Hydrofluoroarylation of alkynes with fluoroarenes

Article abstract of DOI:10.1039/c0dt00104j

A combination of Ni(cod)₂ and PCyp₃ is found to be an effective catalyst for chemoselective activation of the C-H bond of fluoroarenes over C-F bonds followed by insertion of alkynes to allow direct alkenylation of the electron-defic

Full text of DOI:10.1039/c0dt00104j

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PAPER
www.rsc.org/dalton | Dalton Transactions
Hydrofluoroarylation of alkynes with fluoroarenes†‡
Kyalo Stephen Kanyiva,a Natsuko Kashihara,a Yoshiaki Nakao,*a Tamejiro Hiyama,*a Masato Ohashib,c and
Sensuke Ogoshi*b
Received 10th March 2010, Accepted 28th May 2010
DOI: 10.1039/c0dt00104j
A combination of Ni(cod)2 and PCyp3 is found to be an effective catalyst for chemoselective activation
of the C–H bond of fluoroarenes over C–F bonds followed by insertion of alkynes to allow direct
alkenylation of the electron-deficient arenes. The characteristics of the reactions are: a C–H bond ortho
to a fluorine substituent is selectively activated; the reactivity of fluorobenzenes is roughly proportional
to the number of fluorine atoms. The reaction conditions tolerate a broad range of both alkynes and
fluoroarenes containing both electron-withdrawing and -donating groups, thus allowing efficient
synthesis of a variety of substituted ethenes containing a fluoroaryl motif in high regio- and
stereoselective manners. Mechanistic studies including both labeling experiments and stoichiometric
reactions reveal that oxidative addition of C–H bonds in fluoroarenes to nickel(0) is kinetically highly
facile whereas that of C–F bonds is thermodynamically favoured.
chemoselectively. Although several transition metals have been
Introduction
reported to activate C–H bonds over C–F bonds,8 applications
The presence of fluorine atom(s) in an organic compound signifi-
of these elemental reactions in catalytic functionalisation of fluo-
cantly influences its physical, chemical and biological properties.1
In particular, organic molecules containing fluoroaryl motifs find
increasing applications in pharmaceutical,2 agrochemical3 and
material sciences.4 Accordingly, invention of effective methods
for rapid and concise preparation of fluoroaryl containing com-
pounds, either by direct introduction of fluorine or by use of
fluoroaryl-containing building blocks, is of great significance in
both academia and industry. In most cases, traditional methods
for introduction of a fluorine atom into an aromatic framework
usually require special equipment to perform the experiments
and/or harsh conditions that are incompatible with many func-
tional groups.5 Although fluoroarenes can be functionalised via
deprotonation of their acidic hydrogens with a stoichiometric
amount of organometallic bases followed by reactions with
electrophiles,6 this method results in organometallic wastes in
stoichiometric amounts. Therefore, invention of strikingly efficient
alternative synthetic means is desirable.
Transition metal-catalysed C–H bond transformation has
emerged as an atom-efficient way for functionalisation of organic
molecules.7 Nevertheless, direct functionalisation of C–H bonds
of fluoroarenes remains relatively unexplored compared to that
of electron-rich arenes.7 An intriguing problem to achieve a useful
reaction for direct functionalisation of C–H bonds of fluoroarenes
is the challenge of activating C–H bonds over C–F bonds
roarenes are rare. Recently, Fagnou9 and Daugulis10 demonstrated
pioneering studies for direct coupling reactions at C–H bonds of
fluoroarenes with aryl and alkenyl halides using palladium and
copper catalysts, respectively. On the other hand, a transition
metal-catalysed addition of fluoroarenes across alkynes should
be an attractive method for preparation of multi-functionalised
fluoroarylethenes, in terms of atom and step economy.11
Nickel catalysts have been reported to be effective for activation
of rather acidic C–H bonds of terminal alkynes12 and activated
azoles13 to undergo insertion of unsaturated compounds into
these C–H bonds. On the other hand, fluorine bound to arenes is
known to raise acidity of ortho hydrogens.14 Based on these facts,
we envisaged that activation of C–H bonds of fluoroarenes by
nickel(0) species followed by insertion of alkynes could be feasible.
Herein we describe a nickel-catalysed activation of C–H bonds of
fluoroarenes over C–F bonds followed by insertion of alkynes to
furnish a variety of mono- and disubstituted fluoroarylethenes in
regio- and stereoselective manners.15 The addition reaction can
also be carried out with a nickel catalyst generated in situ by
reduction and deprotonation of a bench-stable Ni(II) complex and
a phosphonium salt, respectively.16 The stoichiometric reaction of
17
pentafluorobenzene and Ni2N2(PCy3)4 reveals that the reaction
is initiated by oxidative addition of C–H bond to nickel(0) to
form a trans-(C6F5)(H)Ni(PCy3)2 complex. Whereas the oxidative
addition step is facile and takes place at room temperature,
insertion of alkynes and/or reductive elimination are slow at
temperatures below 50 ◦C.
aDepartment of Material Chemistry, Graduate School of Engineering,
Kyoto University, Kyoto, 615-8510, Japan. E-mail: yoshiakinakao@
npc05.mbox.media.kyoto-u.ac.jp, thiyama@z06.mbox.media.kyoto-u.ac.jp
bDepartment of Applied Chemistry, Graduate School of Engineering,
Osaka University, Suita, Osaka, 565-0871, Japan. E-mail: ogoshi@
chem.eng.osaka-u.ac.jp
Results and discussion
cCenter for Atomic and Molecular Technologies, Osaka University, Suita,
Osaka, 565-0871, Japan
Nickel-catalysed hydrofluoroarylation of alkynes
† Based on the presentation given at Dalton Discussion No. 12, 13–15th
September 2010, Durham University, UK.
‡ CCDC reference numbers 767668. For crystallographic data in CIF or
other electronic format see DOI: 10.1039/c0dt00104j
We first examined the reaction of pentafluorobenzene (1a,
0.50 mmol) with 4-octyne (2a, 0.75 mmol) in the presence of
a catalytic amount of Ni(cod)2 with various ligands (Table 1).
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©

2
Table 1 Nickel-catalysed addition of pentafluorobenzene (1a) across 4-
octyne (2a)a
possibly to h -coordination of an alkenyl group to nickel(0), which
2
may compete with h -coordination of the fluoroarenes prior to
the C–H bond activation. Whereas the reaction of 2a with 1,2-
and 1,4-difluorobenzene (1j and 1k) gave the desired products
in only low yields, 1,3-difluorobenzene (1i) reacted at the C-2
position to give the corresponding mono-adduct selectively in
moderate yield (cf. entries 12–14). Relatively high reactivity of
1i is attributed to the presence of two fluorine substituents ortho
to the C–H bond to be activated, compared to 1j and 1k. This is
consistent with the observations reported by Fagnou and Dauglus,
whereby the most acidic C–H bonds flanked by two fluorine
substituents are more prone to be activated. Noteworthy is that
mono-fluorobenzene also participated in the addition reaction,
albeit in a low yield (entry 15).19 Both electron-withdrawing
and -donating groups tolerated the reaction conditions to give
multi-functionalised fluoroarylethenes in moderate to high yields
(entries 16–19). The chemoselective activation of the C–H bond
in the presence of an Ar–OMe bond in 1p is in sharp contrast
to the fact that Ni(0)/PCy3 catalyst cleaves the Ar–OMe bond.20
Interestingly, the hydrofluoroarylation reaction occurred at ortho
position of the fluorine substituent regardless of the nature of
other electron-withdrawing groups on the fluoroarene ring. These
data again suggest that the activation of C–H bonds ortho to
fluorine is preferred kinetically and/or thermodynamically.18,19
Fluoropyridines also participated in the addition reaction to afford
the desired adducts in moderate to excellent yields (entries 20–23).
These results represent another feature of the present system to
be noted: a Ni(cod)2/PEt3 combination is reported to activate
C–F bonds of polyfluoropyridines over C–H bonds.21 All the
reaction proceeded with exclusive cis-addition of the fluoroarenes
as confirmed by nOe experiments.
We next investigated the scope of alkynes. The reaction of 1a
with 1,4-bis(trimethylsilyl)-2-butyne (2b) proceeded smoothly to
give pentafluoroaryl-substituted allylsilane 3ab (entry 1 in Table 3)
in 75% yield. Addition across diphenylacetylene (2c) took place
in good yield, although slow addition of the alkyne was essential
to curb its competitive tri- and oligomerisation (entry 2). The
reactions with unsymmetrical internal alkynes, 4,4-dimethyl-2-
pentyne (2d) and 1-trimethylsilylprop-1-yne (2e), proceeded with
excellent regioselectivity to give the corresponding cis-adducts
having a bulkier substituent trans to the pentafluorophenyl
group exclusively (entries 3 and 4). Similar regioselectivity is
also observed with other hydrofunctionalization reactions of
alkynes.12,13b,13d,13e,22 Other sterically biased unsymmetrical internal
alkynes bearing phenyl and silyl groups also participate in this
addition reaction to afford the respective adducts in good yields
with defined regio- and stereoselectivity (entries 5 and 6). Terminal
alkynes, however, failed to give the corresponding adducts due to
rapid competing tri- and oligomerisation of the alkynes.
