The stereospecific preparation of (E)-1,2-difluoro-1,2-disubstituted alkenes

Article abstract of DOI:10.1016/j.jfluchem.2012.02.010

(Z)-1,2-difluoro-2-substituted vinyl silanes were prepared stereospecifically from chlorotrifluoroethene, chlorotrimethylsilane and alkyl or aryllithium reagents. Subsequent exchange of the trimethylsilyl group via reaction of the vinylsilane with KF/n-Bu

Full text of DOI:10.1016/j.jfluchem.2012.02.010

Journal of Fluorine Chemistry 143 (2012) 94–98
Contents lists available at SciVerse ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
The stereospecific preparation of (E)-1,2-difluoro-1,2-disubstituted alkenes
*
Long Lu, Donald J. Burton
Department of Chemistry, The University of Iowa, Iowa City, IA 52242, USA
A R T I C L E I N F O
A B S T R A C T
Article history:
(Z)-1,2-difluoro-2-substituted vinyl silanes were prepared stereospecifically from chlorotrifluoroethene,
chlorotrimethylsilane and alkyl or aryllithium reagents. Subsequent exchange of the trimethylsilyl
group via reaction of the vinylsilane with KF/n-Bu3SnCl/DMF stereospecifically afforded the
corresponding (Z)-1,2-difluoro-2-substituted vinyl stannanes. Pd(PPh3)4/Cu(I)I/DMF coupling of the
vinyl stannanes with substituted aromatic iodides stereospecifically provided the (E)-1,2-difluoro-1-
substituted aryl-alkenes in excellent yield.
Received 23 December 2011
Received in revised form 12 February 2012
Accepted 16 February 2012
Available online 25 February 2012
Keywords:
ß 2012 Elsevier B.V. All rights reserved.
Palladium catalysis
Silicon/stannane exchange
Cu(I)I co-catalysis
Aryl iodides
(E)-1,2-difluoroalkenes
1. Introduction
monosubstituted (Z)-1,2-difluorovinylsilane [15], Eq. (1).
The unique properties of fluoroorganic compounds, which
contain one or more fluorines at strategic positions in the
molecule, continue to attract the interest of polymer chemists,
pharmaceutical chemists and agrochemists [1]. In most cases, only
an isolated saturated hydrogen or one vinyl hydrogen was replaced
by fluorine. Recent reports from our laboratory have demonstrated
the utility of fluorine-containing vinyl stannanes as useful
synthons for the preparation of fluoroolefin derivatives [2–13].
Although the introduction of the (E)-1,2-difluoroethene unit into
organic compounds has been investigated by Normant and co-
workers [14], a stereospecific entry into 1,2-disubstituted-1,2-
difluoroolefins had not been described. Our work with 1,2-
difluorostannanes suggested a useful synthetic methodology into
this class of compounds, and this work outlines a stereospecific
route to (E)-1,2-difluoro-1,2-disubstituted olefins [13].
(1)
The corresponding perfluorovinyltin gave only an exchange
reaction with organolithium reagents to form the unstable
perfluorovinyllithium [15,16]. Subsequently, Normant and co-
workers demonstrated that the corresponding trifluorovinyltri-
methylsilane could be generated in situ from chlorotrifluoroethene
and reacted with an equivalent of a different organolithium
reagent to provide the corresponding Seyferth vinylsilane in one
step, [17,18], Eq. (2). The Normant
2. Results and discussion
2.1. Preparation of (Z)-1,2-difluoro-2-substituted vinyl silanes and
vinyl stannanes
Seyferth and Wada reacted several organolithium reagents
or Grignard reagents with F2C55CFSiEt3 and obtained only the
(2)
methodology works very well and we have utilized this
methodology to prepare
difluoroethenylsilanes (both trimethylsilyl and triethylsilyl ana-
a variety of (Z)-(2-substituted-1,2-
* Corresponding author. Tel.: +1 319 335 1363; fax: +1 319 335 1270.
E-mail addresses: donald-burton@uiowa.edu,
logs) [19] either via a one-step or two-step process. We discovered
mburton105@gmail.com (D.J. Burton).
0022-1139/$ – see front matter ß 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2012.02.010

L. Lu, D.J. Burton / Journal of Fluorine Chemistry 143 (2012) 94–98
95
that the monosubstituted-1,2-difluorosilanes could be stereospe-
3. Conclusions
cifically converted to the corresponding stannanes via reaction of
the vinylsilane with n-Bu3SnCl and KF in DMF at RT-80 8C or with
Bu3Sn–O–SnBu3 and catalytic KF in DMF at 80 8C [19], Eqs. (3) and
(4). This simple 2-step methodology provided a convenient entry
(E)-1,2-disubstituted-1-substituted aryl-alkenes were stereo-
specifically prepared via Pd(PPh3)4/Cu(I)I/DMF coupling at RT of
(Z)-1,2-difluoro-2-substituted vinyl stannanes with substituted
aryl iodides. The requisite (Z)-1,2-difluoro-2-substituted vinyl
stannanes were prepared by stereospecific Si/Sn exchange from
the corresponding (Z)-1,2-difluoro-2-substituted vinyl silanes
via reaction with KF/n-Bu3SnCl/DMF at 80 8C. The (Z)-1,2-
disubstituted vinylsilanes were prepared from F2C55CFCl. The
(Z)-1,2-difluoro-2-substituted vinyl stannanes could also be
readily coupled with vinyl halides to stereospecifically prepare
fluorine-containing dienes [9], and coupled via Cu(II)(OAc)2 to
stereospecifically afford symmetrical dienes [12]. The aryl vinyl
stannanes, when coupled with substituted aryl iodides, also
provide a useful route to unsymmetrical (E)-1,2-difluorostil-
benes.
