Strategy and design in fluorous phase immobilization: A systematic study of the effect of 'pony tails' (CH2)3(CF2)n-1CF3 on the partition coefficients of benzenoid compounds

Article abstract of DOI:10.1002/1099-1395(200010)13:10<596::AID-POC284>3.0.CO;2-M

Fluorous solvents commonly exhibit temperature-dependent miscibilities with organic solvents. Thus, catalysts and reagents that have high affinities for fluorous solvents can be used in protocols that combine the advantages of one-phase chemistry (higher temperature) and biphase product separation (lower temperature). The high-yield conversion of benzaldehydes (via Wittig and hydrogenation reactions) to alkylbenzenes with one to three 'pony tails' (CH₂)₃(CF₂)_n-1CF₃ (n = 6, 8, 10) is described. The toluene-CF₃C₆F₁₁ partition coefficients show that three pony tails are necessary to achieve a high degree of fluorous phase immobilization. Copyright

Full text of DOI:10.1002/1099-1395(200010)13:10<596::AID-POC284>3.0.CO;2-M

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY
J. Phys. Org. Chem. 2000; 13: 596–603
Strategy and design in ¯uorous phase immobilization:
a systematic study of the effect of `pony tails'
(CH2)3(CF2)n 1CF3 on the partition coef®cients of
benzenoid compounds
Christian Rocaboy,1,2 Drew Rutherford,1 Byron L. Bennett1 and J. A. Gladysz1,2
*
1Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, USA
2Organische Chemie, Friedrich-Alexander UniversitaÈt Erlangen-NuÈ rnberg, Henkestrasse 42, 91054 Erlangen, Germany
Received 17 October 1999; revised 15 February 2000; accepted 24 February 2000
ABSTRACT: Fluorous solvents commonly exhibit temperature-dependent miscibilities with organic solvents. Thus,
catalysts and reagents that have high affinities for fluorous solvents can be used in protocols that combine the
advantages of one-phase chemistry (higher temperature) and biphase product separation (lower temperature). The
high-yield conversion of benzaldehydes (via Wittig and hydrogenation reactions) to alkylbenzenes with one to three
‘pony tails’ (CH2)3(CF2)n 1CF3 (n = 6, 8, 10) is described. The toluene–CF3C6F11 partition coefficients show that
three pony tails are necessary to achieve a high degree of fluorous phase immobilization. Copyright 2000 John
Wiley & Sons, Ltd.
KEYWORDS: fluorous solvents; pony tails; phosphonium salts; Wittig reaction; alkylbenzenes; partition
coefficients
INTRODUCTION
cient numbers and lengths. The (CH2)m segments serve
to insulate the active site from the electron-withdrawing
fluorines.
The term ‘fluorous’ was recently introduced by Horva´th
and co-workers as an analog to ‘aqueous’ for highly
fluorinated alkane, ether and tertiary amine solvents.1–4
Many such solvents are commercially available, and are
very non-polar. They commonly give bilayers with
organic solvents at room temperature, as illustrated by
the first flask in Fig. 1. At the same time, many such
solvent combinations become miscible at elevated
temperatures, as depicted by the second flask in Fig. 1.
Various practical considerations and underlying physical
principles have been reviewed.4
Organic compounds normally have low affinities for
fluorous solvents. However, compounds that consist
mainly of perfluoroalkyl segments show high affinities.
This reflects a ‘like dissolves like’ effect, and similar
strategies are used to design dyes that can adhere to
Teflon.5 Accordingly, Horva´th and co-workers proposed
that high fluorous affinities could be imparted to common
catalysts and reagents by appending ‘pony tails’
(CH2)m(CF2)n 1CF3 [abbreviated to (CH2)mRfn] in suffi-
This provides the basis for an innovative new approach
to recoverable catalysts and reagents that combines the
advantages of one-phase chemistry (higher temperature)
and biphase product separation (lower temperature). As
illustrated by the second and third flasks in Fig. 1, a
homogeneous reaction can be followed by a simple room
temperature extraction. The organic product is isolated
from the non-fluorous solvent, and the catalyst or
transformed reagent from the fluorous solvent. Many
applications of this protocol have been developed over
the last few years.6,7
This concept was extended by Curran and Wipf, who
developed fluorous ‘tagging’ strategies that facilitate
target isolation from complex multi-component mix-
tures.8 Regardless of application, there is a distinct need
for quantitative data on the partitioning of solutes
between fluorous and non-fluorous solvents. We and
others have favored perfluoro(methylcyclohexane),
CF3C6F11, for various types of physical measurements.
