C O M M U N I C A T I O N S
Table 1. [RuCl2(CO)3]2/dppp-Catalyzed Oxidative Amination of
References
Aminoalkenesa
(1) (a) Taube, R. In Applied Homogeneous Catalysis with Organometallic
Compounds; Cornils, B., Herrmann, W. A., Eds.; VCH: New York, 1996;
Vol. 1, p 507. (b) Mu¨ller, T. E.; Beller, M. In Transition Metals for
Organic Synthesis; Beller, M., Bolm, C., Eds.; Wiley-VCH: New York,
1998; Vol. 2, p 316.
(2) For recent examples of intramolecular hydroamination, see: (a) Mu¨ller,
T. E.; Grosche, M.; Herdtweck, E.; Pleier, A.-K.; Walter, E.; Yan, Y.-K.
Organometallics 2000, 19, 170. (b) Burling, S.; Field, L. D.; Messerle,
B. A. Organometallics 2000, 19, 87. (c) Mu¨ller, T. E.; Pleier, A.-K. J.
Chem. Soc., Dalton Trans. 1999, 583. For recent examples of intermo-
lecular hydroamination, see: (d) Lo¨ber, O.; Kawatsura, M.; Hartwig J. F.
J. Am. Chem. Soc. 2001, 123, 4366. (e) Johnson, J. S.; Bergman R. G. J.
Am. Chem. Soc. 2001, 123, 2923. (f) Tokunaga, M.; Eckert, M.; Wakatsuki,
Y. Angew. Chem., Int. Ed. 1999, 38, 3222. (g) Uchimaru, Y. Chem.
Commun. 1999, 1133. (h) Casalnuovo, A. L.; Calabrese, J. C.; Milstein,
D. J. Am. Chem. Soc. 1988, 110, 6738.
(3) (a) Li, Y.; Marks, T. J. J. Am. Chem. Soc. 1998, 120, 1757. (b) Bu¨rgstein,
M. R.; Berberich, H.; Roesky, P. W. Organometallics 1998, 17, 1452.
(c) Li, Y.; Marks, T. J. J. Am. Chem. Soc. 1996, 118, 9295. (d) Haskel,
A.; Straub, T.; Eisen, M. S. Organometallics 1996, 15, 3773.
(4) (a) Vogels, C. M.; Hayes, P. G.; Shaver, M. P.; Westcott, S. A. Chem.
Commun. 2000, 51. (b) Tamaru, Y.; Hojo, M.; Kawamura, S.; Yoshida,
Z. J. Org. Chem. 1986, 51, 4090. For the stoichiometric reaction under
acidic reaction conditions, see: (c) Heathcock, C. H.; Stafford, J. A.; Clark,
D. L. J. Org. Chem. 1992, 57, 2575. (d) Pugin, B.; Venanzi, L. M. J.
Organomet. Chem. 1981, 214, 125. (e) Ambuehl, J.; Pregosin, P. S.;
Venanzi, L. M. J. Organomet. Chem. 1978, 160, 329.
(5) (a) Molander, G. A.; Dowdy, E. D. J. Org. Chem. 1998, 63, 8983. (b)
Roesky, P. W.; Stern, C. L.; Marks, T. J. Organometallics 1997, 16, 4705.
(c) Li, Y.; Marks, T. J. Organometallics 1996, 15, 3770. (d) Giardello,
M. A.; Conticello, V. P.; Brard, L.; Gagne´, M. R.; Marks, T. J. J. Am.
Chem. Soc. 1994, 116, 10241. (e) Gagne´, M. R.; Stern, C. L.; Marks, T.
J. J. Am. Chem. Soc. 1992, 114, 275. (f) Gagne´, M. R.; Marks, T. J. J.
Am. Chem. Soc. 1989, 111, 4108.
(6) (a) Tillack, A.; Trauthwein, H.; Hartung, C. G.; Eichberger, M.; Pitter,
S.; Jansen, A.; Beller, M. Monatsh. Chem. 2000, 131, 1327. (b) Beller,
M.; Trauthwein, H.; Eichberger, M.; Breindl, C.; Mu¨ller, T. E. Eur. J.
Inorg. Chem. 1999, 1121. (c) Beller, M.; Trauthwein, H.; Eichberger, M.;
Breindl, C.; Herwig, J.; Mu¨ller, T. E.; Thiel, O. R. Chem. Eur. J. 1999,
5, 1306. (d) Beller, M.; Trauthwein, H.; Eichberger, M.; Breindl, C.;
Mu¨ller, T. E.; Zapf, A. J. Organomet. Chem. 1998, 566, 277. (e) Ragaini,
F.; Longo, T.; Cenini, S. J. Mol. Catal. A: Chemical 1996, 110, L171.
(f) Brunet, J.-J.; Neibecker, D.; Philippot, K. Tetrahedron Lett. 1993, 34,
3877. (g) Hosokawa, T.; Takano, M.; Kuroki, Y.; Murahashi, S.-I.
Tetrahedron Lett. 1992, 33, 6643. (h) Bozell, J. J.; Hegedus, L. S. J. Org.
Chem. 1981, 46, 2561. (i) Graunt, M. J.; Spencer, J. B. Org. Lett. 2001,
3, 25. (j) Srivastava, R. S.; Nicholas, K. M. Chem. Commun. 1996, 2335.
(7) A few examples of oxidative cyclization/isomerization of aminoalkenes
have been reported. All reactions require a tosyl substituent on an amino
group. (a) Larock, R. C.; Hightower, T. R.; Hasvold, L. A.; Peterson, K.
