Siloxane based syntheses of fluorous ethenes and their tandem Heck reactions with aryl iodides

Article abstract of DOI:10.1016/j.jfluchem.2012.07.010

Perfluoroalkyl-ethenes (R_fnCHCH₂, 6a-c; a, n = 4; b, n = 6; c, n = 8) were prepared in good isolated yields (67-89%) and high purity (GC assay > 98%) from various fluorinated organosilanes in fluoride-anion assisted protodesilylation reactions. The environmentally more benign 'KF/NEt₃/H₂O' reagent combination introduced here was found as an effective substitute for the commonly used tetrabutylammonium- fluoride trihydrate (TBAF·3H₂O) as a fluoride source. Fluorous styrenes ((E)-R_fnCHCHAr, 8) were then prepared in good isolated yields (58-93%/iodoarene) and purities (GC assay > 95%) with the Pd(0) catalyzed Heck coupling of iodoarenes (Ar-I, 7) and perfluoroalkyl-ethenes generated in situ by the fluoride assisted cleavage of (β-perfluoroalkyl- α-iodo-ethyl)-siloxane ([R_fnCH₂CH(I)SiMe ₂]₂O, 3) precursors in DMF solution at elevated temperatures. They are accessible by the one-pot reaction of dimethylvinylchlorosilane (CH₂CHSiMe₂Cl, 2) and perfluoroalkyl iodides (R_fn-I, 1) as we reported earlier. Similarly, the radical chain addition of C₈F₁₇I to CH ₂CHSi(OMe)₃ (9) gave (β-perfluorooctyl-α-iodo- ethyl)-trimethoxysilane ([C₈F₁₇CH₂CH(I)]Si(OMe) ₃, 10) in good yield, which then was reacted with silica gel in dry toluene to obtain an SiO₂-bonded (perfluorooctyl)ethene surrogate [silica(O)₃SiCH(I)CH₂C₈F₁₇, 11]. The fluoride assisted cleavage of 11 and tandem Heck reaction with iodobenzene afforded the appropriate cross-coupled product (E)-C₈F ₁₇CHCHPh.

Full text of DOI:10.1016/j.jfluchem.2012.07.010

Journal of Fluorine Chemistry 144 (2012) 79–85
Contents lists available at SciVerse ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Siloxane based syntheses of fluorous ethenes and their tandem Heck reactions
with aryl iodides
´
*
´
´
´
Agnes Csapo, Jozsef Rabai
´
Institute of Chemistry, Eo¨tvo¨s Lorand University, P.O. Box 32, H-1518, Budapest 112, Hungary
A R T I C L E I N F O
A B S T R A C T
Article history:
Perfluoroalkyl-ethenes (RfnCH55CH2, 6a–c; a, n = 4; b, n = 6; c, n = 8) were prepared in good isolated
yields (67–89%) and high purity (GC assay > 98%) from various fluorinated organosilanes in fluoride-
anion assisted protodesilylation reactions. The environmentally more benign ‘KF/NEt3/H2O’ reagent
combination introduced here was found as an effective substitute for the commonly used
tetrabutylammonium-fluoride trihydrate (TBAFÁ3H2O) as a fluoride source. Fluorous styrenes ((E)-
RfnCH55CH–Ar, 8) were then prepared in good isolated yields (58–93%/iodoarene) and purities (GC
assay > 95%) with the Pd(0) catalyzed Heck coupling of iodoarenes (Ar-I, 7) and perfluoroalkyl-ethenes
Received 25 June 2012
Received in revised form 18 July 2012
Accepted 19 July 2012
Available online 27 July 2012
Keywords:
Phosphine-free Heck reaction
Protodesilylation
generated in situ by the fluoride assisted cleavage of
(b-perfluoroalkyl-a-iodo-ethyl)-siloxane
([RfnCH2CH(I)SiMe2]2O, 3) precursors in DMF solution at elevated temperatures. They are accessible
by the one-pot reaction of dimethylvinylchlorosilane (CH255CHSiMe2Cl, 2) and perfluoroalkyl iodides
(Rfn-I, 1) as we reported earlier. Similarly, the radical chain addition of C8F17I to CH255CHSi(OMe)3 (9)
Fluorous styrenes
Silica bonded ‘fluorous ethene equivalent’
gave (b-perfluorooctyl-a-iodo-ethyl)-trimethoxysilane ([C8F17CH2CH(I)]Si(OMe)3, 10) in good yield,
which then was reacted with silica gel in dry toluene to obtain an SiO2-bonded (perfluorooctyl)ethene
surrogate [silica(–O–)3Si–CH(I)CH2C8F17, 11]. The fluoride assisted cleavage of 11 and tandem Heck
reaction with iodobenzene afforded the appropriate cross-coupled product (E)-C8F17CH55CHPh.
ß 2012 Elsevier B.V. All rights reserved.
