Design, synthesis and antiproliferative activity of novel 2-substituted-4-amino-6-halogenquinolines

Article abstract of DOI:10.3390/molecules17055870

Two series of novel 2-substituted-4-amino-6-halogenquinolines 8a-l and 13a-h were designed, synthesized and evaluated for their antiproliferative activity against H-460, HT-29, HepG2 and SGC-7901 cancer cell lines in vitro. The pharmacological results indicated that most compounds with 2-arylvinyl substituents exhibited good to excellent antiproliferative activity. Among them, compound 8e was a considered promising lead for further structural modifications with IC50 values of 0.03 μM, 0.55 μM, 0.33 μM and 1.24 μM, which was 2.5- to 186-fold more active than gefitinib and compound 1.

Full text of DOI:10.3390/molecules17055870

Molecules 2012, 17, 5870-5881; doi:10.3390/molecules17055870
OPEN ACCESS
molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
Design, Synthesis and Antiproliferative Activity of Novel
2-Substituted-4-amino-6-halogenquinolines
Nan Jiang, Xin Zhai, Ting Li, Difa Liu, Tingting Zhang, Bin Wang and Ping Gong *
Key Lab of New Drugs Design and Discovery of Liaoning Province,
School of Pharmaceutical Engineering, Shenyang Pharmaceutical University,
103 Wenhua Road, Shenhe District, Shenyang 110016, China
* Author to whom correspondence should be addressed; E-Mail: gongpinggp@126.com;
Tel./Fax: +86-24-2398-6429.
Received: 28 April 2012; in revised form: 10 May 2012 / Accepted: 11 May 2012 /
Published: 16 May 2012
Abstract: Two series of novel 2-substituted-4-amino-6-halogenquinolines 8a–l and 13a–h
were designed, synthesized and evaluated for their antiproliferative activity against H-460,
HT-29, HepG2 and SGC-7901 cancer cell lines in vitro. The pharmacological results
indicated that most compounds with 2-arylvinyl substituents exhibited good to excellent
antiproliferative activity. Among them, compound 8e was a considered promising lead for
further structural modifications with IC50 values of 0.03 μM, 0.55 μM, 0.33 μM and
1.24 μM, which was 2.5- to 186-fold more active than gefitinib and compound 1.
Keywords: 2-substituted-4-amino-6-halogenquinolines; design; synthesis; antiproliferative
activity
1. Introduction
Since a series of targeted antitumor agents such as gefitinib and pelitinib were approved for cancer
therapy, the 4-aminoquinazoline and 4-aminoquinoline skeletons are considered to be promising
nucleus for antitumor drug development [1]. As a result, a great number of novel 4-aminoquinazoline
and 4-aminoquinoline derivatives have been developed in succession (Figure 1). Chloroquine (CQ),
the worldwide used immunostimulatory agent with 4-aminoquinoline skeleton, has recently aroused
increasing attention owing to its surprising antiproliferative potency on different cancer cells [2–5].
Similarly, Strekowski et al. developed a short series of 2-alkyl-4-aminoquinoline CQ derivatives

Molecules 2012, 17
5871
(e.g., 1 and 2) as immunostimulatory agents [6,7]. Among them, compound 1 with a 2-aryl group was
also reported for its excellent antiangiogenesis activity in the chick embryo chorioallantoic membrane
(CAM) assay [8], which brought us new hope in the study of antitumor agents. Under the inspiration
of CQ and compound 1, we conjectured that analogue 2 with a 2-styryl group should possess
promising antiproliferative effects as well.
Figure 1. Structures of gefitinib, pelitinib, CQ, CQ derivatives and target compounds 8a–l, 13a–h.
Prompted by this conjecture, we have designed two series of novel 2-substituted-4-amino-6-halogen
quinolines. In our efforts to provide derivatives endowed with improved electron affinity and better
biological interactions, substituents of various arylvinyl and alkylamino functional groups were
introduced into the C-2 and C-4 positions, respectively, to generate compounds 8a–l, which were
prepared via an optimized Knoevenagel reaction condition. Meanwhile, the introduction of halogen at
the C-6 position might adjust lipophilicity. In order to examine the effect of the pattern of the spacer
between nucleus and aryl moiety on their activity, target compounds 13a–h were synthesized through
a methylsulfone or dimethylsulfone linkage. All target compounds were evaluated for their
antiproliferative activity in vitro against four typical cancer cell lines (H-460, HT-29, HepG2 and
SGC-7901 cell lines) and a preliminary SAR study of these compounds is discussed.
2. Results and Discussion
2.1. Chemistry
The synthetic routes of target compounds 8a–l and 13a–h are illustrated in Scheme 1. The
commercially available ethyl acetoacetate was condensed with 4-substituted anilines in the presence of
ammonium ceric nitrate at 40 °C leading to the formation of 4a–b [9]. Treatment of 4a–b in diphenyl
ether at 250 °C for 20 min yielded compounds 5a–b, which were then chlorinated with phosphoryl
chloride to afford 4-chloro-2-methylquinolines 6a–b in 97–98% yields [10,11]. Subsequent alkylation
of 6a–b with an excess of the corresponding aliphatic amines at reflux gave rise to the key
intermediates 7a–f [12].

