivatives (1‒4) showed a characteristic singlet of
the –NH– proton at about δ 13.00, while in case of 2-hydrazinyl derivatives (5,6), two singlets were
assigned at about δ 9.50 and 6.10, that were indicative for –NH– and –NH2 protons of the hydrazinyl
group. In 13C NMR spectra of all products, twelve resonances were observed for the basic
benzoquinazoline-4-one structure in the range of about δ 175.0‒111.0 ppm, including the most downfield
shifted signals of C-2 and C-4 and most upfield ones C-7 and C-10, whereby all compounds could be
sorted into three groups according to their δ-values. In the first group i.e. 2-thioxo derivatives (1‒4),
thioxo and carbonyl carbons were recorded at about δ 174.0 (C-2) and 160.0 (C-4), while the most upfield
carbons were observed at about 116.0 (C-7) and 111.0 (C-10). In contrast, the carbonyl-C (C-4) and
hydrazinyl-C (C-2) were recorded at 158.9 and 148.0 in case of the 2-hydrazinyl derivatives (5,6), while
C-7 and C-10 were interpreted at about 116.0 and 113.0, respectively. Whereas, the largest group of
2-thio-derivatives (7‒28) was differentiated from previous groups by the location of their carbonyl-C
(C-4) and thio-C (C-2) at about δ 161.0 and 156.0 ppm along with C-7 and C-10 at about 123.0 and 119.0,
respectively. Unambiguous conclusion for all structures was finally obtained from the intrinsic splitting
pattern (multiplicity and J-values) and δ-values of 1H- and 13C-signals for the substituent/s at C-2 and C-3
in each case (ethyl, butyl, allyl, phenyl, cyclohexyl, piperidinoethyl, morpholinoethyl, phthalimidopropyl
and benzyl or their derivatives), see experimental data. As an instance, all butyl derivatives (1, 5 &
1
7‒15) exhibited the characteristic H resonances at about δ 4.0 (t), 1.70 (m), 1.40 (m) and 0.95 (t) for
13
H-1" to H-4" and the corresponding C resonances at about δ 44.0, 30.0, 20.1 and 14.0 interpretable for
1
C-1" to 4", respectively.18-20 Similarly, piperidinoethyl group showed five characteristic H resonances
at about 3.50 (t, CH2-7'), 2.70 (t, CH2-8'), 2.50 (m, H-2'/6'), 1.40 (m, 4H, H-3'/5') and 1.38 (m, H-4')
13
alongside their own C-signals at about δ 54.2 (CH2-7'), 30.2 (CH2-8'), 54.3 (C-2'/6'), 26.1 (C-3'/5') and
24.5 in products 13 and 26.
In addition, in case of the 2-S-aromatic substituted products (10‒12, 18, 19, 24 and 25), the presence of
certain substituents, such as ‒Cl, ‒CN or ‒OMe, played an essential role in proving their identities based on
their additive shift effects controlled by their inductive effect (I-effect) and/or resonance effect (R-effect),
anisotropy and their positions that reflected through increment additive rules.18-20 Such effects would be
very effective if we compare the –CN increment effects in the splitting pattern and δ-values of aromatic
resonances of the benzyl group in both compounds 12 and 25 together with the distinct resonance of
CN-carbon at about 119.0 ppm. The symmetrical position of ‒Cl in the structures of 11, 19 and 25 resulted

HETEROCYCLES, Vol. 91, No. 9, 2015
1739
in the appearance of aromatic protons in the form of a pair of two ortho-doublets each of 2H observed as an
A2M2-spin coupling system at about δ 7.60 (H-3'/5') and 7.40 (H-2'/6') and proper δ-values for C-4' and
C-1' at about 136.8 and 132.5, respectively. The 3-OMe substitution showed also drastic effect on the
13C-resonances of benzyl group-carbons in case of products 10 and 18, whereby C-3' was strongly
downfield shifted to 159.7 (∆= + 30 ppm) and C-2' and C-4' strongly upfield shifted to 115.5 and 113.4 (∆=
– 10 ppm), respectively. The success of the reaction with phthalic anhydride to produce 15, 21 and 28 was
proved by the characteristic resonances of the planar symmetric structure of propylisoindoline moiety at
7.88 (m, 5'/6', 4'/7'), 3.79 (t, CH2-7'), 3.36 (t, CH2-9') and 2.14 (quint, CH2-8') together with their own
13C-resonances at δ 168.5 (C-1'/3'), 134.9 (C-3a'/7a'), 132.1 (C-5'/6'), 123.5 (C-4'/7'), 41.4 (CH2-7'), 36.5
(CH2-9') and 29.2 (CH2-8').
The in vitro cytotoxicity of compounds 1–28 was evaluated against PC-3, A-549, HCT-116, Hep-G2 and
MCF-7 cells, using MTT assay.21 The obtained IC50-values of target compounds are summarized in Table
2 in comparison with those of doxorubicin. Most of the synthesized compounds showed significant
cytotoxicity against all tested cell lines in relation to the reference drug. Compounds 3, 7, 9, 10, 14, 15 and
20 exhibited the highest cytotoxicity against HCT-116 (IC50 = 1.92–3.78 μg/mL); 14 and 20 against
Hep-G2 and PC-3 (IC50 = 2.52/2.65 and 3.1/5.3 μg/mL, respectively); 3, 13, 20 against MCF-7 (IC50 =
4.66–6.82 μg/mL); 1–3, 5, 7, 9, 13, 14, 20, 21 and 26 against A-549 cells (IC50 = 3.1–6.22 μg/mL) in
comparison to the reference drug doxorubicin (IC50 = 0.46, 0.51, 0.78, 0.46 and 0.91 μg/mL). Within this
study, our results show that compounds 14 and 20 were the most active against all tested cell lines,
whereas compounds 15 and 19 were inactive against MCF-7.
Depending on the results compiled in Table 2, it can be concluded that the structural modifications on the
lead structures (1–3) may have had considerable impact on the cytotoxicity activity of all afforded
derivatives (5–28). In particular, alkylation of 1 into 7, 9, 10, 14 and 15 showed increment of the
cytotoxicity against HCT-116, and influenced positively effects on the activity profiles against Hep-G2,
PC-3 and A-549 indicated by 14. Similarly, conversion of 2 into 20 demonstrated the highest activity
against all cell lines. Hydrazinolysis of compounds 1 and 2 into 5 and 6, respectively did not exhibit
remarkable change of their activity. These results indicate that replacement of the thioxo by a hydrazinyl
group led to decrease in the lipophilicity of compounds 5 and 6, in relation to their parents. Variations in
the position of substitution on the benzyl ring affected their cytotoxicity as shown in case of 10–12, where
the presence of the methoxyl group in 10 showed remarkable increase in the cytotoxicity against all cell
lines in comparison to the corresponding chloro- and cyano-derivatives (11,12). Furthermore, we have
noticed that the type of alkyl or heteroalkyl groups play an important role in improvement of the
cytotoxicity as observed in compounds 7, 14 and 20. This could be attributed to the magnitude and
conformation of the alkyl or heteroalkyl substituents, which could be displayed a substantial role in the
cytotoxic effects.

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Moreover, all examined cell lines seemed to be sensitive to the antiproliferative activity of almost all
tested compounds, and it is noteworthy to point out that the higher sensitivity of all cell lines was noticed
towards compounds 14 and 20 followed by 1, 3, 7, 10, 13, 15, 16, 21 and 22.
