J. Bergman et al. / Tetrahedron 56 (2000) 1911–1916
1915
2
2
H), 7.13 (app. t, J7.2 Hz, 2H), 7.02 (app. t, J7.2 Hz,
6H), 6.68 (d, J7.8 Hz, 1H), 5.84 (s, 2H), 5.77 (s, 1H),
13
H), 6.78 (s, 2H).
3.38–3.31 (m, 2H), 3.11–3.03 (m, 2H); C NMR d 146.8
s), 144.8 (s), 141.8 (s), 135.4 (s), 134.4 (s), 128.3 (s), 120.2
(
0
Cyclohept[1,2-b:5,4-b ]bisindole (15). Triethyl ortho-
formate (190 ml, 1.14 mmol) was added to a solution of
(d), 119.9 (d), 118.3 (d), 118.0 (d), 112.4 (s), 110.5 (d),
107.8 (d), 107.6 (d), 100.5 (t), 37.7 (d), 25.5 (t).
1,2-bis(1H-indol-2-yl)ethane (9) (260 mg, 1 mmol) in
TFA (8 ml); the resulting deep red mixture was stirred at
rt for 24 h. The solvent was removed at reduced pressure
and the residue was dissolved in ethanol (15 ml), followed
by addition of sodium borohydride (228 mg, 6 mmol) in
portions during 5 min. Heating at reflux for 15 min gave a
clear yellow solution, which was thereafter allowed to cool
and diluted with water (15 ml), whereupon a whitish pre-
cipitate formed. After filtration, washing with water and
drying, 15 (240 mg, 88%) was obtained as a cream coloured
solid, mp 230ЊC (dec.). This material is sensitive towards
oxidation and slowly turns pink on standing if not stored in a
evacuated desiccator. IR (KBr) 3388, 2906 (w), 2800 (w),
Reaction of 1,2-bis(1H-indol-2-yl)ethane (9) with acetone
A mixture of 1,2-bis(1H-indol-2-yl)ethane (9) (130 mg,
0.5 mmol) and TFA (58 ml, 0.75 mmol) in acetone (5 ml)
was stirred at rt for 24 h. Et O (20 ml) was added, followed
2
by washing with sat. aq. NaHCO (3×10 ml), drying over
3
MgSO and evaporation of the solvent. After chromato-
4
graphy (CH Cl ), the product 19 was isolated as a pale
2
2
yellowish solid (120 mg, 80%); mp 275–277ЊC (dec.). IR
(KBr) 3403, 2932 (w), 1459, 1428, 1334, 1184, 1076,
Ϫ1
1
746 cm ; H NMR (DMSO-d ) d 10.71 (s, 2H), 7.80 (d,
6
J7.7 Hz, 2H), 7.28 (d, J7.5 Hz, 2H), 7.04–6.92 (m, 4H),
Ϫ1
1
13
1
461, 1450, 1420, 1324, 1179, 1006, 743 cm ; H NMR
3.08 (s, 4H), 2.00 (s, 6H); C NMR (DMSO-d ) d 135.2 (s),
6
(
DMSO-d ) d 10.76 (s, 2H), 7.56 (d, J7.5 Hz, 2H), 7.29
134.0 (s), 127.5 (s), 121.0 (d), 119.7 (d), 118.6 (s), 117.8 (d),
6
ϩ
(
3
dd, J6.8, 1.7 Hz, 2H), 7.06–6.97 (m, 4H), 4.16 (s, 2H),
110.8 (d), 37.5 (s), 31.0 (q), 27.1 (t); MS (EI) m/z 300 (M ,
1
3
.14 (s, 4H); C NMR (DMSO-d ) d 135.7 (s), 134.3 (s),
15), 286 (17), 285 (79), 283 (18), 269 (20), 256 (12), 170
(81), 168 (21), 155 (19), 154 (29), 130 (100), 128 (35), 115
(21), 103 (18), 77 (32). HRMS (EI) m/z Calcd for C H N
6
28.7 (s), 120.2 (d), 118.1 (d), 117.3 (d), 110.4 (d), 107.7
ϩ
21
20
2
2
69 (23), 256 (17), 154 (9), 130 (10). HRMS (EI) m/z Calcd
300.1626; found 300.1635.
for C H N 272.1313; found 272.1295.