Although this is a relatively expensive fluorous solvent, it
is available in high purity and without the branched
isomers commonly found in technical-grade acyclic
alkanes and perfluoroalkanes.
*Correspondence to: J. A. Gladysz, Institut fu¨r Organische Chemie,
Friedrich-Alexander Universita¨t Erlangen-Nu¨rnberg, Henkestrasse 42,
91054 Erlangen, Germany.
E-mail: gladysz@organik.uni-erlangen.de
Contract/grant sponsor: US Department of Energy.
Contract/grant sponsor: National Science Foundation.
Contract/grant sponsor: Deutsche Forschungsgemeinschaft.
In this paper, we address the following question: what
type of pony tail motif is necessary to impart high
Copyright 2000 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2000; 13: 596–603

REACTIONS IN ‘PONY TAILS’ FLUOROUS SOLVENTS
597
Figure 1. One possibility for catalysis with ¯uorous solvents [Rmfn = (CH2)m(CF2)n 1CF3]
of benzenoid compounds is also of considerable practical
importance. For example, there would be numerous
applications for catalysts based upon fluorous triaryl-
phosphine ligands. Catalysts with fluorous trialkylphos-
phine ligands have been spectacularly successful1–3,6d,f
but for many purposes triarylphosphines are superior or
required.6b
Scheme 1. Syntheses of ¯uorous phosphonium salts
partition coefficients to benzenoid compounds? In
general, arene p clouds afford significant intermolecular
dipole and induced dipole interactions,9 leading to
enhanced polarities and organic phase affinities.4 Thus,
perfluorinated arenes are normally miscible with organic
solvents. Furthermore, attractive arene–perfluoroarene
stacking interactions are used as design elements in
crystal engineering.10 The fluorous phase immobilization
RESULTS
We sought to graft pony tails on to aromatic aldehydes
using the Wittig reaction. Hence the commercially
available fluorous primary iodides ICH2CH2Rfn (n = 6,
8, 10) were converted on 12–26 g scales to the
Scheme 2. Syntheses of ¯uorous benzenes
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598
C. ROCABOY ET AL.
‡
Table 1. Partition coef®cients (24°C)
corresponding phosphonium salts [Ph3PCH2CH2Rfn] I
(6–8), as shown in Scheme 1. Forcing conditions were
required owing to the attenuated SN2 reactivity of the
iodides.6a,c Although 6 and 7 have been reported
earlier,11 few spectroscopic properties have been de-
scribed. Hence 6–8 were characterized by microanalysis
and NMR (1H, 13C, 31P, 19F), as detailed in the
Experimental section.
No.
Compound
CF3C6F11/CH3C6H5
49.5:50.5
14
15
16
91.2:8.8
The Wittig reagent derived from the deprotonation of
7 has previously been shown to condense with alde-
hydes.11a Analogous reactions with the benzenoid
mono-, di- and trialdehydes C6H6 x(CHO)x shown in
Scheme 2 (1–5) gave the corresponding alkenes
90.7:9.3
C6H6 x(CH=CHCH2Rf8)x (9–13) as mixtures of Z/E
isomers in 94–78% yields. NMR showed that Z isomers
3
17
18
91.1:8.9
dominated (assigned from JHH values), consistent with
literature precedent for unstabilized ylides.13 No effort
was made to separate these mixtures, which were
characterized by microanalysis and NMR. A synthesis
of 9, as a mixture with other compounds, has been
previously reported.12
>99.7:<0.3
Although both n-BuLi ( 78°C, THF) and K2CO3
(95°C, aqueous 1,4-dioxane) could be used to generate
the Wittig reagents, the latter proved superior. Any
excess of n-BuLi effected small amounts of 1,2-HF
elimination from 9–13, which contain activated allylic
protons. The by-products are difficult to detect in the Z/E
mixtures, but become more apparent after subsequent
steps. Importantly, the statistical probability of elimina-
tion increases with the number of pony tails.
