Stille cross-coupling of activated alkyltin reagents under "ligandless" conditions

Article abstract of DOI:10.1021/jo047907q

(Chemical Equation Presented) Monoalkyltins activated by a fluoride source are shown to be as reactive as their vinyl or aryl homologues in the Stille coupling reaction, thus providing an easy entry into the pallado-catalyzed formation of Csp³-Csp² bonds. In addition to this uncommon reactivity, this methodology holds several advantages such as (i) a quantitative preparation of stable and easy to handle alkyltin reagents 2, (ii) a simplified coupling procedure without any phosphine added ligand under neutral conditions, and (iii) a facile purification step of the organic products from the inorganic nontoxic tin byproducts.

Full text of DOI:10.1021/jo047907q

easiness of use, wide scope of reactions, and efficiency of
the catalytic system.6 In most cases, these works appear
to be closely related to the use of special ligands or
additives as well as careful optimization of the reaction
conditions,7 in order to overcome the reluctance of alkyl
halides to undergo oxidative addition and to suppress the
tendency of the resulting alkyl-metal intermediate for
destructive â-hydride elimination. Interestingly, the
construction of Csp2-Csp3 bonds implies essentially alkyl
halides or triflates as substrates, the alkenyl or aromatic
moieties being brought by the organometallic reagent.
Stille Cross-Coupling of Activated Alkyltin
Reagents under “Ligandless” Conditions
Agnes Herve, Alain L. Rodriguez, and Eric Fouquet*
Laboratoire de Chimie Organique et Organome´tallique,
UMR5802, Universite´ Bordeaux1,
351, Cours de la Libe´ration, 33405 Talence Cedex, France
e.fouquet@lcoo.u-bordeaux1.fr
Received November 24, 2004
However, a few recent examples can be found of
pallado-catalyzed cross-coupling reactions with alkyl-
organoboranes,8 dialkylzincs,9 Grignard reagents,10 or
alkylorganoindiums.11 Contrary to these organometallics,
alkyltins have been underemployed in comparison with
the large number of publications dedicated to the Stille
coupling reaction. There are indeed very few works
stating the possibility of transferring alkyl groups, other
than methyl, from alkyltins.12 In the course of finding
nontoxic and easily removable tin reagents, we recently
reported the synthesis of new monoorganotins 2 and their
Stille cross-coupling with halides13 and triflates14 as
electrophiles. The general and easy preparation of the
monoorganotins15 by oxidative addition of the corre-
sponding alkyl halides to the stannylene 1,16 associated
with the great functional group tolerance and the neutral
Monoalkyltins activated by a fluoride source are shown to
be as reactive as their vinyl or aryl homologues in the Stille
coupling reaction, thus providing an easy entry into the
pallado-catalyzed formation of Csp3-Csp2 bonds. In addition
to this uncommon reactivity, this methodology holds several
advantages such as (i) a quantitative preparation of stable
and easy to handle alkyltin reagents 2, (ii) a simplified
coupling procedure without any phosphine added ligand
under neutral conditions, and (iii) a facile purification step
of the organic products from the inorganic nontoxic tin
byproducts.
(4) Dohle, W.; Lindsay, D. M.; Knochel, P. Org. Lett. 2001, 3, 2871-
2873.
Cross-coupling reactions represent an extremely ver-
satile tool in organic synthesis for the C-C bond forma-
tion. In the past two decades most of the efforts have been
focused on the Csp2-Csp2 bond formation1 with applica-
tions ranging from organic materials to the total synthe-
ses of complex natural molecules. Recent advances in the
field of Csp3-hybridized coupling reactions are actually
emerging, the alkyl moiety being either on the substrate
or the organometallic partner.2 Among the variety of
transition metals used for this purpose, such as nickel,3
copper,4 or iron,5 palladium remains undoubtedly the
catalyst of choice as it offers the best balance in terms of
(5) Nagano, T.; Hayashi, T. Org. Lett. 2004, 6, 1297-1299.
(6) For Suzuki cross-coupling see: (a) Netherton, M. R.; Fu, G. C.