1. Introduction
donors and acceptors allowing this reaction. One of the benefits of
involving Heck reaction in a synthetic strategy is its outstanding
Organosilicon reagents are widely used in synthetic organic
chemistry, mostfrequentlyasprotectinggroupsforalcohols.Soluble
fluorides or some acids selectively remove the silyl groups when the
protection is no longer needed [1]. This reaction is often a FÀ assisted
cleavage reaction which is also called as protodesilylation.
The most common reagent for this purpose is tetrabutylam-
monium fluoride which commercially available in the form of
trihydrate (TBAFÁ3H2O) or as a stock solution in THF. Terminal
alkynes could be generated by the fluoride assisted cleavage
trans-selectivity [6].
Heck and other cross-coupling reactions have been instrumen-
tal for the development of metal-catalyzed organic syntheses [7].
The Heck reaction became an effective synthetic tool for fluorous
chemistry as well [8]. Palladium catalyzed olefination of haloarenes
with perfluoroalkyl-ethenes provides a convenient means for the
synthesis of fluorous aromatics [9]. Fluorous aryl compounds were
obtained by the arylation of olefins with an arenediazonium salt by
the cross-coupling of classical ArN2X with CnF2n+1CH55CH2 at room
temperature in methanol [10].
reaction of the corresponding RCBB CSiR3 precursors [2].
b-
Perfluoroalkyl- -iodoalkyl-silanes easily undergo dehydrohalo-
a
Here we disclose a new approach for the preparation of
fluorous aromatic compounds by Heck reaction, which is based
on the in situ generation of fluorous olefins using easily accessible
silane or disiloxane precursors. Such perfluoroalkyl-ethenes
(CnF2n+1CH55CH2) have been manufactured in a two-step proce-
dure starting with the radical addition of perfluoroalkyl iodides to
ethene in a pressure autoclave [11], which then was followed
by the dehydroiodination of the (perfluoroalkyl)ethyl iodide
intermediates with a suitable base (Scheme 1, upper path) [12].
Perfluoroalkyl-iodides (n-CnF2n+1I, RfnI, n = 2–14) with even
number of carbons are common sources of perfluoroalkyl-groups
[13], which became the ultimate precursors for the synthesis of
fluorous compounds [14].
genation with NEt3 to afford (E)-CnF2n+1CH55CHSiMe3 type
alkenyl silanes [3], or can be cleaved with TBAFÁ3H2O in a
simultaneous protodesilylation/dehydrohalogenation process to
give CnF2n+1CH55CH2 fluorous ethenes (Scheme 1; Q = SiMe3) [4].
The palladium-catalyzed C–C coupling between aryl or vinyl
halides and activated alkenes in the presence of a base is referred as
the Heck reaction [5]. Recent developments both in the catalysts
and reaction conditions have resulted in a much broader range of
* Corresponding author. Tel.: +36 1 372 2500; fax: +36 1 372 2592.
E-mail address: rabai@elte.hu (J. Ra´bai).
0022-1139/$ – see front matter ß 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jfluchem.2012.07.010

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A. Csapo´, J. Rabai / Journal of Fluorine Chemistry 144 (2012) 79–85
80
TBAF*3H2O in DMF
or KF/NEt3/H2O in DMF
n-CnF2n+1
3, 4, 5
reflux
6a-c
67-89%
Scheme 3. Preparation of fluorous ethenes via protodesilylation.
base, DMF, F-
Si-org
+
I
Pd(OAc)2
Rf4
Scheme 1. Alternative syntheses of fluorous ethenes (Q = SiMe3, SiMe2X, . . .).
31-47%
Section 4.5
8a
3a, 4a, 5a
7a
In this paper we aimed to generalize the above findings by
expanding the scope of the fluoride ion assisted cleavages of
appropriate silanes and siloxanes for the preparation and/or in situ
generation of terminal fluorous alkenes via combined dehydro-
halogenation protodesilylation (Scheme 1; Q = -SiMe2Cl or
(-SiMe2)2O.
Scheme 4. Tandem Heck-reactions with different olefin-sources.
TBAF*3H2O, DMF,
NEt3, Pd(OAc)2
Si Si
Rfn
O
Rfn
I
I
I
Rfn
7a
3a-c
8aa, 8ba, 8ca
2. Results and discussion
56-62 %
n = 4 (a), 6 (b), 8 (c)
We reported earlier a three step synthesis to fluorous alkenyl-
fluorosilanes (Scheme 2) [15].
Scheme 5. Tandem Heck coupling of 3a–c with C6H5I in the presence of TBAFÁ3H2O/
NEt3.
These silanes (3–5) were tested in a protodesilylation-reaction
with different reagents. First TBAFÁ3H2O was used to generate the
appropriate perfluoroalkyl-ethenes 6a–c, as it is the most
commonly used fluoride source in these reactions (Scheme 3).
It was found that all three organosilanes (3a, 4a and 5a)
undergo protodesilylation successfully in the presence of
Next ligand-free tandem Heck reactions with iodobenzene
substrate were developed using the above protodesilylation
methods for the in situ generation of the olefin partners. First all
the three organosilicon based (perfluorobutyl)ethene precursors
(3a, 4a and 5a) were tested using TBAFÁ3H2O as fluoride source,
Pd(OAc)2 as catalyst and NEt3 as a base in DMF solvent (Scheme 4).
