Palladium-catalyzed cross-coupling of fluorinated vinyl chlorides with terminal alkynes: A general protocol to fluorinated enynes

Article abstract of DOI:10.1002/cjoc.201300352

An efficient and cost-effective method for the preparation of fluorinated conjugated enynes was described. The method was compatible with a variety of functional groups such as chloride, amine, cyano and ester group. The method could also be extended to the coupling of (R,Z)-3-(2-chloro-1,2-difluorovinyl)- 4-alkyloxazolidin-2-one (3) with moderate yields. An efficient and cost-effective method for the preparation of fluorinated conjugated enynes was described. The method was compatible with a variety of functional groups such as chloride, amine, cyano and ester group. The method could also be extended to the coupling of (R,Z)-3-(2-chloro-1,2-difluorovinyl)-4-alkyloxazolidin-2-one (3) with moderate yields. Copyright

Full text of DOI:10.1002/cjoc.201300352

FULL PAPER
DOI: 10.1002/cjoc.201300352
Palladium-Catalyzed Cross-Coupling of Fluorinated Vinyl
Chlorides with Terminal Alkynes: A General Protocol to
Fluorinated Enynes
Sheng Chen, Chunfa Xu, Long Lu,* and Qilong Shen*
Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, Shanghai 200032, China
An efficient and cost-effective method for the preparation of fluorinated conjugated enynes was described. The
method was compatible with a variety of functional groups such as chloride, amine, cyano and ester group. The
method could also be extended to the coupling of (R,Z)-3-(2-chloro-1,2-difluorovinyl)-4-alkyloxazolidin-2-one (3)
with moderate yields.
Keywords fluorine, enyne, palladium, chlorotrifluoroethylene
Introduction
Under these conditions, a number of alkynes were di-
rectly coupled with fluorinated vinyl iodides to give the
desired fluorinated enynes in good yields. Nevertheless,
both of these methods involved fluorinated vinyl iodides
as the substrates that typically required multiple steps
for their synthesis.
Conjugated enynes are important structural motifs in
medicinal chemistry and in conjugated polymers with
optoelectronic application.[1] For example, Terbinafine
(Lamisil™),[1d] an enyne derivative, is currently in
clinical use as an antifungal medicine and carbazole-
substituted phenyl enynes has been shown to be an ex-
cellent single-emitting component for white organic
light-emitting devices (WOLEDs).[1e] In addition, con-
jugated enynes are valuable building blocks in organic
synthesis that can be converted into a variety of differ-
ent functional groups.[2] On the other hand, it is
well-known that incorporation of fluorine into small
molecules will result in significant changes in their
physical, chemical and biological properties.[3] Thus,
fluorinated conjugated enynes are expected to be versa-
tile building blocks in the preparation of partially
fluorinated molecules that might find applications in
medicinal chemistry or materials science. Consequently,
development of new methods for the preparation of
fluorinated conjugated enynes is of great interest.
More recently, we reported a palladium catalyzed
Suzuki-Miyaura coupling reaction of chlorotrifluoro-
ethylene with a variety of aryl boronic acids for the
formation of trifluorostyrene derivatives.[6] As part of
our ongoing programs with the aim to utilize cheap and
easily available chlorotrifluoroethylene as starting ma-
terial, we wondered if it could be possible to realize the
Sonogashira reaction of chlorotrifluoroethylene with
terminal alkynes. In general, carbon-chloride bond is
much stronger than carbon-bromide and carbon-iodide
bond, as a consequence, the activation of carbon-chlo-
ride bond is more difficult.[7] Few coupling reaction of
fluorinated vinyl chlorides has been reported previ-
ously.[8] Herein, we reported a palladium/copper-cata-
lyzed direct coupling of chlorotrifluoroethylene with
terminal alkynes in good to excellent yields.
In 1987, Normant et al.[4] reported the first palla-
dium-catalyzed coupling of fluorinated vinyl iodides
with terminal alkynylzinc reagents for the preparation of
fluorinated conjugated enynes. Although moderate to
good yields were achieved in this approach, the prior
generation of the requisite alkynyl zinc reagent was
necessary. To circumvent the using of the alkynyl zinc
reagent, Yang and Burton improved the reaction condi-
tions by using the combination of Pd(PPh3)2Cl2 and CuI
as the catalyst in the presence of Et3N as the base.[5]
Experimental
General procedure for preparation of compound 3
A Schlenk-type tube (with a condenser) equipped
with a magnetic stir bar charged with oxazolidinone (1.0
mmol) was vacuumed and recharged with argon three
times. THF (2.0 mL) was added and the solution was
cooled to −78 ℃. n-BuLi (1.1 mmol) solution was then
added slowly. The reaction mixture was stirred for 4 h at
* E-mail: shenql@sioc.ac.cn
Received April 25, 2013; accepted June 17, 2013; published online July 19, 2013.
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cjoc.201300352 or from the author.
Chin. J. Chem. 2013, 31, 901—907
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General procedure B for preparation of fluorinated
enynes (2g, 2i, 2j, 2l, 2m)
this temperature. 5.0 mmol of chlorotrifluoroethylene in
a balloon was condensed into the tube. And the tube was
stirred for another 6 h at room temperature. The reaction
was quenched with water when the oxazolidinone dis-
appeared as determined by TLC. The mixture was sepa-
rated and the water phase was extracted with ethyl ace-
tate three times. The organic phase was combined and
concentrated. The resulting residue was purified by sil-
ica gel flash column chromatography to give 189.5 mg
(84%) of (R,Z)-3-(2-chloro-1,2-difluorovinyl)-4-isopro-
pyloxazolidin-2-one (3a) and 238.1 mg (87%) of
(R,Z)-3-(2-chloro-1,2-difluorovinyl)-4-benzyloxazolidin-
2-one (3b) as pale yellow solid.