As shown in Scheme 2, the alkenes underwent facile
hydrogenation in the presence of 10 mol% palladium on
carbon. Workups gave the family of mono-, di- and
trialkylbenzenes C6H6 x(CH2CH2CH2Rf8)x displayed in
Table 1 (14–18) in 92–80% yields. The sequence starting
from the o-dialdehyde 2 was repeated with phosphonium
salts 6 and 8. This gave two additional alkenes with
shorter and longer pony tails, 1,2-C6H4(CH=CHCH2Rf6)2
21
22
73.7:26.3
97.4:2.6
23
24
25
26
27
28
29
50.7:49.3
5.4:94.6
4.2:95.8
3.4:96.6
2.4:97.6
1.9:98.1
1.1:98.9
(19) and 1,2-C6H4(CH=CHCH2Rf10 2
corresponding o-dialkylbenzenes 1,2-C6H4(CH2CH2-
CH2Rf6)2 (21) and 1,2-C6H4(CH2CH2CH2Rf10 2 (22).
)
(20), and the
)
All alkylbenzenes were characterized by microanalysis
30
31
1.2:98.8
0.9:99.1
and NMR (1H, 13C and in some cases 19F).
Absolute solubilities decreased dramatically as the
pony tails became longer in the o-dialkylbenzenes 21, 15
and 22. Compound 22 was only sparingly soluble in
CF3C6F11. The p-dialkylbenzene 17 was less soluble than
the ortho and meta isomers 15 and 16. However, the
trialkylbenzene 18, in which the ratio of perfluorinated to
unfluorinated carbons is similar to that of 22, remained
highly soluble in CH2Cl2, CHCl3, THF, diethyl ether,
hexane, CF3C6H5 and CF3C6F11 (sparingly soluble in
acetone and toluene; insoluble in MeOH and EtOH). The
CF3C6F11–toluene partition coefficients were determined
by GLC as reported previously4,6c and further described
in the Experimental section. These reflect relative as
opposed to absolute solubilities, and are summarized in
32
33
22.4:77.6
28.0:72.0
Copyright 2000 John Wiley & Sons, Ltd.
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REACTIONS IN ‘PONY TAILS’ FLUOROUS SOLVENTS
599
Table 1. Values for related compounds are also given,
and analyzed in the Discussion section.
above, fluorinated arenes are highly soluble in moder-
ately polar solvents. However, 32 and 33 do show higher
fluorous phase affinities than the non-fluorinated alkyl-
benzenes.
The preceding data show that it will be challenging to
prepare functionalized benzenes or triarylphosphines that
are highly immobilized in fluorous phases. Partition
coefficients of 99:1 represent the lower practical limit for
many applications.1–3 With the types of pony tails
described in this paper, three would be required. This
raises the issue of substitution pattern. Any functional-
ized benzene derived from 18 will contain two ortho
substituents. With phosphines, this results in large cone
angles. This is desirable for some catalysts, but often
deleterious. A 3,4,5 (meta/para/meta') substitution pat-
tern would provide the best PPh3 mimic, but to our
knowledge the corresponding trialdehyde has never been
reported. Other synthetic approaches to functionalized
benzenes with three pony tails are, of course, possible.
However, it is difficult to avoid having at least one
substituent ortho to the functional group.
In summary, this work represents the first systematic
study of fluorous phase affinities of benzenoid com-
pounds bearing fluorous pony tails. Our data show the
immobilization of aromatic residues to be a challenging
but not necessarily insurmountable problem. The synth-
esis of functionalized fluorous benzenes and aromatic
heterocycles, and the corresponding partition coeffi-
cients, will be reported in the near future.
DISCUSSION
The protocol summarized in Scheme 2 represents a
versatile, general method for appending pony tails to non-
fluorous structures. Numerous aromatic aldehydes are
commercially available, and others are easily prepared.
This procedure gives pony tails with (CH2)3 insulating
segments, one methylene group more than in the starting
fluorous iodides. However, iodides with longer (CH2)m
segments, such as ICH2CH2CH2Rf8, are easily synthe-
sized.14 Hence higher homologs should be readily
available. Lower homologs would require phosphonium
‡
salts of the type [R3PCH2Rfn] X . These require
additional steps to access, but have been successfully
used in Wittig reactions.15
Other methods for appending (CH2)mRfn groups (m
ꢀ1) to benzenoid rings are known, as exemplified by
recent work with phosphine ligands designed to impart
good solubility in supercritical CO2.16 There are, of
course, numerous means of attaching perfluoroalkyl (Rfn)
groups directly to arenes. Several are nicely illustrated by
other recent work with fluorous phosphine ligands, where
the objective is often fluorous phase solubility as opposed
to highly biased partition coefficients.17,18 However,
Hammet s values of perfluoroalkyl groups (CF3/C4F9: sm
0.46/0.47–0.52; sp 0.53/0.52) indicate inductive electron-
withdrawing effects between those of chloride (sm 0.37)
and cyanide (sm 0.62; sp 0.71).19 Hence the electronic
properties of benzenoid compounds will be strongly
perturbed by such ‘uninsulated’ pony tails. Nonetheless,
in sufficient quantity they should be able to impart good
partitioning characteristics.
