NOVEL SYNTHESIS 3-ALKENYLATED INDOLES
1747
(30 mmol, 5.1 g) in 10 mL 96% ethanol and p-TsOH (1 mmol, 0.2 g) was added. The
reaction mixture was stirred at reflux for 15 h, until complete consumption of
2-methylindole was confirmed by thin-layer chromatography (TLC; petroleum ether:
EtOAc; 3:1). TLC chromatogram showed two spots corresponding to compounds 1
and 3 with a trace of 4. When the reaction mixture was cooled to room temperature,
it deposited copiously, a solid which was separated by filtration. The filtrate showed
traces of all three products, worthless for workup. The precipitate was dispersed in
hot methanol to dissolve 3, filtered hot, and cooled to obtain 1 as a yellow powder.
Evaporation of the filtrate furnished compound 3 as a pinkish solid.
Exact replication of this reaction with EMMN in refluxing ethanol produced 2
in only poor yield, the major product being 3 in 38% yield. Performing the reaction
in acetonitrile increased the yield of 2 to 35%.
Ethyl 2-cyano-3(2-methyl-1H indol-3-yl)prop-2-enoate (C15H14N2O2, 1)[9]
Yellow powder; yield 6 g (80%); mp: 245–246 ꢁC.
.
[(2-Methylindol-3-yl)methylene]propanedinitriles (C13H9N3, 2). Yellow
powder; yield 2.1 g (35%); mp: 233.7–235 ꢁC; IR (nmax=cmꢀ1): 3446, 3328, 2214,
1569, 1514, 1458, 1388, 1350, 1253, 1166, 1098, 746; MS (70 eV): m=z ¼ 207 (Mþ,
1
18), 160 (11), 154 (65), 142 (15), 84 (25), 74 (39), 44 (100%); H NMR (500 MHz,
DMSO-d6): d ¼ 2.50 (3H, s, CH3), 7.21 (2H, m, ArH), 7.43 (1H, d, J ¼ 6.9, ArH),
8.08 (1H, d, J ¼ 7.1, ArH), 8.25 (1H, s, -CH ¼), 12.72 (1H, s, NH); 13C NMR
(125.7 MHz, DMSO-d6): d ¼ 13.5, 110.2, 112.1, 114.9, 117.2, 121.9, 123.2, 126.0,
131.8, 135.4, 150.2. Anal. calc. for C13H9N3: C, 75.35; H, 4.38; N, 20.28. Found:
C, 75.29; H, 4.31; N, 20.35.
3-[Bis(2-methyl-1H indol-3-yl)methyl]-2-methyl-1H-indole (C28H25N3, 3)[13]
.
Pink powder; yield 6 g (50%); mp: 333–335 ꢁC.
3-[3H-Indol-3-ylidenemethyl]-1H-indole (C19H18N2, 4)[10c]. Orange pow-
der; mp: 272 ꢁC (decomp.).
Ethyl-3-(f2-[2,2-bis(1H-indol-3-yl)ethyl]phenylgamino)-2-cyanoprop-
2-enoate (C30H26N4O2, 6). White powder; mp: 190 ꢁC; yield: 5.2 g (55%); IR
(KBr) (nmax=cmꢀ1): 3354, 3324, 2207, 1673, 1634, 1599, 1456, 1416, 1379, 1250,
1
1172, 743; H NMR (500 MHz, DMSO-d6): d ¼ 1.22 (3H, t, J ¼ 7.0 Hz, OCH2CH3),
3.54 (2H, d, J ¼ 7.7, CH-CH2), 4.15 (2H, q, J ¼ 7.1, OCH2CH3), 4.76 (1H, t,
J ¼ 7.7 Hz, CH-CH2), 6.79 (2H, t, J ¼ 7.6 Hz), 6.96 (2H, t, J ¼ 7.5 Hz), 7.03 (1H, t,
J ¼ 7.4 Hz), 7.15 (1H, t, J ¼ 8.3 Hz), 7.21 (2H, d, J ¼ 2 Hz, CH), 7.26 (3H, t,
J ¼ 8.02 Hz), 7.33 (1H, d, J ¼ 8.0 Hz), 7.37 (2H, d, J ¼ 7.9 Hz), 8.04 (1H, d,
J ¼ 13.4 Hz, CH-NH), 10.71 (2H, s, 2NHindolic), 10.86 (1H, d, J ¼ 13.4 Hz, CH-N-
H);13C NMR (125.7 MHz, DMSO-d6): d ¼ 15.0, 15.2, 35.5, 37.3, 37.5, 60.9, 61.3,
74.1, 112.1, 112.2, 118.2, 118.5, 118.6, 118.7, 118.8, 118.9, 119.7, 121.4, 123.1,
123.2, 126.1, 127.3, 128.1, 131.8, 132.1, 137.1, 138.1, 155.2, 157.1, 167.8 ppm; MS
(70 eV): m=z ¼ 474 (Mþ, 22), 358 (16), 311 (12), 282 (9), 245 (100), 218 (83), 189
(10), 155 (15), 117 (22), 90 (8%), Anal. calc. for C30H26N4O2: C, 75.93; H, 5.52;
N, 11.81. Found: C, 75.89; H, 5.51; N, 11.83.