1-Benzyl-2,5-diphenylpyrrole 16b. Crystalline solid, mp 143–
144 ЊC (lit.,12 144 ЊC).
MHz, CDCl3) 3.37 (3H, s, Me), 7.42–7.47 (10H, m, Ph); m/z
393 (Mϩ ϩ 4, 50%), 391 (Mϩ ϩ 2, 100), 389 (Mϩ, 51), 310
(Mϩ Ϫ Br, 3), 297 (Mϩ Ϫ Me Ϫ Br, 3), 230 (Mϩ Ϫ Br2, 13), 216
(Mϩ Ϫ Br2 Ϫ Me, 9), 202 (5), 195 (5), 189 (5), 128 (7), 118 (17),
113 (12) and 77 (Phϩ, 18).
1-(4-Methoxybenzyl)-2,5-diphenylpyrrole 16c. Crystalline
solid, mp 109–110 ЊC (Found: Mϩ, 339.1623. C24H21NO
requires Mϩ, 339.1623); νmax(CHCl3)/cmϪ1 3024, 3014, 1666,
1604, 1512, 1485, 1466, 1305, 1250, 1243, 1232, 1216, 1203,
1194, 1176, 1042, 1037 and 917; δH(270 MHz, CDCl3) 3.80 (3H,
s, OMe), 5.17 (2H, s, CH2), 6.34 (2H, s, pyrrole), 6.57–6.66 (2H,
d, p-MeOC6H4), 6.85–6.88 (2H, d, p-MeOC6H4), 7.27–7.38
(10H, m, Ph); m/z 339 (Mϩ, 1.3%), 218 (Mϩ Ϫ p-MeOC6H4-
CH2, 3), 179 (22), 121 (p-MeOC6H4CH2ϩ, 100) and 77 (Phϩ,
22).
3,4-Dibromo-1-ethyl-2,5-diphenylpyrrole 20a. Crystals, mp
118–120 ЊC; νmax(CHCl3)/cmϪ1 3036, 3008, 1432, 1345, 1291,
1248, 1244, 1216, 1214, 1183, 1045, 902 and 848; δH(270 MHz,
CDCl3) 0.75–0.80 (3H, t, CH3), 3.82–3.88 (2H, q, CH2) and
7.40–7.50 (10H, m, Ph); m/z 407 (Mϩ ϩ 4, 20%), 405 (Mϩ ϩ 2,
40), 403 (Mϩ, 20), 376 (Mϩ Ϫ Et, 5), 216 (Mϩ Ϫ Et Ϫ Br2, 10),
113 (100) and 77 (Phϩ, 45).
1-(4-Nitrobenzyl)-2,5-diphenylpyrrole 16d. Yellow crystalline
solid, mp 102–103 ЊC (Found: Mϩ, 354.1367. C23H18N2O2
requires Mϩ, 354.1368); νmax(CHCl3)/cmϪ1 3037, 3005, 1604,
1518, 1486, 1466, 1452, 1388, 1345, 1321, 1266, 1246, 1236,
1215, 1111, 1075, 1043, 917 and 860; δH(270 MHz, CDCl3)
5.31 (2H, s, CH2), 6.38 (2H, s, pyrrole), 6.69–6.72 (2H, d,
p-NO2C6H4), 7.27–7.34 (10H, m, Ph), 7.93–7.96 (2H, d,
p-NO2C6H4); m/z 354 (Mϩ, 51%), 218 (Mϩ Ϫ p-NO2C6H4CH2,
100), 191 (5), 149 (6), 115 (8), 106 (20), 89 (9) and 77 (3).
1-tert-Butyloxycarbonylamino-2,5-diphenylpyrrole 8d. Crys-
talline solid, mp 184–185 ЊC (lit.,13 183–184.5 ЊC).
1-Benzyl-3,4-dibromo-2,5-diphenylpyrrole 20b. Needles, mp
177–178 ЊC; νmax(CHCl3)/cmϪ1 3033, 3017, 1605, 1497, 1483,
1453, 1318, 1241, 1232, 1216, 1213, 1197, 1045, 1030, 974 and
817; δH(270 MHz, CDCl3) 5.02 (2H, s, PhCH2), 6.52–6.55 (2H,
m, Ph), 7.08–7.10 (3H, m, Ph) and 7.30–7.39 (10H, m, Ph);
m/z 469 (Mϩ ϩ 4, 10%), 467 (Mϩ ϩ 2, 17) 465 (Mϩ, 10), 388
(Mϩ Ϫ Ph, 6), 386 (Mϩ Ϫ Br, 5), 376 (Mϩ Ϫ PhCH2, 17), 307 (7),
295 (Mϩ Ϫ PhCH2 Ϫ Br, 5), 216 (Mϩ Ϫ PhCH2 Ϫ Br2, 13) 204
(7), 113 (20) and 91 (PhCH2ϩ, 100).
