Intramolecular σ-bond metathesis between carbon-carbon and silicon-silicon bonds

Article abstract of DOI:10.1021/ol301280u

An intramolecular σ-bond metathesis between carbon-carbon and silicon-silicon bonds took place on treatment of a disilane tethered to a cyclobutanone with a palladium(0) catalyst, furnishing a silaindane skeleton as well as an acylsilane functionality at

Full text of DOI:10.1021/ol301280u

ORGANIC
LETTERS
2012
Vol. 14, No. 12
3230–3232
Intramolecular σ-Bond Metathesis
Between CarbonꢀCarbon and
SiliconꢀSilicon Bonds
Naoki Ishida, Wataru Ikemoto, and Masahiro Murakami*
Department of Synthetic Chemistry and Biological Chemistry, Kyoto University,
Katsura, Kyoto 615-8510, Japan
murakami@sbchem.kyoto-u.ac.jp
Received May 9, 2012
ABSTRACT
An intramolecular σ-bond metathesis between carbonꢀcarbon and siliconꢀsilicon bonds took place on treatment of a disilane tethered to a
cyclobutanone with a palladium(0) catalyst, furnishing a silaindane skeleton as well as an acylsilane functionality at once.
The reactivities inherent in most organic compounds
reside in their π-bonds or polar σ-bonds. On the other
hand, in the past decade, organic chemists have devoted
keen and ever-increasing attention to reactions involving
direct cleavage of nonpolar σ-bonds1 such as a carbonꢀ
hydrogen bond from a synthetic perspective.2 Such reac-
tions are not only of scientific novelty but also of consider-
able potential to improve the efficiency of synthesis. We
describe herein the palladium-catalyzed intramolecular
σ-bond metathesis3 between carbonꢀcarbon4ꢀ6 and
siliconꢀsilicon single bonds.7 The unique swapping of
the group of 14 elements takes place on treatment of a
disilane tethered to a cyclobutanone8 with a palladium(0)
(5) For σ-bond metathesis between carbonꢀcarbon and siliconꢀ
silicon bonds, see: (a) Tobisu, M.; Kita, Y.; Ano, Y.; Chatani, N. J.
Am. Chem. Soc. 2008, 130, 15982. (b) Matsuda, T.; Kirikae, H. Orga-
nometallics 2011, 30, 3923. See also: Pohlmann, T.; de Meijere, A. Org.
Lett. 2000, 2, 3877.
(6) For selected examples of σ-bond metathesis of carbonꢀcarbon
€
bonds, see: (a) Eisch, J. J.; Piotrowski, A. M.; Han, K. I.; Kruger, C.;
(1) Activation of Unreactive Bonds and Organic Synthesis; Murai, S.,
Ed.; Springer: Berlin, 1999.
Tsay, Y. H. Organometallics 1985, 4, 224. (b) Schwager, H.; Spyroudis,
S.; Vollhardt, K. P. C. J. Organomet. Chem. 1990, 382, 191. (c) Edelbach,
B. L.; Jachicotte, R. J.; Jones, W. D. J. Am. Chem. Soc. 1998, 120, 2843.
(d) Suginome, M.; Matsuda, T.; Ito, Y. J. Am. Chem. Soc. 2000, 122,
11015. (e) Nakazawa, H.; Itazaki, M.; Kamata, K.; Ueda, K. Chem.
Asian J. 2007, 2, 882. (f) Nakai, K.; Kurahashi, T.; Matsubara, S. J. Am.
Chem. Soc. 2011, 133, 11066. (g) Tobisu, M.; Kunita, H.; Kita, Y.;
Remond, E.; Chatani, N. J. Am. Chem. Soc. 2012, 134, 115. See also:
Saito, S.; Yoshizawa, T.; Ishigami, S.; Yamasaki, R. Tetrahedron Lett.
2010, 51, 6028 and references cited therein.
(7) For σ-bond metathesis of siliconꢀsilicon bonds, see: (a) Sakurai,
H.; Hosomi, A. J. Organomet. Chem. 1972, 36, C15. (b) Tamao, K.;
Hayashi, T.; Kumada, M. J. Organomet. Chem. 1976, 124, C19. (c)
Ishikawa, M.; Okazaki, S.; Naka, A.; Sakamoto, H. Organometallics
1992, 11, 4135. (d) Kusukawa, T.; Kabe, Y.; Nestler, B.; Ando, W.