(3)
(4)
to the (Z)-monosubstituted vinylstannane (Z)-(RCF55CFSnBu3).
Although both the trimethyl and triethylsilanes work well in the
reactions described in Eqs. (3) and (4), the trimethylsilane is less
hindered and is more reactive in the Si–Sn exchange process and is
the preferred vinylsilane.
As we have demonstrated several times [2–13], fluorine-
containing vinylstannanes readily undergo Stille–Liebeskind
coupling with aryl iodides. The preferred conditions utilize
Pd(PPh3)4/Cu(I)I/DMF. Pd(PPh3)4 or Cu(I) alone do not catalyze
the coupling reaction or give low yields of the cross-coupled
product. Under the Liebeskind conditions, the (Z)-RCF55CFSnBu3
coupled easily at RT with aryl iodides, Eq. (5).
4. Experimental
4.1. General experimental procedures
19F NMR (282.44 MHz), 1H NMR (300.17 MHz), 13C NMR
(75.48 MHz) spectra were recorded on an AC-300-MHz
multinuclear spectrometer. All samples were taken in CDCl3
solvent and all chemical shifts were recorded in parts per million
downfield of the standards. 19F NMR spectra are referenced against
internal CFCl3, 1H NMR and 13C NMR spectra against internal TMS.
FT-IR spectra were recorded as CCl4 solutions on a Mattson Cygnus
100-FT-IR using a solution cell with a 0.1 cm path length and
absorbance frequencies are reported in cmÀ1. Low resolution GC–
MS spectra were obtained at 70 eV in the electron-impact mode on
a
TRIO-1 GC–MS instrument. High resolution mass spectra
determinations were made at the University of Iowa High
Resolution Mass Spectrometry Facility. GLPC analysis was per-
formed on a 5% OV-101 column with a thermal conductivity
detector.
(5)
All melting points were determined in a 1.2 mm capillary tube
in a Thomas-Hoover Unimelt apparatus and are uncorrected.
Table 1 illustrates twelve examples of this methodology.
Table 1
Pd(0) catalyzed coupling of (Z)-1,2-difluoroalkenylstannanes with aryl iodides.a
Entry
R
X
Yield (%)b
1
2
CH3
3-NO2
85
86
90
87
83
86
87
82
92
85
92
87
CH3
1-iodonaphthalene
4-CN
3
n-Bu
n-Bu
sec-Bu
sec-Bu
sec-Bu
tert-Bu
tert-Bu
Ph
4
3-NO2
5
3-NO2
6
4-CN
7
4-NO2
8
2-NO2
9
4-NO2
10
11
12
4-C(O)CH3
4-NO2
Ph
Ph
4-CN
a
All reactions were performed in DMF at RT on a 1 mmol scale using 3-mol% of Pd(PPh3)4 and 50 mol% Cu(I)I as catalysts.
Isolated yields based on aryl iodides.
b

96
L. Lu, D.J. Burton / Journal of Fluorine Chemistry 143 (2012) 94–98
4.2. Materials
1.0 mmol) in dry DMF (10 ml) at RT for 24 h gave 0.35 g (86%) of
(E)-1,2-difluoro-1-naphthyl-propene as colorless oil (after
chromatography) using hexane as the eluent. 19F NMR:
a
Alkyl and aryl lithium reagents were obtained from the Aldrich
Chemical Co. and used directly. Bromotrifluoroethene and
chlorotrifluoroethene were obtained from PCR Specialty Chemi-
cals. Most aromatic iodides were purchased from Aldrich. 4-
iodobenzonitrile was obtained from Kodak. Tributyltin chloride
and chlorotrimethylsilane were obtained from Aldrich and used
without further purification. KF was dried by refluxing with
benzene prior to use. DMF was dried by distillation from CaH2 and
stored under nitrogen. Tetrakis (triphenylphosphine) palladium
was prepared by Coulson’s procedure [20]. Cu(I)I was purified by
the reported procedure [21]. THF was dried by distillation from
sodium benzophenone ketyl at ambient pressure. Silica gel was
purchased from EM Science (Silica Gel 60, particle size 0.063–
d
3
3
À139.7 (dq, JFF = 133.5 Hz, JHF = 17.2 Hz, 1F), À142.6 (d,
3
3JFF = 133.5 Hz, 1F); 1H NMR:
d 8.01 (d, JHH = 7.7 Hz, 1H), 7.79
(t, 3JHH = 7.0 Hz, 2H), 7.57 (d, 3JHH = 7.0 Hz, 1H), 7.45 (m, 3H), 2.22
(dd, JHF = 17.2 Hz, JHF = 5.2 Hz, 3H); 13C NMR:
d 149.0 (dd,
3
4
1JCF = 237.5 Hz, 2JCF = 54.3 Hz), 147.3 (dd, 1JCF = 227.5 Hz,
2JCF = 48.8 Hz), 133.6 (s), 131.0 (s), 130.3 (s), 128.5 (d, 3JCF = 3.6 Hz),
2
3
128.4 (s), 126.6 (s), 126.5 (dd, JCF = 22.5 Hz, JCF = 2.0 Hz), 126.1
4
2
(s), 125.5 (d, JCF = 2.4 Hz), 124.9 (s), 12.97 (d, JCF = 5.1 Hz). GC–
MS, m/z (relative intensity): 204 (M+, 100), 189 (M+ÀCH3, 86). FTIR:
1727.70 (C55C) cmÀ1. HRMS: calcd for C13H10F2, 204.0751, obsvd
204.0747.
