An efficient method for the synthesis of 3-Aryl-4,7-phenanthroline derivatives catalyzed by iodine

Article abstract of DOI:10.1002/jhet.954

A mild and efficient method for the synthesis of 3-aryl-4,7-phenanthroline derivatives via three-component reaction of aromatic aldehyde, quinolin-6-amine, and n-butylvinyl ether is described using iodine as catalyst. The features of this procedure are mild reaction conditions, good to high yields, and operational simplicity.

Full text of DOI:10.1002/jhet.954

September 2012
An Efficient Method for the Synthesis of 3‐Aryl‐4,7‐
1239
phenanthroline Derivatives Catalyzed by Iodine
Ming‐Yue Yin,a Mei‐Mei Zhang,b Wei Wang,a Yu‐Ling Li,a
a
*
and Xiang‐Shan Wang
aSchool of Chemistry and Chemical Engineering, Jiangsu Key Laboratory of Green Synthetic
Chemistry for Functional Materials, Xuzhou Normal University, Xuzhou Jiangsu 221116
People’s Republic of China
bThe Key Laboratory of Biotechnology on Medical Plant of Jiangsu Province, Xuzhou Normal
University, Xuzhou Jiangsu 221116, People’s Republic of China
*
E-mail: xswang1974@yahoo.com
Received January 22, 2011
DOI 10.1002/jhet.954
Published online 26 October 2012 in Wiley Online Library (wileyonlinelibrary.com).
A mild and efficient method for the synthesis of 3‐aryl‐4,7‐phenanthroline derivatives via three‐component
reaction of aromatic aldehyde, quinolin‐6‐amine, and n‐butylvinyl ether is described using iodine as catalyst.
The features of this procedure are mild reaction conditions, good to high yields, and operational simplicity.
J. Heterocyclic Chem., 49, 1239 (2012).
INTRODUCTION
to synthesize 3‐aryl‐4,7‐phenanthroline derivatives by a
reaction of aromatic aldehyde, quinolin‐6‐amine, and
n‐butylvinyl ether in tetrahydrofuran (THF).
Multicomponent reactions (MCRs) can be distinguished
from classical, sequential two‐component synthetic pro-
cesses in which three or more chemical starting materials
are used for product formation. Up to seven starting compo-
nents have been used, and often MCRs have been shown to
produce higher product yields than classical chemistry [1].
They provide a powerful tool toward the one‐pot synthesis
of diverse and complex compounds as well as small and
drug‐like heterocycles [2]. Owing to their convergence and
productivity, the MCRs have attracted considerable attention
from the point of view of organic synthetic chemistry [3].
Phenanthroline and its derivatives are well‐known
compounds for their metallic complexes. The latter possess
remarkable physiological and pharmacological activities.
These activities include anticancer (lanthanum(III)) [4],
antiinflammatory (copper(II)) [5], antitumor (Ru(II)) [6],
antimicrobial (copper(II)) [7], and antibacterial activity
(zinc (II)) [8]. In addition, it was reported that phenanthro-
line derivatives also had commendable antitumor activity
[9]; therefore, the synthesis of phenanthroline received a
considerable interest in recent years [10].
RESULTS AND DISCUSSION
Treatment of aromatic aldehyde 1, quinolin‐6‐amine 2,
and n‐butylvinyl ether 3 in THF in the presence of 5 mol
% iodine at reflux condition did not afford the desired
trans‐1‐butoxy‐1,2,3,4‐tetrahydro‐4,7‐phenanthroline deri-
vatives 4′. To our surprise, the butoxy group was not found
in the 1H‐NMR, with aromatized 3‐aryl‐4,7‐phenanthroline
being obtained in good yields (Scheme 1). Obviously, this
structure 4 was different from that of the simple substituted
aniline‐involved reactions reported by Sridharan et al. [12]
in 2008 and 2009.
