Dowex-50w promoted friedlaender synthesis of substituted quinolines under solvent-free conditions

Article abstract of DOI:10.3987/COM-10-12078

An efficient method for the synthesis of substituted quinolines using Dowex-50W ion exchange resin as reusable eco-friendly catalyst vai Friedlaender annulation under solvent-free conditions is described. The Japan Institute of Heterocyclic Chemistry.

Full text of DOI:10.3987/COM-10-12078

HETEROCYCLES, Vol. 83, No. 2, 2011
331
HETEROCYCLES, Vol. 83, No. 2, 2011, pp. 331 - 338. © The Japan Institute of Heterocyclic Chemistry
Received, 9th October, 2010, Accepted, 13th December, 2010, Published online, 27th December, 2010
DOI: 10.3987/COM-10-12078
DOWEX-50W
PROMOTED
QUINOLINES
FRIEDLÄNDER
UNDER
SYNTHESIS
OFSUBSTITUTED
CONDITIONS
SOLVENT-FREE
Huey-Min Wang,*a Rei-Sheu Hou,a Hau-Dung Du,b Iou-Jiun Kang,c and
Ling-Ching Chen*b
a Chung Hwa University of Medical Technology, Tainan 717, Taiwan, R.O.C.
b Graduate Institute of Pharmaceutical Sciences, College of Pharmacy, Kaohsiung
Medical University, Kaohsiung 807, Taiwan, R.O.C.
E-mail: m715003@cc.kmu.edu.tw
c
Division of Biotechnology and Pharmaceutical Research, National Health
Research Institutes, Miaoli County 350, Taiwan, R.O.C.
Abstract - An efficient method for the synthesis of substituted quinolines using
Dowex-50W ion exchange resin as reusable eco-friendly catalyst vai Friedländer
annulation under solvent-free conditions is described.
Quinoline derivatives have been well known not only in medicinal chemistry, because of their wide
occurrence in natural products1 and drugs,2 but also in polymer chemistry, electronics and optoelectronics
for their excellent mechanical properties.3 Versatile methods for the synthesis of the quinoline ring
system have been developed.4 Friedländer annulation is one of the most simple and straightforward
approaches for the synthesis of quinoline derivatives.
Homogeneous acidic catalysts such as H2SO4, HCl, AlCl3, and BF3, among others, are commonly used
for organic synthesis carried out in laboratories and industries. However, the above-mentioned catalysts
have several disadvantages because they are corrosive, toxic or volatile, and generate large amount of
waste. In order to overcome all the drawbacks in the use of environmentally hazardous homogeneouse
catalysts, new solid acids such as: zeolites, clays, alumina, heteropolyacids, and acidic resins have been
tested.5 Each catalyst has its own advantages and disadvantages. It is always interesting to develop a new
environmental benign catalyst for organic transformation.
Recently, the use of ion exchange resins in organic synthesis has received great attention.6 It is easy to
measure, safe to use, and readily removed at the end of the reaction. We report here using Dowex-50 ion

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HETEROCYCLES, Vol. 83, No. 2, 2011
exchange resin as catalyst for the first time to synthesize substituted quinolines via Friedländer annulation
under solvent-free conditions.7
Treatment of 2-aminobenzophenone (1) and aryl ketones (2) with Dowex-50 as catalyst at 100 °C for 0.5
h caused cyclodehydration to give substituted quinolines (3) in good yields (Scheme 1). The results are
given in Table 1. When the reaction is conducted in a conventional solvent, such as acetonitrile, the
preparation of 2,4-dephenylquinoline (3a) needs refluxing for 10 h.
