A Novel Stereospecific Route to (E)- And (Z)-(2-Substituted-1,2-difluoroethenyl)stannanes

Article abstract of DOI:10.1021/jo9618785

In the presence of 1.2-1.5 equiv of potassium fluoride, a variety of (E)- and (Z)-(2-substituted-1,2-difluoroethenyl)silanes reacted with tributyltin chloride in DMF at room temperature to 80 °C to afford the corresponding stannanes in good yields with overall retention of configuration. These stannanes are useful intermediates for the introduction of the (E)- and (Z)-1,2-difluoroethylene unit into organic molecules. Under similar reaction conditions, only catalytic potassium fluoride (5-10%) was needed for these conversions when tributyltin chloride was replaced by tributyltin oxide. The mechanism and scope of this transformation is discussed.

Full text of DOI:10.1021/jo9618785

1064
J . Org. Chem. 1997, 62, 1064-1071
A Novel Ster eosp ecific Rou te to (E)- a n d
(Z)-(2-Su bstitu ted -1,2-d iflu or oeth en yl)sta n n a n es
Ling Xue, Long Lu, Scot D. Pedersen, Qibo Liu, Robert M. Narske, and Donald J . Burton*
Department of Chemistry, University of Iowa, Iowa City, Iowa 52242
Received October 4, 1996X
In the presence of 1.2-1.5 equiv of potassium fluoride, a variety of (E)- and (Z)-(2-substituted-1,2-
difluoroethenyl)silanes reacted with tributyltin chloride in DMF at room temperature to 80 °C to
afford the corresponding stannanes in good yields with overall retention of configuration. These
stannanes are useful intermediates for the introduction of the (E)- and (Z)-1,2-difluoroethylene
unit into organic molecules. Under similar reaction conditions, only catalytic potassium fluoride
(5-10%) was needed for these conversions when tributyltin chloride was replaced by tributyltin
oxide. The mechanism and scope of this transformation is discussed.
In tr od u ction
been reported by McCarthy.10 Recently, ethyl 3-(tribu-
tylstannyl)-2-methoxyacrylate was prepared from ethyl
trifluoropyruvate in several steps and used in the Stille
reaction for the synthesis of â-fluoro-R-keto acid deriva-
tives.11 In a recent communication,12 we have described
a novel, general, and convenient method for the prepara-
tion of a variety of fluorinated alkenylstannanes from the
corresponding alkenylsilanes. Here we wish to discuss
our detailed results including the scope, mechanism, and
a new improved modification of this transformation.
Introduction of fluorine into an organic molecule often
leads to dramatic changes in biological activities due to
the unique properties of fluorine, and fluorine-containing
compounds have been utilized in pharmaceuticals, agro-
chemicals, and other bioactive products.1-3 The role of
fluorine-containing organometallics in the preparation of
fluorinated organic molecules has been well reviewed.4
However, fluorine-containing organostannanes have re-
ceived little attention in part due to the limited meth-
odology in the preparation of fluorine-containing orga-
nostannanes. Since non-fluorinated alkenylstannanes
have been widely utilized in the formation of carbon-
carbon bonds via palladium-catalyzed cross-coupling with
organic halides and sulfonates (Stille reaction),5 fluorine-
containing alkenylstannanes would be particularly in-
valuable synthetic building blocks for incorporation of
fluorine into organic molecules. (Trifluorovinyl)stan-
nanes (CF2dCFSnR3) have been prepared from the
corresponding (trifluorovinyl)magnesium6 or (trifluorovi-
nyl)lithium7 reagents and trialkylstannyl halides and
have been successfully employed in the Stille reaction.8,9
The stereospecific preparation of (E)- and (Z)-(R-fluorovi-
nyl)stannanes via the radical reaction of the correspond-
ing R-fluorovinyl sulfones with tributyltin hydride has
Resu lts a n d Discu ssion
P r ep a r a tion of a Va r iety of (E)- a n d (Z)-(2-Su b-
stitu ted -1,2-d iflu or oeth en yl)sila n es. The methodol-
ogy for preparation of (E)- and (Z)-(2-substituted-1,2-
difluoroethenyl)silanes, R′CFdCFSiR3 (where R′ ) alkyl,
aryl, H, I, etc.), has been well established (Scheme 1).13-18
The key intermediate, (trifluorovinyl)triethylsilane (CF2d
CFSiEt3), was prepared utilizing MeLi (ether solution),
bromotrifluoroethylene, and chlorotriethylsilane in ether
13
or n-BuLi (hexane solution), chlorotrifluoroethylene,
and chlorotriethylsilane in THF.14 Treatment of CF2d
CFSiEt3 with LiAlH4 in tetrahydrofuran resulted in the
(Z)-(1,2-difluorovinyl)triethylsilane (trans-HCFdCFSiEt3)
as the predominant isomer (Z:E ) 95:5 by 19F NMR
analysis),15,16 which underwent isomerization easily with
ultraviolet light (254 nm) and catalytic phenyl disulfide
to afford the corresponding (E) isomer (Z:E ) 5:95) in
X Abstract published in Advance ACS Abstracts, February 1, 1997.
(1) (a) Biochemical Aspects of Fluorine Chemistry; Filler, R., Koba-
yashi, Y., Eds.; Elsevier Biomedical Press and Kodansha LTD: 1982.
(b) Organofluorine Compounds in Medicinal Chemistry and Biomedical
Applications; Filler, R., Kobayashi, Y., Yagupolskii, L. M., Eds.,
Elsevier Science Publishers B.V.: Amsterdam, 1993.
(2) Welch, J . T. Tetrahedron 1987, 43, 3123.
(10) (a) McCarthy, J . R.; Matthews, D. P.; Stemerick, D. M.; Huber,
E. W.; Bey, P.; Lipper, B. J .; Snyder, R. D.; Sunkara, P. S. J . Am. Chem.
Soc. 1991, 113, 7439. (b) Matthews, D. P.; Millers, S. C.; J arvi, E. T.;
Sabol, J . S.; McCarthy, J . R. Tetrahedron Lett. 1993, 34, 3057. (c)
Moore, W. R.; Schatzman, G. L.; J arvi, E. T.; Gross, R. S.; McCarthy,
J . R. J . Am. Chem. Soc. 1992, 114, 360. (d) Gross, R. S.; Mehdi, S.;
McCarthy, J . R. Tetrahedron Lett. 1993, 34, 7197.
(11) Shi, G. Q.; Cao, Z. Y.; Zhang, X. B. J . Org. Chem. 1995, 60,
6608.
(12) Xue, L.; Lu, L.; Pederson, S.; Liu, Q.; Narske, R.; Burton, D. J .
Tetrahedron Lett. 1996, 37, 1921.
(13) Fontana, S. A.; Davis, C. R.; He, Y. B.; Burton, D. J . Tetrahedron
1996, 52, 37 and references cited therein.
(3) Banks, R. E., Smart, B. E., Tatlow, J . C., Eds.; Organofluorine
Chemistry, Principles and Chemical Applications; Plenum Press: New
York, 1994.
(4) (a) Burton, D. J .; Yang, Z. Y. Tetrahedron 1992, 48, 189. (b)
Burton, D. J .; Yang, Z. Y.; Morken, P. A. Tetrahedron 1994, 50, 2993.
(5) (a) Pereyre, M.; Quintard, J .-P.; Rehm, A. Tin in Organic
Synthesis; Butterworth: London, 1987. (b) Stille, J . K. Angew. Chem.,
Int. Ed. Engl. 1986, 25, 508. (c) Mitchell, T. N. Synthesis 1992, 803.
(6) (a) Kaesz, H. D.; Stafford, S. L.; Stone, F. G. A. J . Am. Chem.
Soc. 1960, 82, 6232. (b) Seyferth, D; Brandle, K. A.; Raab, G. Angew.
Chem. 1960, 72, 77. (c) Seyferth, D.; Raab, G; Brandle, K. A. J . Fluorine
Chem. 1982, 20, 699.
(7) Seyferth, D.; Welch, D. E.; Raab, G. J . Am. Chem. Soc. 1962,
84, 4266.
(14) Hiyama, T.; Nishide, K.; Obayashi, M. Chem. Lett. 1984, 10,
1765.
(15) Fujita, M.; Obayashi, M.; Hiyama, T. Tetrahedron 1988, 44,
4135.
(16) Martinet, P.; Sauvetre, R.; Normant, J . F. J . Organomet. Chem.
1989, 367, 1.
(17) Seyferth, D.; Wada, T., Inorg. Chem. 1962, 1, 78.
(18) (a) Martin, S.; Sauvetre, R.; Normant, J . F. Tetrahedron Lett.
1983, 24, 5615. (b) Martin, S.; Sauvetre, R.; Normant, J . F. J .
Organomet. Chem. 1984, 264, 155.
(8) (a) Sorokina, R. S.; Rybakova, L. F.; Kalinovskii, I. Q.; Cher-
noplekova, V. A.; Beletskaya, I. P. J . Org. Chem. USSR (Engl. Transl.)
1982, 18, 2180. Zh. Org. Khim. 1982, 18, 2458. (b) Sorokina, R. S.;
Rybakova, L. F.; Kalinovskii, I. Q.; Beletskaya, I. P. Bull. Acad. Sci.
USSR Div. Chem. Sci. (Engl. Transl.) 1985, 1506. Izv. Akad. Nauk
SSSR, Ser. Khim. 1985, 1647.