Angew. Chem., Int. Ed. 2002, 41, 3910-3912. (b) Kirchhoff, J. H.; Dai,
C.; Fu, G. C. Angew. Chem., Int. Ed. 2002, 41, 1945-1947. (c)
Netherton, M. R.; Dai, C.; Neuschu¨tz, K.; Fu, G. C. J. Am. Chem. Soc.
2001, 123, 10099-10100. (d) Ishiyama, T.; Abe, S.; Miyaura, N.;
Suzuki, A. Chem. Lett. 1992, 691-694. For Negishi cross-coupling: (e)
Zhou, J.; Fu, G. C. J. Am. Chem. Soc. 2003, 125, 12 527-12 530. For
Kumada cross-coupling: (f) Frisch, A. C.; Shaikh, N.; Zapf, A.; Beller,
M. Angew. Chem., Int. Ed. 2002, 41, 4056-4059. With organozirconi-
ums: (g) Wiskur, S. L.; Korte, A.; Fu, G. C. J. Am. Chem. Soc. 2004,
126, 82-83.
(7) (a) Hills, I. D.; Netherton, M. R.; Fu, G. C. Angew. Chem., Int.
Ed. 2003, 42, 5749-5752. For Stille cross-coupling: (b) Tang, H.;
Menzel, K.; Fu, G. C. Angew. Chem., Int. Ed. 2003, 42, 5079-5082. (c)
Littke, A. F.; Schwarz, L.; Fu, G. C. J. Am. Chem. Soc. 2002, 124,
6343-6348.
(8) (a) Kirchhofff, J. H.; Netherton, M. R.; Hills, I. D.; Fu, G. C. J.
Am. Chem. Soc. 2002, 124, 13662-13663. (b) Andrus, M. B.; Song, C.
Org. Lett. 2001, 3, 3761-3764.
(9) (a) Yus, M.; Gomis, J. Eur. J. Org. Chem. 2002, 1989-1995. (b)
Piber, M.; Jensen, A. E.; Rottla¨nder, M.; Knochel, P. Org. Lett. 1999,
1, 1323-1326. (c) Boudier, A.; Knochel, P. Tetrahedron Lett. 1999, 40,
687-690.
(10) (a) Gagneur, S.; Montchamp, J.-L.; Negishi, E. Organometallics
2000, 19, 2417-2419. (b) Messner, M.; Kozhushkov, S. I.; de Meijere,
A. Eur. J. Org. Chem. 2000, 1137-1155.
(11) Perez, I.; Perez Sestelo, J.; Sarandeses, L. A. J. Am. Chem. Soc.
2001, 123, 4155-4160.
(12) (a) See one example in ref 7c. (b) Ye, J.; Bhatt, R. K.; Falck, J.
R. J. Am. Chem. Soc. 1994, 116, 1. (c) Kosugi, M.; Sumiya, T.; Ogata,
T.; Sano, H.; Migita, T. Chem. Lett. 1984, 1225. (d) Peet, W. G.; Tam,
W. J. Chem. Soc., Chem. Commun. 1983, 853.
(13) (a) Fouquet, E.; Pereyre, M.; Rodriguez, A. L. J. Org. Chem.
1997, 62, 5242-5243. (b) Rodriguez, A. L.; Peron, G.; Duprat, C.;
Vallier, M.; Fouquet, E.; Fage`s, F. Tetrahedron Lett. 1998, 39, 1179-
1180.
(1) Diederich, F.; Stang, P. J. Metal-Catalyzed Cross-Coupling
Reactions; Wiley-VCH: Weinheim, Germany, 1998. Collman, J.-P.;
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Rev. 2000, 100, 3187-3204. Ca´rdenas, D. J. Angew. Chem., Int. Ed.
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J. Am. Chem. Soc. 2004, 126, 8100-8101. (b) Zhou, J.; Fu, G. C. J.
Am. Chem. Soc. 2003, 125, 14726-14727. (c) Jensen, A. E.; Knochel,
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A.; Stu¨demann, T.; Knochel, P. Angew. Chem., Int. Ed. 1995, 34, 2723-
2775. With organoborons: (g) Zhou, J.; Fu, G. C. J. Am. Chem. Soc.
2004, 126, 1340-1341. With Grignard’s reagents: (h) Terao, J.;
Watanabe, H.; Ikumi, A.; Kuniyasu, H.; Kambe, N. J. Am. Chem. Soc.