Using the conversion of 2‐bromobenzaldehyde 1a, 2, and
3 as a model, several parameters were explored as shown in
Table 1. It was found that no reaction occurred at reflux
condition in the absence of iodine (Table 1, entry 1), and
the yield of 4a was much greater in the presence of various
quantities of the catalyst, reaching a maximum of 82% yield
with 5 mol % iodine (Table 1, entries 4–6). The yield of 4a
was also dependent on temperature (entries 2–4), proceed-
ing smoothly at reflux in THF. Different solvents were also
tested, and THF appeared to be the best medium for this
transformation (entry 5 vs. 7–10).
In view of the importance of phenanthroline derivatives
and as a continuation of our research devoted to the devel-
opment of new methods for the preparation of heterocycles
via MCRs (catalyzed by iodine) [11], herein, we would like
© 2012 HeteroCorporation

1240
M.-Y. Yin, M.-M. Zhang, W. Wang, Y.-L. Li, and X.-S. Wang
Vol 49
Table 2
Synthetic results of 4 catalyzed by iodine in THF.a
Scheme 1. The reaction of 1, 2 and n‐butylvinyl ether.
Isolated
Time (h) yields (%)
Entry
Ar
Products
1
2
3
4
5
6
7
8
2‐BrC6H4
3‐BrC6H4
4‐BrC6H4
3‐ClC6H4
2‐FC6H4
4a
4b
4c
4d
4e
4f
4g
4h
4i
12
16
12
12
20
12
15
20
16
12
21
12
10
82
76
79
84
82
73
76
86
94
90
78
84
82
4‐FC6H4
4‐CH3C6H4
4‐CH3OC6H4
2,3‐Cl2C6H3
3,4‐Cl2C6H3
3,4‐(CH3O)2C6H3
3,4‐OCH2OC6H3
3‐CF3C6H4
9
This process could tolerate both electron‐donating, such
as alkyl and alkoxyl, and electron‐withdrawing (halogen)
substituents on the aromatic aldehydes (Table 2). In all
cases, the reactions proceeded efficiently at reflux to afford
the corresponding 3‐aryl‐4,7‐phenanthrolines in good yields.
All the compounds were characterized by 1H‐NMR, IR, and
high resolution mass spectrometer (HRMS).
10
11
12
13
4j
4k
4l
4m
aReagents and conditions: 1 (2.0 mmol), 2 (0.288 g, 2.0 mmol), 3 (0.220 g,
2.2 mmol), I2 (0.1 mmol, 0.026 g), THF (10 mL), and reflux.
According to the literatures [2]e, we think that iodine
catalyzes the reaction as a mild Lewis acid [13]. The
mechanism was tentatively proposed as shown in Scheme
2. First, the Schiff base I may be formed by the reaction
of aromatic aldehyde and quinolin‐6‐amine. Then imino‐
Diels‐Alder reaction between the iodine‐activated Schiff
base II and n‐butylvinyl ether takes place selectively to form
the intermediate III for its stability. The unexpected n‐BuOH
loses induced by iodine results in dihydrophenanthroline IV,
which is further oxidized by air to afford aromatized 3‐aryl‐
4,7‐phenanthrolines 4.
Bruker‐400 spectrometer. HRMS analyses were carried out using
a Bruker‐micro‐TOF‐Q‐MS analyzer. All the reagents were
purchased from China National Pharmaceutical Group Corporation;
the solvent of THF was dried by Na and redistilled before use.
General procedure for the synthesis of 3‐aryl‐4,7‐phenanthroline
4. A dry 50‐mL flask was charged with aromatic aldehyde (2.0 mmol),
quinolin‐6‐amine (0.288 g, 2.0 mmol), n‐butylvinyl ether (0.220 g, 2.2
mmol), I2 (0.1 mmol, 0.026 g), and THF (10 mL). The reaction mixture
was stirred at reflux for 10–21 h, and then a small amount of DMF was
added to the mixture until all the precipitate was dissolved. The products
4 were obtained by filtration when the mixture was allowed to cool
down to room temperature.
