Indium trichloride-catalyzed imino Diels-Alder reactions: Synthesis of new indolylquinoline derivatives

Article abstract of DOI:10.1055/s-2000-6387

Imino Diels-Alder reaction of N-arylaldimines with cyclopentadiene, 3,4- dihydro-2H-pyran and indene is efficiently catalyzed by indium trichloride to give new indolylquinoline derivatives in good yields.

Full text of DOI:10.1055/s-2000-6387

PAPER
661
Indium Trichloride-Catalyzed Imino Diels-Alder Reactions: Synthesis of New
Indolylquinoline Derivatives
Govindarajulu Babu, Rajagopal Nagarajan, Ramalingam Natarajan, Paramasivan T. Perumal*
Organic Chemistry Division, Central Leather Research Institute, Adyar, Chennai 600020, India
Fax +91(44)4911589; E-mail; ptperumal@hotmail.com
Received 6 September 1999; revised 30 December 1999
Abstract: Imino Diels-Alder reaction of N-arylaldimines with cy-
clopentadiene, 3,4-dihydro-2H-pyran and indene is efficiently cata-
lyzed by indium trichloride to give new indolylquinoline
derivatives in good yields.
Key words: catalysts, Diels-Alder reactions, indium trichloride,
imines, quinolines, heterocycles
The Diels-Alder reaction of imines is a powerful method
for the construction of nitrogen heterocycles such as quin-
oline and pyridine derivatives.1,2 Lewis acids such as
BF3·OEt2,3 lanthanide triflates4 and TFA5 catalyzes the
[4+2] cycloaddition of N-arylaldimines. Recently, we
have found that indium trichloride is an efficient catalyst
for the synthesis of quinoline and azabicycloalkanone de-
rivatives by imino Diels-Alder reactions.6-8 Literature
survey reveals that indium trichloride also catalyzes the
rearrangement of epoxides,9 reductive Friedel-Crafts
alkylation,10 Prins reaction,11 and Mukaiyama aldol reac-
tions.12
In continuation of our research in imino Diels-Alder re-
actions for the synthesis of quinoline derivatives, we en-
visaged the synthesis of indolylquinoline derivatives.
Compounds containing either the indole or the quinoline
moiety possess wide range of biological activity. Few re-
ports are available regarding compounds bearing both the
indole and quinoline moiety13-16 which possess a broad
spectrum of biological activity. In this paper, we describe
the convergent synthesis of new quinoline derivatives by
Scheme 1
imino Diels-Alder reactions catalyzed by indium trichlo-
ride.
range of biological activities which includes psychotropic
In the presence of 20 mol% indium trichloride, N-arylald- activity,19 antiallergic activity,20 antiinflammatory activi-
imine 1a was treated with cyclopentadiene in acetonitrile ty,21 estrogenic activity22 and are used as potential phar-
at room temperature (Scheme 1). After 1 hour, the imino maceuticals.23 Few reports are available on their synthesis
Diels-Alder reaction had proceeded smoothly to afford by imino Diels-Alder reactions. Acetic acid24 and
the corresponding indolylquinoline derivative 2a in 83% BF3•OEt225 catalyze the Diels-Alder reaction of 3,4-dihy-
yield. N-Arylaldimines 1 having various substituents were
dro-2H-pyran (5) with N-benzylidene aniline (1g) to af-
reacted with cyclopentadiene in the presence of indium ford pyranoquinolines; however, the yields are very low.
trichloride catalyst to afford indolylquinolines 2 in good When we treated N-benzylidene aniline (1g) with 3,4-di-
yields (Table 1). The structures of the products were as- hydro-2H-pyran (5) in the presence of 20 mol% indium
certained by the single crystal X-ray analysis of 2a and trichloride, after 30 minutes the reaction afforded the di-
2c17a,b. When we treated N-benzylidene-1-naphthylamine astereomeric pyranoquinoline derivatives 6g and 7g in a
(3) with cyclopentadiene, benzo[h]cyclopentaquinoline 4 ratio of 41:59 in an overall yield of 80% (Scheme 2).26 N-
was obtained in 75% yield (Scheme 1).
Arylaldimines 1 having various substituents were reacted
with 3,4-dihydro-2H-pyran (5) to afford pyranoquinoline
derivatives in varying ratios (Table 2). The structures of
the products were assigned based on the coupling con-
Next, we planned to synthesise pyranoquinoline deriva-
tives. The pyranoquinoline moiety is present in many al-
kaloids.18 Pyranoquinoline derivatives possess a wide
Synthesis 2000, No. 5, 661–666 ISSN 0039-7881 © Thieme Stuttgart · New York

