Molecules 2021, 26, 4739
14 of 31
IR (KBr): 3388 cm−1 (NH), 1766 cm−1, 1704 cm−1 (C=O), 1616 cm−1, 1589 cm−1
,
1
1513 cm−1 (C=C, arom.), H-NMR (400 MHz, DMSO-d6):
δ (ppm) = 7.17 (ddd, J = 8.1,
7.1, 1.1 Hz, 2H), 7.28 (ddd, J = 8.2, 7.1, 1.2 Hz, 2H), 7.58 (dt, J = 8.2, 0.9 Hz, 2H), 7.93
(dt, J = 8.0, 0.9 Hz, 2H), 8.26 (d, J = 3.0 Hz, 2H), 12.44 (s, 2H, NH), 13C-NMR (101 MHz,
DMSO-d6):
(C); C20H12N2O2 (312.33); Anal. calcd. for C20H12N2O2: C 76.91, H 3.87, N 8.97; found C
76.41, H 3.70, N 8.87; MS (EI): m/z (%) = 312 [M]+ (35), 256 [M+
56] (100); isocratic HPLC:
97.1% at 254 nm, 97.6% at 280 nm, tms = 3.63 min, tm (DMSO) = 1.15 min (ACN/H2O 50:50);
δ (ppm) = 112.6, 121.3, 122.6, 123.0, 131.1 (CH), 106.3, 125.0, 136.8, 177.0, 194.8
−
gradient HPLC: 95.1% at 254 nm, tms = 11.0 min, tm (DMSO) = 1.25 min;
331, 410.
λ
max
(nm): 271,
3-(5-Bromo-1H-indol-3-yl)-4-(1H-indol-3-yl)cyclobut-3-ene-1,2-dione (2b)
Synthesis according to General Procedure C (reaction time: 48 h) from 3-chloro-4-
(1H-indol-3-yl)cyclobut-3-ene-1,2-dione (5a, 256 mg, 1.11 mmol) and 5-bromo-1H-indole
−1
(392 mg, 2.00 mmol). The yield of the tawny powder was 166 mg (38%). IR (KBr): 3425 cm
(NH), 3127 cm−1 (CH, arom.), 2919 cm−1 (CH, aliph.), 1748 cm−1, 1714 cm−1 (C=O); 1H-
NMR (400 MHz, DMSO-d6):
δ (ppm) = 7.19 (ddd, J = 8.1, 7.1, 1.1 Hz, 1H, ArH), 7.30 (ddd,
J = 8.2, 7.1, 1.2 Hz, 1H, ArH), 7.41 (dd, J = 8.6, 2.0 Hz, 1H, ArH), 7.51–7.63 (m, 2H, ArH), 7.90
(ddt, J = 8.0, 1.2, 0.6 Hz, 1H, ArH), 8.22 (d, J = 2.0 Hz, 1H, ArH), 8.26 (d, J = 3.0 Hz, 1H, ArH),
8.35 (d, J = 3.1 Hz, 1H, ArH), 12.50 (d, J = 3.2 Hz, 1H, NH), 12.57 (d, J = 3.3 Hz, 1H, NH);
13C-NMR (151 MHz, DMSO-d6):
δ (ppm) = 112.7, 114.6, 121.4, 122.6, 123.1, 124.8, 125.6,
131.2, 132.0 (CH), 106.0, 106.2, 113.8, 124.9, 127.0, 135.5, 136.9, 176.3, 177.3, 194.6, 194.7 (C);
C20H11BrN2O2 [391.22]; Anal. calcd. for C20H11BrN2O2: C 61.40, H 2.83, N 7.16; found C
61.38, H 2.74, N 6.85; MS (EI): m/z (%) = 390 [M]+ (29), 334 [M+
−
56] (100); isocratic HPLC:
99.4% at 254 nm and 99.6% at 280 nm, tms = 5.84 min, tm = 1.11 min (ACN/H2O 50:50);
max (nm): 273, 329, 346; gradient HPLC: 98.0% at 254 nm, tms = 11.9 min, tm = 1.25 min.
