(E)-1,2-Difluoro-1-iodo-2-trialkylsilanes - A useful synthon for the addition of the [IFCCF] unit to activated electrophiles

Article abstract of DOI:10.1016/j.jfluchem.2011.07.013

Fluoride ion catalyzed reaction of (E)-IFCCFSiR₃ with activated aromatic aldehydes and ketones and activated perfluoroaromatics, such as pentafluoropyridine and perfluorotoluenes, transfers the [IFCCF] unit to the activated electrophiles to ste

Full text of DOI:10.1016/j.jfluchem.2011.07.013

Journal of Fluorine Chemistry 132 (2011) 940–944
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
(E)-1,2-Difluoro-1-iodo-2-trialkylsilanes—A useful synthon for the addition of the
[IFC55CF] unit to activated electrophiles
*
Ya-Bo He, Ba V. Nguyen, 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:
Fluoride ion catalyzed reaction of (E)-IFC55CFSiR3 with activated aromatic aldehydes and ketones and
activated perfluoroaromatics, such as pentafluoropyridine and perfluorotoluenes, transfers the [IFC55CF]
unit to the activated electrophiles to stereospecifically provide (E)-1,2-difluoro-1-iodosubstituted
derivatives. Aluminum chloride catalyzed reaction of (E)-1,2-difluoro-1-iodo-2-trialkylsilanes with alkyl
or aryl acyl halides gives the corresponding (E)-1,2-difluoro-1-iodoketones stereospecifically in
excellent yield. The vinyl iodide product formed via this methodology could be coupled (with Pd(0))
catalysis to provide an entry to a polyfunctionalized derivative.
Received 23 June 2011
Accepted 14 July 2011
Available online 23 July 2011
Keywords:
Fluorinated vinylsilanes
Fluoride ion mediated reactions
[IFC5CF] addition reactions
Perfluoroaromatics
ß 2011 Elsevier B.V. All rights reserved.
AlCl3 catalysis
1. Introduction
C6H5
CF3
ºC
100 h
F
F
CF3C(O)C6H5 + Me3SiCF=CF2 + 20% CsF
The development of fluorine-containing synthons has played a
significant role in the preparation of organofluorine compounds
and has been
OSiMe3
F
no solvent
1
a valuable addition to the toolbox of the
64%
organofluorine chemist [1]. Trialkylsilyl derivatives have been
an important component in this methodology. Fluoride ion
mediated processes of compounds, such as CF3SiR3, have been
key to the introduction of trifluoromethyl groups into a variety of
non-fluorinated functionalized compounds [2]. In contrast to the
use of perfluoroalkylsilanes as synthons, the use of perfluorovi-
nylsilane synthons has received only limited attention. The
Normant group first reported the fluoride ion catalyzed reaction
of (Z)-1,2-difluorotrimethylsilylhexene with pivaldehyde (no yield
reported) as illustrated in Eq. (1) [3].
(2)
Conditions utilized in this work dictated whether silylated
trifluoroallylic alcohols were obtained or whether olefinic products
were obtained. More recently, Petrov and Larichev reported similar
fluoride ion catalyzed addition reactions of (E)-trimethyl(perfluoro-
1-propenyl)silane as an agent to transfer the perfluoro-1-propenyl
group stereospecifically to aldehydes and ketones, Eq. (3) [6].
F
F
F3C
F
SiMe3
CsF
THF, RT
+
CH3CHO
(3)
OSiMe3, 50%
F3C
F
Bu
F
F
KF, DMSO
ºC
Bu
F
F
+ (CH3)3CCHO
CH(OH)But
SiMe3
Similar reactions with benzaldehyde gave 66% of the silylated
addition adduct.
(1)
Another vinylsilane synthon of interest is (E)-1,2-difluoro-1-iodo-
2-triethylsilylethene, 2, which is readily synthesized by metallation/
iodination of (Z)-1,2-difluoro-2-triethylsilylethene, Eq. (4) [7].
Subsequently, Yagupolskii studied the fluoride ion catalyzed
addition of trialkyl(trifluorovinyl)silanes to aldehydes and ketones,
as shown in Eq. (2) [4,5].
1) THF/Et2O
I
F
H
F
F
+
BuLi
(4)
ºC
F
SiEt3
SiEt3
2) I2
2
* Corresponding author. Tel.: +1 319 335 1363; fax: +1 319 335 1270.
E-mail addresses: donald-burton@uiowa.edu, mburton105@gmail.com
(D.J. Burton).