662
G. Babu et al.
PAPER
Table 1 Synthesis of Cyclopentaquinolines and Indenoquinolines Using 20 mol% InCl3
Product
Substituents
R2
Time (h)
Yield (%)a
mp (∞C)
Rf Value
R1
R3
2a
2b
2c
2d
2e
4
11g
11i
11j
11k
11l
12
H
H
H
Me
Me
-
H
H
H
H
H
H
Me
H
-
H
H
H
0.5
0.5
0.5
0.5
0.5
0.75
6
6
24
12
9 (reflux)
20
83
60
85
87
79
75
40
48
30
48
65
50
165-166
65-66
0.48
0.52
0.42
0.44
0.41
0.42
0.74
0.80
0.70
0.76
0.79
0.68
Me
Cl
H
Cl
-
H
Cl
OMe
Cl
H
159-160
93-95
72-73
b
-
134-135
145-146
113-114
138-139
146-147
202-203
H
Me
Me
-
H
Me
-
-
a All the compounds were recrystallised from EtOAc/petroleum ether.
b Isolated as dense liquid.
stants of the H-5 proton with the H-4a proton. From Table
2, it is evident that in the case of imines of 2,4- and 2,5-
substituted anilines, pyranoquinoline derivative 7 was ob-
tained as the major compound due to steric hindrance
caused by the methyl protons in the ortho position. In the
case of indole substituted imines, pyranoquinoline deriv-
ative 6 was obtained as major compound due to its bulky
nature, which tends to be in (E)-form while reacting with
3,4-dihydro-2H-pyran (5). N-Benzylidene-1-naphthyl-
amine (3) reacted with 3,4-dihydro-2H-pyran (5) to afford
the benzo[h]pyranoquinolines 8 and 9 in a ratio of 32:68
in an overall yield of 53% (Scheme 2).
Indenoquinoline derivatives also possess a wide range of
biological activities.27-30 Reaction of N-benzylidene
aniline (1g) with indene (10) in the presence of 20 mol%
indium trichloride gave the indenoquinoline 11g in 40%
Scheme 2
Table 2 Synthesis of Indolylpyranoquinolines and Phenylpyranoquinolines Using 20 mol % InCl3
Imine
Substituents
R2
Time (h)
Product Ratioa
Yield (%)
mp (∞C)
Rf
R1
R3
6 : 7
6
7
6
7
1a
1b
1c
1d
1f
1g
1h
1i
H
H
H
Me
H
H
H
H
H
H
Me
Cl
H
OMe
H
Me
Cl
OMe
Cl
H
-
H
H
H
Me
H
H
H
H
H
4
6
6
7
8
0.5
2
0.5
4
0.75
3
>99
71:29
>99
55:45
99
41:59
68:32
34:66
58:42
5:95
68
55
65
38
149-150
174-175
182-183
159-160
129-130
123-124
128-129
154-155
146-147
191-192
111-112
-
0.93
0.87
0.63
0.6
0.75
0.62
0.46
0.51
0.57
0.65
0.59
0.81f
-
0.67
-
0.47
-
0.47
0.39
0.31
0.43
0.59
0.49
0.59g
139-140
-
217-218
-
50
80 (25)b
70
94-95
d
-
50
122-123
d
1j
1k
1l
70 (54)c
46
-
Me
Me
-
H
Me
-
185-186
106-107
5:95
45
51
d,f
d,g
3
0.75
32:68e
-
-
a Isolated yield based on products after column chromatography and recrystallised from EtOAc/petroleum ether.
b Yield reported in the literature.25
c Yield reported in the literature.31
d Isolated as dense liquid.
e Product ratio 8:9.
f Product 8.
g Product 9.
Synthesis 2000, No. 5, 661–666 ISSN 0039-7881 © Thieme Stuttgart · New York

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Indium Trichloride-Catalyzed Imino Diels-Alder Reactions
663
Table 3 Spectral Data of Indolylcyclopentaquinolines, Indolylpyranoquinolines and Indolylindenoquinolines
Prod- IR (KBr)