Ph
Ph
R1
R
Dowex-50W
R
R1
Ar
O
O
Ar
100 °C, 30min
NH2
N
2
1
3
a, R=H
b, R=Cl
Scheme 1
Table 1. Synthesis of substituted quinolines (3a-o)
Entry
1
R
H
H
H
H
H
H
H
H
H
H
H
Cl
Cl
Cl
Cl
Ar
R1
H
Product
3a
Yield (%)
80
Ph
2
4-MeC6H4
4-MeOC6H4
4-FC6H4
4-ClC6H4
4-BrC6H4
2-Furyl
H
75
3b
3c
3
H
76
4
H
74
3d
3e
5
H
82
6
H
84
3f
7
H
73
3g
8
2-Thienyl
4-NO2C6H4
Ph
H
75
3h
3i
9
H
85
10
11
12
13
14
15
Me
Ph
H
80
3j
Ph
78
3k
3l
4-BrC6H4
4-ClC6H4
4-MeC6H4
4-NO2C6H4
84
H
85
3m
3n
3o
H
83
H
90

HETEROCYCLES, Vol. 83, No. 2, 2011
333
This method is equally effective for cyclic ketone. Cyclopentanone, cyclohexanone and cycloheptanone
were chosen to react with 2-aminobenzophenone (1a) to give the corresponding substituted quinolines (4,
5 and 6) in 81, 80 and 83% yields, respectively (Scheme 2).
Ph
n = 1
N
4
Ph
O
Ph
Dowex-50W
O
n = 2
n = 3
100 °C, 30 min
NH2
n
N
1a
5
Ph
N
6
Scheme 2
In conclusion, we have demonstrated a simple and efficient procedure for the Friedländer synthesis of
substituted quinolines using Dowex-50W as catalyst under solvent-free conditions. The significant
features of this method include operational simplicity, safe to use, and readily recovered at the end of the
reaction.
ACKNOWLEDGEMENT
We gratefully acknowledge the National Council Science of Republic of China for financial support of
this work.
EXPERIMENTAL
All melting points are uncorrected. The IR spectra were recorded on a Shimadzu IR-27 G
1
13
spectrophotometer. H NMR and C NMR spectra were recorded on a Varian Unity Plus 400 MHz.
Chemical shifts () were measured in ppm with respect to TMS. MS were obtained on a JEOL JMS
D-300 instrument.
Typical procedure for the synthesis of 2,4-diphenylquinoline (3a)
A mixture of acetophenone (2a) (240mg, 2.0mmol), 2-aminobenzophenone (1a) (197mg, 1.0mmol), and

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HETEROCYCLES, Vol. 83, No. 2, 2011
Dowex-50W (100mg) was heated for 0.5 h at 100 °C. After cooling to room terperature, the reaction was
dissolved in ethyl acetate and Dowex-50W was recovred by filtration. The filtrate was concentrated under
reduced pressure and the residue was chromatographed on silica gel eluting with EtOAc-hexane (1:5) to
give 3a.
2,4-Diphenylquinoline (3a)
1
Mp 110-111 °C (Lit.,8 mp 112-113 °C). IR (KBr) : 3050, 1584, 1541 cm-1. H NMR (CDCl3) :
7.45-7.59 (m, 9H), 7.74 (ddd, J = 1.2, 6.8, 15.2 Hz, 1H), 7.83 (s, 1H), 7.92 (dd, J = 0.8, 8.4 Hz, 1H), 8.20
(d, J = 8.4 Hz, 2H), 8.26 (d, J = 8.4 Hz, 1H). 13C NMR (CDCl3,100 MHz) : 119.3, 125.6, 125.7, 126.3,
127.5, 128.4, 128.5, 128.8, 129.3, 129.4, 129.5 130.0, 138.3, 139.6, 148.7, 149.1, 156.8. MS (EI) m/z: 281
(M+), 280, 202, 176, 139, 125.