All the three couplings were successful and styrene 8a was
isolated in 31–47% yields without optimization. This new tandem
Heck reaction may have some advantages compared to those
performed directly with olefins, since our silicon based olefin
precursors are easy to handle and less volatile liquids with long
shelf-life.
Since olefin precursors 3a, 4a and 5a gave similar isolated yields
in the Heck coupling reaction, for further studies compounds 3a–c
were chosen again. We have found that the length of the
perfluoroalkyl groups has no significant effect on the yield of
the coupling reaction (Scheme 5).
TBAFÁ3H2O in DMF (Table 1, entries 1–3). Since
b-perfluor-
oalkyl- -iodo-siloxanes 3 can be made in a one step procedure
a
(Scheme 2), we selected them for further studies instead of 4 and 5.
We tried to replace TBAFÁ3H2O with more environmentally benign
reagents for the protodesilylation of 3. These experiments revealed
that the KF/NEt3/H2O triad in DMF have the same or better
efficiency as TBAFÁ3H2O if at least stochiometric amount of water
was present (Table 1, entries 4–6). It is noteworthy that without
water the protodesilylation reaction does not take place. These
experiments explicitly prove that water behaves as a proton source
and the added water does not compromise nucleophilicity of the
fluorides supplied by potassium fluoride. The appropriate olefins
were isolated in excellent yields and purities using co-distillation
with pyridine [16].
Then we replaced the traditional TBAFÁ3H2O as a fluoride source
with the KF/NEt3 reagent pair in the next coupling reactions, since
the latter reagent combination showed similar reactivity in the
protodesilylation step. We have found that the KF/NEt3 system
have the same reactivity in the coupling reaction, too. We observed
These protodesilylation reactions using KF/NEt3/H2O triad are
more environmentally benign and less expensive than the
commonly used reactions with quaternary ammonium salts
whereas provide the same efficiency.
Scheme 2. Preparation of fluorous organosilanes from perfluoroalkyl-iodides.
Table 1
Olefin generation from organosilanes using different reagents.
Entry
Organosilane
Reagents
Isolated yield (%)
GC purity (%)
Product
1
2
3
4
5
6
Rf4–CH5CH–SiMe2F (5a)
TBAFÁ3H2O
TBAFÁ3H2O
TBAFÁ3H2O
KF/NEt3/H2O
KF/NEt3/H2O
KF/NEt3/H2O
89a
75a
73a
67b
70b
83b
98
98
98
98
99
98
Rf4–CH5CH2 (6a)
Rf4–CH5CH2 (6a)
Rf4–CH5CH2 (6a)
Rf4–CH5CH2 (6a)
Rf6–CH5CH2 (6b)
Rf8–CH5CH2 (6c)
(Rf4–CH5CH–SiMe2)2O (4a)
(Rf4–CH2–CHI-SiMe2)2O (3a)
(Rf4–CH2–CHI-SiMe2)2O (3a)
(Rf6–CH2–CHI-SiMe2)2O (3b)
(Rf8–CH2–CHI-SiMe2)2O (3c)
a
Isolation with distillation.
b
Isolation with distillation and pyridine-codistillation.

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A. Csapo´, J. Rabai / Journal of Fluorine Chemistry 144 (2012) 79–85
81
base consumed
L
Ph Pd
L
oxidative
addition
PhI
+
Pd0
I
OH-
H2O
reductive
Ph
Pd
I
Rf4
elimination
-I
Rf4
H
H2O
OH-
Ph
proto-
desilylation
F-
Si-org
Rf4
base generated
Scheme 6. Expected mechanism of the tandem Heck reaction.
Scheme 7. Tandem Heck-reaction of 3a with different iodoarenes 7a–i in the presence of KF/NEt3.
that no equivalent amount of water have to be used during the
tandem generation and coupling reaction of the perfluoroalkyl-
ethene intermediates, since the presence of only catalytic amount
of water is satisfactory as it is regenerated in the last – reductive
elimination – step of the catalytic cycle (Scheme 6).
presence of AIBN [19]. After the reagent was immobilized on silica
gel its load was calculated from microanalytical I% data. The
reaction of the immobilized reagent 11 and iodobenzene was
successful; the expected product (8ca) was isolated in 47% yield
and 96% purity as determined by GC. The co-product formed in
this reaction remains bonded to silica and can be removed by
filtration (cf. Section 4). Silica does not disturb this tandem
coupling reaction similarly to many reported techniques
using supported reactants and catalysts for Heck coupling
reactions [20].
Next the effect of the substituents of iodobenzenes (7a–i)
was tested using 3a in the presence of KF/NEt3 and Pd(OAc)2.