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Scheme 1. Synthesis of target compounds.
Reagents and conditions: (a) Ethyl acetoacetate, Ce(NH4)2(NO3)6, 40 °C, 20–24 h; (b) Ph2O,
250 °C, 20 min; (c) POCl3, 80 °C, 1.5 h; (d) NH2(CH2)nNR2R3, reflux, 6–10 h; (e) ArCHO, ZnCl2,
DMF, reflux, 0.5–1 h; (f) m-CPBA, CH2Cl2, 50 °C, 3 h; (g) TsCl, PhMe, 80 °C, 3 h;
(h) ArSH/ArCH2SH, K2CO3, CH3CN, 50 °C, 2 h; (i) 30% H2O2, Na2WO4·2H2O, HOAc, 30 °C, 6 h;
(j) NH2(CH2)nNR1R2, reflux, 2–5 h.
According to the literature, 2-arylvinylquinolines can be prepared via Knoevenagel reaction of
2-methylquinolines and aryl aldehydes, using acetic acid as a solvent at 100 °C for 24 h [13], or with
fused zinc chloride as catalyst for 2 h [14,15]. However, both methods failed due to the number of side
reactions or the black viscous state of the reaction systems. After repeated experiments, an efficient
modified condition for preparing 2-arylvinylquinolines 8a–l in 74–92% yields, using zinc chloride as
catalyst in refluxing N,N-dimethylformamide (DMF) for 0.5–1 h, was successfully employed.
It’s worth mentioning that this optimized method for the preparation of 2-arylvinylquinolines
predominantly generates the (E)-isomer from simple building blocks. Coupling constants (J = 15–17 Hz)
from the proton nuclear magnetic resonance (1H-NMR) spectra of target compounds clearly indicated
that derivatives 8a–l were both geometrically pure and were exclusively trans (E) isomers.
The oxidation reaction of 4-chloro-6-fluoro-2-methylquinoline (6b) with 3-chloroperbenzoic acid
provided compound 9 [16], which was chlorinated with benzenesulfonyl chloride to afford 4-chloro-2-
(chloromethyl)-6-fluoroquinoline (10) [17]. The reaction of 10 with substituted thiophenols or
benzylthiols was carried out in the presence of potassium carbonate at 50 °C to give compounds 11a–d,
which were converted into compounds 12a–d after treatment with 30% hydrogen peroxide and sodium
tungstate in acetic acid [18]. Finally, target compounds 13a–h were obtained according to the same
method as described for compounds 7a–f.

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5873
2.2. Biological Results and Discussion
The antiproliferative activity of two series of target compounds 8a–l and 13a–h was evaluated with
non-small-cell lung cancer cell line (H-460), human colon cancer cell line (HT-29), human liver cancer
cell line (HepG2) and stomach cancer cell line (SGC-7901) by the MTT assay in vitro, with compound
1 and gefitinib as the positive controls. The results expressed as IC50 values are summarized in
Tables 1 and 2.
Table 1. The substituents and IC50 values of 8a–l against H-460, HT-29, HepG2 and
SGC-7901 cells in vitro.
IC50 (μmol/L)
Compd.
R1
n
NR2R3
Ar
H-460
HT-29
HepG2
SGC-7901
8a
8b
8c
8d
8e
8f
Cl
Cl
Cl
Cl
Cl
Cl
F
3
3
2
3
2
3
2
3
2
3
1.57
2.04
2.89
3.34
S
S
2.10
0.46
1.58
0.03
1.20
0.51
0.49
0.91
1.97
2.36
0.79
2.35
0.55
1.74
1.03
0.96
1.84
1.68
1.76
0.93
3.03
0.33
1.86
0.66
0.77
1.56
4.88
4.21
1.56
3.30
1.24
1.55
1.33
1.98
1.72
5.60
8g
8h
8i
S
S
F
F
8j
F
8k
8l
F
F
2
3
3.82
2.32
5.27
2.46
4.51
1.78
11.84
4.74
1
3.52
5.59
1.35
3.36
2.06
6.42
4.92
gefitinib
10.26
As shown in Table 1, all compounds except for 8k exhibited good to excellent antiproliferative
activity, with IC50 values ranging from 0.03–4.74 μM, which were 1.1- to 186-fold better than the
positive controls. Among them, compound 8e bearing a 4-methoxystyryl group at the C-2 position and
a 3-(dimethylamino)-1-propylamino substituent at the C-4 position possessed the best antiproliferative
potency (IC50 values of 0.03 μM, 0.55 μM, 0.33 μM and 1.24 μM) and emerged as a lead for further
research on quinoline analogues. Furthermore, almost all the compounds were more potent against
H-460 cells than against other three cells, reflecting good selectivity for lung cancer.
In general, the substituents on the side chain at the C-4 position had a major influence on
pharmacological activity, and variations of the terminal substituents on the side chain would change
the activity dramatically. Generally, a dimethylamino group made a good contribution to the
antiproliferative potency, while introduction of a morpholinyl group resulted in a certain decrease in
activity (8a vs. 8g, 8b vs. 8h, 8e vs. 8f), which might be due to its steric hindrance.