(9) Farina, V.; Baker, S. R.; Benigni, D. A.; Hauck, S. I.; Sapina, C.,
J r. J . Org. Chem. 1990, 55, 5833.
S0022-3263(96)01878-6 CCC: $14.00 © 1997 American Chemical Society

(E)- and (Z)-(2-Substituted-1,2-difluoroethenyl)stannanes
Sch em e 1
J . Org. Chem., Vol. 62, No. 4, 1997 1065
Sch em e 2
Sch em e 3
difluorovinyl)silane and (trifluorovinyl)zinc iodide19 via
a palladium(0)-catalyzed cross-coupling reaction in THF
(Scheme 3).
P r ep a r a tion of (E)- a n d (Z)-(2-Su bstitu ted -1,2-
diflu or oeth en yl)stan n an es. Palladium-catalyzed cross-
coupling reactions of vinyltrimethylsilane and alkenylflu-
orosilanes with aryl and vinyl halides in the presence of
fluoride for the formation of the carbon-carbon bond has
been reported by Hiyama et al.20 But the low reactivity
of alkenyltrimethylsilane and the lack of availability of
alkenylfluorosilanes limited further applications of this
reaction. Recently, new efforts have been made through
the conversion of the vinylsilanes to the corresponding
vinylboronates followed by the Suzuki-Miyaura cross-
coupling reaction without isolation of the intermediate.21
Our recent interest in the development of (E)- and (Z)-
1,2-difluoroethenyl synthon13 prompted our attention to
the preparation of (E)- and (Z)-(2-substituted-1,2-difluo-
roethenyl)stannanes, R′CFdCFSnR3 (where R′ ) alkyl,
aryl, H, I, etc.) for potential utilization in the Stille cross-
coupling reaction.5 As noted above (trifluorovinyl)stan-
nanes (CF2dCFSnR3) have been prepared from the corre-
sponding (trifluorovinyl)magnesium6 or (trifluorovinyl)-
lithium7 reagents and trialkyltin chlorides. In contrast
to analogous fluorinated vinylsilane, reaction of CF2d
CFSnR3 with R′Li (R′ ) alkyl, aryl) only gave the
high yield.13 (E)-(1,2-Difluoro-2-iodovinyl)triethylsilane
(trans-ICFdCFSiEt3) was readily prepared via low tem-
perature iodination of the pregenerated trans-vinyl-
lithium intermediate.16 In contrast, the (Z) isomer (cis-
ICFdCFSiEt3) was obtained from the corresponding vinyl
stannane due to the instability of cis-vinyllithium inter-
mediate.13
(Z)-(2-Alkyl- or (2-aryl-1,2-difluoroethenyl)silanes (trans)
were prepared through an addition-elimination reaction
of (trifluorovinyl)silane with alkyl or aryl lithium re-
agents via a modified literature procedure (Scheme 2).17,18
Chlorotrimethylsilane was used in situ to trap the un-
stable CF2dCFLi. It should be noted that compound 12
was obtained in better yield (75%) in ethyl ether than
THF (41%), and ether could only be used for preparation
of the volatile compound 8 (bp 95 °C).
(Z)-1-(Triethylsilyl)-1,2,3,4,4-pentafluoro-1,3-butadi-
ene (trans-CF2dCFCFdCFSiEt3, 13) and (Z)-1-(dimeth-
ylphenylsilyl)-1,2,3,4,4-pentafluoro-1,3-butadiene (trans-
CF2dCFCFdCFSiMe2Ph, 14) can be easily synthesized
in high yields from the corresponding (E)-(2-iodo-1,2-
(19) Heinze, P. L.; Burton, D. J . J . Org. Chem. 1988, 53, 2714.
(20) Hiyama, T.; Hatanaka, Y. Pure Appl. Chem. 1994, 66, 1471 and
references cited therein.
(21) Farinola, G. M.; Fiandanese, V.; Mazzone, L.; Naso, F. J . Chem.
Soc., Chem. Commun. 1995, 2523.

1066 J . Org. Chem., Vol. 62, No. 4, 1997
Ta ble 1. Rea ction of Vin ylsila n es w ith Tr ibu tyltin Ch lor id e in th e P r esen ce of P ota ssiu m F lu or id e
Xue et al.
Entry
R′CFdCFSiR3
CF2dCFSiEt3, 1
(Z)-HCFdCFSiEt3, 2
(E)-HCFdCFSiEt3, 3
(E)-ICFdCFSiEt3, 4
(Z)-ICFdCFSiEt3, 5
(Z)-n-BuCFdCFSiEt3, 6
(Z)-tert-BuCFdCFSiEt3, 7
(Z)-MeCFdCFSiMe3, 8
(Z)-n-BuCFdCFSiMe3, 9
(Z)-n-BuCFdCFSiMe3, 9
(Z)-sec-BuCFdCFSiMe3, 10
(Z)-tert-BuCFdCFSiMe3, 11
(Z)-PhCFdCFSiMe3, 12
(Z)-CF2dCFCFdCFSiEt3, 13
(Z)-CF2dCFCFdCFSiMe2Ph, 14
reaction conditions
products
yield (%)a
1
2b
3c
4
rt, overnight
70 °C, overnight
70 °C, overnight
rt, overnight
rt, overnight
80 °C, 24 h
80 °C, 24 h
80 °C, 10 h
rt, overnight
80 °C, 10 h
80 °C, 10 h
80 °C, 10 h
rt, 12 h
1a
92
80
74
83
82
72
71
74
NR
78
87
79
70
82
69
2a b
3a c
4a
5d
6
5a d
6a
7
8
9
10
11
12
13
14
15
7a
8a
-
6a
10a
7a
12a
13a
13a
rt, 24 h
rt, 24 h
a
b
c
Isolated yields based on vinylsilanes. Z:E ) 95:5; E:Z ) 95:5; dZ:E ) 95:5.
Sch em e 4
Sch em e 6
edge, this is the first report of the stereospecific conver-
sion of a vinylsilane to the corresponding vinylstannane,
although recently Buchwald reported the conversion of
alkynyltrimethylsilanes as well as allyl- and benzyltri-
methylsilane to the corresponding stannanes utilizing
TBAF and tributyltin oxide.24 Also Olah recently syn-
thesized (trifluoromethyl)tributylstannane from the cor-
responding (trifluoromethyl)trimethylsilane via Buch-
wald’s method (Scheme 6).25
Sch em e 5
Table 1 summarizes our detailed results. In all cases,
the configuration of the double bond was unchanged.
When R was iodine, phenyl, fluorine, or trifluorovinyl,
the conversion occurred readily at room temperature
(entries 1, 4, 5, 13-15). The conversion proceeded slowly
at room temperature when R was hydrogen, and no
reaction was observed at room temperature when R was
an alkyl group. However, at 70-80 °C the conversion of
the vinylsilane to the vinyl stannane occurred readily
regardless of the nature of the R group. The triethylsilyl
derivatives were less reactive than the corresponding
trimethylsilyl derivatives, and longer reaction time was
needed (entries 6, 7), presumably due to more facile
attack by fluoride ion on the smaller trimethylsilyl group.
A possible reaction mechanism is described below. Fluo-
ride ion attacks the silyl group to generate the vinyl
carbanion and trialkylsilyl fluoride. The vinyl carbanion
reacted with tributyltin chloride to yield the desired
vinylstannane (Scheme 7). Therefore, theoretically at
least 1 equiv of potassium fluoride was needed for
complete conversion, and 1 equiv of trialkylsilyl fluoride
was formed as a major byproduct.
exchange product, (trifluorovinyl)lithium (CF2dCFLi)7,22
and none of the addition-elimination product. Similarly,
reduction of (trifluorovinyl)stannane with LiAlH4 yielded
only trifluoroethylene (CF2dCFH) rather than HCFd
CFSnR3.23 A mixture of (E)- and (Z)-HCFdCFSnMe3
(E:Z ) 3:1) was obtained in about 50% yield through the
radical reduction of (trifluorovinyl)trimethylstannane
with trimethyltin hydride (Scheme 4). Consequently, if
these stannanes were to be utilized in Stille coupling
processes it was necessary to develop a novel, convenient,
and stereospecific route to these (E)- and (Z)-(2-substi-
tuted-1,2-difluoroethenyl)stannanes.
Hiyama reported the fluoride ion-catalyzed generation
and carbonyl addition of trans-2-substituted-1,2-difluo-
roethenyl carbanions from the corresponding trans-(2-
substituted-1,2-difluoroethenyl)silanes (Scheme 5).15 In
place of aldehydes, tributyltin chloride, a well-known
good electrophile, was employed to react with trans-(2-
substituted-1,2-difluoroethenyl)silanes in DMF in the
presence of dry potassium fluoride (1.5-2.0 equiv) at
room temperature to 80 °C to stereospecifically afford the
corresponding stannanes in good yields. To our knowl-
Further studies indicated that when tributyltin chlo-
ride was replaced with bis(tributyltin) oxide (0.5 equiv),
only catalytic potassium fluoride (5-10%) was needed to
complete the conversion under similar reaction conditions
(24) Warner, B. P.; Buchwald, S. L. J . Org. Chem. 1994, 59, 5822.
(25) Prakash, G. K. S.; Yudin, A. K.; Deffieux, D.; Olah, G. A. Synlett
1996, 151.
(22) Seyferth, D.; Wada, T.; Raab, G. Tetrahedron Lett. 1960, 2, 20.
(23) Davis, C. R. University of Iowa, unpublished results.

