Palladium-catalyzed disilylation of o-quinodimethanes: Synthesis of 9- and 10-membered disilacarbocycles

Article abstract of DOI:10.1021/ol801788t

(Chemical Equation Presented) 0-Quinodimethanes are efficiently inserted into a silicon-silicon bond of cyclic disilanes in the presence of a palladium-diphenyl-2-pyridylphosphine catalyst, giving 9- and 10-membered disilacarbocycles, that is, benzodisilonine and benzodisilecine.

Full text of DOI:10.1021/ol801788t

ORGANIC
LETTERS
2008
Vol. 10, No. 19
4319-4322
Palladium-Catalyzed Disilylation of
o-Quinodimethanes: Synthesis of 9- and
10-Membered Disilacarbocycles
Hiroto Yoshida,* Saori Nakano, Masashi Mukae, and Joji Ohshita
Department of Applied Chemistry, Graduate School of Engineering,
Hiroshima UniVersity, Higashi-Hiroshima 739-8527, Japan
yhiroto@hiroshima-u.ac.jp
Received August 1, 2008
ABSTRACT
o-Quinodimethanes are efficiently inserted into a silicon-silicon bond of cyclic disilanes in the presence of a palladium-diphenyl-2-
pyridylphosphine catalyst, giving 9- and 10-membered disilacarbocycles, that is, benzodisilonine and benzodisilecine.
Much attention has been directed to synthetic utilization of
o-quinodimethanes as an efficient 4-carbon unit in construct-
ing 6-membered carbocyclic frameworks via [4 + 2]
cycloaddition (Diels-Alder reaction).1 Although the wide
applicability of the cycloaddition enables diverse functional
molecules including steroids,2 alkaloids,3 polyacenes,4 and
fullerenes5 to be synthesized in a straightforward manner,
little has been known about a different type of transformation
using o-quinodimethanes,6,7 which would lead to production
of cyclic structures of other sizes, despite the significant
synthetic potential arising from their highly reactive char-
acter.
We have recently reported on the palladium-catalyzed
distannylation of o-quinodimethanes, which provides R,R′-
distannyl-o-xylenes of structural diversity, exemplifying that
the transient carbon-carbon double bond can undergo a
facile transition-metal-catalyzed insertion reaction into an
element-element σ-bond.8 In this context, we have been
investigating the synthetic utility of this protocol and have
found that a silicon-silicon bond of disilanes is likewise
added across o-quinodimethanes smoothly. Herein we dis-
close that o-quinodimethanes serve as an efficacious four-
(1) For reviews, see: (a) Oppolzer, W. Synthesis 1978, 793. (b) Charlton,
J. L.; Alauddin, M. M. Tetrahedron 1987, 43, 2873. (c) Martin, N.; Seoane,
C.; Hanack, M. Org. Prep. Proc. Int. 1991, 23, 237. (d) Segura, J. L.; Martin,
N. Chem. ReV. 1999, 99, 3199. (e) Oppolzer, W. In ComprehensiVe Organic
Synthesis; Trost, B. M., Fleming, I., Eds.; Pergamon: New York, 1991;
Vol. 5,Chapter 4.1, pp 385-396.
(5) (a) Belik, P.; Gu¨gel, A.; Spickermann, J.; Mu¨llen, K. Angew. Chem.,
Int. Ed. Engl. 1993, 32, 78. (b) Diederich, F.; Jonas, U.; Gramlich, V.;
Herrmann, A.; Ringsdorf, H.; Thilgen, C. HelV. Chim. Acta 1993, 76, 2445.
(c) Zhang, X.; Foote, C. S. J. Org. Chem. 1994, 59, 5235. (d) Belik, P.;
Gu¨gel, A.; Kraus, A.; Walter, M.; Mu¨llen, K. J. Org. Chem. 1995, 60, 3307.
(6) For polymerization of o-quinodimethanes, see: Chino, K.; Takata,
T.; Endo, T. Macromolecules 1997, 30, 6715.
(2) Nemoto, H.; Fukumoto, K. Tetrahedron 1998, 54, 5425.
(3) (a) Kametani, T.; Fukumoto, K. Acc. Chem. Res. 1976, 9, 319. (b)
Magnus, P.; Gallagher, T.; Brown, P.; Pappalardo, P. Acc. Chem. Res. 1984,
17, 35.
(7) For o-quinodimethanes as nitric oxide cheletropic traps, see: Korth,
H. G. In Free Radicals in Biology and EnVironment; Springer: New York,
1997; NATO ASI Series 3, Vol. 27, pp 331-349.
(4) Morris, J. L.; Becker, C. L.; Fronczek, F. R.; Daly, W. H.;
McLaughlin, M. L. J. Org. Chem. 1994, 59, 6484.
10.1021/ol801788t CCC: $40.75
Published on Web 09/05/2008
2008 American Chemical Society