1H NMR (CDCl3/TMS)
d, J (Hz)
13C NMR (CDCl3/TMS)
d
MS
m/z
ucta
n (cm−1)
2a
3409, 2949,
1480, 1401,
1385, 720
8.07-6.80 (m, 12 H), 6.72 (m, 1 H), 6.68 (d, 1 H, J = 147.3, 137.9, 135.3, 135.2, 134.1, 133.7, 426 (M+)
7.8), 5.83 (m, 1 H), 5.61 (m, 1 H), 4.86 (d, 1 H, J = 133.2, 132.6, 129.6, 127.2, 126.6,
2.6), 4.14 (d, 1 H, J = 8.1), 3.77 (br s, 1 H, NH), 3.22 126.5, 126.3, 125.1, 125.0, 124.0,
(m, 1 H), 2.60 (m, 1 H), 1.69 (m, 1 H)
123.2, 119.4, 119.1, 116.0, 113.9,
113.7, 50.7, 45.7, 43.2, 32.4
2b
2c
2d
2e
3400, 2950,
1450, 1380,
730
8.04-7.79 (m, 5 H), 7.26-7.24 (m, 5 H), 6.89 (s, 1 H), 142.7, 138.0, 135.3, 134.1, 133.7, 133.2, 440 (M+)
6.83 (d, 1 H, J = 7.8), 6.56 (d, 1 H, J = 8.0), 5.81 130.0, 129.9, 129.3, 129.2, 129.1, 128.7,
(br s, 1 H), 5.60 ( s, 1 H), 4.85 (d, 1 H, J = 10.9), 4.09 127.2, 127.0, 126.7, 125.3, 125.0,
(d, 1 H, J = 8.4), 3.65 (br s, 1 H, NH), 3.10 (m, 1 H), 123.2, 122.3, 119.4, 113.9, 50.9, 45.8,
2.53 (m, 1 H), 2.27 (s, 3 H), 1.62 (m, 1 H)
43.1, 32.0, 20.5
3425, 3100,
2900, 1450,
1380, 750
8.03-7.85 (m, 5 H), 7.60-7.21 (m, 5 H ),7.02 (s, 1 H), 143.8, 137.9, 135.5, 134.5, 133.9, 132.6, 462 (M+ + 2),
6.92 (d, 1 H, J = 6.3), 6.56 (d, 1 H, J = 8.5), 5.75 (s, 130.4, 129.8, 127.9, 127.6, 126.4,
460 (M+)
1 H), 5.61 (m, 1 H), 4.80 (d, 1 H, J = 2.6), 4.06 (d, 125.6, 124.8, 123.9, 123.7, 122.1,
1 H, J = 8.5), 3.77 ( s, 1 H ), 3.09 (m, 1 H), 2.48 (m, 120.6, 120.1, 117.9, 114.9, 112.9, 51.4,
1 H), 1.61 (m, 1 H) 49.9, 43.6, 32.2
3459, 3110,
2910, 1460,
1381,754
8.05-7.89 (m, 3 H), 7.72-7.65 (m, 8 H), 6.84 (d, 1 H, 144.6, 138.0, 135.4, 134.2, 133.7, 132.4, 454 (M+)
J = 7.5), 6.59 (d, 1 H, J = 7.4), 5.79 (m, 1 H), 5.62 (m, 130.3, 129.3, 129.2, 127.4, 126.7,
1 H), 4.70 (s, 1 H ), 4.26 (d, 1 H, J = 8.7), 3.63 (br s, 125.3, 125.1, 124.5, 123.3, 123.1,
1 H, NH), 2.72 (m, 1 H), 2.34 (s, 3 H), 2.14 (s, 3 H), 122.2, 120.9, 120.5, 119.4, 114.0, 51.6,
1.77 (m, 1 H)
45.1, 43.3, 32.8, 19.5, 17.0
3400, 2900,
1475,1380,
720
8.04-7.86 (m, 3 H), 7.65-7.23 (m, 7 H), 6.92 (s, 1 H), 141.9,137.9,135.3,133.9,133.8,130.2,
463 (M+ + 2), 461
6.87 (s, 1 H), 5.76 (s, 1 H), 5.60 (s, 1 H), 4.81 (d, 1 H, 129.2, 129.0, 127.2, 127.1, 126.6, 126.2, (M+)
J = 2.4), 4.10 (d, 1 H, J = 8.2), 3.64 ( s, 1 H), 3.12 (m, 125.2, 125.0, 124.6, 123.3, 123.1,
1 H ), 2.53 (m, 1 H), 2.42 (s, 3 H), 1.61 (m, 1 H)
122.3, 119.4, 114.0, 50.7, 45.9, 43.0,
32.0, 17.0
4
3392,1485
7.90-7.32 (m, 11 H), 6.08 (m, 1 H), 5.79 (m, 1 H),
143.2, 139.9, 134.1, 132.7, 130.7, 128.7, 297 (M+)
4.83 (d, 1 H, J = 2.4), 4.59 (br s, 1 H, NH), 4.39 (d, 1 127.5, 126.8, 126.7,125.2, 125.1, 123.8,
H, J = 8.2), 3.25 (m, 1 H), 2.91 (m, 1 H), 2.04 (m, 1 H) 120.3, 119.7, 118.9, 58.3, 47.1, 46.2,
31.5
6a
3457, 3395,
2929, 1608
8.04 (d, 1 H, J = 8.3), 7.90 (d, 1 H, J = 7.6), 7.62-7.11 144.8, 138.1, 135.5, 133.8, 132.0, 129.3, 444 (M+)