(E)- and (Z)-(2-Substituted-1,2-difluoroethenyl)stannanes
J . Org. Chem., Vol. 62, No. 4, 1997 1067
Sch em e 7
Sch em e 9
Ta ble 2. Rea ction of Vin ylsila n es w ith Bis(tr ibu tyltin )
Oxid e in th e P r esen ce of Ca ta lytic P ota ssiu m F lu or id e
CHSnBu3) in 50% yield. Similarly, (Z)-(1-chloro-2-fluoro-
1-hexenyl)tributylstannane ((Z)-n-BuCFdCClSnBu3, 16a)
was obtained in 85% yield from the corresponding silane-
((Z)-n-BuCFdCClSiMe3, 16) (Scheme 9). However, no
conversion of silane to stannane was observed when a
vinylsilane without vinyl fluorine was employed, such as
CH2dCHSiMe3 or (E)-RFCHdCHSiMe3, presumably due
to the low polarity of the carbon-silicon bond when no
fluorine is present on the double bond.
reaction
conditions
yield
(%)a
entry
R′
Me, 8
products
1
2
3
4
5
80 °C, 10 h
80 °C, 10 h
80 °C, 10 h
80 °C, 10 h
80 °C, 10 h
8a
6a
10a
7a
12a
85
90
87
88
79
n-Bu, 9
sec-Bu, 10
tert-Bu, 11
Ph, 12
a
Isolated yields based on vinylsilanes.
Sch em e 8
In conclusion, we have described a novel, efficient, and
stereospecific method for the synthesis of a variety of (E)-
and (Z)-(2-substituted-1,2-difluoroethenyl)stannanes and
related fluorinated stannanes from the corresponding
silanes. These fluorinated alkenylstannanes are poten-
tially valuable synthons for the stereospecific introduc-
tion of the 1,2-difluoroethylene unit into organic mol-
ecules. The detailed results of the palladium-catalyzed
cross-coupling reaction (Stille reaction) of these stan-
nanes with aryl and vinyl halides will be described in
future reports.
Exp er im en ta l Section
Gen er a l. All boiling points are uncorrected. 19F NMR
(282.44 MHz), 1H NMR (300.17 MHz), and 13C NMR (75.48
MHz) spectra were recorded in CDCl3 solvent. All chemical
shifts are reported in parts per million downfield (positive) of
the standards. 19F NMR spectra are referenced against
internal CFCl3, and 1H NMR and 13C NMR spectra against
internal tetramethylsilane (TMS). FT-IR spectra were re-
corded as CCl4 solutions using a solution cell with a 0.1-cm
path length and absorbance frequencies reported in cm-1
.
GC-MS spectra were obtained at 70 eV in the electron-impact
mode. High resolution mass spectral determinations were
made at the University of Iowa High Resolution Mass Spec-
trometry Facility. GLPC analysis were performed on a 5%
OV-101 column with a thermal conductivity detector. Photo-
chemical reactions were carried out in a quartz Rotoflo tube
in a photoreactor equipped with 254 nm bulbs.
Ma ter ia ls. MeLi (1.4 M in ethyl ether), n-BuLi (2.5 M in
hexane), sec-BuLi (1.3 M in cyclohexane), tert-BuLi (1.7 M in
pentane), and PhLi (18 M in pentane/ethyl ether) were
obtained from Aldrich Chemical Co. Chlorotriethylsilane,
bromotrifluoroethylene, chlorotrifluoroethylene, 1,1-dichloro-
2,2-difluoroethylene, and 1,1-difluoroethylene were obtained
from PCR Specialty Chemicals. Tributyltin chloride, chlorot-
rimethylsilane, tributyltin oxide, lithium aluminum hydride,
and potassium fluoride were obtained from Aldrich Chemical
Co. without further purification. Potassium fluoride was dried
by refluxing with benzene prior to use. DMF was dried by
distillation from CaH2 and stored under nitrogen. (Trifluo-
rovinyl)triethylsilane (CF2dCFSiEt3, 1), (Z)-(1,2-difluorovinyl)-
triethylsilane (trans-HCFdCFSiEt3, 2), (E)-(1,2-difluorovinyl)-
triethylsilane (cis-HCFdCFSiEt3, 3), (E)-(1,2-difluoro-2-
iodovinyl)triethylsilane (trans-ICFdCFSiEt3, 4), (Z)-(1,2-di-
(Table 2). This modified procedure provided better yields,
probably due to minimizing the formation of the reduced
product (R′CFdCFH), which is usually formed in about
10% yield. It should be noted that this modified proce-
dure is best employed in the conversion of fluorinated
vinyltrimethylsilanes to the corresponding stannanes,
since in these cases the volatile trimethylsiloxane (Me3-
SiOSiMe3) was formed as the major byproduct, which can
be easily seperated from the product. The catalytic cycle
is shown below (Scheme 8).
Several other fluorinated vinylsilanes can also be
converted to the corresponding stannanes under the same
reaction conditions. 2,2-(Difluorovinyl)triethylsilane (15,
CF2dCHSiEt3) which was prepared from (2,2-difluorovi-
nyl)lithium reagent26 and chlorotriethylsilane reacted
with tributyltin chloride in the presence of KF at 80 °C
to afford the the corresponding stannane (15a , CF2d
(26) Sauvetre, R.; Normant, J . F. Tetrahedron Lett. 1981, 22, 957.

1068 J . Org. Chem., Vol. 62, No. 4, 1997
Xue et al.
fluoro-2-iodovinyl)triethylsilane (cis-ICFdCFSiEt3, 5) were
prepared according to the literature procedure.13
dimethyl-1-(trimethylsilyl)-1-butene in 75% yield, bp 75 °C/
100 mmHg (lit.18b 35 °C/10 mmHg). 1H NMR (CDCl3): 1.21(m,
3
9H), 0.18 (m, 9H) ppm. 19F NMR (CDCl3): -149.4 (d, J FF
)
P r ep a r a tion of (Z)-(1,2-Diflu or o-1-a lk en yl)tr ia lk ylsi-
la n es (tr a n s-R′CF dCF SiR3). P r ep a r a tion of (Z)-1,2-Di-
flu or o-1-(t r im et h ylsilyl)-1-h exen e (tr a n s-n -Bu CF dCF -
SiMe3, 9). A 1000 mL three-necked flask equipped with a low
temperature thermometer, a magnetic stir bar, a N2 tee, and
a dry ice/acetone condenser was charged with 150 mL of
tetrahydrofuran, 21.7 g (0.2 mol) of trimethylsilyl chloride, and
cooled to -85 °C with a pentane/liquid nitrogen bath. Then,
chlorotrifluoroethylene (25.6 g, 0.22 mol) was condensed into
the cooled solution. n-BuLi (88 mL, 2.5 M in hexane, 0.22 mol)
was slowly added over three hours via syringe. During
addition, the solution was maintained below -80 °C. After
the addition was completed, the solution was stirred at -78
°C for 2 h and then allowed to warm to room temperature over
3 h. Then the reaction mixture was recooled to -78 °C with
a dry ice/acetone bath, and n-BuLi (80 mL, 2.5 M in hexane,
0.2 mol) was added slowly into the mixture via syringe. After
the addition was completed, the reaction mixture was warmed
to room temperature and stirred overnight. Aqueous HCl
solution (0.1 N, 300 mL) was added slowly, and the reaction
mixture was extracted with ether (200 mL × 2). The combined
organic layers were washed with brine and dried over MgSO4.
After evaporation of ether, the residue was distilled under
reduced pressure to afford (Z)-1,2-difluoro-1-(trimethylsilyl)-
1-hexene (32.6 g) in 85% yield, bp 95 °C/100 mmHg. (lit.18b
50-52 °C/11 mmHg). 1H NMR (CDCl3): 2.40 (m, 2H), 1.50
125.2 Hz, 1F), -172.9 (d, 3J FF ) 125.2 Hz, 1F) ppm. 13C NMR
(CDCl3): 169.1 (dd, J ) 236.9, 34.5 Hz), 154.9 (dd, J ) 260.7,
87.0 Hz), 35.60 (dd, J ) 24.1, 2.7 Hz), 27.51 (dd, J ) 4.9, 3.9
Hz), -2.21 (dd, J ) 2.8, 2.4 Hz) ppm. GC-MS: 192 (M+, 9.29),
177 (M+ - CH3, 0.75). FTIR: 1728.05 (CdC) cm-1
.
P r ep a r a tion of (Z)-1,2-Diflu or o-1-(tr im eth ylsilyl)sty-
r en e (tr a n s-P h CF dCF SiMe3, 12). Similarly, (trifluorovi-
nyl)trimethylsilane, prepared in situ from bromotrifluoroeth-
ylene (81 g, 0.5 mol) and MeLi (360 mL, 1.4 M in Et2O, 0.5
mol) in ethyl ether, was reacted with PhLi (250 mL, 1.8 M in
pentane/ether, 0.45 mol) to give (Z)-1,2-difluoro-1-(trimethyl-
silyl)styrene (64.0 g) in 75% yield, bp 78-81 °C/1.0 mmHg
(lit.18b 50 °C/0.01 mmHg). 1H NMR (CDCl3): 7.30-7.70 (m,
5H, Ph), 0.30 (dd, 4J HF ) 1.3 Hz, 5J HF ) 0.8 Hz, 3 × CH3) ppm.