2 readily undergoes palladium catalyzed coupling reactions
with organozinc reagents [7]. The corresponding (Z)-1,2-difluoro-
0022-1139/$ – see front matter ß 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2011.07.013

Y.-B. He et al. / Journal of Fluorine Chemistry 132 (2011) 940–944
941
1-iodo-2-triethylsilylethene can be prepared by iodination of (Z)-
1,2-difluoro-1-tributylstannyl-2-triethylsilylethene as illustrated
in Eq. (5) [8].
Trifluoroacetophenone, under similar conditions, gave a 60%
yield of the addition product. Hiyama has reported that the use of
TASF is remarkably efficient for stabilizing carbenoid anions and
effecting aldehyde addition reactions [13]. However, when we
attempted the reaction of octanal with 2 and TASF, the addition
product yield improved slightly. Even with 100 mol% TASF, the
addition product/(Z)-HFC55CFI ratio was 35:65. Isolation of the
addition was complicated; a mixture of the addition product and
the aldol condensation product was obtained by column chroma-
tography. Thus, we pursued the aliphatic aldehydes no further.
F
F
I2
DMF
RT/1 h
F
F
I
(5)
SnBu3
Et3Si
Et3Si
3
2. Results and discussion
2.1. Fluoride ion catalyzed reaction of 2 with aldehydes and ketones
2.2. Reaction of 2 with acyl chloride (as the electrophile)
As demonstrated in the previously cited Refs. [2–6], fluoride ion
readily attacks the trialkylsilyl group with concomitant transfer of
the fluorinated vinyl group to an in situ electrophile, such as an
aldehyde or ketone. If 2 could be utilized as the vinylsilane
component, there is an additional feature present that is not readily
available in the F2C55CFÀ anion or the cis-CF3CF55CF anion – namely,
a good leaving group (ÀI) at the beta position. Consequently,
elimination of the iodide from the anion [IFC55CF]À, is more likely
than in the previously described reagents [9]. Secondly, the
[IFC55CF]À anion can not only attack the electrophilic carbonyl
carbon of the aldehyde or ketone, but could also abstract an iodine
from 2 to produce (E)-IFC55CFI. Thus, our initial focus concentrated
on successful capture of the [IFC55CF] moiety and features in the
carbonyl component that would promote success in the prepara-
tion of the vinyliodide addition product.
Normant reported that difluorovinylsilanes could be reacted
with an acyl halide, such as CH3C(O)Cl, in the presence of AlCl3 to
yield
a,b-unsaturated ketones [3]. Thus, we considered the acyl
group as a potentially useful electrophile for transfer of the
[ICF55CF] group. Two model acyl halides, CH3CH2C(O)Cl and
C6H5C(O)Cl were selected to evaluate this methodology.
Thus, we added benzoyl chloride to a suspension of AlCl3 in
CH2Cl2 at 0 8C, followed by addition of 2 at À40 8C to À30 8C. The
reaction was allowed to slowly warm to room temperature. The
reaction proceeded cleanly as almost no other by-products formed.
After quenching the reaction mixture with water, extraction with
ether, drying over MgSO4, silica gel chromatography (hexane/ethyl
acetate = 10/1) gave the product in 79% isolated yield, Eq. (8).
O
When aliphatic aldehydes, such as C6H5CH2CHO and n-octanal
were reacted with 2 and KF in DMSO at room temperature for
several hours, the main product was (Z)-HFC55CFI [10] (90–95%)
and the minor product was the expected addition product (5–10%).
Traces of (E)-IFC55CFI were also detected by NMR [12]. To increase
the electrophilicity of the carbonyl group and to avoid abstraction
of [H+] from the aldehyde, we focused on two aromatic aldehydes
and one activated ketone containing an electron-withdrawing
group. Thus, when p-trifluoromethylbenzaldehyde was reacted
with 2 in the presence of dry KF, the addition product was formed
in good yield as illustrated in Eq. (6).
AlCl3/CH2Cl2
, 79%
2
+
C(O)Cl
C
F
F
I
(8)
ºC to RT
12 h
7
Similarly, propionyl chloride gave the
a,b-unsaturated ketone,
8, in 81% yield. The electrophilic substitution reaction proceeded
with retention of stereochemistry. Mechanistically, the reaction
proceeds quite differently than the KF reaction of 2 with an
activated aldehyde or ketone. Similar to the mechanistic proposal
of Normant [3], we propose addition of an acyl cation to 2, followed
by trans-elimination (after rotation) to produce the trans
stereochemistry observed in the final product; cf. Scheme 1.