Table 2. Cytotoxicity of the target compounds 1–28 (IC50, μg/mL)
Compound
IC50, μg/mL
HCT-116
5.65
4.99
3.17
8.77
4.38
5.94
2.64
4.58
3.76
3.71
5.79
9.53
5.08
1.92
3.78
24.8
5.49
10.7
Hep-G2
3.04
5.26
3.02
9.13
5.28
9.44
3.85
5.15
4.7
MCF-7
PC-3
20.1
18.0
20.0
9.65
35.6
43.1
12.0
19.5
37.8
7.17
17.8
34.0
2.96
3.1
A-549
3.55
5.67
4.83
12
10.0
18.2
5.58
22.6
16.0
23.7
21.4
11.6
26.8
17.2
19.5
32.9
6.82
11.0
>100
19.2
20.9
48.7
1
2
3
4
5.59
12.9
6.02
8.75
5.69
8.74
11.9
20.0
6.22
6.02
9.0
5
6
7
8
9
4.98
9.62
14.1
5.6
10
11
12
13
14
15
16
17
18
2.52
4.61
41.8
5.84
11.2
44.4
11.1
9.66
9.89
22.8
11.9
16.8

HETEROCYCLES, Vol. 91, No. 9, 2015
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5.52
2.48
11.2
5.95
10.9
23.4
7.74
5.19
5.6
5.87
2.65
4.6
>100
4.66
90.0
9.53
19.1
37.3
20.5
11.4
18.4
24.2
0.46
49.1
5.3
11.0
3.1
19
20
14.4
40.7
71.6
22.0
34.1
11.8
8.9
6.21
11.7
20.5
46.6
14.3
6.03
20.6
10.3
0.91
21
7.8
22
12.2
38.3
10.8
5.99
19.3
6.03
0.51
23
24
25
26
27
28
4.52
0.46
9.88
0.78
Doxorubicin
EXPERIMENTAL
General
Melting points were determined on open glass capillaries using a STUART Melting point SMP 10
apparatus and are uncorrected. NMR spectra were recorded on a Bruker AMX 500 spectrometer in
1
13
DMSO-d6 and are reported as δ ppm values relative to TMS at 500 and 125 MHz for H and C NMR,
respectively. J-Values are recorded in Hz. HREI-MS spectra were measured on a JEOL the MStation
JMS-700 system. Follow-up of the reactions and checking the purity of the compounds was made by TLC
on DC-Mikrokarten polygram SIL G/UV254, from the Macherey-Nagel Firm, Duren (Thickness: 0.25 mm).
General procedure for preparation of compounds 1-4
A mixture of alkyl(aryl) isothiocyanate (10.8 mmol), 3-amino-2-naphthoic acid (10 mmol) and
triethylamine (12 mmol) in DMF (20 mL) was heated to reflux for 2–5 h. The mixture was cooled and
poured onto ice-cold water. The solid was collected by filtration and dried.
3-Butyl-2,3-dihydro-2-thioxobenzo[g]quinazolin-4(1H)-one (1):16 pale yellow amorphous powder
(98%); mp 272–274 °C (DMF); 1H NMR (500 MHz, DMSO-d6): δ 12.99 (s, 1H, -NH-), 8.71 (s, 1H, H-5),
8.15 (br d, J = 8.5 Hz, 1H, H-6), 7.95 (br d, J = 8.5 Hz, 1H, H-9), 7.77 (s, 1H, H-10), 7.65 (br t, J = 7.5 Hz,

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HETEROCYCLES, Vol. 991, No.. 99, 2015
1H, H-8), 7.52 (br t, J = 7.5 Hz, 1H, H-7), 4.44 (t, J = 7.5 Hz, 2H, H-1'), 1.70 (m, 2H, H-2'), 1.37 (m, 2H,
H-3'), 0.95 (t, J = 7.5 Hz, 3H, H-4'); 13C NMR (125 MHz, DMSO-d6): δ 173.6 (C-2), 159.8 (C-4), 141.9
(C-4b), 136.6 (C-9a), 135.3 (C-5a), 130.0 (C-5), 129.9 (C-6), 129.8 (C-8), 127.7 (C-4a), 126.1 (C-9), 116.0
(C-7), 111.5 (C-10), 45.9 (C-1'), 29.2 (C-2'), 20.3 (C-3'), 14.2 (C-4'); HRMS (EI), m/z Calcd for
C16H16N2OS (M)•+ 284.0983, found 284.1003.
3-Allyl-2,3-dihydro-2-thioxobenzo[g]quinazolin-4(1H)-one (2):16 pale brown amorphous powder
(95%); mp 250–252 °C (DMF); 1H NMR (500 MHz, DMSO-d6): δ 13.05 (s, 1H, -NH-), 8.71 (s, 1H, H-5),
8.14 (br d, J = 8.5 Hz, 1H, H-6), 7.96 (br d, J = 8.5 Hz, 1H, H-9), 7.78 (s, 1H, H-10), 7.65 (br t, J = 7.5 Hz,
1H, H-8), 7.52 (br t, J = 7.5 Hz, 1H, H-7), 5.96 (m, 1H, H-2'), 5.20 (dd, J = 17.5, 1.5 Hz, 1H, H-3a'), 5.10
(dd, J = 10.5, 1.5 Hz, 1H, H-3b'), 4.00 (d, J = 5 Hz, 2H, H-1'); 13C NMR (125 MHz, DMSO-d6): δ 175.6
(C-2), 160.9, (C-4), 142.0 (C-4b), 136.6 (C-9a), 134.8 (C-5a), 132.3 (C-2'), 130.1 (C-5), 129.9 (C-6), 129.8
(C-8), 127.8 (C-4a), 126.2 (C-9), 117.5 (C-3'), 115.6 (C-7), 111.6 (C-10), 46.1 (C-1'); HRMS (EI), m/z
Calcd for C15H12N2OS (M)•+ 268.0670, found 268.0694.
2,3-Dihydro-3-phenyl-2-thioxobenzo[g]quinazolin-4(1H)-one (3):16 pale brown amorphous powder
(90%) mp 285–287 °C (DMF); 1H NMR (500 MHz, DMSO-d6): δ 13.14 (s, 1H, -NH-), 8.72 (s, 1H, H-5),
8.18 (br d, J = 8.5 Hz, 1H, H-6), 7.99 (br d, J = 8.5 Hz, 1H, H-9), 7.84 (s, 1H, H-10), 7.67 (br t, J = 7.5 Hz,
1H, H-8), 7.54 (br t, J = 7.5 Hz, 1H, H-7), 7.50 (m, J = 8 Hz, 3H, H-4', 2'/6'), 7.47 (m, 2H, H-3'/5'), 6.32 (br
t-like, J = 7.5 Hz, 1H, H-4'); 13C NMR (125 MHz, DMSO-d6): δ 176.6 (C-2), 160.3 (C-4), 143.0 (C-4b),
139.8 (C-1'), 136.7 (C-9a), 135.8 (C-5a), 130.1 (C-5), 130.0 (C- 3'/5'), 129.9 (C-6), 129.7 (C-8), 129.3
(C-4'), 128.6 (C-4a), 127.8 (C-2'/6'), 126.2 (C-9), 116.6 (C-7), 111.6 (C-10); HRMS (EI), m/z Calcd for
C18H12N2OS (M)•+ 304.0670, found 304.0697.