0200
m
m, 70–230 Mesh, ASTM). All boiling points were deter-
4.3.3. Reaction of (Z)-n-BuCF55CFSnBu3 with 4-iodobenzonitrile
Similar to 4.3.1, reaction of (Z)-n-BuCF55CFSnBu3 (0.49 g,
1.2 mmol) with 4-iodobenzonitrile (0.23 g, 1.0 mmol) in the
presence of Pd(PPh3)4 (0.05 g, 0.043 mmol), Cu(I)I (0.10 g,
0.52 mmol), in dry DMF (5 ml) at RT for 10 h afforded 0.20 g
(90%) of (E)-1,2-difluoro-1-(4-cyanophenyl)-1-hexene as a color-
less oil (after chromatography) using a mixture of ethyl acetate and
hexane (1:20) as the eluent. 19F NMR: À139.3 (dt, 3JHF = 121.5 Hz,
3JHF = 24.1 Hz, 1F), À161.2 (dt, 3JFF = 121.5 Hz, 4JHF = 5.7 Hz, 1F); 1H
mined during fractional distillation using a partial immersion
thermometer and are uncorrected.
(Z)-1,2-difluoro-1-(trimethylsilyl)-1-propene (CH3CF55CFSiMe3),
CFSiMe3), (Z)-1,2-difluoro-1-(trimethylsilyl)-1-hexene (n-BuCF55
CFSiMe3), (Z)-1,2-difluoro-3-methyl-1-(trimethylsilyl)-1-pentene
(sec-BuCF55CFSiMe3), (Z)-1,2-difluoro-3, 3-dimethyl-1-(trimethylsi-
lyl)-1-butene (tert-BuCF55CFSiMe3), and (Z)-1,2-difluoro-1-
(trimethylsilyl)-styrene (PhCF55CFSiMe3) were prepared by the
literature procedure [19]. (Z)-1,2-difluoro-1-(tributylstannyl)-1-
propene (CH3CF55CFSnBu3), (Z)-1,2-difluoro-1-(tributylstannyl)-1-
hexene (n-BuCF55CFSnBu3), (Z)-1,2-difluoro-3-methyl-1-(tributyl-
stannyl)-1-pentene (sec-BuCF55CFSnBu3), (Z)-1,2-difluoro-3,3-
dimethyl-1-(tributylstannyl)-1-butene (tert-BuCF55CFSnBu3), and
(Z)-1,2-difluoro-1-(tributylstannyl)styrene (PhCF55CFSnBu3) were
prepared by the literature procedure [19].
NMR:
2H), 0.96 (t, JHH = 7.3 Hz, 3H); 13C NMR:
1JCF = 254.5 Hz, 2JCF = 56.1 Hz), 145.2 (dd, 1JCF = 224.0 Hz,
d 7.68(AB pattern, 4H), 2.58 (m, 2H), 1.62 (m, 2H), 1.42 (m,
3
d
155.4 (dd,
2
3
2JCF = 43.3 Hz), 134.1 (dd, JCF = 25.0 Hz, JCF = 6.7 Hz), 132.1 (d,
3
4
3JCF = 2.4 Hz), 125.2 (dd, JCF = 10.4 Hz, JCF = 7.9 Hz), 118.5 (s),
111.4 (d, 5JCF = 3.1 Hz), 27.71 (s), 27.3 (d, 2JCF = 22.6 Hz), 21.99 (s),
13.58 (s). GC–MS, m/z (relative intensity): 221 (M+, 47), 178
(M+ÀC3H7, 100), 165 (M+ÀC4H8, 69). FTIR: 2231.21 (CN), 1695.32
(C55C), 1609.16 (Ar)cmÀ1. HRMS: calcd for C13H13NF2, 221.1016;
obsvd 221.1034.
