Thomas and Tyagi
JOCArticle
funnel. After the addition, the reaction mixture was stirred at
room temperature for 24 h. Finally, the reaction was quenched by
addition of ice-cold water. The precipitates formed were filtered
and dried under vacuum. TLC indicated the presence of a single
component: yellow solid; yield 3.38 g (96%, 9.54 mmol); mp 201 °C;
1H NMR(500MHz, CDCl3) δ0.98 (t, J = 7.5 Hz, 3H), 1.40-1.45
(m, 2H), 1.91-1.94 (m, CH2), 4.48 (t, J = 7.5 Hz, 2H), 7.37 (d,
J = 9.0 Hz, 1H), 7.69-7.71 (m, 1H), 7.76-7.79 (m, 2H), 8.14 (dd,
J = 7.0 Hz, 1.3 Hz, 1H), 8.28 (dd, J = 7.0 Hz, 1.3 Hz, 1H), 8.61 (d,
J = 1.5 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 13.8, 20.3, 30.5,
41.4, 111.0, 113.5, 121.1, 125.4, 126.2, 127.9, 129.2, 129.4, 133.4,
138.6, 139.4, 140.9, 142.9, 145.5, 162.6; HRMS calcd for
C18H16BrN3 m/z 353.0528, found 353.0526.
General C-N Coupling Procedure for the Synthesis of the
Diarylamine-Substituted Compounds 3-6. A mixture of 9-bromo-
6-butyl-6H-indolo[2,3-b]quinoxaline (1.77 g, 5 mmol), diarylamine
(6 mmol), Pd(dba)2 (0.1 mmol), (t-Bu)3P (0.1 mmol), sodium tert-
butoxide (7.5 mmol), and toluene (15 mL) taken in a Schlenk tube
was heated at 80 °C for 12 h. After completion of the reaction, the
volatiles were evaporated to leave an orange residue. The residue
was purified by column chromatography by using dichloro-
methane/hexane mixture (1:2) as eluant. For the compounds
6and 7, the initial residue was washed with methanol before column
chromatography purification to remove the unreacted diarylamine.
6-Butyl-N,N-diphenyl-6H-indolo[2,3-b]quinoxalin-9-amine (3):
orange solid; yield 72%; mp 188 °C; 1H NMR (400 MHz, CDCl3)
δ 0.99 (t, J = 7.2 Hz, 3H), 1.46 (sext, J = 7.2 Hz, 2H), 1.94 (quin,
J = 7.2 Hz, 2H), 4.47 (t, J = 7.2 Hz, 2H), 6.97 (t, J = 7.3 Hz, 2H),
7.10 (d, J = 7.6 Hz, 4H), 7.21-7.25 (m, 4H), 7.39 (d, J = 8.7 Hz,
1H), 7.52 (dd, J= 8.7 Hz, 2.2 Hz, 1H), 7.62 (td, J= 7.2 Hz, 1.4 Hz,
1H), 7.72 (td, J= 8.4 Hz, 1.2 Hz, 1H), 8.10 (dd, J= 8.4 Hz, 1.2 Hz,
1H), 8.19 (dd, J = 8.4 Hz, 1.3 Hz, 1H), 8.26 (d, J = 2.2 Hz, 1H);
13C NMR (125 MHz, CDCl3) δ 13.8, 20.4, 30.7, 41.4, 110.4, 120.1,
120.5, 121.5, 121.7, 122.0, 122.3, 122.5, 122.7, 123.3, 123.3, 123.5,
124.9, 125.9, 126.1, 127.8, 128.0, 128.8, 129.27, 129.29, 129.34,
129.5, 129.7, 139.2, 139.7, 140.7, 141.0, 141.8, 146.1, 147.9, 148.4;
HRMS calcd for C30H27N4 (M þ H) m/z 443.2236, found
443.2235. Anal. Calcd for C30H26N4: C, 81.42; H, 5.92; N, 12.66.
Found: C, 81.57; H, 6.01; N, 12.45.