(m, 10 H), 6.84 (d, 1 H, J = 7.4), 6.64 (d, 1 H, J = 7.9), 128.9, 128.2, 127.7, 126.8, 126.1,
5.34 (d, 1 H, J = 5.3), 4.93 (s, 1 H), 3.86 (br s, 1 H, 125.1, 123.4, 123.3, 123.1, 120.2, 119.6,
NH), 3.60 (m, 1 H), 3.41 (d, 1 H, J = 2.8), 2.27 (m, 1 118.2, 114.6, 114.0, 72.0, 60.5, 52.2,
H), 1.56-1.11 (m, 4 H)
36.4, 25.3, 18.5
6b
3405, 3119,
2929, 1362,
717
8.04 (d, 1 H, J = 8.3), 7.91 (d, 1 H, J = 7.5), 7.90-7.04 142.5, 138.1, 135.5, 133.8, 129.7,
(m, 9 H), 6.91 (d, 1 H, J = 8.0), 6.57 (d, 1 H, J = 8.1), 129.2, 128.9, 128.8, 128.0, 127.8,
5.29 (d, 1 H, J = 5.4), 4.88 (s, 1 H), 3.61 (m, 3 H), 2.20 127.1, 126.9,126.7, 125.1, 123.3, 123.2,
458 (M+)
(s, 4 H), 1.54-1.12 (m, 4 H)
120.1, 119.5, 114.7, 113.2, 72.3, 60.6,
52.3, 36.6, 25.3, 20.6, 18.5
7b
6c
3451, 3380,
2929, 1362,
716
8.60-7.05 (m, 11 H), 6.92 (d, 1 H, J = 8.0), 6.45 (d, 1 137.1, 135.6, 135.2, 134.8, 133.0, 131.1, 458 (M+)
H, J = 8.1), 4.95 (d, 1 H, J = 10.1), 4.35 ( d, 1 H, J = 130.1, 129.7, 129.2, 128.0, 127.3, 126.7,
2.4), 4.09 (m, 2 H), 3.72 (m, 1 H), 2.23 (s, 4 H), 2.03- 125.0, 124.1, 123.2, 114.4, 113.9, 111.0,
1.24 (m, 4 H)
74.4, 68.5, 48.2, 37.0, 24.3, 21.8, 20.2
3452, 3385,
2924, 1383,
804
8.03 (d, 1 H, J = 8.2), 7.91 (d, 1 H, J = 7.5), 7.60 (s, 1 144.0, 138.1, 134.2, 133.9, 133.1,
H ), 7.53-7.32 (m, 8 H), 7.27 (d, 1 H, J = 1.9), 6.57 129.4, 129.2, 129.0, 128.1, 127.3,
(d, 1 H, J = 8.4), 5.27 (d, 1 H, J = 5.4), 4.90 (s, 1 H), 126.7, 125.2, 123.4, 123.2, 122.6,
3.82 (br s, 1 H, NH), 3.62-3.43 (m, 2 H ), 2.31 (br s, 119.5, 115.9, 115.3, 114.0, 113.2, 71.9,
480 (M+ + 2), 478
(M+)
1 H) , 1.54-1.23 (m, 4 H)
60.7, 52.2, 36.1, 25.2, 18.5
6d
3454, 3379,
2929, 1368,
717
8.05−7.11 (m, 10 H ), 6.94 (d, 1 H, J = 7.1), 6.57 (d, 1 143.9, 138.1, 137.3, 135.4, 133.7,
H, J = 7.2), 5.41 (d, 1 H, J = 5.1), 4.84 (s, 1 H), 3.65 129.4, 129.1, 127.0, 126.7, 126.3,
(br s, 1 H, NH), 3.51 (d, 1 H, J = 10.2), 3.23 (m, 1 H), 125.1, 124.4, 123.5, 123.0, 120.9,
472 (M+)
2.38 (s, 4 H ), 2.14 (s, 3 H ),1.77−1.26 (m, 4 H)
119.6, 119.4, 118.6, 113.9, 113.2, 72.1,
60.7, 52.0, 36.6, 30.1, 24.4, 21.5, 18.3
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Table 3 (continued)
Prod- IR (KBr)
1H NMR (CDCl3/TMS)
d, J (Hz)
13C NMR (CDCl3/TMS)
d
MS
m/z
ucta
n (cm−1)
7b
3451, 3380,
2929, 1362,
716
8.60-7.05 (m, 11 H), 6.92 (d, 1 H, J = 8.0), 6.45 (d, 137.1, 135.6, 135.2, 134.8, 133.0, 131.1, 458 (M+)
1 H, J = 8.1), 4.95 (d, 1 H, J = 10.1), 4.35 ( d, 1 H, J 130.1, 129.7, 129.2, 128.0, 127.3, 126.7,
= 2.4), 4.09 (m, 2 H), 3.72 (m, 1 H), 2.23 (s, 4 H),
125.0, 124.1, 123.2, 114.4, 113.9, 111.0,
74.4, 68.5, 48.2, 37.0, 24.3, 21.8, 20.2
2.03-1.24 (m, 4 H)
6c
6d
7d
6f
3452, 3385,
2924, 1383,
804
8.03 (d, 1 H, J = 8.2), 7.91 (d, 1 H, J = 7.5), 7.60 (s, 1 144.0, 138.1, 134.2, 133.9, 133.1,
H ), 7.53-7.32 (m, 8 H), 7.27 (d, 1 H, J = 1.9), 6.57 129.4, 129.2, 129.0, 128.1, 127.3,
