Rhodium-catalyzed silylation and intramolecular arylation of nitriles via the silicon-assisted cleavage of carbon-cyano bonds

Article abstract of DOI:10.1021/ja804992n

A rhodium-catalyzed silylation reaction of carbon - cyano bonds using disilane has been developed. Under these catalytic conditions, carbon-cyano bonds in aryl, alkenyl, allyl, and benzyl cyanides bearing a variety of functional groups can be silylated. The observation of an enamine side product in the silylation of benzyl cyanides and related stoichiometric studies indicate that the carbon-cyano bond cleavage proceeds through the deinsertion of silyl isocyanide from η²-iminoacyl complex B. Knowledge gained from these studies has led to the development of a new intramolecular biaryl coupling reaction in which aryl cyanides and aryl chlorides are cross-coupled.

Full text of DOI:10.1021/ja804992n

Published on Web 11/01/2008
Rhodium-Catalyzed Silylation and Intramolecular Arylation of
Nitriles via the Silicon-Assisted Cleavage of Carbon-Cyano
Bonds
Mamoru Tobisu,*,† Yusuke Kita, Yusuke Ano, and Naoto Chatani*
Department of Applied Chemistry, Faculty of Engineering, Osaka UniVersity, Suita,
Osaka 565-0871, Japan
Received June 30, 2008; E-mail: tobisu@chem.eng.osaka-u.ac.jp; chatani@chem.eng.osaka-u.ac.jp
Abstract: A rhodium-catalyzed silylation reaction of carbon-cyano bonds using disilane has been
developed. Under these catalytic conditions, carbon-cyano bonds in aryl, alkenyl, allyl, and benzyl cyanides
bearing a variety of functional groups can be silylated. The observation of an enamine side product in the
silylation of benzyl cyanides and related stoichiometric studies indicate that the carbon-cyano bond cleavage
proceeds through the deinsertion of silyl isocyanide from η2-iminoacyl complex B. Knowledge gained from
these studies has led to the development of a new intramolecular biaryl coupling reaction in which aryl
cyanides and aryl chlorides are cross-coupled.
Introduction
(ca. 130 kcal/mol for Ar-CN) can be cleaved without the aid
of ring strain or extra coordinating groups.3 Fundamental interest
The cleavage of carbon-carbon σ-bonds by transition-metal
complexes and their use for chemical transformation would
provide a conceptually new strategy in organic synthesis.
However, the inherent stability of carbon-carbon σ-bonds
makes the development of such a process a daunting challenge.
Although some success has been attained to this end, it has
usually required the utilization of strained carbon-carbon bonds
or chelation-assisted systems.1,2 This limitation is absent in the
transition-metal-mediated cleavage of carbon-carbon σ-bonds
in nitriles, in which the strong carbon-cyano (C-CN) bond
in this unique process has prompted organometallic chemists
to identify two discrete mechanisms for the activation of C-CN
bonds. One process involves the oxidative addition to a low-
valent metal center, such as Pt,4 Pd,5 Ni,6 and others7 (Scheme
1). The vast majority of reported C-CN bond cleavage reactions
have occurred through this oxidative addition mechanism, and
its application to catalytic processes, including isomerization,8
cross-coupling,9 and carbocyanation,10 has also been discussed.11
In 2003, Bergman and Brookhart reported an alternative
mechanism in which a silyl ligand on the metal complex plays
a critical role (Scheme 2, M ) Rh).12-14 The insertion of a
cyano group into a metal-silyl bond in A forms the η2-
iminoacyl complex B, which undergoes the deinsertion of silyl
isocyanide to afford the carbon-carbon bond cleaved complex
† Frontier Research Base for Global Young Researchers, Graduate School
of Engineering, Osaka University, Suita, Osaka 565-0871, Japan.
(1) (a) Murakami, M.; Ito, Y. In ActiVation of UnreactiVe Bonds and
Organic Synthesis; Murai, S., Ed.; Springer: Berlin, 1999; p 99. (b)
van der Boom, M. E.; Milstein, D. Chem. ReV. 2003, 103, 1759. (c)
Jun, C.-H. Chem. Soc. ReV. 2004, 33, 610. (d) Kondo, T.; Mitsudo,
T. Chem. Lett. 2005, 34, 1462. (e) Park, Y. J.; Park, J.-W.; Jun, C.-H.
Acc. Chem. Res. 2008, 41, 222.
(7) Mo: (a) Churchill, D.; Shin, J. H.; Hascall, T.; Hahn, J. M.;
Bridgewater, B. M.; Parkin, G. Organometallics 1999, 18, 2403. Co:
(b) Ozawa, F.; Iri, K.; Yamamoto, A. Chem. Lett. 1982, 1707. (c) Li,
X.; Sun, H.; Yu, F.; Florke, U.; Klein, H.-F. Organometallics 2006,
25, 4695. U: (d) Adam, R.; Villiers, C.; Ephritikhine, M.; Lance, M.;
Nierlich, M.; Vigner, J. J. Organomet. Chem. 1993, 445, 99. Cu: (e)
Marlin, D. S.; Olmstead, M. M.; Mascharak, P. K. Angew. Chem.,
Int. Ed. 2001, 40, 4752. (f) Lu, T.; Zhuang, X.; Li, Y.; Chen, S. J. Am.
Chem. Soc. 2004, 126, 4760.
(2) For a notable exception, see:(a) Muller, C.; Iverson, C. N.; Lachicotte,
R. J.; Jones, W. D. J. Am. Chem. Soc. 2001, 123, 9718. (b) Gunay,
A.; Jones, W. D. J. Am. Chem. Soc. 2007, 129, 8729.
(3) (a) Tobisu, M.; Chatani, N. Chem. Soc. ReV. 2008, 37, 300. (b) Nakao,
Y.; Hiyama, T. Pure Appl. Chem. 2008, 80, 1097.
(4) Pt: Burmeister, J. L.; Edwards, L. M. J. Chem. Soc. A 1971, 1663.
See also ref 5.
(5) Pd: (a) Parshall, G. W. J. Am. Chem. Soc. 1974, 96, 2360. (b) Liu,
Q.-X.; Xu, F.-B.; Li, Q.-S.; Song, H.-B.; Zhang, Z.-Z. Organometallics
2004, 23, 610.