3
19F NMR (CDCl3): -152.9 (d, J FF ) -152.2 Hz, 1F), -164.6
(d, 3J FF ) 125.2 Hz ,1F) ppm. 13C NMR (CDCl3): 157.9 (dd, J
) 224.6 Hz, J ) 33.3 Hz), 156.7 (dd, J ) 271.0 Hz, J ) 82.4
Hz), 130.1 (dd, J ) 26.8 Hz, J ) 3.9 Hz), 129.0 (d, J ) 2.1 Hz),
128.7 (s), 128.4 (d, J ) 2.1 Hz), 127.2 (d, J ) 4.2 Hz), 125.7
(dd, J ) 9.8 Hz, J ) 7.6 Hz) ppm. GC-MS: 212 (M+, 20.36),
197 (M+ - CH3, 0.51), 77 (Ph+, 100). FTIR: 1640.25 (CdC)
cm-1
.
P r ep a r a tion of (Z)-1,2-Diflu or o-1-(tr ieth ylsilyl)-1-h ex-
en e (tr a n s-n -Bu CF dCF SiEt3, 6). A 250 mL three-necked
flask equipped with a low temperature thermometer, magnetic
stir bar, and N2 tee was charged with CF2dCFSiEt3 (19.6 g,
0.1 mol) and dry ether (100 mL) and cooled to -78 °C with
dry ice/acetone bath. n-BuLi (2.5 M in hexane, 48 mL, 0.12
mol) was added slowly via syringe. The reaction mixture was
stirred at -78 °C for 1 h and then warmed to room temper-
ature for 2 h. The reaction mixture was recooled with an ice-
water bath, and dilute HCl solution (0.1 N, 80 mL) was added
to decompose the excess lithium reagent. The organic layer
was separated, and the aqueous layer was extracted with ethyl
ether (30 mL × 2). The combined organic layers were washed
with saturated brine solution and dried over anhydrous
MgSO4. Evaporation of solvents on a rotary evaporator,
followed by distillation under vaccum, gave the addition-
elimination product (21.0 g, 90% yield), bp 73-77 °C/2 mmHg
(lit.17 53 °C/ 0.4 mmHg). GLPC 95.5%. 1H NMR (CDCl3): 2.40
(m, 2H), 1.51 (m, 2H), 1.36 (m, 2H), 0.97 (m, 12H), 0.72 (q,
6H) ppm. 19F NMR (CDCl3): -146.2 (dt, 3J FF ) 124.6 Hz, 3J HF
4
(m, 2H), 1.35 (m, 2H), 0.92 (t, 3H), 0.2 (q, J HF ) 0.7 Hz, 9H)
3
3
ppm. 19F NMR (CDCl3): -146.1 (dt, J FF ) 125.9 Hz, J HF
)
3
4
23.5 Hz, 1F), -174.3 (dt, J FF ) 125.9 Hz, J FH ) 6.4 Hz, 1F)
ppm. 13C NMR (CDCl3): 165.5 (dd, J ) 237.8 Hz, J ) 41.9
Hz), 155.5 (dd, J ) 254.5 Hz, J ) 74.4 Hz), 27.81 (dd, J ) 2.2
Hz, J ) 0.9 Hz), 26.36 (dd, J ) 25.3 Hz, J ) 1.5 Hz), 22.05 (s),
13.70 (s), -2.37 (s) ppm. GC-MS: 192 (M+, 6.69), 149 (M+
-
C3H7, 0.14). FTIR: 1675.21 (CdC) cm-1
.
P r ep a r a t ion of (Z)-1,2-Diflu or o-1-(t r im et h ylsilyl)-1-
p r op en e (tr a n s-MeCF dCF SiMe3, 8). Similarly, (trifluo-
rovinyl)trimethylsilane (CF2dCFSiMe3), prepared in situ from
bromotrifluoroethylene (72.5 g, 0.45 mol), MeLi (325 mL, 1.4
M in Et2O, 0.45 mol), and chlorotrimethylsilane (43.4 g, 0.4
mol) in ethyl ether was reacted with MeLi (300 mL, 1.4 M in
Et2O, 0.42 mol) followed by fractional distillation through a
25 cm long spinning band column to afford (Z)-1,2-difluoro-1-
(trimethylsilyl)-1-propene (37.1 g) in 62% yield, bp 95 °C. 1H
3
4
2
4
NMR (CDCl3): 2.00 (dd, J HF ) 17.6 Hz, J HF ) 6.2 Hz, 3H),
) 23.6 Hz, 1F), -173.8 (dt, J FF ) 124.6 Hz, J HF ) 6.4 Hz,
1F) ppm. 13C NMR (CDCl3): 166.5 (dd, J ) 238.1 Hz, J )
41.8 Hz), 154.2 (dd, J ) 255.5 Hz, J ) 76.0 Hz), 27.9 (dd, J )
2.5 Hz, J ) 1.2 Hz), 26.3 (dd, J ) 25.6 Hz, J ) 1.8 Hz), 22.0
(s), 13.7 (s), 7.1 (s), 2.5 (dd, J ) 2.2 Hz, J ) 2.1 Hz) ppm.
FTIR: 1672.9 (CdC) cm-1. GC-MS: 234 (M+, 5.69), 177 (M+
- Bu, 0.23), 119 (M+ - Et3Si, 1.10).
0.20 (s, 9H) ppm. 19F NMR (CDCl3): -138.3 (dq, 3J FF ) 126.5
3
3
4
Hz, J HF ) 17.6 Hz, 1F), -173.4 (dq, J FF ) 126.5 Hz, J HF
)
5.7 Hz ,1F) ppm. 13C NMR (CDCl3): 162.3 (dd, J ) 235.2 Hz,
J ) 43.0 Hz), 155.9 (dd, J ) 254.2 Hz, J ) 73.2 Hz), 12.75
(dd, J ) 27.2 Hz, J ) 2.4 Hz) ppm. GC-MS: 150 (M+), 135
(M+ - CH3). FTIR: 1683.90 (CdC) cm-1
.
P r ep a r a tion of (Z)-1,2-Diflu or o-3-m eth yl-1-(tr im eth -
ylsilyl)-1-p en ten e (tr a n s-sec-Bu CF dCF SiMe3, 10). Simi-
larly, (trifluorovinyl)trimethylsilane, prepared in situ from
chlorotrifluoroethylene (25.6 g, 0.22 mol), n-BuLi (88 mL, 2.5
M in hexane, 0.22 mol), and chlorotrimethylsilane (21.7 g, 0.2
mol) in THF, was reacted with sec-BuLi (170 mL, 1.3 M in
cyclohexane, 0.22 mol) to give 28.0 g of (Z)-1,2-difluoro-3-
methyl-1-(trimethylsilyl)-1-pentene in 73% yield, bp 85 °C/100
mmHg. (lit.18b 40 °C/11 mmHg). 1H NMR (CDCl3): 2.80 (m,
1H), 1.43 (m, 2H), 1.09 (d, J ) 7.9 Hz, 3H), 0.89 (t, J ) 8.0
Hz, 3H), 0.21 (m, 9H) ppm. 19F NMR (CDCl3): -159.4 (dd,
3J FF ) 125.9 Hz, 3J HF ) 33.1 Hz, 1F), -175.6 (dd, 3J FF ) 125.9
P r ep a r a tion of (Z)-1,2-Diflu or o-3,3-d im eth yl-1-(tr ieth -
ylsilyl)-1-bu ten e (tr a n s-ter t-Bu CFdCF SiEt3, 7). Similarly,
CF2dCFSiEt3 (9.8 g, 0.05 mol) reacted with tert-BuLi (1.7 M
in pentane, 35 mL, 0.06 mol) in 100 mL of dry ether to afford
the (Z)-1,2-difluoro-3,3-dimethyl-1-(triethylsilyl)-1-butene (10.7
g, 91% yield), bp 64-65 °C/2 mmHg, GLPC 98.7%. 1H NMR
4
5
(CDCl3): 1.21 (dd, J HF ) 2.0 Hz, J HF ) 1.9 Hz, 9H), 0.97 (t,
3J HH ) 7.9 Hz, 9H), 0.68 (q, 3J HH ) 7.9 Hz, 6H) ppm. 19F NMR
3
3
(CDCl3): -149.5 (d, J FF ) 124.0 Hz), -172.6 (d, J FF ) 124.0
Hz) ppm. 13C NMR (CDCl3): 170.0 (dd, J ) 236.8 Hz, J )
34.5 Hz), 153.6 (dd, J ) 260.9 Hz, J ) 88.5 Hz), 35.7 (dd, J )
24.1 Hz, J ) 2.5 Hz), 27.6 (dd, J ) 4.9 Hz, J ) 4.0 Hz), 7.1 (s),
2.6 (dd, J ) 2.5 Hz, J ) 2.4 Hz) ppm. FTIR: 1649.6 (CdC)
cm-1. GC-MS: 234 (M+, 3.22), 205 (M+ - C2H5, 0.16), 177 (M+
- Bu, 0.21). HRMS: Calcd for C12H24F2Si: 234.1615.
Found: 234.1611.
4
Hz, J HF ) 5.1 Hz, 1F) ppm. 13C NMR (CDCl3): 167.7 (dd, J
) 240.8, 40.3 Hz), 154.9 (dd, J ) 254.9, 75.7 Hz), 32.99 (dd, J
) 24.4, 1.2 Hz), 26.12 (d, J ) 2.4 Hz), 16.86 (d, J ) 1.5 Hz),
11.81 (s), -2.32 (m) ppm. GC-MS: 192 (M+, 16.99), 163 (M+
- C2H5, 1.02). FTIR: 1668.61 (CdC) cm-1
.