Substituted fluorous styrenes (8a–i) were isolated in good to
excellent yields (58–93%). However, our effort to expand the
scope to bromobenzene failed even in the presence of added
PPh3 (2 eq to Pd(OAc)2) or using other catalysts (Pd2dba3,
Pd(PPh3)4, (allyl-Pd-Cl)2) at 100 8C (Scheme 7 and Table 2).
An important requirement in the synthesis design is to avoid
the formation of co-products. Although separation of styrenes 8a–i
from the low-boiling organosilanes generated as by-products was
not troublesome, this step might be problematic in other similar
reactions affording more volatile target molecules. For ideal
separation of products and other reaction components after a
complete reaction the purposeful use of orthogonal phases should
be considered. Liquid–gas, solid–liquid, solid–gas and aqueous–
organic or organic–fluorous liquid–liquid phases are the best
known examples and generally accepted for strategy-level
separations [17].
Finally we have tested if these reactions could have
a
transmetallation step based mechanism which is characteristic
to Hiyama type mechanism. In opposite to the Heck mechanism
(Scheme 9, lower path) no base is required to proceed Hiyama’s
transmetallation mechanism (Scheme 9, upper path).
With disiloxane 4a and fluorosilane 5a no significant differ-
ence in the yields and reaction times was seen in the absence or
presence of the base, because their protodesilylation reaction
gave an equivalent amount of OHÀ, which in turn could react as a
base to assist HX elimination in the last step of the reaction (see
Scheme 6).
In case of a-iodoethylsiloxane 3a, the difference was significant,
since here one equivalent of acid (HI) is formed simultaneously
during the protodesilylation, which neutralizes the formed OHÀ
base (Scheme 10, Eq. (1)). In the presence of NEt3 the reaction takes
place with 100% conversion, while in the absence of that, the
reaction fails (0% conversion to iodobenzene; cf. Section 4.5,
Condition B).
These results strongly support our prediction, that these
reactions have a tandem Heck type mechanism, because if the
Hiyama type transmetallation step would be involved, than the
Here we disclose the synthesis of a novel functionalized
fluorous silica gel (11), which on the one hand could be used as a
solid phase supported (perfluoroalkyl)ethene precursor, or on the
other hand following the reductive removal of the
a-iodine
substituent could open up novel routes for the synthesis of
fluorous silica gels [18].
The synthesis of reagent 11 is shown in Scheme 8. In the first
step C8F17I was reacted with trimethoxyvinylsilane (9) in the
Scheme 8. Tandem Heck-reaction with a functionalized fluorous silica gel.

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A. Csapo´, J. Rabai / Journal of Fluorine Chemistry 144 (2012) 79–85
82
Table 2
Tandem Heck reaction of iodoarenes (7a–i) with
b-(perfluorobutyl)-a-iodoethyl-siloxane (3a).
Entry
1
Iodoarene
Yield (%)
60
GC purity (%)
95%
Product
Referencesa
[15]
I
Rf4
(8a)
(8b)
(7a)
I
2
3
4
85
66
63
96%
95%
95%
n.c.
[15].
[15]
OCH3
(7b)
(7c)
(8c)
(8d)
(7d)
5
6
70
93
95%
95%
n.c.
(7e)
(8e)
(8f)
[15]
(7f)
7
67
95%
[15]
(8g)
(7g)
8
9
58
75
95%
95%
[15]
[15]
(8h)
(8i)
(7h)
Rf4
I
(7i)
a
n.c. = new compound.
Scheme 9. Possible routes to the formation of fluorous syterenes – upper path: Hiyama type mechanism with a transmetalation step; lower path: tandem Heck type
mechanism.

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A. Csapo´, J. Rabai / Journal of Fluorine Chemistry 144 (2012) 79–85
83
2 H2O + 2 I-
+ 2 F- + 2 H2O
+ 2 F- + 2 H2O
+ F- + H2O
F-SiMe2-O-SiMe2-F
F-SiMe2-O-SiMe2-F
CH
6a
Eq. 1
Eq. 2
+ 2 H2C
Rf4
+
(Rf4-CH2-CHI-SiMe2)2O
3a
CH
6a
H2C
+ 2
Rf4 +
(Rf4-CH2=CH2-SiMe2)2O
2 OH-
4a
OH-
SiMe2F2
H2C CH Rf4
Rf4-CH2=CH2-SiMe2F
+
+
Eq. 3
6a
5a
Scheme 10. Stoichiometric representation of the protodesilylations (cf. Section 4.5).
reaction of 3a would have been completed to afford the fluorous
styrene Rf4CH55CHPh (8a), even in the absence of the base (cf.
Scheme 9).