3-Cyclohexyl-2,3-dihydro-2-thioxobenzo[g]quinazolin-4(1H)-one (4): brown amorphous powder
(31%); mp 190–192 °C (DMF); 1H NMR (500 MHz, DMSO-d6): δ 12.95 (s, 1H, -NH-), 8.67 (s, 1H, H-5),
8.13 (br d, J = 8.5 Hz, 1H, H-6), 7.96 (br d, J = 8.5 Hz, 1H, H-9), 7.74 (s, 1H, H-10), 7.64 (br t, J = 7.5 Hz,
1H, H-8), 7.51 (br t, J = 7.5 Hz, 1H, H-7), 3.96 (m, 1H, H-1'), 1.73 (m, 4H, H-2'/6'), 1.65 (m, 4H, H-3'/5'),
1.28 (m, 2H, H-4'); 13C NMR (125 MHz, DMSO-d6): δ 173.8 (C-2), 160.0 (C-4), 142.0 (C-4b), 136.7
(C-9a), 135.2 (C-5a), 130.0 (C-5), 129.9 (C-6), 129.8 (C-8), 127.8 (C-4a), 126.0 (C-9), 116.1 (C-7), 111.6
(C-10), 53.1 (C-1'), 32.8 (C-2'/6'), 25.7 (C-4'), 25.0 (3'/5'); HRMS (EI), m/z Calcd for C18H18N2OS (M)•+
310.1139, found 246. 310.1162.
General procedure for preparation of compounds 5 and 6
Compound 1 or 2 (1 mmol) was heated under reflux with hydrazine hydrate (10 mmol) in DMF (15 mL)
for 24 h. After cooling, the precipitate was filtered off and washed with water to afford 5 or 6 as coloured
pure amorphous powder.

HETEROCYCLES, Vol. 91, No. 9, 2015
1743
3-Butyl-2-hydrazinylbenzo[g]quinazolin-4(3H)-one (5): pale green amorphous powder (72%); mp
206–208 °C (DMF); 1H NMR (500 MHz, DMSO-d6): δ 9.55 (s, 1H, -NH-), 8.66 (s, 1H, H-5), 8.39 (s, 1H,
H-10), 8.27 (br d, J = 8.5 Hz, 1H, H-6), 8.02 (br d, J = 8.5 Hz, 1H, H-9), 7.76 (br t, J = 8 Hz, 1H, H-8), 7.65
(br t, J = 8 Hz, 1H, H-7), 6.21 (s, 2H, -NH2), 4.22 (t, J = 7.5 Hz, 2H, H-1'), 1.78 (m, 2H, H-2'), 1.40 (m, 2H,
H-3'), 0.95 (t, J = 7.5 Hz, 3H, H-4'); 13C NMR (125 MHz, DMSO-d6): δ 158.9 (C-4), 148.0 (C-2), 144.6
(C-4b), 136.9 (C-9a), 135.7 (C-5a), 131.4 (C-5), 130.9 (C-6), 130.4 (C-8), 127.7 (C-4a), 127.3 (C-9), 116.3
(C-7), 113.3 (C-10), 42.9 (C-1'), 29.4 (C-2'), 20.0 (C-3'), 14.2 (C-4'); HRMS (EI), m/z Calcd for
C16H18N4O (M)•+ 282.1481, found 282.1498.
3-Allyl-2-hydrazinylbenzo[g]quinazolin-4(3H)-one (6): white amorphous powder (70%); mp 236–238
1
°C (DMF); H NMR (500 MHz, DMSO-d6): δ 9.53 (s, 1H, -NH-), 8.63 (s, 1H, H-5), 8.40 (s, 1H, H-10),
8.24 (br d, J = 8.5 Hz, 1H, H-6), 7.99 (br d, J = 8.5 Hz, 1H, H-9), 7.75 (br t, J = 8 Hz, 1H, H-8), 7.63 (br t,
J = 8 Hz, 1H, H-7), 6.23 (s, 2H, -NH2), 6.02 (m, 1H, H-2'), 5.29 (dd, J = 17.5, 1.5 Hz, 1H, H-3a'), 5.21 (dd,
J = 10.5, 1.5 Hz, 1H, H-3b'), 4.17 (d, J = 5 Hz, 2H, H-1'); 13C NMR (125 MHz, DMSO-d6): δ 158.8 (C-4),
147.8 (C-2), 144.6 (C-4b), 136.9 (C-9a), 135.6 (C-5a), 132.0 (C-2'), 131.4 (C-5), 130.4 (C-6), 129.1 (C-8),
127.6 (C-4a), 127.3 (C-9), 117.9 (C-3'), 116.1 (C-7), 113.2 (C-10), 45.1 (C-1'); HRMS (EI), m/z Calcd for
C15H14N4O (M)•+ 266.1167, found 266.1181.
General procedure for preparation of compounds 7-28
To a solution of 1, 2 or 3 (1 mmol) in DMF (7 mL), potassium carbonate (1.4 mmol) was added portion
wise over a period of 5 min at room temperature. After stirring for 10 min, an appropriate alkyl
(heteroalkyl) halide (1.3 mmol) was added, and the reaction mixture was heated for 20 h at 80 oC. The
mixture was then poured into ice/water, the formed precipitate was filtered off, washed with water and
dried.
3-Butyl-2-(ethylthio)benzo[g]quinazolin-4(3H)-one (7): white amorphous powder (73%); mp 126–128
°C, (DMF); 1H NMR (500 MHz, DMSO-d6): δ 8.79 (s, 1H, H-5), 8.18 (br d, J = 8.5 Hz, 1H, H-6), 8.10 (s,
1H, H-10), 8.08 (br d, J = 8.5 Hz, 1H, H-9), 7.65 (br t, J = 8 Hz, 1H, H-8), 7.55 (br t, J = 8 Hz, 1H, H-7),
4.06 (t, J = 7.5 Hz, 2H, H-1''), 3.31 (q, J = 7.5 Hz, 2H, H-1'), 1.70 (m, 2H, H-2''), 1.42 (t, J = 7.5 Hz, 3H,
H-2'), 1.39 (m, 2H, H-3''), 0.95 (t, J = 7.5 Hz, 3H, H-4''); 13C NMR (125 MHz, DMSO-d6): δ 161.3 (C-4),
155.8 (C-2), 142.8 (C-4b), 136.8 (C-9a), 130.9 (C-5a), 129.7 (C-5), 129.0 (C-6), 128.4 (C-8), 128.1 (C-4a),
126.4 (C-9), 123.2 (C-7), 118.9 (C-10), 43.9 (C-1"), 30.3 (C-2"), 26.5 (C-1'), 20.1 (C-3"), 14.5 (C-2'), 14.1
(C-4"); HRMS (EI), m/z Calcd for C18H20N2OS (M) •+ 312.1296, found 312.1303.
2-(Allylthio)-3-butylbenzo[g]quinazolin-4(3H)-one (8): pale brown amorphous powder (85%); mp
119–121 °C (DMF); 1H NMR (500 MHz, DMSO-d6): δ 8.79 (s, 1H, H-5), 8.18 (br d, J = 8.5 Hz, 1H, H-6),
8.11 (s, 1H, H-10), 8.07 (br d, J = 8.5 Hz, 1H, H-9), 7.65 (br t, J = 8 Hz, 1H, H-8), 7.55 (br t, , J = 8 Hz, 1H
H-7), 6.05 (m, 1H, H-2'), 5.48 (dd, J = 17.5, 1.5 Hz, 1H, H-3a'), 5.21 (dd, J = 10.5, 1.5 Hz, 1H, H-3b'), 4.06

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(t, J = 7.5 Hz, 2H, H-1''), 4.02 (d, J = 5 Hz, 2H, H-1'), 1.69 (m, 2H, H-2''), 1.39 (m, 2H, H-3''), 0.95 (t, J = 7.5
Hz, 3H, H-4''); 13C NMR (125 MHz, DMSO-d6): δ 161.3 (C-4), 155.2 (C-2), 142.6 (C-4b), 136.8 (C-9a),
133.5 (C-2'), 131.0 (C-5a), 129.8 (C-5), 129.1 (C-6), 128.4 (C-8), 128.1 (C-4a), 126.4 (C-9), 123.3 (C-7),
119.5 (C-3'), 118.9 (C-10), 44.1 (C-1"), 34.6 (C-1'), 30.3 (C-2"), 20.1 (C-3"), 14.0 (C-4"); HRMS (EI), m/z
Calcd for C19H20N2OS (M)•+ 324.1296, found 324.1306.
