Pd-catalyzed cross-coupling of polyfluoroarenes with cyclic vinyl triflates

Article abstract of DOI:10.1007/s11426-013-5024-4

An effective method for Pd-catalyzed cross-coupling between polyfluoroarenes and cyclic vinyl triflates has been developed. This protocol provides a useful and facile access to polyfluoroarylated cyclic alkenes that are difficult to prepare otherwise. The advantages of this method are its high efficiency and operational simplicity.

Full text of DOI:10.1007/s11426-013-5024-4

SCIENCE CHINA
Chemistry
February 2014 Vol.57 No.2: 276–281
doi: 10.1007/s11426-013-5024-4
• ARTICLES •
· SPECIAL ISSUE · The Frontiers of Chemical Biology and Synthesis
Pd-catalyzed cross-coupling of polyfluoroarenes with cyclic vinyl
triflates
YU YanBo1, WANG Zhen2 & ZHANG XinGang1*
1Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032,
China
2College of Agriculture, Inner Mongolia Agricultural University, Hohhot 010019, China
Received August 30, 2013; accepted September 20, 2013; published online December 16, 2013
An effective method for Pd-catalyzed cross-coupling between polyfluoroarenes and cyclic vinyl triflates has been developed.
This protocol provides a useful and facile access to polyfluoroarylated cyclic alkenes that are difficult to prepare otherwise.
The advantages of this method are its high efficiency and operational simplicity.
CH bond functionalization, cyclic vinyl triflates, palladium, polyfluoroarenes
reported so far. Continuing our study in palladium-catalyzed
1 Introduction
polyfluoroarene chemistry [5], herein, we report an effec-
tive method for the preparation of polyfluoroarylated cyclic
alkenes catalyzed by palladium. The reaction is made possi-
ble by using cyclic vinyl triflates, which can be easily ac-
cessed through the reactions of widely available enolates
with trifluoromethansesulfonyl reagents [6], thus providing
a useful access to polyfluoroarylated derivatives of interest
in both life and material sciences (Scheme 1).
It is of great synthetic interest to develop efficient methods
to introduce various polyfluoroaryl groups into organic
molecules owing to their importance in many functional
molecules, such as pharmaceuticals, agrochemicals, liquid
crystals, and electronic devices [1]. Traditionally, such val-
uable structural motif can be prepared from prefunctional-
ized polyfluoroarenes, such as polyfluoroaryl metals [2].
However, this “prefunctionalization” process suffers from
tedious procedures in preparing the organometallic reagents
and the incompatibility of important functional groups.
From the point of view of synthetic simplicity, the use of
readily and commercially available polyfluoroarenes as
starting materials would facilitate the accessibility of this
fluorinated structure through direct CH bond functionali-
zation [3]. Recently, impressive progresses have been
achieved in this area [4, 5]. However, examples for the
preparation of polyfluoroarylated alkenes remain few. In
particular, the transition-metal-catalyzed direct olefination
of polyfluoroarenes with cyclic vinyl triflates has not been
Scheme 1 Pd-catalyzed cross-coupling of polyfluoroarenes with cyclic
vinyl triflates.
2 Experimental
2.1 Materials and methods
*Corresponding author (email: xgzhang@mail.sioc.ac.cn)
All reagents were used as received from commercial
© Science China Press and Springer-Verlag Berlin Heidelberg 2013
chem.scichina.com link.springer.com

Yu YB, et al. Sci China Chem February (2014) Vol.57 No.2
277
sources, unless otherwise specified, or prepared as de-
scribed in the literature. All reagents were weighed and
handled in air, and refilled with an inert atmosphere of N2 at
room temperature. DMF, DMSO were distilled under re-
duced pressure from CaH2. Toluene, and 1,4-dioxane were
distilled from sodium and benzophenone immediately be-
fore use.
in THF, 11 mL, 1.1 equiv) was added dropwise to a solution
of a ketone (10 mmol, 1.0 equiv) and PhNTf2 (1.1 equiv) in
THF (0.15 M) at 78 °C. The reaction mixture was allowed
to warm slowly to room temperature and stirred until the
reaction was complete. The reaction was quenched with
saturated aqueous NaHCO3 and extracted with Et2O. The
combined organic layers were washed with brine, dried over
anhydrous MgSO4, filtered, and concentrated. The resulting
residue was purified by flash column chromatography.