6-Butyl-N-(naphthalen-1-yl)-N-phenyl-6H-indolo[2,3-b]quinoxalin-
9-amine (4): orange solid; yield 81%; mp 175 °C; 1H NMR (400
MHz, CDCl3) δ 0.98 (t, J = 7.4 Hz, 3H), 1.44 (sext, J = 7.5 Hz,
2H), 1.92 (quin, J = 7.4 Hz, 2H), 4.44 (t, J = 7.3 Hz, 2H), 6.85 (t,
J = 7.3 Hz, 1H), 6.95 (d, J = 7.7 Hz, 2H), 7.15-7.19 (m, 2H),
7.32-7.37 (m, 3H), 7.42-7.48 (m, 2H), 7.51 (dd, J = 8.7 Hz, 2.3
Hz, 1H), 7.60 (td, J = 7.6 Hz, 1.4 Hz, 1H), 7.68 (td, J = 7.7 Hz, 1.5
Hz, 1H), 7.75 (d, J = 8.4 Hz, 1H), 7.87 (d, J = 8.2 Hz, 1H), 8.04 (d,
J = 8.4 Hz, 1H), 8.09 (dd, J = 8.4 Hz, 1.0 Hz, 1H), 8.16 (dd, J =
8.3 Hz, 1.2 Hz, 1H) 8.22 (d, J = 2.2 Hz, 1H); 13C NMR (125 MHz,
CDCl3) δ 13.7, 20.2, 30.5, 41.1, 110.0, 117.7, 120.1, 120.4, 120.8,
124.2, 126.0, 126.1, 126.3, 126.9, 127.6, 127.7, 128.3, 128.6, 129.0,
131.0, 135.3, 138.9, 139.6, 140.3, 140.5, 142.6, 143.8, 145.9, 149.3;
HRMS calcd for C34H29N4 (M þ H) m/z 493.2392, found
493.2400. Anal. Calcd for C34H28N4: C, 82.90; H, 5.73; N, 11.37.
Found: C, 82.78; H, 5.51; N, 11.26.
C38H30N4: C, 84.10; H, 5.57; N, 10.32. Found: C, 83.87; H, 5.43;
N, 10.18.
6-Butyl-N-phenyl-N-(pyren-2-yl)-6H-indolo[2,3-b]quinoxalin-
9-amine (6): red solid; yield 85%; mp 161 °C; H NMR (400
1
MHz, CDCl3) δ 0.97 (t, J = 7.4 Hz, 3H), 1.43 (sext, J = 7.6 Hz,
2H), 1.91 (quin, J = 7.5 Hz, 2H), 4.43 (t, J = 7.3 Hz, 2H), 6.92 (t,
J = 7.3 Hz, 1H), 7.02 (dd, J = 8.7 Hz, 1.0 Hz, 2H), 7.15-7.21
(m, 2H), 7.34 (d, J = 8.7 Hz, 1H), 7.55-7.60 (m, 2H), 7.68-7.70
(m, 1H), 7.88 (d, J = 8.2 Hz, 1H), 7.91-7.98 (m, 2H), 8.04 (s,
2H), 8.07-8.10 (m, 2H), 8.14-8.17 (m, 3H) 8.25 (d, J = 9.2 Hz,
1H). 8.29 (d, J = 2.2 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ
13.8, 20.3, 30.7, 41.3, 110.3, 117.9, 120.3, 120.8, 121.1, 123.4,
124.9, 125,0, 125.2, 126.1, 126.2, 126.5, 127.0, 127.2, 127.5,
127.88, 127.92, 128.7, 129.0, 129.2, 129.3, 129.4, 131.1, 131.3,
139.0, 139.7, 140.4, 140.7, 141.3, 142.9, 146.0, 149.6; HRMS
calcd for C40H31N4 (M þ H) m/z 567.2549, found 567.2550.
Anal. Calcd for C40H30N4: C, 84.78; H, 5.34; N, 9.52. Found: C,
84.61; H, 5.21; N, 9.65.
4-(5-(6-Butyl-6H-indolo[2,3-b]quinoxalin-9-yl)thiophene-2-yl)-
N,N-diphenylaniline (7). To a mixture of 9-bromo-6-butyl-6H-
indolo[2,3-b]quinoxaline (1.77 g, 5 mmol), N,N-diphenyl-4-(5-(tri-
butylstannyl)thiophene-2-yl)aniline23 (3.7 g, 6 mmol), and dry
dimethylformamide (10 mL) was added Pd(PPh3)2Cl2 (35 mg)
and the mixture heated at 70 °C for 17 h. After the reaction was
over, the orange suspension was cooled, and methanol (30 mL) was
added to complete the precipitation. It was filtered and the residue
dried. The crude product was purified by column chromatography
on silica gel by using a hexane/dichloromethane mixture (2:1) as
eluant: orange solid; yield 4.56 (76%); mp 218 °C; 1H NMR (400
MHz, CDCl3) δ 0.98 (t, J = 7.4 Hz, 3H), 1.42 (sext, J = 7.5 Hz,
2H), 1.92 (quin, J=7.4 Hz, 2H), 4.49 (t, J=7.2 Hz, 2H), 7.01-7.13
(m, 9H), 7.22-7.28 (m, 7H), 7.35 (d, J=3.7 Hz, 1H), 7.45-7.51
(m, 3H), 7.67 (td, J = 7.6 Hz, 1.3 Hz, 1H), 7.75 (td, J = 7.4 Hz,
1.4 Hz, 1H), 7.94 (dd, J = 8.5 Hz, 1.7 Hz, 1H), 8.13 (dd, J =
7.9 Hz, 1.0 Hz, 1H) 8.30 (dd, J = 8.3 Hz, 1.1 Hz, 1H). 8.72 (d, J=
1.3 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 13.9, 20.4, 30.7, 41.3,
100.0, 119.3, 119.9, 123.3, 123.3, 123.6, 123.7, 124.6, 126.1, 126.3,
127.64, 127.9, 128.4, 128.5, 128.9, 129.4, 139.3, 139.8, 140.8, 142.7,
143.0, 143.5, 145.9, 147.2; HRMS calcd for C40H33N4S (M þ H)
m/z 601.2426, found 601.2421. Anal. Calcd for C40H32N4S: C,
79.97; H, 5.37; N, 9.33. Found: C, 79.63; H, 5.31; N, 9.12.