(Z)-3-(2-Chloro-1,2-difluorovinyl)-4-isopropyloxa-
zolidin-2-one (3a) 1H NMR (300 MHz, CDCl3, 293 K,
TMS) δ: 4.47－4.41 (m, 1H), 4.24－4.20 (m, 1H), 4.06
－4.01 (m, 1H), 2.05－2.00 (m, 1H), 1.00－0.93 (m,
6H); 19F NMR (282 MHz, CDCl3, 293 K, TMS) δ:
−116.9 (dd, J＝116.7, 7.9 Hz, 1F), −127.9 (d, J＝124.6
Hz, 1F); 13C NMR (100.5 MHz, CDCl3, 293 K, TMS) δ:
154.2, 137.6 (m), 134.9 (m), 64.9, 60.2, 29.6, 17.3, 15.1.
MS (EI) m/z (%): 225 (100). HRMS: Calculated for
C8H10F2O2NCl: 225.0368, found 225.0370.
(Z)-4-Benzyl-3-(2-chloro-1,2-difluorovinyl)oxa-
zolidin-2-one (3b) 1H NMR (300 MHz, CDCl3, 293 K,
TMS) δ: 7.37－7.30 (m, 3H), 7.21－7.19 (m, 2H), 4.42
－4.34 (m, 2H), 4.21－4.18 (m, 1H), 3.17－3.12 (m,
1H), 2.89－2.83 (m, 1H); 19F NMR (282 MHz, CDCl3,
293 K, TMS) δ: −113.8 (d, J＝124.6 Hz, 1F), −124.9 (d,
J＝126.6 Hz, 1F); 13C NMR (100.5 MHz, CDCl3, 293 K,
TMS) δ: 153.6, 137.5 (dd, J＝291.5, 68.9 Hz), 134.8
(dd, J＝211.5, 46.2 Hz), 134.2, 129.0, 128.9, 127.6,
68.2, 56.6, 39.0. MS (EI) m/z (%): 273 (100). HRMS:
Calculated for C12H10F2O2NCl: 273.0368, found
273.0372.
A Schlenk-type tube equipped with a magnetic stir
bar was charged with the alkyne (1.0 mmol), Pd(PPh3)4
(116 mg, 0.10 mmol), CuI (191 mg, 1.0 mmol), K3PO4
(637 mg, 3 mmol). The reaction tube was capped, then
evacuated briefly under high vacuum and charged with
argon for three times. Benzene (4.0 mL) and deionized
water (1.4 mL) was added. Chlorotrifluoroethylene was
bubbled for 5.0 min. The reaction mixture was stirred at
80 ℃ for 10 h. The mixture was cooled to room tem-
perature and was extracted with 20 mL of diethyl ether
for three times. The organic phase was combined, dried
over anhydrous Na2SO4. Silica gel (10.0 g) was added
to the solution. The solvent was then evacuated under
rotaty evaporator. The residue was purified by silica gel
flash column chromatography using hexane as eluent.
General procedure C for preparation of fluorinated
enynes (4a－4g)
A Schlenk-type tube equipped with a magnetic stir
bar was charged with the alkyne (1 mmol), compound 3
(1.0 mmol), Pd(PPh3)2Cl2 (70.1 mg, 0.1 mmol), CuI
(19.1 mg, 0.1 mmol). The reaction tube was evacuated
briefly under high vacuum and charged with argon for
three times. Triethylamine (96 mg, 1.0 mmol) and
DMSO (2.0 mL) was then added. The reaction mixture
was stirred at 45 ℃ for 10 h. The mixture was cooled
to room temperature. The mixture was concentrated and
the residue was purified by silica gel flash column
chromatography to give the corresponding coupling
product.
1-Fluoro-4-(3,4,4-trifluorobut-3-en-1-ynyl)benzene
(Table 2, 2a) 1H NMR (300 MHz, CDCl3, 293 K,
TMS) δ: 7.48－7.45 (m, 2H), 7.06－7.02 (m, 2H); 19F
NMR (282 MHz, CDCl3, 293 K, TMS) δ: −90.1－90.3
(m, 1F), −108.1－108.2 (m, 1F), −110.1－110.6 (m, 1F),
−172.0 (dd, J＝115.0, 26.8 Hz, 1F); 13C NMR (100.5
MHz, CDCl3, 293 K, TMS) δ: 163.3 (d, J＝288 Hz),
157.7 (td, J＝297.5, 52.3 Hz), 133.7 (m), 128.2 (d, J＝
0.8 Hz), 115.9 (m), 115.7 (m), 101.1 (m), 73.1 (m). MS
(EI) m/z (%): 200 (100). HRMS: Calculated for C10H4F4:
200.0249, found 200.0253.
1-Methyl-4-(3,4,4-trifluorobut-3-en-1-ynyl)benzene
(Table 2, 2b) 1H NMR (300 MHz, CDCl3, 293 K,
TMS) δ: 7.39 (d, J＝8.0 Hz, 2H), 7.17 (d, J＝8.0 Hz,
2H), 2.37 (s, 3H); 19F NMR (282 MHz, CDCl3, 293 K,
TMS) δ: −91.2 (dd, J＝47.6, 27.9 Hz, 1F), −110.7 (dd,
J＝114.8, 47.6 Hz, 1F), −171.5 (dd, J＝114.8, 27.9 Hz,
1F); 13C NMR (100.5 MHz, CDCl3, 293 K, TMS) δ:
157.6 (ddd, J＝296.5, 285.4, 52.7 Hz), 140.2, 131.5,
129.2, 128.3, 116.0 (ddd, J＝222.1, 53.3, 30.8 Hz),
102.5 (m), 72.7 (ddd, J＝32.2, 10.1, 3.0 Hz), 21.4. MS
(EI) m/z (%): 196 (100). HRMS: Calculated for C11H7F3:
196.0500, found 196.0504.
