reactive yet,11 at the same time, the cheapest and most
widely available among the aryl halides. Nickel complexes
bearing either P-2c,12 or C-based13 (N-heterocyclic carbenes,
NHCs) ligands accomplish such transformations even at
room temperature. Moreover, phenol-derived electrophiles
represent an attractive low cost alternative to organic
halides in cross-coupling processes.14 However, these sub-
strates are even more challenging to activate since the bond
dissociation energy (BDE) of the CArꢀO bond is higher
than that of the corresponding CArꢀCl.14a Not surprisingly,
recent outstanding examples of the activation of CArꢀO in
different cross-coupling reactions have been addressed by
using nickel-based catalysts stabilized with electron-rich and
sterically demanding phosphane or carbene ligands.15
Recently, we have described the first examples of room
temperature nickel-catalyzed amination of aryl and het-
eroaryl chlorides.16 These couplings were performed in the
presence of the well-defined complex (IPr)Ni(π-allyl)Cl.17
As continuation of this work, we report herein that this
catalytic system is highly active in KTC couplings with
heteroaryl chlorides. Furthermore, this complex also effec-
tively promotes the cross-coupling of aromatic Grignard
reagents with anisoles under fairly mild reaction conditions.
reaction of 4-chlorotoluene with phenylmagnesium bro-
mide, using 5 mol % of the Ni(II) precatalysts at room
temperature. The results obtained are summarized in
Table 1. We encountered significant differences in the
catalytic behavior of these NHCꢀNi(II) complexes under
the conditions employed. The reactions catalyzed by com-
plexes 1 and 2 afforded moderate yields of the desired
product together with considerable amounts of the homo-
coupling byproduct (entries 1 and 2). Conversely, deriva-
tive 3 promoted a highly selective reaction exclusively
furnishing 4-methylbiphenyl in 75% yield (entry 3). Finally,
the most bulky ItBu18 also suppressed the byproduct for-
mation, but complex 4 exhibited lower catalytic activity
(entry 4) compared with that of the IPr-derivative, 3.
Table 1. Screening of Nickel Complexes 1ꢀ4a
yieldb (%)
entry
catalyst
7
8
1
2
3
4
(IMes)Ni(allyl)Cl (1)
(SIPr)Ni(allyl)Cl (2)
(IPr)Ni(allyl)Cl (3)
(ItBu)Ni(allyl)Cl (4)
48
50
75
65
10
19
0
0
a Reaction conditions: aryl chloride (0.5 mmol), PhMgBr (0.75
mmol), nickel complex (5 mol %), total volume of THF (1 mL).
b Isolated product yield.
Once complex 3 was identified as the most active catalyst,
we tested it in the KTC reaction of heteroaryl chlorides as
Figure 1. Nickel(II) complexes employed in this work.
(15) (a) See 14a and references therein. (b) Tobisu, M.; Shimasaki, T.;
Chatani, N. Angew. Chem., Int. Ed. 2008, 47, 4866. (b) Quasdorft, K. N.;
Tian, X.; Garg, N. K. J. Am. Chem. Soc. 2008, 130, 14442. (c) Quasdorft,
K. N.; Riener, M.; Petrova, K. V.; Garg, N. K. J. Am. Chem. Soc. 2009,
131, 17748. (d) Antoft-Finch, A.; Blackburn, Y.; Snieckus, V. J. Am.
Chem. Soc. 2009, 131, 17750. (e) Tobisu, M.; Shimasaki, T.; Chatani, N.
Chem. Lett. 2009, 38, 710. (f) Shimasaki, T.; Tobisu, M.; Chatani, N.
Angew. Chem., Int. Ed. 2010, 49, 2929. (g) Megasnaw, T.; Silberstein,
A. L.; Ramgren, S. D.; Nathel, N. N. F.; Hong, X.; Liu, P.; Garg, N. K.
Chem. Sci. 2011, 2, 1766. (h) Quasdorf, K, W.; Antoft-Finch, A.; Liu, P.;
Silberstein, A. L.; Komaromi, A.; Blackburn, T.; Ramgren, S. D.; Houk,
K. N.; Snieckus, V.; Garg, N. K. J. Am. Chem. Soc. 2011, 133, 6352.
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342, 1949.
(17) (a) Dible, B. R.; Sigman, M. S. J. Am. Chem. Soc. 2003, 125, 872.
(b) Dible, B. R.; Sigman, M. S. Inorg. Chem. 2006, 45, 8430.
(18) Cavallo, L.; Correa, A.; Costabile, C.; Jacobsen, H. J. Organo-
met. Chem. 2005, 690, 5407.
(19) For recent reviews on the use of heteroarenes in cross-coupling,
see: (a) Fairlamb, I. J. S. Chem. Soc. Rev. 2007, 36, 1036. (b) Slagt, V. F.;
de Vries, A. H. M.; de Vries, J. G.; Kellog, R. M. Org. Process Res. Dev.
2010, 14, 30.
We began by evaluating the catalytic activity of a series
of (NHC)Ni(allyl)Cl17 complexes (Figure 1) in the KTC
(11) Grushin, V. V.; Alper, H. Chem. Rev. 1994, 94, 1047.
(12) For recent examples, see: (a) Yoshikai, N.; Mashima, H.;
Nakamura, E. J. Am. Chem. Soc. 2005, 127, 17978. (b) Ackermann,
L.; Born, R.; Spatz, J. H.; Meyer, D. Angew. Chem., Int. Ed. 2005, 44,
7216. (c) Wang, Z.-X.; Wang, L. Chem. Commun. 2007, 2423. (d)
Yoshikai, N.; Matsuda, H.; Nakamura, E. J. Am. Chem. Soc. 2009,
131, 9590. (e) Xie, L.-G.; Wang, Z.-X. Chem.;Eur. J. 2010, 16, 10332.
(f) Ghosh, R.; Sarkar, A. J. Org. Chem. 2010, 75, 8283. (g) Monnereau,
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L.; Semeril, D.; Matt, D. Chem. Commun. 2011, 47, 6626. (h) Liu, N.;
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€
T.; Gstottmayr, C. W. K.; Herrmann, W. A. Angew. Chem., Int. Ed.
€
2000, 39, 1602. (b) Inamoto, K.; Kuroda, J.-i.; Sakamoto, T.; Hiroya, K.
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ꢀ
metals are quoted here: (a) Bonnet, V.; Mognin, F.; Trecourt, F.;
ꢀ
Queguiner, G.; Knochel, P. Tetrahedron Lett. 2001, 42, 5717. (b) Organ,
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