LETTER
Catalytic Alkylation of Aromatic Amines
245
(9) Brunet, J.-J.; Neibecker, D.; Philippot, K. Tetrahedron Lett.
1993, 34, 3877.
(10) Beller, M.; Eichberger, M.; Trauthwein, H. Angew. Chem. Int.
Ed. Engl. 1997, 36, 2225.
to 2-(1-arylethyl)anilines which can be further exploited
for the synthesis of a wide range of heterocycles. Remark-
ably, the combination of both [Rh(cod)2]BF4 / 4 PPh3 (2.5
mol%) and HBF4◊OEt2 (20 mol%) is necessary to achieve
reactions of aniline and p-fluoroaniline. On the other hand
electron-rich anilines react already in the presence of
HBF4◊OEt2 (20 mol%) whereby the addition of
[Rh(cod)2]BF4 / 4 PPh3 (2.5 mol%) increases the yield of
alkylated anilines (exception p-anisidine at low styrene to
anisidine ratio). Extensions of rhodium-catalyzed reaction
of anilines with styrenes for the synthesis of quinoline het-
erocycles will be reported in due course.14
(11) Beller, M.; Trauthwein, H.; Eichberger, M.; Breindl, C.; Mül-
ler, T. E.; Thiel, O. R.; Herwig, Chem. Europ. J., in press.
(12) Typical experimental procedure: 45 mg (0.11 mmol)
[Rh(cod)2]BF4 and 116 mg (0.44 mmol) PPh3 were suspended
under argon in 5 ml toluene using a pressure tube as reaction
vessel. 0.4 ml (4.4 mmol) aniline and 2.52 ml (22 mmol) sty-
rene were added. After adding 120 µl (0.88 mmol) HBF4·OEt2
and hexadecane (GC-standard) the reaction mixture was heat-
ed for 20 h at 140 °C. Standard organic workup including
chromatography yielded the alkylation products.
All the new compounds were characterized by EA, MS, 1H-
NMR and 13C-NMR. Compound 2a: 1H-NMR (400 MHz,
CDCl3): δ = 7.20 - 7.07 (m, 5H), 6.82 (d, 4J(H,H) = 2.5 Hz,
1H), 6.58 (dd, 3J(H,H) = 8.5 Hz, 3J(H,H) = 2.5 Hz, 1H), 6.49
(d, 3J(H,H) = 8.5 Hz, 1H), 4.00 (q, 3J(H,H) = 7.0 Hz, 1H, CH),
3.69 (s, 3H), 3.03 (s, 2H, NH), 1.51 (d, 3J(H,H) = 7.0 Hz, 3H,
CH3); 13C-NMR (101 MHz, CDCl3): δ = 153.4, 145.8, 138.3,
132.3, 129.2, 127.9, 126.8, 117.6, 114.5, 112.1 , 56.1, 40.7,
22.2; MS (70 eV): 227 [M+], 212 [M+ - CH3], 197 [M+ - 2
CH3], 180. Compound 3a: 1H-NMR (400 MHz, CDCl3): δ =
7.19 - 7.07 (m, 5H,), 6.92 (dd, 3J(H,F) = 10.0 Hz, 4J(H,H) =
3.0 Hz, 1H), 6.68 (ddd, 3J(H,F) = 10.0 Hz, 3J(H,H) = 8.5 Hz,
4J(H,H) = 3.0 Hz, 1H), 6.44 (dd, 3J(H,H) = 8.5 Hz, 4J(H,F) =
5.0 Hz, 1H), 3.95 (q, 3J(H,H) = 7.0 Hz, 1H, CH), 3.21 (s, 2H,
NH), 1.48 (d, 3J(H,H) = 7.0 Hz, 3H, CH3); 13C-NMR (101
MHz, CDCl3): δ = 155.7 (d, 1J(C,F) = 236.2 Hz), 143.8, 139.1
(d, 4J(C,F) = 1.9 Hz), 130.7 (d, 4J(C,F) = 6.8 Hz), 127.8,
126.3, 125.6, 115.9 (d, 3J(C,F) = 7.7 Hz), 113.0 (d, 3J(C,F) =
22.3 Hz), 112.3 (d, 2J(C,F) = 22.4 Hz), 39.2, 20.7; MS (70
eV): 215 [M+], 200 [M+ - CH3], 185, 124, 109, 99, 77. Com-
pound 3b: 1H-NMR (400 MHz, CDCl3): δ = 7.26 - 7.20 (m,
4H), 7.12 (t, 3J(H,H) = 7.5 Hz, 1H), 6.69 (dd, 3J(H,F) = 9.0 Hz,
3J(H,H) = 8.5 Hz, 2H), 6.34 (dd, 3J(H,H) = 8.5 Hz, 4J(H,F) =
2.4 Hz, 2H), 4.31 (q, 3J(H,H) = 7.0 Hz, 1H, CH), 3.90 (s, 1H,
NH), 1.41 (d, 3J(H,H) = 7.0 Hz, 3H, CH3); 13C-NMR (101
MHz, CDCl3): δ = 155.0 (d, 1J(C,F) = 235.2 Hz), 142.7, 144.2,
125.1, 127.9, 126.3, 114.7 (d, 2J(C,F) = 22.4 Hz), 113.5 (d,
3J(C,F) = 7.8 Hz), 53.4, 24.2; MS (70 eV): 215 [M+], 200 [M+
- CH3], 120 [M+ - C6H5], 105, 93, 77.
Acknowledgement
This work was supported by the Deutsche Forschungsgemeinschaft
(Be 1931/3-1). Generous gifts of precious metals from Hereaus AG
and Degussa AG are gratefully acknowledged.
References and Notes
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nic Chemistry, Pergamon, Oxford, 1991, Vol. 2, p 733. d)
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(14) Beller, M.; Thiel, O. R.; Trauthwein, H. manuscript in prepa-
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Synlett 1999, No. 2, 243–245 ISSN 0936-5214 © Thieme Stuttgart · New York