2-(4-Methylphenyl)-4-phenylquinoline (3b)
1
Mp 95-96 °C (Lit.,9 mp 116-117 °C). IR (KBr) : 3049, 1624, 1548 cm-1. H NMR (CDCl3) : 2.43 (s,
3H), 7.34 (d, J = 8.0 Hz, 2H), 7.44-7.58 (m, 6H), 7.71-7.75 (m, 1H), 7.81 (s, 1H), 7.89 (dd, J = 1.0, 8.0
Hz, 1H), 8.10 (d, J = 8.0 Hz, 2H), 8.23 (d, J = 8.0 Hz, 1H). 13C NMR (CDCl3,100 MHz) : 21.3, 119.1,
125.5, 125.6, 126.0, 127.3, 128.3, 128.5, 129.3, 129.5, 129.9, 136.7, 138.4, 139.3, 148.7, 148.9, 156.7.
MS (EI) m/z: 295 (M+), 294, 202, 145, 139.
2-(4-Methoxyphenyl)-4-phenylquinoline (3c)
Mp 78-79 °C (Lit.,8 mp 77-79 °C). IR (KBr) : 1736 cm-1. 1H NMR (CDCl3) : 3.89 (s, 3H), 7.06 (ddd, J
= 2.6, 2.6, 9.2 Hz, 2H), 7.44-7.58 (m, 6H), 7.69-7.75 (m, 1H), 7.79 (s, 1H), 7.89 (ddd, J = 0.8, 0.8, 8.4 Hz,
1H), 8.19 (ddd, J = 2.4, 2.4, 9.2 Hz, 2H), 8.24 (ddd, J = 0.6, 0.8, 8.4 Hz, 1H). 13C NMR (CDCl3,100 MHz)
: 55.3, 114.1, 118.8, 125.4, 125.5, 125.9, 128.3, 128.5, 128.8, 129.4, 129.5, 129.8, 130.1, 132.0, 137.4,
138.4, 148.7, 149.0, 156.3, 160.8. MS (EI) m/z: 311 (M+), 310, 268, 267, 140, 139, 132.
2-(4-Fluorophenyl)-4-phenylquinoline (3d)
Mp 63-64 °C. IR (KBr) : 3056, 1593, 1546 cm-1. 1H NMR (CDCl3) : 7.19-7.24 (m, 2H), 7.47-7.57 (m,
6H), 7.72-7.76 (m, 1H), 7.78 (s, 1H), 7.91 (dd, J = 1.0, 8.4 Hz, 1H), 8.18-8.24 (m, 3H). 13C NMR
(CDCl3,100 MHz) : 115.4, 115.7, 118.7, 125.5, 126.2, 128.3, 128.4, 129.2, 129.3, 129.4, 129.5, 129.8,
135.5, 135.6, 138.1, 148.6, 149.1, 155.5, 162.4. MS (EI) m/z: 299 (M+), 298, 220, 202, 201, 139, 125.
Anal. Calcd for C12H14NF: C, 84.26, H, 4.71, N, 4.68. Found: C, 84.39, H, 4.54, N, 4.53.

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2-(4-Chlorophenyl)-4-phenylquinoline (3e)
1
Mp 104-105 °C (Lit.,10 mp 106 °C). IR (KBr) : 3055, 1589, 1542 cm-1. H NMR (CDCl3) : 7.47-7.57
(m, 8H), 7.74-7.77 (m, 1H), 7.79 (s, 1H), 7.91 (d, J = 8.0 Hz, 1H), 8.14-8.18 (m, 2H), 8.23 (d, J = 8.4 Hz,
1H). 13C NMR (CDCl3,100 MHz) : 118.6, 125.6, 125.7, 126.5, 128.4, 128.6, 128.8, 128.9, 129.5, 129.6,
130.0, 136.5, 137.9, 138.2, 148.7, 149.4, 155.4. MS (EI) m/z: 317 (M++2), 315 (M+), 314, 220, 202, 176,
139.