λ
3-(5-Chloro-1H-indol-3-yl)-4-(1H-indol-3-yl)cyclobut-3-ene-1,2-dione (2c)
Synthesis according to General Procedure C (reaction time: 20 h) from 3-chloro-4-
(1H-indol-3-yl)cyclobut-3-ene-1,2-dione (5a, 241 mg, 1.04 mmol) and 5-chloro-1H-indole
(227 mg, 1.50 mmol). Boiling in ethanol/toluene yielded a yellowish powder (133 mg,
38%). IR (KBr): 3395 cm−1 (NH), 1749 cm−1, 1714 cm−1 (C=O), 1618 cm−1, 1539 cm−1
(C=C, arom.); 1H-NMR (600 MHz, DMSO-d6):
δ (ppm) = 7.20 (ddd, J = 8.1, 7.0, 1.1 Hz, 1H,
ArH), 7.27–7.33 (m, 2H, ArH), 7.57–7.63 (m, 2H, ArH), 7.91 (ddt, J = 8.1, 1.4, 0.7 Hz, 1H,
ArH), 8.08 (dt, J = 2.1, 0.6 Hz, 1H, ArH), 8.28 (d, J = 3.1 Hz, 1H, ArH), 8.35 (d, J = 3.1 Hz,
1H, ArH), 12.50 (d, J = 3.1 Hz, 1H, NH), 12.58 (d, J = 3.0 Hz, 1H, NH); 13C-NMR (151 MHz,
DMSO-d6):
δ (ppm) = 112.7, 114.2, 121.4, 121.9, 122.6, 123.1, 123.2, 131.3, 132.2 (CH), 106.2.
106.2, 124.9, 125.8, 126.4, 135.3, 136.9, 176.4, 177.4, 194.7, 194.8 (C); C20H11ClN2O2 [347.77];
Anal. calcd. for C20H11ClN2O2: C 69.27, H 3.20, N 8.08; found C 68.87, H 3.10, N 7.93; MS
(EI): m/z (%) = 346 [M]+·(23), 290 [M+-56] (100); isocratic HPLC: 95.9% at 254 nm and 96.8%
at 280 nm, tms = 5.17 min, tm = 1.11 min (ACN/H2O 50:50);
λ
max
(nm): 273, 328 and 347;
gradient HPLC: 98.3% at 254 nm, tms = 11.8 min, tm = 1.25 min.
3-(1H-Indol-3-yl)-4-(5-methoxy-1H-indol-3-yl)cyclobut-3-ene-1,2-dione (2d)
Synthesis according to General Procedure C (reaction time: 20 h) from 3-chloro-4-
(1H-indol-3-yl)cyclobut-3-ene-1,2-dione (5a, 241 mg, 1.04 mmol) and 5-methoxy-1H-indole
−1
(322 mg, 2.19 mmol). The yield of the yellow powder was 40 mg (11%). IR (KBr): 3298 cm
(NH), 3144 cm−1 (CH, arom.), 2964 cm−1 (CH, aliph.), 1748 cm−1, 1704 cm−1 (C=O); 1H-
NMR (600 MHz, DMSO-d6):
δ (ppm) = 3.53 (s, 3H, CH3), 6.89 (dd, J = 8.8, 2.5 Hz, 1H, ArH),
7.15 (ddd, J = 8.0, 7.0, 1.0 Hz, 1H, ArH), 7.27 (ddd, J = 8.2, 7.1, 1.1 Hz, 1H, ArH), 7.31–7.34
(m, 1H, ArH), 7.47 (dd, J = 8.8, 0.5 Hz, 1H, ArH), 7.58 (dt, J = 8.1, 0.9 Hz, 1H, ArH), 7.91 (dt,
J = 8.0, 0.9 Hz, 1H, ArH), 8.21 (s, 1H, ArH), 8.25 (s, 1H, ArH), 12.38 (s, 2H, NH); 13C-NMR
(151 MHz, DMSO-d6):
δ (ppm) = 54.8 (CH3), 104.7, 112.5, 112.8, 113.3, 121.1, 122.5, 122.9,
131.0, 131.4 (CH), 106.2, 106.3, 125.1, 125.5, 131.6, 136.6, 154.5, 176.3, 176.9, 194.4, 195.0 (C);