(d, 1 H, J = 8.4), 5.27 (d, 1 H, J = 5.4), 4.90 (s, 1 H), 126.7, 125.2, 123.4, 123.2, 122.6,
3.82 (br s, 1 H, NH), 3.62-3.43 (m, 2 H ), 2.31 (br s, 119.5, 115.9, 115.3, 114.0, 113.2, 71.9,
480 (M+ + 2), 478
(M+)
1 H) , 1.54-1.23 (m, 4 H)
60.7, 52.2, 36.1, 25.2, 18.5
3454, 3379,
2929, 1368,
717
8.05-7.11 (m, 10 H ), 6.94 (d, 1 H, J = 7.1), 6.57 (d, 143.9, 138.1, 137.3, 135.4, 133.7,
1 H, J = 7.2), 5.41 (d, 1 H, J = 5.1), 4.84 (s, 1 H), 3.65 129.4, 129.1, 127.0, 126.7, 126.3,
(br s, 1 H, NH), 3.51 (d, 1 H, J = 10.2), 3.23 (m, 1 H), 125.1, 124.4, 123.5, 123.0, 120.9,
472 (M+)
472 (M+)
2.38 (s, 4 H ), 2.14 (s, 3 H ),1.77-1.26 (m, 4 H)
119.6,119.4, 118.6, 113.9, 113.2, 72.1,
60.7, 52.0, 36.6, 30.1, 24.4, 21.5, 18.3
3459, 3380,
2929, 1379,
715
8.05 (d, 1 H , J = 8.4), 8.02-7.18 (m, 9 H ), 6.87 (d, 1 142.5, 138.1, 136.5, 134.7, 133.8,
H, J = 7.2), 6.52 (d, 1 H, J = 7.3), 5.12 (d, 1 H, J = 129.9, 129.2, 127.1, 126.9, 126.4,
10.3), 4.92 (s, 1 H), 3.71 (br s, 1 H, NH), 3.56 (d, 1 H, 125.0, 124.6, 123.5, 123.2, 122.6,
J = 10.3), 3.24 (m, 1 H ), 2.33 (s, 4 H ), 1.95 (s, 3 H), 121.3, 119.1, 118.7, 114.0, 113.2, 72.1,
1.82-1.24 (m, 4 H)
68.7, 47.3, 37.2, 29.7, 21.8, 18.1, 17.1
3436, 3385,
2934, 1368,
753
8.22 (m, 1 H ), 8.03-7.03 (m, 10 H ), 6.71 (d, 1 H, J = 153.2, 138.7, 138.1, 136.1, 135.5, 134.7, 474 (M+)
2.7), 6.61 (d, 1 H, J = 8.6), 5.32 (d, 1 H, J = 5.5), 4.86 133.8, 129.7, 129.2, 127.1, 126.7,
(s, 1 H), 3.77 (br s, 4 H), 3.55 (m, 2 H ), 2.34 (br s, 1 125.1,123.4, 123.2, 122.6, 121.4, 119.6,
H) ,1.57-1.24 (m, 4 H)
116.0, 115.1, 113.2, 72.4, 60.7, 55.8,
52.4, 36.6, 25.2, 18.4
265 (M+)
265 (M+)
279 (M+)
279 (M+)
6g
7g
6h
7h
3378, 3316,
2936, 1605,
1485, 1071
7.41-7.24 (m, 6 H), 7.13 (m, 1 H), 6.83 (m, 1 H), 6.62 145.2, 141.1, 128.3, 128.0, 127.6, 127.5,
(d, 1 H, J = 7.6), 5.34 (d, 1 H, J = 4.5), 4.68 (br s, 1 H), 126.8, 119.8, 118.3, 114.4, 72.8, 60.6,
3.89 (br s, 1 H, NH), 3.61 (d, 1 H, J = 11.2), 3.44 (m, 59.3, 38.9, 25.4, 18.0
1 H), 2.17 (m, 1 H), 1.75-1.31 (m, 4 H)
3374, 2928,
1610, 1489,
1077
7.43-7.34 (m, 5 H), 7.26 (d, 1 H, J = 7.0), 7.13 (m, 1 144.1, 141.7, 130.2, 128.7, 128.0,
H), 6.75 (m, 1 H), 6.54 (d, 1 H, J = 7.8), 4.74 (d, 1 H, 127.2, 127.1, 120.0, 116.8, 113.5, 73.9,
J = 10.6), 4.41 (br s, 1 H), 4.10 (m, 2 H), 3.78 (m, 1 68.0, 54.1, 38.2, 23.5, 21.4
H), 2.08 (m, 1 H), 1.89-1.31 (m, 4 H)
3387, 2940,
1512, 1019
7.48-7.26 (m, 6 H), 6.94 (d, 1 H, J = 7.6), 6.55 (d, 1 142.7, 141.2, 128.6, 128.2, 127.6, 127.4,
H, J = 7.8), 5.32 (d, 1 H, J = 4.2), 4.64 (br s, 1 H), 3.77 127,3, 126.7, 119,7, 114.4, 72.7, 60.5,
(br s, 1 H, NH), 3.62 (d, 1 H, J = 11.3 Hz), 3.48 (m, 1 59.3, 38.9, 25.2, 20.5, 17.8
H), 2.29 (s, 3 H), 2.16 (m, 1 H), 1.63-1.30 (m, 4 H)
3367, 2927,
1509, 1261,
1086
7.48-7.24 (m, 5 H), 7.04 (s, 1 H), 6.92 (d, 1 H, J =