Entry
Ligand
Solvent
Yield (%)b
1
PCyp3
PCyp3
PCy3
P(i-Pr)3
P(n-Bu)3
P(t-Bu)3
PPh3
PCyPh2
PCyp3
PCyp3
PCyp3
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Hexane
1,4-Dioxane
DMF
>95 (99)c
2d
3
62
94
>95
<1
2
12
6
70
53
69
4
5
6
7
8
9
10
11
a All reactions were carried out using 1a (0.50 mmol), 2a (0.75 mmol),
Ni(cod)2 (3 mol%), and a ligand (3 mol%) in toluene (0.5 mL) at 80 ◦C for
1 h. b Estimated by GC using undecane as an internal standard. c Isolated
yield obtained with a 1.00 mmol scale for 3 h. d PCyp3 (6 mol%) was used.
Among the numerous ligands screened for the reaction, tri(sec-
alkyl)phosphines, especially tricyclopentylphosphine (PCyp3),
gave the desired product (3aa) in excellent yields (entries 1–4). The
cis-stereochemistry of the addition reaction was unambiguously
confirmed by nOe experiments of 3aa. Increase in the amount
of ligand was deleterious to the reaction (entry 2), furnishing
3aa in only 62% yield as estimated by GC. Tri(pri- and tert-
alkyl)phosphines gave only a trace amount of 3aa (entries 5 and
6). Neither triaryl- nor diarylalkylphosphine ligands such as PPh3
or PCyPh2 were effective (entries 7 and 8). The reaction performed
in hexane, 1,4-dioxane and DMF also gave 3aa albeit in moderate
yields (entries 9–11).
With the optimised conditions in hand, we next studied the
scope of fluoroarenes with 2a as an alkyne substrate (Table 2). The
addition of 1,2,3,4-tetrafluorobenzene (1b) across 2a proceeded
smoothly to give the corresponding mono-adduct 3ba in 71%
yield (entry 1). A trace amount of dialkenylated adduct 4ba
was also detected. The reactions of 2 molar equivalents of
tetrafluorobenzenes, 1c and 1d, with 2a also gave the respective
mono-adducts selectively in moderate yields (entries 2 and 4).
On the other hand, when the amount of 2a was increased
to 4 equivalents compared to the fluoroarenes, dialkenylated
products 4ca and 4da were obtained in high and excellent yields,
respectively (entries 3 and 5). Similar results were obtained with 1e
as a fluoroarene substrate (entries 6 and 7). Trifluorobenzenes 1f,
1g and 1h also added across 2a smoothly, although a mixture
of mono- and dialkenylation products resulted (entries 8–11).
Notably, among possible reaction sites, the C–H bond ortho to a
fluorine substituent was primarily activated.9,10 The high selectivity
is attributable to coordination of fluorine to a nickel catalyst to
direct the C–H activation, enhanced acidity of the C–H bonds,14
and/or stabilised Ni–fluoroaryl bond in the oxidative adducts by
ortho fluorine atoms.18 Apparently, non-alkenylated fluoroarenes
are more reactive than mono- and dialkenylated adducts, due
Since both Ni(cod)2 and PCyp3 are oxygen-sensitive, experimen-
tal practicality of the above method may be limited. To improve
its convenience and applicability, a method for generation of
the active nickel(0)/PCyp3 catalyst in situ was developed, which
employs AlMe3 to reduce and deprotonate an air-stable and readily
available nickel(II) complex and a phosphonium salt.16 Thus, the
reaction of 1a and 2a using a catalyst generated in situ by reduction
∑
and deprotonation of bench-stable Ni(acac)2 and HPCyp3 BF4
with AlMe3 following a standard Schlenk technique gave 3aa in
87% isolated yield (eqn (1)).
10484 | Dalton Trans., 2010, 39, 10483–10494
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©

Table 2 Nickel/PCyp3-catalysed addition of fluoroarenes (1) across 4-octyne (2a)
Entry
1
Fluoroarene (1)
x
y
T/◦C
Time/h
12
Yield of 3 (%)a
71 (3ba)
Yield of 4 (%)a
<5 (4ba)
1.0
1.5
80
2b
3
2.0
1.0
1.0
4.0
80
80
5
14
48 (3ca)
<5 (3ca)
7 (4ca)
87 (4ca)
4b
5
2.0
1.0
1.0
4.0
80
80
1
10
53 (3da)
<5 (3da)
7 (4da)
99 (4da)
6b
7b
2.0
1.0
1.0
3.0
80
80
1
10
61 (3ea)
<5 (3ea)
9 (4ea)
92 (4ea)
8
9
2.0
1.0
1.0
1.5
100
80
3
2
35 (3fa)
75 (3ga)
2 (4fa)
16 (4ga)c
10d
11
1.0
2.0
4.0
1.0
80
80
30
1
15 (3ha)
15 (3ha)
35 (4ha)
35 (4ha)
12
13
1.0
1.0
1.5
1.5
100
100
10
10
54 (3ia)
9 (3ja)
7 (4ia)
<5 (4ja)
14
1.0
1.5
100
11
33 (3ka)
<5 (4ka)
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©

Table 2 (Contd.)
Entry
15
Fluoroarene (1)
x
y
T/◦C
Time/h
20
Yield of 3 (%)a
8 (3la)
Yield of 4 (%)a
<5 (4la)
1.0
1.5
100
16
1.0
1.5
80
2
71 (3ma)
<5 (4ma)
17
18
1.0
2.0
3.0
1.0
100
100
3
3
47 (3na)
41 (3oa)
5 (4na)
3 (4oa)
19
1.0
1.0
1.5
1.0
80
80
2
87 (3pa)
85 (3qa)
—
20b
18
1.0
21
22
1.0
2.0
3.0
1.0
80
80
9
3
<5 (3ra)
40 (3ra)
91
6 (4ra)
23b
2.0
1.0
80
2
99 (3sa)
<5 (4sa)
a Isolated yield obtained with a 1.00 mmol scale. b Run with 3.0 mol% of Ni(cod)2 and PCyp3. c Obtained as a mixture of isomers. d 2,4,6-
trialkenyltrifluorobenzene was also obtained in 21% yield.
C6D6, evolution of a gas (nitrogen) and oxidative addition of
the C–H and its para C–F bonds in 1a to nickel(0) took place
to give a mixture of trans-(C6F5)(H)Ni(PCy3)2 (7) and trans-
(1)
(C6F4H)(F)Ni(PCy3)2 (8) complexes (Scheme 1). The C–H and C–
2
F bond activation possibly takes place via a h -complex (6), which
would be formed by coordination of 1a to the nickel(0) complex.23
Mechanism of addition reaction of fluoroarenes to alkynes
The ratio of the two complexes after 1 h was estimated to be ~4 : 1
as determined by 31P NMR. These observations are in agreement
with those reported by Johnson and coworkers on the reaction
To gain a mechanistic insight into the addition reaction, we
1
examined H, 31P and 19F NMR studies of the reaction. Upon
2
of 1,2,4,5-tetrafluorobenzene with (Et3P)2Ni(h -C10H10)23c but in
mixing stoichiometric amounts of 1a and Ni2N2(PCy3)4 (5) in
10486 | Dalton Trans., 2010, 39, 10483–10494
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©

Table 3 Nickel/PCyp3-catalysed hydroarylation of alkynes with 1aa
Entry
1
Alkyne
mmol
3.0
T/◦C
Time/h
6
Yield of 3 (%)b
75 (3ab)
2b
80
2b
3c
4
5
6d
2c
2d
2e
2f
3.0
1.5
1.5
1.5
1.0
80
80
100
100
100
3.5
3
13
15
24
68 (3ac)
89 (3ad)
47 (3ae)
63 (3af)
63 (3ag)
2g
a All reactions were carried out using 1 (1.00 mmol), 2a (1.50–3.00 mmol), Ni(cod)2 (0.10 mmol), and PCyp3 (0.10 mmol) in toluene (1.0 mL). b Slow
addition of 2c over 2.5 h. c Run with 3.0 mol% of Ni(cod)2 and PCyp3. d Ratio of 1a : 2g = 2.0 : 1.0.