4.3. General procedure for the palladium (0) catalyzed coupling
reactions of (Z)-RCF55CFSnBu3 with aryl iodides
4.3.1. Reaction of (Z)-CH3CF55CFSnBu3 with 3-iodonitrobenzene
A 25 ml flask was charged with Pd(PPh3)4 (0.05 g, 0.043 mmol)
Cu(I)I (0.1 g, 0.52 mmol), 3-iodonitrobenzene (0.25 g, 1.0 mmol)
and dry DMF (5 ml). Then (Z)-CH3CF55CFSnBu3 (0.45 g, 1.2 mmol)
was added at RT with stirring. The reaction mixture was stirred for
10 h at RT. Complete disappearance of the vinyl stannane was
confirmed by 19F NMR analysis of the reaction mixture. The
reaction mixture was then diluted with ether (100 ml) and washed
with aqueous KF solution (15%, 50 ml). The ethereal layer was
separated, dried over anhydrous MgSO4 and concentrated. The
residue was chomatographed on a silica gel column using a
mixture of ethyl acetate and hexane (1:20) as eluent to afford
0.17 g (85%) of (E)-1,2-difluoro-1-(3-nitrophenyl)-propene as
4.3.4. Reaction of (Z)-n-BuCF55CFSnBu3 with 3-iodonitrobenzene
Similar to 4.3.1, reaction of (Z)-n-BuCF-CFSnBu3 (0.49 g,
1.2 mmol) with 3-iodonitrobenzene (0.25 g, 1.0 mmol) in the
presence of Pd(PPh3)4 (0.05 g, 0.043 mmol), Cu(I)I (0.10 g,
0.52 mmol) in dry DMF (5 ml) at RT for 10 h gave 0.21 g (87%)
of (E)-1,2-difluoro-1-(3-nitrophenyl)-1-hexene as a yellow oil
(after chromatography) using a mixture of ethyl acetate and
hexane (1:20) as the eluent. 19F NMR:
d
À141.3 (dt, 3JFF = 122.7 Hz,
3JHF = 24.1 Hz, 1F), À160.7 (dt, 3JFF = 122.7 Hz, 4JHF = 5.7 Hz, 1F); 1H
NMR:
d
8.45 (t, 4JHH = 1.8 Hz, 1H), 8.15 (dm, 3JHH = 7.4 Hz, 1H), 7.9
(dd, 2JHH = 7.9 Hz, 3JHH = 0.9 Hz, 1H), 7.57 (t, 3JHH = 8.1 Hz, 1H), 2.60
(m, 2H), 1.65 (m, 2H), 1.44 (m, 2H), 0.97 (t, 3JHH = 7.3 Hz, 3H); 13
C
1
2
NMR:
d 154.8 (dd, JCF = 252.7 Hz, JCF = 55.5 Hz), 148.4 (s), 144.9
1
2
2
yellow crystals, mp 52–53 8C. 19F NMR:
d
À134.5 (dq,
(dd, JCF = 224.0 Hz, JCF = 44.0 Hz), 131.6 (dd, JCF = 25.7 Hz,
3
3
3
4
3JFF = 123.3 Hz, JHF = 18.5 Hz, 1F), À160.0 (dq, JFF = 123.3 Hz,
3JCF = 6.1 Hz), 130.5 (dd, JCF = 9.8 Hz, JCF = 7.3 Hz), 129.4 (d,
4JHF = 5.8 Hz, 1F). 1H NMR:
d
8.42 (t, JHH = 1.9 Hz, 1H), 8.15
4JCF = 2.5 Hz), 122.7 (d, JCF = 1.8 Hz), 119.9 (dd, JCF = 9.8 Hz,
4
5
3
3
4
4
2
(ddd, JHH = 8.2 Hz, JHH = 2.2 Hz, JHH = 1.0 Hz, 1H), 7.90 (dt,
4JCF = 8.6 Hz), 27.75 (s), 27.16 (d, JCF = 23.2 Hz), 22.03 (s), 13.61
3JHH = 8.2 Hz, JHH = 1.0 Hz, 1H), 7.57 (t, JHH = 8.2 Hz, 1H), 2.25
(s). GC–MS, m/z (relative intensity): 241 (M+, 29), 198 (M+ÀC3H7,
4
3
(dd, JHF = 18.0 Hz, JHF = 5.2 Hz, 3H); 13C NMR:
d 151.4 (dd,
18), 185 (M+ÀC4H8, 57), 151 (100). FTIR: 1699.93 (C55C), 1534.86
3
4
1JCF = 250.3 Hz, 2JCF = 56.8 Hz), 148.3 (s), 145.0 (dd, 1JCF = 224.0 Hz,
(NO2), 1350.77 (NO2) cmÀ1
241.0914, obsvd 241.0898.