Table 1. Palladium-Catalyzed Disilylation of
o-Quinodimethanes with 2aa
Scheme 1. Palladium-Catalyzed Disilylation of
o-Quinodimethanes with 2b-2e
entry
R
3
time (h)
yield (%)b
1
2
3
4
H (1a)
3-Ph (1b)
4-F (1c)
4-Cl (1d)
5-Me (1e)
6-Me (1f)
4,6-Me2 (1g)
3aa
3ba
3ca
3da
3ea
3fa
48
67
20
21
70
47
76
46
64
59
57
43
36
36
5c
6c
7c
3ga
a The reaction was carried out in dioxane (1 mL) at 40 °C using 1 (0.40
mmol), 2a (0.20 mmol), KF (0.74 mol), and 18-crown-6 (0.74 mmol) in
the presence of Pd(dba)2 (0.010 mmol) and Ph2P(2-Py) (0.010 mmol).
b Isolated yield based on 2a. c 60 °C.
carbon unit in constructing 9- and 10-membered disilacar-
bocycles, that is, benzodisilonine and benzodisilecine, through
palladium-catalyzed disilylation of 5- and 6-membered cyclic
disilanes.9,10
Disilylation of o-quinodimethanes, generated in situ
from 2-[(trimethylsilyl)methyl]benzyl phenyl carbonates
(1) and a fluoride ion,11,12 with naphthalene-fused di-
silacyclopentane 2a could be achieved by the use of a
catalytic amount of bis(dibenzylideneacetone)palladium-
diphenyl-2-pyridylphosphine complex, which is also effective
for the above distannylation. As depicted in Table 1, a
9-membered disilacarbocycle, benzodisilonine 3aa, was
formed straightforwardly via insertion of an exo-1,3-diene
moiety of simple o-quinodimethane (from 1a) into the
silicon-silicon bond of 2a (entry 1). Such substituted
o-quinodimethanes as 3-phenyl- (from 1b), 4-fluoro- (from
1c), or 4-chloro-o-quinodimethane (from 1d) took part in
the disilylation efficiently to afford the respective products
(3ba-3da) in 64%, 59%, or 57% yield (entries 2-4),
whereas the reaction using methyl-substituted o-quino-
dimethanes (from 1e-1g) became somewhat sluggish (entries
5-7).
The present insertion reaction was also applicable to
disilacyclopentane 2b, giving moderate yields of a ben-
zodisilonine (3ab or 3bb) (Scheme 1). Furthermore, a 10-
membered disilacarbocycle, benzodisilecine (3ac or 3bc),
could be synthesized by treatment of biphenyl-fused
disilacyclohexane 2c with o-quinodimethanes, while the
reaction of disilacyclohexane 2d furnished 3ad in only
8% yield. Although the yield was slightly lower than those
observed with cyclic disilanes, an acyclic disilane (2e)
participated in the reaction to provide a disilyl-o-xylene
(3ae).
(8) Yoshida, H.; Nakano, S.; Yamaryo, Y.; Ohshita, J.; Kunai, A. Org.
Lett. 2006, 8, 4157
.
(9) We have also reported catalytic insertion reactions of arynes into
an element-element σ-bond. (a) Yoshida, H.; Honda, Y.; Shirakawa, E.;
Hiyama, T. Chem. Commun. 2001, 1880. (b) Yoshida, H.; Ikadai, J.; Shudo,
M.; Ohshita, J.; Kunai, A. J. Am. Chem. Soc. 2003, 125, 6638. (c) Yoshida,
H.; Ikadai, J.; Shudo, M.; Ohshita, J.; Kunai, A. Organometallics 2005,
24, 156. (d) Ikadai, J.; Yoshida, H.; Ohshita, J.; Kunai, A. Chem. Lett. 2005,
34, 56. (e) Yoshida, H.; Tanino, K.; Ohshita, J.; Kunai, A. Angew. Chem.,
Int. Ed. 2004, 43, 5052. (f) Yoshida, H.; Tanino, K.; Ohshita, J.; Kunai, A.
(11) For pioneering works on the fluoride ion-induced generation of
o-quinodimethanes, see: (a) Ito, Y.; Nakatsuka, M.; Saegusa, T. J. Am.
Chem. Soc. 1980, 102, 863. (b) Ito, Y.; Nakatsuka, M.; Saegusa, T. J. Am.
Chem. Soc. 1982, 104, 7609.
Chem. Commun. 2005, 5678
.
(10) For reviews on catalytic insertion reactions of carbon-carbon
multiple bonds into an element-element σ-bond, see: (a) Beletskaya, I.;
Moberg, C. Chem. ReV. 1999, 99, 3435. (b) Suginome, M.; Ito, Y. Chem.
ReV. 2000, 100, 3221. (c) Beletskaya, I.; Moberg, C. Chem. ReV. 2006,
(12) Diels-Alder reaction of o-quinodimethanes using 2-[(trimethylsi-
lyl)methyl]benzyl acetate has been reported; see: (a) Askari, S.; Lee, S.;
Perkins, R. R.; Scheffer, J. R. Can. J. Chem. 1985, 63, 3526. (b) Kuwano,
R.; Shige, T. Chem. Lett. 2005, 34, 728.
106, 2320
.
4320
Org. Lett., Vol. 10, No. 19, 2008