2002, 124, 4222-4223.
(14) Fouquet, E.; Rodriguez, A. L. Synlett 1998, 1323-1324.
(15) Fouquet, E.; Pereyre, M.; Rodriguez, A. L.; Roulet, T. Bull. Soc.
Chim. Fr. 1997, 134, 959-967.
10.1021/jo047907q CCC: $30.25 © 2005 American Chemical Society
Published on Web 02/08/2005
J. Org. Chem. 2005, 70, 1953-1956
1953

TABLE 1. n-Alkyl Transfer
SCHEME 1
conditions of the Stille reaction, prompted us to assess
the ability of monoalkyltins to achieve Csp2-Csp3 cou-
plings.17
TABLE 2. Branched-Alkyl Transfer
The coupling reaction is believed to proceed via an
activated hypervalent organostannate intermediate 4
prepared in situ by adding a fluorine source (Scheme 1).
Such nucleophilic activation is a well-established strategy
in organosilicon-mediated coupling reactions,18 and was,
more recently, applied to organoboron19 and organotin
chemistry.7b,13,14,20 It is noteworthy that the trifluorostan-
nate 5 is a nontoxic and easily removable inorganic
byproduct, which allows the coupling product 3 to get rid
of tin residues.
n-Alkyl transfer: We were first interested in trans-
ferring n-alkyl groups. Based on our earlier results, we
chose to perform the reaction in refluxing dioxane with
a 1.5-fold excess of the monoalkyltin partner. Palladium
tetrakis(triphenylphosphine) (2%) was elected as catalyst
and 3 equiv of TBAF was used as additive. These
conditions did yield the expected products in the range
68-91% (Table 1).
Thus, methyl-, butyl-, and decyltins 2a, 2b, and 2c
reaction (Table 1). The reaction is effective with iodides
(entries 2 and 3) as well as with bromides (entries 1, 4,
and 5) as the electrophilic substrates. Increasing the
length of the alkyl chain did not lower the reactivity of
the organotin. In terms of yields, these results have to
be compared with the transfer of the n-dodecyl group
from tetra(n-dodecyl)tin, which furnished the cross-
coupling product in only 25% yield.12d Importantly, the
substrate-substrate homocoupling was the sole side
reaction isolated and no trace of the â-hydride elimination
product (i.e. n-decene) was observed, which suggested a
quite fast reductive elimination step. Furthermore, the
method is tolerant of all substitutions (electron poor or
rich) on the aryl ring with only modest changes in yields.
Branched alkyl tranfer: We have also examined the
cross-coupling of branched alkytins 2e-j (Table 2). We
observed that the reaction was sensitive to the substitu-
tion of the alkyl chain. Indeed, while γ substitution had
no effect on the reaction rate and yield (entry 1), â
substitution had significant effects as demonstrated by
the slightly lengthened reaction time (36 h) and the
reduced yield (63%) (entry 2). Not surprisingly, R sub-
stitution forbade the reaction to proceed either with an
electron-donating group (entry 3) or with an electron-
withdrawing group (entry 4) as substituents. As a
consequence, we were unfortunately unable to transfer
secondary alkyl groups under these conditions. The
appeared to be efficient reagents for the Stille coupling
(16) (a) Harris, D. H.; Lappert, M. F. J. Chem. Soc., Chem. Commun.
1974, 895-896. (b) Schaeffer, C. D.; Zuckermann, J. J. J. Am. Chem.
Soc. 1974, 96, 7160-7162. Stannylene 1 is now a commercialy available
reagent.
(17) A range of monoalkyltins 2a-m were quantitatively prepared
by oxidative addition of the corresponding alkyl halides to the
stannylene 1. They were fully characterized by 119Sn, 1H, and 13C NMR
spectroscopy and cross-coupled without further purification.
(18) (a) Lee, J.-Y.; Fu, G. C. J. Am. Chem. Soc. 2003, 125, 5616-
5617. (b) Mowery, M. E.; DeShong, P. J. Org. Chem. 1999, 64, 3266-
3270. (c) Mowery, M. E.; DeShong, P. J. Org. Chem. 1999, 64, 1684-
1688. (d) Mowery, M. E.; DeShong, P. Org. Lett. 1999, 1, 2137-2140.