P r ep a r a tion of (2,2-Diflu or ovin yl)tr ieth ylsila n e (CF 2d
CHSiEt3, 15). A 250 mL three-necked flask equipped with a
low temperature thermometer, a magnetic stir bar, a N2 tee,
and a dry ice/acetone condenser, was charged with anhydrous
ether (8 mL), anhydrous tetrahydrofuran (30 mL), chlorotri-
ethylsilane (15.1 g, 0.10 mol), and vinylidene fluoride (8.0 g,
0.125 mol) and cooled to -110 °C with a pentane/liquid
nitrogen bath. tert-BuLi (70 mL, 1.7 M in pentane, 0.119 mol)
P r ep a r a tion of (Z)-1,2-Diflu or o-3,3-d im eth yl-1-(tr im -
eth ylsilyl)-1-bu ten e (tr a n s-ter t-Bu CFdCFSiMe3, 11). Simi-
larly, (trifluorovinyl)trimethylsilane, prepared in situ from
chlorotrifluoroethylene (25.6 g, 0.22 mol), n-BuLi (88 mL, 2.5
M in hexane, 0.22 mol), and chlorotrimethylsilane (21.7 g, 0.2
mol) in THF, was reacted with tert-BuLi (130 mL, 1.7 M in
pentane, 0.22 mol) to give 28.8 g of (Z)-1,2-difluoro-3,3-

(E)- and (Z)-(2-Substituted-1,2-difluoroethenyl)stannanes
J . Org. Chem., Vol. 62, No. 4, 1997 1069
was slowly added over 3 h via syringe with stirring. During
addition, the solution was maintained between -100 to -110
°C. After the addition was completed, the solution was stirred
at -100 °C for 1 h, -78 °C for 2 h, and then allowed to warm
to room temperature and stirred overnight. The reaction
mixture was treated with 0.1 N aqueous hydrogen chloride
(20 mL) and extracted with ether (100 mL × 2). The combined
organic layers were washed with brine and dried over MgSO4.
After evaporation of ether, the residue was fractionally
distilled through a 25 cm long spinning band column to give
the (2,2-difluorovinyl)triethylsilane (10.7 g) in 60% yield, bp
24.4 Hz), -4.3 (s) ppm. GC-MS: 277 (M+ - 1, 1.63), 182 (100).
FTIR: 1770 (CdC), 1751 (C ) C) cm-1
.
P r ep a r a tion of (E) a n d (Z)-1,2-Diflu or o-1-(tr ibu tyl-
sta n n yl)-1-a lk en es Usin g Tr ibu tyltin Ch lor id e. P r ep a -
r a t ion of (Tr iflu or ovin yl)t r ib u t ylst a n n a n e (CF 2dCF -
Sn Bu 3, 1a ). A round-bottom flask equipped with a Teflon-
coated magnetic stir bar, a nitrogen tee, and rubber septum
was charged with anhydrous potassium fluoride (0.22 g, 3.8
mmol), CF2dCFSiEt3 (0.48 g, 2.4 mmol), and dry DMF (2 mL).
Tributyltin chloride (0.57 g, 1.8 mmol) was added via syringe,
and the reaction mixture was stirred at room temperature
overnight. Analysis by 19F NMR indicated the absence of the
vinylsilane. The reaction mixture was extracted with ether
and washed with water. Evaporation of solvent followed by
chromatography on silica gel using hexane as eluant gave 0.6
g of (trifluorovinyl)tributylstannane in 92% yield. 19F NMR
(CDCl3): -88.5 (dd, J ) 79.5, 33.7 Hz, 1F), -123.1 (dd, J )
113.8, 79.5 Hz, 1F), -193.1 (dd, J ) 113.8, 34.4 Hz, 1F) ppm.
1H NMR (CDCl3): 1.55 (m, 2H), 1.33 (m, 2H), 1.10 (m, 2H),
0.91 (m, 3H) ppm. 13C NMR (CDCl3): 161.7 (ddd, J ) 315.6,
265.5, 34.1 Hz), 133.3 (ddd, J ) 291.1, 86.1, 9.7 Hz), 28.8 (s),
27.2 (s), 13.6 (s), 10.0 (s) ppm.
P r ep a r a t ion of (Z)-(1,2-Diflu or ovin yl)t r ib u t ylst a n -
n a n e (tr a n s-HCF dCF Sn Bu 3, 2a ). Similarly, the reaction
of (Z)-(1,2-difluorovinyl)triethylsilane (5.0 g, 28.1 mmol) with
tributyltin chloride (9.22 g , 28.3 mmol) in the presence of
anhydrous potassium fluoride (2.66 g, 45.9 mmol) in dry DMF
(20 mL) gave 8.26 g of (Z)-(1,2-difluorovinyl)tributylstannane
in 83% yield. GLPC 97.8%. 19F NMR (CDCl3): -173.0 (dd, J
) 119.2, 11.1 Hz, 1F), -177.7 (dd, J ) 119.6, 83.0 Hz, 1F) ppm.
1H NMR (CDCl3): 7.68 (dd, J ) 83.1, 11.1 Hz, 1H), 1.55 (m,
6H), 1.33 (m, 6H), 1.09 (m, 6H), 0.90 (t, J ) 7.3 Hz, 9H) ppm.
13C NMR (CDCl3): 165.8 (dd, J ) 297.9, 78.7 Hz), 153.8 (dd,
J ) 229.5, 47.0 Hz), 28.8 (s), 28.8 (d, J ) 21.4 Hz), 27.1 (s),
27.1 (d, J ) 59.9 Hz), 13.6 (s), 9.8 (s) ppm. GC-MS: 297 (M+-
C4H9, 91.6), 295 (76.7), 293 (44.1), 253 (70.3), 241 (88.6), 195
(33.2), 181 (37.1), 177 (64.9), 139 (71.8), 121 (36.6), 57 (66.3).
HRMS: Calcd for C10H19F2Sn (M+ - Bu): 297.0477. Found:
297.0476.
3
140 °C. 1H NMR (CDCl3): 3.74 [dd, J HF(trans) ) 42.1 Hz,
3J HF(cis) ) 9.9 Hz, 1H], 0.95 (t, J ) 8.0 Hz, 9H), 0.62 (q, J )
2
8.0 Hz, 6H) ppm. 19F NMR (CDCl3): -62.09 [dd, J FF ) 24.2
Hz, 3J HF(cis) ) 9.9 Hz, 1F], -72.48 (dd, 3J HF ) 42.1 Hz, 2J FF
)
24.2 Hz, 1F) ppm. 13C NMR (CDCl3): 159.4 (dd, J ) 306.4,
287.5 Hz), 65.24 (dd, J ) 34.2, 4.3 Hz), 7.02 (s), 3.82 (s) ppm.
GC-MS: 178 (M+, 2.05), 149 (M+ - C2H5, 14.46). FTIR (CCl4):
1689.89 (CdC) cm-1. HRMS: Calcd for C8H16F2Si: 178.0989.
Found: 178.1011.
P r ep a r a tion of (Z)-1-Ch lor o-2-flu or o-1-(tr im eth ylsilyl)-
1-h exen e ((Z)-n -Bu CF dCClSiMe3, 16). (Z)-1-Chloro-2-
fluoro-1-(trimethylsilyl)-1-hexene was prepared according to
the literature procedure27 in 80% yield, bp 60-61 °C/1.5 mmHg
(lit.27 82-84 °C/20 mmHg). 1H NMR (CDCl3): 2.50 (dt, 3J HF
)
3
22.7 Hz, J HH ) 7.3 Hz, 2H), 1.53 (m, 2H), 1.37 (m, 2H), 0.93
(t, J ) 7.3 Hz, 3H), 0.21 (d, J ) 1.3 Hz, 9H) ppm. 19F NMR
3
(CDCl3): -95.32 (t, J HF ) 22.7 Hz, 1F) ppm. GC-MS: 208
(M+, 10.04), 151 (M+ - C4H9, 2.15). FTIR: 1640.75 (CdC)
cm-1
.
P r epar ation of (Z)-1-(Tr ieth ylsilyl)-1,2,3,4,4-pen taflu or o-
1,3-bu ta d ien e (tr a n s-CF 2dCF CF dCF SiEt3, 13). A 250 mL
three-necked, round-bottomed flask equipped with a water
condenser, a rubber septum, a thermometer, a Teflon-coated
magnetic stir bar, and a nitrogen gas inlet was charged with
tetrakis(triphenylphosphine)palladium (0.3 g), (E)-(1,2-dif-
luoro-2-iodovinyl)triethylsilane (trans-ICFdCFSiEt3, 15.2 g, 50
mmol) and 20 mL of dry tetrahydrofuran. To the stirred
solution, (trifluorovinyl)zinc iodide19 in THF (72 mL, 0.76 M,
55 mmol) was added via syringe. The reaction mixture was
heated at 60 °C until 19F NMR analysis showed no silyl iodide
remained (about 12-24 h), and it was extracted with ether
(200 mL × 3). The combined ethereal layers were washed with
saturated brine solution and dried over MgSO4. After evapo-
ration of solvents, the residue was fractionally distilled to
afford (Z)-1-(triethylsilyl)-1,2,3,4,4-pentafluoro-1,3-butadiene
(10.1 g) in 81% yield, bp 83-85 °C/20 mmHg. GLPC 100%.