Molecules 2012, 17
Table 2. The substituents and IC50 values of 13a–h against H-460, HT-29 cells in vitro.
5874
IC50 (μmol/L)
IC50 (μmol/L)
H-460 HT-29
Compd.
m
n
NR1R2 Ar
Compd.
13f
m
n
NR1R2 Ar
H-460 HT-29
13a
13b
0
0
2
3
47.3
69.7
1
1
2
3
22.1
9.0
14.3
4.7
NA a
185.2 13g
13c
0
3
160.3 NA a
13h
1
3
156.3 NA a
O
O
13d
13e
1
1
2
3
21.97 53.6
146.9 NA a
1
3.52
5.59
1.35
3.36
gefitinib
a NA: Compounds having IC50 value > 200 μM.
As can be seen from the comparison of Tables 1 and 2, all compounds with 2-arylvinyl substituents
were more active than those with 2-aryl, 2-(arylsulfonyl)methyl and 2-(benzylsulfonyl)methyl substituents.
The results suggested that the introduction of ethylene linkages between nucleus and aryl moiety based
on the structure of compound 1 was essential for improving activity, and a methylsulfone or
dimethylsulfone linkage was not favorable in this region. Further analysis of 2-arylvinyl groups
revealed that compounds substituted with electron donating groups were superior to that with strong
electrophilic groups, and the greatest enhancement of activity occurred with the 4-methoxyphenyl
substituent. A case in point is that 4-methoxysubstiuted compound 8e was the most active compound,
whereas 8k bearing 4-methylsulfonyl substituent showed a 2.5- to 4-fold decrease in potency against
HT-29, HepG2 and SGC-7901 cell lines compared to the positive control 1.
3. Experimental
3.1. Chemistry
Melting points were obtained on a Büchi Melting Point B-540 apparatus (Büchi Labortechnik,
Flawil, Switzerland) and were uncorrected. Mass spectra (MS) were taken in ESI mode on Agilent
1100 LC-MS (Agilent, Palo Alto, CA, USA). Proton (1H) nuclear magnetic resonance spectra were
recorded using Bruker ARX-300 and Bruker ARX-600 spectrometers (Bruker Bioscience, Billerica,
MA, USA) with TMS as an internal standard. Unless otherwise noted, all common reagents and
solvents were used as obtained from commercial suppliers without further purification.
3.2. General Procedure for the Preparation of Ethyl-(3Z)-3-(4-substitutedphenylamino)but-2-enoates
4a–b
Ammonium ceric nitrate (5 mmol) was added to a stirred solution of 4-substituted aniline (0.5 mol)
in ethyl acetoacetate (0.6 mol) at room temperature. Then the mixture was heated to 40 °C for 20–24 h.
After the reaction was completed, ethanol (50 mL) was added and the mixture was stirred for
another 0.5 h. The mixture was cooled to 0 °C, separated by filtration, washed with cool ethanol. The
crude products were purified by recrystallization from ethanol to give compounds 4a–b (68–72%) as

Molecules 2012, 17
5875
white crystals. Compound 4a was prepared from 4-chloroaniline, and compound 4b was prepared
from 4-fluoroaniline.
3.3. General Procedure for the Preparation of 6-Substituted-2-methylquinolin-4-ols 5a–b
Compounds 4 (0.2 mol) was added portionwise to a stirred solution of diphenyl ether (200 mL) at
250 °C within 10 min. The resulting solution was stirred for 20 min and cooled to 40 °C, then a solid
formed. Ether (150 mL) was added, the mixture was stirred for a while and cooled to room
temperature. The precipitate was filtered and washed with ether to afford compounds 5a–b (92–95%)
as gray solids.
3.4. General Procedure for the Preparation of 6-Substituted-4-chloro-2-methylquinolines 6a–b
A mixture of compound 5 (0.1 mol) in phosphorus oxychloride (70 mL) were heated to 80 °C for
1.5 h. Excess phosphorus oxychloride was then removed under reduced pressure. The residue was
poured into ice water (500 mL), stirred intensively for 1 h and filtered in order to remove insoluble
solids. The filtrate was neutralized with aqueous ammonia to a pH of 8–9, filtered and dried to give
compounds 6a–b (97–98%) as gray or light pink solids.
3.5. General Procedure for the Preparation of 6-Substituted-2-methyl-4-aminoquinolines 7a–f
A mixture of compounds 6a–b (50 mmol) and aliphatic amines (0.2 mol) was stirred at reflux for
6–10 h and then cooled to room temperature. Water (200 mL) was added to the solution, and the
product was precipitated and collected, washed several times with water, and dried to afford
compounds 7a–f (95–99%) as pale solids. Compound 7a was prepared from 6a and N,N-dimethyl-
ethylenediamine. Compound 7b was prepared from 6a and N,N-dimethyl-1,3-propanediamine.
Compound 7c was prepared from 6a and N-(3-aminopropyl)morpholine. Compound 7d was prepared
from 6b and N,N-dimethylethylenediamine. Compound 7e was prepared from 6b and N,N-dimethyl-1,3-
propanediamine. Compound 7f was prepared from 6b and N-(3-aminopropyl)morpholine.