3‐(2‐Bromophenyl)‐4,7‐phenanthroline 4a. mp: 209–210°C;
1H‐NMR (DMSO‐d6, 400 MHz): δH 7.47 (t, J = 7.6 Hz, 1H,
ArH), 7.56–7.60 (m, 1H, ArH), 7.71 (d, J = 7.6 Hz, 1H, ArH),
7.80–7.84 (m, 2H, ArH), 8.00 (d, J = 8.4 Hz, 1H, ArH), 8.24
(s, 2H, ArH), 9.06 (d, J = 4.0 Hz, 1H, ArH), 9.35 (d, J = 8.4
Hz, 1H, ArH), 9.40 (d, J = 8.8 Hz, 1H, ArH). IR (KBr): ν
3075, 3051, 3009, 1580, 1526, 1483, 1447, 1434, 1417, 1387,
1356, 1330, 1300, 1284, 1102, 1078, 1022, 836, 816, 793, 764,
733, 693 cm−1. HRMS (ESI, m/z): calcd for C18H12BrN2 [M+H+]
335.0184, found 335.0222.
EXPERIMENTAL
Melting points were determined in open capillaries and are un-
corrected. IR spectra were recorded on a Tensor 27 spectrometer
in KBr pellet. H‐NMR spectra were obtained from a solution in
1
DMSO‐d6 or CDCl3 with Me4Si as internal standard using a
Table 1
3‐(3‐Bromophenyl)‐4,7‐phenanthroline 4b. mp: 198–199°C; 1H‐
NMR (CDCl3, 400 MHz): δH 7.42 (t, J = 8.0 Hz, 1H, ArH), 7.61–7.64
Synthetic results of 4a under different reaction conditions.a
Isolated
Entry
Temp. (°C)
I2 (mol %)
Solvent
yields (%)
Scheme 2. Possible mechanism for the formation of products 4.
1
2
3
Reflux
r.t.
50
0
5
5
THF
THF
THF
0
Trace
76
4
5
6
7
8
9
10
Reflux
Reflux
Reflux
Reflux
Reflux
80
5
THF
THF
THF
CH3CN
Benzene
DMF
CHCl3
82
82
81
73
80
72
78
10
20
5
5
5
Reflux
5
aReagents and conditions: 2‐bromobenzaldehyde 1a (0.370 g, 2.0 mmol),
2 (0.288 g, 2.0 mmol), 3 (0.220 g, 2.2 mmol), and solvent (10 mL).
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

September 2012
An Efficient Method for the Synthesis of 3‐Aryl‐4,7‐phenanthroline
1241
Derivatives Catalyzed by Iodine
(m, 2H, ArH), 8.03 (d, J = 8.8 Hz, 1H, ArH), 8.14 (d, J = 8.0 Hz, 1H,
ArH), 8.26–8.32 (m, 2H, ArH), 8.41 (s, 1H, ArH), 8.91 (d, J = 8.4 Hz,
1H, ArH), 8.95 (d, J = 8.8 Hz, 1H, ArH), 9.03 (d, J = 4.0 Hz, 1H, ArH).
IR (KBr): ν 3059, 3025, 2999, 1585, 1559, 1525, 1485, 1443, 1434,
1387, 1359, 1299, 1280, 1258, 1068, 993, 839, 785, 705, 679 cm−1.
HRMS (ESI, m/z): calcd for C18H12BrN2 [M+H+] 335.0184, found
1186, 1111, 1027, 849, 835, 809, 783 cm−1. HRMS (ESI, m/z):
calcd for C19H15N2O [M+H+] 287.1184, found 287.1220.