General procedure A for preparation of fluorinated
enynes (2a－2f, 2h, 2k, 2n, 2o)
A Schlenk-type tube (with a condenser) equipped
with a magnetic stir bar was charged with the alkyne
(1.0 mmol), Pd(PPh3)4 (116 mg, 0.10 mmol), CuI (19.1
mg, 0.10 mmol), tributylamine (37 mg, 0.20 mmol),
K3PO4 (637 mg, 3.0 mmol). And the reaction tube was
added benzene (2.0 mL) and water (0.7 mL). The tube
was equipped with a dry ice/acetone condenser, and
then evacuated briefly under high vacuum and charged
with argon three times. 5 mmol of chlorotrifluoroethyl-
ene in a ballon was plunged into the tube. Then the re-
action mixture was stirred at 80 ℃ for 10 h. The reac-
tion was then cooled to room temperature. The mixture
was extracted with 20 mL of diethyl ether three times.
The organic phase was combined, dried with anhydrous
Na2SO4. Silica gel (10.0 g) was added to the solution.
The solvent was then evacuated under rotaty evaporator.
The residue was purified by silica gel flash column
chromatography using hexane as eluent. Further purifi-
cation was conducted by Kugelrohr distillation.
1-Propyl-4-(3,4,4-trifluorobut-3-en-1-ynyl)benzene
(Table 2, 2c) 1H NMR (300 MHz, CDCl3, 293 K,
TMS) δ: 7.43－7.41 (m, 2H), 7.19－7.17 (m, 2H), 2.65
902
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Chin. J. Chem. 2013, 31, 901—907

Palladium-Catalyzed Cross-Coupling of Fluorinated Vinyl Chlorides with Terminal Alkynes
(t, J＝7.6 Hz, 2H), 1.68－1.62 (m, 2H), 0.95 (t, J＝7.6
Hz, 3H); 19F NMR (282 MHz, CDCl3, 293 K, TMS) δ:
−91.2 (dd, J＝47.6, 27.9 Hz, 1F), −111.2 (dd, J＝114.7,
47.6 Hz, 1F), −171.5 (dd, J＝114.7, 47.6 Hz, 1F); 13C
NMR (100.5 MHz, CDCl3, 293 K, TMS) δ: 157.6 (ddd,
J＝296.5, 285.4, 53.3 Hz), 144.9, 131.5, 128.7, 118.0
(ddd, J＝222.1, 53.3, 31.2 Hz), 115.9 (m), 102.5, 72.7
(ddd, J＝32.2, 10.1, 3.1 Hz), 38.0, 24.2, 13.6. MS (EI)
m/z (%): 224 (100). HRMS: Calculated for C13H11F3:
224.0813, found 224.0817.
1-tert-Butyl-4-(3,4,4-trifluorobut-3-en-1-ynyl)ben-
zene (Table 2, 2d) 1H NMR (300 MHz, CDCl3, 293 K,
TMS) δ: 7.45－7.37 (m, 4H), 1.32 (s, 9H); 19F NMR
(282 MHz, CDCl3, 293 K, TMS) δ: −90.8 (dd, J＝47.6,
27.4 Hz, 1F), −110.7 (dd, J＝114.7, 47.2 Hz, 1F),
−171.2 (dd, J＝114.7, 47.2 Hz, 1F); 13C NMR (100.5
MHz, CDCl3, 293 K, TMS) δ: 157.6 (ddd, J＝296.5,
285.4, 52.7 Hz), 153.3, 131.4, 125.5, 117.8, 115.9 (ddd,
J＝274.4, 53.3, 30.8 Hz), 102.5 (m), 72.7 (ddd, J＝32.2,
10.1, 3.1 Hz), 34.9, 31.0. MS (EI) m/z (%): 238 (100).
HRMS: Calculated for C14H13F3: 238.0969, found
238.0973.
1-Methoxy-4-(3,4,4-trifluorobut-3-en-1-ynyl)ben-
zene (Table 2, 2e) 1H NMR (300 MHz, CDCl3, 293 K,
TMS) δ: 7.42 (d, J＝8.8 Hz, 2H), 6.86 (d, J＝8.8 Hz
2H), 3.81 (s, 3H); 19F NMR (282 MHz, CDCl3, 293 K,
TMS) δ: −91.1 (dd, J＝48.0, 26.6 Hz, 1F), −110.9 (dd,
J＝114.7, 47.7 Hz, 1F), −170.7 (dd, J＝114.3, 26.6 Hz,
1F); 13C NMR (100.5 MHz, CDCl3, 293 K, TMS) δ:
160.8, 157.5 (ddd, J＝296.5, 285.4, 53.2 Hz), 133.3,
115.8 (ddd, J＝279.4, 58.3, 27.3 Hz), 114.1, 112.8,
102.4 (m), 72.1 (ddd, J＝31.6, 9.6, 2.5 Hz), 55.3. MS
(EI) m/z (%): 212 (100). HRMS: Calculated for
C11H7F3O: 212.0449, found 212.0451.
1-Fluoro-2-(3,4,4-trifluorobut-3-en-1-ynyl)benzene
(Table 2, 2h) 1H NMR (300 MHz, CDCl3, 293 K,
TMS) δ: 7.48－7.35 (m, 2H), 7.15－7.07 (m, 2H); 19F
NMR (282 MHz, CDCl3, 293 K, TMS) δ: −89.4－89.6
(m, 1F), −108.6 (m, 1F), −109.2－109.7 (m, 1F), −172.4
－172.8 (m, 1F); 13C NMR (100.5 MHz, CDCl3, 293 K,
TMS) δ: 162.4 (d, J＝296.5 Hz), 157.7 (ddd, J＝297.5,
286.5, 51.5 Hz), 133.2, 131.7, 128.8, 124.1, 115.7 (d,
J＝20.7 Hz), 115.6 (ddd, J＝232.2, 54.3, 30.2 Hz), 95.7
(m), 77.9 (m). MS (EI) m/z (%): 200 (100). HRMS:
Calculated for C10H4F3: 200.0249, found 200.0247.