. HRMS: calcd for C12H13NF2O2,
2JCF = 42.7 Hz), 131.4 (dd, JCF = 26.2 Hz, JCF = 6.7 Hz), 130.4 (dd,
2
3
3JCF = 9.8 Hz, JCF = 7.3 Hz), 129.4 (d, JCF = 2.4 Hz), 122.7 (d,
4
4
5JCF = 1.8 Hz), 119.7 (dd, JCF = 9.8 Hz, JCF = 8.5 Hz), 13.59 (d,
4.3.5. Reaction of (Z)-sec-BuCF55CFSnBu3 with 3-iodonitrobenzene
Similar to 4.3.1, reaction of sec-BuCF55CFSnBu3 (0.49 g, 1.2 mmol)
with 3-iodonitrobenzene (0.25 g, 1.0 mmol) in the presence of
Pd(PPh3)4 (0.05 g, 0.043 mmol) and Cu(I)I (0.10 g, 0.52 mmol) in dry
DMF (5 ml) at RT for 10 h gave 0.20 g (83%) of (E)-1,2-difluoro-3-
methyl-1-(3-nitrophenyl)-1-pentene as a colorless oil (after chro-
4
5
2JCF = 24.4 Hz). GC–MS, m/z (relative intensity): 199 (M+, 100),
183 (3), 133 (91). FTIR: 1709.55 (C55C), 1577.42 (NO2) cmÀ1
;
HRMS: calcd for C9H7NF2O2, 199.0445; obsvd 199.0431.
4.3.2. Reaction of (Z)-CH3CF55CFSnBu3 with 1-iodonaphthalene
Similar to 4.3.1, reaction of (Z)-CH3CF55CFSnBu3 (0.92 g,
2.5 mmol) with 1-iodonaphthalene (0.51 g, 2.0 mmol) in the
presence of Pd(PPh3)4 (0.10 g, 0.087 mmol) and Cu(I)I (0.19 g,
matography) using ethyl acetate and hexane (1:20) as the eluent. 19
F
NMR:
d
À154.2 (dd, 3JFF = 122.1 Hz, 3JHF = 33.1 Hz, 1F), À161.4 (dd,
4
4
3JFF = 122.1 Hz, JHF = 5.1 Hz, 1F); 1H NMR:
d 8.47 (t, JHH = 1.9 Hz,

L. Lu, D.J. Burton / Journal of Fluorine Chemistry 143 (2012) 94–98
97
1H), 8.16 (m. 1H), 7.93 (m, 1H), 7.58 (t, 3JHH = 8.1 Hz, 1H), 2.93 (m,
1H), 1.60 (m, 2H), 1.23 (d, JHH = 6.9 Hz, 3H), 0.97 (t, JHH = 7.4 Hz,
1704.25 (C55C), 1535.91 (NO2), 1353.10 (NO2) cmÀ1. HRMS: calcd
for C12H13NF2O2, 241.0914, obsvd 241.0925.
3
3
3H); 13C NMR:
d
157.2(dd, 1JCF = 255.4 Hz, 2JCF = 53.4 Hz), 148.3 (m),
1
2
2
144.5 (dd, JCF = 223.1 Hz, JCF = 43.9 Hz), 131.7 (dd, JCF = 26.3 Hz,
4.3.9. Reaction of (Z)-PhCF55CFSnBu3 with 4-iodoacetophenone
Similar to 4.3.1, reaction of (Z)-PhCF55CFSnBu3 (0.52 g,
1.21 mmol) with 4-iodoacetophenone (0.25 g, 1.0 mmol) in the
presence of Pd(PPh3)4 (0.5 g, 0.043 mmol) and Cu(I)I (0.10 g,
0.52 mmol) in dry DMF (5 ml) at RT for 10 h gave 0.22 g (85%) of
(E)-1,2-difluoro-2-phenyl-1-(p-acetylphenyl)-ethene, mp = 128–
129 8C, as colorless crystals (after chromatography) using a mixture
3JCF = 6.4 Hz), 130.6 (dd, JCF = 9.8 Hz, JCF = 7.0 Hz), 129.4 (d,
3
4
4JCF = 2.5 Hz), 122.7 (d, JCF = 2.1 Hz), 120.0 (dd, JCF = 10.1 Hz,
5
3
4JCF = 8.2 Hz), 33.87 (d, JCF = 22.3 Hz), 26.22 (d, JCF = 2.1 Hz),
2
3
3,4
16.68 (t,
J
CF
= 1.5 Hz), 11.84 (s). GC–MS, m/z (relative intensity):
241 (M+, 31), 212 (M+ÀC2H5, 100). FTIR: 1695.44 (C55C), 1537.84
(NO2), 1351.68 (NO2) cmÀ1
241.0914; obsvd 241.0892.