(e) Hatanaka, Y.; Hiyama, T. J. Org. Chem. 1989, 54, 270-276. (f)
Hatanaka, Y.; Hiyama, T. J. Org. Chem. 1988, 53, 920-923.
(19) (a) Navarre, L.; Darse, S.; Genet, J.-P. Eur. J. Org. Chem. 2004,
69-73. (b) Darse, S.; Genet, J.-P. Eur. J. Org. Chem. 2003, 4313-
4327. (c) Kolomeitsev, A. A.; Kadyrov, A. A.; Szczepkoxska-Sztoleman,
J.; Milewska, M.; Koroniak, H.; Bissky, G.; Barten, J. A.; Ro¨schentha-
ler, G.-V. Tetrahedron Lett. 2003, 44, 8273-8277. (d) Molander, G. A.;
Biolatto, B. J. Org. Chem. 2003, 68, 4302-4314.(e) Wright, S. W.;
Hageman, D. L.; McClure, L. D. J. Org. Chem. 1994, 59, 6095-6097.
(20) (a) Mee, S. P. H.; Lee, V.; Baldwin, J. E. Angew. Chem., Int.
Ed. 2004, 43, 1132-1136. (b) Menzel, K.; Fu, G. C. J. Am. Chem. Soc.
2003, 125, 3718-3719. (c) Tang, H.; Menzel, K.; Fu, G. C. Angew.
Chem., Int. Ed. 2003, 42, 5079-5082. (d) Martinez, A. G.; Barcina, J.
O.; Heras, M. R. C.; de Fresno Cerezo, A. Organometallics 2001, 20,
1020-1023. (e) Grasa, G. A.; Nolan, S. P. Org. Lett. 2001, 3, 119-122.
Martinez, A. G.; Barcina, J. O.; Heras, M. R. C.; de Fresno Cerezo, A.
Org. Lett. 2000, 2, 1377-1378. (f) Fugami, K.; Ohnuma, S.-Y.;
Kameyama, M.; Saotome, T.; Kosugi, M. Synlett 1998, 63-64. (g)
Martinez, A. G.; Barcina, J. O.; de Fresno Cerezo, A.; Subramanian,
L. R. Synlett 1994, 1047-1048.
1954 J. Org. Chem., Vol. 70, No. 5, 2005

SCHEME 2
TABLE 3. Ligands Effect
(dibenzylideneacetone)dipalladium and 2 equiv of the
ligand for each Pd atom. Replacing triphenylphosphine
by less donating ligands such as triisopropyl phosphite
(entry 3) and triphenylarsine (entry 4) resulted in an
enhancement of the reaction rate and the ability to
proceed at lower temperature. The cross-coupling was
successfully extended to other types of substrates such
as a iodoalkyne (entry 6) and a iodoalkene (entry 7) to
yield the desired products in good yields (60% and 72%,
respectively). A large rate enhancement was also ob-
served with tri-2-furylphosphine22 recommended by V.
Farina as the ligand of choice for the Stille cross-coupling
(entry 5). Nevertheless, the best results were obtained
under the simplest “ligandless” conditions, i.e., by using
Pd2dba3 as the catalyst (entry 9). Originally, even C20-
alkyltin 2d was efficiently cross-coupled with iodobenzene
yielding the corresponding aromatic compound 3m in
82% yield (entry 10).
Perfluoroalkyl transfer: The scope of our methodol-
ogy was investigated with the synthesis of perfluoroalky-
lated aryl compounds. Indeed, perfluoroalkylated deriva-
tives have attracted great interest in recent years not
only in the field of catalysisswith the concept of Fluorous
Biphasic Catalysis23sbut also in the field of combinatorial
organic synthesis.24 Nevertheless, only a few approaches
have been developed for the introduction of an ethylene
or a propylene spacer between the aromatic ring and the
perfluoroalkyl unit, whenever this spacer was proved to
be necessary to reduce the strong electron-withdrawing
effect of the perfluoroalkyl tail.23d Most frequently, cross-
coupling methodology involves the Heck25 reaction of
perfluoroalkenes with the subsequent hydrogenation of
the perfluoroalkenyl-substituted aromatic compounds. To
the best of our knowledge, only one Stille coupling
reaction has been described to introduce perfluoroalkyl
substituents on an aromatic ring.26
benzyltin reagent 2i was cross-coupled with 4-meth-
ylphenyl iodide and provided the desired product 3h
(entry 5) in comparable yield with that obtained with the
â-substituted alkyltin. Moreover, the reaction allowed the
transfer of a more sensible alkyl group (entry 6), furnish-
ing the cross-coupled product 3i in a non-optimized 52%
yield, without opening the methylenecyclopropyl unit.