P. J. Org. Chem. 1996, 61, 3584. (b) Ro¨nn, M.; Ba¨ckvall, J.-E.; Andersson,
P. G. Tetrahedron Lett. 1995, 36, 7749. (c) van Benthem, R. A. T. M.;
Hiemstra, H.; Longarela, G. R.; Speckamp, W. N. Tetrahedron Lett. 1994,
35, 9281. (d) Hegedus, L. S.; McKearin, J. M. J. Am. Chem. Soc. 1982,
104, 2444.
(8) (a) Hegedus, L. S. Angew. Chem., Int. Ed. Engl. 1988, 27, 1113 and
references therein. (b) Krolski, M. E.; Renaldo, A. F.; Rudisill, D. E.;
Stille, J. K. J. Org. Chem. 1988, 53, 1170.
(9) (a) Suzuki, T.; Shiotsuki, M.; Wada, K.; Kondo, T.; Mitsudo, T. J. Chem.
Soc., Dalton Trans. 1999, 4231. (b) Suzuki, T.; Shiotsuki, M.; Wada, K.;
Kondo, T.; Mitsudo, T. Organometallics 1999, 18, 3671.
(10) (a) Kondo, T.; Tanaka, A.; Kotachi, S.; Watanabe, Y. J. Chem. Soc., Chem.
Commun. 1995, 413. (b) Kondo, T.; Okada, T.; Suzuki, T.; Mitsudo, T.
J. Organomet. Chem. 2001, 622, 149.
(11) (a) Kondo, T.; Mukai T.; Watanabe, Y. J. Org. Chem. 1991, 56, 487. (b)
Kondo, T.; Kodoi, K.; Mitsudo, T.; Watanabe Y. J. Chem. Soc., Chem.
Commun. 1994, 755.
(12) It has been pointed out that ruthenium-catalyzed reactions require highly
careful tuning of reaction conditions with substrates to obtain products in
high yields and selectivities. N-Methylpiperidine was found to be the best
solvent for some ruthenium-catalyzed reactions, and may act as a suitable
ligand for an active ruthenium species as well as a simple solvent. See:
Mitsudo, T.; Kondo, T. Synlett 2001, 309 and references therein.
(13) (a) Eliel, E. L.; Wilen, S. H.; Mander, L. N. Stereochemistry of Organic
Compounds; John Wiley & Sons: New York, 1994; Vol. 11.3c, p 682.
(b) Kirby, A. AdV. Phys. Org. Chem. 1980, 17, 183.
(14) Sappa, E.; Milone, L. J. Organomet. Chem. 1973, 61, 383.
(15) (a) Cowan, R. L.; Trogler, W. C. Organometallics 1987, 6, 2451. (b)
Cowan, R. L.; Trogler, W. C. J. Am. Chem. Soc. 1989, 111, 4750.
a Aminoalkene (2.5 mmol), [RuCl2(CO)3]2 (0.050 mmol), dppp (0.10
mmol), K2CO3 (5.0 mmol), allyl acetate (7.5 mmol), and N-methylpiperidine
(4.0 mL) at 140 °C for 8 h under an argon atmosphere. b Determined by
1
GLC (isolated yield). c Determined by H NMR. d At 120 °C for 22 h.
Considering all of our findings, the most plausible mechanism
is as follows. The initial step might consist of the predominant
coordination and oxidative addition of the amine functionality in
aminoalkenes (1) to a coordinatively unsaturated active ruthenium
center to produce a (hydrido)(amido)ruthenium intermediate.14 The
“Thorpe-Ingold effect”13 and the formation of a nitrile as a
byproduct in the present reaction strongly suggest this direct N-H
bond activation/olefin insertion mechanism (vide supra). Neither
conversion of aminoalkenes to the corresponding tosylamides7 nor
acidic reaction conditions4c-e to decrease the coordination ability
of an amine functionality to less than an alkene moiety in
aminoalkenes was needed in the present reaction, which also
supports this mechanism. Subsequently, insertion of an alkene
moiety into the Ru-N bond15 followed by â-hydride elimination
and sequential reductive elimination16/isomerization gives the
corresponding cyclic imine with the formation of a ruthenium
dihydride intermediate, which regenerates a catalytically active
ruthenium species via removal of the hydride by hydrogenolysis
of allyl acetate (vide supra).
In conclusion, we have developed the practically useful ruthenium-
catalyzed intramolecular oxidative amination of aminoalkenes. This
process provides an effective and straightforward method for the
catalytic synthesis of unsaturated nitrogen heterocycles such as
1-pyrroline and indole derivatives without the use of expensive
aminoalkynes.
Acknowledgment. This work was supported in part by a Grant-
in-Aid for Scientific Research from the Japan Society for the
Promotion of Science (JSPS). T.K. acknowledges financial support
from the Sumitomo Foundation and Yamada Science Foundation.
T.O. appreciates Research Fellowships from the Japan Society for
the Promotion of Science for Young Scientists.
Supporting Information Available: Complete experimental pro-
cedures, lists of spectral data, and elemental analyses for all of the
new compounds (PDF). This material is available free of charge via
(16) (a) Baranano, D.; Hartwig, J. F. J. Am. Chem. Soc. 1995, 117, 2937. (b)
Hartwig, J. F. Angew. Chem., Int. Ed. 1998, 37, 2046.
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