Organometallics 1995, 14, 2556. (e) Suginome, M.; Oike, H.; Ito, Y.
J. Am. Chem. Soc. 1995, 117, 1665. (f) Sun, H.; Pan, Y.; Huang, X.; Guo,
Z.; Zhang, Z.; Zhang, H.; Li, J.; Wang, F. Organometallics 2006, 25, 133
and references cited therein.
(8) For transition-metal-catalyzed reaction involving cleavage of a
carbonꢀcarbon bond of cyclobutanones, see: (a) Murakami, M.; Amii,
H.; Shigeto, K.; Ito, Y. J. Am. Chem. Soc. 1996, 118, 8285. (b)
Murakami, M; Itahashi, T.; Ito, Y. J. Am. Chem. Soc. 2002, 124,
13976. (c) Liu, L.; Ishida, N.; Murakami, M. Angew. Chem., Int. Ed.
2012, 51, 2485 and references cited therein.
(2) (a) Handbook of CꢀH Transformations; Dyker, G., Ed.; Wiley-
VCH: Weinheim, 2005. (b) Kakiuchi, F.; Kochi, T. Synthesis 2008, 3013. (c)
Daugulis, O.; Do, H.-Q.; Shabashov, D. Acc. Chem. Res. 2009, 42, 1074.
(d) Giri, R.; Shi, B.-F.; Engle, K. M.; Maugel, N.; Yu, J.-Q. Chem. Soc.
Rev. 2009, 38, 3242. (e) Colby, D. A.; Bergman, R. G.; Ellman, J. A.
Chem. Rev. 2010, 110, 624. (f) Mkhalid, I. A. I.; Barnard, J. H.; Marder,
T. B.; Murphy, J. M.; Hartwig, J. F. Chem. Rev. 2010, 110, 890. (g)
Lyons, T. W.; Sanford, M. S. Chem. Rev. 2010, 110, 1147. (h) Xu, L.-M.;
Li, B.-J.; Yang, Z.; Shi, Z.-J. Chem. Soc. Rev. 2010, 39, 712. (i)
Ackermann, L. Chem. Commun. 2010, 46, 4866. (j) Rauf, W.; Hazari,
A.; Gouverneur, V.; Brown, J. M. Pure Appl. Chem. 2010, 82, 1415. (k)
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ꢁ
(3) For alkene metathesis, see: Handbook of Metathesis; Grubbs,
R. H., Ed.; Wiley-VCH: Weinheim, 2003.
(4) For reviews on transition metal-catalyzed cleavage of car-
bonꢀcarbon bonds, see: (a) Miura, M.; Satoh, T. Top. Organomet.
Chem. 2005, 14, 1. (b) Kondo, T.; Mitsudo, T. Chem. Lett. 2005, 34,
ꢀ
1462. (c) Necas, D.; Kotora, M. Curr. Org. Chem. 2007, 11, 1566. (d)
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r
10.1021/ol301280u
Published on Web 05/31/2012
2012 American Chemical Society

catalyst, simultaneously giving rise to a silaindane skeleton
as well as an acylsilane functionality.
Scheme 1. Proposed Mechanism
Disilane 1a, which was tethered to a cyclobutanone
unit through an o-phenylene linker, was prepared from
o-bromo-R-methylstyrene through introduction of a dis-
ilanyl group followed by a standard [2 þ 2]-cycloaddition
reaction with dichloroketene.9 The disilane 1a thus obtained
was treated with 5 mol % of CpPd(π-allyl) and 20 mol % of
10
P(n-Bu)3 in p-xylene at 130 °C (eq 1). After 60 h, the
acylsilane 2a was isolated in 81% yield together with the
decarbonylated alkylsilane 3a (16%). The structure of
2a was elucidated by a comprehensive set of NMR spectra
(1H, 13C, DEPT, COSY, HMQC, HMBC, and NOESY)
and finally verified by derivatization to the known nitrile.9
regeneration of palladium(0).15,16 The other is a decarbo-
nylation/reductive elimination pathway which leads to the
formation of alkylsilane 3a.17
Cyclopropane 4, which was produced through direct
decarbonylation of the cyclobutanone unit under the
rhodium-catalyzed reaction conditions,8a,18 was not ob-
served in the reaction mixture. Furthermore, the simple
cyclobutanone lacking a disilanyl group 5 remained intact
underthepresentpalladium-catalyzedreaction conditions.
