4
Phosphine-Free Palladium(II)-Catalyzed
Arylation of Naphthalene and Benzene with Aryl
Iodides
group containing arenes, the intermolecular coupling of aryl
5
halides with simple arenes such as benzene in the absence of
directing groups still has been rarely reported. Herein, we
describe a Pd(OAc)2-catalyzed arylation of naphthalene or
benzene with various aryl iodides in the presence of CF3CO2Ag
in trifluoroethanol (TFE) or/and trifluoroacetic acid (TFA).
According to the previous reports on palladium-catalyzed
couplings of heteroaromatics with aryl halides, the arylations
Chunxia Qin and Wenjun Lu*
Department of Chemistry, Shanghai Jiao Tong UniVersity,
8
00 Dongchuan Road, Shanghai, 200240, China
0
/II
involve a Pd cycle, as shown in Scheme 1, and additional
reductants are necessary if the initial catalyst is a Pd(II)
2
0/II
complex. In this Pd cycle, the first arylpalladium(II) inter-
mediate I is formed through an oxidative addition of a Pd(0)
complex with an aryl halide. However, since only the aryl C-H
bond of heteroaromatics and directing-group assisted arenes
could be cleaved successfully by the intermediate I to give a
diarylpalladium(II) complex II under the reaction conditions,
ReceiVed June 21, 2008
the scope of this arylation is severely limited. To overcome this
II/IV
barrier, we propose a Pd
cycle for our intermolecular
arylation of simple arenes with aryl iodides as first suggested
in the ortho-alkylation of acetanilides with excess alkyl
7
a
4b,7b,c
II/IV
iodides, then applied in other arylations.
In the Pd
cycle, as shown in Scheme 1, the first step is the attack of a
highly electrophilic Pd(II) complex on a simple aryl C-H bond
to generate an arylpalladium(II) intermediate III under similar
reaction conditions in the cross-coupling of simple arenes via
double C-H bond activations we reported recently, followed
by an oxidative addition with an aryl halide to afford a
diarylpalladium(IV) complex IV.
A phosphine-free arylation of naphthalene and benzene with
aryl iodides to give biaryls in moderate to good yields is
6
carried out in the presence of catalytic Pd(OAc)
stoichiometric CF CO Ag in TFE or/and TFA.
2
and
3
2
In our initial investigation of the coupling of naphthalene (1a)
with p-iodonitrobenzene (2a), as shown in Table 1, the above
Formation of aryl-aryl bonds has been one of the most
important methods in organic synthesis since the Ullmann
reaction, a homocoupling of aryl halides with a stoichiometric
II/IV
hypothesis on Pd
cycle is partly supported. In the cases of
Pd/C and Pd(PPh3)4, no biaryl was found (Table 1, entries 5
and 6). In contrast, when Pd(OAc)2 was employed, trace
coupling products were detected by GC analysis (Table 1,entry
1
amount of copper, was discovered one century ago. A promis-
ing protocol of this chemistry, especially for yielding unsym-
metric biaryls, is the direct arylation of aromatic C-H bonds
with aryl halides in the presence of catalytic transition metals.
Although significant progress was achieved most recently in
1
%
6
). Notably, by loading Pd(II) or Pd(0) as the catalyst (5 mol
), the yields of arylation products could be up to 88% and
1% (Table 1, entries 4 and 7), respectively, after 1.2 equiv of
CF3CO2Ag was added into the reactions. This indicates that not
2
3
arylations of heteroaromatics, fluoroarenes, and directing-
II/IV
only Pd(II) can make the arylation occur but also a Pd
cycle
may be involved in the process. Moreover, CF3CO2Ag should
be necessary to keep the Pd(II) catalyst more active by either
Ag eliminating I to prevent forming an inactive PdI2
(
1) Reviews: (a) Bellina, F.; Cauteruccio, S.; Rossi, R. Curr. Org. Chem.
2
1
4
008, 12, 774. (b) Alberico, D.; Scott, M. E.; Lautens, M. Chem. ReV. 2007,
07, 174. (c) Campeau, L.-C.; Stuart, D. R.; Fagnou, K. Aldrichim. Acta 2007,
0, 35. (d) Satoh, T.; Miura, M. Chem. Lett. 2007, 36, 200. (e) Seregin, I. V.;
+
-
Gevorgyan, V. Chem. Soc. ReV. 2007, 36, 1173. (f) Godula, K.; Sames, D. Science
006, 312, 67. (g) Campeau, L.-C.; Fagnou, K. Chem. Commun. 2006, 1253.
h) Kakiuchi, F.; Chatani, N. AdV. Synth. Catal. 2003, 345, 1077. (i) Hassan, J.;
Sevignon, M.; Gozzi, C.; Shulz, E.; Lemaire, M. Chem. ReV. 2002, 102, 1359.
