alkynes7 and alkylation of aromatic halides with alkyl
halides. For the cases of the arylation of aromatic com-
ever, various phosphine ligands other than PPh
phosphines, phosphites, and bidentate diphosphines, were
3
, such as alkyl
8
6
pounds, we have reported that, in the presence of a catalytic
amount of a rhodium(I)-phosphine complex, pyridylbenzenes
are directly arylated in the ortho position with tetraarylstan-
examined in combination with [RuCl
not exhibit comparably favorable results. Wilkinson complex
(RhCl(PPh ), which was most effective in arylation reaction
2
(η -C
6 6 2
H )] , and did
3 3
)
9
9
nanes. Coordination by the pyridyl group is presumed to
with tetraarylstannanes, showed a lower catalytic activity
direct the rhodium complex during the cleavage of the ortho
C-H bond. Arylations with aryl halides were also reported;
for example, phenolic compounds such as 1-naphthols and
in the present reaction system, affording product 6aa in
merely 22% yield. Other PPh - and chlorine-coordinated
3
complexes of Fe, Co, Pd, and Pt did not demonstrate any
catalytic activities. Aprotic polar solvents were suitable for
the reaction, of which NMP exhibited the best results.
Iodobenzene (3a) and phenyltriflate (4a) were also used as
phenylating reagents; reaction of the former gave 65% yield
of product 6aa and 14% yield of product 7aa, while the latter
gave 61% yield of product 6aa and 7% yield of product 7aa.
The reaction of chlorobenzene (5a) was slower; 32% yield
of product 6aa was obtained from the reaction after 20 h.
When reactant 1a (0.5 mmol) was treated with an excess
amount of bromobenzene (2a, 1.5 mmol) under similar
1
0
11
2
-phenylphenols, benzyl phenyl ketones, and benz-
12
anilides were arylated with aryl halides in the presence of
palladium catalyst. It is considered that the coordination
between the phenolate or enolate oxygen of the substrates
and the arylpalladium intermediate plays a key role in these
reactions. In our previous report, the arylrhodium species
generated by the transmetalation with tetraarylstannane is
assumed to be a key intermediate. The oxidative addition of
aryl halides to transition metal complexes would also yield
the arylated transition metal species, which was thus expected
to act similarly as an intermediate for the arylation of
pyridylbenzenes. Herein we report that, in the presence of a
catalytic amount of a ruthenium(II)-phosphine complex, the
aromatic rings of pyridyl group-substituted aromatic com-
pounds were directly arylated or alkenylated, in the ortho
position, with the corresponding organic halides.
2 3
reaction conditions, except the increased amount of K CO
(3.0 mmol), the diphenylated product 7aa was obtained
exclusively in 77% yield.
Table 1 summarizes the representative results for the
reactions of arylpyridines 1 with equimolar amounts of
1
3
bromides 2. The arylation of 2-phenylpyridine (1a) with
substituted bromobenzenes 2b, 2c, or 1-bromonaphthalene
(2d) proceeded comparably as in the case of bromobenzene
(2a), affording the monoarylated products 6ab-ad in 60-
64% yields and the diarylated products 7ab-ad in 16-18%
yields (entries 1-3). The reaction of 1a with a hetero-aryl
bromide, bromopyridine (2e), yielded products 6ae and 7ae
in 40% and 14% yields, respectively (entry 4). Alkenylation
was also observed when 1a was treated with â-bromostyrene
2-Phenylpyridine (1a, 0.5 mmol) was treated with an
equimolar amount of bromobenzene (2a, 0.5 mmol) in the
6
presence of [RuCl
2
(η -C
6
H
6
)]
2
(0.0125 mmol), PPh
3
(0.05
mmol, P/Ru ratio ) 2), and K
2
CO (1.0 mmol) in N-
3
methylpyrrolidinone (NMP) at 120 °C for 20 h to yield the
monophenylated product 6aa (71% yield) and a small amount
of the diphenylated product 7aa (11% yield, Scheme 1).
(
2f) to afford the monoalkenylated product 6af in 62% yield
and the dialkenylated product 7af in 17% yield (entry 5).
-Methyl-2-phenylpyridine (1b) selectively gave the mono-
3
phenylated product (6ba) in 90% yield in the reaction with
bromobenzene (2a, entry 6). As was described in the
4,5
literatures, the steric interaction between the phenyl group
and the methyl group in 6ba would prevent the second
phenylation. Meta substituted phenylpyridines underwent the
arylation only at the less hindered ortho position. Thus, the
(
8) (a) Catellani, M.; Frignani, F.; Rangoni, A. Angew. Chem., Int. Ed.
Engl. 1997, 36, 119. (b) Catellani, M.; Cugini, F. Tetrahedron 1999, 55,
595.
6
(
(
9) Oi, S.; Fukita, S.; Inoue, Y. Chem. Commun. 1998, 2439.
10) (a) Satoh, T.; Kawamura, Y.; Miura, M.; Nomura, M. Angew. Chem.,
Int. Ed. Engl. 1997, 36, 1740. (b) Satoh, T.; Inoh, J.-I.; Kawamura, Y.;
Kawamura, Y.; Miura, M.; Nomura, M. Bull. Chem. Soc. Jpn. 1998, 71,
2
239. (c) Kawamura, Y.; Satoh, T.; Miura, M.; Nomura, M. Chem. Lett.
1999, 961.
(
11) Satoh, T.; Kametani, Y.; Terao, Y.; Miura, M.; Nomura, M.
Tetrahedron Lett. 1999, 40, 5345.
12) Kametani, Y.; Satoh, T.; Miura, M.; Nomura, M. Tetrahedron Lett.
000, 41, 2655.
13) A following procedure is representative. A mixture of 1a (77.6 mg,
.5 mmol), 2a (78.6 mg, 0.5 mmol), K2CO3 (138 mg, 1.0 mmol), PPh3
(13.1 mg, 0.05 mmol), and [RuCl2(η -C6H6)]2 (6.3 mg, 0.0125 mmol,
available from Aldrich) in 1 mL of dried NMP was stirred at 120 °C for 20
h under a N2 atmosphere in a Schlenk tube. The reaction mixture was diluted
with 50 mL of EtOAc, washed with water (20 mL × 3), and dried over
MgSO4. After the solvent was evaporated in vacuo, the residue was purified
by flash chromatography (hexanes-EtOAc, 5: 1) to give the phenylated
products 6aa (82.1 mg, 71%) and 7aa (16.9 mg, 11%).
(
2
2 3 3 2 2 3
RuCl (PPh ) or [RuCl (cod)] -4PPh catalytic systems also
(
showed good activities in affording the products in similar
yields, which indicate that the preceding three catalytic
systems generate analogous active catalytic species. How-
0
6
(7) (a) Jia, C.; Piao, D.; Oyamada, J.; Lu, W.; Kitamura, T.; Fujiwara,
Y. Science 2000, 287, 1992. (b) Jia, C.; Lu, W.; Oyamada, J.; Kitamura,
T.; Matsuda, K.; Irie, M.; Fujiwara, Y. J. Am. Chem. Soc. 2000, 122, 7252.
2580
Org. Lett., Vol. 3, No. 16, 2001
Oi, Shuichi