OSiEt3
CH
KF
I
F
F3C
CHO
F3C
+
, 71%
DMSO
RT/5 h
F
I
F
SiEt3
F
2.3. KF catalyzed reaction of 2 with reactive perfluoroaromatics
4
(6)
Pentafluoropyridine has been shown to be an excellent
nucleophilic trapping agent for the unstable halodifluoromethide
ion [14]. Thus, we attempted to trap the [IFC55CF]À with
pentafluoropyridine. As expected, the trapping reaction was fast.
When 2 was reacted with pentafluoropyridine and KF in DMSO
at RT, 19F NMR analysis of the reaction mixture after 10 min
showed that all of 2 had been completely consumed. The results of
Note that similar to Refs. [4–6], the siloxy derivative is initially
formed (when the reaction is quenched with water). This protecting
group is useful for further functionalization of the addition product
(cf. Section 4.8). Hydrolysis to the corresponding alcohol with dilute
3 N HCl is slow. When the reaction mixture was quenched with
water, followed by extraction with ether and water, a 71% yield of 4
was isolated. If the reaction mixture was quenched with dilute 3 N
HCl followed by extraction with ether and water, a mixture of 4 and
the corresponding alcohol, 5, were isolated (cf. Section 4). If the
reaction mixture was treated further with 3 N HCl at RT for 2 h, the
alcohol was the sole product in 70% yield. When p-chlorobenzalde-
hyde was reacted with (E)-Me3SiCF55CFI under similar conditions,
the addition product, 6, was obtained in 75% yield, Eq. (7).
_
+
C6H5C(O)Cl
+
AlCl3
[C6H5C(O)
+
AlCl4
]
2
O
F
C-C6H5
I
O
I
+
+
F
F
SiEt3
CC6H5
F
SiEt3
OSiMe3
Me3Si
F
F
I
KF, DMSO
RT/3 h
AlCl3-Cl
Cl
CH
+ Cl
CHO
, 75%
F
I
I
F
F
C6H5
6
F
O
(7)
Scheme 1. Mechanism of AlCl3 acylation of an acyl chloride with 2.

942
Y.-B. He et al. / Journal of Fluorine Chemistry 132 (2011) 940–944
2.4. Extension of methodology to polyfunctionalized derivatives
F
_
F
I
-FSiEt3
-
F
I
N
2
+ F
One of the interests in attempting to trap the [IFC55CF]À anion
via fluoride mediation of 2 with reactive electrophiles was the
potential utility of the addition product to be easily functionalized
further to provide access to polyfunctional derivatives. The vinyl
iodide product could be functionalized via two potentially known
methods: (1) the vinyl iodide could be directly coupled with other
substrates, or (2) the vinyl iodide could be converted in situ to a
vinylzinc or a vinylcopper reagent that could be elaborated further
by known methodology [15,16]. As proof of principle of this
expectation, we investigated the functionalization of the addition
product of 2 with trifluoroacetophenone, which was obtained in
71% yield (cf. Section 4.2). Thus, 4 was reacted (via Pd(0) catalysis)
with an acetylenic derivative [18] as illustrated in Eq. (11). The
overall yield of 14 via a two-step process was 63%.
F
-
F
F
F
I
N
-
9
F
Path B
_
F
Path A
F
-
F
F
+ IF
F
F
I
I
F
F
-
F
+
N
F
F
I
N
F
N
11
F
N
N
F
I
F
I
F
N
+
F
F
F
F
F
OSiEt3
N
F
F3C
CH
10
F
F
I
OH
10
+
N
F
C CH
Scheme 2. Mechanism of formation of 9, 10 and 11.
Pd(PPh3)2Cl2
Cu(I)I
this reaction are illustrated in Eq. (9).
NEt3
ºC
(11)
2.5 h
N
F
OSiEt3
CH
DMSO
10 min
F
I
F
I
F
I
2
+
+ KF
+
:
+
:
F
N
F3C
F
F
F
F
F
F
N
N
F
14
OH
10
34
9
34
11
32
(9)
89%
The ratio of the three products was determined by 19F NMR
analysis of the reaction mixture. 9 and 10 were isolated in yields of
26% and 23% respectively. 11 was identified by comparison of its
spectroscopic data to a known sample [8]. The products of this
reaction are rationalized by the mechanism outlined in Scheme 2.
The possibility of direct attack of FÀ on 9 (path B) was excluded
by the fact that treatment of 9 with perfluoropyridine and TASF did
not afford any 10.
TASF could also be used as the catalyst in this reaction. Thus,
when pentafluoropyridine, TASF and 2 were reacted at RT, the ratio
of 9:10:11 was 43:28:29; 29% isolated yield of 9 and 18% of 10.