1H NMR (CDCl3): 1.02 (t, J ) 7.7 Hz, 9H), 0.80 (q, J ) 7.7
Hz, 6H) ppm. 19F NMR (CDCl3): -96.5 (dd, J ) 52.0, 32.0
Hz, 1F), -107.6 (dddd, J ) 115.0, 52.0, 22.5, 12.4 Hz, 1F),
-151.0 (ddt, J ) 138.0, 19.9, 8.3 Hz), -158.9 (ddd, J ) 138.0,
32.0, 11.5 Hz, 1F), -182.6 (dtd, J ) 115.0, 32.0, 10.4 Hz, 1F)
ppm. 13C NMR (CDCl3): 161.7 (dd, J ) 281.2, 70.8 Hz), 154.2
(tdm, J ) 291.6, 52.4 Hz), 150.2 (dddm, J ) 227.2, 22.2, 10.4
Hz), 119.5 (dddd, J ) 232.2, 57.9, 33.7, 24.1 Hz), 7.07 (s), 2.55
(s) ppm. GC-MS: 258 (M+, 1.34), 105 (100). FTIR: 1773 (CdC)
P r ep a r a t ion of (E)-(1,2-Diflu or ovin yl)t r ib u t ylst a n -
n a n e (cis-HCF dCF Sn Bu 3, 3a ). Similarly, the reaction of
(E)-(1,2-difluorovinyl)triethylsilane (2.1 g, 11.8 mmol) with
tributyltin chloride (3.2 g, 9.8 mmol) in the presence of
anhydrous potassium fluoride (0.8 g, 13.8 mmol) in dry DMF
(5 mL) gave 2.6 g of (E)-(1,2-difluorovinyl)tributylstannane in
74% yield. Bp 87-90 °C/0.2 mmHg, GLPC 99%. 19F NMR
(CDCl3): -143.0 (dd, J ) 77.3, 9.2 Hz, 1F), -147.0 (dd, J )
1
25.7, 9.2 Hz, 1F) ppm; H NMR (CDCl3): 5.95 (dd, J ) 77.3,
25.5 Hz, 1H), 5.96 (ddd, J ) 77.3, 25.5, 4.8 Hz, 1H), 1.53 (m,
6H), 1.33 (m, 6H), 1.03 (tm, J ) 8.3 Hz, 6H), 0.91 (t, J ) 7.2
Hz, 9H) ppm. 13C NMR (CDCl3): 154.9 (dd, J ) 313.1, 7.3
Hz), 141.5 (dd, J ) 282.3, 7.1 Hz), 28.8 (s), 28.8 (d, J ) 21.9
Hz), 27.2 (s), 27.2 (d, J ) 59.2 Hz), 13.6 (s), 10.0 (s) ppm. GC-
MS: 297 (M+ - C4H9, 95.0), 295 (75.3), 293 (44.0), 253 (9.6),
241 (100.0). HRMS: Calcd for C10H19F2Sn (M+ - Bu):
297.0477. Found: 297.0472.
cm-1
.
P r ep a r a tion of (E)-1-Iod o-(1,2-d iflu or ovin yl)tr ibu tyl-
sta n n a n e (tr a n s-ICF dCF Sn Bu 3, 4a ). Similarly, the reac-
tion of (E)-2-iodo-(1,2-difluorovinyl)triethylsilane (4.95 g, 16.3
mmol) with tributyltin chloride (5.21 g , 16.0 mmol) in the
presence of anhydrous potassium fluoride (1.33 g, 22.9 mmol)
in dry DMF (60 mL) gave 6.5 g of (E)-2-iodo-(1,2-difluorovinyl)-
tributylstannane in 85% yield. 19F NMR (CDCl3): -122.8 (d,
J ) 137.3 Hz, 1F), -133.7 (d, J ) 137.3 Hz, 1F) ppm. 1H NMR
(CDCl3): 1.55 (m, 2H), 1.34 (m, 2H), 1.23 (m, 2H), 0.91 (t, J )
7.3 Hz, 3H) ppm. 13C NMR (CDCl3): 166.9 (dd, J ) 313.1,
84.2 Hz), 108.0 (dd, J ) 300.9, 55.9 Hz), 28.7 (s), 28.6 (d, J )
22.3 Hz), 27.5 (s), 13.6 (s), 10.6 (t, J ) 1.5 Hz) ppm. GC-MS:
P r ep a r a tion of (Z)-1-(Dim eth ylp h en ylsilyl)-1,2,3,4,4-
p en t a flu or ob u t a d ien e (tr a n s-CF 2dCF CF dCF SiMe2P h ,
14). Similarly, the reaction of (E)-1,2-difluoro-1-iodo-2-(dim-
ethylphenylsilyl)ethylene (trans-ICFdCFSiMe2Ph, 23.4 g, 72
mmol) and CF2dCFZnI in THF (approximately 100 mmol) in
the presence of tetrakis(triphenylphosphine)palladium (1.0
g) yielded (Z)-1-(dimethylphenylsilyl)-1,2,3,4,4-pentafluorob-
utadiene (16.4 g) in 82% yield, bp 98-102 °C/20 mmHg. GLPC
97%. 1H NMR (CDCl3): 7.5 (m, 2H), 7.3 (m, 3H), 0.5 (s, 6H)
ppm. 19F NMR (CDCl3): -95.8 (ddm, J ) 50.5, 31.8 Hz, 1F),
-106.9 (dddd, J ) 114.6, 50.5, 22.8, 12.9 Hz, 1F), -151.2 (dm,
J ) 139.9 Hz, 1F), -157.4 (ddd, J ) 139.9, 33.2, 12.9 Hz, 1F),
-183.2 (dddd, J ) 114.6, 32.8, 31.8, 10.8 Hz) ppm. 13C NMR
(CDCl3): 160.7 (ddm, J ) 280.7, 69.5 Hz), 153.7 (tdm, J )
287.0, 46.3 Hz), 149.4 (ddm, J ) 229.3, 39.2 Hz), 133.9 (s),
133.8 (s), 130.3 (s), 128.3 (s), 119.4 (dddd, J ) 231.9, 59.0, 34.6,
423 (M+ - C4H9, 22.66), 253 (100). FTIR: 1606.0 (CdC) cm-1
.
P r ep a r a tion of (Z)-2-Iod o-(1,2-d iflu or ovin yl)tr ibu tyl-
sta n n a n e (cis-ICF dCF Sn Bu 3, 5a ). Similarly, the reaction
of (Z)-2-iodo-(1,2-difluorovinyl)triethylsilane (1.53 g, 5.0 mmol)
with tributyltin chloride (2.6 g, 8.0 mmol) at 50 °C in the
presence of anhydrous potassium fluoride (0.48 g, 8.0 mmol)
in dry DMF (5 mL) gave (Z)-1-iodo-(1,2-difluorovinyl)tributyl-
stannane in 82% yield. 1H NMR (CDCl3): 1.55 (m, 6H), 1.35
(27) Martin, S.; Sauvetre, R.; Normant, J . F. J . Organomet. Chem.
1986, 303, 317.

1070 J . Org. Chem., Vol. 62, No. 4, 1997
Xue et al.
(m, 6H), 1.16 (m, 6H), 0.91 (t, J ) 7.3 Hz, 9H) ppm. 19F NMR
(CDCl3): -83.32 (d, J ) 4.8 Hz, 1F), -108.1 (d, J ) 4.8 Hz,
1F) ppm.
1.21 (dd, J ) 2.4, 1.6 Hz, 9H), 1.02 (m, 6H), 0.91 (t, J ) 7.2
3
Hz, 9H) ppm. 19F NMR (CDCl3): -151.1 (d, J FF ) 112.6 Hz,
3
4
1F), 164.0 (dd, J FF ) 112.6 Hz, J HF ) 2.0 Hz, 1F) ppm. 13C
NMR (CDCl3): 168.5 (dd, J ) 225.2, 26.5 Hz), 157.9 (dd, J )
299.7, 113.9 Hz), 35.54 (dd, J ) 26.0, 1.9 Hz), 28.93 (s), 27.67
(dd, J ) 4.8, 1.2 Hz), 27.18 (s), 13.68 (s), 9.93 (t, J ) 2.2 Hz)
ppm. GC-MS: 353 (M+-C4H9, 8.43), 253 (100). FTIR: 1650.23
(CdC) cm-1. HRMS: Calcd for C14H27F2Sn (M+-Bu): 353.1103.
Found: 353.1112.
P r ep a r a tion of (Z)-1,2-Diflu or o-1-(tr ibu tylsta n n yl)-1-
p r op en e (tr a n s-MeCF dCF Sn Bu 3, 8a ). Gen er a l P r oce-
d u r e. A 100 mL, round-bottom flask equipped with a nitrogen
tee, a condenser, and Teflon-coated magnetic stir bar was
charged with dry DMF (15 mL), fresh dried potassium fluoride
(3.5 g, 60 mmol), tributyltin chloride (10.0 g, 30.7 mmol), and
(Z)-1,2-difluoro-1-(trimethylsilyl)-1-propene (4.5 g, 30 mmol).