1-Chloro-2-(3,4,4-trifluorobut-3-en-1-ynyl)benzene
(Table 2, 2i) 1H NMR (400 MHz, CDCl3, 293 K,
TMS) δ: 7.88－6.71 (m, 4H); 19F NMR (376 MHz,
CDCl3, 293 K) δ: −89.2 (dd, J＝43.0, 27.8 Hz, 1F),
−109.2 (dd, J＝114.7, 43.3 Hz, 1F), −172.6 (dd, J＝
114.9, 27.8 Hz, 1F); 13C NMR (100.5 MHz, CDCl3, 293
K, TMS) δ: 157.70 (ddd, J＝297.4, 286.5, 51.5 Hz),
133.17, 130.73, 129.47, 128.29, 126.56, 120.99, 115.66
(ddd, J＝221.4, 53.0, 30.6 Hz), 98.80 (ddd, J＝10.2, 8.4,
5.3 Hz), 78.03 (ddd, J＝31.9, 9.9, 2.8 Hz). MS (EI) m/z
(%): 216 (100). HRMS: Calculated for C10H4F3Cl:
215.9954, found 215.9957.
1-Chloro-3-(3,4,4-trifluorobut-3-en-1-ynyl)benzene
(Table 2, 2j) 1H NMR (400 MHz, CDCl3, 293 K,
TMS) δ: 7.70－6.90 (m, 4H); 19F NMR (376 MHz,
CDCl3, 293 K) δ: −89.3 (dd, J＝44.0, 27.9 Hz, 1F),
−109.6 (dd, J＝114.9, 43.9 Hz, 1F), −172.6 (dd, J＝
114.9, 27.9 Hz, 1F); 13C NMR (100.5 MHz, CDCl3, 293
K, TMS) δ: 157.73 (ddd, J＝297.3, 286.2, 51.5 Hz),
134.47, 131.28 (m), 130.02, 129.75, 129.60 (m), 128.31,
115.6 (ddd, J＝222.2, 53.5, 30.6 Hz), 100.64 (ddd, J＝
10.1, 8.3, 5.2 Hz), 74.38 (ddd, J＝12.9, 9.6, 2.7 Hz).
MS (EI) m/z (%): 216 (100). HRMS: Calculated for
C10H4F3Cl: 215.9954, found 215.9949.
4-(3,4,4-Trifluorobut-3-en-1-ynyl)benzonitrile
(Table 2, 2f) 1H NMR (300 MHz, CDCl3, 293 K,
TMS) δ: 7.64 (d, J＝8.0 Hz, 2H), 7.56 (d, J＝8.4 Hz,
2H); 19F NMR (282 MHz, CDCl3, 293 K, TMS) δ:
−87.6 (dd, J＝40.1, 28.5 Hz, 1F), −108.1 (dd, J＝114.7,
40.5 Hz, 1F), −173.3 (dd, J＝114.7, 28.5 Hz, 1F); 13C
NMR (100.5 MHz, CDCl3, 293 K, TMS) δ: 157.8 (ddd,
J＝298.5, 287.4, 50.6 Hz), 132.2, 131.8, 125.4, 117.9,
115.4 (ddd, J＝223.1, 53.3, 31.2 Hz), 113.1, 100.2 (m),
77.3 (m). MS (EI) m/z (%): 207 (100). HRMS: Calcu-
lated for C11H4F3N: 207.0296, found 207.0299.
Methyl 4-(3,4,4-trifluorobut-3-en-1-ynyl)benzoate
(Table 2, 2g) 1H NMR (300 MHz, CDCl3, 293 K,
TMS) δ: 8.02 (d, J＝8.2 Hz, 2H), 7.54 (d, J＝8.2 Hz,
2H), 3.89 (s, 3H); 19F NMR (282 MHz, CDCl3) δ: −89.2
(dd, J＝42.7, 27.8 Hz, 1F), −109.5 (dd, J＝114.8, 42.7
Hz, 1F), −173.1 (dd, J＝114.7, 27.8 Hz, 1F); 13C NMR
(75 MHz, CDCl3, 293 K, TMS) δ: 166.0, 157.6 (ddd,
J＝297.5, 286.5, 51.5 Hz), 131.2, 130.7, 129.5, 125.0,
115.3 (ddd, J＝80.8, 54.1, 27.1 Hz), 101.2 (m), 75.7
(ddd, J＝31.7, 9.9, 2.7 Hz), 52.2. MS(EI) m/z (%):
209.1 (100). HRMS: Calculated for C12H7F3O2:
2240.0398, found 240.0395.
3-(3,4,4-Trifluorobut-3-en-1-ynyl)aniline (Table 2,
2k) 1H NMR (300 MHz, CDCl3, 293 K, TMS) δ: 7.20
(t, J＝8.0 Hz, 1H), 6.87 (d, J＝7.6 Hz, 1H), 6.77 (s, 1H),
6.70－6.67 (m, 1H), 3.70 (s, 2H); 19F NMR (282 MHz,
CDCl3, 293 K, TMS) δ: −90.4 (dd, J＝46.1, 27.4 Hz,
1F), −110.4 (dd, J＝114.0, 46.1 Hz, 1F), −171.4 (dd,
J＝114.7, 27.4 Hz, 1F); 13C NMR (100.5 MHz, CDCl3,
293 K, TMS) δ: 157.4 (ddd, J＝297.3, 286.2, 51.5 Hz),
146.4, 129.4, 121.8, 121.4, 117.4, 116.6 (m), 116.2,
102.5 (m), 72.7 (m). MS (EI) m/z (%): 197 (100).
HRMS: Calculated for C10H6F3N: 197.0452, found
197.0449.