(8) (a) Chaumonnot, A.; Lamy, F.; Sabo-Etienne, S.; Donnadieu, B.;
Chaudret, B.; Barthelat, J.-C.; Galland, J.-C. Organometallics 2004,
23, 3363. (b) Wilting, J.; Mu¨ller, C.; Hewat, A. C.; Ellis, D. D.; Tooke,
D. M.; Spek, A. L.; Vogt, D. Organometallics 2005, 24, 13. (c) van
der Vlugt, J. I.; Hewat, A. C.; Neto, S.; Sablong, R.; Mills, A. M.;
Lutz, M.; Spek, A. L.; Mu¨ller, C.; Vogt, D. AdV. Synth. Catal. 2004,
346, 993. (d) Acosta-Ram´ırez, A.; Flores-Gaspar, A.; Mun˜oz-Her-
na´ndez, M.; Are´valo, A.; Jones, W. D.; Garc´ıa, J. J. Organometallics
2007, 26, 1712. (e) Acosta-Ram´ırez, A.; Mun˜oz-Herna´ndez, M.; Jones,
W. D.; Garc´ıa, J. J. Organometallics 2007, 26, 5766. (f) Acosta-
(6) Ni: (a) Gerlach, D. H.; Kane, A. R.; Parshall, G. W.; Jesson, J. P.;
Muetterties, E. L. J. Am. Chem. Soc. 1971, 93, 3543. (b) Morvillo,
A.; Turco, A. J. Organomet. Chem. 1981, 208, 103. (c) Favero, G.;
Morvillo, A.; Turco, A. J. Organomet. Chem. 1983, 241, 251. (d) Abla,
M.; Yamamoto, T. J. Organomet. Chem. 1997, 532, 267. (e) Luo,
F.-H.; Chu, C.-I.; Cheng, C.-H. Organometallics 1998, 17, 1025. (f)
Garcia, J. J.; Jones, W. D. Organometallics 2000, 19, 5544. (g) Garcia,
J. J.; Brunkan, N. M.; Jones, W. D. J. Am. Chem. Soc. 2002, 124,
9547. (h) Brunkan, N. M.; Brestensky, D. M.; Jones, W. D. J. Am.
Chem. Soc. 2004, 126, 3627. (i) Garcia, J. J.; Arevalo, A.; Brunkan,
N. M.; Jones, W. D. Organometallics 2004, 23, 3997. (j) Ates¸in, T. A.;
Li, T.; Lachaize, S.; Brennessel, W. W.; Garc´ıa, J. J.; Jones, W. D.
J. Am. Chem. Soc. 2007, 129, 7562. (k) Schaub, T.; Do¨ring, C.; Radius,
U. Dalton Trans. 2007, 1993. See also refs 4 and 5.
´
Ram´ırez, A.; Flores-Alamo, M.; Jones, W. D.; Garc´ıa, J. J. Organo-
metallics 2008, 27, 1834. (g) Swartz, B. D.; Reinartz, N. M.;
Brennessel, W. W.; Garc´ıa, J. J.; Jones, W. D. J. Am. Chem. Soc.
2008, 130, 8548.
(9) (a) Miller, J. A. Tetrahedron Lett. 2001, 42, 6991. (b) Miller, J. A.;
Dankwardt, J. W. Tetrahedron Lett. 2003, 44, 1907. (c) Miller, J. A.;
Dankwardt, J. W.; Penney, J. M. Synthesis 2003, 1643.
9
15982 J. AM. CHEM. SOC. 2008, 130, 15982–15989
10.1021/ja804992n CCC: $40.75
2008 American Chemical Society

Rh-Catalyzed Silylation and Arylation of Nitriles
A R T I C L E S
Scheme 1. C-CN Bond Cleavage via Oxidative Addition
Scheme 3. Rhodium-Catalyzed Silylation of Nitriles via C-CN
Bond Cleavage
Scheme 2. C-CN Bond Cleavage via Deinsertion of Silyl
Isocyanide
Scheme 4. Mechanistic Hypothesis for the Catalytic Silylation of
Nitriles
C. Nakazawa subsequently reported that a silyliron complex
can mediate the C-CN bond cleavage under photochemical
conditions via the same mechanism (Scheme 2, M ) Fe).15 This
iron-mediated photochemical process was further applied to the
catalytic conversion of a C-CN bond into a C-H bond using
hydrosilane as a reducing agent.15b,c,e Recently, Hashimoto and
Tobita reported that the reaction of a ruthenium silylene complex
with nitriles resulted in the formation of a ruthenium silyl
isocyanide complex, as in C (M ) Ru).16 A silicon-assisted
mechanism, similar to that shown in Scheme 2, has been
proposed as one of the two possibilities for this ruthenium-
mediated C-CN bond cleavage process. On the other hand,
we recently reported that a C-CN bond can be cleaved
catalytically in the presence of a rhodium complex and disilanes
to form a C-Si bond (Scheme 3).17 This reaction represents
the first illustration that the silicon-assisted catalytic cleavage
of C-CN bonds proceeds thermally. The full details of this
catalysis are described herein, including reaction condition
optimization, substrate scope, mechanistic aspects, and applica-
tion to intramolecular arylation.
Results and Discussion
Silylation of Aryl, Alkenyl, and Alkyl Cyanides. To construct
a catalytic cycle that contains a silicon-assisted C-CN bond
cleavage process (Scheme 2), it was necessary to define the
pathway for regenerating the silylmetal species from the C-CN
cleaved complex C (Scheme 4). The approach used to address
this issue was the utilization of disilanes, which would react
with the complex C to form carbon-silicon and metal-silicon
bonds via σ-bond metathesis or an oxidative addition/reductive
elimination sequence.18 Overall, it was expected that the reaction
of nitriles with disilanes would result in the formation of
organosilanes and silyl isocyanides. It was also expected that
the use of disilanes might allow the in situ generation of the
metal silyl species A from the readily available metal halides
or their derivatives.
The studies began with an investigation of the reaction of
2-cyanonaphthalene (1) and hexamethyldisilane (2a) as a
prototype for the catalysis shown in Scheme 4. A pioneering
work by Bergman and Brookhart led to the initial examination
of [Cp*RhCl2]2/PPh3 as a catalyst precursor, and it was found
that the expected 2-(trimethylsilyl)naphthalene (3a) was obtained
in 12% yield (entry 1 in Table 1). Stimulated by this promising
result, a variety of rhodium complexes were then examined.
