6846
B. A. D. Neto et al. / Tetrahedron Letters 46 (2005) 6843–6846
Z.; Wisnoski, D. D.; Wokenberg, S. E.; Leister, W. H.;
Wang, Y.; Lindsley, C. W. Tetrahedron Lett. 2004, 45,
4873.
Br
Br
Br
O
NH2
NH2
N
N
H
2NaHSO3
H
6. Ong, C. W.; Liao, S. C.; Chang, T. H.; Hsu, H. F. J. Org.
Chem. 2004, 69, 3181.
7. Suzuki, T.; Okubo, T.; Okada, A.; Yamashita, Y.;
Miyashi, T. Heterocycles 1993, 35, 395.
8. Consorti, C. S.; Ebeling, G.; Rodembusch, F.; Stefani, V.;
Livotto, P. R.; Rominger, F.; Quina, F. H.; Yihwa, C.;
Dupont, J. Inorg. Chem. 2004, 43, 530.
9. Compound 1a was synthesized accordingto literature:
Pesin, V. G.; Khaletskii, A. M.; Chzi-chzhun, C. J. Gen.
Chem. (USSR), Engl. Transl. 1957, 27, 1648.
O
EtOH
Br
7
2a
Scheme 4. Cyclization of diamine 2a to form the stable quinoxaline 7.
the synthesis of photoluminescent compounds. In addi-
tion, like other sulfur extrusion reactions,17 this one
should also be useful in the chemistry of aromatic
alkaloids.
10. Corey, E. J.; Kuhnle, F. N. M. Tetrahedron Lett. 1997, 38,
¨
8631.
11. (a) Ganem, B.; Heinzman, S. W. J. Am. Chem. Soc. 1982,
104, 6801; (b) McManis, J. S.; Ganem, B. J. Org. Chem.
1980, 45, 2041; (c) Osby, J. O.; Heinzman, S. W.; Ganem,
B. J. Am. Chem. Soc. 1986, 108, 67.
12. Baird, D. B.; Baxter, I.; Cameron, D. W.; Phillips, W. R.
J. Chem. Soc. Chem. Commum. 1971, 31.
Acknowledgements
13. General procedure for sulfur extrusion reaction: 2,1,3-
Benzothiadiazole 1 (1–10 mmol) and EtOH (150 mL, no
previous solvent treatment was required) were charged into
a 500 mL flask. NaBH4 (1–10 mmol) was added, followed
by CoCl2Æ6H2O (1 mol %). Black solid Co2B was formed
instantly and, in a few minutes, H2S evolution was noted.
The mixture was refluxed for 3 h, cooled to room temper-
ature and then filtered to separate the black solid. The
solvent was evaporated, water (100 mL) was added and
the organic product was extracted with Et2O (3 · 30 mL).
The combined organic extracts were dried over Na2CO3
and the solvent removed, resultingin the very air-unstable
diamine product 2. If necessary, the product can be chro-
matographed on alumina (neutral), eluting with Et2O. If
the solubility of the 2,1,3-benzothiadiazole 1 in EtOH is not
satisfactory, THF can be added (THF/EtOH 1:3), without
This work was sponsored by grants from Conselho
´
´
Nacional de Desenvolvimento Cientıfico e Tecnogico
`
(CNPq—Brazil) and Fundac¸ao de Amparo a Pesquisa
˜
do Estado do Rio Grande do Sul (FAPERGS).
B.A.D.N., A.S.L. and M.W. also thank the CNPq for
fellowships. We also thank Professor Frank H. Quina,
from IQ-USP, for a critical readingof the manuscript.
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2
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