3.6. General Procedure for the Preparation of Compounds 8a–l
Anhydrous zinc chloride (0.5 mmol) was added rapidly to a mixture of compound 7 (1 mmol), aryl
aldehyde (1.1 mmol) and DMF (1 mL). The reaction mixture was refluxed for 20–60 min and cooled
to 70 °C, methanol (8 mL) was added and refluxed for 1 h. After cooling, the yellow solid was
precipitated, filtered and washed with methanol. The crude product was purified by recrystallization
from methanol/DMF to afford compounds 8a–l.
(E)-2-(2-(Benzo[d][1,3]dioxol-5-yl)vinyl)-6-chloro-N-(3-morpholin-4ylpropyl)quinolin-4-amine (8a).
Prepared from 7c and heliotropin. Yield: 88%; m.p.: 189–192 °C; MS (ESI) m/z: 452.2, 454.1 [M+H+];
1H-NMR (600 MHz, DMSO-d6) δ (ppm): 8.32 (s, 1H), 7.77 (d, J = 9.0 Hz, 1H), 7.67 (d, J = 16.2 Hz,
1H), 7.59 (d, J = 9.0 Hz, 1H), 7.36 (s, 1H), 7.33 (s, 1H), 7.18 (d, J = 16.2 Hz, 1H), 7.15 (d, J = 7.8 Hz,
1H), 6.96 (d, J = 7.8 Hz, 1H), 6.72 (s, 1H), 6.07 (s, 2H), 3.62 (t, 4H), 3.38 (q, 2H), 2.46 (t, 2H), 2.41
(s, 4H), 1.90–1.85 (qui, 2H).

Molecules 2012, 17
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(E)-6-Chloro-N-(3-morpholinopropyl)-2-(2-(thiophen-2-yl)vinyl)quinolin-4-amine (8b). Prepared from
7c and thiophene-2-carbaldehyde. Yield: 79%; m.p.: 179–183 °C; MS (ESI) m/z: 414.1, 416.0 [M+H+];
1H-NMR (300 MHz, DMSO-d6) δ (ppm): 8.30 (s, 1H), 7.92 (d, J = 15.6 Hz, 1H), 7.75 (d, J = 9.0 Hz,
1H), 7.57 (t, J = 9.0 Hz, 2H), 7.38 (d, J = 2.7 Hz, 1H), 7.29 (t, 1H), 7.12 (t, 1H), 7.00
(d, J = 15.9 Hz, 1H), 6.75 (s, 1H), 3.62 (t, 4H), 3.38(q, 2H), 2.46–2.36 (m, 6H), 1.91–1.80 (qui, 2H).
(E)-N1-(6-Chloro-2-(2-(thiophen-2-yl)vinyl)quinolin-4-yl)-N2,N2-dimethylethane-1,2-diamine (8c). Prepared
from 7a and thiophene-2-carbaldehyde. Yield: 75%; m.p.: 134–136 °C; MS (ESI) m/z: 358.1, 360.1
1
[M+H+]; H-NMR (600 MHz, DMSO-d6) δ (ppm): 8.29 (s, 1H), 7.92 (d, J = 15.0 Hz, 1H), 7.75 (d,
J = 7.8 Hz, 1H), 7.62–7.50 (m, 2H), 7.36 (s, 1H), 7.10 (s, 1H), 7.05 (s, 1H), 7.00 (d, J = 15.0 Hz, 1H),
6.76 (s, 1H), 3.41 (s, 2H), 2.59 (s, 2H), 2.24 (s, 6H).
(E)-N1-(6-Chloro-2-(4-(methylsulfonyl)styryl)quinolin-4-yl)-N3,N3-dimethylpropane-1,3-diamine (8d). Prepared
from 7b and p-methylsulphonyl benzaldehyde. Yield: 87%; m.p.: 176–181 °C; MS (ESI) m/z: 444.3,
1
446.3 [M+H+]; H-NMR (300 MHz, DMSO-d6) δ (ppm): 8.36 (s, 1H), 7.96 (t, 4H), 7.90–7.78 (m,
J = 16.2, 9.3 Hz, 2H), 7.62 (d, J = 9.0 Hz, 1H), 7.53 (d, J = 16.2 Hz, 1H), 7.43 (t, 1H), 6.88 (s, 1H),
3.25 (s, 3H), 3.41 (s, 2H), 2.73 (t, 2H), 2.44 (s, 6H), 2.02–1.91 (qui, 2H).
(E)-N1-(6-Chloro-2-(4-methoxystyryl)quinolin-4-yl)-N2,N2-dimethylethane-1,2-diamine (8e). Prepared
from 7a and p-anisaldehyde. Yield: 83%; m.p.: 169–172 °C; MS (ESI) m/z: 382.1, 384.1 [M+H+];
1H-NMR (300 MHz, DMSO-d6) δ (ppm): 8.33 (d, J = 1.4 Hz, 1H), 7.74 (t, J = 16.2, 9.0 Hz, 2H), 7.65
(d, J = 8.7 Hz, 2H), 7.59 (dd, J = 9.0, 1.4 Hz, 1H), 7.16 (t, J = 16.2 Hz, 2H), 6.99 (d, J = 8.7 Hz, 2H), 6.79
(s, 1H), 3.80 (s, 3H), 3.48 (q, 2H), 2.71 (t, 2H), 2.34 (s, 6H).