Finally, the process showed promise for cyclization
reactions by using distannylated reagents (Scheme 2).
Thus, intermolecular cross-coupling of the organotin 2k
followed by an intramolecular one occurred to give the
eight-membered cyclized product 3j in a 38% yield. A
simple dilution of the reaction mixture by a factor of 2
resulted in an improved yield up to 48%.
Ligand effects: These promising results led us to
turn our attention to the optimization of the catalytic
system (Table 3). The choice of the catalyst generally has
a substantial impact on the course of the reaction. The
use of Pd(PPh3)2Cl2 in place of Pd(PPh3)4 allowed the
reaction to be done with a Pd:PPh3 ratio of 1:2, which is
believed to be the optimal one for the reaction to
proceed.21 We observed a significant acceleration (entry
2 versus entry 1); however, under these conditions, the
quantity of biphenyl that arose from the competitive
homocoupling of the halide was isolated in 18% yield. To
find the most effective catalyst, we surveyed an array of
ligands of different donating effect, as the nature of the
ligand can exert as well a dramatic influence on the rate
of cross-coupling reactions. The catalyst was then formed
in situ by introducing the weakly coordinated tris-
We first studied the cross-couplings of perfluoroethyltin
2l and perfluoropropyltin 3m by applying our optimized
conditions, i.e., in refluxing dioxane with a 1.7-fold excess
(22) (a) Farina, V.; Krishnan, B. J. Am. Chem. Soc. 1991, 113, 9585-
9595. (b) Andersen, N. G.; Keay, B. A. Chem. Rev. 2001, 101, 997-
1030 and references cited herein.
(23) For reviews see: (a) Pozzi, G.; Shepperson, I. Coord. Chem. Rev.
2003, 242, 115-124. (b) Wolf, E.; van Koten, G.; Deelman, B.-J. Chem.
Soc. Rev. 1999, 28, 37-41. (c) Fish, R. H. Chem. Eur. J. 1999, 5, 1677-
1679. (d) Hope, E. G.; Stuart, A. M. J. Fluorine Chem. 1999, 100, 75-
83. (e) Horvath, I. T. Acc. Chem. Res. 1998, 31, 641-650. (f) Cornils,
B. Angew. Chem., Int. Ed. Engl. 1997, 36, 2057-2059. (g) Gladysz, J.
A. Science 1994, 266, 55-56. (h) Horvath, I. T.; Rabai, J. Science 1994,
266, 72-75.
(24) (a) Wipf, P. Tetrahedron Lett. 1999, 40, 5139-5142. (b) Wipf,
P.; Reeves, J. T. Tetrahedron Lett. 1999, 40, 4649-4652. (c) Studer,
A.; Jeger, P.; Wipf, P.; Curran, D. P. J. Org. Chem. 1997, 62, 2917-
2924.
(25) (a) Wende, M.; Seidel, F.; Gladysz, J. A. J. Fluorine Chem. 2003,
124, 45-54. (b) Chen, W.; Xu, L.; Xiao, J. Tetrahedron Lett. 2001, 42,
4275-4278. (c) Darses, S.; Pucheault, M.; Genet, J.-P. Eur. J. Org.
Chem. 2001, 1121-1128. (d) Chen, W.; Xu, L.; Xiao, J. Org. Lett. 2000,
2, 2675-2677.
(26) Shimizu, R.; Fuchikami, T. Tetrahedron Lett. 1996, 37, 8405-
8408.