The reaction of perfluorotoluene with 2 and KF in DMSO at RT
was slower than the reaction with pentafluoropyridine, but the
overall result was similar; cf. Eq. (10).
3. Conclusions
With fluoride ion catalysis, (E)-1,2-difluoro-1-iodotrialkylsi-
lanes have been demonstrated to stereospecifically transfer the
[ICF55CF] unit to an activated aldehyde, activated ketone,
acylchlorides, or reactive perfluoroaromatics, such as perfluor-
opyridine or perfluorotoluene. The addition product can be utilized
in further transformations to provide a simple two-step route to
polyfunctionalized products.
4. Experimental
4.1. General experimental procedures
All glassware were oven-dried before use. 19F NMR
(282.44 MHz), 1H NMR (300.17 MHz) and {1H} 13C NMR
(75.48 MHz) were recorded on an AC-300 spectrometer in CDCl3
solvent. The chemical shifts are reported in parts per million
downfield to the TMS internal standard for the 1H NMR and {1H}
13C NMR. The chemical shifts are reported in parts per million
upfield to the CFCl3 internal standard for 19F NMR. FTIR spectra
were recorded in CCl4 solutions and reported in wavenumbers
(cmÀ1). Low resolution GC–MS spectra were obtained at 70 eV in
the electron-impact mode on a TRIO-1-GC-MS instrument. All
reactions were carried out under an atmosphere of nitrogen.
Cu(I)Br was treated with aqueous HBr (48%), precipitated with
excess cold water, washed with water; acetone, and ether and
dried in vacuo. KF was dried at 250 8C in vacuo for 2 days. 2 was
prepared by Normant’s procedure [7,8]. (E)-IFC55CFSiMe3 was
prepared from the corresponding vinylsilane via our reported
CF3
F
F
F
I
I
F
I
DMSO
RT
+
+ 2 + KF
+
F
F
F
F
F
13
11
F
12
CF3
F3C
F3C
(10)
After 1 h and RT, 19F NMR analysis of the reaction mixture
indicated the ratio of 12:13:11 was 46:30:24. After an additional
2 h at RT, the reaction was complete and the ratio of 12:13:11 was
33:40:27. The isolated yields of 12 and 13 were 25% and 28%
respectively.
With the less reactive hexafluorobenzene, no substitution
product was obtained.

Y.-B. He et al. / Journal of Fluorine Chemistry 132 (2011) 940–944
943
procedure [17]. All other reagents were obtained from common
commercial sources.
suspension was added benzoyl chloride (252 mg, 1.8 mmol) at 0 8C
over a period of 25 min; then 456 mg (1.50 mmol) of 2 was added
at À30 to À40 8C within 10 min. The reaction mixture was stirred
at À40 8C to RT for 2 h and then at RT overnight. 19F NMR showed
that all the vinylsilane, 2, had been consumed. The reaction
mixture was quenched by the addition of water, then extracted
with ether, and dried over MgSO4. Column chromatography on
silica gel (hexane/ethyl acetate, 10/1) gave 350 mg (yield: 79%) of
4.2. Preparation of (Z)-1,2-difluoro-1-iodo-2(p-
trifluoromethylbenzyltriethylsiloxy) ethene, 4
A 2-neck flask equipped with a magnetic stir bar, rubber septum
and nitrogen inlet was charged with anhydrous KF (232 mg,
2.87 mmol) in anhydrous DMSO (2 ml). Then, p-trifluoromethyl-
benzaldehyde (500 mg, 2.87 mmol) and (E)-1,2-difluoro-1-iodo-2-
triethylsilylethene, 2 (700 mg, 2.30 mmol) were added via syringe.
After the reaction mixture was stirred at RT for 5 h, 19F NMR
analysis of the reaction mixture showed the addition product was
formed, accompanied by a small amount of the protonated
product, while all the starting vinylsilane had been consumed.