Several Rh(I) complexes, such as [RhCl(cod)]2, [RhCl(coe)2]2,
[RhOMe(cod)]2, and [Rh(cod)2]BF4, exhibited much-improved
catalytic activity (entries 2-5), while [RhCl(CO)2]2, [IrCl(cod)]2,
and [Cp*RuCl]n were inactive under these conditions. Interest-
ingly, the Ni(cod)2/PBu3 system, which is competent for the
oxidative addition of C-CN bonds,8-10 did not give any
silylated products. The solvent employed also proved to be an
important factor in the efficiency of the reaction. Among the
solvents examined, ethylcylohexane gave the highest yield (entry
8). Although the reaction was routinely conducted at 130 °C, it
(10) (a) Nakao, Y.; Oda, S.; Hiyama, T. J. Am. Chem. Soc. 2004, 126,
13904. (b) Nakao, Y.; Oda, S.; Yada, A.; Hiyama, T. Tetrahedron
2006, 62, 7567. (c) Nakao, Y.; Yukawa, T.; Hirata, Y.; Oda, S.; Satoh,
J.; Hiyama, T. J. Am. Chem. Soc. 2006, 128, 7116. (d) Nakao, Y.;
Yada, A.; Satoh, J.; Ebata, S.; Oda, S.; Hiyama, T. Chem. Lett. 2006,
35, 790. (e) Nakao, Y.; Yada, A.; Ebata, S.; Hiyama, T. J. Am. Chem.
Soc. 2007, 129, 2428. (f) Nakao, Y.; Hirata, Y.; Tanaka, M.; Hiyama,
T. Angew. Chem., Int. Ed. 2008, 47, 385. (g) Nakao, Y.; Ebata, S.;
Yada, A.; Hiyama, T.; Ikawa, M.; Ogoshi, S. J. Am. Chem. Soc. 2008,
130, 12874. (h) Watson, M. P.; Jacobsen, E. N. J. Am. Chem. Soc.
2008, 130, 12594.
(11) Catalytic reactions involving the cleavage of C(dO)sCN bonds, a
special class of CsCN bonds, have also been reported:(a) Blum, J.;
Oppenheimer, E.; Bergmann, E. D. J. Am. Chem. Soc. 1967, 89, 2338.
(b) Murahashi, S.; Naota, T.; Nakajima, N. J. Org. Chem. 1986, 51,
898. (c) Nozaki, K.; Sato, N.; Takaya, H. J. Org. Chem. 1994, 59,
2679. (d) Nozaki, K.; Sato, N.; Takaya, H. Bull. Chem. Soc. Jpn. 1996,
69, 1629. (e) Nishihara, Y.; Inoue, Y.; Itazaki, M.; Takagi, K. Org.
Lett. 2005, 7, 2639. (f) Nishihara, Y.; Inoue, Y.; Izawa, S.; Miyasaka,
M.; Tanemura, K.; Nakajima, K.; Takagi, K. Tetrahedron 2006, 62,
9872. (g) Nakao, Y.; Hirata, Y.; Hiyama, T. J. Am. Chem. Soc. 2006,
128, 7420. (h) Kobayashi, Y.; Kamisaki, H.; Yanada, R.; Takemoto,
Y. Org. Lett. 2006, 8, 2711. (i) Kobayashi, Y.; Kamisaki, H.; Takeda,
H.; Yasui, Y.; Yanada, R.; Takemoto, Y. Tetrahedron 2007, 63, 2978.
(j) Nishihara, Y.; Miyasaka, M.; Inoue, Y.; Yamaguchi, T.; Kojima,
M.; Takagi, K. Organometallics 2007, 26, 4054. (k) Yasui, Y.;
Kamisaki, H.; Takemoto, Y. Org. Lett. 2008, 10, 3303.
(12) (a) Taw, F. L.; White, P. S.; Bergman, R. G.; Brookhart, M. J. Am.
Chem. Soc. 2002, 124, 4192. (b) Taw, F. L.; Mueller, A. H.; Bergman,
R. G.; Brookhart, M. J. Am. Chem. Soc. 2003, 125, 9808.
(13) A similar stoichiometric reaction has been reported, although the
mechanism is proposed to be oxidative addition: Klei, S. R.; Tilley,
T. D.; Bergman, R. G. Organometallics 2002, 21, 4648.
(14) One catalytic C-CN bond cleavage reaction that proceeds through
neither of the processes shown in Schemes 1 and 2 has also been
reported: Luo, F.-H.; Chu, C.-I.; Cheng, C.-H. Organometallics 1998,
17, 1025.
(15) (a) Nakazawa, H.; Kawasaki, T.; Miyoshi, K.; Suresh, C. H.; Koga,
N. Organometallics 2004, 23, 117. (b) Nakazawa, H.; Kamata, K.;
Itazaki, M. Chem. Commun. 2005, 4004. (c) Itazaki, M.; Nakazawa,
H. Chem. Lett. 2005, 34, 1054. (d) Hashimoto, H.; Matsuda, A.; Tobita,
H. Organometallics 2006, 25, 472. (e) Nakazawa, H.; Itazaki, M.;
Kamata, K.; Ueda, K. Chem.sAsian J. 2007, 2, 882.
(18) Reviews on the Si-Si bond activation:(a) Sharma, H. K.; Pannell,
K. H. Chem. ReV. 1995, 95, 1351. (b) Suginome, M.; Ito, Y. Chem.
ReV. 2000, 100, 3221. (c) Beletskaya, I.; Moberg, C. Chem. ReV. 2006,
106, 2320.
(16) Ochiai, M.; Hashimoto, H.; Tobita, H. Angew. Chem., Int. Ed. 2007,
46, 8192.
(17) Tobisu, M.; Kita, Y.; Chatani, N. J. Am. Chem. Soc. 2006, 128, 8152.
9
J. AM. CHEM. SOC. VOL. 130, NO. 47, 2008 15983

A R T I C L E S
Tobisu et al.
Table 1. Rh(I)-Catalyzed Silylation Reaction of Nitriles: Catalyst
Table 2. Rh(I)-Catalyzed Silylation Reaction of Nitriles: Disilane
and Solvent Optimizationa
Variationa
entry
catalyst
solvent
yieldb (%)
entry
disilane
yieldb (%)
1
2
3
[Cp*RhCl2]2/2PPh3
[RhCl(cod)]2
[RhCl(coe)2]2
[Rh(OMe)(cod)]2
[Rh(cod)2]BF4
[RhCl(cod)]2
[RhCl(cod)]2
[RhCl(cod)]2
[RhCl(cod)]2
mesitylene
mesitylene
mesitylene
mesitylene
mesitylene
dioxane
DMA
ethylcyclohexane
ethylcyclohexane
12
53
62
80
65
71
36
87
49
1
2
3
4
5
6
7
8
Me3Si-SiMe3 (2a)
87
46
41
0
0
0
PhMe2Si-SiMe2Ph (2b)
BnMe2Si-SiMe2Bn (2c)
t-BuMe2Si-SiMe2t-Bu (2d)
Ph2MeSi-SiMePh2 (2e)
Et3Si-SiEt3 (2f)
4
5c
6
7
FMe2Si-SiMe2F (2g)
(EtO)3Si-Si(OEt)3 (2h)
0
0
8
9d
a Reaction conditions: 1 (2.0 mmol), 2 (4.0 mmol), catalyst (0.10
mmol) in solvent (1.0 mL) at 130 °C, 15 h. b Isolated yields.