1,2,3,6-Tetrahydro-[1,1′-biphenyl]-4-yl trifluoromethane-
sulfonate (2d). Colorless oil (75% yield). This compound is
known [9]. H NMR (300 MHz, CDCl3) δ 7.357.21 (m,
5H), 5.905.78 (m, 1H), 2.892.82 (m, 1H), 2.592.29 (m,
4H), 2.10–1.89 (m, 2H).
1-Pivaloyl-1,2,3,6-tetrahydropyridin-4-yl trifluoromethan-
esulfonate (2e). Colorless oil (68% yield). This compound is
known [9]. 1H NMR (400 MHz, CDCl3) δ 5.82 (s, 1H), 4.23
(d, J = 2.8 Hz, 2H), 3.82 (t, J = 5.6 Hz, 2H), 2.49 (s, 2H),
1.30 (s, 9H).
1H NMR and 13C NMR spectra were recorded on a
Bruker AM300 and AM400 spectrometer. 19F NMR was
recorded on a Bruker AM300 and AM400 spectrometer
(CFCl3 as outside standard and low field is positive).
Chemical shifts (δ) are reported in ppm, and coupling con-
stants (J) are in Hertz (Hz). The following abbreviations
were used to explain the multiplicities: s = singlet, d = dou-
blet, t = triplet, q = quartet, m = multiplet, br = broad. NMR
yield was determined by 19F NMR using fluorobenzene as
an internal standard before working up the reaction.
1
2.2 Synthesis of cyclic vinyl triflates
Vinyl triflates 2a, 2b, and 2c were prepared from the corre-
sponding ketones and trifluoromethanesulphonic anhydride
according to the literature procedure [7].
2.3 General procedure for Pd-catalyzed cross-coupling
of polyfluoroarenes with cyclic vinyl triflate
To a Schlenck tube with a magnetic stir bar were added
Pd(OAc)2 (5 mol%), SPhos or DavePhos (5 mol%), AdOH
(0.1 equiv), K2CO3 (1.2 equiv) under N2, followed by DMF
(2.5 mL) with stirring. Polyfluoroarene (1.2 mmol, 2.0
equiv) and vinyl triflate (0.6 mmol, 1 equiv) were added
subsequently. The Schlenck tube was sealed and stirred in
an oil bath (80 °C) for 8 h. The reaction mixture was al-
lowed to cool to room temperature and diluted with ethyl
acetate, washed with brine, dried over Na2SO4, filtered and
concentrated. The residue was purified with silica gel
chromatography (petroleum ether) to provide pure product.
Typical procedure for the synthesis of cyclic triflates 2a
Under argon, a solution of 3,4-dihydronaphthalen-1(2H)-
one (1.46 g, 10.0 mmol) in 200 mL of dry dichloromethane
was cooled to 0 °C, sodium carbonate (2.12 g, 20.0 mmol)
and trifluoromethanesulphonic anhydride 4.51 g, 16.0 mmol)
were then added subsequently to the stirred solution. After
the addition, the resulting reaction mixture was warmed up
to 25 °C and stirred for 5 h until the ketone was fully con-
sumed (monitored by TLC). The reaction mixture was
quenched by ice water, diluted with ethyl acetate, washed
with brine, dried over Na2SO4, filtered and concentrated.