, HRMS: calcd for C12H13NF2O2,
of ethyl acetate and hexane (1:20) as the eluent. 19F NMR:
d
À148.2
(d, 3JFF = 119.5 Hz,1F), À153.5(d,3JFF = 119.5 Hz, 1F);1HNMR:
d
7.98
3
4.3.6. Reaction of (Z)-sec-BuCF55CFSnBu3 with 4-iodobenzonitrile
Similar to 4.3.1, reaction of (Z)-sec-BuCF55CFSnBu3 (0.49 g,
1.2 mmol) with 4-iodobenzonitrile (0.23 g, 1.0 mmol) in the
presence of Pd(PPh3)4 (0.05 g, 0043 mmol), and Cu(I)I (0.10 g,
0.52 mmol) in dry DMF (5 ml) at RT for 10 h gave 0.19 g (86%) of
(E)-1,2-difluoro-3-methyl-1-(4-cyanophenyl)-1-pentene as a yel-
low oil (after chromatography) using a mixture of ethyl acetate and
(d, JHH = 8.4 Hz, 2H), 7.80 (m, 4H), 7.43 (m, 3H), 2.58 (s, 3H); 13C
1
2
NMR:
d 197.1 (s), 150.1 (dd, JCF = 183.1 Hz, JCF = 47.3 Hz), 146.9
(dd, 1JCF = 178.9 Hz, 2JCF = 47.6 Hz), 136.6(d, 5JCF = 2.5 Hz), 134.4 (dd,
2JCF = 22.1 Hz, JCF = 6.4 Hz), 129.8 (d, JCF = 6.1 Hz), 129.5 (d,
3
3
4JCF = 1.9 Hz), 128.5 (d, JCF = 2.4 Hz), 128.3 (d, JCF = 2.4 Hz), 126.0
(dd,2JCF = 9.4 Hz, 3JCF = 8.2 Hz), 125.6(dd, 3JCF = 9.2 Hz, 4JCF = 7.9 Hz),
26.48 (s). GC–MS, m/z (relative intensity): 258 (M+, 61), 243
3
3
hexane (1:20) as the eluent. 19F NMR:
d
À152.2 (dd, 3JFF = 120.8 Hz,
(M+ÀCH3,100), 214 (38). FTIR: 1689.85 (C55C), 1606.21 (Ar), cmÀ1
.
3
4
3JHF = 33.01 Hz, 1F), À161.9 (dd, JFF = 120.8 Hz, JHF = 5.1 Hz, 1F);
HRMS: calcd for C16H12F2O, 258.0856; obsvd 258.0859.
1H NMR:
d 7.70 (AB Pattern, 4H), 2.92 (m, 1H), 1.59 (m, 2H), 1.22
(d, 3JHH = 7.0 Hz, 3H), 0.96(t, 3JHH = 7.4 Hz,3H). 13CNMR:
1JCF = 257.0 Hz, 2JCF = 54.0 Hz), 144.8 (dd, 1JCF = 223.4 Hz,
d
157.7(dd,
4.3.10. Reaction of (Z)-PhCF55CFSnBu3 with 4-iodonitrobenzene
Similar to 4.3.1, reaction of (Z)-PhCF55CFSnBu3 (0.52 g,
1.21 mmol) with 4-iodonitrobenzene (0.25 g, 1.0 mmol) in the
presence of Pd(PPh3)4 (0.05 g, 0043 mmol) and Cu(I)I (0.10 g,
0.52 mmol) in dry DMF (5 ml) at RT for 10 h gave 0.24 g (92%) of
(E)-1,2-difluoro-2-phenyl-1-(4-nitrophenyl)ethene as yellow crys-
tals, mp = 121–123 8C (after chromatography) using ethyl acetate
2
3
2JCF = 43.6 Hz), 134.1 (dd, JCF = 25.3 Hz, JCF = 6.1 Hz), 132.0 (d,
3JCF = 2.4 Hz), 125.3 (dd, 3JCF = 10.0 Hz, 4JCF = 7.6 Hz), 118.4 (s), 111.4
(d, 5JCF = 3.1 Hz), 33.86 (2JCF = 22.3 Hz), 26.15 (d, 3JCF = 2.1 Hz), 16.56
(s), 11.75 (s). GC–MS, m/z (relative intensity): 221 (M+, 23), 192
(M+ÀC2H5, 100). FTIR: 2230.76 (CN), 1690.54 (C55C), 1608.45
(Ar) cmÀ1. HRMS: calcd for C13H13NF2: 221.1026; obsvd 221.0990.