4.2.2. Preparation of (perfluoroalkyl)-ethenes (6a–c) by the KF/NEt3/
H2O assisted cleavage of 3a–c in DMF (Table 1, entries 4–6)
In a round bottomed flask equipped for distillation was
placed the
a-iodoethylsiloxane (3a, 4.39 g, 5.0 mmol, or 3b,
3. Conclusions
5.39 g, 5.0 mmol, or 3c, 6.39 g, 5.0 mmol), KF (0.87 g, 15 mmol)
NEt3 (1.52 g, 15 mmol), H2O (0.27 g, 15 mmol) and 15 mL of
DMF. Then the mixture was stirred and heated at 160 8C with an
oil bath. The evolution of the title olefin started immediately and
the distillations were complete within 30 min. The biphasic
distillate was diluted with water and the lower phase was
separated and co-distilled with pyridine. The distillate was
washed with 5% HCl solution. The lower phase was separated
and dried over Na2SO4. Yields: 1.65 g (67% of 6a), or 2.42 g (70%
of 6b), or 3.70 g (83% of 6c) colorless oils, all with GC assay:
98–99%. The NMR data were in agreement with those
reported [4].
Easily accessible
b-(perfluoroalkyl)-a-iodoethyl-disiloxanes
and related fluorous organosilanes were used for the generation
of (perfluoroalkyl)-ethenes using more environmentally benign
reagents for protodesilylations.
Experimental evidence was given that the reaction of iodo-
benzenes and the above fluorous organosilicon derivatives under
specified condition could afford
yields involving an unusual fluoride-induced elimination–desily-
lation tandem Heck type mechanism.
v-perfluoroalkyl-styrenes in good
A new functionalized fluorous silica gel was developed as an
orthogonal solid phase (perfluoroalkyl)-ethene precursor to
simplify product separations.
4.2.3. Effect of the length of the fluorous chain on the coupling of
perfluoroalkyl-a-iodoethyl-siloxanes (3a–c) with iodobenzene (cf.
Scheme 5)
b-
4. Experimental
Under argon atmosphere in a round bottomed flask which is
equipped with a reflux condenser a mixture of (RfnCH2CHISi-
Me2)2O (3.38 g 3a, or 4.15 g 3b or 4.92 g 3c, 3.85 mmol), C6H5I (7a,
1.43 g, 7.0 mmol), TBAFÁ3H2O (3.31 g, 10.5 mmol), NEt3 (1.06 g,
10.5 mmol), Pd(OAc)2 (31 mg, 2 mol%) and DMF (16 mL) were
heated to 100 8C and stirred for 3 h. The product was isolated with
steam-distillation. The distillate (50 mL) was extracted with ether
(3 Â 15 mL) and the combined organic layers were dried (Na2SO4),
then the solvent was removed by evaporation (Rotavap). The crude
product was purified with flash chromatography (50 mL n-hexane,
2.5 cm  4 cm column, silica 60). Yield 1.40 g (62%/3a) of 8aa = 8a
(GC: 95%), 1.66 g (56%/3b) of 8ba (GC: 95%), and 2.12 g (58%/3c) of
8ca (GC: 97%). The spectroscopic data of products were in
agreement with those reported [15].
4.1. Materials and methods
Palladium(II)-acetate (99.9+%) and TBAF (Bu4NFÁ3H2O) were
purchased from Alfa Aesar. The other reagents and solvents were
purchased from Alfa Aesar or Molar (Hungary). Organosilicon
reagents (3–5) were synthesized as reported [15]. DMF was
distilled from CaH2 prior to use. Fluka Silica gel 60 (60,739) was
used for flash column chromatography and as support material.
NMR spectra were recorded at 298 K on Bruker Avance 250 MHz
spectrometer equipped with a QNP 1H/13C/19F/31P probe-head. 1H
and 13C spectra were referenced to the signal of chloroform.
Chemical shifts (
relatively to the internal standard TMS (
13C) and to CFCl3 as external standard ( = 0.00 for 19F). GC analyses
d
) are given in parts per million (ppm) units
d
= 0.00 for 1H,
d
= 0.00 for
d
were performed on a Hewlett–Packard 5890 Series II chromato-
graph, Column: PONA [crosslinked methylsilicone gum],
4.3. Tandem Heck-reactions with substituted iodobenzenes (General
Procedure-1, GP-1)
50 m  0.2 mm  0.5
280 8C).
mm, carrier gas: H2, FID detection (detector:
Under argon atmosphere in a round bottomed flask which is
equipped with a reflux condenser a mixture of (Rf4CH2CHISi-
Me2)2O (3a, 0.88 g, 1.0 mmol), iodoarene (7a–i, 0.7 mmol), KF
(0.12 g, 2.1 mmol), NEt3 (0.28 g, 2.8 mmol), Pd(OAc)2 (3.1 mg,
0.014 mmol, 2 mol%) and DMF (1.5 mL) were heated to 120 8C and
stirred for 5–14 h. The mixture was extracted with ether
(2 Â 15 mL) and the combined organic layers were dried (Na2SO4),
then the solvent was removed by evaporation (Rotavap). The crude
product was purified with flash chromatography (50 mL n-hexane,
2.5 cm  4 cm column, silica 60).