The residue was purified with silica gel chromatography
(petroleum ether) to provide pure product 2a (2.5 g, 90%) as
4-(Perfluorophenyl)-1,2-dihydronaphthalene (3a)
White solid (155 mg, 87%). m.p. 85 °C. 1H NMR (400 MHz,
CDCl3) δ 7.307.05 (m, 3H), 6.66 (d, J = 7.5 Hz, 1H), 6.16
(t, J = 4.4 Hz, 1H), 2.91 (t, J = 8.1 Hz, 2H), 2.592.42 (m,
2H). 19F NMR (376 MHz, CDCl3) δ 140.6 (dd, J = 22.2,
6.7 Hz, 2F), 156.2 (td, J = 20.9, 4.1 Hz, 1F), 156.7 (m,
2F). 13C NMR (100 MHz, CDCl3) δ 144.2 (dm, J = 243.3
Hz), 140.1 (dm, J = 253.3 Hz), 137.2 (dm, J = 252.5 Hz),
135.1, 133.3, 132.4, 127.5, 127.4, 126.2, 124.5, 123.2,
114.0 (m), 27.0, 23.1. IR (thin film) max 1493, 1106, 987
cm1. MS (EI): m/z (%) 296 (M+, 100), 297 (MH+), 281.
HRMS: Calculated for C16H9F5: 296.0624; found: 296.0625.
1
a colorless oil. This compound is known [7]. H NMR (400
MHz, CDCl3) δ 7.377.10 (m, 4H), 5.99 (t, J = 4.7 Hz, 1H),
2.84 (t, J = 8.1 Hz, 2H), 2.502.45 (m, 2H) (Supporting
Information online).
5-Methoxy-3,4-dihydronaphthalen-1-yl trifluoromethan-
esulfonate (2b). Colorless oil (85% yield). This compound
1
is known [8]. H NMR (300 MHz, CDCl3) δ 7.257.20 (m,
1H), 7.106.98 (m, 1H), 6.896.86 (m, 1H), 6.00 (t, J = 4.6
Hz, 1H), 3.83 (s, 3H), 2.85 (t, J = 8.4 Hz, 2H), 2.512.44
(m, 2H).
Cyclohex-1-en-1-yl trifluoromethanesulfonate (2c). Col-
orless oil (75% yield). This compound is known [9]. H
1
NMR (400 MHz, CDCl3) δ 5.815.72 (m, 1H), 2.372.26
(m, 2H), 2.232.12 (m, 2H), 1.78 (m, 2H), 1.60 (m, 2H).
Vinyl triflates 2d and 2e were prepared from the corre-
sponding ketones and PhNTf2 according to the literature
procedure [9]. Under argon, a solution of NaHMDS (1.0 M
8-Methoxy-4-(perfluorophenyl)-1,2-dihydronaphthalene (3b)
White solid (168 mg, 86%). m.p. 66 °C. 1H NMR (400 MHz,
CDCl3) δ 7.05 (t, J = 8.0 Hz, 1H), 6.80 (d, J = 8.2 Hz, 1H),
6.31 (d, J = 7.6 Hz, 1H), 6.15 (t, J = 4.2 Hz, 1H), 3.83 (s,
3H), 2.90 (t, J = 8.3 Hz, 2H), 2.52–2.40 (m, 2H). 19F NMR

278
Yu YB, et al. Sci China Chem February (2014) Vol.57 No.2
2,2-Dimethyl-1-[4-(perfluorophenyl)-5,6-dihydropyridin-1
(2H)-yl]propan-1-one (3f)
(376 MHz, CDCl3) δ 140.2 (dd, J = 23.2, 8.2 Hz, 2F),
156.0 (t, J = 20.8 Hz, 1F), 162.5 (td, J = 23.0, 8.4 Hz, 2F).
13C NMR (100 MHz, CDCl3) δ 156.3, 144.7 (dm, J = 243.2
Hz), 140.5 (dm, J = 253.1 Hz), 137.6 (dm, J = 252.0 Hz),
134.1, 133.8, 126.7, 124.8, 123.5, 116.5, 114.8 (m), 110.4,
55.5, 23.0, 19.2. IR (thin film) max 2839, 1496, 989 cm1.