3‐(2,3‐Dichlorophenyl)‐4,7‐phenanthroline 4i. mp: 237–238°C;
1H‐NMR (CDCl3, 400 MHz): δH 7.37–7.41 (m, 1H, ArH), 7.58–
7.68 (m, 3H, ArH), 7.94 (d, J = 8.4 Hz, 1H, ArH), 8.30–8.33 (m,
2H, ArH), 8.96 (d, J = 8.8 Hz, 1H, ArH), 9.06 (d, J = 8.8 Hz, 1H,
ArH), 9.05–9.06 (m, 1H, ArH). IR (KBr): ν 3061, 1590,
1554, 1527, 1486, 1441, 1432, 1389, 1355, 1305, 1283, 1192,
1155, 1094, 1041, 853, 793, 775, 748, 706 cm−1. HRMS
(ESI, m/z): calcd for C18H11Cl2N2 [M+H+] 325.0299, found
325.0317.
3‐(3,4‐Dichlorophenyl)‐4,7‐phenanthroline 4j. mp: 216–217°C;
1H‐NMR (DMSO‐d6, 400 MHz): δH 7.60–7.65 (m, 2H, ArH), 8.02
(d, J = 8.8 Hz, 1H, ArH), 8.06 (d, J = 9.2 Hz, 1H, ArH), 8.26–8.31
(m, 2H, ArH), 8.37 (s, 1H, ArH), 8.90 (d, J = 8.0 Hz, 1H, ArH),
8.95 (d, J = 8.4 Hz, 1H , ArH), 9.04 (d, J = 3.6 Hz, 1H, ArH). IR
(KBr): ν 3060, 3009, 1599, 1585, 1553, 1529, 1487, 1472, 1444,
1389, 1301, 1266, 1139, 1089, 1067, 1027, 914, 836, 808, 779
cm−1. HRMS (ESI, m/z): calcd for C18H11Cl2N2 [M+H+] 325.0299,
found 325.0317.
3‐(3,4‐Dimethoxyphenyl)‐4,7‐phenanthroline 4k.mp: 170–171°C;
1H‐NMR (DMSO‐d6, 400 MHz): δH 3.87 (s, 3H, CH3O), 3.94
(s, 3H, CH3O), 7.14 (d, J = 8.4 Hz, 1H, ArH), 7.77 (dd, J=
8.4 Hz, J′ = 4.0 Hz, 1H, ArH), 7.93 (d, J = 8.4 Hz, 1H, ArH),
7.97 (s, 1H, ArH), 8.18–8.23 (m, 2H, ArH), 8.36 (d, J = 8.8 Hz,
1H, ArH), 9.01 (d, J = 4.0 Hz, 1H, ArH), 9.30 (d, J = 8.8 Hz,
2H, ArH). IR (KBr): ν 3008, 2963, 2936, 2910, 2837, 1596,
1564, 1530, 1510, 1481, 1459, 1441, 1415, 1359, 1338, 1274,
1224, 1217, 1161, 1135, 1021, 845, 806, 770 cm−1. HRMS
(ESI, m/z): calcd for C20H17N2O2 [M+H+] 317.1290, found
317.1324.
3‐(Methylenedioxyphenyl)‐4,7‐phenanthroline 4l.mp:240–241°C;
1H‐NMR (DMSO‐d6, 400 MHz): δH 6.14 (s, 2H, CH2), 7.11 (d, J
= 8.8 Hz, 1H, ArH), 7.77 (dd, J = 8.0 Hz, J′ = 4.0 Hz, 1H,
ArH), 7.91–7.93 (m, 2H, ArH), 8.17–8.21 (m, 2H, ArH), 8.30
(d, J = 8.8 Hz, 1H, ArH), 9.01 (dd, J = 4.0 Hz, J′ = 1.6 Hz,
1H, ArH), 9.29 (d, J = 8.8 Hz, 2H, ArH). IR (KBr): ν 3060,
2990, 2913, 1604, 1587, 1530, 1502, 1482, 1441, 1392, 1366,
1288, 1260, 1238, 1106, 1035, 927, 850, 840, 800, 788 cm−1.
HRMS (ESI, m/z): calcd for C19H13N2O2 [M+H+] 301.0977,
found 301.1019.
335.0211.