Scheme
1
Stoichiometric reactions of 1a, Ni2N2(PCy3)4 (5) and
Ni(cod)2/PCy3.
sharp contrast with selective C–F activation of fluoroarenes over
C–H activation with a closely related nickel dimer complex ligated
by an N-heterocyclic carbene.23b The 1H NMR spectrum showed
a multiplet of triplets at d -16.3 with a 2JP–H value of 68.3 Hz, as
Scheme 2 Stoichiometric reaction of 7 with 2a.
anticipated for a nickel hydride complex.23 The 1H decoupled 31
P
NMR spectrum featured a resonance for the hydride complex at
formation of p-cyclobutenylnickel complex 9, which exhibits 31P
NMR signal at 27.8 ppm was observed. Analytically pure yellow
powder of complex 9 was obtained in 10% yield by column
chromatography on silica gel. X-Ray quality microcrystals were
then obtained by dissolving 9 into 1,4-dioxane at 60 ◦C and
leaving the clear orange solution overnight at room temperature.
The X-ray crystal structure of 9 is shown in Fig. 1. Formation
of complex 9 possibly takes place via pentafluroroaryl–Ni–alkenyl
complex 10 and pentafluroroaryl–Ni–dienyl complex 11, which
would be formed by insertion of one and two molecules of 4-
octyne into the Ni–H bond of 7, respectively,24 followed by thermal
electrocyclisation of the diene moiety in 11 in a conrotatory
manner. Similar nickel complexes have been previously reported.25
Nevertheless, a reaction done using a catalytic amount of complex
9 did not proceed at all, indicating that 9 is not involved in the
catalytic cycle.
d 40.2 as a singlet, while the nickel fluoride complex was observed
2
at d 19.4 as a doublet with a JP–F value of 40.8 Hz. The 19F
NMR of the nickel fluoride featured a triplet at d -404.9 with a
2JP–F value of 39.8 Hz. Although a similar stoichiometric reaction
carried out using 1a, Ni(cod)2 and 1 or 2 equivalents of PCy3 in
C6D6 gave similar species by 31P NMR, the reaction was sluggish
possibly due to slow ligand exchange between 1,5-cyclooctadiene
(cod) and PCy3. All attempts to isolate and crystallise the nickel
hydride complex suitable for X-ray analyses were fruitless.
When 2a (1.5 equivalents) was added to a mixture of 7 and
8 (~4 : 1) in C6D6, gradual conversion of the nickel hydride 7,
and simultaneous formation of 3aa was observed upon heating
the mixture at 80 ◦C, with 8 remaining unchanged (Scheme 2).
The reaction was complete in 3 h to give 3aa in 65% yield
as estimated by 19F NMR. Upon the addition of 2a, however,
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The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 10483–10494 | 10487
©

Fig. 2 Estimation of KIE in hydrofluoroarylation of alkynes.
2
to nickel(0) complex to form h -arene complex 6 (Scheme 3).
The intermediacy of the h -complex species is fully supported by
Fig. 1 ORTEP diagram of 9 (all hydrogens are omitted for clarity).
2
literature precedents.23,26,27 This is followed by reversible oxidative
addition of the C–H bond to nickel(0) to give trans-nickel
hydride complex 7. Ligand exchange between the coordinating
phosphine with an alkyne followed by migratory insertion of the
coordinating alkyne into the Ni–H bond gives fluoroaryl–Ni(II)–
alkenyl intermediate 14. When unsymmetrical internal alkynes
are used, the coordination followed by the hydronickelation takes
place in the direction which avoids steric repulsion between bulkier
R2 and the fluoroaryl group in intermediates 13 and 14.
Noteworthy, upon heating the crude mixture of 7 and 8 at
100 ◦C, nickel fluoride 8 became a major product (7 : 8 = <5 : 95
after 2 h). Reversibility of the oxidative addition of C–H bond of 1a
to nickel(0) was further confirmed by the fact that addition of 1p to
the mixture of 7 and 8 (~4 : 1) in C6D6 followed by heating at 50 ◦C
for 24 h gave a mixture of nickel hydrides derived from 1a and 1p,
and an increased amount of 8 (eqn (2)). These observations clearly
show that the oxidative addition of C–F bonds is irreversible and
thermodynamically favoured over that of C–H bonds, which is
likely to be favoured kinetically.23c,d,26
(2)
Similar nickel species were also observed in the catalytic reaction
of 1a with 2a (1.5 equivalents) in the presence of 5 (10 mol%)
or Ni(cod)2 (20 mol%) and PCy3 (40 mol%) in C6D6 at 50 ◦C,
although the reactions were sluggish. The ratio of 7 : 9 after 30 min
was 1 : 10; the p-cyclobutenyl nickel complex 9 being the major
phosphine species, suggesting that only a small amount of nickel
is actually catalytically active. The same reaction but with 20 mol%
of PCy3 was faster to give 3aa in 63% yield after 12 h as estimated
by GC. These results indicate that equimolar amounts of nickel
and PCyp3 are optimum and that the phosphine ligand in excess
retards the reaction. To understand the mechanism further, we
measured initial rates of the reactions of 1p or 1p-d1 with 2a to
estimate a kinetic isotope effect (KIE) value to be 1.0 (eqn (3)
and Fig. 2), indicating that neither C–H bond activation nor the
hydronickelation step is rate-determining.
Scheme 3 Plausible mechanism for hydrofluoroarylation across alkynes.
Subsequent reductive elimination of 14 produces adduct 3 and
regenerates the nickel(0) species. On the other hand, insertion
of another alkyne molecule into either of the Ni–C bonds of
14,24 followed by thermal electrocyclisation forms complex 9
(Scheme 2). Since the catalytic reaction is run using an equimolar
amount of phosphine compared to nickel, the alkyne possibly acts
as a ligand to stabilise some intermediates in the catalytic cycle.
Phosphine ligands in excess possibly retard the ligand exchange
step, a plausible rate-determining step, thereby resulting in a lower
rate and yield of the reaction (entry 1 vs. 2 of Table 1).
(3)
Based on these results, the catalytic cycle of the hydrofluoroary-
2
lation of alkynes should be initiated by h -coordination of 1a
10488 | Dalton Trans., 2010, 39, 10483–10494
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©

Comparison of PCy3 and P(n-Bu)3 as a ligand
Conclusion
In conclusion, we have demonstrated addition reactions of flu-
oroarenes across alkynes under nickel catalysis. This hydroflu-
oroarylation reaction proceeds with high chemo-, regio-, and
stereoselectivities to give rise to a wide variety of fluoroaryl ethenes
in good to high yields. The reaction conditions tolerate a wide
scope of fluoroarenes and alkynes. The versatility and applicability
of the nickel catalysis may be raised by the protocol that generates
an active nickel(0) catalyst in situ from a bench-stable nickel(II)
precursor, a phosphonium salt and AlMe3. A catalytic cycle involv-
ing a nickel hydride intermediate derived from oxidative addition
of the C–H bond in fluoroarenes and a rate-determining ligand
exchange step has been established by a series of NMR studies.
As reported by Johnson and coworkers, activation of the C–
H bond in fluoroarenes with a nickel(0)/tri(n-alkyl)phosphine
2
complex, (Et3P)2Ni(h -C10H10), readily takes place.23c In contrast,
Table 1 shows that only tri(sec-alkyl)phosphine ligands are highly
effective in the present addition reaction. To gain rationale for this
observation, we also studied a stoichiometric reaction of 1a, 2a
with Ni(cod)[P(n-Bu)3]2 (15),28 which was prepared in situ by the
reaction of Ni(cod)2 with 2.0 equivalents of P(n-Bu)3 followed by
removal of liberated cod in vacuo. No hydroarylation reaction
took place with the nickel complex, even at elevated reaction
◦
temperature of 80 C for 12 h (eqn (4)). In addition, monitoring
the reaction by 1H and 31P NMR showed no formation of a nickel
hydride complex. On the other hand, the stoichiometric reaction
of Ni(4-octyne)[P(n-Bu)3]2 (16) with 1a at 80 ◦C proceeded to
give 3aa in low yield, accompanied by tri- and oligomerisation
of the alkyne (eqn (5)). These two experiments suggest that
nickel complexes 15 and 16 coordinated by phosphorus-donor
ligands with a small cone angle29 are reluctant to undergo ligand
exchange between the coordinating cod or alkynes with 1a even at
elevated temperatures. In contrast, such ligand exchange would be
feasible with phosphorous ligands having a large cone angle due
presumably to steric hindrance. In addition, the large cone angle
may also accelerate the reductive elimination step.
Experimental
All manipulations of oxygen- and moisture-sensitive materials
were conducted with standard Schlenk technique or in a glove
box under an argon or nitrogen atmosphere. Flash column
chromatography was performed using Kanto Chemical silica
gel (spherical, 40–50 mm). Analytical thin layer chromatography
(TLC) was performed on Merck Kieselgel 60 F254 (0.25 mm)
plates. Visualisation was accomplished with UV light (254 nm)
and/or an aqueous alkaline KMnO4 solution followed by heating.
