1450
J. Bergman et al. / Tetrahedron 58 12002) 1443±1452
1
1
1518, 1466, 1326, 1229, 1072, 740; H NMR 4DMSO-d6)
748; H NMR 4acetone-d6) d 8.26 41H, d, J8.7 Hz), 8.13
41H, d, J7.4 Hz), 7.99 41H, d, J8.2 Hz), 7.87 41H, d,
J7.8 Hz), 7.67 41H, dd, J7.4, 7.3 Hz), 7.53 41H, s),
7.47 41H, dd, J7.8, 7.4 Hz), 7.35±7.28 48H, m), 7.24±
7.20 42H, m), 7.16±7.13 42H, m), 7.10±7.09 42H, m),
6.87±6.85 42H, m), 5.67 41H, d, J16.4 Hz), 5.04±4.99
42H, m), 4.45 41H, d, J15.6 Hz), 3.57 43H, s), 3.00 43H,
s); 13C NMR 4acetone-d6) d 180.1 4s), 164.6 4s), 163.9 4s),
163.1 4s), 142.4 4s), 140.1 4s), 139.6 4s), 138.4 4s), 138.1 4s),
137.9 4s), 137.5 4s), 137.3 4s), 130.6 4d), 129.5 4d), 129.2 4d),
128.8 4s), 128.5 4d), 128.3 4d), 128.0 4d), 127.6 4d), 126.6
4s), 126.5 4s), 126.2 4d), 125.8 4d), 125.6 4d), 125.5 4d),
124.8 4d), 123.9 4d), 123.8 4d), 123.3 4d), 123.2 4d), 116.0
4d), 112.7 4d), 112.4 4d), 109.6 4s), 108.9 4s), 51.7 4q), 51.6
4q), 50.7 4t), 49.2 4t); FABHRMS Calcd for C44H34N3O6
700.2448 [M1H]1 found 700.2440.
d 12.81 42H, s), 8.13 42H, d, J7.7 Hz), 7.50 42H, d,
J8.0 Hz), 7.34 42H, dd, J8.6, 6.8 Hz), 7.28 42H, dd,
J7.8, 6.9 Hz); 13C NMR 4DMSO-d6) d 180.8 4s), 172.4
4s), 138.1 4s), 136.3 4s), 126.0 4d), 124.2 4s), 123.6 4d),
121.9 4d), 117.6 4s), 113.7 4d); FABHRMS Calcd for
C18H11N2O2 287.0821 [M1H]1 found 287.0810.
4.1.17. 5-Benzyl-5H,12H-pyrido[1,2-a:4,5-b0]-diindolo-
6,13-dione '25). Compound 23a 41.183 g, 3.00 mmol) was
suspended in Ac2O 415 mL) at 218C and then heated at
re¯ux for 30 min. Upon cooling, the product crystallised
out as yellow needles. Collection of the solid and washing
with a small amount of cooled glacial AcOH and EtOH
42£10 mL) followed by drying at reduced pressure
produced the dione 25 4800 mg, 71%) as yellow crystals.
Mp 227.5±229.08C; IR 4KBr) cm21: 3124, 3062, 1687,
1
4.1.15. 5-Benzyl-5H,7H-indolo[2,3-b]carbazole-6,12-dione
'24). The acid 23a 4986 mg, 2.5 mmol) was suspended in
Ac2O 412.5 mL) at 218C and the resulting suspension
protected under argon. Upon dropwise addition of tri¯uoro-
acetic anhydride 42.5 mL), the suspension became dark.
After the last addition, the suspension was stirred at 218C
for 4 h and then ice 4100 mL) was added to the ¯ask. The
combined phases were removed in vacuo and a dark solid
was obtained. Recrystallisation from glacial AcOH
produced, after drying at 1208C for 15 h, 800 mg 485%)
24 as a green±black solid. This substance can also be
sublimed at 2608C/1 mmHg to produce blue-blackish crys-
tals. Mp 346.5±348.58C; IR 4KBr) cm21: 3447, 3250, 1638,
1466, 1328, 1241, 1089, 743; 1H NMR 4DMSO-d6) d 12.77
41H, bs), 8.25 41H, d, J7.3 Hz), 8.12 41H, d, J7.6 Hz),
7.68 41H, d, J7.9 Hz), 7.51 41H, d, J8.0 Hz), 7.40±7.25
49H, m), 5.98 42H, s); 13C NMR 4DMSO-d6) d 180.4 4s),
173.0 4s), 139.2 4s), 138.2 4s), 137.1 4s), 136.9 4s), 133.7 4s),
128.7 4d) 127.5 4d), 126.8 4d), 126.6 4d), 126.1 4d), 124.3 4d),
123.9 4s), 123.7 4d), 123.6 4s), 122.3 4d), 121.9 4d), 118.6 4s),
116.9 4s), 113.8 4d), 112.4 4d), 47.5 4t); MS 4ESI) [M1H]1
377, [M2H]2 375; Anal. Calcd for C25H16N2O2: C, 79.77;
H, 4.28; N, 7.44; found C, 79.65; H, 4.21; N, 7.29.