2) For recent arylation of heteroaromatics see: (a) Lebrasseur, N.; Larrosa,
2
(
(4) For recent ortho-arylation of various arenes see: (a) Campeau, L.-C.;
Schipper, D. J.; Fagnou, K. J. Am. Chem. Soc. 2008, 130, 3266. (b) Larivee, A.;
Mousseau, J. J.; Charette, A. B. J. Am. Chem. Soc. 2008, 130, 52. (c) Ackermann,
L.; Vicente, R.; Althammer, A. Org. Lett. 2008, 10, 2299. (d) Ozdemir, I.; Demir,
S. J. Am. Chem. Soc. 2008, 130, 1156. (e) Chiong, H. A.; Pham, Q.-N.; Daugulis,
O. J. Am. Chem. Soc. 2007, 129, 9879. (f) Shabashov, D.; Daugulis, O. J. Org.
Chem. 2007, 72, 7720. (g) Lazareva, A.; Daugulis, O. Org. Lett. 2006, 8, 5211.
(h) Giri, R.; Maugel, N.; Li, J.-J.; Wang, D.-H.; Breazzano, S. P.; Saunders,
L. B.; Yu, J.-Q. J. Am. Chem. Soc. 2007, 129, 3510.
(5) For arylation of benzene see: (a) Lafrance, M.; Fagnou, K. J. Am. Chem.
Soc. 2006, 128, 16496. (b) Fujita, K.-I.; Nonogawa, M.; Yamaguchi, R. Chem.
Commun. 2004, 1926. For arylation of azulene see: (c) Dyker, G.; Borowski,
S.; Heiermann, J.; K o¨ rning, J.; Opwis, K.; Henkel, G.; K o¨ ckerling, M. J.
Organomet. Chem. 2000, 606, 108.
(
I. J. Am. Chem. Soc. 2008, 130, 2926. (b) Fleageau, E. F.; Popkin, M. E.;
Greaney, M. F. Org. Lett. 2008, 10, 2717. (c) Martin, T.; Verrier, C.; Hoarau,
C.; Marsais, F. Org. Lett. 2008, 10, 2909. (d) Bellina, F.; Cauteruccio, S.; DiFiore,
A.; Marchetti, C.; Rossi, R. Tetrahedron 2008, 64, 6060. (e) Do, H.-Q.; Daugulis,
O. J. Am. Chem. Soc. 2007, 129, 12404. (f) Chiong, H. A.; Daugulis, O. Org.
Lett. 2007, 9, 1449. (g) Wang, X.; Gribkov, D. V.; Sames, D. J. Org. Chem.
2
007, 72, 1476. (h) Battace, A.; Lemhadri, M.; Zair, T.; Doucet, H.; Santelli,
M. Organometallics 2007, 26, 472. (i) Yanagisawa, S.; Sudo, T.; Noyori, R.;
Itami, K. J. Am. Chem. Soc. 2006, 128, 11748.
(
3) For arylation of fluoroarenes see: (a) Do, H.-Q.; Daugulis, O. J. Am.
Chem. Soc. 2008, 130, 1128. (b) Ozdemir, I.; Demir, S.; Cetinkaya, B.;
Gourlaouen, C.; Maseras, F.; Bruneau, C.; Dixneuf, P. H. J. Am. Chem. Soc.
(6) (a) Rong, Y.; Li, R.; Lu, W. Organometallics 2007, 26, 4376. (b) Li, R.;
Jiang, L.; Lu, W. Organometallics 2006, 25, 5973.
(7) (a) Tremont, S. J.; Rahman, H. J. Am. Chem. Soc. 1984, 106, 5759. (b)
Whitfield, S. R.; Sanford, M. S. J. Am. Chem. Soc. 2007, 129, 15142. (c) Kalyani,
D.; Deprez, N. R.; Desai, L. V.; Sanford, M. S. J. Am. Chem. Soc. 2005, 127,
7330.
2
008, 130, 1156. (c) Ackermann, L.; Vicente, R.; Althammer, A. Org. Lett. 2008,
1
0, 2299. (d) Shabashov, D.; Daugulis, O. J. Org. Chem. 2007, 72, 7720. (e)
Lafrance, M.; Rowley, C. N.; Woo, T. K.; Fagnou, K. J. Am. Chem. Soc. 2006,
1
28, 8754. (f) Lafrance, M.; Shore, D.; Fagnou, K. Org. Lett. 2006, 8, 5097.
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424 J. Org. Chem. 2008, 73, 7424–7427
10.1021/jo801345b CCC: $40.75 2008 American Chemical Society
Published on Web 08/27/2008