MS (EI): m/z (%) 326 (M+, 100), 327 (MH+), 311. HRMS:
Calculated for C17H11OF5: 326.0730; found: 326.0726.
White solid (162 mg, 81%). m.p. 45 °C. 1H NMR (400 MHz,
CDCl3) δ 5.91 (s, 1H), 4.25 (s, 2H), 3.83 (s, 2H), 2.42 (s,
2H), 1.30 (s, 9H). 19F NMR (376 MHz, CDCl3) δ 142.2 (d,
J = 16.5 Hz, 2F), 156.1 (t, J = 20.6 Hz, 1F), 162.3 (t, J =
18.0 Hz, 2F). 13C NMR (101 MHz, CDCl3) δ 176.7, 144.0
(dm, J = 246.9 Hz), 140.1 (dm, J = 253.7 Hz), 137.6 (dm, J
= 255.8 Hz), 129.8, 123.4, 115.7 (m), 44.7, 42.6, 38.7, 29.1,
28.1. IR (thin film) max 2976, 1632, 1492 cm1. MS (EI):
m/z (%) 333 (M+, 100), 334 (MH+), 84. HRMS: Calculated
for C16H16NOF5: 333.1152; found: 333.1154.
4-(2,3,5,6-Tetrafluoro-4-methoxyphenyl)-1,2-dihydronaphtha-
lene (3c)
White solid (153 mg, 83%). m.p. 79 °C. 1H NMR (400 MHz,
CDCl3) δ 7.287.05 (m, 3H), 6.71 (d, J = 7.2 Hz, 1H), 6.15
(m, 1H), 4.11 (s, 3H), 2.90 (t, J = 8.0 Hz, 2H), 2.49 (m, 2H).
19F NMR (376 MHz, CDCl3) δ 142.0 (dd, J = 22.3, 8.7 Hz,
2F), 158.2 (dd, J = 22.4, 8.7 Hz, 2F). 13C NMR (100 MHz,
CDCl3) δ 144.8 (dm, J = 245.1 Hz), 141.0 (dm, J = 247.4
Hz), 137.5 (m), 135.6, 133.3, 133.2, 127.8, 127.6, 126.6,
125.5, 123.8, 112.7 (m), 62.2, 27.5, 23.5. IR (thin film) max
2834, 1483, 982 cm1. MS (EI): m/z (%) 308 (M+, 100), 309
(MH+), 293. HRMS: Calculated for C17H12OF4: 308.0824;
found: 308.0829.
2,2-Dimethyl-1-[4-(2,3,5,6-tetrafluoro-4-methoxyphenyl)-5,
6-dihydropyridin-1(2H)-yl]propan-1-one (3g)
White solid (145 mg, 70%). m.p. 84 °C. 1H NMR (400 MHz,
CDCl3) δ 5.91 (s, 1H), 4.27 (s, 2H), 4.08 (s, 3H), 3.84 (t, J =
5.1 Hz, 2H), 2.45 (s, 2H), 1.33 (s, 9H). 19F NMR (376 MHz,
CDCl3) δ 143.9 (dd, J = 21.9, 8.0 Hz, 2F), 158.3 (dd, J =
21.8, 7.0 Hz, 2F). 13C NMR (100 MHz, CDCl3) δ 176.7,
144.2 (dm, J = 245.3 Hz), 140.9 (dm, J = 247.2 Hz), 137.2
(m), 129.0, 124.0, 114.1 (t, J = 17.9 Hz), 62.1, 44.7, 42.7,
38.7, 29.1, 28.1. IR (thin film) max 2978, 1621, 1075 cm1.
MS (EI): m/z (%) 345 (M+, 100), 346 (MH+), 330. HRMS:
Calculated for C17H19NO2F4: 345.1352; found: 345.1350.