and hexane (1:20) as the eluent. 19F NMR:
d
À145.7 (d,
3
3JFF = 119.6 Hz, 1F), À153.8 (d, JFF = 119.6 Hz, 1F); 1H NMR:
d
3
3
4.3.7. Reaction of (Z)-sec-BuCF55CFSnBu3 with 4-iodonitrobenzene
Similar to 4.3.1, reaction of (Z)-sec-BuCF55CFSnBu3 (0.49 g,
1.2 mmol) with 4-iodonitrobenzene (0.25 g, 1.0 mmol) in the
presence of Pd(PPh3)4 (0.05 g, 0.043 mmol) and Cu(I)I (0.10 g,
0.52 mmol) in dry DMF (5 ml) at RT for 10 h give 0.21 g (87%) of (E)-
1,2-difluoro-3-methyl-1-(4-nitrophenyl)-1-pentene as a yellow oil
(after chromatography) using a mixture of ethyl acetate and
8.26 (d, JHH = 9.0 Hz, 2H), 7.89 (d, JHH = 9.0 Hz, 2H), 7.77 (d,
3JHH = 7.8 Hz, 2H), 7.46 (m, 3H); 13C NMR:
d 150.7 (dd,
1JCF = 242.9 Hz, JCF = 47.0 Hz), 147.2 (d, JCF = 2.8 Hz), 146.4 (dd,
2
5
1JCF = 235.9 Hz,
2JCF = 47.3 Hz),
136.2
(dd,
2JCF = 24.0 Hz,
2
3JCF = 6.7 Hz), 130.0 (d, JCF = 2.1 Hz), 129.2 (dd, JCF = 24.1 Hz,
4
3JCF = 6.7 Hz), 128.6 (d, JCF = 2.1 Hz), 126.3 (dd, JCF = 8.2 Hz,
4
3
4JCF = 1.2 Hz), 126.1 (dd, JCF = 8.2 Hz, JCF = 2.7 Hz), 123.7 (d,
5JCF = 2.4 Hz). GC–MS, m/z (relative intensity): 261 (M+, 100),
231 (19), 214 (70). FTIR: 1651.67 (C55C), 1599.07 (Ar), 1525.79
3
4
hexane (1:20) as the eluent. 19F NMR:
d
À150.9 (dd, 3JFF = 120.8 Hz,
3
4
3JHF = 33.1 Hz, 1F),
d
À161.1 (dd, JFF = 120.8 Hz, JHF = 5.1 Hz, 1F).
1H NMR:
d
8.25 (d, 3JHH = 9.0 Hz, 2H), 7.78 (dm, 3JHH = 9.0 Hz, 2H),
(NO2), 1344.51 (NO2) cmÀ1
261.0601; obsvd 261.0619.
. HRMS: calcd for C14H9NF2O2,
3
2.94 (m, 1H), 1.60 (m, 2H), 1.23 (d, JHH = 7.0 Hz, 3H), 0.97 (t,
3JHH = 7.5 Hz, 3H); 13C NMR:
d 158.3 (dd, JCF = 258.1 Hz,
1
5
1
2JCF = 53.7 Hz), 146.9 (d, JCF = 3.1 Hz), 144.8 (dd, JCF = 223.4 Hz,
4.3.11. Reaction of (Z)-tert-BuCF55CFSnBu3 with 4-iodonitrobenzene
Similar to 4.3.1, reaction of (Z)-tert-BuCF55CFSnBu3 (0.49 g,
1.2 mmol) with 4-iodonitrobenzene (0.25 g, 1.0 mmol) in the
presence of Pd(PPh3)4 (0.05 g, 0.043 mmol), and Cu(I)I (0.10 g,
0.52 mmol) in dry DMF (5 ml) at RT for 10 h gave 0.22 g (92%) of
colorless crystals (after chromatography), mp = 63–64 8C, using a
mixture of ethyl acetate and hexane (1:20) as the eluent. 19F NMR:
2
3
2JCF = 43.7 Hz), 136.0 (dd, JCF = 25.0 Hz), JCF = 6.4 Hz), 125.6 (dd,
4
4
3JCF = 10.3 Hz, JCF = 7.6 Hz), 123.6 (d, JCF = 2.4 Hz), 34.01 (d,
3
2JCF = 2.0 Hz), 26.25 (d, JCF = 2.2 Hz), 16.64 (s), 11.84 (s). GC–MS,
m/z (relative intensity): 241 (M+, 50), 212 (M+ÀC2H5, 100). FTIR:
1687.32 (C55C), 1600.12 (Ar), 1524.29 (NO2) cmÀ1. HRMS: calcd for
C12H13NF2O2, 241.0914 obsvd 241.0918.
3
3
d
À141.3 (d, JFF = 120.4 Hz, 1F), À157.7 (d, JFF = 120.4 Hz, 1F; 1H
4/5
4/5
4.3.8. Reaction of (Z)-tert-BuCF55CFSnBu3 with 2-iodonitrobenzene
Similar to 4.3.1, reaction of (Z)-tert-BuCF55CFSnBu3 (0.49 g,
1.2 mmol) with 2-iodonitrobenzene (0.25 g, 1.0 mmol) in the
presence of Pd(PPh3)4 (0.05 g, 0.043 mmol) and Cu(I)I (0.10 g,
0.52 mmol) in dry DMF (5 ml) at RT for 10 h gave 0.20 (82%) of (E)-
1,2-difluoro-3,3-dimethyl-1-butene as a yellow oil (after chroma-
NMR:
d
8.30 (d,
1.35 (m, 9H); 13C NMR:
146.9 (d, JCF = 2.4 Hz), 145.2 (dd, JCF = 229.3 Hz, JCF = 50.0 Hz),
J
HF
= 9.2 Hz, 2H), 7.6 (dm,
160.3 (dd, 1JCF = 256.3 Hz, 2JCF = 48.8 Hz),
J
HF
= 9.2 Hz, 2H),
d
5
1
2
2
3
3
136.9 (dd, JCF = 25.0 Hz, JCF = 6.7 Hz), 126.1 (dd, JCF = 11.0 Hz,
4JCF = 8.0 Hz), 123.5 (d, JCF = 1.8 Hz), 35.81 (dd, JCF = 21.4 Hz,
4
2
3JCF = 3.7 Hz), 27.41 (t,
J
CF
= 4.5 Hz). GC–MS, m/z (relative
3/4
tography) using a mixture of ethyl acetate and hexane (1:20) as the
intensity): 241 (M+, 36), 226 (M+ÀCH3, 100). FTIR: 1673.99
3
eluent. 19F NMR:
d
À147.1 (d, JFF = 132.2 Hz, 1F), À148.0 (d,
(C55C), 1524.16 (NO2), 1342.06 (NO2) cmÀ1. HRMS: calcd for
3JFF = 132.2 Hz, 1F); 1H NMR:
1H), 7.58 m (3H), 1.31 (t, 4/5JCF = 2.0 Hz 9H); 13C NMR:
1JCF = 227.7 Hz, 2JCF = 26.9 Hz), 147.6 (s), 143.5 (dd, 1JCF = 212.4 Hz,
d
7.95 (dd, 3JHH = 8.0 Hz, 4JHH = 0.6 Hz,
C12H13NF2O2, 241.0914; obsvd 241.0889.