8-(5-(6-Butyl-6H-indolo[2,3-b]quinoxalin-9-yl)thiophene-2-yl)-
9,9-diethyl-N,N-diphenyl-9H-fluoren-1-amine (8). Compound 8
was obtained in 79% yield as a red solid from 9,9-diethyl-N,N-
diphenyl-7-(5-(tributylstannyl)thiophene-2-yl)-9H-fluoren-2-amine25
and 9-bromo-6-butyl-6H-indolo[2,3-b]quinoxaline as described
above: mp 195 °C; 1H NMR (400 MHz, CDCl3) δ0.41 (t, J=7.3Hz,
3H), 0.98 (t, J = 7.4 Hz, 3H), 1.44 (sext, J = 7.6 Hz, 2H),
1.91-2.02 (m, 6H), 4.48 (t, J = 7.2 Hz, 2H), 6.98-7.05 (m, 3H),
7.10-7.14 (m, 5H), 7.23-7.27 (m, 4H), 7.36-7.39 (m, 2H), 7.46
(d, J = 8.5 Hz, 1H), 7.55-7.57 (m, 2H), 7.61 (s, 2H), 7.65-7.73
(m, 1H), 7.73-7.77 (m, 1H), 8.12-8.14 (dd, J = 8.4 Hz, 1.2 Hz,
1H) 8.29-8.32 (dd, J = 8.4 Hz, 1.3 Hz, 1H). 8.74 (d, J = 1.8 Hz,
1H); 13C NMR (125 MHz, CDCl3) δ 8.5, 13.7, 20.2, 30.5, 32.6,
41.2, 56.0, 109.8, 119.15, 119.21, 119.3, 119.6, 119.8, 120.2, 122.4,
123.6, 123.7, 124.4, 125.9, 127.5, 127.7, 128.5, 128.8, 129.4, 129.2,
132.2, 136.0, 139.2, 139.7, 140.6, 140.8, 142.8, 143.5, 143.8, 145.8,
147.1, 147.8, 150.5, 151.4; HRMS calcd for C51H45N4S (M þ H)
m/z 745.3365, found 745.3371. Anal. Calcd for C51H44N4S: C,
82.22; H, 5.95; N, 7.52. Found: C, 81.97; H, 5.81; N, 7.36.
Computational Methods. The ground-state geometry of the
compounds at the gas phase were optimized using the density
functional theory method with the B3LYP functional in con-
jugation with the basis set 6-31G(d,p) as implemented in the
Gaussian 09 package.29 The default options for the self-consis-
tent field (SCF) convergence and threshold limits in the optimi-
zation were used. The electronic transitions were calculated
using the time-dependent DFT (B3LYP) theory and the 6-31G
N-(Anthracen-9-yl)-6-butyl-N-phenyl-6H-indolo[2,3-b]quinoxalin-
1
9-amine (5): orange solid; yield 76%; mp 238 °C; H NMR (400
MHz, CDCl3) δ 1.01 (t, J = 7.4 Hz, 3H), 1.48 (sext, J = 7.6 Hz,
2H), 1.96 (quin, J = 7.4 Hz, 2H), 4.49 (t, J = 7.3 Hz, 2H), 7.05 (t,
J = 7.3 Hz, 1H), 7.16 (d, J = 8.1 Hz, 2H), 7.29-7.38 (m, 5H),
7.42-7.47 (m, 2H), 7.59-7.63 (m, 2H), 7.70-7.74 (td, J = 6.9 Hz,
1.2 Hz, 1H), 7.82-7.88 (m, 2H), 7.92-7.94 (m, 1H), 8.07 (s, 1H),
8.12 (d, J = 8.5 Hz, 1H), 8.18 (d, J = 8.4 Hz, 1H) 8.30-8.34 (m,
2H); 13C NMR (125 MHz, CDCl3) δ 13.7, 20.2, 30.6, 41.2, 110.3,
117.2, 120.2, 122.7, 123.8, 124,1, 124.2, 124.4, 125.75, 125.81,
127.5, 127.6, 128.0, 128.6, 129.0, 129.2, 129.7, 130.6, 132.0, 132.5,
139.0, 139.5, 140.6, 141.1, 141.3, 145.2, 147.8; HRMS calcd for
C38H31N4 (M þ H) m/z 543.2549, found 543.2549. Anal. Calcd for
8110 J. Org. Chem. Vol. 75, No. 23, 2010