4-[2,3,5,6-Tetrafluoro-4-(trifluoromethyl)phenyl]-1,2-
dihydronaphthalene (3d)
Colorless oil (172 mg, 85%). 1H NMR (300 MHz, CDCl3) δ
7.217.20 (m, 2H), 7.177.10 (m, 1H), 6.66 (d, J = 7.4 Hz,
1H), 6.21 (t, J = 4.4 Hz, 1H), 2.92 (t, J = 8.1 Hz, 2H),
2.562.49 (m, 2H). 19F NMR (282 MHz, CDCl3 ) δ 56.6 (t,
J = 21.6 Hz, 3F), 138.4 (td, J = 15.9, 5.9 Hz, 2F), 141.1
(td, J = 20.9, 10.8 Hz, 2F). 13C NMR (100 MHz, CDCl3) δ
144.7 (dm, J = 247.9 Hz), 144.1 (dm, J = 260.2 Hz), 135.5,
134.1, 132.2, 128.0, 126.7, 125.1, 123.9 (t, J = 19.0 Hz),
123.6, 119.6 (q, J = 275.3 Hz), 108.7 (m), 27.3, 23.5. IR
(thin film) max 1479, 1340, 989 cm1. MS (EI): m/z (%) 346
(M+, 100), 347 (MH+), 331. HRMS: Calculated for C17H9F7:
346.0592; found: 346.0596.
2',3',4',5',6'-Pentafluoro-2,3,4,5-tetrahydro-1,1'-biphenyl (3h)
Colorless oil (91mg, 61%). This compound is known [10].
1H NMR (400 MHz, CDCl3) δ 5.85 (s, 1H), 2.272.17 (m,
4H), 1.831.75 (m, 2H), 1.71 (dd, J = 7.3, 3.2 Hz, 2H). 19
NMR (376 MHz, CDCl3) δ 142.8 (dd, J = 23.1, 8.0 Hz,
2F), 157.9 (t, J = 20.9 Hz, 1F), 163.3 (dt, J = 23.1, 8.2 Hz,
2F). 13C NMR (100 MHz, CDCl3) δ 145.8 (dm, J = 256.2
Hz), 141.4 (dm, J = 250.5 Hz), 139.2 (dm, J = 246.7 Hz),
134.5, 126.3, 119.8 (m), 30.4, 27.2, 24.3, 23.3.
F
8-Methoxy-4-[2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenyl]-
2',3',5',6'-Tetrafluoro-4'-(trifluoromethyl)-2,3,4,5-tetrahydro-
1,1'-biphenyl (3i)
1,2-dihydronaphthalene (3e)
White solid (133 mg, 59%). m.p. 83 °C. 1H NMR (400 MHz,
CDCl3) δ 7.07 (t, J = 8.0 Hz, 1H), 6.82 (d, J = 8.2 Hz, 1H),
6.31 (d, J = 7.6 Hz, 1H), 6.20 (t, J = 4.4 Hz, 1H), 3.84 (s,
3H), 2.92 (t, J = 8.3 Hz, 2H), 2.49 (td, J = 8.3, 4.8 Hz, 2H).
19F NMR (376 MHz, CDCl3) δ 56.3 (t, J = 21.7 Hz, 3F),
138.2 (m, 2F), 141.0 (td, J = 21.0, 11.0 Hz, 2F). 13C
NMR (100 MHz, CDCl3) δ 155.9, 144.4 (dm, J = 249.6 Hz),
143.7 (dm, J = 260.2), 133.9, 132.7, 126.4, 124.5, 123.8 (t,
J = 18.8 Hz), 123.0, 120.5 (q, J = 274.4 Hz), 115.9, 110.2,
108.2 (m), 55.1, 22.5, 18.7. IR (thin film) max 2957, 1471,
1337 cm1. MS (EI): m/z (%) 376 (M+, 100), 377 (MH+),
361. HRMS: Calculated for C18H11OF7: 376.0698; found:
376.0698.