142.2, 131.5, 130.6, 128.9, 127.7, 126.9,
7.4), 6.46 (d, 1 H, J = 7.8), 4.70 (d, 1 H, J = 10.7), 4.35 126.3, 120.4, 114.8, 113.9, 74.0, 68.4,
(s, 1 H), 4.11 (d, 1 H, J = 10.5), 3.96 (br s, 1 H, NH), 54.9, 39.4, 24.0, 21.5, 19.4
3.75 (m, 1 H), 2.23 (s, 3 H), 2.08 (m, 1 H), 1.90-1.30
(m, 4 H)
301(M+ + 2),
299 (M+)
7i
6j
7j
3348, 2934,
1494, 1265
7.37 (m, 5 H), 7.19 (s, 1 H), 7.03 (d, 1 H, J = 8.2), 6.45 143.2, 141.8, 130.3, 129.1, 128.6, 127.9,
(d, 1 H, J = 8.3), 4.67 (d, 1 H, J = 10.5), 4.33 (s, 1 H), 127.6, 121.8, 121.7, 115.2, 73.8, 68.4,
4.08 (m, 2 H), 3.73 (m, 1 H), 2.05 (m, 1 H), 1.83-1.31 54.8, 38.6, 23.9, 22.0
(m, 4 H)
295 (M+)
295 (M+)
3295, 2942,
1502, 1262,
1065
7.40-7.29 (m, 5 H), 7.03 (s, 1 H), 6.73 (d, 1 H, J =
152.8, 141.3, 139,1, 128.3, 127.4, 126.8,
8.2), 6.57 (d, 1 H, J = 8.4), 5.31 (d, 1 H, J = 5.4), 4.61 121.1, 115.7, 115.0, 111.8, 72.9, 60.8,
(s, 1 H), 3.73 (s, 3 H), 3.67 (br s, 1 H), 3.61-3.36 (m, 59.5, 55.8, 39.1, 25.3, 17.9
2 H), 2.15 (m, 1 H), 1.54-1.26 (m, 4 H)
3361, 2938,
1504, 1255,
1032
7.43-7.27 (m, 5 H), 6.82 (s, 1 H), 6.75 (d, 1 H, J =
151.9, 142.2, 138.7, 128.1, 127.7, 121.3,
9.1), 6.49 (d, 1 H, J = 8.5), 4.62 (d, 1 H, J = 10.5), 4.38 116.7, 115.5, 114.7, 74.5, 68.3, 55.7,
(s, 1 H), 4.10 (m, 1 H), 3.75 (m, 5 H), 2.10 (m, 1 H), 55.1, 38.8, 24.0, 21.9
1.84-1.30 (m, 4 H)
Synthesis 2000, No. 5, 661–666 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Indium Trichloride-Catalyzed Imino Diels-Alder Reactions
665
Table 3 (continued)
Prod- IR (KBr)
1H NMR (CDCl3/TMS)
d, J (Hz)
13C NMR (CDCl3/TMS)
d
MS
m/z
ucta
n (cm−1)
6k
3384, 2936,
1493, 1263
7.45 (m, 5 H), 7.04 (s, 1 H), 6.98 (s, 1 H), 5.25 (s,
143.6, 140.5, 128.8, 127.7, 127.2, 126.9, 315 (M+ + 2),
1 H), 4.64 (s, 1 H), 3.79 (br s, 1 H, NH), 3.62 (m, 1 H), 126.5, 126.0, 122.1, 115.4, 73.1, 60.5, 313 (M+)
3.44 (m, 1 H), 2.12 (br s, 4 H), 1.80-1.31 (m, 4 H)
59.4, 39.1, 37.8, 25.2, 16.8
7k
6l
7l
8
3395, 2846,
1481, 1052
7.44-7.34 (m, 5 H), 7.10 (d, 1 H, J = 1.8), 6.97 (s,
141.7, 140.9, 129.4, 128.3, 128.0, 127.6, 315 (M+ + 2),
1 H), 4.73 (d, 1 H, J = 10.7), 4.34 (d, 1 H, J = 2.4), 4.11 127.3, 122.5, 120.8, 120.7, 73.8, 68.1, 313 (M+)
(d, 1 H, J = 8 .9), 3.88 (br s, 1 H, NH), 3.74 (m, 1 H), 54.4, 38.1, 23.5, 21.5, 16.6
2.11 (br s, 4 H), 1.90-1.32 (m, 4 H)
3384, 2940,
1510, 1023
7.50 (m, 5 H), 6.92 (d, 1 H, J = 7.0), 6.51 (d, 1 H, J = 142.6, 141.4, 128.7, 128.3, 127.7, 127.4, 293 (M+)
7.1), 5.31 (s, 1 H), 4.64 (s, 1 H), 3.76 (br s, 1 H, NH), 127.3, 126.8, 119.7, 114.4, 71.7, 60.6,
3.63 (d, 1 H, J = 11.2), 3.48 (m, 1 H), 2.35 (s, 3 H), 59.4, 38.9, 25.3, 20.6, 17.8, 16.8
2.06 (br s, 4 H), 1.84-1.27 (m, 4 H)
3382, 2942,
1508, 1022
7.49-7.37 (m, 5 H), 6.91 (d, 1 H, J = 6.9), 6.52 (d,
142.6, 142.5, 136.2, 129.7, 128.5, 127.8, 293 (M+)
1 H, J = 7.0), 4.76 (d, 1 H, J = 11.2), 4.50 (s, 1 H), 4.14 127.7, 118.8, 118.5, 118.3, 72.2, 68.6,