The reaction was quenched by the addition of diluted HCl (3 N),
extracted with ether, the ether extracts washed with dilute HCl
(3 N), and water, and the ether layer dried over MgSO4. Column
chromatography on silica gel (hexane/ethyl acetate, 9/1) gave a
7. 1H NMR:
d 7.81–7.78 (m, 2H), 7.52–7.54 (m, 1H), 7.47–7.42 (m,
3
2H); 19F NMR:
d
À96.6 (d, JFF = 148.0 Hz, 1F), À133.8 (d,
3JFF = 148.0 Hz, 1F); 13C NMR:
d 181.9 (dd, JCF = 27.0 Hz,
2
3JCF = 5.0 Hz), 151.6 (dd, JCF = 254.0 Hz, JCF = 32.0 Hz), 135.0 (d,
1
2
3JCF = 5.0 Hz), 133.9 (s), 129.0 (s), 128.5 (s), 113.8 (dd,
1JCF = 339.0 Hz, JCF = 67.0 Hz). GC–MS, m/z (relative intensity):
2
294 (M+, 17), 189 (M+ÀC6H5CO, 3.7), 167 (M+ÀI, 71), 127 (I+, 9), 105
(C6H5CO+, 98), 77 (C6H5+, 100). IR (cmÀ1): 1687 (m), 1677 (m),
1581 (m), 1500 (m), 1306 (vs), 1197 (s), 1175 (s).
4.5. Preparation of (Z)-1,2-difluoro-1-iodo-3-pentenone, 8
colorless oil (520 mg), 4, yield: 47% and a white solid (200 mg), 5,
3
yield: 24%. 4, 1H NMR:
d
7.57 (m, 4H), 5.88 (dd, JHF = 25 Hz,
Similar to Section 4.4, propionyl chloride (184 mg, 2.0 mmol),
AlCl3 (390 mg, 3.00 mmol), and 2 (456 mg, 1.50 mmol) in CH2Cl2
(3 ml) at À30 8C/RT for 3 h gave 300 mg of 8, yield: 81%, after the
3
3
4JHF = 4.0 Hz, 1H), 0.95 (t, JHH = 7.5 Hz, 9H), 0.67 (q, JHH = 7.5 Hz,
6H); 19F NMR:
d
À63.1 (s, 3F), À123.6 (d, JFF = 142.0 Hz, 1F),
3
À145.5 (dd, JFF = 142.0 Hz, JHF = 25.0 Hz, 1F); 13C NMR:
d
156.3
usual workup. 1H NMR:
d 2.70 (qdd, JHH = 7.0 Hz, JHF = 2.9 Hz,
3
3
3
4
(dd, 1JCF = 253.0 Hz, 2JCF = 40.4 Hz), 142.9 (s), 130.6 (q, 2JCF = 32 Hz),
5JHF = 1.5 Hz, 2H), 1.2 (t, JHH = 7.0 Hz, 3H); 19F NMR:
d
À94.3 (d,
3
3
1
126.5 (s), 125.5 (q, JCF = 3.5 Hz), 124.2 (q, JCF = 272.0 Hz), 99.21
3JFF = 145.0 Hz, 1F), À139.9 (d, 3JFF = 145.0 Hz, 1F); 13C NMR: 188.8
1
2
2
2
3
1
(dd, JCF = 314.0 Hz, JCF = 67.0 Hz), 66.8 (d, JCF = 23.0 Hz), 6.6 (s),
4.6 (s). GC–MS, m/z (relative intensity): 459 (1), 449 (1), 325 (6),
217 (100), 127 (4), 115 (7), 105 (65), 77 (72). IR (cmÀ1): 2959 (s),
(dd, JCF = 25.0 Hz, JCF = 6.0 Hz), 152.0 (dd, JCF = 248.0 Hz,
2JCF = 33.0 Hz), 115.5 (dd, JCF = 339.0 Hz, JCF = 69.0 Hz), 33.6 (d,
3JCF = 4.0 Hz), 6.97 (s). GC–MS, m/z (relative intensity): 246 (M+, 9),
217 (M+ÀEt, 17), 189 (M+ÀEtCO, 10), 127 (I+, 11), 119 (M+ÀI, 15),
57 (EtCO+, 100). IR (cm+1): 1720 (s), 1704 (s), 1616 (s), 1320 (s),
1264 (s), 1184 (vs), 1170 (vs), 2985 (m).
1
2
1324 (vs), 1169 (m), 1134 (vs). 5, mp 57–58 8C. 1H NMR:
d 7.6 (m,
4H), 5.9 (dm 3JHF = 24.0 Hz, 1H), 2.9 (d, 4JHF = 5.0 Hz, 1H); 19F NMR:
3
d
À63.2 (s, 3F), À122.4 (d, JFF = 141.0 Hz, 1F), À146.6 (dd,
3
3JFF = 142.0 Hz, JHF = 25.0 Hz, 1F); 13C NMR:
d 155.2 (dd,
2
2
1JCF = 250.0 Hz, JCF = 41.0 Hz), 141.4 (s), 130.9 (q, JCF = 32 Hz),
4.6. Reaction of 2 with pentafluoropyridine, preparation of 9 and 10
3
1
126.6 (s), 125.8 (q, JCF = 3.5 Hz), 124.2 (q, JCF = 273.0 Hz), 100.3
(dd, 1JCF = 316.0 Hz, 2JCF = 67.0 Hz), 66.7 (d, 2JCF = 23.0 Hz). GC–MS,
m/z (relative intensity): 364 (M+, 3.7), 345 (M+ÀF, 5.7), 295
(M+ÀCF3, 0.64), 237 (M+ÀI, 100), 219 (M+ÀCF3C6H4, 20.8), 189
(ICF55CF+, 48.4), 145 (CF3C6H4+, 34.2), 127 (I+, 77.8). IR (cm+1): 3613
(br, m), 1325 (vs), 1171 (s), 1136 (vs), 861 (w).