White solid (132 mg, 74%). m.p. 39 °C. 1H NMR (400 MHz,
CDCl3) δ 5.94 (s, 1H), 2.26 (s, 4H), 1.76 (m, 4H). 19F NMR
(376 MHz, CDCl3) δ 56.4 (t, J = 21.5 Hz, 3F), 140.4 (m,
2F), 141.7 (td, J = 20.5, 10.3 Hz, 2F). 13C NMR (100 MHz,
CDCl3) δ 144.1 (dm, J = 259.5 Hz), 133.8, 127.3 (t, J = 18.1
Hz), 124.8, 120.9 (q, J = 274.2 Hz), 107.1 (m), 28.2, 25.5,
22.4, 21.4. IR (thin film) max 2924, 1334, 1148 cm1. MS
(EI): m/z (%) 298 (M+), 299 (MH+), 283 (M+, 100). HRMS:
Calculated for C13H9F7: 298.0592; found: 298.0587. Anal.
Calcd. for C13H9F7: C, 53.36, H, 3.04; found: C, 53.18; H,
3.26.

Yu YB, et al. Sci China Chem February (2014) Vol.57 No.2
279
2'',3'',4'',5'',6''-Pentafluoro-1',2',3',6'-tetrahydro-1,1':4',1''-
1620). To our delight, when bulky 1-adamantanecarbox-
ylic acid (AdOH) was used as an additive, an improved
yield was obtained (Table 1, entries 1920). It has been
demonstrated that phosphine-ligated arylpalladium carbox-
ylates LPd(Ar)(OCOR) typically reacted with arenes to
form biarylpalladium complexes through a concerted
metallation-deprotonation (CMD) pathway [11b]. We sup-
posed that AdOH may function as a proton shuttle during
the pentafluorobenzene CH cleavage step [11a], as a result,
a higher yield was observed. Further optimization of the
reaction conditions led to the highest yield (87% isolated
yield) by reducing the amount loading of Pd(OAc)2 to 5
mol%, along with utilization of 5 mol% of SPhos, 1.2 equiv
of K2CO3, and 0.1 equiv of AdOH (Table 1, entry 22).
terphenyl (3j)
1
White solid (175 mg, 90%). m.p. 162 °C. H NMR (400
MHz, CDCl3) δ 7.397.18 (m, 5H), 5.96 (s, 1H), 3.022.87
(m, 1H), 2.53 (m, 2H), 2.442.24 (m, 2H), 2.08 (m, 1H),
1.95 (m, 1H). 19F NMR (376 MHz, CDCl3) δ 142.5 (dd,
J = 23.2, 8.0 Hz, 2F), 157.3 (t, J = 20.9 Hz, 1F), 162.9 (td,
J = 22.9, 8.1 Hz, 1F). 13C NMR (100 MHz, CDCl3) δ 148.0,
146.0 (dm, J = 258.2 Hz), 142.0 (dm, J = 251.4 Hz), 139.3
(dm, J = 259.5 Hz), 134.2, 130.2, 128.6, 128.0, 126.4,
119.4(m), 40.9, 35.4, 31.5, 31.0. IR (thin film) max 2920,
1488, 983 cm1. MS (EI): m/z (%) 324 (M+, 100), 325
(MH+), 104. HRMS: Calculated for C18H13F5: 324.0937;
Found: 324.0935. Anal. Calcd. for C18H13F5: C, 66.67, H,
4.04; Found: C, 66.63; H, 4.05.