4.2. Preparation of (perfluorobutyl)-ethene
4.2.1. Preparation of (perfluorobutyl)-ethene (6a) by the TBAF
assisted cleavage of 3a, 4a, and 5a (Table 1, entries1–3)
In a round bottomed flask equipped for distillation was placed
the
a-iodoethylsiloxane (3a, 4.39 g, 5.0 mmol), or the alkenylsi-
loxane (4a, 3.11 g, 5.0 mmol), or the alkenylfluorosilane (5a, 3.22 g,
10 mmol), TBAFÁ3H2O (4.73 g, 15 mmol) and 10 mL of DMF,
respectively. Then the mixture was stirred and heated at 100 8C
with an oil bath. The evolution of the title olefin started
immediately and the distillations were complete within 30 min.
Yield: 2.19 g (89%/3a), or 1.85 g (75%/4a), or 1.80 g (73%/5a)
colorless oils, all with GC assay: 98%. The NMR data were in
agreement with those reported [4].
4.3.1. (E)-1-Methoxy-2-(3,3,4,4,5,5,6,6,6-nonafluoro-hexen-1-yl)-
benzene (8b)
The reaction was performed according to GP-1 using
2-iodoanisole (7b) (0.164 g, 0.70 mmol) for 5 h. Yield: 0.210 g
(85%), GC assay: 98%. 1H NMR (CDCl3):
d = 3.78 (s, 3 H, OCH3); 6.25

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A. Csapo´, J. Rabai / Journal of Fluorine Chemistry 144 (2012) 79–85
84
3
3
(dt, JHH = 16 Hz, JHF = 12 Hz, 1H, CF2–CH); 6.60–7.40 (m; 5H,
4.4. Preparation and use of a ‘silica supported b-perfluoroalkyl-a-
iodoethyl-trialkoxy-silane’ (11)
Ar–CH overlaps with aromatic protons). 13C NMR (CDCl3):
(s, OCH3), 111.4 (s, CAr), 114.9 (t, JCF = 23 Hz, CF2–CH), 120.9 (s;
d
= 55.7
2
C
Ar), 122.7 (CAr,ipso), 128.9 (s, CAr), 131.5 (s, CAr), 135.4 (t,
4.4.1. Synthesis of b-(n-perfluorooctyl)-a-iodoethyl-trimethoxy-
silane (10)
3JCF = 10 Hz, Ar–CH), 158.2 (s, CAr
,
ipso). 19F NMR (CDCl3):
3
d
= À81.55 (t, JFF = 10.5 Hz, 3F), À112.12 (m; 2F), À124.60 (m;
C8F17I (24.5 g, 45 mmol) and CH255CH–Si(OMe)3 (9, 5.04 g,
34 mmol) were placed into an oven dried round bottomed flask
which was equipped with a reflux condenser and magnetic stirrer
bar. The mixture was heated to 80 8C and azobisisobutyronitrile
(AIBN, 0.9 g, 5.5 mmol) was introduced in small increments during
2.5 h. It was stirred an additional 3 h at 80 8C. The product was
isolated by short-path distillation. Yield: 17.5 g (74%) of slightly
violet liquid, which was collected at 140 8C bath temperature @
0.10 mmHg pressure, GC assay: 92.5%.
2F), À126.20 (m; 2F). MS (EI, m/z) 183 (MeO–C6H4–CH55CH–CF2+),
163, 151, 133, 119 (C2F5+), 91 (C8H7), 77 (C6H5+), 69 (CF3+), 51
(C4H3+).
4.3.2. (E)-1-Methoxy-3-(3,3,4,4,5,5,6,6,6-nonafluoro-hexen-1-yl)-
benzene (8c)
The reaction was performed according to GP-1 using
3-iodoanisole (7c) (0.164 g, 0.70 mmol), for 5 h. Yield: 0.163 g
(66%), GC assay: 96%. The spectroscopic data were in agreement
with those reported [15].
1H NMR (CDCl3):
CHI), 3.65 (s, 9H, OCH3). 13C NMR (CDCl3):
2JCF = 21.5 Hz, CH2), 52.26 (s, OCH3). 19F NMR (CDCl3):
(t; 3JFF = 10.5 Hz; 3F); À116.0 (m; 2F); À122.2 (m; 2F); À122.5 (m,
4F), À123.3 (m; 2F); À124.2 (m; 2F); À126.7 (m; 2F).
Microanalysis for C13H12F17O3SiI = 694.19 g/mol; calculated I
18.28%; found I, 18.12%.
d
= 2.45–3.05 (m; 2H, CH2); 3.10–3.20 (m; 1H,
= À11.2 (s, CH), 34.7 (t,
d
d
= À81.39
4.3.3. (E)-1-Methoxy-4-(3,3,4,4,5,5,6,6,6-nonafluoro-hexen-1-yl)-
benzene (8d)
The reaction was performed according to GP-1 using
4-iodoanisole (7d) (0.164 g, 0.70 mmol), for 5 h. Yield: 0.155 g
(63%), GC assay: 95%. The spectroscopic data were in agreement
with those reported [15].