(E)-6-Chloro-2-(4-methoxystyryl)-N-(3-morpholin-4ylpropyl)quinolin-4-amine (8f). Prepared from 7c
1
and p-anisaldehyde. Yield: 85%; m.p.: 126–129 °C; MS (ESI) m/z: 438.4, 440.4 [M+H+]; H-NMR
(600 MHz DMSO-d6) δ (ppm): 8.28 (d, J = 1.8 Hz, 1H), 7.75 (d, J = 9.0 Hz, 1H), 7.67 (d, J = 16.2 Hz,
1H), 7.63 (d, J = 8.4 Hz, 2H), 7.56 (dd, J = 9.0, 1.8 Hz, 1H), 7.23 (t, 1H), 7.15 (d, J = 15.6 Hz, 1H),
6.97 (d, J = 8.4 Hz, 2H), 6.72 (s, 1H), 3.79 (s, 3H), 3.60 (s, 4H), 3.38–3.35 (m, 2H), 2.43 (t, 2H), 2.38
(s, 4H), 1.89–1.83 (qui, 2H).
(E)-N1-(2-(2-(Benzo[d][1,3]dioxol-5-yl)vinyl)-6-fluoroquinolin-4-yl)-N2,N2-dimethylethane-1,2-diamine
(8g). Prepared from 7d and heliotropin. Yield: 92%; m.p.: 152–155 °C; MS (ESI) m/z: 380.4, 381.4
[M+H+]; 1H-NMR (300 MHz, DMSO-d6) δ (ppm): 8.04 (dd, J = 10.5 Hz, 1H), 7.83–7.78 (m, 1H),
7.64 (d, J = 16.5 Hz, 1H), 7.49 (t, 1H), 7.37 (s, 1H), 7.16 (t, J = 16.2, 7.2 Hz, 2H), 6.95 (d, J = 8.0 Hz,
2H), 6.73 (s, 1H), 6.07 (s, 2H), 3.42 (q, 2H), 2.59 (t, 2H), 2.25 (s, 6H).
(E)-N1-(6-Fluoro-2-(2-(thiophen-2-yl)vinyl)quinolin-4-yl)-N3,N3-dimethylpropane-1,3-diamine (8h). Prepared
from 7e and thiophene-2-carbaldehyde. Yield: 78%; m.p.: 154–157 °C; MS (ESI) m/z: 356.3, 357.3
1
[M+H+]; H-NMR (300 MHz, DMSO-d6) δ (ppm): 7.99 (dd, J = 11.1, 2.1 Hz, 1H), 7.89 (d,
J = 15.9 Hz, 1H), 7.80 (dd, J = 9.0, 6.0 Hz, 1H), 7.55 (d, J = 5.1 Hz, 1H), 749 (td, J = 9.0, 8.1 Hz, 1H),
7.37 (d, J = 3.3 Hz, 1H), 7.19–7.10 (m, J = 4.2 Hz, 2H), 7.01 (d, J = 15.9 Hz, 1H), 6.74 (s, 1H), 2.37
(t, 2H), 2.18 (s, 6H), 1.89–1.77 (qui, 2H).

Molecules 2012, 17
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(E)-N1-(6-Fluoro-2-(2-(thiophen-2-yl)vinyl)quinolin-4-yl)-N2,N2-dimethylethane-1,2-diamine (8i). Prepared
from 7d and thiophene-2-carbaldehyde. Yield: 82%; m.p.: 148–152 °C; MS (ESI) m/z: 342.1, 343.1
[M+H+]; 1H-NMR (300 MHz, DMSO-d6) δ (ppm): 8.07 (dd, J = 11.7 Hz, 1H), 7.92 (d, J = 15.9 Hz, 1H),
7.81 (dd, J = 9.0, 6.0 Hz, 1H), 7.56 (d, J = 4.8 Hz, 1H), 7.50 (td, J = 9.0, 8.4 Hz, 1H), 7.37
(d, J = 4.5 Hz, 1H), 7.12 (t, J = 4.5, 3.9 Hz, 1H), 7.01 (d, J = 15.9 Hz, 2H), 6.77 (s, 1H), 2.63 (t, 2H),
2.28 (s, 6H).
(E)-N1-(6-Fluoro-2-(4-(methylsulfonyl)styryl)quinolin-4-yl)-N3,N3-dimethylpropane-1,3-diamine (8j).
Prepared from 7e and p-methylsulphonyl benzaldehyde. Yield: 89%; m.p.: 177–180 °C; MS (ESI) m/z:
428.1, 429.1 [M+H+]; 1H-NMR (300 MHz, DMSO-d6) δ (ppm): 8.05 (dd, J = 10.7 Hz, 1H), 8.00–7.92
(m, J = 8.7 Hz, 4H), 7.88–7.77 (m, J = 16.2, 9.0, 6.0 Hz, 2H), 7.59–7.48 (m, J = 15.9, 9.0 Hz, 2H),
7.26 (t, 1H), 6.82 (s, 1H), 3.40 (q, 2H), 3.25 (s, 3H), 2.38 (t, 2H), 2.19 (s, 6H), 1.91–1.79 (qui, 2H).