These experimental results suggested that initial activation
of the cyclobutanone prior to the disilane activation was
unlikely. Instead, we assume that the siliconꢀsilicon bond
is initially activated to locate the palladium(II) center in
close proximity to the carbonꢀcarbon bond next to the
carbonyl, inducing its oxidative addition.
Thus, both the siliconꢀsilicon σ-bond of the disilanyl
group and the carbonꢀcarbon σ-bond of the cyclobuta-
none unit were cleaved, and the originally bonded group of
14elementswereswappedtoresultin σ-bond metathesis. It
necessitates cleavage of both the carbonꢀcarbon and
siliconꢀsilicon linkages. Depicted in Scheme 1 is a possible
mechanistic scenario. Oxidative addition of the sili-
conꢀsilicon bond onto palladium(0) generates bis-
silylpalladium(II) A,7,11 in which the palladium(II) center
is located in close proximity to the cyclobutanone unit. The
σ-bond between the carbonyl carbon and the R-carbon
undergoesoxidativeadditionontothe palladium(II) center
to give rise to bicyclic palladium(IV) intermediate B.12,13
Reductive elimination of the sp3 carbonꢀsilicon bond
furnishes the (R-silaindan-3-ylacetyl)silylpalladium(II)
C,14 which then follows two pathways. One is direct
reductive elimination to afford acylsilane 2a with
Various disilanes having phenylene-type linkers success-
fully underwent the σ-bond metathesis to afford the corre-
sponding silaindanes in good yields (Table 1). Both electron-
donating and -withdrawing substituents were allowed on the
phenylene linker (entries 1 and 2). A thiophene linker also
worked to give 2e (entry 4). For the substituents at the
3-positions of the cyclobutanones, functionalized alkyl as
(9) See the Supporting Information for details.
(10) No reaction occurred, and the starting disilane 1a was recovered
when other palladium(0) precursors (e.g., Pd(dba)2 and Pd(OAc)2) and/
or ligands (e.g., P(t-Bu)3, IPr, and 1,1,3,3-tetramethylbutyl isocyanide)
were employed. Better reproducibility was observed with the use of 20
mol % of P(n-Bu)3, although 10 mol % was generally enough.
(11) For direct observation of oxidative addition of a siliconꢀsilicon
bond onto palladium(0), see: (a) Eaborn, C.; Griffiths, R. W.; Pidcock,
A. J. Organomet. Chem. 1982, 225, 331. (b) Biershenk, T. R.; Guerra,
M. A.; Juhlke, T. J.; Larson, S. B.; Lagow, R. J. J. Am. Chem. Soc. 1987,
109, 4855. (c) Murakami, M.; Yoshida, Y.; Ito, Y. Organometallics 1994,
13, 2900. (d) Ozawa, F.; Sugawara, M.; Hayashi, T. Organometallics
1994, 13, 3237. (e) Suginome, M.; Oike, H.; Shuff, P. H.; Ito, Y.
Organometallics 1996, 15, 2170.
(12) For palladium(IV) complexes with silyl ligands, see: (a) Shimada,
S.; Tanaka, M.; Shiro, M. Angew. Chem., Int. Ed. 1996, 35, 1856. (b)
Suginome, M.; Kato, Y.; Takeda, N.; Oike, H.; Ito, Y. Organometallics
1988, 17, 495.
(13) For a general review on palladium(IV) complexes, see: Sehnal,
P.; Taylor, R. J. K.; Fairlamb, I. J. S. Chem. Rev. 2010, 110, 824.
(14) An another conceivable mechanism from intermediate A to C
is a direct σ-bond exchange between carbonꢀcarbon and siliconꢀ
palladium bonds.