2-(3,4,4-Trifluorobut-3-en-1-ynyl)thiophene (Table
2, 2l) 1H NMR (400 MHz, CDCl3, 293 K) δ: 7.61 (d,
J＝2.0 Hz, 1H), 7.32 (dd, J＝4.9, 2.9 Hz, 1H), 7.17 (d,
J＝4.7 Hz, 1H); 19F NMR (376 MHz, CDCl3, 293 K) δ:
−90.1 (dd, J＝46.0, 27.2 Hz, 1F), −110.2 (dd, J＝115.1,
46.1 Hz, 1F), −171.6 (dd, J＝115.1, 27.2 Hz, 1F); 13C
NMR (100.5 MHz, CDCl3, 293 K, TMS) δ: 158.1 (ddd,
J＝299.9, 292.9, 54.5 Hz), 130.99, 129.48, 125.96,
119.94, 115.80 (ddd, J＝221.3, 52.6, 30.5 Hz), 97.47
(ddd, J＝9.9, 8.1, 5.0 Hz), 72.97 (ddd, J＝12.8, 9.6, 2.7
Hz). MS (EI) m/z (%): 188 (100). HRMS: Calculated
Chin. J. Chem. 2013, 31, 901—907
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903

Chen et al.
FULL PAPER
for C8H3F3S: 187.9908, found 187.9912.
1H NMR (300 MHz, CDCl3, 293 K, TMS) δ: 7.61－
6.93 (m, 4H), 4.47－4.44 (m, 1H), 4.27－4.08 (m, 2H),
3.85 (s, 3H), 2.13－2.02 (m, 1H), 1.03－0.96 (m, 6H);
19F NMR (282 MHz, CDCl3, 293 K, TMS) δ: −130.6 (d,
J＝128.9 Hz, 1F), −144.2 (d, J＝128.6 Hz, 1F); 13C
NMR (100.5 MHz, CDCl3, 293 K, TMS) δ: 135.5, 131.1,
128.8, 127.0, 113.2, 113.0, 64.8, 60.5, 55.2, 29.6, 17.4,
15.2. MS (EI) m/z (%): 321 (100). HRMS: Calculated
for C17H17F2O3N: 321.1176, found 321.1181.
2-Methoxy-6-(3,4,4-trifluorobut-3-en-1-ynyl)naph-
thalene (Table 2, 2m) 1H NMR (300 MHz, CDCl3,
293 K, TMS) δ: 7.95－7.11 (m, 6H), 3.93 (s, 3H); 19F
NMR (282 MHz, CDCl3, 293 K, TMS) δ: −90.4 (dd,
J＝46.8, 27.4 Hz, 1F), −110.4 (dd, J＝114.7, 46.8 Hz,
1F), −171.1 (dd, J＝114.7, 26.6 Hz, 1F); 13C NMR
(100.5 MHz, CDCl3, 293 K, TMS) δ: 168.9, 157.6,
149.1, 134.9, 132.0, 129.6, 128.9, 128.2, 127.0, 119.8,
115.6, 105.8, 98.7, 73.5 (m), 55.3. MS (EI) m/z (%): 262
(100). HRMS: Calculated for C15H9F3O: 262.0605,
found 262.0604.
4,5,5-Trifluoropent-4-en-2-ynyl benzoate (Table 2,
2n) 1H NMR (300 MHz, CDCl3, 293 K, TMS) δ:
8.08－8.03 (m, 2H), 7.57－7.55 (m, 1H), 7.46－7.42
(m, 2H), 5.12－5.10 (m, 2H); 19F NMR (282 MHz,
CDCl3, 293 K, TMS) δ: −87.9－88.0 (m, 1F), −108.9－
109.3 (m, 1F), −173.5－173.9 (m, 1F); 13C NMR (100.5
MHz, CDCl3, 293 K, TMS) δ: 165.6, 158.2 (ddd, J＝
297.3, 286.2, 51.5 Hz), 133.5, 129.8, 129.0, 128.5,
115.1 (m), 97.4 (m), 71.4 (m), 52.4. MS (EI) m/z (%):
240 (100). HRMS: Calculated for C12H7F3O2: 240.0398,
found 240.0400.
(4,5,5-Trifluoropent-4-en-2-ynyl)benzene (Table 2,
2o) 1H NMR (300 MHz, CDCl3, 293 K, TMS) δ:
7.34－7.23 (m, 5H), 3.84－3.82 (m, 2H); 19F NMR
(282 MHz, CDCl3, 293 K, TMS) δ: −91.2－91.4 (m,
1F), −112.1－112.5 (m, 1F), −171.4－171.8 (m, 1F);
13C NMR (100.5 MHz, CDCl3, 293 K, TMS) δ: 157.9
(ddd, J＝290.5, 289.4, 52.3 Hz), 128.7, 128.3, 127.9,
127.0, 115.0, 101.9 (m), 67.3 (m), 25.8. MS (EI) m/z
(%): 196 (100). HRMS: Calculated for C11H7F3:
196.0500, found 196.0499.
(E)-3-(1,2-Difluoro-4-m-tolylbut-1-en-3-ynyl)-4-
isopropyloxazolidin-2-one (Table 3, 4d) 1H NMR
(300 MHz, CDCl3, 293 K, TMS) δ: 7.58－7.22 (m, 4H),
4.51－4.45 (m, 1H), 4.27－4.13 (m, 2H), 2.41－2.40
(m, 3H), 2.11－2.06 (m, 1H), 1.04－0.97 (m, 6H); 19F
NMR (282 MHz, CDCl3, 293 K, TMS) δ: −128.2 (d,
J＝118.4 Hz, 1F), −149.6 (d, J＝121.2 Hz, 1F); 13C
NMR (100.5 MHz, CDCl3, 293 K, TMS) δ: 154.9, 139.9,
134.6, 129.2, 125.6, 102.4, 72.1, 65.0, 60.0, 29.7, 21.3,
17.5, 15.3. MS (EI) m/z (%): 305 (100). HRMS: Calcu-
lated for C17H17F2O2N: 305.1227, found 305.1225.