a Reaction conditions: 1 (2.0 mmol), 2a (4.0 mmol), catalyst (0.10
mmol) in solvent (1.0 mL) at 130 °C, 15 h. b Isolated yields. c A 10 mol
% concentration of [Rh(cod)2]BF4 was used. d Run at 100 °C.
process was further demonstrated by the successful use of
benzonitriles containing boronic esters (entry 14), indicating that
the transfer of the aryl group on the boron to a rhodium center
did not occur under these conditions.19 In addition to benzonitrile
derivatives, nitriles containing heteroaromatics, such as pyrroles
(entry 17), indoles (entry 18), and quinolines (entry 19), and a
Cp ring of ferrocene (entry 20) were all good substrates for the
Rh-catalyzed reaction. On the other hand, the reaction of
benzonitriles bearing nitro, acetyl, and acetamide groups did
not give any silylated products. In the course of the examination
of the reaction scope, a significant impact of the electronic nature
of nitriles on the reaction rate was observed. In general, electron-
deficient substrates were silylated faster than electron-rich
nitriles. For example, 4-methoxybenzonitrile required more than
40 h for the full conversion, while the reaction of a 4-(trifluo-
romethyl)benzonitrile was completed within 15 h (entry 1 vs
entry 8). The reaction was also sensitive to the steric environ-
ment of the nitrile moiety. Thus, the use of sterically congested
substrates retarded the reaction (entries 12 and 16). Rate
acceleration resulting from the introduction of an electron-
withdrawing group could compensate for this unfavorable steric
effect (entry 13).
The compatibility of the aryl halide moiety was investigated
next. Although aryl fluorides remained intact under the Rh-
catalyzed reaction (entry 2), chlorides and bromides proved to
be susceptible to silylation. For example, the reaction of
4-bromobenzonitrile (4) with 1.1 equiv of disilane 2a resulted
in the selective formation of compound 6, in which the silylation
took place at the bromide site (eq 4). By increasing the amount
of 2a, both functionalities were silylated, furnishing a 1,4-
bis(trimethylsilyl)benzene, 7. It has been reported that rhodium
complexes can catalyze the silylation of aryl halides using
hydrosilanes,20a-c but the rhodium catalysis with disilanes is
unprecedented, to the best of our knowledge.21
could proceed at a lower temperature (100 °C), albeit at a slower
rate (entry 9). Addition of ligands, such as PPh3, PBu3, P(OPh)3,
and pyridine, led to a decrease in the yield, probably due to
their competitive coordination with a cyano group.
The effect of the substituents on the silicon atom of disilanes
was examined next (Table 2). When one of the methyl groups
on each silicon atom in 2a was replaced with a phenyl (2b) or
benzyl (2c) group, the corresponding silylated products were
obtained in modest yields (entries 2 and 3). However, the use
of the much bulkier tert-butyldimethylsilyl (2d), methyldiphe-
nylsilyl (2e), and triethylsilyl (2f) groups led to no conversion
at all (entries 4-6). The activation of silicon-silicon bonds is
often accelerated by the introduction of electron-withdrawing
groups on the silicon moiety.18 However, in the present catalytic
system, no desired products were formed with disilanes 2g and
2h, due in part to the instability of these disilanes under the
reaction conditions (entries 7 and 8).
Unsymmetrically substituted disilanes were also examined.
The reaction of 1 with 1,1,1,2,2-pentamethyl-2-phenyldisilane
(2i) under standard conditions resulted in the formation of
equimolar amounts of 3a and 3b, indicating that trimethylsilyl
and dimethylphenylsilyl groups are not differentiated signifi-
cantly in any of the steps involved in the present catalysis (eq
1).
The scope of the Rh-catalyzed silylation of nitriles with 2a
was then examined (Table 3). A number of functional groups,
such as fluorines (entries 1, 2, and 13), esters (entries 3, 4, 7,
and 11), ethers (entries 8 and 10), and amines (entry 9) proved
to be compatible with this catalytic system. The presence of an
acidic NH group lowered the yield of the silylated product, due
to the accompanied formation of the product in which a cyano
group is substituted by a hydrogen atom (entry 5). In contrast,
N,N-disubstituted amides were well suited for this catalytic
silylation (entry 6). The high functional group tolerance of the
Although the present catalysis promotes the silylation of both
aryl halides and cyanides, it is known that the former function-
9
15984 J. AM. CHEM. SOC. VOL. 130, NO. 47, 2008

Rh-Catalyzed Silylation and Arylation of Nitriles
A R T I C L E S
Table 3. Rh(I)-Catalyzed Silylation Reaction of Aryl Cyanidesa
ality can also be silylated by other catalytic methods.20,21 We
envisioned that, by combining such a method with our catalytic
silylation, halides and nitriles could be silylated orthogonally.
As expected, the Pt-catalyzed reaction20f of 4-iodobenzonitrile
(8) allowed the selective introduction of a triethylsilyl group at
the iodide site without affecting the nitrile functionality (eq 4).
The subsequent silylation of a cyano group in 9 by rhodium
catalysis afforded a benzene derivative containing two different
silyl groups, as in 10.
To further extend the scope of the reaction, we examined
the silylation of alkenyl cyanides (Table 4). At the time that
we initiated this study, there had been no reports on catalytic
reactions involving the cleavage of alkenyl C-CN bonds,
irrespective of the mechanism involved. Nakao and Hiyama
recently reported that a Ni(0)/Lewis acid dual catalyst system
can promote the addition of alkenyl C-CN bonds to alkynes.10e
We were pleased to find that the C-CN bond of trans-
cinnamonitrile could be silylated with disilanes under these Rh-
catalyzed conditions (entry 1). The silylation of the cis-isomer
exclusively afforded the corresponding alkenylsilane with trans
geometry (entry 2). A silylated product was not obtained with
alkenyl cyanide bearing an alkyl group, presumably because
the starting cyanide was prone to decompose under the reaction
conditions (entry 3). On the other hand, more stable cyclohex-
enyl cyanide could be silylated in moderate yield (entry 4).
Notably, sterically congested 2,2-disubstituted alkenyl cyanide
proved to be a good substrate for this reaction (entry 5).