(15) For reactions of acyl chlorides with disilanes giving acylsilanes
and/or decarbonylated products, see: (a) Yamamoto, K.; Hayashi, A.;
Suzuki, S.; Tsuji, J. Organometallics 1987, 6, 974. (b) Rich, J. D. J. Am.
Chem. Soc. 1989, 111, 5886. (c) Kashiwabara, T.; Tanaka, M. Organo-
metallics 2006, 25, 4648.
(16) A pathway involving initial reductive elimination of the acyl
carbonꢀtrimethylsilyl bond and subsequent reductive elimination of the
sp2 carbonꢀsilicon bond is also conceivable for production of 2a.
(17) No decarbonylation was observed when isolated acylsilane 3a
was subjected to the palladium-catalyzed reaction conditions. For
palladium-catalyzed decarbonylation of bis(organosilyl) ketones, see:
Sakurai, H.; Yamane, M.; Iwata, M.; Saito, N.; Narasaka, K. Chem.
Lett. 1996, 25, 841.
(18) When cyclobutanone 1a was treated with 5 mol % of
[Rh(cod)dppp]PF6 in p-xylene at 130 °C for 60 h, cyclopropane 4 was
obtained in 34% yield.
Org. Lett., Vol. 14, No. 12, 2012
3231

Reactivities peculiar to acylsilanes were briefly examined
using the product 2a. For example, irradiation with UV light
(λ = 360 nm) generated a siloxycarbene species with the
arylꢀSi linkage remaining intact (eq 2). The resulting carbene
underwent insertion into water and the following elimination
of trimethylsilanol afforded aldehyde 6 in 73% isolated yield
based upon 2a.20 Addition of phenyllithium to 2a prompted
the Brook rearrangement to give a carbanion (eq 3).21 Sub-
sequent methylation with methyl iodide afforded tert-alkyl
silyl ether 7 as a mixture of diastereomer (1.9:1). These
transformations demonstrated that the acylsilanes produced
by the present σ-bond metathesis serve as versatile platforms
for the synthesis of functionalized silaindane derivatives.
Table 1. Palladium-Catalyzed σ-Bond Metathesis between
CarbonꢀCarbon and SiliconꢀSilicon Linkagesa
In summary, we have presented a unique example of the
σ-bond metathesis reaction between carbonꢀcarbon and
siliconꢀsilicon bonds. The process involves activation of
carbonꢀcarbon and siliconꢀsilicon σ-bonds, which are
both far less reactive than π-bonds or polar σ-bonds.
Whereas the full potential awaits further exploration, the
present reaction provides a prototype of a highly atom-
economical method, which dispenses with a substitution
process, for the synthesis of organosilicon compounds.
Acknowledgment. This work was supported in part by a
Grant-in-Aid for Scientific Research on Innovative Areas
“Molecular Activation Directed toward Straightforward
Synthesis” and Grant-in-Aid for Scientific Research (B)
from MEXT and The Asahi Glass Foundation.
Note Added after ASAP Publication. Equation 3 con-
tained an error in the version published ASAP May 31,
2012. The correct version reposted June 4, 2012.
a Reaction conditions: 5 mol % of CpPd(π-allyl), 20 mol % of P(n-
Bu)3, p-xylene (0.1 M), 130 °C, 60 h unless otherwise noted. b Isolated
yields. c 10 mol % of CpPd(π-allyl) and 40 mol % of P(n-Bu)3 were used.
Supporting Information Available. Experimental proce-
dures and spectral data for new compounds. This material is
available free of charge via the Internet at http://pubs.acs.org.
well as phenyl groups were suitable (entries 6ꢀ8). The
disilane having a hydrogen atom there, however, gave the
corresponding silaindane in only 20% yield.19
(20) Wegert, A.; Behr, J.-B.; Hoffmann, N.; Miethchen, R.; Portella,
C.; Plantier-Royon, R. Synthesis 2006, 2343 and references cited therein.
(21) Reich, H. J.; Olson, R. E.; Clark, M. C. J. Am. Chem. Soc. 1980,
102, 1423.
(19) Most of the starting material remained. The contrast in reactiv-
ity may indicate that the ThorpeꢀIngold effect reinforces the proximity
effect.
The authors declare no competing financial interest.
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Org. Lett., Vol. 14, No. 12, 2012