(E)-3-(1,2-Difluoro-4-(6-methoxynaphthalen-2-yl)-
but-1-en-3-ynyl)-4-isopropyloxazolidin-2-one (Table
3, 4e) 1H NMR (300 MHz, CDCl3, 293 K, TMS) δ:
7.98－7.48 (m, 4H), 7.19－7.11 (m, 2H), 4.48－4.42 (m,
1H), 4.26－4.11 (m, 2H), 3.93 (s, 3H), 2.44－2.41 (m,
3H), 2.11－2.07 (m, 1H), 1.02－0.98 (m, 6H); 19F NMR
(282 MHz, CDCl3, 293 K, TMS) δ: −122.4 (d, J＝121.6
Hz, 1F), −144.8 (d, J＝126.8 Hz, 1F); 13C NMR (100.5
MHz, CDCl3, 293 K, TMS) δ: 158.9, 149.1, 134.9,
132.1, 129.6, 128.2, 127.1, 123.9, 119.8, 115.5, 105.8,
98.7, 74.8, 64.9, 60.4, 55.4, 29.7, 17.4, 15.2. MS (EI)
m/z (%): 371 (100). HRMS: Calculated for
C21H19F2O3N: 371.1333, found 371.1329.
(E)-3-(1,2-Difluoro-4-phenyl-but-1-en-3-ynyl)-4-
isopropyloxazolidin-2-one (Table 3, 4a) 1H NMR
(300 MHz, CDCl3, 293 K, TMS) δ: 7.47－7.25 (m, 5H),
6.95－6.76 (m, 2H), 4.48－4.43 (m, 1H), 4.25－4.08
(m, 2H), 2.08－2.04 (m, 1H), 1.02－0.96 (m, 6H); 19F
NMR (282 MHz, CDCl3, 293 K, TMS) δ: −131.9 (dd,
J＝128.6, 1.5 Hz, 1F), −157.6 (d, J＝128.2 Hz, 1F); 13C
NMR (100.5 MHz, CDCl3, 293 K, TMS) δ: 135.5, 131.1,
128.8, 127.0, 113.2, 113.0, 64.8, 60.5, 29.6, 17.4, 15.2;
MS (EI) m/z (%): 291 (100). HRMS: Calculated for
C16H15F2O2N: 291.1071, found 291.1068.
(E)-3-(1,2-Difluoro-4-p-tolylbut-1-en-3-ynyl)-4-
isopropyloxazolidin-2-one (Table 3, 4b) 1H NMR
(300 MHz, CDCl3, 293 K, TMS) δ: 7.47－7.19 (m, 4H),
4.49－4.45 (m, 1H), 4.26－4.11 (m, 2H), 2.38 (s, 3H),
2.09－2.05 (m, 1H), 1.02－0.97 (m, 6H); 19F NMR
(282 MHz, CDCl3, 293 K, TMS) δ: −127.8 (d, J＝121.2
Hz, 1F), −149.9 (d, J＝118.4 Hz, 1F); 13C NMR (100.5
MHz, CDCl3, 293 K, TMS) δ: 154.8, 145.3, 138.6,
130.5, 128.4, 128.0, 126.2, 122.9, 102.4, 72.1, 64.9,
60.6, 29.7, 21.4, 17.5, 15.3. MS (EI) m/z (%): 305 (100).
HRMS: Calculated for C17H17F2O2N: 305.1227, found
305.1231.
(E)-4-Benzyl-3-(1,2-difluoro-4-p-tolylbut-1-en-3-
ynyl)oxazolidin-2-one (Table 3, 4f) 1H NMR (300
MHz, CDCl3, 293 K, TMS) δ: 7.42－7.17 (m, 9H),
4.41－4.34 (m, 2H), 4.21－4.18 (m, 1H), 3.23－3.18
(m, 1H), 2.88－2.82 (m, 1H), 2.38 (s, 3H); 19F NMR
(282 MHz, CDCl3, 293 K, TMS) δ: −122.7 (d, J＝181.0
Hz, 1F), −144.4 (d, J＝180.8 Hz, 1F); 13C NMR (100.5
MHz, CDCl3, 293 K, TMS) δ: 153.5, 149.1, 143.3 (dd,
J＝261.3, 51.4 Hz), 140.4, 134.3, 131.7, 131.3 (dd, J＝
230.2, 65.1 Hz), 129.3, 129.0, 127.5, 117.6, 102.6, 74.6,
68.1, 56.9, 38.9, 21.6. MS (EI) m/z (%): 353 (100).
HRMS: Calculated for C21H17F2O2N: 353.1227, found
353.1222.
(E)-4-Benzyl-3-(1,2-difluoro-4-(4-methoxyphenyl)-
but-1-en-3-ynyl)oxazolidin-2-one (Table 3, 4g) 1H
NMR (300 MHz, CDCl3, 293 K, TMS) δ: 7.47－6.87
(m, 9H), 4.37－4.34 (m, 2H), 4.21－4.18 (m, 1H), 3.68
(s, 3H), 3.23－3.18 (m, 1H), 2.88－2.82 (m, 1H); 19F
NMR (282 MHz, CDCl3, 293 K, TMS) δ: −122.7 (d,
J＝128.9 Hz, 1F), −144.4 (d, J＝130.6 Hz, 1F); 13C
NMR (100.5 MHz, CDCl3, 293 K, TMS) δ: 153.5, 149.1,
143.3 (m), 134.3, 133.5, 132.7, 131.2 (m), 129.0, 127.5,
123.9, 117.6, 102.6 (m), 74.6 (m), 68.1, 56.9, 55.8, 38.9.
MS (EI) m/z (%): 369 (100). HRMS: Calculated for
C21H17F2O3N: 369.1176, found 369.1180.