Although alkenyl cyanide containing three phenyl groups at each
vinylic position was inert (entry 6), replacing one phenyl with
an ester group remarkably enhanced the reactivity of the C-CN
bond to furnish the corresponding silylated product (entry 7).
This indicates that an electron-deficient C-CN bond exhibits
superior reactivity, as was observed in the silylation of aryl
cyanides (Table 3).
Allyl cyanides are also possible substrates for this catalytic
reaction, in view of some successful examples of the catalytic
cleavage of their C-CN bonds via oxidative addition.8,10c As
expected, the silylation of allyl cyanide 11 furnished allylsilane
12 in 59% yield (eq 5). Complete conversion was reached at a
lower temperature (100 °C), although the reactions of aryl and
alkenyl cyanides generally required heating at 130 °C. The
a Reaction conditions: nitrile (2.0 mmol), 2a (4.0 mmol), [RhCl-
(cod)]2 (0.10 mmol) in ethylcyclohexane (1.0 mL) at 130 °C, 15 h.
b Isolated yields. c GC yield. d [Rh(OMe)(cod)]2 was used as a catalyst.
e N-tert-Butylbenzamide was also isolated in 20% yield. f Run for 40 h.
g [Rh(cod)2]BF4 was used as a catalyst. h Run for 96 h. i Run for 60 h.
j A 10 mol % concentration of the catalyst was used.
(19) (a) Fagnou, K.; Lautens, M. Chem. ReV. 2003, 103, 169. (b) Hayashi,
T.; Yamasaki, K. Chem. ReV. 2003, 103, 2829.
relatively facile cleavage of C-CN bonds in the allyl cyanides
might be attributed to the intermediacy of a stable π-allyl-
rhodium complex.
(20) For selected examples of the catalytic silylation of aryl halides using
hydrosilanes, see the following references. Rh: (a) Murata, M.;
Ishikura, M.; Nagata, M.; Watanabe, S.; Masuda, Y. Org. Lett. 2002,
4, 1843. (b) Murata, M.; Yamasaki, H.; Ueta, T.; Nagata, M.; Ishikura,
M.; Watanabe, S.; Masuda, Y. Tetrahedron 2007, 63, 4087. (c)
Yamanoi, Y.; Nishihara, H. Tetrahedron Lett. 2006, 47, 7157. Pd: (d)
Seganish, W. M.; Handy, C. J.; DeShong, P. J. Org. Chem. 2005, 70,
8948. (e) Denmark, S. E.; Kallemeyn, J. M. Org. Lett. 2003, 5, 3483.
Pt: (f) Hamze, A.; Provot, O.; Alami, M.; Brion, J.-D. Org. Lett. 2006,
8, 931.
(21) Pd-catalyzed silylation of aryl halides using disilanes has been reported:
(a) Shirakawa, E.; Kurahashi, T.; Yoshida, H.; Hiyama, T. Chem.
Commun. 2000, 1895. (b) Gooaˆen, L. J.; Ferwanah, A.-R. S. Synlett
2000, 1801. (c) Iwasawa, T.; Komano, T.; Tajima, A.; Tokunaga, M.;
Obora, Y.; Fujihara, T.; Tsuji, Y. Organometallics 2006, 25, 4665.
The silylation reaction of benzyl cyanides was examined next
(Table 5). At 100 °C, the expected benzylsilanes 14 were
obtained in low to moderate yields with an array of benzyl
cyanides (entries 1-5). Since significant amounts of the starting
9
J. AM. CHEM. SOC. VOL. 130, NO. 47, 2008 15985

A R T I C L E S
Tobisu et al.
Table 4. Rh(I)-Catalyzed Silylation Reaction of Alkeneyl Cyanidesa
The product distribution (i.e., 14/15) was not significantly
affected by the electronic and steric nature of the aryl group of
the benzyl cyanides. However, the predominant formation of
the enamine product was observed in the silylation of diphe-
nylacetonitrile 13f at 160 °C (eq 5). The formation of unexpected
side product 15 provided some insight into the reaction
mechanism (vide infra).
Next, we turned our attention to the use of unactivated alkyl
cyanides in this silylation reaction. Regardless of the mechanism
involved, utilization of unactivated C(sp3)-CN bonds containing
ꢀ-hydrogen atoms for the catalytic transformation represents a
challenge, due to the difficulty in suppressing a facile ꢀ-hydro-
gen elimination process of the intermediate metal alkyl
species.10e The ability of our catalytic system to silylate
unactivated C(sp3)-CN bonds was investigated using nitrile 16
as a test substrate (eq 5). After a variety of optimization studies,
the silylated product 17 was obtained in 48% yield by adding
P(O-i-Pr)3 as an additive. Although the efficiency of the reaction
was unsatisfactory, it is noteworthy that byproducts arising from
the ꢀ-hydrogen elimination process of the possible metal alkyl
intermediate (i.e., allylbenzene or ꢀ-methylstyrene) were not
observed.
a Reaction conditions: nitrile (2.0 mmol), 2a (4.0 mmol), [RhCl-
(cod)]2 (0.10 mmol) in ethylcyclohexane (1.0 mL) at 130 °C, 15 h.
b Isolated yields. c [Rh(OMe)(cod)]2 was used as a catalyst. d A 10 mol
% concentration of the catalyst was used. e Run for 3 h.
Table 5. Rh(I)-Catalyzed Silylation Reaction of Benzyl Cyanidesa
Mechanistic Considerations. On the basis of the stoichio-
metric reaction reported by Bergman and Brookhard,12
a
possible mechanism that accounts for the silylation of C-CN
bonds is illustrated in Scheme 5. The reaction of a catalyst
precursor, such as [RhCl(cod)]2, with disilanes generates a
rhodium(I) silyl species, A′, via σ-bond metathesis or an
oxidative addition/reductive elimination sequence (step 0). As
supporting evidence for this step, chlorotrimethylsilane, which
should be generated, was observed by 29Si NMR measurement
of the stoichiometric reaction (see the Supporting Information
for details). Migration of the silyl group in A′ to the nitrogen
atom of the substrate nitrile affords an η2-iminoacyl complex,
isolated yields (%)
entry
R
temp (°C)
14b
15c
recovered 13b
1
2
3
4
5
6
7
8
9
4-OMe (a)
H (b)
4-CF3 (c)
4-CO2Me (d)
2-Me (e)
4-OMe (a)
H (b)
4-CF3 (c)
4-CO2Me (d)
2-Me (e)
100
100
100
100
100
160
160
160
160
160
38
43
35
33
20
68
52
59
35
63
0
0
0
34
36
0
0
0
0
trace
59
0
18
18
12
17
0
0
0
trace
Scheme 5. Possible Mechanism for Silylation of Aryl Cyanides
10
a Reaction conditions: benzyl cyanide 13 (2.0 mmol), 2a (4.0 mmol),
[RhCl(cod)]2 (0.10 mmol) in ethylcyclohexane (1.0 mL) for 15 h.
b Isolated yields. c Estimated by GC analysis.
benzyl cyanides were recovered in most cases, we decided to
conduct the reactions at a higher temperature. At 160 °C,
complete conversion was observed in all cases, and benzylsilanes
14 were obtained in satisfactory yields (entries 6-10). Interest-
ingly and importantly, the formation of enamine 15 (in which
a C-CN bond is not cleaved) as a minor product (0-18%)
was also observed in the silylation reaction of benzyl cyanides.
