Palladium-catalyzed distannylation of ortho-quinodimethanes

Article abstract of DOI:10.1021/ol0617345

An exo-diene moiety of various ortho-quinodimethanes, regardless of its transient character, was inserted into a Sn-Sn σ-bond of hexabutyldistannane in the presence of a palladium catalyst, giving α,α′-bis(tributylstannyl)-o-xylenes straightforwardly.

Full text of DOI:10.1021/ol0617345

ORGANIC
LETTERS
2006
Vol. 8, No. 18
4157-4159
Palladium-Catalyzed Distannylation of
ortho-Quinodimethanes
Hiroto Yoshida,* Saori Nakano, Yasuhito Yamaryo, Joji Ohshita, and
Atsutaka Kunai*
Department of Applied Chemistry, Graduate School of Engineering, Hiroshima
UniVersity, Higashi-Hiroshima 739-8527, Japan
yhiroto@hiroshima-u.ac.jp; akunai@hiroshima-u.ac.jp
Received July 14, 2006
ABSTRACT
An exo-diene moiety of various ortho-quinodimethanes, regardless of its transient character, was inserted into
a Sn−Sn σ-bond of
hexabutyldistannane in the presence of a palladium catalyst, giving
r,r′-bis(tributylstannyl)-o-xylenes straightforwardly.
o-Quinodimethanes are recognized as potent reactive inter-
mediates in organic synthesis,1 which have been utilized for
preparing steroids,1d alkaloids,2 polyacenes,3 modified
fullerenes,4 etc. These transformations are based on [4+2]
cycloadditions (Diels-Alder reaction),1f in which o-quino-
dimethanes act as dienes, and thus, little attention has been
focused on their utilization for other types of reactions,
despite their great synthetic potential.5,6
demonstrating that the transient carbon-carbon triple bond
species can be applied to the catalytic insertion reaction into
an element-element σ-bond.10 Taking into account that
o-quinodimethanes also hold a transient carbon-carbon
unsaturated bond like arynes, we envisioned that o-quino-
dimethanes would be inserted into an element-element
σ-bond with the aid of a transition-metal catalyst. Herein,
we disclose the first demonstration of element-element
σ-bond addition to o-quinodimethanes, that is, palladium-
catalyzed distannylation (Scheme 1).11
We have already reported on palladium-catalyzed car-
bostannylation,7 disilylation,8 and distannylation9 of arynes,
(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) Nemoto, H.;
Fukumoto, K. Tetrahedron 1998, 54, 5425. (e) Segura, J. L.; Martin, N.
Chem. ReV. 1999, 99, 3199. (f) Oppolzer, W. In ComprehensiVe Organic
Synthesis; Trost, B. M., Fleming, I., Eds.; Pergamon: New York, 1991;
Vol. 5, Chapter 4.1, pp 385-396.
Scheme 1
(2) (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.
We first examined the reaction of simple o-quino-
dimethane, generated in situ from 2-[(trimethylsilyl)methyl]-
benzyl phenyl carbonate (1a) and a fluoride ion,12-14 with
hexabutylditin (2) in the presence of bis(dibenzylidene-
(3) Morris, J. L.; Becker, C. L.; Fronczek, F. R.; Daly, W. H.;
McLaughlin, M. L. J. Org. Chem. 1994, 59, 6484.
(4) (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.
(5) For polymerization of o-quinodimethanes, see: Chino, K.; Takata,
T.; Endo, T. Macromolecules 1997, 30, 6715.
(6) For o-quinodimethanes as nitric oxide cheletropic traps, see: Korth,
H. G. Free Radicals in Biology and EnVironment; NATO ASI Series 3;
Plenum: New York, 1997; Vol. 27, pp 331-349.
(7) Yoshida, H.; Honda, Y.; Shirakawa, E.; Hiyama, T. Chem. Commun.
2001, 1880.
(8) (a) Yoshida, H.; Ikadai, J.; Shudo, M.; Ohshita, J.; Kunai, A. J. Am.
Chem. Soc. 2003, 125, 6638. (b) Yoshida, H.; Ikadai, J.; Shudo, M.; Ohshita,
J.; Kunai, A. Organometallics 2005, 24, 156. (c) Ikadai, J.; Yoshida, H.;
Ohshita, J.; Kunai, A. Chem. Lett. 2005, 34, 56.
10.1021/ol0617345 CCC: $33.50
© 2006 American Chemical Society
Published on Web 07/28/2006