If the reaction was quenched by water followed by extraction
with ether and H2O wash, column chromatography gave only 4, in
71% isolated yield.
A 2-neck flask equipped with a magnetic stir bar, rubber septum
and nitrogen inlet was charged with anhydrous KF (58 mg,
1.00 mmol). Then pentafluoropyridine (338 mg, 2.00 mmol) and 2
(480 mg, 1.57 mmol) were added via syringe. After stirring the
reaction mixture at RT for 10 min, 19F NMR analysis of the reaction
mixture indicated that all the vinylsilane had been consumed, and
three products A, B and C, in the ratio of 34:34:32, had been formed.
Product C was identified as (E)-1,2-difluoro-1,2-diiodoethene, 11, by
comparison of its 19F NMR data with a known sample [12]. The
reaction mixture was quenched with H2O, extracted with ether and
driedover MgSO4. Column chromatographyon silicagel withhexane
gave a white solid product; 140 mg (yield: 26%), identified as (Z)-1-
iodo-1,2-difluoro-2-tetrafluoropyridylethene, mp = 44.5–45 8C, 9,
and 130 mg (yield, 23%) of a white solid (mp 95–96 8C) identified
4.3. Preparation of (Z)-1,2-difluoro-1-iodo-3-trimethylsiloxy-3-(p-
chlorophenyl) ethene, 6
Similar to Section 4.2, 6 was prepared via the reaction of
(440 mg, 1.00 mmol) of (E)-1,2 difluoro-1-iodo-2-trimethylsily-
lethene, p-chlorobenzaldehyde (170 mg, 1.20 mmol), KF (116 mg,
2.00 mmol) in DMSO (2 ml) at RT for 3 h. Usual workup gave the
as (E)-1,2-difluoro-1,2-tetrafluoropyridylethene, 10. 19F NMR of 9:
d
3
4
À88.8 (m, 2F), À107.3 (dt, JFF = 148.7 Hz, JFF 16.3 Hz, 1F), À132.6
addition product, 6, (300 mg, yield: 75%). 1H NMR:
5.80 (dd, 3JHF = 26.0 Hz, 4JHF = 5.5 Hz, 1H), 0.16 (s, 9H); 19F NMR:
d
7.3 (s, 4H),
(dt, JFF = 149.3 Hz, JFF = 8.6 Hz, 1F), À137.7 (m, 2F). 13C NMR:
d
3
5
d
143.8 (dm, 1JCF = 246 Hz), 142.0 (dd, 1JCF = 240.9 Hz, 2JCF = 44.5 Hz),
3
4
1
1
À123.9 (dd, JFF = 142.0 Hz, JHF = 5.0 Hz, 1F), À145.4 (dd,
138.8 (dm, JCF = 268 Hz), 120.5 (m), 105.5 (dd, JCF = 327 Hz,
2JCF = 66.5 Hz). GC–MS, m/z (relative intensity): 339 (M+, 100), 212
(M+ÀI, 39), 193(M+ÀIÀF, 20), 162 (80). IR(cmÀ1):1672 (m), 1638 (s),
1484 (vs), 1477 (vs), 1259 (m), 1469 (vs), 1195 (vs), 1166 (vs), 1152
3
3JFF = 142.0 Hz, JHF = 25.0 Hz, 1F); 13C NMR:
d 156.1 (dd,
2
1JCF = 253.0 Hz, JCF = 40.0 Hz), 137.0 (s), 133.9 (s), 128.6 (s),
1
2
127.5 (s), 99.1 (dd, JCF = 314.0 Hz, JCF = 67.0 Hz), 66.5 (d,
2JCF = 22.0 Hz), 0.30 (s). GC–MS, m/z (relative intensity): 405
(M++1, 1), 403 (M++1, 1), 367 (M+ÀCl, 1), 275 (26), 73 (100, +SiMe3).