9
15986 J. AM. CHEM. SOC. VOL. 130, NO. 47, 2008

Rh-Catalyzed Silylation and Arylation of Nitriles
A R T I C L E S
Scheme 6. Mechanistic Rationale for the Silylation of Benzyl
Cyanides
B′ (step 1). Subsequent migration of the aryl group in B′ to a
rhodium center induces the cleavage of a C-C bond to form
an arylrhodium complex, C′ (step 2). σ-Bond metathesis
between an Ar-Rh bond in C′ and a Si-Si bond of disilane
produces an arylsilane product and a rhodium silyl complex,
A′, completing a catalytic cycle (step 3). As in step 0, a pathway
through a Rh(III) intermediate (i.e., an oxidative addition/
reductive elimination sequence) is also possible for step 3. The
coordinated silyl isocyanide, which is formed in step 2, should
be dissociated from a rhodium center in any of the steps for an
efficient catalysis. The dissociated silyl isocyanide should
isomerize, under the reaction conditions, to silyl cyanide, a more
thermodynamically stable isomer.22 Indeed, the formation of
trimethylsilyl cyanide was confirmed by 29Si NMR measurement
of the crude reaction mixture obtained from the Rh-catalyzed
reaction of 1 with 2a. Furthermore, part of the dissociated
trimethylsilyl cyanide could be trapped as cyanohydrin silyl
ether15c by stirring the crude reaction mixture with acetophenone
and I2 (see the Supporting Information for details).
In addition to rhodium(I) silyl species A′, a rhodium(III) silyl
complex, A′′, which could be formed by oxidative addition of
disilane to A′, is also a possible competent species for the
catalytic silylation of nitriles. An iridium complex related to
A′′ was proposed as a key intermediate in the catalytic silylation
of C-H bonds.23 No conclusive evidence is yet available
concerning which of these complexes is responsible for the
catalysis (A′ and/or A′′), although we have conducted several
NMR studies on the stoichiometric reaction of [RhCl(cod)]2 with
2a in the presence or absence of nitriles (see the Supporting
Information for details).
In relation to steps 1 and 2, Bergman and Brookhart
investigated the effect of para substituents on the rate of the
C-CN bond cleavage reaction of benzonitrile derivatives on a
rhodium complex.12b They documented that the silyl migration
reaction, which is related to step 1 in the present catalysis, is
relatively insensitive to the electronic nature of the benzonitrile
used. In contrast, the deinsertion of silyl isocyanide, which is
related to step 2 in our catalysis, is accelerated by an electron-
withdrawing group.24 They noted that the rate enhancement by
an electron-withdrawing group may be explained by destabiliza-
tion of the Rh-N interaction in B′ as well as the formation of
a stronger Ar-Rh bond in the transition state. On the other hand,
in the course of the examination of an array of nitriles in the
catalytic silylation, a similar electronic effect of nitrile substrates
on the overall rate was observed; the presence of electron-
withdrawing groups resulted in an increased rate. Although
neither experimental nor literature data concerning the sensitivity
of step 3 to electronic effects are available, the observed effect
of substituents can be well-rationalized by the assumption that
step 2 is the turnover-limiting step in the present catalysis.
On the other hand, a small electronic effect was observed in
the silylation of benzyl cyanides (Table 5). This might indicate
that the turnover-limiting step in these cases lies in a different
step than that in the reactions of aryl cyanides. The migratory
extrusion of silyl isocyanide, a plausible turnover-limiting step
in the case of aryl cyanides, is expected to be relatively facile
in the case of benzyl cyanides, since it has been reported that
the related migratory extrusion of carbon monoxide from
RhsC(dO)CH2Ph has a lower activation energy than that from
RhsC(dO)Ph.24 Another important observation of the reactions
of benzyl cyanides is the formation of enamine side product 15
(Table 5).25 Possible routes leading to enamine are provided in
Scheme 6. The η2-iminoacyl complex B″ serves as a common
intermediate for the formation of both benzylsilanes and
enamines. The reaction of complex B″ with disilane affords
iminosilane D and regenerates the active species A′ (path a).
This process (B″ f D) can be related to the acylsilane formation
process by the reaction of a metal acyl complex with disilane.26
The silyl group at the imino carbon atom in D then migrates to
the imino nitrogen atom via aza-Brook-type rearrangement to
give R-aminocarbene E or its metal-bound species.27 Finally,
insertion of the carbene moiety in E into a benzylic C-H bond
furnishes the observed enamine product. An alternate pathway
is initiated by ꢀ-hydrogen elimination from η2-iminoacyl
(25) For transition-metal-mediated synthesis of N,N-disilylenamines, see:
(a) Corriu, R. J. P.; Moreau, J. J. E.; Pataud-Sat, M. Organometallics
1985, 4, 623. (b) Murai, T.; Sakane, T.; Kato, S. J. Org. Chem. 1990,
55, 449.
(22) (a) Thayer, J. S. Inorg. Chem. 1968, 7, 2599. (b) Secker, J. A.; Thayer,
J. S. Inorg. Chem. 1976, 15, 501.
(23) (a) Ishiyama, T.; Sato, K.; Nishio, Y.; Miyaura, N. Angew. Chem.,
Int. Ed. 2003, 42, 5346. (b) Ishiyama, T.; Sato, K.; Nishio, Y.; Miyaura,
N. Chem. Commun. 2005, 5065. (c) Saiki, T.; Nishio, Y.; Ishiyama,
T.; Miyaura, N. Organimetallics 2006, 25, 6068.
(26) (a) Yamamoto, K.; Suzuki, S.; Tsuji, J. Tetrahedron Lett. 1980, 21,
1653–1656. (b) Eaborn, C.; Griffiths, R.; Pidcock, A. J. Organomet.