3,4-Dibromo-1-(4-methoxybenzyl)-2,5-diphenylpyrrole 20c.
Needles, mp 127–128 ЊC; νmax(CHCl3)/cmϪ1 3038, 3024, 3017,
1613, 1514, 1483, 1467, 1306, 1253, 1244, 1216, 1196, 1177,
1046, 1037, 1030, 813 and 769; δH(270 MHz, CDCl3) 3.71 (3H,
s, OMe), 4.95 (2H, s, CH2), 6.40–6.43 (2H, d, 4-MeOC6H4),
6.59–6.62 (2H, d, 4-MeOC6H4) and 7.31–7.42 (10H, m, Ph);
m/z 499 (Mϩ ϩ 4, 4%), 497 (Mϩ ϩ 2, 8), 495 (Mϩ, 4), 376
(Mϩ Ϫ p-methoxybenzyl, 1.4), 295 (Mϩ Ϫ p-methoxybenzylϪ
Br,1.2),216(Mϩ Ϫ p-methoxybenzylϪBr2,5),121(p-MeOC6H4-
CH2, 100), 113 (11) and 77 (Phϩ, 11).
3,4-Dibromo-1-(4-nitrobenzyl)-2,5-diphenylpyrrole 20d. Crys-
tals, mp 166–167 ЊC; νmax(CHCl3/cmϪ1 3033, 3017, 1603, 1525,
1484, 1346, 1315, 1244, 1232, 1216, 1213, 1196 and 861; δH(270
MHz, CDCl3) 5.14 (2H, s, CH2), 6.67–6.71 (2H, d, 4-NO2-
C6H4), 7.27–7.45 (10H, m, Ph) and 7.93–7.97 (2H, d, 4-NO2-
C6H4); m/z 516 (Mϩ ϩ 4, 1.2%), 514 (Mϩ ϩ 2, 19), 512 (Mϩ,
37), 496 (Mϩ Ϫ O, 7), 376 (Mϩ Ϫ NO2 Ϫ C6H4CH2, 100), 297
(Mϩ Ϫ NO2C6H4CH2 Ϫ Br, 25), 296 (25), 216 (Mϩ Ϫ NO2C6H4-
CH2 Ϫ Br2, 51) 113 (55), 90 (32) and 77 (Phϩ, 12).
1-Ethoxycarbonylmethyl-2,5-diphenylpyrrole 16e. Crystalline
solid, mp 98–99 ЊC (Found: Mϩ, 305.1414. C20H19NO2 requires
Mϩ, 305.1416); νmax(CHCl3)/cmϪ1 3036, 3002, 1746 (C᎐O),
᎐
1605, 1485, 1467, 1451, 1377, 1250, 1245, 1243, 1215, 1211,
1189, 1033, 922 and 874; δH(270 MHz, CDCl3) 1.10–1.14 (3H, t,
CH3), 4.06–4.14 (2H, q, CH2), 4.57 (2H, s, NCH2), 6.33 (2H, s,
ArH) and 7.32–7.44 (10H, m, Ph); m/z 305 (Mϩ, 100%), 277
(Mϩ Ϫ Et, 15), 232 (Mϩ Ϫ CO2Et, 93), 218 (6), 202 (9), 154 (8),
128 (18), 115 (10), 102 (7) and 77 (14).
Methyl 2,5-diphenylpyrrole-1-carboxylate 8c
In a 250 ml three-neck flask fitted with a gas inlet tube, reflux
condenser with drying tube and a magnetic stirrer were placed
2,5-diphenylpyrrole (5.0 g) and dry light petroleum (bp 60–
80 ЊC) (50 ml). The light petroleum was warmed to dissolve the
pyrrole after which potassium (1 g) was added to the solution.