(E)-3-(1,2-Difluoro-4-(4-methoxyphenyl)but-1-en-
3-ynyl)-4-isopropyloxazolidin-2-one (Table 3, 4c)
904
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© 2013 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2013, 31, 901—907

Palladium-Catalyzed Cross-Coupling of Fluorinated Vinyl Chlorides with Terminal Alkynes
Results and Discussion
known to accelerate the oxidative-addition step for the
model reaction between chlorotrifluoroethylene and
3-phenyl-1-propyne. Surprisingly, no desired fluorinated
conjugated enyne was observed when tri-o-tolylphos-
phine (P(o-tol)3), butyl-di-1-adamantyl phosphine
(Ad2PBu), tri-tert-butylphosphine, 2-(dicyclohexyl-
phosphino)biphenyl (CyJohnPhos), 2-dicyclohexyl-
phosphino-2'-(N,N-dimethylamino)biphenyl (DavePhos)
We began our investigation by studying the stoichi-
ometric reaction of previously isolated [trans-(PPh3)2-
Pd(CF＝CF2)(Cl)][9] 1 with 3-phenyl-1-propyne under
various conditions. Heating of [trans-(PPh3)2Pd(CF＝
CF2)(Cl)] 1 with 3-phenyl-1-propyne in THF, benzene
or toluene in the present of 5 mol% CuI as additive and
1.0 equivalent of Et3N or K3PO4 as the base generated
the corresponding fluorinated enyne in less than 5%
yield. Interestingly, the yield was increased to 58%
when the reaction was conducted in benzene with 1.1
equivalent of CuI as the additive and K3PO4 as the base.
Lowering the reaction temperature to room temperature
led to higher yield (82%) (Eq. 1), possibly due to the
slowing down of the unwanted competition dimerization
of the alkyne. Since we have determined previously that
oxidative addition of chlorotrifluoroethylene to Pd(0)
occurred at 80 ℃,[6] the stoichiometric reaction indi-
cated that that oxidative-addition of chlorotrifluoro-
ethylene to Pd(0) species was much slower than those of
transmetalation and reductive-elimination steps. Thus, if
a suitable ligand can be identified to facilitate the oxida-
tive-addition of chlorotrifluoroethylene to Pd(0) spe-
cies,[8] the efficient Pd-catalyzed cross-coupling of
chlorotrifluoroethylene and terminal alkynes might be
accomplished under mild conditions.
or
2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl
(SPhos)[10] was used as the ligand when the reaction was
conducted in benzene with 1.1 equivalent of CuI as the
additive and K3PO4 as the base (Table 1, Entries 1－6).
In contrast, when triphenylphosphine was used as the
ligand, the desired product was formed in 69% yield
under otherwise identical conditions (Table 1, Entry 7).
Replacing Pd(dba)2 with Pd(OAc)2 resulted in com-
pletely shutting down the reaction (Table 1, Entry 8).
Using Pd(PPh3)2Cl2 as the catalyst formed the product
in lower 33% yield while using Pd(PPh3)4 led to much
higher 82% yield (Table 1, Entries 9 and 10). The effect
of the solvent and the base was further evaluated. Reac-
tion in THF was less efficient than those in benzene
(Table 1, Entry 11). Reaction using Et3N or i-Pr2NH as
the base was not effective at all (Table 1, Entries 12 and
13). When the amount of CuI was reduced to 20 mol%,
the yield of the fluorinated conjugated enyne was de-
creased to 20 mol% (Table 1, Entry 14). Interestingly,
the yield was significantly improved to 87% when 20
mol% of Bu3N was used as an additive and a mixed
solvent of benzene/water (3/1, V/V) was used (Table 1,
Entries 15－17). Reaction in a mixed solvent of tolu-
ene/water under otherwise same conditions gave the
product in 85% yield (Table 1, Entry 18). It is likely that
the presence of water increased the solubility of K3PO4
that facilitated the transmetalation step of the catalytic
cycle.[11]
F
F
F
F
F
F
1.1 equiv. CuI
+
(1)
Bn
Bn
H
Ph3P Pd PPh3
K3PO4
Benzene
r.t., 10 h
82%
Cl
1
Guided by these stoichiometric investigations, we first
examined various supporting ligands, especially those
Table 1 Optimization for Pd-catalyzed coupling of chlorotrifluoroethylene with 3-phenyl-1-propynea
Pd/L
CuI
F
F
F
F
F
F
+
Bn
H
Base, solvent
80 oC, 10 h
Cl
Bn
Entry
Pd source
Ligand
Solvent
CuI
Base
Yieldb/%
－
1
2
Pd(dba)2
Pd(dba)2
Pd(dba)2
Pd(dba)2
Pd(dba)2
Pd(dba)2
Pd(dba)2
Pd(OAc)2
Pd(PPh3)4
Pd(PPh3)2Cl2
P(oTol)3
Ad2PBu
t-Bu3P
CyJohnPhos
DavePhos
SPhos
PPh3
Benzene
Benzene
Benzene
Benzene
Benzene
Benzene
Benzene
Benzene
Benzene
Benzene
1.1 equiv.
1.1 equiv.
1.1 equiv.
1.1 equiv.
1.1 equiv.
1.1 equiv.
1.1 equiv.
1.1 equiv.
1.1 equiv.
1.1 equiv.
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
－
－
3
－
4
－
5
－
6
7
69
8
PPh3
－
9
－
82
－
10
33
Chin. J. Chem. 2013, 31, 901—907
© 2013 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
905

Chen et al.
FULL PAPER
Continued
Yieldb/%
Entry
Pd source
Ligand
－
Solvent
THF
CuI
Base
K3PO4
11
12
13
14
15
16
17
18
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
1.1 equiv.
1.1 equiv.
1.1 equiv.
10 mol%
10 mol%
10 mol%
10 mol%
10 mol%
52
－
－
－
Benzene
Et3N
－
Benzene
i-Pr2NH
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
－
Benzene
20
－
Benzene/H2O (5/1)
Benzene/H2O (3/1)
Benzene/H2O (1/1)
Toluene/H2O (3/1)
43c
87c
71c
85c
－
－
－
a Reaction conditions: 3-phenyl-1-propyne (1.0 mmol), excess chlorotrifluoroethylene, palladium precursor (10 mol%), ligand (20 mol%),
base (3.0 mmol) in 2.0 mL solvent. b The yield was determined by 19F NMR spectroscopy with fluorobezene as an internal standard. c 20
mol% Bu3N was added as additive.