2-(Benzylthio)-3-butylbenzo[g]quinazolin-4(3H)-one (9): white amorphous powder (82%); mp 138–140
°C (DMF); 1H NMR (500 MHz, DMSO-d6): δ 8.79 (s, 1H, H-5), 8.19 (br d, J = 8 Hz, 1H, H-6), 8.17 (s, 1H,
H-10), 8.09 (br d, J = 8 Hz, 1H, H-9), 7.66 (br t, J = 8 Hz, 1H, H-8), 7.56 (m, 3H, H-7, 2'/6'), 7.36 (t-like, J
= 7.5 Hz, 2H, H-3',5'), 7.28 (br d, J = 7.5 Hz, 1H, H-4'), 4.61 (s, 2H, -CH2-), 4.04 (t, J = 7.5 Hz, 2H, H-1''),
1.67 (m, 2H, H-2''), 1.37 (m, 2H, H-3''), 0.92 (t, J = 7.5 Hz, 3H, H-4''); 13C NMR (125 MHz, DMSO-d6): δ
161.3 (C-4), 155.5 (C-2), 142.6 (C-4b), 137.3 (C-1'), 136.8 (C-9a), 131.0 (C-5a), 129.9 (C-5), 129.8
(C-3',5'), 129.1 (C-6), 129.0 (C-8), 128.4 (C-2',6'), 128.2 (C-4a), 127.9 (C-4'), 126.5 (C-9), 123.3 (C-7),
118.9 (C-10), 44.1 (C-1"), 36.0 (-CH2-), 30.3 (C-2"), 20.1 (C-3"), 14.0 (C-4"); HRMS (EI), m/z Calcd for
C23H22N2OS (M)•+ 374.1453, found 374.1469.
3-Butyl-2-(3-methoxybenzylthio)benzo[g]quinazolin-4(3H)-one (10): white amorphous powder (85%);
mp 116–118 °C (DMF); 1H NMR (500 MHz, DMSO-d6): δ 8.80 (s, 1H, H-5), 8.20 (br d, J = 8.5 Hz, 1H,
H-6), 8.18 (s, 1H, H-10), 8.09 (br d, J = 8.5 Hz, 1H, H-9), 7.66 (br t, J = 7.5 Hz, 1H, H-8), 7.56 (br t, J = 7.5
Hz, 1H, H-7), 7.27 (t-like, J = 8 Hz, 1H, H-5'), 7.16 (br s, 1H, H-2'), 7.13 (br d, J = 8 Hz, 1H, H-4'), 6.85 (br
d, J = 8 Hz, 1H, H-6'), 4.58 (s, 2H, -CH2-), 4.05 (t, J = 7.5 Hz, 2H, H-1''), 3.74 (s, 3H, -OCH3), 1.68 (m, 2H,
H-2''), 1.36 (m, 2H, H-3''), 0.93 (t, J = 7.5 Hz, 3H, H-4''); 13C NMR (125 MHz, DMSO-d6): δ 161.3 (C-4),
159.7 (C-3'), 155.5 (C-2), 142.6 (C-4b), 138.8 (C-1'), 136.8 (C-9a), 131.0 (C-5a), 130.1 (C-5'), 129.8 (C-5),
129.1 (C-6), 128.5 (C-8), 128.1 (C-4a), 126.5 (C-9), 123.3 (C-7), 122.0 (C-6'), 118.9 (C-10), 115.5 (C-4'),
113.4 (C-2'), 55.5 (-OCH3), 44.1 (C-1"), 36.0 (-CH2-), 30.3 (C-2"), 20.1 (C-3"), 14.0 (C-4"); HRMS (EI),
m/z Calcd for C24H24N2O2S (M)•+ 404.1558, found 404.1579.
3-Butyl-2-(4-chlorobenzylthio)benzo[g]quinazolin-4(3H)-one (11): pale yellow amorphous powder
(74%); mp 147–149 °C, (DMF); 1H NMR (500 MHz, DMSO-d6): δ 8.80 (s, 1H, H-5), 8.20 (br d, J = 8 Hz,
1H, H-6), 8.18 (s, 1H, H-10), 8.10 (br d, J = 8 Hz, 1H, H-9), 7.65 (br t, J = 7.5 Hz, 1H, H-8), 7.60 (d, J = 8.5
Hz, 2H, H-3'/5'), 7.57 (br t, J = 7.5 Hz, 1H, H-7), 7.41 (d, J = 8.5 Hz, 2H, H-2'/6'), 4.61 (s, 2H, -CH2-), 4.05
(t, J = 7.5 Hz, 2H, H-1''), 1.67 (m, 2H, H-2''), 1.38 (m, 2H, H-3''), 0.93 (t, J = 7.5 Hz, 3H, H-4''); 13C NMR
(125 MHz, DMSO-d6): δ 161.3 (C-4), 155.3 (C-2), 142.7 (C-4b), 136.8 (C-4'), 136.7 (C-9a), 132.5 (C-1'),
131.7 (C- 3'/5'), 131.1 (C-5a), 131.0 (C-5'), 129.8 (C-5), 129.1 (C-2'/6'), 128.9 (C-6), 128.5 (C-8), 128.1
(C-4a), 126.5 (C-9), 123.3 (C-7), 118.9 (C-10), 44.1 (C-1"), 35.1 (-CH2-), 30.3 (C-2"), 20.1 (C-3"), 14.0
(C-4"); HRMS (EI), m/z Calcd for C23H21ClN2OS (M)•+ 408.1063, found 408.1089.
4-[(3-Butyl-3,4-dihydro-4-oxobenzo[g]quinazolin-2-ylthio)methyl]benzonitrile
(12):
white
amorphous powder (87%); mp 178–180 °C (DMF); 1H NMR (500 MHz, DMSO-d6): δ 8.79 (s, 1H, H-5),

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8.20 (br d, J = 7.5 Hz, 1H, H-6), 8.18 (s, 1H, H-10), 8.10 (br d, J = 7.5 Hz, 1H, H-9), 7.83 (d, J = 8.5 Hz,
2H, H-3'/5'), 7.79 (d, J = 8.5 Hz, 2H, H-2'/6'), 7.67 (br t, J = 7.5 Hz, 1H, H-8), 7.57 (br t, J = 7.5 Hz, 1H,
H-7), 4.69 (s, 2H, -CH2-), 4.05 (t, J = 7.5 Hz, 2H, H-1''), 1.68 (m, 2H, H-2''), 1.37 (m, 2H, H-3''), 0.93 (t,
J = 7.5 Hz, 3H, H-4''); 13C NMR (125 MHz, DMSO-d6): δ 161.7 (C-4), 155.5 (C-2), 143.9 (C-4b), 141.5
(C-1'), 136.8 (C-9a), 132.8 (C-3'/5'), 131.1 (C-5a), 130.8 (C-2'/6'), 129.8 (C-5), 128.9 (C-6), 128.5 (C-8),
128.1 (C-4a), 126.5 (C-9), 123.3 (C-7), 119.0 (C≡N), 118.9 (C-10), 110.9 (C-4'), 44.1 (C-1"), 35.3
(-CH2-), 30.3 (C-2"), 20.1 (C-3"), 14.0 (C-4"); HRMS (EI), m/z Calcd for C24H21N3OS (M)•+ 399.1405,
found 399.1434.
