J. Am. Chem. Soc. 2001, 123, 337-338
337
Ru-Catalyzed Oxidative Coupling of Arenes with
Olefins Using O2
Table 1. Oxidative Coupling of Benzene with Acrylate Esters
residual yield yield mass
acrylate propionate cinnamate balance
entry
conditionsa
%
%
% [TON]
%
Haim Weissman, Xiaoping Song, and David Milstein*
b
1
2
3
MA , 2 atm O
2
22
41
38
10
20
23
35 [88]
20 [50]
23 [57]
67
81
84
Department of Organic Chemistry
The Weizmann Institute of Science
MA, no O
MA, no O
no light,
.2 mmol galvinoxyl
MA, 2 atm O
.1 mmol CuO
2
2
,
RehoVot, 76100, Israel
0
ReceiVed September 13, 2000
4
2
,
23
3
35 [88]
63
0
Catalytic carbon-carbon bond formation by C-H activation
is a topic of much current interest. Significant progress has been
made in recent years in the development of synthetically useful
catalytic addition of arenes to alkenes to give the saturated alkyl
arenes.1 Catalytic oxidative coupling of arenes with alkenes to
give aryl alkenes, in which the double bond is preserved, is a
highly desirable goal. Such a reaction, which does not require
the utilization of a reactive substituent and does not produce waste,
may have an advantage over other methods for the preparation
of aromatic alkenes, such as the well-known Heck reaction for
the vinylation of aryl halides. Stoichiometric coupling of olefins
5
6
EA, 2 atm O
EA, 2 atm O
2
26
21
10
19
30 [75]
40 [100]
66
80
2
,
0.2 mmol of HQ
EA, 2 atm O
0.4 mmol of HQ
7
2
,
17
21
42 [105]
80
,2
a
Reaction conditions: a solution containing 8 mL of benzene, 0.02
mmol of 1 and 5 mmol of acrylate esters in a Fischer-Porter glass
reactor is pressurized with 6.1 atm CO and 2 atm O and heated to 180
2
°C with stirring for 48 h. b MA ) methyl acrylate. EA ) ethyl
acrylate. Yields are based on the acrylate ester.
c
3a
4
under the same conditions). Notably, the dehydrogenative coupling
with arenes promoted by Pd(II) is well-known. Tsuji et al., and
5
6
proceeds either under O
In absence of O the olefin itself serves as an oxidant, and a 1:1
ratio of cinnamate:propionate is obtained. In comparison, under
2
(eq 1) or in an inert atmosphere (eq 2).
lately Fujiwara et al. and others, have demonstrated catalysis
by utilizing peroxides as oxidants in their systems. While good
catalytic activity was achieved with some alkenes, acrylates
resulted in low activity (∼10 turnovers). The use of peroxide
oxidants and acetic acid solvent in these systems is problematic
2
2
3
atm of O
2
the cinnamate yield is doubled and a ratio of about
:1 of cinnamate:propionate is obtained (see Table 1). Essentially
no organic carbonylation products are observed. The product
turnover number increases with CO pressure up to 6.1 atm, beyond
which further pressure increase had no beneficial effect. Various
arenes are reactive (see Table 2). Reactants containing acetyl
groups (e.g., vinylmethyl ketone and acetophenone) undergo aldol
condensation and are incompatible with our system. Alkyl acry-
lates are by far the most active of the olefins tested (Table 2).
from the industrial point of view. Attempts to use O
2
or air
7
3b-d,8
resulted in low activity in intra- and intermolecular
coupling,
and alkene oxidation took place in the intermolecular reaction.
Another approach utilizing Rh carbonyl clusters under high (20-
9
3
0 atm) CO pressure resulted in modest catalytic activity with
concomitant hydrocarbonylation of the alkene. Low catalytic
activity was reported for the Rh-catalyzed photochemical coupling
of arenes with alkenes, in which concomitant hydrogenation of
10
the alkene took place and biaryls were formed as byproducts.