(E)-N1-(6-Fluoro-2-(4-(methylsulfonyl)styryl)quinolin-4-yl)-N2,N2-dimethylethane-1,2-diamine (8k). Prepared
from 7d and p-methylsulphonyl benzaldehyde. Yield: 86%; m.p.: 178–182 °C; MS (ESI) m/z: 414.2,
1
416.2 [M+H+]; H-NMR (600 MHz, DMSO-d6) δ (ppm): 8.08 (dd, J = 10.8 Hz, 1H), 7.96 (q,
J = 8.4 Hz, 4H), 7.85 (dd, J = 9.6, 6.0 Hz, 1H), 7.82 (d, J = 16.2 Hz, 1H), 7.53 (d, J = 15.6 Hz, 2H),
7.07 (t, 1H), 6.85 (s, 1H), 3.47–3.44 (q, 2H), 3.25 (s, 3H), 2.63 (t, 2H), 2.27 (s, 6H).
(E)-6-Fluoro-2-(4-methoxystyryl)-N-(3-morpholin-4ylpropyl)quinolin-4-amine (8l). Prepared from 7f
1
and p-anisaldehyde. Yield: 82%; m.p.: 148–151 °C; MS (ESI) m/z: 422.2, 423.2 [M+H+]; H-NMR
(300 MHz, DMSO-d6) δ (ppm): 8.01 (dd, J = 11.1 Hz, 1H), 7.81 (dd, J = 9.3, 5.7 Hz, 1H), 7.70–7.61 (m,
J = 16.5, 8.4 Hz, 3H), 7.49 (td, J = 9.0, 8.4 Hz, 1H), 7.16 (d, J = 16.2 Hz, 1H), 7.07 (t, 1H), 6.99 (d,
J = 8.7 Hz, 2H), 6.73 (s, 1H), 3.80 (s, 3H), 3.65–3.59 (t, 4H), 3.43–3.37 (q, 2H),
2.47–2.36 (m, 6H), 1.93–1.81 (qui, 2H).
3.7. 4-Chloro-6-fluoro-2-methylquinoline 1-oxide (9)
3-Chloroperbenzoic acid (19.0 g, 0.11 mol) was added portionwise to a stirred solution of 4-chloro-
6-fluoro-2-methylquinoline (6b, 19.6 g, 0.1 mol) in 1,2-dichloroethane (100 mL). The resulting mixture
was stirred at 50 °C for 3 h and cooled to room temperature. Then the solution was washed with 0.1 mol/L
NaHCO3 aqueous solution and brine, dried (MgSO4), filtered and concentrated to provide compound 9
as a yellow solid (19.7 g, 93.1%).
3.8. 4-Chloro-2-(chloromethyl)-6-fluoroquinoline (10)
Benzenesulfonyl chloride (28.2 mL, 0.22 mol) was added dropwise to a mixture of compound 9
(19.0 g, 0.09 mol) in toluene (95 mL) at 80 °C. Then the mixture was stirred for 3 h and cooled to
room temperature. The solution was washed with 0.1 mol/L NaHCO3 aqueous solution and brine,
dried (MgSO4), filtered and concentrated to provide a black oil. Ethanol (12 mL) was added and the
mixture was stirred at 0 °C until solidified. The precipitate was filtered and washed with cold ethanol
to afford compound 10 as yellow-green solid (11.6 g, 56.0%).

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3.9. General Procedure for the Preparation of Compounds 11a–d
A mixture of corresponding substituted phenythiol or benzylthiol (0.055 mol) and potassium
carbonate was stirred in acetonitrile at 50 °C for 10 min, then compound 10 (11.5 g, 0.05 mol) was
added. The reaction mixture was stirred for 2 h, cooled to room temperature and concentrated. The
residue was poured into water (150 mL), stirred for 0.5 h and separated by filtration to give compounds
11a–d as white solids (57.7–72.4%). Compound 11a was prepared from 4-methylthiophenol, MS (ESI)
m/z: 317.1, 318.1 [M+H+]. Compound 11b was prepared from 4-methoxyphenthiol, MS (ESI) m/z:
333.2, 334.2 [M+H+]. Compound 11c was prepared from furan-2-carbaldehyde, MS (ESI) m/z: 307.0,
308.0 [M+H+]. Compound 11d was prepared from 4-fluorobenzylthiol, MS (ESI) m/z: 335.1, 336.1
[M+H+].
3.10. General Procedure for the Preparation of Compounds 12a–d
30% Hydrogen peroxide (28.2 mL, 0.2 mol) was added dropwise to a stirred mixture of compound
11 (0.02 mol) and sodium tungstate (2 mmol) in acetic acid (60 mL). Then the mixture was stirred at
30 °C for 6 h, poured into water (150 mL), filtered and washed with water to give compounds 12a–d
as white solids (87.2–91.5%). Compound 12a, MS (ESI) m/z: 349.1, 350.0 [M+H+]. Compound 12b,
MS (ESI) m/z: 365.2, 366.2 [M+H+]. Compound 12c, MS (ESI) m/z: 339.0, 340.0 [M+H+]. Compound
12d, MS (ESI) m/z: 367.1, 368.1 [M+H+].