Chem. 1982, 225, 331. (c) Ricci, A.; Degl’Innocenti, A.; Chimichi,
S.; Fiorenza, M.; Rossini, G. J. Org. Chem. 1985, 50, 130. (d)
Yamamoto, K.; Hayashi, A.; Suzuki, S.; Tsuji, J. Organometallics
1987, 6, 974.
(24) A similar electronic effect was also observed in mechanistically related
rhodium-catalyzed decarbonylation of aldehydes: Fristrup, P.; Kreis,
M.; Palmelund, A.; Norrby, P.-O.; Madsen, R. J. Am. Chem. Soc. 2008,
130, 5206.
(27) Suginome, M.; Fukuda, T.; Ito, Y. J. Organomet. Chem. 2002, 643-
644, 508.
9
J. AM. CHEM. SOC. VOL. 130, NO. 47, 2008 15987

A R T I C L E S
Tobisu et al.
Scheme 7. Utilization of an ArylRhodium Complex for
Intramolecular Cyclizations
complex B″, resulting in the formation of ketene imine F (path
b).28 The eliminated rhodium hydride then adds to a CdN bond
in F to give a rhodium enamide intermediate, G. N-Silylation
of G with disilane produces an enamine and a rhodium silyl
complex, A′.
The yields of the enamine 15 were, in general, lower than
those of benzylsilane 14, and the formation of enamine was
observed at a higher temperature (160 °C). These results indicate
that the pathway leading to enamines is an energetically difficult
process, compared with that leading to benzylsilanes. To gain
more insight into the mechanism for the formation of enamines,
the silylation reaction of deuterated benzyl cyanide 13g was
examined (eq 7). In contrast to the results using nonlabeled
benzyl cyanide 13b, enamine 15g was not detected, while
benzylsilane 14g was obtained in 53% yield. This observation
suggests that there is a moderately large kinetic isotope effect
in the C-H bond cleavage step (E f enamine in path a or B″
f F in path b) and the deuterium elimination is not competitive
with silylation. In the case of silylation of 13f, the activation
energy for the C-H bond cleavage is lowered due to the
formation of more stable trisubstituted enamine 15f. Although
there is no firm evidence to distinguish paths a and b at this
point, we currently favor the latter mechanism involving
ꢀ-hydrogen elimination, since iminosilane D would be detected
during the course of the reaction if enamine is formed through
path a. Irrespective of the mechanism involved, a key point is
that the formation of the enamines strongly supports the
intermediacy of η2-iminoacyl complex B″ in the rhodium-
catalyzed C-CN bond cleavage reaction.
Table 6. Rhodium-Catalyzed Intramolecular Arylation of Nitrile 18a
isolated yields (%)
entry
X
ligand
19
20
recovered 18
1
2
3
Br
Cl
Cl
Cl
Cl
none
none
P(Oi-Pr)3
P(4-CF3C6H4)3
P(4-CF3C6H4)3
10
42
45
35
71
0 (57)b
10
6
trace
trace
0
40
31
61
27
4
5c
a Reaction conditions: 18 (0.5 mmol), 2a (1.0 mmol), [RhCl(cod)]2
(0.025 mmol), and ligand (0.050 mmol) in ethylcyclohexane (1.0 mL) at
130 °C, 15 h. b Yield of bis[2-(trimethylsilyl)phenyl] ether. c [RhCl-
(cod)]2 (0.050 mmol) was used.
undesired C-X bond silylation, although silylation at the C-CN
bond accompanied to give 20b in 10% yield (entry 2). Screening
of the ligand revealed that the addition of P(4-CF3C6H4)3
effectively suppressed the formation of 20b (entry 4). The yield
of the cyclization product 19 was improved by increasing the
catalyst loading without deteriorating the selectivity (entry 5).
Under these conditions, intramolecular arylation involving
C-CN bond cleavage proceeded with several substrates to
furnish tricyclic systems (Table 7). Substituted dibenzofurans
could be synthesized in satisfactory yields via the intramolecular
cross-coupling of aryl cyanides and aryl chlorides (entries 1-4).
An attempt to apply this methodology to a pyridine-containing
system failed under the standard conditions, probably due to
the catalyst deactivation through the coordination of pyridine
to rhodium. However, the addition of a catalytic amount of
InCl3, in place of P(4-CF3C6H4)3, dramatically increased the
yield of the product (entry 5). Since this acceleration effect of
InCl3 was not observed in other substrates shown in Table 7,
we consider that the effect is brought by the suppression of
catalyst deactivation through the coordination of pyridine to
InCl3, rather than by the nitrile activation.10e A nitrogen-tethered
substrate could also be applied successfully to form a carbazole
derivative (entry 6). In addition to aryl C-CN bonds, a benzylic
C-CN bond could be arylated under these conditions, providing
access to a fluorene framework (entry 7).
Intramolecular Arylation of Nitriles. As discussed above, we
postulated an arylrhodium intermediate (C′ in Scheme 5) in the
silylation of aryl cyanides. In view of a number of reactions of
such intermediates with diverse electrophiles,29,30 it was envis-
aged that the postulated arylrhodium species in the catalysis
should be intercepted by tethered electrophiles, such as enones,
aldehydes, and nitriles, resulting in an intramolecular cyclization
(Scheme 7).
To realize the carbon-carbon bond formation process
depicted in Scheme 7, a variety of tethered electrophiles were
examined. It was found that benzonitrile 18a, which contains a
bromophenyl moiety, afforded the desired cyclization product
19 in 10% yield (entry 1 in Table 6).31 However, the major
product was a disilylated compound in which both C-CN and
C-Br bonds were silylated. The use of the chloride analogue
18b increased the yield of 19 to 42% by suppressing the
(28) (a) Torii, S.; Okumoto, H.; Sadakane, M.; Hai, A. K. M. A.; Tanaka,
H. Tetrahedron Lett. 1991, 34, 6553. (b) Tanaka, H.; Hai, A. K. M. A.;
Sadakane, M.; Okumoto, H.; Torii, S. J. Org. Chem. 1994, 59, 3040.
(c) Zhou, Z.; Alper, H. J. Org. Chem. 1996, 61, 1256.
(29) Miura, T.; Murakami, M. Chem. Commun. 2007, 217. See also ref
19.
The construction of an aryl-aryl linkage is one of the most
important synthetic processes. The metal-catalyzed cross-
coupling reactions of aryl (pseudo)halides and arylmetal re-
agents, such as Grignard reagents and boronic acids, are
currently the methods of widespread utility.32 Considering the
(30) For our works along this line, see:(a) Harada, Y.; Nakanishi, J.;
Fujihara, H.; Tobisu, M.; Fukumoto, Y.; Chatani, N. J. Am. Chem.