The data in Table 1 show that large numbers of CF2
groups are needed to immobilize benzene derivatives
effectively in fluorous phases. In the CH2CH2CH2Rf8
series, there is a gradual progression of partition
coefficients from ca 50:50 (14, one pony tail) to ca 91:9
(15–17, two pony tails) to >99:<1 (18, three pony tails).
Interestingly, the ortho, meta and para isomers give
essentially identical values. The partition coefficients of
the o-dialkylbenzenes increase from ca 74:26 (21) to ca
91:9 (15) to ca 97:3 (22) as the Rfn segment is lengthened
from six to eight to ten carbons.
EXPERIMENTAL
General. All reactions were conducted under inert
atmospheres unless noted otherwise. Chemicals were
treated as follows: THF, diethyl ether, toluene, hexanes,
distilled from Na–benzophenone; CH2Cl2, distilled from
CaH2; CF3C6H5 (Aldrich), CF3C6F11, CF3C6F5
(Oakwood or ABCR), distilled from P2O5; CDCl3
(Cambridge Isotope or Aldrich), other/‘reagent-grade’
solvents, ICH2CH2Rfn, C6H6 x(CHO)x (x = 1, 2), 1,3,5-
C6H3(CO2CH3)3 (all Oakwood or Aldrich), used as
received. The educt 1.3.5-C6H3(CH2OH)3 was prepared
from LiAlH4 (2.00 g, 57.7 mmol) and 1,3,5-
C6H3(CO2CH3)3 (5.80 g, 23.0 mmol) by the procedure
of Nakazaki et al.20 the crude product was chromato-
graphed on a silica gel column (eluent: 5:95 MeOH–
EtOAc); the solvent was removed by rotary evaporation
to give white crystals that were dried by oil pump vacuum
(3.05 g, 8.13 mmol, 79%), m.p. 74°C (lit. 74–75°C); 1H
NMR (ꢀ, CDCl3), 4.73 (s, 6H), 7.33 (s, 3H).
To help place these values in perspective, data for
related compounds are given in Table 1. When the phenyl
group in 14 is replaced by an iodide (23), the partition
coefficient is unaffected. The n-alkanes 24–29 have
similar numbers of carbons as the pony tails. As
expected, they show marked preferences for the toluene
phase (>94:<6) that increase with chain length. The non-
fluorinated alkylbenzenes 30 and 31 partition similarly.
Pentafluorobenzene (32) and hexafluorobenzene (33) also
prefer the toluene phase (78–72:22–28). As analyzed
NMR spectra were recorded on Varian FT or Jeol
JMN-400GX FT spectrometers (ambient probe tempera-
ture in CDCl3 unless noted and referenced as follows: 1H,
residual internal CHCl3 (ꢀ 7.27); 13C, internal CDCl3 (ꢀ
77.23); 31P, external 85% H3PO4 (ꢀ 0.00); 19F, external
CFCl3 (ꢀ 0.00)). Gas chromatography was conducted on
Copyright 2000 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2000; 13: 596–603

600
C. ROCABOY ET AL.
‡
Hewlett-Packard 5910 or ThermoQuest Trace GC 2000
instruments. Elemental analyses were conducted with a
Carlo Erba EA1110 instrument (in-house) or by Atlantic
Microlab (Norcross, GA, USA).