Proton and carbon nuclear magnetic resonance spectra (1H NMR
and 13C NMR) were recorded on a Varian Mercury 400 (1H
NMR, 400 MHz; 13C NMR, 101 MHz) or JEOL ECA-600P (1H
NMR, 600 MHz; 13C NMR, 150 MHz) spectrometer with solvent
resonance as the internal standard (1H NMR, CHCl3 at 7.26 ppm
or C6D5H at 7.15 ppm; 13C NMR, CDCl3 at 77.0 ppm or C6D6
at 128.6 ppm) as an external standard. Fluorine and phosphine
nuclear magnetic resonance spectra (19F NMR and 31P NMR) were
recorded on a Varian Gemini 300 (19F NMR, 282 MHz; 31P NMR,
121 MHz) spectrometer with CFCl3 (0 ppm) as internal standard
and phosphoric acid (0 ppm) as an external standard, respectively.
Melting points (mp) were determined using a YANAKO MP-
500D. Elemental analyses were performed by Elemental Analysis
Center of Kyoto University or Instrumental Analysis Center of
Osaka University. High-resolution mass spectra (HRMS) were ob-
tained with a JEOL JMS-700 (EI) or JEOL JMS-HX110A (FAB+)
spectrometer. Preparative recycling gel permeation chromatogra-
phy (GPC) and preparative recycling silica gel chromatography
were performed with a JAI LC-908 chromatograph equipped with
JAIGEL-1H and -2H (chloroform as an eluent) and JAIGEL-
SIL or Nacalai tesque 5SL-II (hexane–ethyl acetate as an eluent).
GC analyses were performed on a Shimadzu GC 2014 equipped
with an ENV-1 column (Kanto Chemical, 30 m ¥ 0.25 mm,
pressure = 31.7 kPa, detector = FID, 290 ◦C) with a helium
gas as a carrier. Unless otherwise noted, commercially available
reagents were used without purification. Toluene was distilled from
sodium/benzophenone ketyl or purchased from Kanto Chemical
and degassed by purging vigorously with argon for 20 min and
further purified by passing through activated alumina under
positive argon pressure as described by Grubbs et al.30
(4)
(5)
Transformations of 3da
Some synthetic transformations of the adducts thus obtained
are demonstrated by sequential alkenylation of 3da with 2b
under the nickel catalysis to afford unsymmetrically dialkenylated
tetrafluorobenzene 17 in 78% yield (Scheme 4). Also, direct C–
H arylation of 3da with an equimolar amount of 4-iodotoluene
following a palladium-catalysed protocol reported by Fagnou and
coworkers gave biarylethene 18 in 66% yield.9a
Chemicals
1,4-Bis(trimethylsilyl)-2-butyne (2b)31 and Ni2N2(PCy3)4 were
17
Scheme 4 Alkenylation and arylation reactions of 3da.
prepared according to the respective literature procedure.
This journal is
The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 10483–10494 | 10489
©

Nickel-catalysed hydrofluoroarylation of alkynes
(m, 1H), 5.49 (t, J = 7.3 Hz, 1H), 2.38 (t, J = 7.7 Hz, 2H), 2.23
(q, J = 7.3 Hz, 2H), 1.49 (sext, J = 7.3 Hz, 2H), 1.31 (sext, J =
7.5 Hz, 2H), 0.97 (t, J = 7.4 Hz, 3H), 0.89 (t, J = 7.3 Hz, 3H);
13C NMR (101 MHz, CDCl3) d 155.6 (dm, JF = 245.4 Hz), 148.1
(dm, JF = 262.5 Hz), 147.1 (dm, JF = 245.8 Hz), 134.8, 128.0,
122.8 (dd, JF = 22.9, 17.0 Hz), 114.4 (dd, JF = 18.1, 9.5 Hz), 110.2
(ddd, JF = 26.2, 6.9, 3.8 Hz), 32.7, 30.2, 22.8, 21.5, 13.92, 13.88;
General procedure. In a glove box, a solution of Ni(cod)2 (8.4 mg,
30 mmol) and PCyp3 (7.2 mg, 30 mmol) in toluene (1.0 mL) was
added to a solution of pentafluorobenzene (168 mg, 1.00 mmol)
and 4-octyne (165 mg, 1.50 mmol) placed in a 3 mL vial. Undecane
(an internal standard, 78 mg, 0.5 mmol) was added. The vial
was closed with a screw cap, taken out from the glove box, and
heated at the temperature for the time specified in Tables 1, 2
and 3. The resulting mixture was filtered through a silica gel
pad and concentrated in vacuo. The residue was purified by
flash chromatography on silica gel to give the corresponding
products in yields listed in Tables 1, 2 and 3. In some cases,
a mixture of mono- and dialkenylated products and impurities
(mainly tri- and oligomers of alkynes) were further separated by
preparative recycling GPC or silica gel chromatography. Structural
characterisation of 3aa, 3ba, 3ca, 4ca, 3da, 4da, 3fa, 3ha, 4ha, 3ia,
4ia, 3ja, 3la, 3ma, 3pa, 3qa, 3sa, 3ab, 3ac, 3ad, 3ae, and 3af were
performed previously.15
19F NMR (282 MHz, CDCl3) d -119.0 (s, 1F), -137.2 (dd, JF
=
22.6, 11.3 Hz, 1F), -143.3 to -143.6 (m, 1F); MS (EI, 70 eV) m/z
(%) 243 (M+ + 1, 10), 242 (M+, 64), 200 (32), 199 (100), 185 (35),
183 (11), 173 (10), 172 (81), 171 (90), 169 (25), 164 (18), 159 (28),
158 (19), 157 (18), 156 (18), 151 (42), 146 (15), 145 (94), 137 (15),
55 (35).
(E)-1,3,5-Trifluoro-2-(oct-4-en-4-yl)benzene (3ha). A colour-
less oil, Rf 0.55 (hexane). IR (neat) 2922, 2853, 1595, 1462, 1452,
1420, 1377, 1144, 1036, 833; 1H NMR (400 MHz, CDCl3) d 6.67–
6.57 (m, 2H), 5.44 (t, J = 7.3 Hz, 1H), 2.34 (t, J = 7.6 Hz, 2H),
2.20 (q, J = 7.3 Hz, 2H), 1.47 (sext, J = 7.3 Hz, 2H), 1.29 (sext,
J = 7.5 Hz, 2H), 0.96 (t, J = 7.3 Hz, 3H), 0.89 (t, J = 7.3 Hz, 3H);
13C NMR (101 MHz, CDCl3) d 160.8 (dt, JF = 241.1, 15.5 Hz),
160.3 (ddd, JF = 241.1, 14.5, 10.8 Hz), 134.4, 127.7, 117.2 (t, JF =
17.1 Hz), 99.8 (dd, JF = 32.2, 25.1 Hz), 32.9, 30.2, 22.8, 21.5, 13.92,
13.87; 19F NMR (282 MHz, CDCl3) d -110.7 (t, JF = 6.1 Hz, 2F),
-111.6 to -111.9 (m, 1F); MS (EI, 70 eV) m/z (%) 243 (M+, 20),
242 (M+, 76), 213 (12), 200 (60), 199 (100), 197 (12), 186 (10), 185
(53), 183 (16), 182 (13), 173 (17), 172 (79), 171 (87), 169 (48), 165
(11), 164 (18), 159 (51), 158 (27), 157 (55), 156 (36), 151 (49), 146
(38), 145 (90), 137 (32), 125 (10), 67 (13), 55 (35); HRMS (EI)
Calcd for C14H17F3: M+, 242.1282. Found: 242.1283.
(E)-2,3,5,6,2¢,3¢,5¢,6¢-Octafluoro-4-(oct-4-en-4-yl)biphenyl
(3ae). A yellow oil, Rf 0.30 (hexane). Anal. Calcd for C20H16F8:
C, 58.83; H, 3.95. Found: C, 59.05; H, 4.10. IR (neat) 2964, 2945,
2889, 2857, 2847, 1504, 1469, 1462, 1456, 1377, 1268, 1177, 988,
935, 849, 708; 1H NMR (400 MHz, CDCl3) d 7.28–7.17 (m, 1H),
5.61 (t, J = 7.3 Hz, 1H), 2.42 (t, J = 7.7 Hz, 2H), 2.25 (q, J =
7.3 Hz, 2H), 1.50 (sext, J = 7.3 Hz, 2H), 1.36 (sext, J = 7.5 Hz,
2H), 0.98 (t, J = 7.3 Hz, 3H), 0.93 (t, J = 7.3 Hz, 3H); 13C NMR
(101 MHz, CDCl3) d 146.1 (dm, JF = 256.7 Hz), 145.8 (dm, JF =
251.8 Hz), 144.1 (dm, JF = 238.8 Hz), 143.8 (dm, JF = 251.8 Hz),
136.4, 127.0, 125.4 (t, JF = 18.5 Hz), 108.2 (t, JF = 20.2 Hz), 107.5
(t, JF = 22.3 Hz), 104.8 (t, JF = 20.2 Hz), 32.6, 30.3, 22.6, 21.7,
13.89, 13.85; 19F NMR (282 MHz, CDCl3) d -138.4 to -138.6 (m,
2F), -138.7 to -138.9 (m, 2F), -139.9 to -140.3 (m, 2F), -141.9
(dd, J = 22.9, 10.4 Hz, 2F); MS (EI, 70 eV) m/z (%) 409 (M++1,
20), 408 (M+, 76), 366 (64), 365 (100), 351 (39), 339 (35), 338 (95),
337 (85), 330 (20), 325 (29), 324 (36), 323 (16), 322 (24), 318 (16),
312 (29), 311 (89), 299 (12), 297 (11), 291 (20), 273 (22), 268 (13),
253 (14), 55 (20).