3‐(4‐Bromophenyl)‐4,7‐phenanthroline 4c. mp: 236–237°C;
1H‐NMR (CDCl3, 400 MHz): δH 7.63 (dd, J = 8.4 Hz, J′ = 4.4 Hz,
1H, ArH), 7.68 (d, J = 8.4 Hz, 2H, ArH), 8.04 (d, J = 8.4 Hz,
1H, ArH), 8.11 (d, J = 8.4 Hz, 2H, ArH), 8.25–8.31 (m, 2H, ArH),
8.91 (d, J = 8.0 Hz, 1H, ArH), 8.95 (d, J = 8.8 Hz, 1H, ArH),
9.02–9.03 (m, 1H, ArH). IR (KBr): ν 3068, 3036, 3004, 1580,
1556, 1527, 1480, 1440, 1430, 1395, 1356, 1302, 1280, 1185,
1098, 1073, 1060, 1005, 993, 851, 827, 804, 787 cm−1. HRMS
(ESI, m/z): calcd for C18H12BrN2 [M+H+] 335.0184, found
335.0224.
3‐(3‐Chlorophenyl)‐4,7‐phenanthroline 4d. mp: 210–211°C;
1H NMR (CDCl3, 400 MHz): δH 7.45–7.51 (m, 2H, ArH), 7.64
(dd, J = 8.4 Hz, J′ = 4.4 Hz, 1H, ArH), 8.04 (d, J = 8.8 Hz, 1H,
ArH), 8.08–8.10 (m, 1H, ArH), 8.25–8.33 (m, 3H, ArH), 8.91
(d, J = 8.4 Hz, 1H, ArH), 8.96 (d, J = 8.8 Hz, 1H, ArH),9.03
(d, J = 4.0 Hz, 1H, ArH). IR (KBr): ν 3058, 3030, 3007, 2961,
1593, 1582, 1563, 1525, 1480, 1443, 1421, 1389, 1360, 1299,
1284, 1259, 1081, 1070, 901, 838, 784, 734, 714, 680 cm−1
.
HRMS (ESI, m/z): calcd for C18H12ClN2 [M+H+] 291.0689,
found 291.0705.
3‐(2‐Fluorophenyl)‐4,7‐phenanthroline 4e. mp: 165–166°C;
1H‐NMR (DMSO‐d6, 400 MHz): δH 7.40–7.45 (m, 2H, ArH),
7.57–7.61 (m, 1H, ArH), 7.81 (dd, J = 8.4 Hz, J′ = 4.0 Hz, 1H,
ArH), 8.12–8.16 (m, 2H, ArH), 8.21–8.27 (m, 2H, ArH),
9.05 (d, J = 4.4 Hz, 1H, ArH), 9.31 (d, J = 8.4 Hz, 1H,
ArH), 9.38 (d, J = 8.8 Hz, 1H, ArH). IR (KBr): ν 3050,
3027, 1614, 1585, 1526, 1486, 1441, 1390, 1363, 1307,
1283, 1210, 1112, 1068, 939, 838, 784, 751, 740 cm−1
.
HRMS (ESI, m/z): calcd for C18H12FN2 [M+H+] 275.0985,
found 275.1008.
3‐(4‐Fluorophenyl)‐4,7‐phenanthroline 4f. mp: 200–201°C;
1H‐NMR (DMSO‐d6, 400 MHz): δH 7.41 (t, J = 8.8 Hz, 2H,
ArH), 7.79 (dd, J = 8.4 Hz, J′ = 4.4 Hz, 1H, ArH), 8.20–8.26
(m, 2H, ArH), 8.36–8.44 (m, 3H, ArH), 9.03 (d, J = 4.0 Hz,
1H, ArH), 9.32 (d, J = 8.4 Hz, 1H, ArH), 9.36 (d, J = 8.8 Hz,
1H, ArH). IR (KBr): ν 3051, 3003, 1598, 1567, 1504, 1484,
1442, 1406, 1383, 1320, 1298, 1281, 1217, 1161, 1063, 834,
801, 775 cm−1. HRMS (ESI, m/z): calcd for C18H12FN2 [M
+H+] 275.0985, found 275.1011.