Scheme 2
.
Disilylation via Cross-Coupling
Scheme 5. Plausible Catalytic Cycle
Because a benzylic carbonate moiety in 1 should be
prone to undergo a cross-coupling reaction with 2 in the
presence of a fluoride ion and a palladium catalyst,13,14
an o-quinodimethane intermediate might not be involved in
the present disilylation: cross-coupling of 1 at a C-OCO2Ph
moiety with 2 followed by fluoride-ion-induced silicon-
silicon exchange between the resulting 2-[(trimethylsilyl)-
methyl]benzylsilane and SiOCO2Ph (and/or SiOPh)
(Scheme 2). However, this pathway can be excluded
since the reaction using 1h or 1i, a regioisomer of 1a, did
not afford the respective products (Scheme 3). In addition,
carried out in the absence of the palladium catalyst. This
result also rules out a pathway where a fluoride ion acts as
a catalyst, as previously reported in the disilylation of 1,3-
dienes.15
These results prompt us to propose a catalytic cycle that
is triggered by formation of palladacycle 416 from an
o-quinodimethane and a Pd(0) complex (Scheme 5, Cycle
A). The resulting palladacycle then reacts with 2 to
produce benzylpalladium complex 5, which undergoes
reductive elimination of 3 with regenerating the Pd(0)
complex.17 Although metal-catalyzed disilylation of such
unsaturated carbon-carbon compounds as alkynes and
alkenes generally involves oxidative addition of 2 to a
Pd(0) complex as a key step,10b we are now in position
that Cycle A would be more plausible than Cycle B,
since a stoichiometric reaction of 2a with the Pd(0)-
Ph2P(2-Py) complex did not give oxidative adduct 6
(Scheme 6).
Scheme 3. Reaction Using 1h or 1i
In conclusion, disilylation of o-quinodimethane has been
accomplished by use of a palladium-Ph2P(2-Py) complex,
(13) (a) Matsumoto, H.; Nagashima, S.; Yoshihiro, K.; Nagai, Y. J.
Organomet. Chem. 1975, 85, C1. (b) Azarian, D.; Dua, S. S.; Eabornand,
C.; Walton, D. R. M. J. Organomet. Chem. 1976, 117, C55. (c) Matsumoto,
H.; Yoshihiro, K.; Nagashima, S.; Watanabe, H.; Nagai, Y. J. Organomet.
Chem. 1977, 128, 409. (d) Hatanaka, Y.; Hiyama, T. Tetrahedron Lett.
1987, 28, 4715. (e) Shirakawa, E.; Kurahashi, T.; Yoshida, H.; Hiyama, T.
Chem. Commun. 2000, 1895.
Scheme 4 describes the indispensability of the palladium
catalysis for the disilylation. Thus, disilylation product 3aa
was not formed at all when the reaction of 1a with 2a was
(14) For palladium-catalyzed cross-couplings of benzylic carbonates, see:
(a) Kuwano, R.; Yokogi, M. Org. Lett. 2005, 7, 945. (b) Kuwano, R.; Yu,
J.-Y. Heterocycles 2007, 74, 233. (c) Nakao, Y.; Ebata, S.; Chen, J.;
Imanaka, H.; Hiyama, T. Chem. Lett. 2007, 36, 606. (d) Ohsumi, M.;
Kuwano, R. Chem. Lett. 2008, 37, 796.
(15) Hiyama, T.; Obayashi, M.; Mori, I.; Nozaki, H. J. Org. Chem. 1983,
48, 912.
Scheme 4
.
Reaction of 1a with 2a in the Absence of the
Palladium Catalyst
(16) Palladacycle 4 has been reported to be a key intermediate in
palladium-catalyzed formal [4 + 2] cycloaddition of o-quinodimethanes
with olefins. Kuwano, R.; Shige, T. J. Am. Chem. Soc. 2007, 129, 3802.
(17) For palladium-catalyzed carbostannylation of alkynes or arynes,
which proceeds through a palladacycle, see: (a) Shirakawa, E.; Yoshida,
H.; Nakao, Y.; Hiyama, T. J. Am. Chem. Soc. 1999, 121, 4290. (b) Yoshida,
H.; Shirakawa, E.; Nakao, Y.; Honda, Y.; Hiyama, T. Bull. Chem. Soc.
Jpn. 2001, 74, 637. (c) Matsubara, T. Organometallics 2003, 22, 4297.
Org. Lett., Vol. 10, No. 19, 2008
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and various 9- and 10-membered disilacarbocycles, which
would be otherwise difficult to be synthesized, are accessible
directly. Further studies on catalytic insertion reactions of
o-quinodimethanes into other element-element σ-bonds are
in progress in our laboratory.
Scheme 6. Stoichiometric Reaction of 2a with Pd-Ph2P(2-Py)
Supporting Information Available: Experimental pro-
cedure and characterization of products. This material is
available free of charge via the Internet at http://pubs.acs.org.
OL801788T
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