acetone)palladium-diphenyl-2-pyridylphosphine (Ph2P(2-Py))
and observed that the exo-diene moiety was inserted into
the Sn-Sn σ-bond to produce the distannylation product,
R,R′-bis(tributylstannyl)-o-xylene (3a) in 55% yield (Scheme
2). The reactions using other o-quinodimethane precursors
Scheme 3
Scheme 2
proceed. Similarly to the case of simple o-quinodimethane,
the reaction of o-quinodimethane bearing a naphthalene
backbone (from 1b) or 3-phenyl-o-quinodimethane (from 1c)
proceeded smoothly to give the distannylation product (3b
or 3c) in 63% or 59% yield. Methyl-substituted o-quino-
dimethanes (from 1d-1f) or 4-fluoro-o-quinodimethane
(from 1g) also underwent the addition of 2, affording
moderate yields of the respective products (3d-3g). Fur-
thermore, a methyl group of R-methyl-o-quinodimethane
(from 1h) did not inhibit the course of the distannylation to
furnish 3h in 64% yield.16
Because 1 has electrophilic (C-OCO2Ph) and nucleophilic
(C-SiMe3) sites at each benzylic position, the distannylation
might proceed through a pathway which does not involve
an o-quinodimethane intermediate: cross-coupling of 1 at a
C-OCO2Ph moiety with 217 followed by fluoride ion-
induced tin-silicon exchange between the resulting 2-[(tribu-
tylstannyl)methyl]benzylsilane and Bu3SnOCO2Ph (and/or
Bu3SnOPh).18 Therefore, we examined the reaction of 1i or
1j, a regioisomer of 1a, and observed that no trace of the
respective product was formed, which eliminates the cross-
coupling pathway in the distannylation (Scheme 3).19
or ligands also gave 3a, although the yields were rather low.15
The distannylation product was not formed at all in the
absence of the palladium catalyst or the fluoride ion, which
confirms that both of them are essential for the reaction to
On the basis of the above result, we propose cycle A,
which includes the formation of palladacycle 420 from a Pd-
(9) (a) Yoshida, H.; Tanino, K.; Ohshita, J.; Kunai, A. Angew. Chem.,
Int. Ed. 2004, 43, 5052. (b) Yoshida, H.; Tanino, K.; Ohshita, J.; Kunai, A.
Chem. Commun. 2005, 5678.
Scheme 4
(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,
106, 2320.
(11) Palladium-catalyzed distannylations of other carbon-carbon multiple
bonds have been reported. For alkynes, see: (a) Mitchel, T. N.; Amamria,
A.; Killing, H.; Rutschow, D. J. Organomet. Chem. 1983, 241, C45. (b)
Piers, E.; Skerlj, R. T. J. Chem. Soc., Chem. Commun. 1986, 626. (c)
Mancuso, J.; Lautens, M. Org. Lett. 2003, 5, 1653. For 1,3-dienes, see:
(d) Tsuji, Y.; Kakehi, T. J. Chem. Soc., Chem. Commun. 1992, 1000. For
allenes, see: (e) Killing, H.; Mitchell, T. N. Organometallics 1984, 3, 1318.
(12) Generation of o-quinodimethane from 1a has been confirmed by
the Diels-Alder reaction with methyl acrylate; see Supporting Information
for details.
(13) 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.
(14) The Diels-Alder reaction using 2-[(trimethylsilyl)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.
(15) See Supporting Information for details.
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Org. Lett., Vol. 8, No. 18, 2006

(0) complex and o-quinodimethane (Scheme 4). Subsequent
reaction of 4 with 2 produces benzylpalladium complex 5,
followed by reductive elimination giving the product with
regeneration of the Pd(0) complex.21 Although the stoichio-
metric reaction of the Pd(0) complex with 2 did not afford
an oxidative adduct (6) in contrast to the case with a Pd-
isocyanide complex (Scheme 5),9a we cannot entirely rule
Scheme 6
Scheme 5
out the possibility that the distannylation proceeds through
oxidative addition of 2 to the Pd(0) complex (cycle B).
Synthetic transformation of the distannylation product is
briefly described in Scheme 6. Iododestannylation of 3a gave
R,R′-diiodo-o-xylene (7) in 43% yield. Moreover, the io-
dodestannylation combined with the reaction using an active
methylene compound furnished 8 or 9 in one pot, although
the yields were rather low.22
In conclusion, we have demonstrated that a variety of
o-quinodimethanes, regardless of their transient character,
can be applied for catalytic distannylation by use of the
appropriate catalyst and precursor. Further studies on catalytic
reactions of o-quinodimethanes involving unreactive σ-bond
cleavage, on synthetic transformation of distannylation
products, and on details of the reaction mechanism are in
progress.
(16) The major side product in the distannylation was tetrabutyltin.
(17) For the palladium-catalyzed cross-coupling of organic halides with
distannanes, see: (a) Hitchcock, S. A.; Mayhugh, D. R.; Gregory, G. S.
Tetrahedron Lett. 1995, 36, 9085. (b) Stork, G.; Isaacs, R. C. A. J. Am.
Chem. Soc. 1990, 112, 7399.
(18) Warner, B. P.; Buchwald, S. L. J. Org. Chem. 1994, 59, 5822.
(19) Although the precursor (1i or 1j) was totally consumed, most of 2
remained intact with some formation of tetrabutyltin.
(20) Transition-metal o-quinodimethane complexes: (a) Ku¨ndig, E. P.;
Leresche, J. Tetrahedron 1993, 49, 5599. (b) Bennett, M. A.; Bown, M.;
Hockless, D. C. R.; McGrady, J. E.; Schranz, H. W.; Stranger, R.; Willis,
A. C. Organometallics 1998, 17, 3784. (c) Bennett, M. A.; Bown, M.;
Byrnes, M. J. J. Organomet. Chem. 1998, 571, 139. (d) Ca´mpora, J.; Graiff,
C.; Palma, P.; Carmona, E.; Tiripicchio, A. Inorg. Chim. Acta 1998, 269,
191.
(21) A palladacycle has been reported to be an intermediate species in
the palladium-catalyzed element-element σ-bond additions. For carbostan-
nylation of alkynes or arynes, 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. For
disilylation and distannylation of arynes, see refs 8b and 9.
Supporting Information Available: Experimental pro-
cedures and characterization of products. This material is
available free of charge via the Internet at http://pubs.acs.org.
OL0617345
(22) Ridvan, L.; Za´vada, J. Tetrahedron 1997, 53, 14793.
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