12686
J. Am. Chem. Soc. 2001, 123, 12686-12687
Although a wide variety of reaction systems were examined
in the hope of achieving the three-component cycloaddition of
benzyne, various alkenes (or alkynes), and CO, we were not able
to achieve the carbonylative cycloaddition reaction. However, it
was found that a few complexes show catalytic activity for
carbonylation reactions of benzyne itself. A cobalt complex was
found to be extremely active for the carbonylation of benzyne.
Thus, the reaction of 1a (0.5 mmol) with CO (5 atm) in CH3CN
(3 mL) in the presence of Co2(CO)8 (0.01 mmol) and CsF (1
mmol) at 60 °C for 12 h gave anthraquinone (2a)11 in 71% isolated
yield, along with a trace amount of triphenylene (eq 1). It was
Catalytic Carbonylation Reactions of Benzyne
Derivatives
Naoto Chatani,* Akihito Kamitani, Masayuki Oshita,
Yoshiya Fukumoto, and Shinji Murai*
Department of Applied Chemistry
Faculty of Engineering, Osaka UniVersity
Suita, Osaka 565-0871, Japan
ReceiVed August 9, 2001
Alkynes can be used as two-carbon assembling units in
cycloaddition reactions, and a variety of transition metal-catalyzed
cycloaddition reactions using alkynes have been reported.1 In
contrast, benzyne derivatives (arynes) have not been used
extensively in the area of transition metal-catalyzed cycloaddition
chemistry despite their ability to undergo cycloaddition reactions.2
The high reactivity and short lifetime of benzyne suggest that its
use as a component of a catalytic reaction might be difficult.
During our ongoing studies of catalytic carbonylative cycload-
dition reactions,3 we have investigated the use of benzyne as a
reactive partner in carbonylative cycloadditions. In 1999, Pe´rez
and Guitia´n reported that the treatment of 2-trimethylsilylphenyl
trifluoromethansulfonate (1a) with CsF and a catalytic amount
of Pd(0) in CH3CN gives triphenylene, possibly via the [2 + 2
+ 2] homo-cyclotrimerization of benzyne.4 They also reported
on the preparation of phenanthrene or naphthalene derivatives
via the Pd-catalyzed [2 + 2 + 2] co-cyclotrimerization of
benzyne-benzyne-alkyne or benzyne-alkyne-alkyne.5,6 Yama-
moto independently reported on a similar co-cyclotrimerization
of benzyne-benzyne-alkyne, catalyzed by a Pd(0) complex.7
Yamamoto later confirmed that these co-cyclotrimerization reac-
tions do not proceed via an all-free benzyne mechanism; rather,
the initial step of the catalytic cycle involves the oxidative addition
of an Ar-OTf bond in benzyne precursor 1a to Pd(0).8 Yamamoto
also reported that the Pd-catalyzed reaction of 1a with allyl
chlorides in the presence of CsF gives phenanthrene derivatives
and that this reaction proceeded via a free benzyne mechanism.8,9
On the other hand, no report on the catalytic carbonylation of
benzyne has appeared in the literature to date. Stoichiometric
reactions of benzyne-transition metal complexes with CO are,
however, known.10 If benzyne could be utilized as a two-carbon
assembly unit in the same manner as alkynes, a new type of
carbonylative cycloaddition reaction is possible. We wish to
report, to the best of our knowledge, the first example of transition
metal-catalyzed carbonylation reactions of benzyne.
found that Co4(CO)12 is more active. The use of Co4(CO)12 as
the catalyst gave 2a in 80% yield. Increasing the CO pressure
(10 and 15 atm) had no significant effect on the product yield
(82 and 80%, respectively); however, the reaction under 1 atm
dramatically decreased the yield. A reaction at 80 °C gave a
slightly lower yield (70%).
While details of the reaction mechanism are not clear at this
time, the formation of these products is consistent with the
intermediacy of 3 and 4, in a manner similar to the transition
metal-mediated synthesis of quinones from alkynes and CO.12
Thus, the incorporation of the second benzyne into 4 followed
by reductive elimination affords 2.
The reaction of a methoxy derivative 1b gave a mixture of
regioisomers 2b and 2b′ in a ratio of 1:1 (eq 2). The reaction of
1c also gave a 1:1 mixture of 2c and 2c′ (eq 3). These results are
(1) Recent reviews on cycloaddition of alkynes, see: Lautens, M.; Klute,
W.; Tam, W. Chem. ReV. 1996, 96, 49. Ojima, I.; Tzamarioudaki, M.; Li, Z.;
Donovan, R. J. Chem. ReV. 1996, 96, 635. Saito, S.; Yamamoto, Y. Chem.
ReV. 2000, 100, 2901.
(2) A recent review on benzyne nickel and platinum complexes, see:
Bennett, M. A.; Wenger, E. Chem. Ber./Rec. 1997, 130, 1029.
(3) For our recent papers on carbonylative cycloaddition, see: Chatani,
N.; Morimoto, T.; Fukumoto, Y.; Murai, S. J. Am. Chem. Soc. 1998, 120,
5335. Morimoto, T.; Chatani, N.; Murai, S. J. Am. Chem. Soc. 1999, 121,
1758. Chatani, N.; Tobisu, M.; Asaumi, T.; Fukumoto, Y.; Murai, S. J. Am.
Chem. Soc. 1999, 121, 7160. Tobisu, M.; Chatani, N.; Asaumi, T.; Amako,
K.; Ie, Y.; Fukumoto, Y.; Murai, S. J. Am. Chem. Soc. 2000, 122, 12663.
Kamitani, A.; Chatani, N.; Morimoto, T.; Murai, S. J. Org. Chem. 2000, 65,
9230.
(4) Pen˜a, D.; Escudero, S.; Pe´rez, D.; Guitia´n, E.; Castedo, L. Angew.
Chem., Int. Ed. 1998, 37, 2659. Pen˜a, D.; Pe´rez, D.; Guitia´n, E.; Castedo, L.
Org. Lett. 1999, 1, 1555.
consistent with benzyne as an intermediate. However, the pos-
sibility that the reaction is initiated by the oxidative addition of
a C-OTf bond to the cobalt complex and subsequent steps, which
involve the insertion of CO, benzyne, and CO, followed by
coupling, cannot be excluded, as Yamamoto has demonstrated.8
(5) Pen˜a, D.; Pe´rez, D.; Guitia´n, E.; Castedo, L. J. Am. Chem. Soc. 1999,
121, 5827.
(6) Pen˜a, D.; Pe´rez, D.; Guitia´n, E.; Castedo, L. Synlett 2000, 1061.
(7) Radhakrishnan, K. V.; Yoshikawa, E.; Yamamoto, Y. Tetrahedron Lett.
1999, 40, 7533.
(8) Yoshikawa, E.; Radhakrishnan, K. V.; Yamamoto, Y. J. Am. Chem.
Soc. 2000, 122, 7280.
(9) Yoshikawa, E.; Yamamoto, Y. Angew. Chem., Int. Ed. 2000, 39, 173.
(10) Bennett, M. A.; Hockless, D. C. R.: Humphrey, M. G.; Schultz, M.;
Wenger, E. Organometallics 1996, 15, 928.
(11) All compounds were characterized by NMR, IR, and mass spectral
data. For new compounds, elemental analyses or high-resolution mass were
also measured. See Supporting Information.
(12) For a review, Liebeskind, L. S.; Baysdon, S.; South, M. S.; Iyer, S.
Tetrahedron 1985, 41, 5839.
10.1021/ja011923c CCC: $20.00 © 2001 American Chemical Society
Published on Web 11/21/2001