3-Butyl-2-[2-(piperidin-1-yl)ethylthio]benzo[g]quinazolin-4(3H)-one (13): pale brown amorphous
powder (86%); mp120–122 °C (DMF); 1H NMR (500 MHz, DMSO-d6): δ 8.79 (s, 1H, H-5), 8.19 (br d, J =
7.5 Hz, 1H, H-6), 8.09 (br s, 2H, H-9, 10), 7.64 (br t, J = 7.5 Hz, 1H, H-8), 7.55 (br t, J = 7.5 Hz, 1H, H-7),
4.08 (t, J = 7.5 Hz, 2H, H-1''), 3.45 (t, J = 7.5 Hz, 2H, CH2-7'), 2.68 (t, J = 7.5 Hz, 2H, CH2-8'), 2.47 (m, 4H,
H-2'/6'), 1.71 (m, 2H, H-2''), 1.40 (m, 4H, H-3'/5'), 1.39 (m, 4H, H-4', 3''), 0.95 (t, J = 7.5 Hz, 3H, H-4''); 13C
NMR (125 MHz, DMSO-d6): δ 161.4 (C-4), 155.3 (C-2), 143.3 (C-4b), 136.7 (C-9a), 130.9 (C-5a), 129.9
(C-5), 128.8 (C-6), 128.6 (C-8), 128.1 (C-4a), 126.5 (C-9), 123.3 (C-7), 118.8 (C-10), 54.3 (C-2'/6'), 54.2
(CH2-7'), 44.1 (C-1"), 30.3 (C-2"), 30.2 (CH2-8'), 26.1 (C-3'/5'), 24.5 (C-4'), 20.1 (C-3"), 14.0 (C-4");
HRMS (EI), m/z Calcd for C23H29N3OS (M)•+ 395.2031, found 395.2049.
3-Butyl-2-(2-morpholinoethylthio)benzo[g]quinazolin-4(3H)-one (14): pale yellow amorphous powder
(88%); mp 125–127 °C (DMF); 1H NMR (500 MHz, DMSO-d6): δ 8.79 (s, 1H, H-5), 8.18 (br d, J = 8 Hz,
1H, H-6), 8.09 (br d, J = 8 Hz, 1H, H-9), 8.07 (s, 1H, H-10), 7.65 (br t, J = 7.5 Hz, 1H, H-8), 7.55 (br t, J =
7.5 Hz, 1H, H-7), 4.07 (t, J = 7.5 Hz, 2H, H-1''), 3.60 (t, J = 4.0 Hz, 4H, H-3'/5'), 3.46 (t, J = 7.5 Hz, 2H,
CH2-7'), 2.72 (t, J = 7.5 Hz, 2H, CH2-8'), 2.50 (t, J = 4.0 Hz, 4H, H-2'/6'), 1.70 (m, 2H, H-2''), 1.39 (m, 2H,
H-3"), 0.95 (t, J = 7.5 Hz, 3H, H-4''); 13C NMR (125 MHz, DMSO-d6): δ 161.3 (C-4), 155.9 (C-2), 142.7
(C-4b), 136.8 (C-9a), 130.9 (C-5a), 129.8 (C-5), 129.0 (C-6), 128.4 (C-8), 128.1 (C-4a), 126.4 (C-9), 123.1
(C-7), 118.9 (C-10), 66.7 (C-3'/5'), 57.4 (CH2-7'), 53.6 (C-2'/6'), 44.0 (C-1"), 30.3 (C-2"), 29.1 (CH2-8'),
20.1 (C-3"), 14.1 (C-4"); HRMS (EI), m/z Calcd for C22H27N3O2S (M)•+ 397.1824, found 397.1852.
2-[3-(3-Butyl-3,4-dihydro-4-oxobenzo[g]quinazolin-2-ylthio)propyl]isoindoline-1,3-dione
(15):
white amorphous powder (90%); mp 210–212 °C (DMF); 1H NMR (500 MHz, DMSO-d6): δ 8.77 (s, 1H,
H-5), 8.17 (br d, J = 7.5 Hz, 1H, H-6), 7.88 (m, 5H, H-9, 5'/6', 4'/7'), 7.73 (s, 1H, H-10), 7.65 (br t, J = 7.5
Hz, 1H, H-8), 7.56 (br t, J = 7.5 Hz, 1H, H-7), 4.03 (t, J = 7.5 Hz, 2H, H-1''), 3.79 (t, J = 7 Hz, 2H,
CH2-7'), 3.36 (t, J = 7 Hz, 2H, CH2-9'), 2.14 (quint, J = 7.2 Hz, 2H, CH2-8'), 1.67 (m, 2H, H-2''), 1.37 (m,
2H, H-3"), 0.93 (t, J = 7.5 Hz, 3H, H-4''); 13C NMR (125 MHz, DMSO-d6): δ 168.5 (C-1'/3'), 161.5 (C-4),
155.6 (C-2), 142.9 (C-4b), 136.8 (C-9a), 134.9 (C-3a'/7a'), 132.1 (C-5'/6'), 131.0 (C-5a), 129.9 (C-5),
129.2 (C-6), 128.5 (C-8), 128.1 (C-4a), 126.5 (C-9), 123.5 (C-4'/7'), 123.0 (C-7), 118.8 (C-10), 44.1
(C-1"), 41.4 (CH2-7'), 36.5 (CH2-9'), 30.3 (C-2"), 29.2 (CH2-8'), 20.1 (C-3"), 14.1 (C-4"); HRMS (EI),

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m/z Calcd for C27H25N3O3S (M)•+ 471.1617, found 471.1635.
3-Allyl-2-(ethylthio)benzo[g]quinazolin-4(3H)-one (16): pale yellow amorphous powder (88%); mp
98–100 °C (DMF); 1H NMR (500 MHz, DMSO-d6): δ 8.81 (s, 1H, H-5), 8.19 (br d, J = 8.5 Hz, 1H, H-6),
8.12 (s, 1H, H-10), 8.09 (br d, J = 8.5 Hz, 1H, H-9), 7.64 (br t, J = 8 Hz, 1H, H-8), 7.56 (br t, J = 8 Hz,
1H, H-7), 5.97 (m, 1H, H-2"), 5.22 (dd, J = 10.5, 1.5 Hz, 1H, H-3a"), 5.15 (dd, J = 17.5, 1.5 Hz, 1H,
13
H-3b"), 4.73 (d, J = 4 Hz, 2H, H-1"), 3.31 (q, J = 7.5 Hz, 2H, H-1'), 1.41 (t, J = 7.5 Hz, 3H, H-2'); C
NMR (125 MHz, DMSO-d6): δ 161.2 (C-4), 156.0 (C-2), 142.8 (C-4b), 136.9 (C-9a), 132.3 (C-2"), 131.0
(C-5a), 129.8 (C-5), 129.1 (C-6), 128.5 (C-8), 128.1 (C-4a), 126.4 (C-9), 123.3 (C-7), 118.9 (C-10), 117.7
(C-3"), 46.1 (C-1"), 26.5 (C-1'), 14.5 (C-2'); HRMS (EI), m/z Calcd for C17H16N2OS (M)•+ 296.0983,
found 296.1011.