Soc. 2007, 129, 5766. (b) Miyamoto, M.; Harada, Y.; Tobisu, M.;
Chatani, N. Org. Lett. 2008, 10, 2975.
(31) The reaction of arylrhodium species, generated from arylboron
compounds, with aryl halides leading to biaryls has been reported: Ueura,
K.; Satoh, T.; Miura, M. Org. Lett. 2005, 7, 2229.
(32) For a review on industrial application of metal-catalyzed cross-coupling
reactions, see: Corbet, J.-P.; Mignani, G. Chem. ReV. 2006, 106, 2651.
9
15988 J. AM. CHEM. SOC. VOL. 130, NO. 47, 2008

Rh-Catalyzed Silylation and Arylation of Nitriles
A R T I C L E S
Table 7. Rhodium-Catalyzed Intramolecular Arylation of Nitrilesa
the establishment of metal-catalyzed cross-coupling processes
that utilize aryl cyanides as nucleophilic coupling partners in
place of organometallic reagents.
Conclusion
We have developed a rhodium-catalyzed silylation of nitriles
with disilanes in which an unreactive C-CN bond is cleaved
in a catalytic manner. Under the catalytic conditions, a diverse
array of functional groups, including esters, amides, amines,
ethers, and boronic esters, as well as heterocycles, are tolerated.
In addition to the C-CN bonds of aryl, alkenyl, allyl, and benzyl
cyanides, those of alkyl cyanides, a challenging class of sub-
strates for the catalytic transformation, can be cleaved and
silylated with this catalytic system. One of the most intriguing
features of this reaction is the mechanism for the cleavage of
C-CN bonds. On the basis of related stoichiometric reactions,
it is proposed that the catalytic reaction proceeds through the
deinsertion of silyl isocyanide of η2-iminoacyl complex B′
(Scheme 5). The observation of enamine side products in the
silylation of benzyl cyanides also supports the intermediacy of
B′. This silicon-assisted strategy for the activation of C-CN
bonds is further applied to an intramolecular cyclization process
in which the Ar-Ar bond is constructed by the cross-coupling
reaction between Ar-CN and Ar-Cl. Current efforts are
directed toward further application of the postulated rhodium
silyl species to the cleavage of other unreactive bonds.35
Acknowledgment. This paper is dedicated to Professor Shinji
Murai on the occasion of his 70th birthday. This work has been
carried out via the Program of Promotion of Environmental
Improvement to Enhance Young Researchers’ Independence,
Special Coordination Funds for Promoting Science and Technology,
MEXT, Japan. This work was also supported by a Grant-in-Aid
for Science Research on Priority Areas (No. 19027037, Synergy
of Elements) from MEXT, Japan. M.T. acknowledges the General
Oil Foundation. We also thank the Instrumental Analysis Center,
Faculty of Engineering, Osaka University, for their assistance with
the MS, HRMS, and elemental analyses. We also acknowledge Prof.
Baba and Prof. Yasuda (Osaka University) for obtaining 29Si NMR
spectra.
a Reaction conditions: nitrile (0.5 mmol), 2a (1.0 mmol), [RhCl-
(cod)]2 (0.05 mmol), and P(4-CF3C6H4)3 (0.10 mmol) in ethylcyclo-
hexane (1.0 mL) at 130 °C, 15 h. b Isolated yield. c P(O-i-Pr)3 (0.10
mmol) was used in place of P(4-CF3C6H4)3. d InCl3 (0.10 mmol), in
place of P(4-CF3C6H4)3, and dioxane (2 mL), in place of ethyl-
cyclohexane, were used. A 6-7% yield of the silylated product was also
formed. e Run at 160 °C using 2a (2.0 mmol). f (2-Chlorophenyl)-
phenylamine was also obtained in 18% yield. g P(O-i-Pr)3 (0.10 mmol)
was used in place of P(4-CF3C6H4)3. Run at 160 °C for 40 h. h The
silylated product was also obtained in 15% yield.
Supporting Information Available: Complete experimental
procedures and characterization data for new compounds. This
material is available free of charge via the Internet at http://
pubs.acs.org.
cost, availability, and stability of the organometallic coupling
partners, recent efforts have been devoted to replacing the
organometallic reagents with simple organic compounds in such
cross-coupling reactions. Although simple arenes are the most
ideal coupling partners to this end, the issue of regioselectivity
must be addressed.33 In this context, decarboxylative coupling,
in which aryl carboxylic acids can serve as an aryl source in
the cross-coupling with aryl halides, represents a notable
method.34 The results shown in Table 7 lay the foundation for
JA804992N
(34) (a) Goossen, L. J.; Deng, G.; Levy, L. M. Science 2006, 313, 662–
664. (b) Forgione, P.; Brochu, M.-C.; St-Onge, M.; Thesen, K. H.;
Bailey, M. D.; Bilodeau, F. J. Am. Chem. Soc. 2006, 128, 11350. (c)
Goossen, L. J.; Rodriguez, N.; Melzer, B.; Linder, C.; Deng, G.; Levy,
L. M. J. Am. Chem. Soc. 2007, 129, 4824. (d) Goossen, L. J.; Melzer,
B. J. Org. Chem. 2007, 72, 7473. Becht, J.-M.; Catala, C.; LeDrian,
C.; Wagner, A. Org. Lett. 2007, 9, 1781. (e) Nakano, M.; Tsurugi,
H.; Satoh, T.; Miura, M. Org. Lett. 2008, 10, 1851.
(33) For recent reviews, see:(a) Alberico, D.; Scott, M. E.; Lautens, M.
Chem. ReV. 2007, 107, 174. (b) Seregin, I. V.; Gevorgyan, V. Chem.
Soc. ReV. 2007, 36, 1173. (c) Campeau, L.-C.; Stuart, D. R.; Fagnou,
K. Aldrichimica Acta 2007, 24. (d) Satoh, T.; Miura, M. Chem. Lett.
2007, 36, 200. (e) Li, B.-J.; Yang, S.-D.; Shi, Z.-J. Synlett 2008, 7,
949.
(35) C-F bond cleavage: (a) Ishii, Y.; Chatani, N.; Yorimitsu, S.; Murai,
S. Chem. Lett. 1998, 27, 157. C-H bond cleavage: (b) Tobisu, M.;
Ano, Y.; Chatani, N. Chem.sAsian J. 2008, 3, 1585.
9
J. AM. CHEM. SOC. VOL. 130, NO. 47, 2008 15989