[Ph3PCH2CH2Rf10] I (8). Ph3P (5.716 g, 21.79 mmol),
ICH2CH2Rf10 (13.35 g, 19.81 mmol) and DMF (20 ml)
were combined in a procedure analogous to that for 6. An
identical workup gave 8 as a white solid (16.31 g,
17.41 mmol, 88%), m.p. 202–204°C. Calculated for
C30H19F21IP: C, 38.49; H, 2.05. Found: C, 38.28; H,
1,3,5-C6H3(CHO)3 (5)21. A Schlenk flask was charged
with 1,3,5-C6H3(CH2OH)3 (0.700 g, 416 mmol) and the
Dess–Martin reagent (6.18 g, 14.6 mmol).22 Then
CH2Cl2 (100 ml) was added and the suspension vigor-
ously stirred. After 15 h, diethyl ether (100 ml) was
added. The mixture was washed with Na2S2O3 [24.8 g
(100 mmol) in 100 ml of KHCO3-saturated H2O] and
saturated aqueous KHCO3 (100 ml). The combined
aqueous phases were extracted with CH2Cl2 (100 ml).
The CH2Cl2 phases were combined, dried (MgSO4) and
taken to dryness by rotary evaporation. The white powder
was flash chromatographed (CH2Cl2). The solvent was
removed by rotary evaporation to give 5 as star clusters of
white crystals (0.665 g, 4.10 mmol, 98%), m.p. 159°C
1
2.08%. NMR*: H 2.51 (m, CH2CF2), 4.01 (apparent
2
3
quin, JPH = 14 Hz, JHH = 7 Hz, PCH2), 7.68–7.87 (m,
15H); 13C{1H} (partial) 16.2 (d, JCP = 55 Hz, PCH2),
1
2
24.6 (t, JCF = 22 Hz, PCH2CH2), PPh at 116.6 (d,
1JCP = 72 Hz), 130.9 (d, JCP = 13 Hz), 133.8 (d,
2
3JCP = 10 Hz), 135.8 (d, JCP = 3 Hz); 31P{1H} 28.7 (s);
4
19F 81.3 (t, JFF = 9.0 Hz, CF3), 113.5 (br s, CF2),
3
122.4 (br s, 5CF2), 123.3 (br s, 2CF2), 126.7 (br s,
CF2).
C6H5CH=CHCH2Rf8 (9)12. A round-bottomed flask was
charged with C6H5CHO (0.200 g, 1.88 mmol), 7 (1.89 g,
2.26 mmol), K2CO3 (0.147 g, 2.45 mmol), reagent-grade
1,4-dioxane (10 ml) and H2O (0.3 ml) and fitted with a
condenser (no inert atmosphere). The mixture was stirred
at 95°C for 20 h. The volatiles were removed by rotary
evaporation, and CH2Cl2 (50 ml) and H2O (50 ml) were
added to the orange residue. The layers were separated.
The aqueous layer was extracted with CH2Cl2 (50 ml)
and the CH2Cl2 layers were combined and dried
(MgSO4). The solvent was removed by rotary evapora-
tion. The oily solid was rinsed through a silica gel plug
(10 cm) with hexanes. The solvent was removed by
rotary evaporation and oil pump vacuum to give 9 as a
colorless oil (0.953 g, 1.78 mmol, 94%, 90:10 Z/E).
Calculated for C17H9F17: C, 38.07; H, 1.69. Found: C,
38.29; H, 1.81%. NMR: 1H 3.21 2.97 (2dt,
1
(lit. 155.5–160°C).21 NMR: H 10.21 (s, 3H), 8.65 (s,
3H).
‡
[Ph3PCH2CH2Rf6]
I
(6)11. A flask was charged with
Ph3P (7.64 g, 29.13 mmol), ICH2CH2Rf6 (12.40 g,
26.16 mmol) and DMF (15 ml). The mixture was stirred
vigorously for 24 h at 105°C. The DMF was removed by
oil pump vacuum. The waxy solid was triturated with
diethyl ether (100 ml), collected by filtration, washed
with diethyl ether and dried by oil pump vacuum to give 6
as a white solid (16.95 g, 23.02 mmol, 88%), m.p. 191–
195°C. Calculated for C26H19F13IP: C, 42.42; H, 2.60.