(d, 1 H, J = 10.3), 3.85 (br s, 1 H, NH), 3.73 (m, 1 H), 54.0, 39.4, 24.0, 21.8, 17.9, 16.9
2.35 (s, 3 H), 2.08 (br s, 4 H), 1.93-1.27 (m, 4 H)
3385, 2925,
1406, 1075
7.88-7.23 (m, 11 H), 5.50 (d, 1 H J = 5.5), 4.79 (s,
1 H), 4.50 (br s, 1 H), 3.62 (m, 1 H), 3.38 (m, 1 H),
2.26 (m, 1 H), 1.84-1.34 (m, 4 H)
141.2, 136.2, 134.4, 133.6, 129.7, 128.8, 315 (M+)
128.3, 127.6, 126.9, 125.3, 122.8, 119.9,
118.1, 114.3, 72.8, 60.8, 59.5, 38.4,
25.3, 18.0
9
3413, 2937,
1721, 1494,
1216
7.76-7.21 (m, 11 H), 4.85 (d, 1 H, J = 10.7), 4.50 (s, 142.2, 139.8, 134.3, 129.1, 128.1, 127.8, 315 (M+)
1 H), 4.14 (d, 1 H, J = 10.1), 3.76 (m, 1 H), 3.50 (m, 127.4, 125.3, 124.0, 122.5, 119.7, 117.9,
1 H), 2.20 (m, 1 H), 1.90-1.34 (m, 4 H)
116.5, 114.6, 74.7, 68.6, 55.2, 38.7,
25.4, 24.1
11g
3402, 1497
7.54-6.98 (m, 11 H), 6.76 (d, 1 H, J = 6.8), 6.62 (d, 146.2, 145.1, 142.8, 142.5, 129.4, 128.5, 297 (M+)
1 H, J = 6.59), 4.76 (br s, 1 H), 4.59 (d, 1 H, J = 7.1), 127.4, 126.8, 126.7, 126.5, 126.2, 124.9,
3.91 (br s, 1 H, NH), 3.38-3.18 (m, 2 H), 2.43 (m,
1 H)
124.8, 123.7, 118.8, 115.5, 57.4, 48.1,
46.1, 31.0
11i
11j
3381, 3032,
1499, 1308
7.51-7.09 (m, 10 H), 6.95 (d, 1 H, J = 7.9), 6.52 (d, 145.5, 143.7, 142.7, 142.1, 129.0, 128.6, 333 (M+ + 2),
1 H, J = 8.1), 4.71 (br s, 1 H), 4.51 (d, 1 H, J = 6.7), 127.5, 127.1, 126.6, 126.5, 125.2, 124.8, 331 (M+)
3.92 (br s, 1 H), 3.34-3.14 (m, 2 H), 2.42 (m, 1 H)
123.1, 116.6, 57.4, 47.8, 46.0, 30.9
3398, 2947,
1515, 1160
7.55-6.52 (m, 12 H), 4.67 (s, 1 H), 4.56 (d, 1 H, J = 152.6, 146.1, 143.0, 142.7, 139.1, 128.5, 327 (M+)
7.8), 3.86 (s, 1 H), 3.72 (s, 3 H), 3.35-3.12 (m, 2 H), 128.3, 127.8, 126.9, 126.3, 125.2, 124.8,
2.42 (m, 1 H)
124.0, 116.3, 115.4, 113.2, 57.8, 55.6,
48.1, 46.5, 30.9
11k
11l
12
3387, 2950
7.55-6.86 (m, 11 H), 4.72 (s, 1 H), 4.54 (d, 1 H, J = 145.8, 142.7, 142.4, 141.8, 129.0, 128.8, 347 (M+ + 2),
7.0), 3.80 (br s, 1 H, NH), 3.33-3.14 (m, 2 H), 2.42 128.5, 127.6, 127.5, 127.1, 126.5, 124.9, 345 (M+)
(m, 1 H), 2.11 (s, 3 H)
124.6, 124.0, 122.3, 120.3, 57.3, 47.8,
46.2, 30.9, 17.2
3385, 2930,
1495
7.42-6.71 (m, 11 H), 4.92 (d, 1 H, J = 6.0), 4.45 (d, 145.8, 145.4, 143.2, 142.5, 134.3, 128.8, 325 (M+)
1 H, J = 4.2), 3.87 (br s, 1 H), 3.43-3.12 (m, 2 H), 2.85 128.5, 127.5, 127.1, 126.2, 125.6, 124.8,
(m, 1 H), 2.62 (s, 3 H), 2.15 (s, 3 H)
123.7, 123.3, 121.4, 119.7, 60.2, 46.6,
45.1, 33.8, 17.5, 16.1
347 (M+)
3414, 3065,
1577
7.80-7.08 (m, 15 H), 4.85 (s, 1 H), 4.75 (d, 1 H, J = 146.2, 142.9, 142.7, 139.4, 132.6, 128.6,
7.2), 4.71 (br s, 1 H, NH), 3.47 (m, 2 H), 2.50 (m,
1 H)
128.5, 127.5, 127.3, 126.9, 126.7, 126.1,
125.2, 125.1, 125.0, 124.9, 122.2, 119.6,
118.5, 117.6, 57.7, 48.1, 46.8, 30.9
a Satisfactory microanalyses obtained: C 0.45; H 0.04; N 0.03.
Synthesis 2000, No. 5, 661–666 ISSN 0039-7881 © Thieme Stuttgart · New York