1
9
16
2
Reaction of bisphenylhydrazone 21 with PCl3
Reaction of 1,2-bis(1H-indol-2-yl)ethane (9) with
-nitrobenzaldehyde
4
To bisphenylhydrazone 21 (2.92 g, 10 mmol) suspended in
toluene (40 ml), was added PCl (2.75 g, 20 mmol) drop-
wise at rt. The mixture was thereafter heated at reflux for
3
A mixture of 1,2-bis(1H-indol-2-yl)ethane (9) (130 mg,
.5 mmol) and 4-nitrobenzaldehyde (81 mg, 0.54 mmol)
was heated at reflux in EtOH (5 ml) containing TFA (3
0
6
h. After cooling, the mixture was diluted with acetone
(250 ml) and filtered. The filtrate was immediately evapo-
drops) for 3.5 h. After cooling, the solvent was evaporated
rated with silica gel whereupon flash chromatography
(hexane–EtOAc, 2:1) took place to yield indolo[2,3-c]-
carbazole (8) (210 mg, 8%). The spectral data of this
and the residue subjected to chromatography (CH Cl ) to
2
2
yield 17 (169 mg, 86%) as a yellowish solid; mp 272–273ЊC
10
(
1
dec.). IR (KBr) 3399, 3052 (w), 2915 (w), 1592, 1518,
material were identical with those previously reported.
Ϫ1
1
461, 1346, 744 cm ; H NMR (DMSO-d ) d 10.96 (s,
6
2
H), 8.02 (d, J8.8 Hz, 2H), 7.69 (d, J8.8 Hz, 2H), 7.63
The insoluble material after the treatment with acetone was
suspended in EtOH (40 ml) and filtered. The filtrate was
diluted with water (600 ml) and the pH was adjusted to 9
by addition of NaOH. This operation gave a precipitate
which was collected by filtration, washed with water and
(
d, J7.5 Hz, 2H), 7.27 (d, J7.5 Hz, 2H), 7.01 (app. t,
J7.2 Hz, 2H), 6.95 (app. t, J7.3 Hz, 2H), 6.00 (s, 1H),
1
3
3
.40–3.30 (m, 2H), 3.16–3.06 (m, 2H); C NMR (DMSO-
d6) d 155.4 (s), 145.4 (s), 136.0 (s), 134.4 (s), 128.3 (d),
22
1
28.0 (d), 123.4 (d), 120.5 (d), 118.5 (d), 117.8 (d), 111.0
dried to yield 3-aminocarbazole (22) (780 mg, 43%).
ϩ
(s), 110.6 (d), 37.9 (d), 25.4 (t); MS (EI) m/z 393 (M , 18),
2
72 (21), 271 (100), 269 (23), 256 (10), 154 (10), 135 (28),
130 (7). HRMS (EI) m/z Calcd for C H N O 393.1477;
References
2
5
19
3
2
found 393.1479.
1
. For reviews see: (a) Gribble, G. W.; Berthel, S. J. In Studies in
Reaction of 1,2-bis(1H-indol-2-yl)ethane (9) with 3,4-
methylenedioxybenzaldehyde
Natural Product Chemistry; Atta-ur-Rahman, Ed.; Elsevier:
Amsterdam, 1993; Vol. 12, p 365. (b) Prudhomme, M. Curr.
Pharm. Des. 1997, 3, 265. (c) Pindur, U.; Kim, Y.-S.; Mehrabani,
F. Curr. Med. Chem. 1999, 6, 29.
1
,2-Bis(1H-indol-2-yl)ethane (9) (260 mg, 1 mmol) was
refluxed with 3,4-methylenedioxybenzaldehyde (155 mg,
.03 mmol) and p-toluenesulfonic acid (10 mg) in EtOH
15 ml) for 14 h. After cooling, the product 18 (210 mg)
2. (a) Kase, H.; Iwahashi, K.; Matsuda, Y. J. Antibiot. 1986, 39,
1059. (b) Elliot, L. H.; Wilkinson, S. E.; Sedgwick, A. D.; Hill,
C. H.; Lawton, G.; Davis, P. D.; Nixon, J. S. Biochem. Biophys.
Res. Commun. 1990, 171, 148. For a synthesis, see: Wood, J. L.;
Stoltz, B. M.; Dietrich, H.-J. J. Am. Chem. Soc. 1995, 117, 10413.
3. (a) Omura, S.; Iwai, Y.; Hirano, A.; Nakagawa, A.; Awaya, J.;
Tsuchiya, H.; Takahashi, Y.; Masuma, R. J. Antibiot. 1977, 30,
275. (b) Furusaki, A.; Hashiba, N.; Matsumoto, T.; Hirano, A.;
Iwai, Y.; Omura, S. J. Chem. Soc., Chem. Commun. 1978, 800.
(c) Nakano, H.; Kobayashi, E.; Takahashi, I.; Tamaoki, T.; Kuzuu,
1
(
was collected, washed with ethanol and dried. The mother
liquor was concentrated, and a second crop of 18 (45 mg)
was collected after trituration with Et O. Total yield 255 mg
2
(
3
7
65%). Whitish solid, mp 320–322ЊC (dec.). IR (KBr) 3408,
385, 2907 (w), 1498, 1482, 1459, 1436, 1243, 1037, 922,
Ϫ1 1
95, 744 cm ; H NMR (DMSO-d ) d 10.84 (s, 2H), 7.62
6
(d, J7.5 Hz, 2H), 7.27 (d, J7.6 Hz, 2H), 7.03–6.92 (m,