of Ni-based catalysts are their much lower cost and increased
reactivity toward readily available and inexpensive aryl chlo-
rides.10 In Ni-catalyzed cross-couplings, both Ni(0) and Ni(II)
reagents are employed as Ni catalyst sources, but the Ni(0)
species is generally regarded as being catalytically active.
Although utilizing Ni(0) reagents, such as Ni(COD)2, Ni(PPh3)4,
etc., as catalysts is the simplest and most direct route, such nickel
sources would be difficult to handle and manipulate because of
their high air sensitivity and thermal instability. By contrast,
Ni(II) compounds, readily available and conveniently handled,
as pre-catalysts are more preferred from a practical point of
view. Certainly, the Ni(II) as pre-catalyst needs to first be
activated (i.e, converted in situ to zerovalent nickel) in reaction
systems because the active Ni(0) species is essential for
Ni-catalyzed processes. Different from the Pd(II), however, the
added ligands, solvents, or bases in reaction systems are
normally insufficient to reduce Ni(II) to Ni(0).11 In some
coupling reactions with organometallic reagents as partners, such
as the Kumada-Corriu reaction,5 Negishi reaction,6 and Suzuki
reaction,7f-i Ni(0) species could be formed from the Ni(II) via
the homocoupling of the organometals used. However, for the
other processes not involving the organometals (e.g., typically
in the Ni(II)-catalyzed arylamination), in situ generation of Ni-
(0) species would be problematic. Therefore the treatment of
Ni(II) precatalysts with external reductants has been an inevi-
table step. The reported modes included addition of zinc dust7a,b
and pretreatment of butyllithium or the Grignard reagent7c-e
and NaH.8d-h Also, the Ni(0)-on-charcoal from Ni(II) pretreated
with n-BuLi was elaborated for the C-C6e,7jand C-N8c
couplings.
Ni(II)-(σ-Aryl) Complex: A Facile, Efficient
Catalyst for Nickel-Catalyzed Carbon-Nitrogen
Coupling Reactions
Chen Chen†,‡ and Lian-Ming Yang*,†
Beijing National Laboratory For Molecular Sciences (BNLMS),
Laboratory of New Materials, Institute of Chemistry, Chinese
Academy of Sciences, Beijing 100080, China, and Graduate
School of Chinese Academy of Sciences, Beijing 100049, China
ReceiVed May 19, 2007
trans-Haloarylbis(triphenylphosphine)nickel(II), a type of air-
and moisture-stable Ni(II)-(σ-aryl) complex, was examined
as catalyst precursor in the C-N coupling reaction. This type
of Ni(II) pre-catalyst, associated with N-heterocyclic carbene
ligands, is found to easily produce the catalytically active
Ni(0) species in situ without the aid of external reductants
and allows for the efficient amination of aryl chlorides with
secondary cyclic amines and anilines under mild conditions.
Recently we were interested in exploring new Ni(II)-catalyzed
protocols for C-N bond-forming reactions, where the use of
external reducing agents would be obviated. A type of isolatable
trans-haloarylbis(triphenylphosphane)nickel(II) attracted our
great attention. An intensive investigation of Ni(II)-(σ-aryl)
Nickel-catalyzed carbon-carbon1-7 and carbon-nitrogen8
bond-forming reactions have become important and powerful
tools in organic syntheses during the past decades. Compared
to the corresponding Pd catalyst systems,9 the major advantages
(7) For the Suzuki reaction, see: (a) Percec, V.; Bae, J-Y.; Hill, D. H.
J. Org. Chem. 1995, 60, 1060-1065. (b) Galland, J.-C.; Savignac, M.;
Geneˆt, J.-P. Tetrahedron Lett. 1999, 40, 2323-2326. (c) Saito, S.; Sakai,
M.; Miyaura, N. Tetrahedron Lett. 1996, 37, 2993-2996. (d) Saito, S.;
Oh-tani, S.; Miyaura, N. J. Org. Chem. 1997, 62, 8024-8030. (e) Tang,
Z.-Y.; Hu, Q.-S. J. Org. Chem. 2006, 71, 2167-2169. (f) Indolese, A. F.
Tetrahedron Lett. 1997, 38, 3513-3516. (g) Inada, K.; Miyaura, N.
Tetrahedron 2000, 56, 8657-8660. (h) Zim, D.; Lando, V. R.; Dupont, J.;
Monterio, A. L. Org. Lett. 2001, 3, 3049-3051. (i) Percec, V.; Golding,
G. M.; Smidrkal, J.; Weichold, O. J. Org. Chem. 2004, 69, 3447-3452. (j)
Lipshutz, B. H.; Sclafani, J. A.; Blomgren, P. A. Tetrahedron 2000, 56,
2139-2144.