2-(4-Bromophenyl)-4-phenylquinoline (3f)
1
Mp 111-112 °C (Lit.,11 mp 128-129 °C). IR (KBr) : 3029, 1584, 1539 cm-1. H NMR (CDCl3) :
7.48-7.57 (m, 6H), 7.64-7.67 (m, 2H), 7.73-7.87 (m, 2H), 7.91 (dd, J = 1.0, 8.4 Hz, 1H), 8.08-8.11 (m,
13
2H), 8.24 (d, J = 8.4 Hz, 1H). C NMR (CDCl3,100 MHz) : 118.7, 123.8, 125.5, 125.7, 126.4, 128.4,
128.5, 129.0, 129.4, 129.6, 130.0, 131.8, 138.1, 138.3, 148.6, 149.3, 155.3. MS (EI) m/z: 361 (M++2), 360
(M++1), 359 (M+), 279, 278, 202, 139.
2-(2-Furyl)-4-phenylquinoline (3g)
Mp 98-99 °C (Lit.,9 mp 109-111 °C). IR (KBr) : 3060, 1594, 1546 cm-1. 1H NMR (CDCl3) : 6.60 (dd, J
= 1.6, 3.6 Hz, 1H), 7.25 (m, 1H), 7.43-7.57 (m, 6H), 7.63 (dd, J = 0.6, 1.8 Hz, 1H), 7.74 (ddd, J = 1.0, 6.8,
8.4 Hz, 1H), 7.78 (s, 1H), 7.87 (dd, J = 1.2, 8.4 Hz, 1H), 8.21 (d, J = 8.4 Hz, 1H). 13C NMR (CDCl3,100
MHz) : 110.1, 112.1, 117.6, 125.6, 125.7, 126.1, 128.3, 128.4, 129.4, 129.5, 129.8, 138.0, 144.0, 148.4,
148.5, 148.9, 153.6. MS (EI) m/z: 271 (M+), 270, 243, 242, 241, 120.
4-Phenyl-2-(2-thienyl)quinoline (3h)
Mp 92-93 °C (Lit.,9 mp 89-92 °C). IR (KBr) : 3054, 1585, 1543 cm-1. 1H NMR (CDCl3) : 7.16 (dd, J =
3.8, 5.0 Hz, 1H), 7.42-7.57 (m, 7H), 7.68-7.74 (m, 3H), 7.84 (dd, J = 0.8, 8.4 Hz, 1H), 8.16 (d, J = 8.8 Hz,
1H). 13C NMR (CDCl3,100 MHz) : 117.8, 125.6, 125.7, 125.8, 126.0, 128.0, 128.4, 128.5, 128.6, 129.4,
129.5, 129.6, 138.0, 145.3, 148.5, 148.7, 151.7. MS (EI) m/z: 287 (M+), 286, 253, 202, 200.
2-(4-Nitrophenyl)-4-phenylquinoline (3i)
Mp 156-157 °C (Lit.,11 mp 162-163 °C). IR (KBr) : 3055, 1588, 1547 cm-1. 1H NMR (CDCl3) :
7.52-7.58 (m, 6H), 7.77-7.81 (m, 1H), 7.86 (s, 1H), 7.95 (d, J = 8.0 Hz, 1H), 8.27 (d, J = 8.4 Hz, 1H),
8.37-8.42 (m, 4H). 13C NMR (CDCl3,100 MHz) : 119.0, 120.8, 123.3, 123.9, 125.7, 126.0, 127.2, 128.1,
128.2, 128.6, 129.3, 129.4, 130.0, 130.2, 130.9, 137.8, 145.3, 148.2, 148.7, 149.8, 153.9. MS (EI) m/z:
326 (M+), 325, 280, 278, 202, 176, 139.

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3-Methyl-2,4-diphenylquinoline (3j)
Mp 134-135 °C (Lit.,12 mp 145-146 °C). IR (KBr) : 3048, 1609, 1568 cm-1. 1H NMR (CDCl3) : 2.17 (s,
3H), 7.32-7.34 (m, 2H), 7.40-7.58 (m, 8H), 7.62-7.68 (m, 3H), 8.20 (d, J = 8.4 Hz, 1H).13C NMR
(CDCl3,100 MHz) : 18.5, 115.8, 126.1, 126.5, 126.9, 127.7, 127.9, 128.0, 128.2, 128.4, 128.6, 128.8,
129.2, 129.3, 137.5, 141.3, 146.1, 147.6, 160.6. MS (EI) m/z: 295 (M+), 294, 217, 189, 139.