666
G. Babu et al.
PAPER
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yield (Scheme 1). Table 1 summarizes the results of reac-
tion of indene with N-arylaldimines 1 having various sub-
stituents. Benzo[h]indenoquinoline 12 was obtained in
50% yield when N-benzylidene-1-naphthylamine (3) was
treated with indene in the presence of indium trichloride.
In summary, the results demonstrated here reveal the wide
utility of indium trichloride in the imino Diels-Alder re-
action of N-arylaldimines to synthesise new quinoline de-
rivatives.
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Mass spectra were recorded on Varian VG 70-70H mass spectro-
meter. Melting points were measured in capillary tubes and are un-
corrected. Analytical TLC was performed on precoated sheets of
silica gel G of 0.25 mm thickness containing PF 254 indicator (Mer-
ck, Darmstadt). Column chromatography was performed with silica
gel (60-120 mesh; SD Fine, Boisar). IR spectra were recorded as
solids in KBr pellets on a Nicolet Impact-400 spectrometer. NMR
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Shanmugasundararaj, S.; Hoong-Kun Fun.; Babu, G.;
Perumal, P. T. Acta Cryst. C55 in press.
(b) Sankaranarayanan, R.; Velmurugan, D.;
1
spectra were obtained on a Bruker spectrometer. H NMR spectra
Shanmugasundararaj, S.; Hoong-Kun Fun; Babu, G.;
Perumal, P. T. Acta Cryst C, communicated.
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were recorded at 300 MHz in CDCl3 and the chemical shifts are giv-
en in d relative to the internal standard TMS. 13C NMR spectra were
recorded at 75 MHz in CDCl3 and the chemical shift was given in d
relative to the solvent (77.0). MeCN was distilled from CaH2 and
dried over 4 Å molecular sieves.
IndiumTrichloride-Catalyzed Diels-Alder Reaction of Imines
1a-l or 3 with Dienenophile; General Procedure
A mixture of imine 1 or 3 (2.5 mmol), InCl3 (0.110 g, 20 mol%),
dienenophiles [cyclopentadiene (5 mmol) or 3,4-dihydro-2H-pyran
(5 mmol) or indene (2.5 mmol)] in MeCN (7 mL) was stirred at r.t.
for the appropriate time. To the reaction mixture was added aq satd
NaHCO3 solution (5 mL) and the solution was extracted with CHCl3
(3 × 10 mL). The combined organic layers were washed with H2O,
brine, dried (Na2SO4), filtered, and the solvent evaporated. The res-
idue was purified by column chromatography eluting with 90:10
EtOAc/petroleum ether (bp 60-80°C) to afford the cycloadducts.
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Acknowledgement
We thank the Council of Scientific and Industrial Research, New
Delhi for financial support.
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Article Identifier:
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Synthesis 2000, No. 5, 661–666 ISSN 0039-7881 © Thieme Stuttgart · New York