4.4.2. Immobilization of a fluorous-trimethoxysilane onto silica gel
Silica-gel 60 (20.0 g), trimethoxysilane derivative (10, 13.2 g,
19 mmol) and toluene (100 mL) was placed in a round bottomed
flask equipped with a reflux condenser, CaCl2 drying tube and
magnetic stirrer bar. The mixture was heated to 130 8C and stirred
for 28 h. The product was filtered by suction and washed with
acetone (100 mL) and n-hexane (100 mL) and dried on the air. The
yield is 31.1 g (99%) of white free flowing powder with 0.60 mmol/
g bonded silane. Microanalysis: calculated I, 7.77%; found I, 7.69%.
4.3.4. (E)-1-Chloro-2-(3,3,4,4,5,5,6,6,6-nonafluoro-hexen-1-yl)-
benzene (8e)
The reaction was performed according to GP-1 using 2-
chloroiodobenzene (7e) (0.167 g, 0.70 mmol), for 14 h. Yield:
0.175 g (70%), GC assay: 95%. 1H NMR (CDCl3):
d = 6.51 (dt,
3JHH = 16 Hz, JHF = 12 Hz, 1H, CF2–CH); 7.20–8.20 (m; 5H, Ar–CH
3
overlaps with aromatic protons). 13C NMR (CDCl3):
d = 117.2 (t,
2JCF = 23 Hz, CF2–CH), 127.4 (s; CAr), 128.1 (s, CAr), 129.6 (s, CAr),
130.3 (s; CAr), 131.3 (s; CAr), 134.7 (s, CAr), 136.5 (t, 3JCF = 10 Hz, Ar–
4.4.3. Coupling reaction of silica supported (perfluoroalkyl)-ethene
surrogate 11 and iodobenzene
CH). 19F NMR (CDCl3):
d
= À81.57 (t, JFF = 10.5 Hz, 3F), À111.70
3
(m; 2F), À124.60 (m; 2F), À126.20 (m; 2F). MS (m/z): 187 and 189
(Cl–C6H4–CH55CH–CF2+; 2:1 intensity ratio due to Cl izotopes), 167
and 169 (2:1 intensity ratio due to Cl izotopes), 151, 133, 119
(C2F5+), 77 (C6H5+), 69 (CF3+), 51 (C4H3+).
Under argon atmosphere in a round bottomed flask which is
equipped with a reflux condenser and magnetic stirrer bar a
mixture of 6a (1.43 g, 7.0 mmol), reagent 11 (16.7 g, 10 mmol
fluorous-ethene equivalent), KF (1.16 g, 20 mmol), NEt3 (3.0 g,
30 mmol), Pd(OAc)2 (16 mg, 0.067 mmol, 1 mol%) and DMF
(40 mL) was heated to 140 8C and stirred for 5 h. After the reaction
completed, the mixture was filtered, then the filtrate was diluted
with water (100 mL) and extracted with ether (3 Â 30 mL). The
combined organic layers were washed with water (3 Â 30 mL) and
dried (Na2SO4), then the solvent was removed by evaporation
(Rotavap). The crude product was purified with flash chromatog-
raphy (50 mL n-hexane, 2.5 cm  4 cm column, silica 60). Yield:
1.72 g (47%) of 8ca as a colorless oil, GC assay: 96%. The NMR data
were in agreement with those reported [15].
4.3.5. (E)-1-Methyl-2-(3,3,4,4,5,5,6,6,6-nonafluoro-hexen-1-yl)-
benzene (8f)
The reaction was performed according to GP-1 using
2-iodotoluene (7f) (0.153 g, 0.70 mmol), for 5 h. Yield: 0.220 g
(93%), GC assay: 95%. The spectroscopic data were in agreement
with those reported [15].
4.3.6. (E)-1-Methyl-4-(3,3,4,4,5,5,6,6,6-nonafluoro-hexen-1-yl)-
benzene (8g)
The reaction was performed according to GP-1 using
4-iodotoluene (7g) (0.153 g, 0.70 mmol), for 8 h. Yield: 0.158 g
(67%), GC assay: 95%. The spectroscopic data were in agreement
with those reported [15].
4.5. Cross-coupling reaction of the olefin sources 3a, 4a, and 5a with
iodobenzene (7a) in the presence of TBAF/NEt3, TBAF, or KF/NEt3
reagents yielding
v-(perfluorobutyl)-styrene (8a)
4.3.7. (E)-1-Trifluoromethyl-3-(3,3,4,4,5,5,6,6,6-nonafluoro-hexen-
1-yl)-benzene (8h)
The reaction was performed according to GP-1 using
3-iodobenzotrifluoride (7h) (0.190 g, 0.70 mmol), for 11 h. Yield:
0.158 g (58%), GC assay: 95%. The spectroscopic data were in
agreement with those reported [15].