Found: C, 42.26; H, 2.63%. NMR: 1H 2.58 (m, CH2CF2),
2
3
4.06 (apparent quin, JPH = 14 Hz, JHH = 7 Hz, PCH2),
7.69–7.93 (m, 15H); 13C{1H} (partial) 16.5 (dt,
3JHF = 18 Hz, JHH = 7 Hz, CH2CF2 E and Z), 5.78 (dt,
3
1JCP = 56 Hz,
3JCF = 4 Hz,
PCH2),
24.8
(td,
3JHH = 11 Hz, JHH = 7 Hz,
=
=
CHCH2, Z), 6.17 (dt,
3
2JCF = 23 Hz, JCP = 2 Hz, PCH2CH2), PPh at 116.9 (d,
3JHH = 16 Hz, JHH = 7 Hz,
CHCH2, E), 6.65 (d,
2
3
2
3
1JCP = 88 Hz), 131.2 (d, JCP = 13 Hz), 134.1 (d,
3JHH = 16 Hz, ArCH
=, E), 6.85 (d, JHH = 11 Hz,
3JCP = 11 Hz), 136.1 (d, JCP = 3 Hz); 31P{1H} 25.5 (s);
ArCH=
, Z), 7.20–7.45 (m, C6H5, Z and E); 13C{1H}
4
19F 81.4 (t, JFF = 9.3 Hz, CF3), 113.6 (br s, CF2),
(partial, Z) 30.7 (t, JCF = 22 Hz, CH2CF2), 118.1 (t,
3
2
122.4 (br s, CF2), 123.3 (br s, CF2), 123.4 (br s,
CF2), 126.8 (br s, CF2).
3JCF = 5 Hz,
136.2 (5s, C6H5CH
=
CHCH2), 127.8, 128.7, 128.8, 135.7,
).
=
‡
[Ph3PCH2CH2Rf8] I (7)11. Ph3P (13.20 g, 50.32 mmol),
1,2-C6H4(CH=CHCH2Rf8)2 (10). The reaction/workup
given for 9 was repeated with 1,2-C6H4(CHO)2 (0.160 g,
1.20 mmol), 7 (2.00 g, 2.39 mmol), K2CO3 (0.143 g,
2.39 mmol), reagent-grade 1,4-dioxane (15 ml) and H2O
(0.5 ml). This gave 10 as a colorless oil that solidified
upon standing (1.10 g, 1.10 mmol, 92%; 95:5 ZZ/EZ),
m.p. 59–60°C. Crystallization from hot hexanes gave
(ZZ)-10 as clear, colorless flakes. Calculated for
C28H12F34: C, 33.82; H, 1.21. Found: C, 33.72; H,
ICH2CH2Rf8 (26.11 g, 45.48 mmol) and DMF (20 ml)
were combined in a procedure analogous to that for 6. An
identical workup gave 7 as a white solid (34.73 g,
41.51 mmol, 91%), m.p. 174–175°C. Calculated for
C28H19F17IP: C, 40.22; H, 2.29. Found: C, 40.23; H,
2.32%. NMR: 1H 2.55 (m, CH2CF2), 4.04 (apparent quin,
2JPH = 14 Hz, JHH = 7 Hz, PCH2), 7.71–7.89 (m, 15H);
3
13C{1H} (partial) 16.3 (dt, JCP = 58 Hz, JCF = 3 Hz,
1
3
2
2
3
PCH2), 24.7 (td, JCF = 23 Hz, JCP = 3 Hz, PCH2CH2),
1.17%. NMR (ZZ): 1H 2.92 (dt, JHF = 18 Hz,
1
2
PPh at 116.8 (d, JCP = 87 Hz), 131.1 (d, JCP = 13 Hz),
3JHH = 7 Hz, 2CH2CF2), 5.82 (dt, 3JHH = 11 Hz,
133.9 (d, JCP = 10 Hz), 136.0 (d, JCP = 3 Hz); 31P{1H}
26.5 (s); 19F 81.3 (t, 3JFF = 9.0 Hz, CF3), 113.6 (br s,
CF2), 122.2 (br s, CF2), 122.5 (br s, 2CF2), 123.3 (br
s, 2CF2), 126.8 (br s, CF2).
3JHH = 7 Hz,
2=
CHCH2), 6.77 (d, JHH = 11 Hz,
3
4
3
2ArCH=), 7.20–7.23 (m, 2H), 7.32–7.34 (m, 2H);
2
13C{1H} (partial) 30.7 (t, JCF = 22 Hz, CH2CF2), 119.3
3
(t, JCF = 4 Hz,
=
CHCH2), 128.0, 129.1, 134.6, 135.1
Copyright 2000 John Wiley & Sons, Ltd.