(8) (a) Wolfe, J. P.; Buchwald, S. L. J. Am. Chem. Soc. 1997, 119, 6054-
6058. (b) Bolm, C.; Hildebrand, J. P.; Rudolph, J. Synthesis 2000, 7, 911-
913. (c) Lipshutz, B. H.; Ueda, H. Angew. Chem., Int. Ed. 2000, 39, 4492-
4494. (d) Brenner, E.; Fort, Y. Tetrahedron Lett. 1998, 39, 5359-5362.
(e) Brenner, E.; Schneider, R.; Fort, Y. Tetrahedron 1999, 55, 12829-
12842. (f) Desmarets, C.; Schneider, R.; Fort, Y. Tetrahedron Lett. 2000,
41, 2875-2879. (g) Gradel, B.; Brenner, E.; Schneider, R.; Fort, Y.
Tetrahedron Lett. 2001, 42, 5689-5692. (h) Desmarets, C.; Schneider, R.;
Fort, Y. J. Org. Chem. 2002, 67, 3029-3036.
(9) For comprehensive reviews on Pd-catalyzed cross-coupling reactions,
see: (a) Tsuji, J. Palladium Reagents and Catalysts: New PerspectiVes
for the 21st Century; John Wiley & Sons: New York, 2004. (b) Topics in
Current Chemistry; Miyaura, N., Ed.; Springer-Verlag: Berlin, 2002; Vol.
219
(10) Fu, G. C.; Littke, A. F. Angew. Chem., Int. Ed. 2002, 41, 4176-
4211.
(11) Only one example has been reported where Ni(II)-nickelocene as
pre-catalyst was reduced to Ni(0) by PR3 (R ) Ph, Cl, or OiPr) for C-C
coupling; see: Leadbeater, N. E. J. Org. Chem. 2001, 66, 7539-7541.
† Institute of Chemistry, Chinese Academy of Sciences.
‡ Graduate School of Chinese Academy of Sciences.
(1) For the Heck reaction, see: (a) Heck, R. F.; Nolley, J. P. J. Org.
Chem. 1972, 14, 2320-2322. (b) Beletskaya, I. P.; Cheprakov, A. V. Chem.
ReV. 2000, 100, 3009-3066.
(2) For the Sonogashira reaction, see: (a) Beletskaya, I. P.; Latyshev,
G. V.; Tsvetkov, A. V.; Lukashev, N. V. Tetrahedron Lett. 2003, 44, 5011-
5013. (b) Wang, L.; Li, P.; Zhang, Y. Chem. Commun. 2004, 514-515.
(3) For the Still reaction, see: (a) Kosugi, M.; Fugami, K. J. Organomet.
Chem. 2002, 653, 50-53. (b) Shirakawa, E.; Yamasaki, K.; Hiyama, T. J.
Chem. Soc., Perkin Trans. 1 1997, 2449-2450. (c) Kang, S.; Ryu, H.; Lee,
S. J. Chem. Soc., Perkin Trans. 1 1999, 2661-2663.
(4) For the Ullmann reaction, see: (a) Takagi, K.; Hayama, N.; Inokawa,
S. Bull. Chem. Soc. Jpn. 1980, 53, 3691-3695. (b) Takagi, K.; Hayama,
N. Chem. Lett. 1983, 12, 637-638. (c) Lin, G. Q.; Hong, R. J. Org. Chem.
2001, 66, 2877-2880.
(5) For the Kumada-Corriu reaction, see: (a) Tamao, K.; Sumitani, K.;
Kumada, M. J. Am. Chem. Soc. 1972, 94, 4374-4376. (b) Corriu, R. J. P.;
Masse, J. P. Chem. Commun. 1972, 144. (c) Bohm, V. P. W.; Weskamp,
T.; Gstottmayr, C. W. K.; Hermann, W. A. Angew. Chem., Int. Ed. 2000,
39, 1602-1604. (d) Terao, J.; Watanabe, H.; Kambe, N. J. Am. Chem. Soc.
2005, 127, 3656-3657. (e) Yoshikai, N.; Mashima, H.; Nakamura, E. J.
Am. Chem. Soc. 2005, 127, 17978-17979.
(6) For the Negishi reaction, see: (a) Knochel, P.; Dohle, W.; Gom-
mermann, N.; Kneisel, F. F.; Kopp, F.; Korn, T.; Sapountzis, I.; Vu, V. A.
Angew. Chem., Int. Ed. 2003, 42, 4302-4320. (b) Gavryushin, A.; Kofink,
C.; Manolikakes, G.; Knochel, P. Org. Lett. 2005, 7, 4871-4874. (c)
Lipshutz, B. H.; Blomgren, P. A. J. Am. Chem. Soc. 1999, 121, 5819-
5820.
10.1021/jo0709448 CCC: $37.00 © 2007 American Chemical Society
Published on Web 07/11/2007
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