3-Allyl-2-(allylthio)benzo[g]quinazolin-4(3H)-one (17): pale yellow amorphous powder (79%); mp
1
120–122 °C (DMF); H NMR (500 MHz, DMSO-d6): δ 8.80 (s, 1H, H-5), 8.18 (br d, J = 8.5 Hz, 1H,
H-6), 8.12 (s, 1H, H-10), 8.08 (br d, J = 8.5 Hz, 1H, H-9), 7.66 (br t, J = 8 Hz, 1H, H-8), 7.56 (br t, J = 8
Hz, 1H, H-7), 6.03 (m, 1H, H-2'), 5.95 (m, 1H, H-2"), 5.45 (dd, J = 17.5, 1.5 Hz, 1H, H-3a'), 5.22 (dd, J =
10.5, 1.5 Hz, 1H, H-3b'), 5.19 (dd, J = 10.5, 1.5 Hz, 1H, H-3b"), 5.15 (dd, J = 17.5, 1.5 Hz, 1H, H-3a"),
4.72 (d, J = 4 Hz, 2H, H-1"), 4.00 (d, J = 7 Hz, 2H, H-1'); 13C NMR (125 MHz, DMSO-d6): δ 161.2 (C-4),
155.4 (C-2), 142.6 (C-4b), 136.9 (C-9a), 133.4 (C-2'), 132.3 (C-2"), 131.0 (C-5a), 129.8 (C-5), 129.1
(C-6), 128.5 (C-8), 128.1 (C-4a), 126.5 (C-9), 123.4 (C-7), 119.5 (C-3'), 118.9 (C-10), 117.7 (C-3"), 46.1
(C-1"), 34.7 (C-1'); HRMS (EI), m/z Calcd for C18H16N2OS (M)•+ 308.0983, found 308.0999.
3-Allyl-2-(3-methoxybenzylthio)benzo[g]quinazolin-4(3H)-one (18): white amorphous powder (81%);
mp 115–117 °C (DMF); 1H NMR (500 MHz, DMSO-d6): δ 8.82 (s, 1H, H-5), 8.21 (s, 1H, H-10), 8.19 (br
d, J = 8.5 Hz, 1H, H-6), 8.11 (br d, J = 8.5 Hz, 1H, H-9), 7.68 (br t, J = 7.5 Hz, 1H, H-8), 7.57 (br t, J =
7.5 Hz, 1H, H-7), 7.26 (t-like, J = 8 Hz, 1H, H-5'), 7.14 (br s, 1H, H-2'), 7.11 (br d, J = 8 Hz, 1H, H-4'),
6.86 (br d, J = 8 Hz, 1H, H-6'), 5.93 (m, 1H, H-2"), 5.20 (dd, J = 10.5, 1.5 Hz, 1H, H-3b"), 5.15 (dd, J =
13
17.5, 1.5 Hz, 1H, H-3a"), 4.72 (d, J = 5 Hz, 2H, H-1"), 4.58 (s, 2H, -CH2-), 3.74 (s, 3H, -OCH3); C
NMR (125 MHz, DMSO-d6): δ 161.2 (C-4), 159.7 (C-3'), 155.7 (C-2), 142.6 (C-4b), 138.7 (C-1'), 136.9
(C-9a), 132.3 (C-2"), 131.0 (C-5a), 130.1 (C-5'), 129.8 (C-5), 129.2 (C-6), 128.6 (C-8), 128.2 (C-4a),
126.5 (C-9), 123.3 (C-7), 122.0 (C-6'), 118.9 (C-10), 117.8 (C-3"), 115.4 (C-4'), 113.4 (C-2'), 55.5
(-OCH3), 46.1 (C-1"), 36.0 (-CH2-); HRMS (EI), m/z Calcd for C23H20N2O2S (M)•+ 388.1245, found
388.12472.
2-(4-Chlorobenzylthio)-3-allylbenzo[g]quinazolin-4(3H)-one (19): white amorphous powder (78%);
mp 219–221 °C (DMF); 1H NMR (500 MHz, DMSO-d6): δ 8.82 (s, 1H, H-5), 8.21 (s, 1H, H-10), 8.18 (br
d, J = 8 Hz, 1H, H-6), 8.09 (br d, J = 8 Hz, 1H, H-9), 7.66 (br t, J = 7.5 Hz, 1H, H-8), 7.59 (d, J = 8.5 Hz,

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2H, H-3'/5'), 7.56 (br t, J = 7.5 Hz, 1H, H-7), 7.40 (d, J = 8.5 Hz, 2H, H-2'/6'), 5.93 (m, 1H, H-2"), 5.21
(dd, J = 10.5, 1.5 Hz, 1H, H-3b"), 5.13 (dd, J = 17.5, 1.5 Hz, 1H, H-3a"), 4.72 (d, J = 4.5 Hz, 2H, H-1"),
13
4.60 (s, 2H, -CH2-); C NMR (125 MHz, DMSO-d6): δ 161.6 (C-4), 155.4 (C-2), 142.5 (C-4b), 136.8
(C-4'), 136.7 (C-9a), 132.4 (C-1'), 132.2 (C-2"), 131.7 (C- 3'/5'), 131.1 (C-5a), 131.0 (C-5'), 129.8 (C-5),
129.2 (C-2'/6'), 128.9 (C-6), 128.6 (C-8), 128.2 (C-4a), 126.5 (C-9), 123.4 (C-7), 118.8 (C-10), 117.8
(C-3"), 46.0 (C-1"), 35.1 (-CH2-); HRMS (EI), m/z Calcd for C22H17ClN2OS (M)•+ 392.0750, found
392.0776.
3-Allyl-2-(2-morpholinoethylthio)benzo[g]quinazolin-4(3H)-one (20): brown amorphous powder
(62%); mp 187–189 °C (DMF); 1H NMR (500 MHz, DMSO-d6): δ 8.79 (s, 1H, H-5), 8.17 (br d, J = 8 Hz,
1H, H-6), 8.12 (br d, J = 8 Hz, 1H, H-9), 7.99 (s, 1H, H-10), 7.64 (br t, J = 7.5 Hz, 1H, H-8), 7.51 (br t, J
= 7.5 Hz, 1H, H-7), 5.95 (m, 1H, H-2"), 5.20 (dd, J = 10, 1.5 Hz, 1H, H-3b"), 5.14 (dd, J = 17.5, 1.5 Hz,
1H, H-3a"), 4.72 (d, J = 4 Hz, 2H, H-1"), 3.59 (t, J = 4.0 Hz, 4H, H-3'/5'), 3.44 (t, J = 7.5 Hz, 2H, CH2-7'),
13
2.71 (t, J = 7.5 Hz, 2H, CH2-8'), 2.50 (t, J = 4.0 Hz, 4H, H-2'/6'); C NMR (125 MHz, DMSO-d6): δ
161.2 (C-4), 156.1 (C-2), 142.7 (C-4b), 136.8 (C-9a), 132.3 (C-2"), 130.9 (C-5a), 129.9 (C-5), 129.1
(C-6), 128.5 (C-8), 128.1 (C-4a), 126.5 (C-9), 123.2 (C-7), 118.8 (C-10), 117.7 (C-3"), 66.7 (C-3'/5'),
57.3 (CH2-7'), 53.5 (C-2'/6'), 34.7 (C-1"), 29.2 (CH2-8'); HRMS (EI), m/z Calcd for C21H23N3O2S (M)•+
381.1511, found 381.1535.