After the mixture had been stirred and refluxed for 3 h under
dry nitrogen, methyl chloroformate (2.5 g) was added to it and
refluxing was continued for 0.5 h. After this the mixture was
cooled and acetic acid (5 ml) was added to it with rapid stirring
to react with any remaining potassium. The reaction mixture
was then poured into water (200 ml) and ether (100 ml). The
organic layer was separated and the aqueous layer was
extracted with ether (2 × 20 ml). The combined ether extracts
were dried (MgSO4) and evaporated at reduced pressure to
leave a pale brown oil which subsequently solidified. Recrystal-
lization of this from hexane gave the product 8c (4.0 g, 62%) as
pale yellow cubic crystals, mp 99–100 ЊC (lit.,14 100 ЊC).
3,4-Dibromo-1-ethoxycarbonylmethyl-2,5-diphenylpyrrole
20e. Needles, mp 142–143 ЊC; νmax(CHCl3)/cmϪ1 3029, 3024,
3014, 1748 (C᎐O), 1605, 1484, 1446, 1417, 1376, 1322, 1254,
᎐
1244, 1241, 1232, 1216, 1213, 1194, 1191, 1046, 1028, 974, 812,
794 and 770; δH(270 MHz, CDCl3) 1.07–1.12 (3H, t, CH3),
4.02–4.07 (2H, q, CH2), 4.37 (2H, s, NCH2), 7.39–7.45 (10H, m,
Ph) m/z 465 (Mϩ ϩ 4, 5%), 463 (Mϩ ϩ 2, 100), 461 (Mϩ, 55),
390 (Mϩ Ϫ CO2Et, 26), 309 (Mϩ Ϫ CO2Et Ϫ Br, 42), 230
(Mϩ Ϫ CO2Et Ϫ Br2, 45), 202 (27), 127 (19), 113 (12), 105 (20)
and 77 (Phϩ, 24).
Reactions of trithiazyl trichloride (NSCI)3
1-Amino-2,5-diphenylpyrrole 18
With 1,2,5-triphenylpyrrole 5: typical procedures. (a) To tetra-
chloromethane (20 ml) was added 1,2,5-triphenylpyrrole (295
mg, 1 mmol) and the mixture was warmed with stirring to give a
clear solution. To this stirred solution was added trithiazyl tri-
chloride (82 mg. 0.33 mmol) after which the mixture was heated
at reflux for 12 h under nitrogen. The tetrachloromethane was
removed from the mixture by evaporation in vacuo and the resi-
due was purified by column chromatography on silica gel. Elu-
tion with dichloromethane (20%) in light petroleum gave 3,4-
dichloro-1,2,5-triphenylpyrrole 7 (60 mg, 17%) as colourless
needles, mp 214–215 ЊC (Found: Mϩ, 363.0582. C22H15NCl2
requires Mϩ, 363.0582); νmax(CHCl3)/cmϪ1 3019, 1604, 1500,
1489, 1444, 1350, 788, 773 and 763; δH(270 MHz, CDCl3) 6.8–
7.3 (15H, m, Ph); δC(67.5 MHz, CDCl3) 137.70, 130.45, 129.75,
129.71, 128.67, 127.88–127.59 (3 singlets?), 127.51 and 111.14;
m/z 367 (Mϩ ϩ 4, 12%), 365 (Mϩ ϩ 2, 66), 363 Mϩ, 100), 328
(5), 293 (16), 227 (7), 225 (21), 145 (12) and 77 (Phϩ, 16).
Elution with dichloromethane (30%) in light petroleum gave
A
mixture of 1-tert-butyloxycarbonylamino-2,5-diphenyl-
pyrrole 8d (2.2 g) and methanol (30 ml) was heated to reflux and
hydrogen chloride gas was passed through the solution for 0.5
h. A pink solid separated. The mixture was allowed to stand at
room temperature for 2 h after which the solid was filtered off
and washed with methanol. The crude solid was recrystallized
from dimethylformamide to give the product 18 (1.23 g, 80%) as
cream coloured flakes, mp 218–219 ЊC (lit.,13 218–220 ЊC).
The following 3,4-dibromo-2,5-diphenylpyrroles were pre-
pared by brominating the corresponding 2,5-diphenylpyrroles
with N-bromosuccinimide (NBS) (2 equiv.) in dry tetrahydro-
furan at 4 ЊC.6 These brominated pyrroles were purified by
recrystallization. The physical data for the compounds pre-
pared are as follows.
3,4-Dibromo-1-methyl-2,5-diphenylpyrrole. Crystals, mp 128–
130 ЊC; νmax(CHCl3)/cmϪ1 3036, 3008, 1604, 1482, 1471, 1432,
1324, 1242, 1216, 1214, 1195, 1160, 1030, 975 and 920; δH(270
J. Chem. Soc., Perkin Trans. 1, 1997
3193