3.11. General Procedure for the Preparation of Compounds 13a–h
A mixture of compound 12 (2 mmol) and the corresponding aliphatic amine (8 mmol) was stirred at
reflux for 2–5 h and then cooled to room temperature. Water (200 mL) was added, and the product was
precipitated and collected, washed several times with water, and dried. The crude product was purified
by silica gel chromatography (MeOH:CH2Cl2 = 20:1) to afford the title compounds 13a–h (65–84%)
as white solids.
N1-(6-Fluoro-2-(((4-methylphenyl)sulfonyl)methyl)quinolin-4-yl)-N2,N2-dimethylethane-1,2-diamine (13a).
Prepared from 12a and N,N-dimethylethylenediamine. Yield: 72%; m.p.: 158–159 °C; MS (ESI) m/z:
402.0, 402.9 [M+H+]; 1H-NMR (300 MHz, DMSO-d6) δ (ppm): 8.03 (d, J = 9.9 Hz, 1H), 7.75–7.60 (m,
J = 9.6 7.8, 6.6 Hz, 3H), 7.49 (t, J = 8.4, 7.5 Hz, 1H), 7.38 (d, J = 7.8 Hz, 2H), 7.12 (s, 1H), 6.29 (s,
1H), 4.73 (s, 2H), 3.17 (q, 2H), 2.47 (t, 2H), 2.38 (s, 3H), 2.21 (s, 6H).
6-Fluoro-2-(((4-methylphenyl)sulfonyl)methyl)-N-(3-morpholin-4ylpropyl)quinolin-4-amine (13b). Prepared
from 12a and N-(3-aminopropyl)morpholine. Yield: 80%; m.p.: 183–184 °C; MS (ESI) m/z: 458.0,
1
459.9 [M+H+]; H-NMR (300 MHz, DMSO-d6) δ (ppm): 8.00 (d, J = 10.8 Hz, 1H), 7.67 (m,
J = 10.2, 8.4, 6.6 Hz, 3H), 7.49 (t, J = 9.0, 8.4 Hz, 1H), 7.38 (d, J = 7.5 Hz, 2H), 7.17 (s, 1H), 6.31 (s,
1H), 4.71 (s, 2H), 3.60 (t, 4H), 3.15 (q, 2H), 2.37 (d, 9H), 1.79–1.70 (qui, 2H).
6-Fluoro-2-(((4-methoxyphenyl)sulfonyl)methyl)-N-(3-morpholin-4ylpropyl)quinolin-4-amine (13c). Prepared
from 12b and N-(3-aminopropyl)morpholine. Yield: 84%; m.p.: 174–177 °C; MS (ESI) m/z: 474.0
1
[M+H+]; H-NMR (300 MHz, DMSO-d6) δ (ppm): 8.01 (dd, J = 11.1, 2.4 Hz, 1H), 7.71–7.65 (m,

Molecules 2012, 17
5879
J = 10.5, 8.7, 5.7 Hz, 3H), 7.49 (td, J = 8.7, 8.4, 2.6 Hz, 1H), 7.19 (t, 1H), 7.09 (d, J = 9.0 Hz, 2H),
6.30 (s, 1H), 4.69 (s, 2H), 3.83 (s, 3H), 3.60 (t, 4H), 3.15 (q, 2H), 2.37 (t, 6H), 1.80–1.71 (qui, 2H).
N1-(6-fluoro-2-(((furan-2-ylmethyl)sulfonyl)methyl)quinolin-4-yl)-N2,N2-dimethylethane-1,2-diamine
(13d). Prepared from 12c and N,N-dimethylethylenediamine. Yield: 65%; m.p.: 147–149 °C; MS (ESI)
1
m/z: 392.1, 393.1 [M+H+]; H-NMR (300 MHz, DMSO-d6) δ (ppm): 8.05 (d, J = 10.8 Hz, 1H),
7.87 (dd, J = 9.3, 6.0 Hz, 1H), 7.73 (d, 1H), 7.56 (td, J = 8.4, 6.3 Hz, 1H), 7.17 (t, 1H), 6.64 (d, J = 2.7 Hz,
2H), 6.52 (t, 1H), 4.80 (s, 2H), 4.61 (s, 2H), 3.38 (q, 2H), 2.56 (t, 2H), 2.23 (s, 6H).
6-Fluoro-2-(((furan-2-ylmethyl)sulfonyl)methyl)-N-(3-morpholin-4ylpropyl)quinolin-4-amine (13e). Prepared
from 12c and N-(3-aminopropyl)morpholine. Yield: 76%; m.p.: 155–157 °C; MS (ESI) m/z: 448.0,
1
449.0 [M+H+]; H-NMR (300 MHz, DMSO-d6) δ (ppm): 8.06 (dd, J = 10.8, 2.5 Hz, 1H), 7.87 (dd,
J = 9.3, 6.0 Hz, 1H), 7.74 (s, 1H), 7.56 (td, J = 9.0, 8.4, 2.5 Hz, 1H), 7.29 (t, 1H), 6.65 (d, J = 3.0 Hz,
1H), 6.62 (s, 1H), 6.53 (t, 1H), 4.81 (s, 2H), 4.61 (s, 2H), 3.58 (t, 4H), 3.33 (s, 2H), 2.39 (t, 6H),
1.86–1.81 (qui, 2H).