Table 2 Scope of Pd-catalyzed coupling of chlorotrifluoro-
The scope of Sonogashira reaction of a variety of
alkynes with chlorotrifluoroethylene in the presence of
palladium catalyst and CuI as additive is shown in Table
2. A wide range of alkynes were readily converted to the
corresponding fluorinated conjugated enynes in moder-
ate to excellent yields. Reactions of both electron-rich
and electron-poor aryl substituted alkynes gave the cor-
responding products in good to excellent yields (Table 2,
2a－2m). It was found that the reaction conditions were
compatible with various functional groups such as ester,
amine, cyano group (Table 2, 2f, 2g, 2i and 2n). Notably,
2- or 3-chlorophenylethyne also coupled with chloro-
trifluoroethylene to give the corresponding enynes in
65% and 61% yield, respectively (Table 2, Entries 2i
and 2j), which indicated that C－Cl bond in chloro-
trifluoroethylene is more reactive than those in aryl
chlorides that has been observed in the palladium-cata-
lyzed Suzuki-coupling of chlorotrifluoroethylene with
aryl boronic acids. The presence of chloride in the
products is very useful for further synthetic manipula-
tions. Reaction of heteroaryl alkyne such as 2-thiophe-
nylethyne occurred smoothly to give the corresponding
product in 48% yield (Table 2, 2l). Reactions of alkyl
alkynes generated the corresponding enynes in excellent
yields (Table 2, 2n and 2o).
ethylene with alkynesa,b
10 mol% Pd(PPh3)4
10 mol% CuI
20 mol% Bu3N
F
F
F
F
F
F
R
+
3.0 equiv. K3PO4
benzene/H2O (3/1)
80 oC, 10 h
Cl
R
2a - 2o
F
F
F
F
F
F
R
F
F
F
R
R
R = Cl, 61%, 2jc
NH2, 78%, 2k
R = F, 78%, 2h
Cl, 65%, 2ic
R = F, 81%, 2a
Me, 86%, 2b
F
F
n-Pr, 84%, 2c
t-Bu, 88%, 2d
OMe, 88%, 2e
CN, 78%, 2f
F
F
S
F
F
PhCO2
CO2Me, 38%, 2gc
82%, 2n
48%, 2lc
F
F
F
F
F
F
To further expand the scope of the reaction, we fur-
ther studied the reaction of (R,Z)-3-(2-chloro-1,2-di-
fluorovinyl)-4-alkyloxazolidin-2-one (3a and 3b) with
alkynes. After careful investigation of various reaction
parameters, it was found that reaction of compound 3a
with phenylacetylene occurred smoothly to give the
coupled product in 64% yield when 10 mol% of
Pd(PPh3)2Cl2 was used as the catalyst, 20 mol% of CuI
was used as cocatalyst and Et3N was used as base in
DMSO. A variety of aryl alkynes were subjected to the
catalytic conditions to give the product in moderate to
good yield, as summarized in Table 4. In general, these
reactions were faster than those of chlorotrifluoroethyl-
ene and the reaction typically required 10 h at 45 ℃. At
higher temperature, the yields dropped significantly.
MeO
Bn
55%, 2mc
82%, 2o
a Reaction conditions: alkyne (1.0 mmol), excess chlorotrifluoro-
ethylene, Pd(PPh3)4 (10 mol%), CuI (10 mol%), n-Bu3N (20
mol%), K3PO4 (3.0 mmol) in 2.0 mL of benzene/H2O (3/1) at 80
℃ for 10 h. b Isolated yields. c 1.0 equivalent of CuI was used.
Conclusions
In summary, an efficient and cost-effective method
for the preparation of fluorinated conjugated enynes has
been successfully developed. The method was compati-
ble with a variety of functional groups such as chloride,
amine, cyano and ester group. The method could also be
extended to the coupling of (R,Z)-3-(2-chloro-1,2-di-
906
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© 2013 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2013, 31, 901—907

Palladium-Catalyzed Cross-Coupling of Fluorinated Vinyl Chlorides with Terminal Alkynes
Table 3 Scope of Pd-catalyzed coupling of (R,Z)-3-(2-chloro-
1,2-difluorovinyl)-4-alkyloxazolidin-2-one 3 with alkynesa,b
21032006), National Natural Science Foundation of
China (Nos. 21172245, 21172244, B020304), Agro-
scientific Research in the Public Interest (No.
201103007), the National Key Technologies R&D Pro-
gram (No. 2011BAE06B05), Shanghai Scientific Re-
search Program (No. 10XD1405200), and SIOC.
F
O
10 mol% Pd(PPh3)2Cl2
20 mol% CuI
Cl
N
+
R'
H
O
F
NEt3 (1.0 equiv.)
DMSO
45 oC, 10 h
R
R = i-Pr, 3a
Bn, 3b
References
R'
F
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O
N
O
F
R
4
R''
Me
F
O
F
O
N
N
O
F
O
F
i-Pr
i-Pr
59%, 4d
R'' = H, 64%, 4a
Me, 58%, 4b
R''
OMe, 66%, 4c
F
MeO
O
N
O
F
F
O
O
Bn
N
F
i-Pr
R'' = Me, 66%, 4f
OMe, 63%, 4g
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59%, 4e
a Reaction conditions: alkyne (1.2 mmol), (R,Z)-3-(2-chloro-1,2-
difluorovinyl)-4-alkyloxazolidin-2-one (3) (1.0 mmol), Pd(PPh3)2-
Cl2 (10 mol%), CuI (10 mol%), Et3N (20 mol%) in 2.0 mL of
DMSO at 45 ℃ for 10 h. b Isolated yields.
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fluorovinyl)-4-alkyloxazolidin-2-one (3) with moderate
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the reaction and to further explore the reactivity of
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Acknowledgement
The authors gratefully acknowledge the financial
support from National Basic Research Program of
China (Nos. 2012CB821600, 2010CB126103), the Key
Program of Natural Science Foundation of China (No.
(Pan, B.; Qin, X.)
Chin. J. Chem. 2013, 31, 901—907
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