The mixture was stirred at 80 °C for about 10 h, and the
starting silane had disappeared by 19F NMR analysis. The
reaction mixture was treated with water (50 mL) and extracted
with ethyl ether (50 mL × 2). The ethereal phase was dried
and concentrated. The residue was purified on a silica gel
column using hexane as eluant to afford 8.2 g of (Z)-1,2-
difluoro-1-(tributylstannyl)-1-propene in 74% yield as a color-
P r ep a r a tion of (Z)-1,2-Diflu or o-3,3-d im eth yl-1-(tr ibu -
tylstan n yl)-1-bu ten e (tr a n s-ter t-Bu CFdCFSn Bu 3, 7a) fr om
th e Cor r esp on d in g Tr ieth ylsila n e (7). Similarly, the reac-
tion of (Z)-1,2-difluoro-3,3-dimethyl-1-(triethylsilyl)-1-butene
(11.7 g, 50 mmol), potassium fluoride (5.8 g, 100 mmol), and
tributyltin chloride (16.3 g, 50.1 mmol) in DMF (30 mL) at 80
°C for 24 h afforded (Z)-1,2-difluoro-3,3-dimethyl-1-(tributyl-
stannyl)-1-butene (14.4 g) as a colorless oil in 71% yield.
P r ep a r a tion of (Z)-1,2-Diflu or o-1-(tr ibu tylsta n n yl)sty-
r en e (tr a n s-P h CF dCF Sn Bu 3, 12a ). Similarly, the reaction
of (Z)-1,2-difluoro-1-(trimethylsilyl)styrene (4.24 g, 20 mmol),
potassium fluoride (2.3 g, 40 mmol), and tributyltin chloride
(7.8 g, 24 mmol) in DMF (15 mL) at room temperature for 24
h afforded (Z)-1,2-difluoro-1-(tributylstannyl)styrene (6.0 g) as
a colorless oil in 70% yield. 1H NMR (CDCl3): 7.67(m, 2H),
3
less oil. 1H NMR (CDCl3): 2.03 (dd, J HF ) 17.1 Hz, J ) 6.2
Hz, 3H), 1.53 (m, 6H), 1.32 (m, 6H), 1.15 (m, 6H), 0.90 (t, J )
7.2 Hz, 9H) ppm. 19F NMR (CDCl3): -141.5 (dq, 3J FF ) 116.3
3
3
Hz, J HF ) 17.1 Hz, 1F), -165.3 (dm, J FF ) 116.3 Hz, 1F)
ppm. 13C NMR (CDCl3): 162.2 (dd, J ) 225.0, 35.7 Hz), 158.9
(dd, J ) 293.3, 97.6 Hz), 28.88 (s), 27.18 (s), 13.62 (s), 12.3
(dm, J ) 31.5 Hz), 9.80 (t, J ) 1.7 Hz) ppm. GC-MS: 311 (M+
- C4H9, 29.70), 253 (100). FTIR: 1675.76 (CdC) cm-1
.
7.34 (m, 3H), 1.58 (m, 6H), 1.35 (m, 6H), 1.14 (m, 6H), 0.91 (t,
HRMS: Calcd for C11H21F2Sn (M+ - Bu): 311.0633. Found:
311.0623.
3
J ) 7.2 Hz, 9H) ppm. 19F NMR (CDCl3): -154.2 (d, J FF
)
113.1 Hz, 1F), -155.0 (d, 3J FF ) 113.1 Hz, 1F) ppm. 13C NMR
(CDCl3): 163.7 (d, J ) 202.0 Hz), 159.5 (d, J ) 187.4 Hz), 129.9
(d, J ) 25.7 Hz), 128.5 (d, J ) 1.8 Hz), 128.3 (d, J ) 1.8Hz),
125.2 (dd, J ) 9.5 Hz, J ) 7.7 Hz), 28.88 (s), 27.17 (s), 13.65
(s), 10.14 (s) ppm. GC-MS: 373 (M+-C4H9, 6.66), 253 (100).
FTIR: 1628.61 (CdC), 1600.89 (Ar) cm-1. HRMS: Calcd for
C16H23F2Sn (M+ - Bu): 373.0790. Found: 373.0790.
P r ep a r a tion of (Z)-1,2-Diflu or o-1-(tr ibu tylsta n n yl)-1-
h exen e (tr a n s-n -Bu CF dCF Sn Bu 3, 6a ). Similarly, the reac-
tion of (Z)-1,2-difluoro-1-(trimethylsilyl)-1-hexene (9.6 g, 50
mmol), potassium fluoride (5.8 g, 100 mmol), and tributyltin
chloride (16.3 g, 50.1 mmol) in DMF (30 mL) at 80 °C for 10 h
afforded (Z)-1,2-difluoro-1-(tributylstannyl)-1-hexene (16.0 g)
as a colorless oil in 78% yield. 1H NMR (CDCl3): 2.42 (m, 2H),
1.52 (m, 8H), 1.32 (m, 8H), 1.15 (m, 6H), 0.89 (m, 12H) ppm.
P r ep a r a t ion of (2,2-Diflu or ovin yl)t r ib u t ylst a n n a n e
(CF 2dCHSn Bu 3, 15a ). Similarly, the reaction of (2,2-difluo-
rovinyl)triethylsilane (1.78 g, 10.0 mmol) with tributyltin
chloride (3.3 g, 10.2 mmol) in the presence of anhydrous
potassium fluoride (1.0 g, 17.3 mmol) in dry DMF (10 mL) gave
1.76 g of (2,2-difluorovinyl)tributylstannane in 50% yield. 1H
NMR (CDCl3): 3.87 [dd, 3J HF(trans) ) 47.6 Hz, 3J HF(cis) ) 9.9
Hz, 1H], 1.49 (m, 6H), 1.32 (m, 6H), 0.97 (m, 6H), 0.89 (t, J )
3
3
19F NMR (CDCl3): -149.1 (dt, J FF ) 115.7 Hz, J HF ) 22.9
3
4
Hz, 1F), -166.3 (dt, J FF ) 115.7 Hz, J HF ) 5.7 Hz, 1F) ppm.
13C NMR (CDCl3): 165.6 (dd, J ) 227.4, 34.8 Hz), 158.4 (dd,
J ) 293.9, 98.6 Hz), 28.95 (s), 28.11 (m), 27.19 (s), 26.01 (dd,
J ) 26.8, 2.1 Hz), 22.01 (s), 13.69 (s), 13.63 (s), 9.87 (s) ppm.
GC-MS: 353 (M+ - C4H9, 18.48), 253 (100). FTIR: 1667.56
(CdC) cm-1
.
HRMS: Calcd for C14H27F2Sn (M+ - Bu):
2
8.0 Hz, 9H) ppm. 19F NMR (CDCl3): -61.23 [dd, J FF ) 36.9
Hz, 3J HF(cis) ) 9.9 Hz, 1F], -73.40 [dd, 3J HF(trans) ) 47.6 Hz,
2J FF ) 36.9 Hz, 1F] ppm. 13C NMR (CDCl3): 157.8 (dd, J )
311.6, 277.1 Hz), 63.74 (dd, J ) 48.3, 14.4 Hz), 28.88 (s), 27.16
(s), 13.62 (s), 9.99 (s) ppm. GC-MS: 297 (M+-C4H9, 48.44), 253
(100). FTIR: 1678.58 (CdC) cm-1. HRMS: Calcd for C10H19F2-
Sn (M+-Bu): 297.0477. Found: 297.0474.
353.1103. Found: 353.1101.
P r ep a r a tion of (Z)-1,2-Diflu or o-1-(tr ibu tylsta n n yl)-1-
h exen e (tr a n s-n -Bu CF dCF Sn Bu 3, 6a ) fr om th e Cor r e-
sp on d in g Tr iet h ylsila n e (6). Similarly, the reaction of
(Z)-1,2-difluoro-1-(triethylsilyl)-1-hexene (11.7 g, 50 mmol),
potassium fluoride (5.8 g, 100 mmol), and tributyltin chloride
(16.3 g, 50.1 mmol) in DMF (30 mL) at 80 °C for 24 h afforded
(Z)-1,2-difluoro-1-(tributylstannyl)-1-hexene (14.7 g) as a color-
less oil in 72% yield.
P r ep a r a tion of (Z)-1-Ch lor o-2-flu or o-1-(tr ibu tylsta n -
n yl)-1-h exen e ((Z)-n -Bu CF dCClSn Bu 3, 16a ). Similarly,
reaction of (Z)-n-BuCFdCClSiMe3 (4.2 g, 20 mmol) with
tributyltin chloride (6.6 g, 20.3 mmol) in the presence of
potassium fluoride (2.3 g, 40 mmol) in DMF (20 mL) at 80 °C
P r ep a r a tion of (Z)-1,2-Diflu or o-3-m eth yl-1-(tr ibu tyl-
stan n yl)-1-pen ten e (tr a n s-sec-Bu CFdCFSn Bu 3, 9a). Simi-
larly, reaction of (Z)-1,2-difluoro-3-methyl-1-(trimethylsilyl)-
1-pentene (9.6 g, 50 mmol), potassium fluoride (5.8 g, 100
mmol), and tributyltin chloride (16.5 g, 50.7 mmol) in DMF
(50 mL) at 80 °C for 10 h afforded 17.8 g (87% yield) of (Z)-
1,2-difluoro-3-methyl-1-(tributylstannyl)-1-pentene as a color-
less oil. 1H NMR (CDCl3): 2.85 (m, 1H), 1.25-1.70 (m, 15H),
0.85-1.12 (m, 20H) ppm. 19F NMR (CDCl3): -162.3 (dd, 3J FF
) 115.1 Hz, 3J HF ) 33.1 Hz, 1F), -167.7 (dd, 3J FF ) 115.1 Hz,
4J HF ) 5.7 Hz, 1F) ppm. 13C NMR (CDCl3): 167.8 (dd, J )
230.1, 32.7 Hz), 157.8 (dd, J ) 293.6, 99.8 Hz), 32.91 (dd, J )
25.6, 2.1 Hz), 28.89 (s), 27.11 (s), 26.22 (d, J ) 2.7 Hz), 17.33
(d, J ) 2.4 Hz), 13.65 (s), 11.9 (s), 9.86 (t, J ) 2.0 Hz) ppm.
