3742
I. C. F. R. Ferreira et al. / Tetrahedron 59 (2003) 3737–3743
IR: 3395 (N–H). 1H NMR: (CDCl3) 3.79 (3H, s, OMe), 6.00
(1H, broad s, N–H), 6.79 (1H, dd, J¼9 and 2.7 Hz, H-50),
6.95 (1H, s, H-2), 7.05 (1H, d, J¼9 Hz, H-60), 7.16 (1H, d,
J¼2.7 Hz, H-30), 7.38–7.42 (2H, m, 2£ArH), 7.66–7.69
(1H, m, ArH), 7.83–7.87 (1H, m, ArH). 13C NMR: (CDCl3)
55.88 (OCH3), 109.39, 112.02 (C), 114.57, 117.44, 117.91,
120.62, 123.20, 124.01, 124.95, 134.45 (C), 135.16 (C),
135.99 (C), 138.89 (C), 153.63 (C). MS: 335 (100, Mþ
81Br), 333 (96, Mþ 79Br), 320 (42, Mþ 81Br215), 318 (42,
N–H). 13C NMR: (CDCl3) 55.88 (OCH3), 101.16, 112.91,
113.36, 116.18 (C), 119.36, 122.78 (C), 124.13, 124.25,
124.41, 126.74 (C), 135.47 (C), 137.60 (C), 142.76 (C),
154.32 (C). MS: 253 (100, Mþ), 238 (20, Mþ215), 210
(48). Anal. Calcd for C15H11NOS: C 71.42, H 4.38, N 5.53,
S 12.66; found: C 71.09, H 4.31, N 5.55, S 12.30.
4.5.2. 8,9-Dimethoxy-6H-indolo[3,2-b]benzo[b]thiophene
(8b). From ortho-diarylamine 7b (0.10 g, 0.28 mmol)
compound 8b was obtained as a beje solid (46 mg, 60%),
mp 120–122. IR: 3406 (N–H). 1H NMR: (CDCl3
þ([D6]DMSO) 3.82 (3H, s, OMe), 3.83 (3H, s, OMe),
6.91 (1H, s, H-7), 7.03 (1H, s, H-10), 7.10–7.16 (1H, m, H-3
or 4), 7.21–7.27 (1H, m, H-4 or 3), 7.70 (1H, broad d,
J¼8 Hz, H-2 or 5), 7.79 (1H, broad d, J¼8 Hz, H-5 or 2),
10.60 (1H, s, N–H). 13C NMR: ([D6]DMSO) 55.79 (OCH3),
55.92 (OCH3), 95.44, 100.39, 114.45 (C), 114.74 (C),
119.03, 122.78, 123.67, 123.73, 126.99 (C), 134.99 (C),
136.13 (C), 141.55 (C), 144.22 (C), 147.01 (C). MS: 283
(100, Mþ), 268 (35, Mþ215). Anal. Calcd for C16H13NO2S
calcd C 67.82, H 4.62, N 4.94, S 11.31; found: C 67.44, H
4.94, N 4.95, S 10.88.
M
þ 79Br215), 254 (25, Mþ280), 239 (23), 223 (25), 210
(32). HRMS C15H12BrNOS calcd Mþ 79Br 333.98565;
found 333.98695.
4.4.2. 3-(2-Bromo-3,4-dimethoxyphenyl)aminobenzo-
[b]thiophene (7b). From 2-bromo-4,5-dimethoxyaniline
3b13 (0.50 g, 2.2 mmol), heating for 16 h and following
the general procedure, compound 7b was obtained as a
rosed solid after chromatographic purification (0.23 g,
30%). Crystallization from ether/petroleum ether gave
1
rosed crystals, mp 100–102. IR: 3413 (N–H). H NMR:
(CDCl3) 3.71 (3H, s, OMe), 3.87 (3H, s, OMe), 5.99 (1H, s,
N–H), 6.76 (1H, s, H-60), 6.97 (1H, s, H-2), 7.06 (1H, s,
H-30), 7.39–7.43 (2H, m, 2£ArH), 7.68–7.73 (1H, m, ArH),
7.84–7.88 (1H, m, ArH). 13C NMR: (CDCl3) 56.03
(OCH3), 56.59 (OCH3), 100.99 (C), 101.41, 109.19,
115.78, 120.66, 123.21, 124.05, 125.07, 134.40 (C),
135.12 (C), 135.99 (C), 138.89 (C), 143.38 (C), 149.26
(C). Anal. Calcd for C16H14BrNO2S: C 52.76, H 3.87, N
3.85, S 8.80; found: C 52.70, H 4.16, N 3.97, S 8.86.