2,3,4-Triphenylquinoline (3k)
1
Mp 190-191 °C (Lit.,13 mp 189-190 °C). IR (KBr) : 3052, 1603, 1547 cm-1. H NMR (CDCl3) :
6.88-6.91 (m, 2H), 6.99-7.02 (m, 3H), 7.14-7.16 (m, 2H), 7.21-7.23 (m, 3H), 7.26-7.31 (m, 3H),
7.38-7.40 (m, 2H), 7.46 (ddd, J = 1.2, 6.8, 8.4 Hz, 1H), 7.59 (dd, J = 1.2, 8.4 Hz, 1H), 7.74 (ddd, J = 1.2,
13
6.8, 8.4 Hz, 1H), 8.28 (d, J = 8.4 Hz, 1H). C NMR (CDCl3,100 MHz) : 126.2, 126.4, 126.5, 127.1,
127.2, 127.4, 127.5, 127.6, 129.2, 129.5, 129.8, 130.1, 131.2, 132.8, 136.8, 138.2, 141.0, 147.2, 147.5,
158.8. MS (EI) m/z : 357 (M+), 356, 278, 176, 171.
6-Chloro-2-(4-bromophenyl)-4-phenylquinoline (3l)
1
Mp 173-175 °C (Lit.,14 mp 174-176 °C). IR(KBr) : 3060, 1062, 1591 cm-1. H NMR (CDCl3) :
7.54-7.58 (m, 5H), 7.64-7.70 (m, 3H), 7.80 (s, 1H), 7.86 (d, J = 2.2 Hz, 1H), 8.08 (d, J = 11.2 Hz, 2H),
8.15 (d, J = 12.4Hz, 1H). MS (EI) m/z: 397 (M++4), 395 (M++2), 393 (M+), 358. Anal. Calcd for
C21H13BrClN: C, 63.90, H, 3.32, N, 3.55. Found: C, 63.87, H, 3.14, N, 3.58.
6-Chloro-2-(4-chlorophenyl)-4-phenylquinoline (3m)
1
Mp 162-162 °C (Lit.,14 mp 164-166 °C). IR(KBr) : 3056, 1066, 1585 cm-1. H NMR (CDCl3) :
7.49-7.58 (m, 7H), 7.68 (dd, J = 3.2, 12.0 Hz, 1H), 7.80 (s, 1H), 7.86 (d, J = 2.8 Hz, 1H), 8.13 (d, J = 2.0
Hz, 2H), 8.16 (d, J = 3.2 Hz, 1H). MS (EI) m/z: 353 (M++4), 351 (M++2), 349 (M+), 314. Anal. Calcd for
C21H13Cl2N: C, 72.02, H, 3.74, N, 4.00. Found: C, 72.06, H, 3.78, N, 4.23.
6-Chloro-2-(4-methylphenyl)-4-phenylquinoline (3n)
Mp 132-134 °C (Lit.,14 mp 132-134 °C). IR(KBr) : 3046, 1602, 1581 cm-1. 1H NMR (CDCl3) : 2.44 (s,
3H), 7.33 (d, J = 10.8 Hz, 2H), 7.52-7.57 (m, 5H), 7.66 (dd, J = 2.8, 12.0 Hz), 7.82 (s, 1H), 7.85 (d, J =