1649, 1543, 1469, 1318, 1308, 1172, 750, 742, 694; H
NMR 4DMSO-d6, 908C) d 8.49 41H, d, J8.3 Hz), 8.36
41H, d, J7.9 Hz), 7.81 41H, d, J7.9 Hz), 7.73 41H, d,
J8.4 Hz), 7.64 41H, s), 7.59 41H, dd, J8.0, 7.6 Hz),
7.51 41H, dd, J7.4, 7.1 Hz), 7.44 41H, dd, J7.6,
7.2 Hz), 7.37±7.24 46H, m), 6.05 42H, s); 13C NMR
4DMSO-d6, 908C) d 169.4 4s), 157.4 4s), 139.2 4s), 136.4
4s), 136.4 4s), 134.9 4s), 134.1 4s), 129.2 4d), 128.1 4d), 128.0
4s), 127.0 4d), 127.0 4d), 126.3 4d), 123.9 4s), 123.8 4d),
123.7 4d), 123.5 4d), 121.8 4d), 115.3 4d), 115.3 4d), 114.8
4s), 112.0 4d), 47.3 4t); MS EI 470 eV) [M1H]1 377 47%),
[M]1 376 444%), 105 418%), 91 4100%), 77 411%); Anal.
Calcd for C25H16N2O2: C, 79.77; H, 4.28; N, 7.44; found C,
79.64; H, 4.19; N, 7.33.
4.1.18. 1-Benzyl-2-'1H-indole-3-carbonyl)-1H-indole-3-
carboxylic acid '26). Magnesium turnings 478 mg,
3.21 mmol) were placed in a 100 mL ¯ask under argon.
Et2O 410 mL) and EtBr 40.24 mL, 3.22 mmol) were added.
After 30 min at 218C a solution of indole 4357 mg,
3.05 mmol) in Et2O 415 mL) was added dropwise. After
stirring for 15 min, an ethereal solution of ZnCl2
43.10 mmol, 3.1 mL) was added and the resulting suspen-
sion stirred for 30 min whereupon the anhydride 22
4832 mg, 3.00 mol) was added in one portion. The resulting
yellow suspension was stirred for 5 h and then quenched
with a saturated aq. solution of NH4Cl 420 mL). After stir-
ring for 30 min, the solution was taken up in EtOAc
4200 mL) and acidi®ed with 1 M HCl 4200 mL). The aq.
phase was separated and the organic phase was washed
with water 4100 mL), brine 4100 mL) and dried over
MgSO4. Evaporation of the solvent produced a yellow
solid, which was suspended in ether 425 mL). After stirring
overnight, the carboxylic acid 26 was ®ltered off and after
drying gave 813 mg 469%) as a yellow powder. Mp 234.0±
235.58C; IR 4KBr) cm21: 3178, 1689, 1524, 1497, 1456,
4.1.16. 5H,7H-Indolo[2,3-b]carbazole-6,12-dione '4). To
a solution of 5-benzyl-5H,7H-indolo[2,3-b]carbazole-6,12-
dione 424) 4392 mg, 1.05 mmol) in benzene under argon,
solid AlCl3 41389 mg, 10.41 mmol) was added in one
portion at 218C. After stirring at this temperature for 1 h,
the suspension was gradually heated over a 20 min period to
re¯ux. After 90 min at re¯ux, the suspension was allowed to
cool to 218C, poured on ice 4100 mL) and diluted with
EtOAc 4100 mL). Upon separation of the organic phase,
the water phase was extracted with EtOAc 42£50 mL).
The combined organic phases were washed with water
42£50 mL), brine 42£50 mL) and dried over MgSO4.
Evaporation of the solvents produced a dark green-blackish
solid that was subjected to column chromatography on silica
gel with CHCl3±hexane 450±100%) as the eluent. The ®rst
fractions contained unreacted starting material. These frac-
tions were collected and the solvents were evaporated. The
residue was recrystallised twice from glacial AcOH, ®ltered
and dried to give 24 438 mg). Later, fractions containing 4
were pooled and evaporated to produce 170 mg of 4 4yield
63% based on recovered starting material) was obtained.
Mp.4008C; IR 4KBr) cm21: 3259, 1651, 1634, 1615,
1
743; H NMR 4DMSO-d6) d 13.21 41H, bs), 11.88 41H, d,
J2.3 Hz), 8.21±8.18 41H, m), 7.67 41H, d, J3.0 Hz), 7.64
41H, d, J8.5 Hz), 7.54 41H, d, J8.0 Hz), 7.52±7.49 41H,
m), 7.36±7.28 43H, m), 7.26±7.19 43H, m), 7.17±7.13 43H,
m), 5.87 42H, s); 13C NMR 4DMSO-d6) d 186.0 4s), 162.7
4s), 138.1 4s), 137.1 4s), 136.8 4s), 135.2 4d), 128.6 4d), 127.8
4s), 127.2 4d), 126.4 4d), 125.6 4s), 125.3 4s), 125.1 4d), 122.9
4d), 121.7 4d), 121.4 4d), 121.3 4d), 121.0 4d), 118.4 4s),
112.3 4d), 111.5 4d), 47.2 4t); FABHRMS Calcd for
C25H19N2O3 395.1396 [M1H]1 found 395.1396.