GC-MS: 353 (M+-C4H9, 5.51), 253 (100). FTIR: 1665.19 (CdC)
for 12 h afforded the corresponding stannane (7.2 g) in 85%
3
yield as a colorless liquid. 1H NMR (CDCl3): 2.51 (dt, J HF
)
3
22.1 Hz, J HH ) 7.2 Hz, 2H), 1.52 (m, 8H), 1.33 (m, 8H), 1.06
(m, 6H), 0.93 (t, J ) 7.2 Hz, 3H), 0.90 (t, J ) 7.3 Hz, 9H) ppm.
19F NMR (CDCl3): -94.29 (t, J HF ) 22.1 Hz, 1F) ppm. 13C
3
NMR (CDCl3): 168.3 (d, J ) 240.4 Hz), 114.1 (d, J ) 94.6 Hz),
28.80 (s), 28.46 (s), 28.08 (m), 27.18 (s), 22.00 (s), 13.78 (s),
13.66 (s), 10.67 (d, J ) 1.2 Hz) ppm. GC-MS: 369 (M+-C4H9,
4.70), 251 (100). FTIR: 1635.53 (CdC) cm-1. HRMS: Calcd
for C14H27ClFSn (M+-Bu): 369.0807. Found: 369.0772.
P r ep a r a tion of (Z)-1-(Tr ibu tylsta n n yl)-1,2,3,4,4-p en -
ta flu or o-1,3-bu ta dien e (tr a n s-CF2dCFCFdCFSn Bu 3, 13a )
fr om (Z)-1-(Tr ieth ylsilyl)-1,2,3,4,4-p en ta flu or obu ta d ien e
(tr a n s-CF 2dCF CF dCF SiE t3, 13). Similarly, reaction of
(Z)-1-(triethylsilyl)-1,2,3,4,4-pentafluorobutadiene (trans-CF2d
CFCFdCFSiEt3, 19.5 g, 75.5 mmol) with tributyltin chloride
(27.7 g, 85.0 mmol) in the presence of potassium fluoride (4.93
g, 85.0 mmol) in DMF (120 mL) at room temperature for 30 h
afforded the corresponding stannane (24.5 g) in 75% yield. 1H
NMR (CDCl3): 1.55 (m, 6H), 1.35 (m, 6H), 1.1 (m, 6H), 0.9 (t,
J ) 7.3 Hz, 9H) ppm. 19F NMR (CDCl3): -97.2 (dd, J ) 53.3,
29.1 Hz, 1F), -108.6 (dddd, J ) 115.0, 53.3, 19.3, 12.3 Hz,
1F), -142.2 (dm, J ) 129.8 Hz, 1F), -160.9 (ddd, J ) 129.8,
cm-1
.
HRMS: Calcd for C14H27F2Sn (M+-Bu): 353.1103.
Found: 353.1086.
P r ep a r a tion of (Z)-1,2-Diflu or o-3,3-d im eth yl-1-(tr ibu -
tylsta n n yl)-1-bu ten e (tr a n s-ter t-Bu CF dCF Sn Bu 3, 7a ).
Similarly, the reaction of (Z)-1,2-difluoro-3,3-dimethyl-1-(tri-
methylsilyl)-1-butene (9.6 g, 50 mmol), potassium fluoride (5.8
g, 100 mmol), and tributyltin chloride (16.3 g, 50.1 mmol) in
DMF (30 mL) at 80 °C for 10 h afforded (Z)-1,2-difluoro-3,3-
dimethyl-1-(tributylstannyl)-1-butene (16.2 g) as a colorless oil
in 79% yield. 1H NMR (CDCl3): 1.53 (m, 6H), 1.32 (m, 6H),

(E)- and (Z)-(2-Substituted-1,2-difluoroethenyl)stannanes
J . Org. Chem., Vol. 62, No. 4, 1997 1071
34.7, 12.3 Hz), -181.4 (dddd, J ) 115.0, 34.7, 30.0, 10.7 Hz)
ppm. 13C NMR (CDCl3): 167.7 (ddm, J ) 323.0, 98.3 Hz),
153.4 (tdm, J ) 288.2, 44.0 Hz), 149.3 (dm, J ) 215.9 Hz),
118.8 (dm, J ) 233.2 Hz), 28.8 (s), 27.2 (s), 13.5 (s), 10.3 (s)
ppm. GC-MS: 377 (M+-Bu, 4.12), 257 (15.53), 251 (100).
P r ep a r a tion of (Z)-1,2-Diflu or o-1-(tr ibu tylsta n n yl)-1-
h exen e (6a ). Similarly, the reaction of (Z)-1,2-difluoro-1-
(trimethylsilyl)-1-hexene (5.76 g, 30 mmol), potassium fluoride
(0.26 g, 4.5 mmol), and bis(tributyltin) oxide (10.0 g, 16.8
mmol) in DMF (20 mL) at 80 °C for 20 h afforded (Z)-1,2-
difluoro-1-(tributylstannyl)-1-hexene (11.0 g) as a colorless oil
in 90% yield.
P r ep a r a tion of (Z)-1,2-Diflu or o-3-m eth yl-1-(tr ibu tyl-
sta n n yl)-1-p en ten e (9a ). Similarly, the reaction of (Z)-1,2-
difluoro-3-methyl-1-(trimethylsilyl)-1-pentene (5.76 g, 30 mmol),
potassium fluoride (0.18 g, 3.1 mmol), and bis(tributyltin) oxide
(9.0 g, 15.1 mmol) in DMF (30 mL) at 80 °C for 10 h afforded
10.7 g (87% yield) of (Z)-1,2-difluoro-3-methyl-1-(tributylstan-
nyl)-1-pentene as a colorless oil.
P r ep a r a tion of (Z)-1,2-Diflu or o-3,3-d im eth yl-1-(tr ibu -
tylsta n n yl)-1-bu ten e (7a ). Similarly, the reaction of (Z)-1,2-
difluoro-3,3-dimethyl-1-(trimethylsilyl)-1-butene (5.76 g, 30
mmol), potassium fluoride (0.18 g, 3.1 mmol), and tributyltin
oxide (9.0 g, 15.1 mmol) in DMF (30 mL) at 80 °C for 10 h
afforded (Z)-1,2-difluoro-3,3-dimethyl-1-(tributylstannyl)-1-
butene (10.8 g) as a colorless oil in 88% yield.
P r ep a r a tion of (Z)-1,2-Diflu or o-1-(tr ibu tylsta n n yl)sty-
r en e (12a ). Similarly, the reaction of (Z)-1,2-difluoro-1-
(trimethylsilyl)styrene (4.24 g, 20 mmol), potassium fluoride
(0.12 g, 2.1 mmol), and tributyltin oxide (6.0 g, 10.1 mmol) in
DMF (20 mL) at 80 °C for 10 h afforded (Z)-1,2-difluoro-1-
(tributylstannyl)styrene (6.78 g) as a colorless oil in 79% yield.
FTIR: 2972 (s), 2907 (s), 1418 (w), 1359 (w) cm-1
.
P r ep a r a tion of (Z)-1-(Tr ibu tylsta n n yl)-1,2,3,4,4-p en -
ta flu or o-1,3-bu ta dien e (tr a n s-CF2dCFCFdCFSn Bu 3, 13a )
fr om (Z)-1-(Dim eth ylp h en ylsilyl)-1,2,3,4,4-p en ta flu or ob-
u ta d ien e (tr a n s-CF 2dCF CF dCF SiMe2P h , 14). Similarly,
reaction of (Z)-1-(dimethylphenylsilyl)-1,2,3,4,4-pentafluorob-
utadiene (trans-CF2dCFCFdCFSiMe2Ph, 21.0 g, 75.5 mmol)
with tributyltin chloride (27.7 g, 85.0 mmol) in the presence
of potassium fluoride (4.93 g, 85.0 mmol) in DMF (120 mL) at
room temperature for 30 h afforded the corresponding stan-
nane (22.6 g) in 69% yield.
P r ep a r a tion of (Z)-1,2-Diflu or o-1-(tr ibu tylsta n n yl)-1-
a lk en es Usin g Bis(tr ibu tyltin )oxid e. P r ep a r a tion of (Z)-
1,2-Diflu or o-1-(tr ibu tylsta n n yl)-1-p r op en e (8a ). Gen er a l
P r oced u r e. A 100 mL, round-bottom flask equipped with a
nitrogen tee, a condenser, and Teflon-coated magnetic stir bar
was charged with dry DMF (25 mL), fresh dried potassium
fluoride (0.18 g, 3.1 mmol), bis(tributyltin) oxide (9.0 g, 15.1
mmol), and (Z)-1,2-difluoro-1-(trimethylsilyl)-1-propene (4.5 g,
30 mmol). The mixture was stirred at 80 °C for about 12 h,
and the starting silane had disappeared by 19F NMR analysis.
The reaction mixture was treated with water (50 mL) and
extracted with ethyl ether (50 mL × 2). The ethereal phase
was washed with water, dried, and concentrated. The residue
was purified on silica gel column using hexane as eluant to
afford (Z)-1,2-difluoro-1-(tributylstannyl)-1-propene as a color-
less oil in 85% yield.
Ack n ow led gm en t. We wish to thank the National
Science Foundation for financial support of this work.
J O9618785