3‐(4‐(Trifluoromethyl)phenyl)‐4,7‐phenanthroline 4m.mp: 187–
1
189°C; H‐NMR (DMSO‐d6, 400 MHz): δH 7.78 (dd, J = 8.4 Hz,
J′ = 4.0 Hz, 1H, ArH), 7.92 (d, J = 8.0 Hz, 2H, ArH), 8.20–8.27
(m, 2H, ArH), 8.43 (d, J = 8.8 Hz, 1H, ArH), 8.54 (d, J = 8.0 Hz,
2H, ArH), 9.03 (d, J = 4.0 Hz, 1H, ArH), 9.31 (d, J = 8.4 Hz, 1H,
ArH), 9.39 (d, J = 8.8 Hz, 1H, ArH). IR (KBr): ν 3067, 3032,
3008, 1940, 1615, 1580, 1566, 1530, 1484, 1448, 1404, 1391,
1322, 1282, 1153, 1125, 1071, 1012, 994, 983, 862, 837, 811, 784,
719, 687 cm−1. HRMS (ESI, m/z): calcd for C20H12F3N2 [M+H+]
325.0953, found 325.0967.
3‐p‐Tolyl‐4,7‐phenanthroline 4g. mp: 179–180°C; 1H‐NMR
(DMSO‐d6, 400 MHz): δH 2.41 (s, 3H, CH3), 7.39 (d, J = 8.0 Hz,
1H, ArH), 7.77 (d, J = 8.4 Hz, J′ = 4.4 Hz, 1H, ArH), 8.18–8.26
(m, 4H, ArH), 8.34 (d, J = 8.8 Hz, 1H, ArH), 9.02 (dd, J = 4.4 Hz,
J′ = 1.6 Hz, 1H, ArH), 9.29–9.34 (m, 2H, ArH). IR (KBr): ν 3059,
3026, 3001, 2950, 2920, 1592, 1560, 1504, 1479, 1440, 1386,
1355, 1297, 1278, 1182, 1110, 1095, 1061, 1018, 851, 832,
807, 784, 744, 719 cm−1. HRMS (ESI, m/z): calcd for
C19H15N2 [M+H+] 271.1235, found 271.1258
CONCLUSION
3‐(4‐Methoxyphenyl)‐4,7‐phenanthroline 4h. mp: 200–201°C;
1H‐NMR (DMSO‐d6, 400 MHz): δH 3.86 (s, 3H, CH3O), 7.14
(dd, J = 6.8 Hz, J′ = 2.0 Hz, 2H, ArH), 7.77 (dd, J = 8.0 Hz,
J′ = 4.0 Hz, 1H, ArH), 8.17–8.23 (m, 2H, ArH), 8.30–8.33
(m, 3H, ArH), 9.01 (d, J = 4.4 Hz, J′ = 1.6 Hz, 1H, ArH), 9.28–
9.31 (m, 2H, ArH). IR (KBr): ν 3054, 2955, 2835, 1603, 1596,
1566, 1531, 1508, 1483, 1441, 1415, 1391, 1304, 1289, 1254,
In conclusion, we found a mild and efficient method for
the synthesis of 3‐aryl‐4,7‐phenanthroline derivatives via
three‐component reaction of aromatic aldehyde, quinolin‐
6‐amine 2, and n‐butylvinyl ether using iodine as catalyst.
The features of this procedure are mild reaction conditions,
good yields, and operational simplicity.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

1242
M.-Y. Yin, M.-M. Zhang, W. Wang, Y.-L. Li, and X.-S. Wang
Vol 49
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foundation (08KJD150019), and Qing Lan Project (08QLT001)
of Jiangsu Education Committee for financial support.
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Journal of Heterocyclic Chemistry
DOI 10.1002/jhet