With the optimized reaction conditions in hand, the sub-
strate scope of the cross-coupling of polyfluoroarenes with
cyclic vinyl triflates was investigated, and the representative
2'',3'',5'',6''-Tetrafluoro-4''-methoxy-1',2',3',6'-tetrahydro-1,
1':4',1''-terphenyl (3k)
1
White solid (105 mg, 52%). m.p. 126 °C. H NMR (400
Table 1 Optimization of Pd-catalyzed cross-coupling of pentafluoroben-
zene 1a with vinyl triflate 2a a)
MHz, CDCl3) δ 7.497.04 (m, 5H), 5.93 (s, 1H), 4.04 (s,
2H), 2.92 (s, 1H), 2.48 (s, 2H), 2.33 (m, 2H), 2.191.84 (m,
3H). 19F NMR (376 MHz, CDCl3) δ 144.2 (dd, J = 22.3,
8.5 Hz, 2F), 158.7 (dd, J = 22.3, 8.4 Hz, 2F). 13C NMR
(100 MHz, CDCl3) δ 146.4, 144.3 (dm, J = 244.2 Hz), 140.9
(dm, J = 246.7 Hz), 137.2 (m), 131.7, 128.5, 126.9, 126.2,
125.3, 116.2 (m), 62.1, 39.3, 33.7, 29.8, 29.4. IR (thin film)
max 2935, 1482, 1073 cm1. MS (EI): m/z (%) 336 (M+,
100), 337 (MH+), 232 (M+, 100). HRMS: Calculated for
C19H16OF4: 336.1137; found: 336.1133.
Base
(equiv)
Entry x mol%
L, y mol%
Additive
Yield b)
1
2
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
5
PPh3, 20
K2CO3, 1.2
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
Trace
52
MePhos, 20 K2CO3, 1.2
3
RuPhos, 20
SPhos, 20
K2CO3, 1.2
K2CO3, 1.2
70
4
72 (66)
trace
18
3 Results and discussion
5
XantPhos, 10 K2CO3, 1.2
6
BINAP, 10
SPhos, 20
SPhos, 20
SPhos, 20
SPhos, 20
SPhos, 20
SPhos, 20
SPhos, 20
SPhos, 20
SPhos, 20
SPhos, 20
SPhos, 20
SPhos, 20
SPhos, 20
SPhos, 20
SPhos, 10
SPhos, 5
K2CO3, 1.2
NaOAc, 1.2
K3PO4, 1.2
KOAc, 1.2
tBuOLi, 1.2
tBuONa, 1.2
tBuOK, 1.2
K2CO3, 1.2
K2CO3, 1.2
K2CO3, 1.2
We began this study by choosing pentafluorobenzene 1a
and 1-tetralone derived 3,4-dihydronaphthalen-1-yl trifluo-
romethanesulfonate 2a as model substrates. Initially, a neg-
ative result was obtained when the reaction was carried out
with Pd(OAc)2 (10 mol%), PPh3 (20 mol%), and K2CO3 (1.2
equiv) in DMF at 80 °C (Table 1, entry 1). After a survey of
different phosphane ligands (Table 1, entries 26), SPhos
was found to be the optimal one, providing 3a in 66% iso-
lated yield without observation of homocoupling of 1a (Ta-
ble 1, entry 4). Other ligands, such as MePhos, Xantphos,
and BINAP, showed less or no effectiveness. Encouraged
by these results, different bases and solvents were examined
to further improve the reaction efficiency (Table 1, entries
715). It turned out that K2CO3 and DMF remained to be
the best choice. Stronger bases did not facilitate the reaction
(Table 1, entries 1012), and 20% yield of defluorinated
side product was observed when tBuOK was used (Table 1,
entry 12). Carboxylic acid was reported to have a beneficial
effect on the CH bond activation of simple arenes [11],
thus a series of carboxylic acids were tested (Table 1, entries
7
64
8
63
9
12
10
11
12
13 d)
14 e)
15 f)
16
17
18
19
20
21
22
20
18
50 c)
trace
30
50
K2CO3, 2.4 PivOH 1.2
K2CO3, 2.4 PhCO2H 1.2
K2CO3, 2.4 HOAc 1.2
K2CO3, 2.4 AdOH 1.2
K2CO3, 1.2 AdOH 0.1
K2CO3, 1.2 AdOH 0.1
K2CO3, 1.2 AdOH 0.1
57
80
72
84
84 (82)
82 (80)
90 (87)
5
a) Conditions (unless otherwise specified): 1a (0.6 mmol) and 2a (0.3
mmol) in solvent (2.0 mL), 8 h; b) NMR yield determined by 19F NMR
using fluorobenzene as the internal standard and number in parentheses is
isolated yield; c) 20% yield of defluorinated side product was observed; d)
using DMSO as solvent; e) using toluene as solvent; f) using dioxane as
solvent.