d
157.0 (dd,
4.3.12. Reaction of (Z)-PhCF55CFSnBu3 with 4-iodobenzonitrile
Similar to 4.3.1, reaction of (Z)-PhCF55CFSnBu3 (0.52 g,
1.21 mmol) with 4-iodobenzonitrile (0.23 g, 1.0 mmol) in the
presence of Pd(PPh3)4 (0.05 g, 0.043 mmol) and Cu(I)I (0.10 g,
0.52 mmol) in dry DMF (5 ml) at RT for 10 h gave 0.21 g (87%) of
2JCF = 36.7 Hz), 132.7 (s), 131.4 (dd, JCF = 4.3 Hz, JCF = 3.0 Hz),
130.2 (s), 125.0 (dd, JCF = 23.8 Hz, JCF = 1.8 Hz), 124.4 (s), 34.90
(dd, JCF = 20.7 Hz, JCF = 3.0 Hz), 27.06 (t,
m/z (relative intensity): 241 (M+, 1), 220 (2), 109 (100). FTIR:
3
4
2
3
2
3
3,4
J
CF
= 4.3 Hz). GC–MS,

98
L. Lu, D.J. Burton / Journal of Fluorine Chemistry 143 (2012) 94–98
(f) G. Resnati, V. Soloshnok, Fluoroorganic Chemistry, Synthetic Challenges and
Biomedical Rewards, Tetrahedron Symposia-in-Print, No. 58, Tetrahedron 52
(1996) 1;
(g) R. Filler, Y. Kobayashi, L.M. Yagupolski (Eds.), Organofluorine Compounds in
Medical and Biomedical Applications, Elsevier, Amsterdam, 1993;
(h) M. Hudlisky, A.E. Pavlath (Eds.), Chemistry of Organic Fluorine Compounds,
American Chemical Society, 1996, No. 187.
(E)-1,2-difluoro-3-phenyl-1-(4-cyanophenyl)-ethene as white
crystals, m.p. = 98–100 8C (after chromatography) using ethyl
acetate and hexane (1:20) as the eluent. 19F NMR:
d
À146.7 (d,
3JFF = 119.5 Hz, 1F), À154.5 (d, 3JFF = 119.5 Hz, 1F); 1H NMR:
d
7.84
3
3
4
(d, JHH = 8.5 Hz, 2H), 7.76 (dd, JHH = 8.5 Hz, JHH = 1.5 Hz, 2H),
3
7.71 (d, JHH = 8.5 Hz, 2H), 7.46 (m, 3H); 13C NMR:
d 150.4 (dd,
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995.
1JCF = 241.7 Hz, 2JCF = 47.0 Hz), 146.5 (dd, 1JCF = 235.6 Hz,
2JCF = 47.6 Hz), 134.4 (dd, JCF = 24.4 Hz, JCF = 6.4 Hz), 132.2 (d,
2
3
4JCF = 2.4 Hz), 129.9 (d, JCF = 1.8 Hz), 129.3 (dd, JCF = 24.1 Hz,
5
2
4
3
3JCF = 6.4 Hz), 128.6 (d, JCF = 2.2 Hz), 126.6 (dd, JCF = 9.4 Hz,
[6] Q. Liu, D.J. Burton, J. Fluorine Chem. 130 (2009) 922–925.
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[12] E.J. Blumenthal, D.J. Burton, Israel J. Chem. 39 (1999) 109–115.
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161.
4JCF = 8.2 Hz), 125.9 (dd, JCF = 10.9 Hz, JCF = 8.2 Hz), 118.4 (s),
112.0 (d, J = 3.0 Hz). GC–MS, m/z (relative intensity): 241 (M+, 100).
FTIR: 2231.04 (CN), 1650.43 (C55C), 1606.97 (Ar) cmÀ1. HRMS:
calcd for C15H9NF2, 241.0703; obsvd 241.0716.
3
4
References
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