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M. Tokunaga et al. / Tetrahedron Letters 42 (2001) 3865–3868
4. (a) Mo¨hlau, R. Chem. Ber. 1881, 14, 171; (b) Bischler, A.
indole formation (140°C) whereas it showed low activity
for the first amination step (100°C).
Chem. Ber. 1892, 25, 2860.
5. Brown, R. K. Indoles, Part I; Houlihan, W. J., Ed.; John
13. Typical procedure: A round-bottomed flask was charged
with [Ru3(CO)12] (16.0 mg, 0.025 mmol), aniline (559 mg,
6.0 mmol), aniline hydrochloride (129.6 mg, 1.0 mmol),
and 3-butyn-2-ol (631 mg, 9.0 mmol) and was then stirred
at 140°C for 8 h. After cooling, the product was sepa-
rated by silica-gel column chromatography (hexane–
CH2Cl2 4:1 then 1:1). Special care does not need to be
taken to remove air and moisture from the system. In the
case of solid substrate, ethylene glycol was used as the
solvent. When the reaction gave a mixture of two
regioisomeric indoles, crude product was isolated to
determine its ratio by 13C NMR (NNE mode; gated
decoupling without NOE), representative signal: l 8.0–
9.7 (3-Me), 10.6–11.7 (2-Me).
Wiley & Sons: New York, 1972; p. 317.
6. Most synthetic applications have been for 2-arylindoles
from anilines and a-halo acetophenone derivatives. See
Ref. 1, p. 77.
7. (a) De Kimpe, N.; Verhe´, R. In The Chemistry of h-
Haloketones, h-Haloaldehydes and h-Haloimines; Rappo-
port, Z.; Patai, S., Eds.; John Wily & Sons: Chichester,
1988; p. 121; (b) March, J. In Advanced Organic Chem-
istry, 4th ed.; John Wily & Sons: New York, 1992; p. 587.
8. (a) Pindur, U.; Adam, R. J. Heterocyclic Chem. 1988, 25,
1; (b) Takeda, A.; Kamijo, S.; Yamamoto, Y. J. Am.
Chem. Soc. 2000, 122, 5662; (c) Tokuyama, H.;
Yamashita, T.; Reding, M. T.; Kaburagi, Y.; Fukuyama,
T. J. Am. Chem. Soc. 1999, 121, 3791; (d) Fu¨rstner, A.;
Hupperts, A. J. Am. Chem. Soc. 1995, 117, 4468; (e)
Larock, R. C.; Yun, E. K.; Refvik, M. J. Org. Chem.
1998, 63, 7652; (f) Chen, C.-Y.; Lieberman, D. R.;
Larsen, R. D.; Verhoeven, T. R.; Reider, P. J. J. Org.
Chem. 1997, 62, 2676; (g) Sakamoto, T.; Kondo, Y.;
Yamanaka, H. Heterocycles 1988, 27, 2225; (h) Hegedus,
L. S. Angew. Chem., Int. Ed. Engl. 1988, 27, 1113.
9. Tokunaga, M.; Eckert, M.; Wakatsuki, Y. Angew. Chem.,
Int. Ed. 1999, 38, 3222.
14. (a) Campbell, N.; McCall, E. B. J. Chem. Soc. 1950,
2870; (b) Cummins, J. A.; Tomlinson, M. L. J. Chem.
Soc. 1955, 3475.
15. All indole products in this study are known and have
1
been characterized by H and 13C NMR. All compounds
gave satisfactory elemental analysis except for 3c and 3f,
whose GC/MS spectrum were identical.
16. Without additives, the same ratio of Ia-1/Ia-2 was recov-
ered after heating at 140°C for 5 min.
17. (a) Janetzky, E. F. J.; Verkade, P. E. Rec. Trav. Chim.
Pays-Bas 1946, 65, 905; (b) Julian, P. L.; Meyer, E. W.;
Magnani, A.; Cole, W. J. Am. Chem. Soc. 1945, 67, 1203.
18. Tokunaga, M.; Wakatsuki, Y. Japan Patent, Application
No. 2000-216457.
10. For a recent review of hydroamination, see: Mu¨ller, T.
E.; Beller, M. Chem. Rev. 1998, 98, 675.
11. In these catalytic hydroamination reactions, a small
amount of additive (NH4PF6) was crucial. See Ref. 9.
12. [RuCl2(PPh)3] exhibited similar activity on this one-pot
.