280
Yu YB, et al. Sci China Chem February (2014) Vol.57 No.2
results were illustrated in Table 2. Generally, the standard
reaction conditions were quite suitable for 1-tetralone de-
rived substrate (3b) and different polyfluoroarenes (3ce).
Fluoroarenes bearing either electron-donating group or
electron-withdrawing group, such as 1,2,4,5-tetrafluoro-3-
(trifluoromethyl)benzene and 1,2,4,5-tetrafluoro-3-methoxy-
benzene, all furnished their corresponding products smoothly
when 1-tetralone derived triflates were used as substrates.
Apart from conjugated vinyl triflates, substrate bearing am-
ide group derived from 4-piperidinone also reacted smooth-
ly with polyfluoroarenes in good yields (3fg). However,
this standard reaction condition was not applicable to cy-
clohexenyl triflate. To address this issue, different phos-
phane ligands were screened. We were pleased to find that a
satisfying yield was provided when DavePhos was em-
ployed as a ligand (3h). Under such modified reaction con-
ditions, other fluoroarenes and cyclohexenyl triflates were
all suitable substrates (3ik). It is noteworthy that an excel-
lent yield was obtained when 4-phenyl cyclohexenyl triflate
was tested (3j). However, five-membered cyclic vinyl sub-
strates failed to provide desired products due to the decom-
position of these triflates [9].
Table 2 Pd-catalyzed direct cross-coupling of polyfluoroarenes with
cyclic vinyl triflates a)
On the basis of the results reported by others [11] and us
[5f], a plausible mechanism is proposed and shown in
Scheme 2. An oxidative addition of cyclic vinyl triflates to a
zero valent Pd species is envisioned to take place as an ini-
tial step, leading to a Pd-vinyl intermediate I. I subsequent-
ly undergoes ligand exchange with 1-adamantanecarbox-
ylate (II) to form III, which reacts with polyfluoroarenes
through the concerted-metallation-deprotonation (CMD)
process [11] to generate the key intermediate V. As the final
step of the catalytic cycle, reductive elimination of V pro-
duces polyfluoroarylated cyclic alkenes along with the re-
generation of Pd(0) species.
Scheme 2 Plausible mechanism of the Pd-catalyzed cross-coupling of
polyfluoroarenes with cyclic vinyl triflates.
4 Conclusions
In summary, we have developed an effective and straight-
forward method for Pd-catalyzed cross-coupling of
polyfluoroarenes with cyclic vinyl triflates. This method
allows the conversion of easily accessible cyclic vinyl tri-
flates to polyfluoroarylated derivatives of interest in both
life and material science.
a) Conditions (unless otherwise specified): 1a (0.6 mmol), 2a (0.3
mmol), Pd(OAc)2 (5 mol%), SPhos (5 mol%), AdOH (0.1 equiv) and
K2CO3 (1.2 equiv) in DMF 2.0 mL, 8 h. All yields are of the isolated prod-
ucts. b) Use DavePhos as ligand.

Yu YB, et al. Sci China Chem February (2014) Vol.57 No.2
281
This work was financially supported by the National Basic Research Pro-
gram of China (973 Program, 2012CB821600), and the National Natural
Science Foundation of China (21172242). We are also thankful for the
support of Shanghai institute of Organic Chemistry, the Chinese Academy
of Sciences.
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