Under argon atmosphere in a round bottomed flask which is
equipped with a reflux condenser a mixture of (Rf4CH2CHISi-
Me2)2O (3a, 0.97 g, 1.1 mmol), or (Rf4CH55CHSiMe2)2O (4a, 0.68 g,
1.1 mmol), or Rf4CH55CHSiMe2F (5a, 0.71 g, 2.2 mmol), respective-
ly, and C6H5I (7a, 0.41 g, 2.0 mmol), and the activator/base
[TBAFÁ3H2O (0.69 g, 2.2 mmol) and NEt3 (0.30 g, 3.0 mmol)
(Condition A), or TBAFÁ3H2O (0.69 g, 2.2 mmol) (Condition B), or
KF (0.13 g, 2.2 mmol) and 0.61 g (6.0 mmol) NEt3, (Condition C)
respectively], Pd(OAc)2 (9 mg, 2 mol%) and DMF (5 mL) was heated
to 100 8C and stirred for 1.5 h. Then the product was isolated with
steam-distillation. The distillate (50 mL) was extracted with ether
(3 Â 15 mL) and the combined organic layers were dried (Na2SO4),
then the solvent was removed by evaporation (Rotavap). The crude
4.3.8. (E)-1-(3,3,4,4,5,5,6,6,6-nonafluoro-hexen-1-yl)-naphtalene
(8i)
The reaction was performed according to GP-1 using
1-iodonaphtalene (7i) (0.178 g, 0.70 mmol), for 10 h. Yield:
0.195 g (75%) yellow oil. GC assay: 95%. The spectroscopic data
were in agreement with those reported [15].

´
´
A. Csapo´, J. Rabai / Journal of Fluorine Chemistry 144 (2012) 79–85
85
[7] For the evolution of metal-catalyzed organic synthesis, see: N. Miyaura, Advanced
Synthesis and Catalysis, 346 (2004) 1522–1523.
[8] (a) I.T. Horva´th, J. Ra´bai, Science 266 (1994) 72–75;
product was purified with flash chromatography (50 mL n-hexane,
2.5 cm  4 cm column, silica 60).
Condition A: yields: 0.30 g (47%/3a), or 0.30 g (47%/4a), or 0.20 g
(31%/5a) of colorless oils (with NEt3/TBAF).
(b) E.G. Hope, A.M. Stuart, Journal of Fluorine Chemistry 100 (1999) 75–83;
(c) J.A. Gladysz, D.P. Curran, I.T. Horva´th (Eds.), Handbook of Fluorous Chemistry,
Wiley-VCH, Weinheim, 2004;
(d) For changing designers issues in fluorous chemistry, see: A.E.C. Collis, I.T.
Horva´th, Catalysis Science and Technology, 1 (2011) 912–919;
Condition B: yields: 0.00 g (0%/3a), or 0.25 g (39%/4a), or 0.20 g
(31%/5a) of colorless oils (with TBAF).
´
(e) X. Zhao, W.Y. Ng, K.-C. Lau, A.E.C. Collis, I.T. Horvath, Physical Chemistry
Chemical Physics 14 (2012) 3909–3914.
Condition C: yields: 0.30 g (47%/3a), or 0.30 g (47%/4a), or 0.26 g
(40%/5a) of colorless oils (KF/NEt3). The NMR data for product 8a
were in agreement with those reported [15].
[9] (a) W. Chen, L. Xu, J. Xiao, Tetrahedron Letters 42 (2001) 4275–4278;
(b) W. Chen, L. Xu, J. Xiao, Organic Letters 2 (2000) 2675–2677.
[10] (a) J. Salabert, R.M. Sebastia´n, A. Vallribera, A. Roglans, C. Na´jera, Tetrahedron 67
(2011) 8659–8664;
Acknowledgements
(b) S. Darses, M. Pucheault, J.-P. Geneˆt, European Journal of Organic Chemistry 6
(2001) 1121–1128;
(c) K. Kikukawa, T. Matsuda, Chemistry Letters (1977) 159–162.
[11] (a) N.O. Brace, US Patent 3,016,406 (E. I. du Pont de Nemours and Company),
January 9, 1962 (application: September 21, 1960); Chem. Abstr. (1962) 57,
2078a.;
(b) W. Boechl, Neth. Appl. 6,506,069. 1965 November 15 (application: May 14,
1964); Chem. Abstr. (1966), 64, 17421c.
[12] N.O. Brace, L.W. Marshall, C.J. Pinson, G. van Wingerden, Journal of Organic
Chemistry 49 (1984) 2361–2368.
These investigations were supported by the Hungarian Scientific
Research Foundation (OTKA K062191 ‘‘Sustainable fluorous
chemistry’’). The European Union and the European Social Fund
have provided financial support to the project under the grant
´
´
´
agreement no. TAMOP_4.2.1./B-09/1/KMR-2010-0003. Agnes Csapo
thanks the ‘Sanofi-Aventis/Chinoin’ for a PhD fellowship. We
´
[13] P.M. Murphy, C.S. Baldwin, R.C. Buck, Journal of Fluorine Chemistry 138
(2012) 3–23.
´
´
thank Szilard Nasz and Aron Kramarics for analytical assistance.
[14] J. Ra´bai, in: J.A. Gladysz, D.P. Curran, I.T. Horvath (Eds.), Handbook of Fluorous
Chemistry, Wiley-VCH, Weinheim, 2004, pp. 156–174 (Chapter 9).
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