(21) Farina, V.; Kupadia, S.; Krishnan, B.; Wang, C.; Liebeskind,
L. S. J. Org. Chem. 1994, 59, 5905-5911.
J. Org. Chem, Vol. 70, No. 5, 2005 1955

TABLE 4. Pefluoroalkyl Transfer
a suspension of tinchloride(II) (10 g, 1 equiv) in anhydrous Et2O
(50 mL). The resulting reaction mixture was stirred at room
temperature for an additional 3 h. The solution was transferred
to a flask where the solvents were removed in vacuo to give an
orange oil that was distillated under reduced pressure (0.1
mmHg, 110 °C) to furnish bis(N,N-bistrimethylsilylamino)-
stannylene 1 in 89% yield (20.6 g).
General Procedure for the Preparation of Monoalkyltin
Compounds 2a-m. In a typical procedure, alkyl halide (1
equiv) was added to a solution of bis(N,N-bistrimethylsilylamino)
stannylene 1 (1 g) in anhydrous THF (10 mL) under an argon
atmosphere at room temperature. The reaction mixture was
stirred at room temperature until the reaction mixture turned
pale yellow. The solution was then concentrated in vacuo to yield
quantitatively the monoalkyltin 2a-m.
alkyl
time,
h
yield,
%
entry tin ArX solvent (°C)
product
1
2
3
2l
2m PhI dioxane (101) 1.75 Ph(CH2)3C8F17 (3o)
2m PhI THF (65) 12 Ph(CH2)3C8F17 (3o)
PhI dioxane (101) 1.75 Ph(CH2)2C8F17 (3n)
62
63
89
of the organotin, 3 equiv of TBAF as additive and 2% of
Pd2dba3 as catalyst. As shown in Table 4, the desired
products 3n and 3o were obtained in 62% and 63% yields,
respectively, within only 1 h 45 min (entries 1 and 2).
This difference in terms of reactivity between perfluoro-
alkyltin and simple alkyltin reagents is presumably
related to a faster reductive elimination step in the Stille
catalytic cycle. This led us to perform the reaction at
lower temperature in view of decreasing some substrate-
substrate homocoupling process. Thus, the cross-coupled
product 3o was isolated in 89% yield by carrying out the
reaction in refluxing THF (entry 3). This result offered
us the possibility of conceiving a one-pot procedure.
In conclusion, we have described the first ligandless-
palladium based method for transferring alkyl groups via
a cross-coupling reaction of aryl halides with original
monoalkyltin reagents. These compounds are easily and
quantitatively available through direct oxidative addition
of the corresponding halides with a low-valent tin species.
Moreover, these reagents met with the criteria of reduced
toxicity and easiness of purification, thus solving the
major drawbacks of the Stille cross-coupling. Indeed all
the organic products were free of organotin contamina-
tion as the trifluorostannate byproduct was easily re-
moved by a simple filtration. This methodology was
successfully applied to the synthesis of perfluoroalkylated
aromatic compounds. Further extensions are currently
underway in our laboratory.
General Procedure for the Stille Cross-Coupling. A
solution of TBAF (5.9 mL, 3 equiv, 1 M in THF) was added in
situ, at room temperature, to the monoorganotin reagents 2a-m
(1.85 mmol) prepared following the above procedure.. The
reaction mixture was concentrated in vacuo before adding the
anhydrous solvent (THF or dioxane, 8 mL), the catalyst (1% or
2%), and the halide (1.23 mmol, 0.67 equiv). The reaction
mixture was heated until the complete consumption of the halide
before cooling at room temperature. Removal of the solvent in
vacuo yielded an oily residue, which was subjected to chroma-
tography on silica gel (eluent: petroleum ether) to furnish the
cross-coupled product 3a-o.
Selected Data for Monoorganotin 2j and 2k: Bromobis-
(N,N-bistrimethylsilylamino)(3-(3-methyl-2-methylency-
clopropyl)propyl)tin 2j. Solvent: THF. Temperature: room
temperature. Reaction time: 2 h. Quantitatively prepared
following the general procedure. 119Sn NMR (74.6 MHz, CDCl3)
δ -57.2; 1H NMR (250 MHz, CDCl3) δ 5.30-5.28 (m, 2H), 1.72-
1.31 (m, 6H), 1.09-0.81 (m, 5H), 0.23 (s, 36H); 13C NMR (62.9
MHz, CDCl3) δ 143.3, 102.3, 36.2 (3JSn-C ) 72 Hz), 30.5 (1JSn-C
) 607 Hz), 25.7, 22.9, 17.5, 17.1, 5.8 (12C).