2-[3-(3-Allyl-3,4-dihydro-4-oxobenzo[g]quinazolin-2-ylthio)propyl]isoindoline-1,3-dione (21): pale
yellow amorphous powder (71%); mp 140–142 °C (DMF); 1H NMR (500 MHz, DMSO-d6): δ 8.75 (s, 1H,
H-5), 8.16 (br d, J = 7.5 Hz, 1H, H-6), 7.86 (m, H-9, 5H, 4'-7'), 7.69 (s, 1H, H-10), 7.64 (br t, J = 7.5 Hz,
1H, H-8), 7.53 (br t, J = 7.5 Hz, 1H, H-7), 5.91 (m, 1H, H-2"), 5.18 (dd, J = 10, 1.5 Hz, 1H, H-3b"), 5.11
(dd, J = 17.5, 1.5 Hz, 1H, H-3a"), 4.68 (d, J = 4 Hz, 2H, H-1"), 3.78 (t, J = 7 Hz, 2H, CH2-7'), 3.32 (t, J =
7 Hz, 2H, CH2-9'), 2.11 (quint, J = 7.2 Hz, 2H, CH2-8'); 13C NMR (125 MHz, DMSO-d6): δ 168.6
(C-1'/3'), 161.6 (C-4), 155.4 (C-2), 143.0 (C-4b), 136.9 (C-9a), 134.8 (C-3a'/7a'), 132.2 (C-2"), 132.1
(C-5'/6'), 131.1 (C-5a), 129.8 (C-5), 129.1 (C-6), 128.4 (C-8), 128.1 (C-4a), 126.5 (C-9), 123.5 (C-4'/7'),
123.1 (C-7), 118.8 (C-10), 117.9 (C-3"), 46.1 (C-1"), 41.4 (CH2-7'), 36.5 (CH2-9'), 29.2 (CH2-8');
HRMS (EI), m/z Calcd for C26H21N3O3S (M)•+ 455.1304, found 455.1334
2-(Ethylthio)-3-phenylbenzo[g]quinazolin-4(3H)-one (22):17 white amorphous powder (72%); mp
1
167–169 °C (DMF); H NMR (500 MHz, DMSO-d6): δ 8.81 (s, 1H, H-5), 8.21 (br d, J = 8.5 Hz, 1H,
H-6), 8.17 (s, 1H, H-10), 8.11 (br d, J = 8.5 Hz, 1H, H-9), 7.67 (br t, J = 8 Hz, 1H, H-8), 7.58 (m, 4H,
13
H-7, 4", 2''/6''), 7.49 (m, 2H, H-3"/5"), 3.17 (q, J = 7.5 Hz, 2H, H-1'), 1.32 (t, J = 7.5 Hz, 3H, H-2'); C
NMR (125 MHz, DMSO-d6): δ 161.5 (C-4), 156.7 (C-2), 143.2 (C-4b), 136.9 (C-9a), 136.5 (C-1"), 130.9
(C-5a), 130.2 (C-5), 129.9 (C-3"/5"), 129.8 (C-4"), 129.5 (C-2"/6"), 129.1 (C-6), 128.6 (C-8), 128.2

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(C-4a), 126.5 (C-9), 123.4 (C-7), 119.6 (C-10), 26.8 (C-1'), 14.3 (C-2'); HRMS (EI), m/z Calcd for
C20H16N2OS (M)•+ 332.0983, found 332.0998.
2-(Allylthio)-3-phenylbenzo[g]quinazolin-4(3H)-one (23): pale yellow amorphous powder (77%); mp
1
145–147 °C (DMF); H NMR (500 MHz, DMSO-d6): δ 8.81 (s, 1H, H-5), 8.22 (br d, J = 8.5 Hz, 1H,
H-6), 8.20 (s, 1H, H-10), 8.12 (br d, J = 8.5 Hz, 1H, H-9), 7.68 (br t, J = 8 Hz, 1H, H-8), 7.58 (m, 4H,
H-7, 4", 2"/6"), 7.50 (m, 2H, H-3"/5"), 5.99 (m, 1H, H-2'), 5.37 (dd, J = 17.5, 1.5 Hz, 1H, H-3a'), 5.15
(dd, J = 10.5, 1.5 Hz, 1H, H-3b'), 3.88 (d, J = 7 Hz, 2H, H-1'); 13C NMR (125 MHz, DMSO-d6): δ 161.5
(C-4), 156.1 (C-2), 143.1 (C-4b), 136.9 (C-9a), 136.4 (C-1"), 133.5 (C-2'), 131.0 (C-5a), 130.3 (C-5),
130.2 (C-3"/5"), 129.9 (C-4"), 129.8 (C-2"/6"), 129.2 (C-6), 128.7 (C-8), 128.2 (C-4a), 126.5 (C-9), 123.5
(C-7), 119.6 (C-10), 119.3 (C-3'), 35.1 (C-1'); HRMS (EI), m/z Calcd for C21H16N2OS (M) •+ 344.0983,
found 344.0999.
3-[(3,4-Dihydro-4-oxo-3-phenylbenzo[g]quinazolin-2-ylthio)methyl]benzonitrile (24): pale yellow
amorphous powder (84%); mp 193–195 °C (DMF); 1H NMR (500 MHz, DMSO-d6): δ 8.83 (s, 1H, H-5),
8.27 (s, 1H, H-10), 8.23 (br d, J = 8.5 Hz, 1H, H-6), 8.14 (br d, J = 8.5 Hz, 1H, H-9), 7.99. (br s, 1H,
H-2'), 7.87 (br d, J = 8 Hz, 1H, H-6'), 7.71 (br d, J = 8 Hz, 1H, H-4'), 7.69 (br t, J = 8 Hz, 1H, H-8), 7.58
13
(br t, J = 8 Hz, 1H, H-7), 7.55 (m, 3H, 4", 2"/6"), 7.52 (m, 3H, 5', 3"/5"), 4.51 (s, 2H, -CH2-); C NMR
(125 MHz, DMSO-d6): δ 161.5 (C-4), 156.0 (C-2), 142.9 (C-4b), 139.8 (C-1'), 136.9 (C-9a), 136.3 (C-1"),
134.8 (C-6'), 133.4 (C-2'), 131.5 (C-4'), 131.0 (C-5a), 130.4 (C-5), 130.2 (C-3"/5"), 130.1 (C-5'), 129.9
(C-4"), 129.8 (C-2"/6"), 129.3 (C-6), 128.7 (C-8), 128.2 (C-4a), 126.6 (C-9), 123.4 (C-7), 119.7 (C-10),
119.1 (C≡N), 111.7 (C-3'), 35.3 (-CH2-); HRMS (EI), m/z Calcd for C26H17N3OS (M)•+ 419.1092, found
419.1119.
2-(4-Chlorobenzylthio)-3-phenylbenzo[g]quinazolin-4(3H)-one (25): pale yellow amorphous powder
(81%); mp 195–197 °C (DMF); 1H NMR (500 MHz, DMSO-d6): δ 8.83 (s, 1H, H-5), 8.27 (s, 1H, H-10),
8.22 (br d, J = 8.5 Hz, 1H, H-6), 8.14 (br d, J = 8.5 Hz, 1H, H-9), 7.69 (br t, J = 8 Hz, 1H, H-8), 7.57 (br t,
J = 8 Hz, 1H, H-7), 7.53 (m, 3H, 4", 2"/6"), 7.51 (d, J = 8.5 Hz, 2H, H-3'/5'), 7.49 (m, 2H, 3"/5"), 7.37 (d,
J = 8.5 Hz, 2H, H-2'/6'), 4.45 (s, 2H, -CH2-); 13C NMR (125 MHz, DMSO-d6): δ 161.3 (C-4), 156.1 (C-2),
143.1 (C-4b), 136.9 (C-4'), 136.8 (C-9a), 136.3 (C-1"), 132.3 (C-1'), 131.7 (C- 3'/5'), 131.0 (C-5a), 130.4
(C-5), 130.3 (C-3"/5"), 130.2 (C-4"), 129.9 (C-2"/6"), 129.2 (C-6), 128.8 (C-2'/6'), 128.7 (C-8), 128.2
(C-4a), 126.6 (C-9), 123.5 (C-7), 119.8 (C-10), 35.5 (-CH2-); HRMS (EI), m/z Calcd for C25H17ClN2OS
(M)•+ 428.0750, found 428.0769.