(E)-1,3,5-Trifluoro-2,4-bis(oct-4-en-4-yl)benzene
(4ha). A
colourless oil, Rf 0.55 (hexane). Anal. Calcd for C22H31F3: C,
74.97; H, 8.86. Found: C, 75.12; H, 9.01. IR (neat) 2959, 2932,
2872, 1628, 1593, 1483, 1465, 1456, 1418, 1379, 1339, 1262,
1
1144, 1117, 1091, 1036, 974, 899, 833, 739, 577, 549; H NMR
(400 MHz, CDCl3) d 6.59 (td, J = 9.3, 2.0 Hz, 1H), 5.44 (t, J =
7.3 Hz, 2H), 2.33 (t, J = 7.7 Hz, 4H), 2.20 (q, J = 7.3 Hz, 4H),
1.47 (sext, J = 7.3 Hz, 4H), 1.30 (sext, J = 7.4 Hz, 4H), 0.96 (t,
J = 7.4 Hz, 6H), 0.89 (t, J = 7.3 Hz, 6H); 13C NMR (101 MHz,
CDCl3) d 158.4 (ddd, JF = 226.3, 15.3, 10.7 Hz), 157.7 (dt, JF =
241.4, 10.1 Hz), 134.1, 128.2, 116.7 (dd, JF = 25.5, 23.9 Hz), 99.3
(td, JF = 27.8, 4.2 Hz), 33.0, 30.2, 22.8, 21.5, 14.0, 13.9; 19F NMR
(282 MHz, CDCl3) d -113.5 (s, 1F), -114.6 (s, 2F); MS (EI, 70
eV) m/z (%) 353 (M+ + 1, 14), 352 (M+, 57), 310 (48), 309 (100),
281 (29), 267 (24), 255 (36), 213 (10).
(E,E)-2,3,5,6,2¢,3¢,5¢,6¢-Octafluoro-4,4¢-bis(oct-4-en-4-yl)-
biphenyl (4ea). A yellow solid, mp 56.5–57.4 ◦C, Rf 0.30 (hexane).
Anal. Calcd for C28H30F8: C, 64.86; H, 5.83. Found: C, 65.12; H,
6.01. IR (KBr) 2961, 2932, 2872, 1651, 1479, 1462, 1401, 1379,
1367, 1339, 1287, 1261, 1165, 1094, 1071, 990, 968, 901, 818, 721,
656, 567; 1H NMR (400 MHz, CDCl3) d 5.62 (t, JF = 7.3 Hz, 2H),
2.43 (t, J = 7.6 Hz, 4H), 2.26 (q, JF = 7.3 Hz, 4H), 1.51 (sext, JF =
7.3 Hz, 4H), 1.38 (sext, JF = 7.5 Hz, 4H), 0.99 (t, JF = 7.4 Hz,
6H), 0.94 (t, JF = 7.3 Hz, 6H); 13C NMR (101 MHz, CDCl3) d
144.0 (dm, JF = 246.4 Hz), 143.8 (dm, JF = 251.9 Hz), 136.3,
127.1, 125.2 (t, JF = 18.9 Hz), 105.2 (t, JF = 16.2 Hz), 32.6, 30.3,
22.7, 21.7, 13.84, 13.79; 19F NMR (282 MHz, CDCl3) d -139.9 to
-140.3 (m, 4F), -142.0 to -142.4 (m, 4F); MS (EI, 70 eV) m/z (%)
519 (M+ + 1, 14), 518 (M+, 37), 476 (36), 475 (100), 447 (18), 433
(18), 281 (13), 207 (20), 73 (11).
(E)-1,3,5-Trifluoro-2,4,6-tris(oct-4-en-4-yl)benzene (4¢ha).
A
yellow oil, Rf 0.55 (hexane). Anal. Calcd for C30H45F3: C, 77.88;
H, 9.80. Found: C, 78.03; H, 9.87. IR (neat) 2959, 2932, 2872,
1601, 1462, 1454, 1429, 1379, 1360, 1337, 1260, 1244, 1186, 1117,
1086, 1053, 1042, 1018, 993, 899, 859, 808, 739, 692, 598; 1H NMR
(400 MHz, CDCl3) d 5.45 (t, J = 7.3 Hz, 3H), 2.33 (t, J = 7.6 Hz,
6H), 2.19 (q, J = 7.3 Hz, 6H), 1.47 (sext, J = 7.3 Hz, 6H), 1.30
(sext, J = 7.5 Hz, 6H), 0.96 (t, J = 7.4 Hz, 9H), 0.89 (t, J =
7.3 Hz, 9H); 13C NMR (101 MHz, CDCl3) d 155.7 (dt, JF = 242.6,
10.8 Hz), 133.7, 128.6, 116.1 (dd, JF = 27.7, 23.2 Hz), 33.0, 30.3,
22.8, 21.6, 13.99, 13.95; 19F NMR (282 MHz, CDCl3) d -117.2 (s,
3F); MS (EI, 70 eV) m/z (%) 463 (M+, 26), 462 (76), 433 (14), 421
(E)-1,2,4-Trifluoro-3-(oct-4-en-4-yl)benzene (3ga). A yellow
oil, Rf 0.40 (hexane). Anal. Calcd for C14H17F3: C, 69.40; H, 7.07.
Found: C, 69.69; H, 7.22. IR (neat) 2964, 2872, 1636, 1541, 1485,
1445, 1380, 1365, 1356, 1279, 1339, 1261, 1196, 1032, 972, 899,
860; 1H NMR (400 MHz, CDCl3) d 7.04–6.92 (m, 1H), 6.82–6.73
10490 | Dalton Trans., 2010, 39, 10483–10494
This journal is
The Royal Society of Chemistry 2010
©

(23), 420 (15), 419 (100), 405 (14), 392 (19), 391 (44), 379 (17), 377
(32), 366 (18), 365 (53), 349 (13), 335 (12), 69 (32), 55 (27).
(E)-4-Fluoro-3-(oct-4-en-4-yl)acetophenone (3oa). A yellow
oil, Rf 0.10 (hexane–ethyl acetate = 50 : 1). IR (neat) 2961, 2932,
2872, 1688, 1605, 1580, 1489, 1458, 1431, 1412, 1379, 1358, 1304,
1288, 1242, 1202, 1119, 1099, 957, 897, 829, 731, 652, 600, 567; 1H
NMR (400 MHz, CDCl3) d 7.85–7.78 (m, 2H), 7.10–7.02 (m, 1H),
5.54 (t, J = 7.3 Hz, 1H), 2.60 (s, 3H), 2.45 (t, J = 7.6 Hz, 2H),
2.20 (q, J = 7.4 Hz, 2H), 1.48 (sext, J = 7.3 Hz, 2H), 1.29 (sext,
J = 7.5 Hz, 2H), 0.98 (t, J = 7.3 Hz, 3H), 0.87 (t, J = 7.4 Hz, 3H);
13C NMR (101 MHz, CDCl3) d 196.5, 162.8 (d, JF = 254.9 Hz),
135.1, 133.1 (d, JF = 3.1 Hz), 132.9, 132.2 (d, JF = 16.2 Hz), 131.1
(d, JF = 6.2 Hz), 128.6 (d, JF = 9.3 Hz), 115.6 (d, JF = 26.4 Hz),
32.4 (d, JF = 2.3 Hz), 30.4, 26.6, 22.9, 21.6, 13.98, 13.94; 19F NMR
(282 MHz, CDCl3) d -108.3 (s, 1F). MS (EI, 70 eV) m/z (%) 249
(M+ + 1, 52), 248 (M+, 100), 233 (32), 219 (18), 206 (41), 205 (96),
191 (51), 179 (12), 178 (73), 177 (39), 175 (21), 165 (20), 164 (16),
163 (80), 161 (23), 159 (12), 151 (63), 149 (23), 147 (37), 146 (46),
136 (14), 135 (23), 134 (13), 133 (52), 127 (10), 115 (12), 109 (17),
108 (11), 55 (12); HRMS (EI) Calcd for C16H21FO: M+, 248.1576.
Found: 248.1581.