IR (cmÀ1): 2962 (m), 1491 (m), 1256 (s), 1133 (s), 1090 (s), 875 (s).
(s), 926 (s). 10, 19F NMR:
(m, 2F); 13C NMR:
143.7 (dtm, JCF = 246.5 Hz, JCF = 15.0 Hz),
d
À87.85 (m, 4F), À137.0 (m, 4F), À138.95
1 2
d
142.9–138.8 (m), 139.3 (dm, 1JCF = 270.0 Hz), 120.0–119.8 (m). GC–
MS, m/z (relative intensity): 362 (M+, 88), 343 (M+ÀF, 13), 293 (100),
262 (26), 248 (79), 181 (11), 117 (22).
4.4. Preparation of (Z)-1,2-difluoro-1-iodo-2-benzoylethene, 7
When TAFS was used in place of KF, the same reaction was
completed at RT in 2 min. The ratio of 9, 10, 11, was 43:28:29.
Usual workup gave 9 in 29% isolated yield and 10 in 18% isolated
yield.
A 2-neck flask equipped with a magnetic stir bar, rubber
septum, and nitrogen inlet was charged with anhydrous AlCl3
(260 mg, 2.00 mmol), in anhydrous CH2Cl2 (3 ml). To the above

944
Y.-B. He et al. / Journal of Fluorine Chemistry 132 (2011) 940–944
4.7. Reaction of 2 with perfluorotoluene, preparation of 12 and 13
359 (M+ÀSiEt3, 0.24), 329 (M+ÀCF3C6H4, 2.4), 275 (11), 201
(CF3C6H4CHOSi+, 17.5), 115 (SiEt3+, 17), 77 (C6H5+, 100). IR (cmÀ1):
2958 (s), 2877 (m), 1457 (m), 1325 (vs), 1262 (s), 1169 (s), 1134
(vs), 846 (m).
Similar to Section 4.6, perfluorotoluene (684 mg, 2.9 mmol),
anhydrous KF (58 mg, 1.0 mmol) and 2 (760 mg, 2.5 mmol) were
stirred at RT for 1 h. 19F NMR analysis of the reaction mixture
showed that most of the vinylsilane had been consumed. After
stirring the mixture for an additional 2 h at RT, the ratio of products
(by 19F NMR), 12 and 13, 11 was 33:40:27. The reaction was
quenched with H2O, extracted with ether, and dried over MgSO4.
Column chromatography on silica gel with hexane gave 12
4.9. Reaction of 2 and KF with trifluoroacetophenone, 15
Similar to Section 4.2, 2 (280 mg, 0.92 mmol), trifluoroaceto-
phenone (174 mg, 1.00 mmol) KF (116 mg, 2.00 mmol) in DMSO
(2 ml) were reacted for 3 h at RT. After the usual work-up, 260 mg
(60%) of (Z)-1,2-difluoro-1-iodo-3-phenyl-3-triethylsiloxy-4,4,4-
(250 mg, yield = 25%) and 13 (350 mg, 28%). 19F NMR of 12:
d
À57.2 (t, 4JFF = 22.0 Hz, 3F), À109.3 (dt, 3JFF = 148.0 Hz,
trifluoro-1-butene, 15 was isolated. 1H NMR:
7.40–7.37 (m, 3H), 0.97 (t, 3JHH = 7.5 Hz, 9H), 0.79 (q, 3JHH = 7.5 Hz,
d 7.56–7.53 (m, 2H),
3
5
4JFF = 15.0 Hz, 1F), À130.7 (dt, JFF = 149.0 Hz, JFF = 7.5 Hz, 1F),
À134.6 to 134.7 (m, 2F), À139.1 to 139.5 (m, 2F); 13C NMR:
d
6H); 19F NMR:
d
À76.15 (dd, JFF = 15.0 Hz, JFF = 10.0 Hz, 3F),
4
5
1
2
3 4
156.2–142.1 (m), 141.9 (dd, JCF = 246.0 Hz, JCF = 45.0 Hz), 120.6
À106.39 (dq, JFF = 150.0 Hz, JFF = 15 Hz, 1F), À129.5 (dq,
1
1
5
(q, JCF = 275 Hz), 112.9–111.4 (m), 104.3 (dd, JCF = 325.0 Hz,
2JCF = 67.0 Hz). GC–MS, m/z (relative intensity): 406 (M+, 100), 387
(M+ÀF, 15), 279 (M+ÀI, 25), 260 (M+ÀIÀF, 13), 241 (M+À2F, 14),
229 (CF3C6F4C+, 48), 210 (M+ÀIÀCF3, 54), 127 (I+, 8), 69 (CF3+, 9). IR
3JFF = 150.0 Hz, JFF = 10.0 Hz, 1F); 13C NMR:
d
159.9 (dd,
1JCF = 285.0 Hz, JCF = 36.0 Hz), 135.3 (s), 129.4 (s), 128.3 (s),
2
1
3
126.8 (s), 123.2 (qd, JCF = 287.0 Hz, JCF = 5.0 Hz), 106.2 (dd,
1JCF = 286 Hz, JCF = 71 Hz), 79.40 (m), 6.7 (s), 5.5 (s). IR (cmÀ1):
2
(cmÀ1): 1660 (vs), 1501 (s), 1493 (s), 1348 (s), 1270 (s), 1179 (vs),
2959 (m), 2880 (m), 1207 (m), 1188 (s), 1179 (s), 1151 (m). GC–MS,
m/z (relative intensity): no parent ion, 198 (74), 170, (40, ICF55C+),
151 (60), 115 (Si+Et3, 7), (77, 100, C6H5+).