4.5.3. 6H-Indolo[3,2-b]benzo[b]thiophene (8c). From
ortho-bromodiarylamine 7c (80 mg, 0.26 mmol) compound
8c was obtained as a white solid (58 mg, quantitative yield).
Crystallization from ether/petroleum ether gave colourless
1
crystals, mp 251–253 (lit14 250–252). H NMR: (CDCl3)
7.22–7.50 (4H, m, H-3,4, 8 and 9), 7.55 (1H, broad d,
J¼8 Hz, ArH), 7.79(1H, broad d, J¼8 Hz, ArH), 7.88 (1H,
broad d, J¼8 Hz, ArH), 7.92 (1H, broad d, J¼8 Hz, ArH),
8.60 (1H, s, N–H). 13C NMR: (CDCl3) 112.15, 116.59 (C),
119.33, 119.36, 120.22, 122.50 (C), 123.34, 124.14, 124.25,
124.43, 126.63 (C), 136.82 (C), 140.54 (C), 142.87 (C). MS:
223 (100, Mþ), 121 (11). HRMS C14H9NS: calcd Mþ
223.045571; found 223.045592.
4.4.3. 3-(2-Bromophenyl)aminobenzo[b]thiophene (7c).
From 2-bromoaniline 3c (0.50 g, 2.9 mmol), compound 7c
was obtained as an oil after chromatographic purification
(0.35 g, 40%). 1H NMR: (CDCl3) 6.30 (1H, s, N–H), 6.65–
6.75 (1H, m, ArH), 6.98 (1H, dd, J¼8.1 and 1.5 Hz, H-60),
7.10–7.17 (1H, m, ArH),7.18 (1H, s, H-2) 7.36–7.43 (2H,
m, 2£ArH), 7.55 (1H, dd, J¼8.1 and 1.5 Hz, H-30), 7.64–
7.67 (1H, m, ArH), 7.85–7.89 (1H, m, ArH). 13C NMR:
(CDCl3) 110.45 (C), 113.63, 114.78, 120.12, 120.90,
123.15, 124.11, 124.97, 128.31, 132.62, 133.51 (C),
134.84 (C), 138.74 (C), 142.37 (C). MS: 305 (70, Mþ
81Br), 303 (69, Mþ 79Br), 224 (75), 223 (100). HRMS
C14H10BrNS: calcd Mþ 81Br 305.97425; found 305.97304.
Acknowledgements
Thanks are due to Foundation for the Science and
Technology-IBQF-Univ. Minho (Portugal), to the Research
Incitment Programme of the Calouste Gulbenkian
Foundation (Portugal) for financial support and to Escola
4.5. General procedure for the intramolecular
cyclisation of ortho-bromodiarylamines 7 to indolo-
[3,2-b]benzo[b]thiophenes 8
´
Superior Agraria-Instituto Politecnico de Braganc¸a for
supporting in part Isabel C. F. R. Ferreira PhD.
´
ortho-Bromodiarylamines 7, Pd(OAc)2 (10%) and Na2CO3
(1.4 equiv.) were refluxed in dry DMF (4–5 ml), for 2 h.
The reaction was followed by TLC. After cooling, CHCl3
was added. The organic phase was separated, dried
(MgSO4), filtered and the solvent removed to give the
product which was submitted to crystallization using ether/
petroleum ether.
References
¨
1. Knolker, H-J.; Reddy, K. R. Chem. Rev. 2002, 102,
4303–4427.
2. Kirsch, G. H. Curr. Org. Chem. 2001, 5, 507–518.
3. (a) Thornerm, C. W. Chem. Soc. Rev. 1979, 8, 563–580.
(b) Patani, G. A.; LaVoie, E. J. Chem. Rev. 1996, 96,
3147–3176.
4.5.1. 9-Methoxy-6H-indolo[3,2-b]benzo[b]thiophene
(8a). From ortho-bromodiarylamine 7a (70 mg,
0.21 mmol) compound 8a was obtained as colourless
crystals (32 mg, 60%), mp 212–213.5. IR: 3420 (N–H).
1H NMR: (CDCl3) 3.93 (3H, s, OMe), 6.98 (1H, dd, J¼9
and 2.4 Hz, H-8), 7.23 (1H, d, J¼2.4 Hz, H-10), 7.33–7.46
(3H, m, 3£ArH), 7.82–7.92 (2H, m, 2£ArH), 8.46 (1H, s,
4. Ferreira, I. C. F. R.; Queiroz, M.-J. R. P.; Kirsch, G. J. Het.
Chem. 2001, 38, 749–754.
5. Ferreira, I. C. F. R.; Queiroz, M-J. R. P.; Kirsch, G.
Tetrahedron 2002, 58, 7943–7949, and references cited
therein.