1,6-Bis[bromobis(N,N-bistrimethylsilylamino)stannyl]-
hexane 2k. Solvent: THF. Temperature: room temperature.
Reaction time: 3 h. Quantitatively prepared following the
1
general procedure. 119Sn NMR (74.6 MHz, CDCl3) δ -58.8; H
NMR (250 MHz, CDCl3) δ 1.83-1.35 (m, 12H), 0.22 (s, 72H).
13C NMR (62.9 MHz, CDCl3) δ 32.8 (2C, 3JSn-C ) 139 Hz), 30.7
1
(2C, JSn-C ) 622 Hz), 25.7 (2JSn-C ) 36 Hz), 5.7 (24C).
Selected Data for Coupling Products 3i and 3j: 1-Phen-
yl-3-(3-methyl-2-methylencyclopropyl)propane 3i. Solvent:
dioxane. Reaction time: 8 h. Temperature: 101 °C. Catalyst: Pd-
(PPh3)4 1%. Yield: 52%. 1H NMR (250 MHz, CDCl3) δ 7.38-7.21
(m, 5H), 5.60-5.58 (m, 2H), 2.68 (br t, J ) 7.6 Hz, 2H), 1.87-
1.29 (m, 4H), 1.20-0.94 (m, 5H); 13C NMR (62.9 MHz, CDCl3) δ
144.0, 142.7, 128.5 (2C), 128.4 (2C), 125.7, 101.8, 35.7, 32.4, 31.5,
23.6, 17.6, 17.1; MS (EI) m/z (rel intensity) 186 (M+, 6), 171 (20),
157 (27), 143 (17), 129 (43), 117 (56), 104 (32), 91 (100); HRMS
(EI) calcd for C14H18 186.1409, found 186.1412.
Bicyclododec[6.4.0]-1,9,11-triene 3j. Solvent: dioxane. Re-
action time: 15 h. Temperature: 101 °C. Catalyst: Pd(PPh3)4 1%.
Yield: 48%. 1H NMR (250 MHz, CDCl3) δ 7.19-7.03 (m, 4H),
2.85-2.73 (m, 4H), 1.78-1.61 (m, 4H), 1.45-1.33 (m, 4H); 13C
NMR (62.9 MHz, CDCl3) δ 141.3 (2C), 129.0 (2C), 126.2 (2C),
32.34 (2C), 32.29 (2C), 25.9 (2C); MS (EI) m/z (rel intensity) 160
(M+, 100), 131 (54), 117 (76), 104 (93), 91 (45); HRMS (EI) calcd
for C12H16 160.1252, found 160.1255.
Experimental Section
All reactions were carried out under an argon atmosphere in
flame-dried glassware. THF and dioxane were distilled under
argon from sodium/benzophenone. Commercially available ma-
terials were used without further purification. Anhydrous tin
chloride was stored under argon before used. The Bu4NF used
in the coupling reactions is the commercially available 1 M
solution. Reactions were monitored by gas chromatography (GC)
analysis of worked up reaction aliquots. Analytical thin-layer
chromatography (TLC) was performed using silica gel plates
(0.25 mm). Column chromatography was performed with 40-
63 µm silica gel. NMR spectra were recorded at ambient
temperature in CDCl3, on a 250 or 300 MHz NMR spectrometer
1
for H and 13C and a 200 MHz spectrometer for 119Sn.
Bis(N,N-bistrimethylsilylamino)stannylene 1. n-butyl-
lithium (41.3 mL of a 2.5 M hexane solution) was added dropwise
to a precooled (-78°C, acetone/dry ice) solution of freshly
distilled hexamethyldisilazane (21.8 mL, 1 equiv) in anhydrous
Et2O (50 mL) and THF (30 mL). The resulting mixture was
allowed to reach room temperature and stirred over a period of
1 h. The resulting lithium amidure was then added dropwise to
Supporting Information Available: Experimental pro-
cedures and NMR spectroscopic data including 1H and 13C for
compounds 1, 2a-m, and 3a-o as well as 119Sn for compounds
2a-m. This material is available free of charge via the
Internet at http://pubs.acs.org.
JO047907Q
1956 J. Org. Chem., Vol. 70, No. 5, 2005