N1-(6-fluoro-2-(((4-fluorobenzyl)sulfonyl)methyl)quinolin-4-yl)-N2,N2-dimethylethane-1,2-diamine (13f).
Prepared from 12d and N,N-dimethylethylenediamine. Yield: 72%; m.p.: 177–180 °C; MS (ESI) m/z:
420.0, 421.0 [M+H+]; 1H-NMR (300 MHz, DMSO-d6) δ (ppm): 8.07 (d, J = 10.8 Hz, 1H), 7.92 (dd,
J = 8.7, 5.7 Hz, 1H), 7.60 (d, 3H), 7.26 (t, J = 8.7, 8.4 Hz, 2H), 7.18 (s, 1H), 6.65 (s, 1H), 4.65 (s, 2H),
4.52 (s, 2H), 3.39 (s, 2H), 2.58 (t, 2H), 2.24 (s, 6H).
N1-(6-fluoro-2-(((4-fluorobenzyl)sulfonyl)methyl)quinolin-4-yl)-N3,N3-dimethylpropane-1,3-diamine
(13g). Prepared from 12d and N,N-dimethyl-1,3-propane diamine. Yield: 77%; m.p.: 156–158 °C; MS
(ESI) m/z: 434.0, 435.0 [M+H+]; 1H-NMR (300 MHz, DMSO-d6) δ (ppm): 8.05 (d, J = 10.2 Hz, 1H),
7.91 (dd, J = 9.0, 6.0 Hz, 1H), 7.58 (t, 3H), 7.33 (t, 1H), 7.26 (t, J = 8.1 Hz, 2H), 6.61 (s, 1H), 4.65 (s,
2H), 4.51 (s, 2H), 3.29 (d, 2H), 2.35 (t, 2H), 2.17 (s, 6H), 1.86–1.78 (qui, 2H).
6-Fluoro-2-(((4-fluorobenzyl)sulfonyl)methyl)-N-(3-morpholin-4ylpropyl)quinolin-4-amine (13h). Prepared
from 12d and N-(3-aminopropyl)morpholine. Yield: 81%; m.p.: 192–195 °C; MS (ESI) m/z: 476.0
[M+H+]; 1H-NMR (300 MHz, DMSO-d6) δ (ppm): 8.07 (d, J = 10.5 Hz, 1H), 7.91 (dd, J = 8.7, 6.0 Hz,
1H), 7.58 (s, 3H), 7.26 (t, J = 8.7 Hz, 3H), 6.62 (s, 1H), 4.65 (s, 2H), 4.51 (s, 2H), 3.58 (s, 4H), 3.31 (s,
1H), 2.38 (s, 6H), 1.86–1.81 (qui, 2H).
3.12. Evaluation of the Biological Activity
The antiproliferative activity of compounds 8a–l and 13a–h was evaluated with non-small-cell lung
cancer cell line (H-460), human colorectal cancer cell line (HT-29), human liver cancer cell line
(HepG2) and stomach cancer cell line (SGC-7901) by the MTT method in vitro, with compound Iressa
as positive control. The cancer cells were cultured in minimum essential medium (MEM)
supplemented with 10% fetal bovine serum (FBS). Approximately 4 × 103 cells, suspended in MEM
medium, were plated onto each well of a 96-well plate and incubated in 5% CO2 at 37 °C for 24 h. The
test compounds were added to the culture medium at the indicated final concentrations and the cell
cultures were continued for 72 h. Fresh MTT was added to each well at a final concentration of

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5 μg/mL and incubated with cells at 37 °C for 4 h. The formazan crystals were dissolved in 100 μL
DMSO per each well, and the absorbency at 492 nm (for the absorbance of MTT formazan) and 630 nm
(for the reference wavelength) was measured with the ELISA reader. All of the compounds were tested
twice in each of the cell lines. The results expressed as IC50 (inhibitory concentration of 50%) were the
averages of two determinations and were calculated by using the Bacus Laboratories Incorporated
Slide Scanner (Bliss) software.
4. Conclusions
In conclusion, an efficient optimized method was employed to generate 2-arylvinylquinolines, using
anhydrous zinc chloride in refluxing DMF. Two series of novel 2-substituted-4-amino-6-halogenquinolines
were synthesized and evaluated for their antiproliferative activity against four human cancer cell lines
(H-460, HT-29, HepG2 and SGC-7901). The preliminary SARs showed that the improved activity
depended strongly on the introduction of an ethylene linkage between the nucleus and aryl moiety.
Among the tested compounds, compound 8e with a 4-methoxystyryl group at the C-2 position and a
dimethylaminoalkylamino substituent at the C-4 position is considered a promising lead for further
structural modifications.
Acknowledgments
This work was supported by a grant from National S & T Major Project (No. 2011ZX09102-001-006)
and the S & T Project of Liaoning Province (No. LJQ201107).
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Sample Availability: Samples of the compounds are available from the authors.
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