(E)-1,4-Difluoro-2-(oct-4-en-4-yl)benzene (3ka). A yellow oil,
Rf 0.50 (hexane). Anal. Calcd for C14H18F2: C, 74.97; H, 8.09.
Found: C, 75.03; H, 8.18. IR (neat) 2961, 2932, 2872, 1618, 1587,
1493, 1487, 1468, 1464, 1456, 1418, 1379, 1275, 1244, 1202, 1177,
1086, 874, 812, 756; 1H NMR (400 MHz, CDCl3) d 6.98–6.82 (m,
3H), 5.53 (t, J = 7.2 Hz, 1H), 2.42 (t, J = 7.6 Hz, 2H), 2.18 (q, J =
7.3 Hz, 2H), 1.47 (sext, J = 7.4 Hz, 2H), 1.31 (sext, J = 7.4 Hz,
2H), 0.97 (t, J = 7.3 Hz, 3H), 0.87 (t, J = 7.3 Hz, 3H); 13C NMR
(101 MHz, CDCl3) d 158.3 (dd, JF = 250.3, 2.9 Hz), 155.8 (dd,
JF = 250.3, 2.9 Hz), 135.2, 133.2 (dd, JF = 17.5, 7.7 Hz), 132.7,
116.6 (dd, JF = 23.8, 5.0 Hz), 116.2 (dd, JF = 27.0, 8.5 Hz), 113.9
(dd, JF = 23.9, 8.4 Hz), 32.3 (d, JF = 3.1 Hz), 30.4, 22.9, 21.6,
13.99, 13.96; 19F NMR (282 MHz, CDCl3) d -120.5 to -120.9 (m,
1F), -122.3 to -122.6 (m, 1F); MS (EI, 70 eV) m/z (%) 224 (M+,
55), 182 (21), 181 (100), 167 (20), 165 (15), 164 (15), 154 (62), 153
(93), 151 (30), 141 (16), 133 (25), 127 (89), 119 (11), 55 (22).
(E,E)-4-Fluoro-3,5-di(oct-4-en-4-yl)acetophenone
(4oa). A
(E)-3-Fluoro-4-(oct-4-en-4-yl)acetophenone (3na).
A yellow
yellow oil, Rf 0.10 (hexane). IR (neat) 2959, 2932, 2872, 1688,
1584, 1456, 1416, 1377, 1360, 1240, 1202, 1137, 1082, 889, 760,
741, 650, 577; 1H NMR (400 MHz, CDCl3) d 7.65 (d, J = 6.8 Hz,
2H), 5.52 (t, J = 7.2 Hz, 2H), 2.59 (s, 3H), 2.44 (t, J = 7.6 Hz,
4H), 2.19 (q, J = 7.3 Hz, 4H), 1.48 (sext, J = 7.3 Hz, 4H), 1.30
(sext, J = 7.5 Hz, 4H), 0.98 (t, J = 7.3 Hz, 6H), 0.87 (t, J =
7.4 Hz, 6H); 13C NMR (101 MHz, CDCl3) d 197.0, 160.0 (d,
JF = 254.9 Hz), 135.6, 132.5, 132.2 (d, JF = 17.8 Hz), 129.3 (d,
JF = 6.2 Hz), 32.6 (d, JF = 2.3 Hz), 30.4, 26.7, 22.9, 21.6, 14.1,
14.0; 19F NMR (282 MHz, CDCl3) d -110.9 (t, JF = 2.4 Hz, 1F);
MS (EI, 70 eV) m/z (%) 359 (M+ + 1, 64), 358 (M+, 100), 343
(16), 329 (20), 316 (53), 315 (95), 288 (12), 287 (21), 285 (12), 273
(42), 271 (42), 259 (11), 245 (20), 243 (11), 231 (10), 229 (41), 217
(17), 216 (17), 215 (69), 203 (19), 201 (12), 189 (24), 187 (12), 175
(30), 173 (12), 147 (11), 69 (20), 55 (13); HRMS (EI) Calcd for
C24H35FO: M+, 358.2672. Found: 358.2656.
oil, Rf 0.10 (hexane–ethyl acetate = 50 : 1). IR (neat) 3364, 2961,
2934, 2856, 1694, 1682, 1614, 1562, 1495, 1465, 1454, 1416, 1360,
1
1279, 1242, 1188, 1123, 1099, 1076, 963, 891, 831, 646, 560; H
NMR (400 MHz, CDCl3) d 7.66 (dd, J = 7.9, 1.7 Hz, 1H), 7.58
(dd, J = 11.1, 1.6 Hz, 1H), 7.28 (t, J = 7.7 Hz, 1H), 5.58 (t,
J = 7.3 Hz, 1H), 2.58 (s, 3H), 2.46 (t, J = 7.6 Hz, 2H), 2.20 (q,
J = 7.3 Hz, 2H), 1.48 (sext, J = 7.3 Hz, 2H), 1.29 (sext, J =
7.5 Hz, 2H), 0.97 (t, J = 7.3 Hz, 3H), 0.86 (t, J = 7.3 Hz, 3H); 13
C
NMR (101 MHz, CDCl3) d 196.2 (d, JF = 2.3 Hz), 159.6 (d, JF =
248.7 Hz), 136.9 (d, JF = 3.1 Hz), 136.8 (d, JF = 11.5 Hz), 135.3
(d, JF = 1.5 Hz), 133.3, 130.5 (d, JF = 3.8 Hz), 123.7 (d, JF
=
3.1 Hz), 115.1 (d, JF = 24.6 Hz), 32.1 (d, J = 3.1 Hz), 30.3, 26.6,
22.8, 21.6, 13.9, 13.8; 19F NMR (282 MHz, CDCl3) d -114.8. MS
(EI, 70 eV) m/z (%) 249 (M+ + 1, 52), 248 (M+, 100), 233 (25), 219
(34), 206 (42), 205 (92), 191 (49), 179 (14), 178 (79), 177 (37), 165
(21), 163 (80), 161 (22), 151 (46), 147 (47), 146 (57), 134 (17), 133
(70), 123 (37), 115 (18), 108 (16), 107 (11), 55 (15); HRMS (EI)
Calcd for C16H21FO: M+, 248.1576. Found: 248.1572.
(E)-2,4,6-Trifluoro-3-(oct-4-en-4-yl)pyridine (3ra). A yellow
oil, Rf 0.20 (hexane). Anal. Calcd for C13H16F3N: C, 64.18; H, 6.63.
Found: C, 64.35; H, 6.89. IR (neat) 2964, 2941, 2874, 1593, 1462,
1406, 1377, 1144, 1049, 1013, 833; 1H NMR (400 MHz, CDCl3) d
6.56 (ddd, J = 7.7, 1.2, 0.6 Hz, 1H), 5.51 (t, J = 7.4 Hz, 1H), 2.34
(t, J = 7.6 Hz, 2H), 2.20 (q, J = 7.5 Hz, 2H), 1.47 (sext, J = 7.4 Hz,
2H), 1.29 (sext, J = 7.4 Hz, 2H), 0.96 (t, J = 7.3 Hz, 3H), 0.89
(t, J = 7.3 Hz, 3H); 13C NMR (101 MHz, CDCl3) d 170.1 (ddd,
JF = 261.1, 12.3, 9.2 Hz), 159.8 (dt, JF = 242.6, 17.8 Hz), 159.6
(ddd, JF = 243.3, 17.7, 12.3 Hz), 135.9, 126.1 (d, JF = 3.8 Hz),
112.8–112.1 (m), 94.9 (ddd, JF = 39.3, 26.2, 6.2 Hz), 32.4, 30.2,
22.6, 21.5, 13.8 (2C); 19F NMR (282 MHz, CDCl3) d -67.8 (dd,
JF = 21.4, 13.0 Hz, 1F), -68.5 (t, JF = 17.1 Hz, 1F), -94.7 to -95.2
(m, 1F); MS (EI, 70 eV) m/z (%) 243 (M+, 20), 201 (13), 200 (80),
186 (17), 184 (15), 173 (51), 172 (63), 170 (17), 160 (12) 159 (12),
158 (12), 157 (16), 152 (18), 147 (11), 146 (100), 138 (21), 57 (27),
56 (16), 55 (14).
(E,E)-3-Fluoro-2,4-bis(oct-4-en-4-yl)acetophenone (4na).