2.8 Hz, 1H), 8.09 (d, J = 11.2 Hz, 2H), 8.16 (d, J = 12.0 Hz, 1H). MS (EI) m/z : 331 (M++2), 329 (M+),
294. Anal. Calcd for C22H16ClN: C, 80.11, H, 4.89, N, 4.25. Found: C, 80.18, H, 4.77, N, 4.35.
6-Chloro-2-(4-nitrophenyl)-4-phenylquinoline (3o)

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337
1
Mp 219-220 °C (Lit.,14 mp 218-220 °C). IR(KBr) : 3040, 1611, 1524 cm-1., H NMR (CDCl3) :
7.53-7.58 (s, 5H), 7.72 (dd, J = 3.2, 12.0 Hz, 1H), 7.88 (s, 1H), 7.90 (d, J = 3.2 Hz, 1H), 8.20 (d, J = 12.4
Hz, 1H). MS (EI) m/z: 362 (M++2), 360 (M+), 314, 278. Anal. Calcd for C21H13ClN2O3: C, 69.91, H, 3.63,
N, 7.76. Found: C, 69.95, H, 3.72, N, 7.62.
2,3-Dihydro-9-phenyl-1H-cyclopenta[b]quinoline (4)
Mp 131-132 °C (Lit.,15 mp 130 °C). IR (KBr) : 3058, 2923, 1569, 1485, 831 cm-1. 1H NMR (CDCl3, 400
MHz) : 2.15-2.19 (m, 2H), 2.91 (t, J = 7.2 Hz, 2H), 3.24 (t, J = 7.6 Hz, 2H), 7.35-7.41 (m, 3H),
7.47-7.54 (m, 3H), 7.60-7.64 (m, 2H), 8.06-8.08 (m, 1H); 13C NMR (CDCl3, 100 MHz) : 23.5, 30.3, 35.1,
125.4, 125.6, 126.2, 128.2, 128.4, 129.2, 133.6, 136.7, 142.6, 147.9, 167.4; EI-MS m/z: 245 (M+), 244,
217, 168.
9-Pheyl-1,2,3,4-tetrahydroacridine (5)
Mp 137 °C (Lit.,15 mp 138 °C). IR (KBr) : 3061, 2940, 2860, 1570, 1485, 1440, 1220, 765, 705 cm-1. 1H
NMR (CDCl3, 400 MHz) : 1.75-1.81 (m, 2H), 1.93-1.99 (m, 2H), 2.59 (t, J = 6.8 Hz, 2H), 3.18 (t, J =
6.8 Hz, 2H), 7.20-7.35 (m, 4H), 7.46-7.55 (m, 3H), 7.63-7.65 (m, 1H), 8.17 (d, J = 8.4 Hz, 1H); 13C NMR
(CDCl3, 100 MHz) : 22.4, 22.7, 27.8, 33.3, 125.8, 125.8, 126.6, 127.1, 127.9, 128.6, 128.8, 129.0, 136.5,
144.6, 147.9, 158.5; EI-MS m/z: 259 (M+), 244, 230, 217, 202, 189, 121.
11-Phenyl-7,8,9,10-tetrahydro-6H-cyclohepta[b]quinoline (6)
Mp 109-110 °C (Lit.,16 105-107 °C). IR (KBr) : 3054, 2927, 2851, 1571, 1485, 1443, 1196, 762, 708
cm-1. 1H NMR (CDCl3, 400 MHz) : 1.61 (s, 2H), 1.86 (d, J = 2.4 Hz, 4H), 2.72 (t, J = 5.6 Hz, 2H), 3.38
(d, J = 3.6 Hz, 2H), 7.22-7.23 (m, 2H), 7.23-7.38 (m, 2H), 7.46-7.52 (m, 3H), 7.63 (t, J = 8.0 Hz, 1H),
8.22 (d, J = 8.4 Hz, 1H). 13C NMR (CDCl3, 100 MHz) : 26.7, 28.1, 30.5, 31.6, 38.9, 126.0, 126.3, 126.8,
127.2, 128.4, 128.8, 129.1, 134.1, 136.9, 143.9, 146.9, 164.1. EI-MS m/z: 273 (M+), 272, 258, 244, 231,
230.
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