4
1162 (m), 999 (s). 13, 19F NMR:
d
À57.1 (t, JFF = 22.0 Hz, 6F),
À134.1 to 134.2 (m, 4F), À138.3 (pentet, 4JFF = 12.0 Hz, 2F); À138.7
to À139.0 (m, 4F); 13C NMR: 144.5 (dm, JCF = 263.0 Hz), 141.4–
1
137.3 (m), 120.5 (q, 1JCF = 276.0 Hz), 113.4–111.8 (m). GC–MS, m/z
(relative intensity): 496 (M+, 100), 477 (45), 427 (45), 408 (12), 377
(48), 358 (5), 320 (5), 217 (8). IR (cmÀ1): 1502 (s), 1493 (s), 1345
(vs), 1299 (s), 1200 (s), 1178 (s), 1163 (s).
Acknowledgements
We would like to thank the National Science Foundation for
financial support of this work. YBH acknowledges partial support
by the Ethyl Corporation.
4.8. Reaction of 4 with 1-ethynyl-1-cyclohexanol, preparation of 14
References
A 2-neck flask equipped with a magnetic stir bar, rubber
septum, and condenser topped with a nitrogen inlet was charged
with Pd(PPh3)2Cl2 (50 mg, 0.07 mmol), Cu(I)I (19 mg, 0.10 mmol)
and NEt3 (3 ml). Then 1-ethynyl-1-cyclohexanol (170 mg,
1.37 mmol) and 4 (340 mg, 0.71 mmol) were added to the catalytic
mixture via syringe. After the reaction mixture was stirred at 60–
70 8C for 2.5 h, 19F NMR analysis of the reaction mixture indicated
the reaction was complete. Then, the volatile components of the
reaction mixture were pumped off. Dilute (3 N) HCl was added to
the residue, the residue extracted with ether, washed with water,
and dried over MgSO4. Column chromatography on silica gel
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(hexane/ethyl acetate = 10/1) gave the product 14, (305 mg) in 89%
4,5
yield. 1H NMR:
d
7.48 (q,
J
HF
= 8.5 Hz, 4H), 5.76 (dd,
3JHF = 25.0 Hz, JHF = 3.5 Hz, 1H), 2.87 (brs, 1H), 1.91–1.83 (m,
4
3
2H), 1.54–1.40 (m, 7H), 1.15–1.07 (m, 1H), 0.89 (t, JHH = 8.0 Hz,
9H), 0.70 (q, 3JHH = 7.8 Hz, 6H); 19F NMR:
d
À63.04 (s, 3F), À152.28
(dd, 3JFF = 135.0 Hz, 4JHF = 3.5 Hz, 1F), À155.77 (dd, 3JFF = 135.0 Hz,
3JHF = 25.0 Hz, 1F); 13C NMR:
d
155.6 (dd, JCF = 310.0 Hz,
1
2JCF = 51.0 Hz), 142.1 (s), 131.99 (dd, 1JCF = 220.0 Hz, 2JCF = 48.0 Hz),
2
129.4 (q, JCF = 32.0 Hz), 125.51 (s), 124.4 (s), 123.14 (q,
1JCF = 272 Hz), 104.84 (dd, JCF = 13.0 Hz, JCF = 7.6 Hz), 70.15 (dd,
2JCF = 36.6 Hz, 3JCF = 6.4 Hz), 68.22 (s), 38.38 (s), 23.98 (s), 22.06 (s),
5.48 (s), 3.53 (s). GC–MS, m/z (relative intensity): 455 (M+ÀF, 1.5),
3
4