A
yellow oil, Rf 0.10 (hexane–ethyl acetate = 50 : 1). IR (neat) 2961,
2932, 2872, 1694, 1601, 1465, 1454, 1412, 1379, 1354, 1279, 1260,
1017, 891, 826, 743; 1H NMR (400 MHz, CDCl3) d 7.21 (d, J =
8.1 Hz, 1H), 7.09 (dd, J = 7.9, 7.0 Hz, 1H), 5.53 (t, J = 7.2 Hz,
1H), 5.35 (t, J = 7.3 Hz, 1H), 2.47 (s, 3H), 2.44 (t, J = 7.6 Hz,
2H), 2.36 (br, 2H), 2.184 (q, J = 7.7 Hz, 2H), 2.181 (q, J =
7.7 Hz, 2H), 1.53–1.22 (m, 8H), 0.97 (t, J = 7.3 Hz, 3H), 0.96 (t,
J = 7.3 Hz, 3H), 0.91 (t, J = 7.3 Hz, 3H), 0.86 (t, J = 7.4 Hz,
3H); 13C NMR (101 MHz, CDCl3) d 202.4 (d, JF = 34.1 Hz),
157.0 (d, JF = 245.6 Hz), 140.0 (d, JF = 33.0 Hz), 135.9, 134.6 (d,
J = 17.7 Hz), 133.6, 133.0, 132.6, 130.7 (d, JF = 20.1 Hz), 128.5
(d, JF = 5.5 Hz), 122.9 (d, JF = 3.9 Hz), 34.6 (d, JF = 1.5 Hz),
32.4 (d, JF = 3.4 Hz), 30.6, 30.5, 30.4, 22.9, 22.6, 21.7, 21.6, 14.6,
14.1, 14.03, 14.00; 19F NMR (282 MHz, CDCl3) d -116.2 (s, 1F);
MS (EI, 70 eV) m/z (%) 358 (M+, 18), 340 (16), 330 (35), 329
(89), 317 (23), 315 (100), 311 (16), 273 (41), 257 (22), 215 (13),
69 (16); HRMS (EI) Calcd for C24H35FO: M+, 358.2672. Found:
358.2670.
(E,E)-2,4,6-Trifluoro-3,5-di(oct-4-en-4-yl)pyridine
(4ra). A
yellow oil, Rf 0.20 (hexane); Anal. Calcd for C21H30F3N: C, 71.36;
H, 8.55. Found: C, 71.62; H, 8.77. IR (neat) 2948, 2926, 2855,
1
1585, 1458, 1423, 1377, 1045; H NMR (400 MHz, CDCl3) d
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©

5.51 (t, J = 7.3 Hz, 2H), 2.34 (t, J = 7.6 Hz, 4H), 2.20 (q, J =
7.3 Hz, 4H), 1.48 (sext, J = 7.3 Hz, 4H), 1.30 (sext, J = 7.5 Hz,
4H), 0.96 (t, J = 7.4 Hz, 6H), 0.89 (t, J = 7.3 Hz, 6H); 13C NMR
(101 MHz, CDCl3) d 167.1 (d, JF = 258.8 Hz), 157.0 (ddd, JF =
242.2, 18.5, 12.3 Hz), 135.5, 126.6, 112.1 (dd, JF = 22.3, 18.5 Hz),
32.5, 30.2, 22.6, 21.6, 13.9 (2C); 19F NMR (282 MHz, CDCl3) d
71.5 (d, JF = 17.2 Hz, 2F), -97.7 (t, JF = 18.0 Hz, 1F); MS (EI,
70 eV) m/z (%) 353 (M+, 21), 311 (22), 310 (100), 282 (17), 268
(18), 256 (14), 149 (13), 55 (10).
powder. X-Ray quality microcrystals of complex 9 (ca. 80 mg)
was then obtained by dissolving ca. 150 mg of complex 9 into ca.
4 mL of 1,4-dioxane at 60 ◦C and leaving the clear orange solution
overnight at room temperature (Fig. 1). Rf 0.40 (hexane only); mp
108.0–108.8 ◦C; Anal. Calcd for C40H62F5NiP: C, 66.03; H, 8.59.
Found: C, 65.97; H, 8.73. IR (KBr) 3422, 2930, 2849, 2820, 1681,
1632, 1607, 1559, 1541, 1518, 1464, 1439, 1422, 1377, 1362, 1331,
1298, 1279, 1267, 1174, 1128, 1109, 1088, 1051, 1037, 1003, 945,
897, 887, 849, 766, 733, 546, 534, 511, 492; 1H NMR (600 MHz,
C6D6) d 2.92–2.85 (m, 1H), 2.83–2.75 (m, 1H), 2.59–2.50 (m, 2H),
2.38–2.30 (m, 1H), 2.11–2.12 (m, 1H), 1.98–1.84 (m, 4H), 1.87–
1.68 (m, 3H), 1.68–1.20 (m, 28H), 1.20–1.07 (m, 6H), 1.07–0.84
(m, 12H), 0.75 (t, J = 7.2 Hz, 3H); 13C NMR (150 MHz, C6D6)
d 147.7 (dd, J = 219.0, 26.6 Hz), 145.9 (dd, J = 216.0, 29.4 Hz),
136.9 (dm, J = 216.9 Hz), 136.6 (dm, J = 223.5 Hz), 136.1 (dm,
J = 239.9 Hz), 130.9, 101.1 (t, J = 22.3 Hz), 91.7 (d, J = 18.7 Hz),
85.8, 44.4, 34.6 (d, J = 15.8 Hz), 33.1, 32.3, 31.9, 31.1, 29.7 (d,
J = 14.4 Hz); 27.9 (d, J = 7.9 Hz) (2C), 26.6, 22.9, 22.8, 21.5 (2C),
14.9, 14.7, 14.33, 14.27; 19F NMR (282 MHz, C6D6) d -108.0 (d,
J = 38.1 Hz, 1F), -112.7 (d, J = 38.1 Hz, 1F), -162.8 (d, J =
41.5 Hz, 1F), -163.5 to -164.0 (m, 1F), -164.1 to -164.6 (m, 1F);
31P NMR (121 MHz, C6D6) d 27.8 (s); MS (FAB+) 727 (M+ + 1,
12), 594 (14), 593 (17), 338 (14), 298 (38), 297 (100), 295 (13), 281
(22), 235 (13), 221 (36), 81 (13), 55 (18), 43 (13), 41 (10).
(E) - Dimethyl(2 - (pentafluorophenyl)2 - phenylethenyl) [2 - tetra -
hydro-2H-pyran-2-yloxy]methyl)phenyl]silane (3ag).
A yellow
oil, Rf 0.30 (hexane). Anal. Calcd for C28H27F5O2Si: C, 64.85; H,
5.25. Found: C, 64.95; H, 5.27. IR (neat) 3057, 2926, 2856, 1647,
1589, 1518, 1493, 1340, 1260, 1250, 1182, 1119, 1078, 1069, 1032,
907, 871, 851, 833, 816, 775, 749, 735, 700; 1H NMR (400 MHz,
CDCl3) d 7.47 (d, J = 7.5 Hz, 1H), 7.42 (dd, J = 7.5, 1.0 Hz, 1H),
7.38 (td, J = 7.5, 1.3 Hz, 1H), 7.26–7.18 (m, 2H), 7.15 (t, J =
7.5 Hz, 2H), 7.08 (d, J = 7.1 Hz, 2H), 6.28 (s, 1H), 4.84 (d, J =
12.1 Hz, 1H), 4.69 (t, J = 3.5 Hz, 1H), 4.57 (d, J = 12.3 Hz, 1H),
3.90 (ddd, J = 11.3, 8.4, 2.9 Hz, 1H), 3.53 (ddd, J = 10.9, 4.7,
4.1 Hz, 1H), 1.91–1.46 (m, 6H), 0.23 (s, 6H); 13C NMR (101 MHz,
CDCl3) d 143.5 (dm, JF = 248.0 Hz), 143.4, 142.9, 140.05, 139.99
(dm, JF = 258.6 Hz), 139.4, 137.3 (dm, JF = 253.4 Hz), 136.7,
134.4, 129.4, 128.1, 128.0, 127.8, 126.8, 119.5 (t, JF = 17.2 Hz),
109.7, 97.9, 68.9, 62.1, 30.7, 25.6, 19.5, -0.5; 19F NMR (282 MHz,
CDCl3) d -142.0 (d, JF = 24.6 Hz, 2F), -156.7 (d, JF = 24.6 Hz,
1F), -162.8 (t, JF = 24.4 Hz, 2F); MS (EI, 70 eV) m/z (%) 417
(M+ - OTHP, 11), 281 (10), 270 (11), 260 (11), 245 (16), 237 (14),
219 (11), 165 (18), 164 (19), 163 (29), 149 (44), 147 (11), 135 (10),
105 (17), 91 (24), 85 (100), 75 (10), 71 (11), 57 (43), 55 (14).