3-Phenyl-2-[2-(piperidin-1-yl)ethylthio]benzo[g]quinazolin-4(3H)-one (26): pale green amorphous
powder (80%); mp 147–149 °C (DMF); 1H NMR (500 MHz, DMSO-d6): δ 8.81 (s, 1H, H-5), 8.21 (br d, J
= 8.5 Hz, 1H, H-6), 8.15 (s, 1H, H-10), 8.13 (br d, J = 8.5 Hz, 1H, H-9), 7.68 (br t, J = 7.5 Hz, 1H, H-8), 7.58

HETEROCYCLES, Vol. 91, No. 9, 2015
1749
(m, 4H, H-7, 4", 2"/6"), 7.49 (m, 2H, 3"/5"), 3.31 (t, J = 7 Hz, 2H, CH2-7'), 2.69 (t, J = 7 Hz, 2H, CH2-8'),
2.42 (m, 4H, H-2'/6'), 1.48 (m, 4H, H-3'/5'), 1.39 (m, 2H, H-4'); 13C NMR (125 MHz, DMSO-d6): δ 161.5
(C-4), 156.9 (C-2), 143.2 (C-4b), 136.9 (C-9a), 136.6 (C-1"), 130.9 (C-5a), 130.3 (C-3"/5"), 130.2 (C-4"),
129.9 (C-2"/6"), 129.3 (C-5), 129.0 (C-6), 128.6 (C-8), 128.2 (C-4a), 126.5 (C-9), 123.3 (C-7), 119.6
(C-10), 57.6 (CH2-7'), 54.3 (C-2'/6'), 29.9 (CH2-8'), 26.0 (C-3'/5'), 24.5 (C-4'); HRMS (EI), m/z Calcd for
C25H25N3OS (M)•+ 415.1718, found 415.1738.
2-(2-Morpholinoethylthio)-3-phenylbenzo[g]quinazolin-4(3H)-one (27): brown amorphous powder
(72%); mp 172–174 °C (DMF); 1H NMR (500 MHz, DMSO-d6): δ 8.81 (s, 1H, H-5), 8.20 (br d, J = 8 Hz,
1H, H-6), 8.15 (s, 1H, H-10), 8.12 (br d, , J = 8 Hz, 1H H-9), 7.67 (br t, J = 8 Hz, 1H, H-8), 7.58 (m, 4H,
H-7, 4", 2"/6"), 7.49 (m, 2H, 3"/5"), 3.57 (t, J = 4.0 Hz, 4H, H-3'/5'), 3.32 (t, J = 7 Hz, 2H, CH2-7'), 2.63 (t,
J = 7 Hz, 2H, CH2-8'), 2.46 (t, J = 4.0 Hz, 4H, H-2'/6'); 13C NMR (125 MHz, DMSO-d6): δ 161.5 (C-4),
156.7 (C-2), 143.1 (C-4b), 136.9 (C-9a), 136.5 (C-1"), 130.9 (C-5a), 130.6 (C-3"/5"), 130.4 (C-4"), 130.0
(C-2"/6"), 129.8 (C-5), 129.4 (C-6), 128.4 (C-8), 128.1 (C-4a), 126.5 (C-9), 123.3 (C-7), 119.6 (C-10), 66.6
(C-3'/5'), 57.4 (CH2-7'), 53.5 (C-2'/6'), 29.4 (CH2-8'); HRMS (EI), m/z Calcd for C24H23N3O2S (M)•+
417.1511, found 417.1525.
2-[3-(3,4-Dihydro-4-oxo-3-phenylbenzo[g]quinazolin-2-ylthio)propyl]isoindoline-1,3-dione
(28):
1
pale yellow amorphous powder (69%); mp 168–170 °C (DMF); H NMR (500 MHz, DMSO-d6): δ 8.78
(s, 1H, H-5), 8.19 (br d, J = 8 Hz, 1H, H-6), 7.92 (br d, J = 8 Hz, 1H, H-9), 7.88 (m, 4H, H-5'/6', 4'/7'),
7.74 (s, 1H, H-10), 7.67 (br t, J = 7.5 Hz, 1H, H-8), 7.55 (m, 4H, H-7, 4", 2"/6"), 7.45 (m, 2H, 3"/5"),
13
3.71 (t, J = 7 Hz, 2H, CH2-7'), 3.20 (t, J = 7 Hz, 2H, CH2-9'), 2.10 (quint, J = 7 Hz, 2H, CH2-8'); C
NMR (125 MHz, DMSO-d6): δ 168.6 (C-1'/3'), 161.6 (C-4), 155.9 (C-2), 142.3 (C-4b), 136.9 (C-9a),
136.6 (C-1"), 134.8 (C-3a'/7a'), 132.4 (C-5'/6'), 130.8 (C-5a), 130.5 (C-3"/5"), 130.3 (C-4"), 129.9
(C-2"/6"), 129.7 (C-5), 129.2 (C-6), 128.5 (C-8), 128.1 (C-4a), 126.4 (C-9), 123.5 (C-4'/7'), 123.1 (C-7),
118.9 (C-10), 41.5 (CH2-7'), 36.3 (CH2-9'), 29.4 (CH2-8'); HRMS (EI), m/z Calcd for C29H21N3O3S (M)•+
491.1304, found 491.1321.
Antitumor activity assay
Human colon (HCT-116), human breast (MCF-7), human hepatocellular (Hep-G2), human prostate
(PC-3) and human lung (A-549) carcinoma cell lines were obtained from the American Type Culture
Collection (ATCC, Rockville, MD). The cells were grown on RPMI-1640 medium supplemented with
10% inactivated fetal calf serum and 50 μg/mL gentamycin. The cells were maintained at 37 ºC in a
humidified atmosphere with 5% CO2 and were subcultured two to three times a week.21
For antitumor assays, the cell lines were suspended in the medium at concentration 5x104 cell/well in
Corning® 96-well tissue culture plates, and were incubated for 24 h. The tested compounds were then
added to the 96-well plates (six replicates) to achieve eight concentrations for each compound. Six

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vehicle controls with media or 0.5% DMSO were run for each 96 well plate as a control. After incubation
for 24 h, the numbers of viable cells were determined using the MTT test. Briefly, the media were
removed from the 96 well plate and replaced with 100 μL of fresh culture RPMI 1640 medium without
phenol red then 10 μL of the 12 mM MTT stock solution (5 mg of MTT in 1 mL of PBS) were added to
each well including the untreated controls. The 96 well plates were then incubated at 37 °C and 5% CO2
for 4 h. An 85 μL aliquot of the media was removed from the wells, and 50 μL of DMSO were added to
each well and mixed thoroughly with the pipette and incubated at 37 °C for 10 min. Thereafter, the
optical density was measured at 590 nm with the microplate reader (SunRise, TECAN, Inc, USA) to
determine the number of viable cells. The percentage of viability was calculated as [1-(ODt/ODc)]x100%
where ODt is the mean optical density of wells treated with the tested sample and ODc is the mean optical
density of untreated cells. The relation between surviving cells and drug concentration was plotted to get
the survival curve of each tumor cell line after treatment with the specified compound. The IC50–values
(the concentration required to cause toxic effects in 50% of intact cells) were estimated from graphic plots
of the dose response curve for each concentration using Graphpad Prism software (San Diego, CA.
USA).21-23
ACKNOWLEDGEMENTS
The authors extend their appreciation to the Deanship of Scientific Research at King Saud University for
funding this work through research group No. RG-1435-068.
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