A low yield, Rh-catalyzed oxidative phenylation of ethylene was
reported very recently.11
Herein we report on a novel oxidative coupling of arenes with
olefins, in which O can be directly used as the oxidant and good
2
catalytic activity is obtained. The reaction is catalyzed by Ru
complexes and requires a CO atmosphere (eqs 1, 2). Typical
examples are listed in Table 1. The complexes RuCl
3
‚3H
O, and Ru(F
show essentially the same catalytic activity,
(CO)12 is much less active (leading to 15 turnovers
2
O (1),
6
Addition of Cu(II) salts as potential cocatalysts does not have
a beneficial effect on the reaction. In the presence of CuO the
amount of propionate is diminished, but the amount of the
cinnamate does not increase, due to side reactions. Addition of
[
Ru(CO)
CCOCHCOCF
whereas Ru
3
Cl
2
]
2
, [(η -C
6
H
6
)RuCl
2
]
2
, Ru(NO)Cl
3
‚5H
2
3
-
3 3
)
3
(1) Murai, S.; Kakiuchi, F.; Sekine, Tanaka, Y.; Kamatani, A.; Sonoda,
2
CuCl slows down the reaction. This fact and the observed
M.; Chatani, N. Nature 1993, 366, 529. (b) Kakiuchi, F.; Yamakazu, M.;
Chatani, N.; Murai, S. Chem. Lett. 1996, 111.
inhibition of the reaction by CsCl indicate that excess of chloride
anions has a detrimental effect on the catalytic performance.
Addition of a catalytic amount of hydroquinone (HQ) improves
the yield, the turnover number, and the mass balance of the
reaction, perhaps by inhibiting competing radical reactions. Ten
or twenty equiv of HQ (relative to Ru) had a similar effect.
Addition of Galvinoxyl does not retard the reaction, and it
proceeds as well in the dark (entry 3 in Table 1). These
observations tend to exclude a radical chain mechanism for the
reaction. The reaction rate exhibits first-order dependence on the
acrylate concentration under pseudo-first-order conditions, the
derived second-order rate constant being kobs ) 2.328((0.005)
(
2) 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.; Masahiro, I.; Fujiwara, Y. J. Am. Chem. Soc. 2000, 122, 7252.
(
c) Matsumoto, T.; Taube, D. J.; Periana, R. A.; Taube, H.; Yoshida, H. J.
Am. Chem. Soc. 2000, 122, 7414.
3) (a) Moritani, I.; Fujiwara, Y. Tetrahedron Lett. 1967, 1119. (b) Fujiwara,
Y.; Moritani, I.; Danno, S.; Teranishi, S. J. Am. Chem. Soc. 1969, 91, 7166.
(
(
c) Asano, R.; Moritani, I.; Fujiwara, Y.; Teranishi, S. Chem. Commun. 1970,
1
293. (d) Fujiwara, Y.; Asano, R.; Moritani, I.; Teranishi, S. J. J. Org. Chem.
976, 41, 1681.
1
(
4) Tsuji, J.; Nagashima, H. Tetrahedron 1984, 40, 2699.
(
5) . (a) Fujiwara, Y.; Takaki, K.; Taniguchi, Y. Synlett 1996, 591. (b) Jia,
C.; Lu, W.; Kitamura, T.; Fujiwara, Y. Org. Lett. 1999, 1, 2097.
(
6) Mikami, K.; Hatano, M.; Terada, M. Chem. Lett. 1999, 55.
(
7) (a) Miura, M.; Tsuda, T.; Satoh, T.; Nomura, M. Chem. Lett. 1997,
-3
-1 -1
×
10
Using C
/k ) 2 was measured in the reaction with methyl acrylate.
M
h .
1
103. (b) Miura, M.; Tsuda, T.; Satoh, T.; Pivsa-Art, S.; Nomura, M. J. Org.
6
D
6
instead of C
6 6
H , a kinetic isotope effect of
Chem. 1998, 63, 5211.
(
(
(
8) Shue, R. S. J. Catal. 1972, 26, 112.
k
H
D
9) (a) Hong, P.; Yamazaki, H. J. Mol. Catal. 1984, 297.
10) Sasaki, K.; Sakuraka, T.; Tokunaga, Y.; Wada, K.; Tanaka, M. Chem.
12a
12b
Similar kinetic isotope effects of 2.8 and ∼3 were observed
in other systems involving activation of benzene with electrophilic
complexes. Addition of a catalytic amount of the weak non-
Lett. 1988, 685.
11) Matsumoto, T. and Yoshida, H. Chem. Lett. 2000, 1064.
(
1
0.1021/ja003361n CCC: $20.00 © 2001 American Chemical Society
Published on Web 12/21/2000