Measurement of KIE. In a glove box, a solution of Ni(cod)2
(1.7 mg, 6.0 mmol) and PCyp3 (1.4 mg, 6.0 mmol) in toluene
(0.6 mL) were added to a solution of 1p (36 mg, 0.20 mmol) placed
in a 3 mL vial. In another vial were placed the same catalyst and
1p-d1 in equimolar amount. To each vial were added 4-octyne
(22.0 mg, 0.2 mmol) and dodecane (internal standard, 17.0 mg,
0.10 mmol). Each vial was closed with a screw cap, and heated
Stoichiometric reaction of 1a with 5. Pentafluorobenzene (1a,
8.8 mg, 52 mmol) was added to a solution of Ni2N2(PCy3)4 (5,
32 mg, 25 mmol) dissolved in C6D6 (0.75 mL). Evolution of a gas
◦
at 30 C. Aliquots of the reaction mixture were taken from each
vial and analyzed by GC to monitor the reactions. The set of
experiments was repeated twice and the average yields for the
three sets were calculated and plotted in Fig. 2.
1
(nitrogen) was observed. The reaction was monitored by H, 31P
and 19F NMR spectroscopy.
(E)-6-(Oct-4-en-4-yl)-(E)-3-[1,4-bis(trimethylsilyl)but-2-en-2-
yl]-1,2,4,5-tetra-fluorobenzene (17). A yellow oil, Rf 0.60 (hexane
only). IR (neat) 2959, 2936, 2901, 2874, 1715, 1695, 1647, 1636,
1468, 1456, 1306, 1249, 1161, 1144, 1063, 974, 939, 895, 842, 758,
694; 1H NMR (400 MHz, CDCl3) d 5.52 (t, J = 7.5 Hz, 1H), 5.46
(t, J = 8.8 Hz, 1H), 2.38 (t, J = 7.5 Hz, 2H), 2.22 (q, J = 7.3 Hz,
2H), 1.87 (s, 2H), 1.61 (d, J = 8.6 Hz, 2H), 1.48 (sext, J = 7.3 Hz,
2H), 1.29 (sext, J = 7.4 Hz, 2H), 0.97 (t, J = 7.4 Hz, 3H), 0.89 (t,
J = 7.3 Hz, 3H), 0.07 (s, 9H), -0.08 (s, 9H); 13C NMR (101 MHz,
CDCl3) d 143.9 (dm, JF = 241.8 Hz), 143.6 (dm, JF = 241.8 Hz),
135.4, 129.0, 127.4, 122.8 (t, JF = 18.9 Hz), 121.7, 120.7 (t, JF =
18.5 Hz), 32.6, 30.3, 22.7, 21.7, 21.5, 20.1, 13.9 (2C), -1.2, -1.5;
19F NMR (282 MHz, CDCl3) d -143.7 (dd, JF = 26.6, 10.6 Hz,
2F), -144.4 (dd, JF = 24.0, 13.3 Hz, 2F); MS (EI, 70 eV) m/z (%)
458 (M+, 100), 328 (17), 74 (10), 73 (100); HRMS (EI) Calcd for
C24H38F4Si2: M+, 458.2448. Found: 458.2432.
Stoichiometric reaction of 1a with Ni(cod)2 and PCy3. Pentaflu-
orobenzene (1a, 16.8 mg, 0.100 mmol) was added to a solution of
Ni(cod)2 (28 mg, 0.100 mmol) and PCy3 (28 mg, 0.100 mmol or
56 mg, 0.20 mmol) ◦was dissolved in C6D6 (1.0 mL). The solution
1
was warmed to 50 C, and monitored by H, 31P and 19F NMR
spectroscopy.
Stoichiometric reaction of 1a with 5 then with an excess amount
of 1p. Pentafluorobenzene (1a, 8.8 mg, 52 mmol) was added to a
solution of Ni2N2(PCy3)4 (5, 32 mg, 25 mmol) dissolved in C6D6
(0.75 mL). The solution was stirred for 1 h, then 5 equivalents of
1,2,4,5-tetrafluoro-3-methoxybenzene (1p, 52 mg, 0.26 mmol) was
◦
added. The resulting solution was heated at 50 C for 24 h and
monitored by 31P NMR spectroscopy.
Synthesis of complex 9. In a glove box, pentafluorobenzene
(1a, 1.30 g, 8.0 mmol) was added to a solution of Ni(cod)2 (0.88 g,
3.2 mmol) and PCy3 (1.79 g, 6.4 mmol) dissolved in toluene
(10 mL). The solution was stirred for 5 min at rt, then 4-octyne
(1.32 g, 12.0 mmol) was added to the solution and stirred at 50 ◦C
for 40 min. The crude solution was then concentrated in vacuo.
The residue was purified by flash chromatography on silica gel to
give 3aa (0.33 g, 15%) and complex 9 (2.10 g, 36%) as a yellow
Palladium-catalysed arylation of 3da with 4-iodotoluene.
Pd(OAc)2 (6.0 mg, 25 mmol), K2CO3 (76 mg, 0.55 mmol) and 4-
iodotoluene (109 mg, 0.5 mmol) were measured into a 3.0 mL vial.
The vial was purged three times with argon and put into a glove
box. DMA (1.0 mL), P(t-Bu)2Me (6.0 mg, 50 mmol), 3da (130 mg,
0.5 mmol) and undecane (internal standard, 78 mg, 0.5 mmol) were
10492 | Dalton Trans., 2010, 39, 10483–10494
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added. The vial was closed with a screw cap, taken out from the
glove box and heated at 120 C for 120 h. The resulting mixture
(g) F. Kakiuchi and T. Kochi, Synthesis, 2008, 3013; (h) X. Chen, K. M.
Engle, D.-H. Wang and J.-Q. Yu, Angew. Chem., Int. Ed., 2009, 48, 5094;
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2009, 48, 9792; (j) D. A. Colby, R. G. Bergman and J. A. Ellman, Chem.
Rev., 2010, 110, 624; (k) C. C. C. Johansson and T. J. Colacot, Angew.
Chem., Int. Ed., 2010, 49, 696.
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U. Klabunde and G. W. Parshall, J. Am. Chem. Soc., 1972, 94, 9081;
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F. Maseras, O. Eisenstein, R. N. Perutz, K. B. Renkema and K. G.
Caulton, J. Am. Chem. Soc., 1998, 120, 12634; (d) F. Godoy, C. L.
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◦
was filtered through a silica gel pad and concentrated in vacuo.
The residue was purified by flash chromatography on silica gel
to give 4¢-methyl-(E)-4-(oct-4-en-4-yl)-2,3,5,6-tetrafluorobiphenyl
(18, 120 mg, 0.33 mmol, 66%) as a colourless solid, mp 55.6–
56.2 ◦C, Rf 0.35 (ethyl acetate–hexane = 100 : 1). Anal. Calcd for
C21H22F4: C, 71.98; H, 6.33. Found: C, 72.32; H, 6.52. IR (KBr)
3038, 3024, 2957, 2930, 2870, 2837, 1522, 1474, 1460, 1402, 1381,
1370, 1308, 1188, 1146, 1113, 1081, 1067, 1025, 970, 945, 905,
849, 818, 789, 766, 746, 712, 681, 583, 513; 1H NMR (400 MHz,
CDCl3) d 7.37 (d, J = 8.1 Hz, 2H), 7.30 (d, J = 8.1 Hz, 2H), 5.58
(t, J = 7.3 Hz, 1H), 2.43 (s, 3H), 2.42 (t, J = 7.5 Hz, 2H), 2.25
(q, J = 7.3 Hz, 2H), 1.50 (sext, J = 7.4 Hz, 2H), 1.37 (sext, J =
7.5 Hz, 2H), 0.99 (t, J = 7.3 Hz, 3H), 0.93 (t, J = 7.3 Hz, 3H); 13
C
10 (a) H.-Q. Do and O. Daugulis, J. Am. Chem. Soc., 2008, 130, 1128;
(b) H.-Q. Do, R. M. K. Khan and O. Daugulis, J. Am. Chem. Soc.,
2008, 130, 15185.
NMR (101 MHz, CDCl3) d 144.3 (dm, JF = 241.8 Hz), 143.6 (dm,
JF = 248.0 Hz), 138.8, 135.7, 129.8, 129.1, 127.4, 124.6, 121.9 (t,
JF = 19.3 Hz), 118.4 (t, JF = 16.5 Hz), 32.7, 30.3, 22.7, 21.6, 21.4,
13.9, 13.8; 19F NMR (282 MHz, CDCl3) d –143.6 (dd, JF = 49.9,
13.7 Hz, 2F), -145.8 (dd, JF = 24.8, 13.8 Hz, 2F); MS (EI, 70 eV)
m/z (%) 351 (M+ + 1, 27), 350 (M+, 85), 308 (48), 307 (100), 293
(16), 281 (11), 280 (56), 279 (48), 267 (12), 265 (14), 264 (16), 254
(17), 253 (76).
11 B. M. Trost, Science, 1991, 254, 1471.
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Acknowledgements
This work has been supported financially by a Grant-in-Aid
for Creative Scientific Research from MEXT. KSK acknowl-
edges Honjo International Scholarship Foundation for financial
support. The authors also thank Messrs Tamaki Takashi and
Hoshimoto Yoichi for their kind assistance in the synthesis of
Ni2N2(PCy3)4.
Notes and references
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