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REACTIONS IN ‘PONY TAILS’ FLUOROUS SOLVENTS
3
601
3
[4s, C6H4(CH
=
)2]; 19F 78.0 (t, JFF = 12 Hz, 2CF3),
3JHH = 7 Hz,
2=CHCH2), 6.78 (d, JHH = 11 Hz,
110.1 (m, 2CF2), 119.0 (br s, 6CF2), 119.8 (br s,
2CF2), 120.2 (br s, 2CF2), 123.3 (br s, 2CF2).
2ArCH=), 7.22–7.26 (m, 2H), 7.30–7.35 (m, 2H);
2
13C{1H} (partial) 30.7 (t, JCF = 22 Hz, CH2CF2), 119.3
3
(t, JCF = 5 Hz,
=CHCH2), 128.0, 129.1, 134.6, 135.2
3
1,3-C6H4(CH=CHCH2Rf8)2 (11). The reaction/workup
given for 9 was repeated with 1,3-C6H4(CHO)2 (0.200 g,
1.491 mmol), 7 (3.74 g, 4.47 mmol), K2CO3 (0.268 g,
4.46 mmol), reagent-grade 1,4-dioxane (15 ml) and H2O
(0.5 ml). This gave 11 as a colorless oil (1.36 g,
1.36 mmol, 92%; 95:5 ZZ/EZ). Calculated for
C28H12F34: C, 33.82; H, 1.21. Found: C, 33.97; H,
[4s, C6H4(CH=
)2]; 19F 80.4 (t, JFF = 9 Hz, 2CF3),
112.5 (br s, 2CF2), 121.4 (br s, 2CF2), 122.3 (br s,
2CF2), 122.6 (br s, 2CF2), 125.7 (br s, 2CF2).
1,2-C6H4(CH=CHCH2Rf10)2 (20). The reaction/workup
given for 9 was repeated with 1,2-C6H4(CHO)2 (0.389 g,
2.90 mmol), 8 (8.14 g, 8.70 mmol), K2CO3 (0.522 g,
8.70 mmol), reagent-grade 1,4-dioxane (30 ml) and H2O
(0.5 ml). This gave 20 as a white solid (3.15 g,
2.63 mmol, 91%; 95:5 ZZ/EZ), m.p. 78–79°C. Calculated
for C32H12F42: C, 32.18; H, 1.01. Found: C, 32.33; H,
3
1.51%. NMR (ZZ): 1H 3.12 (dt, JHF = 18 Hz,
3JHH = 7 Hz, 2CH2CF2), 5.81 (dt, 3JHH = 11 Hz,
3
3JHH = 7 Hz, 2
=
CHCH2), 6.85 (d, JHH = 11 Hz,
ArCH=
), 7.10–7.42 (s, C6H4); 13C{1H} (partial) 30.7
(t, JCF = 22 Hz, CH2CF2), 118.8 (t, JCF = 4 Hz,
2
3
1
1.20%. NMR (ZZ): (in 50:50 COCl3–CF3C6F5) H 2.97
3
3
=CHCH2), 127.8, 128.4, 129.0, 134.4, 136.5 (5s,
(dt, JHF = 18 Hz, JHH = 7 Hz, 2CH2CF2), 5.87 (dt,
3
C6H4(CH=)2).
3JHH = 11 Hz, JHH = 7 Hz,
2=CHCH2), 6.85 (d,
3JHH = 11 Hz, ArCH ), 7.15–7.55 (m, C6H4); 13C{1H}
=
2
1,4-C6H4(CH=CHCH2Rf8)2 (12). The reaction/workup
given for 9 was repeated with 1,4-C6H4(CHO)2 (0.200 g,
1.491 mmol), 7 (3.74 g, 4.47 mmol), K2CO3 (0.268 g,
4.46 mmol), reagent grade 1,4-dioxane (15 ml) and H2O
(0.5 ml). This gave 12 as a white solid (1.34 g,
1.34 mmol, 90%; 95:5 ZZ/EZ), m.p. 62–63°C. Calculated
for C28H12F34: C, 33.82; H, 1.21. Found: C, 34.11; H,
(partial) 30.8 (t, JCF = 22 Hz, CH2CF2), 119.5 (t,
3JCF = 4 Hz,
CHCH2), 128.0, 129.3, 134.8, 135.5 [4s,
C6H4(CH )2].
=
=
C6H5CH2CH2CH2Rf8 (14). A Schlenk flask was charged
with 9 (1.24 g, 2.31 mmol), 10% Pd/C (0.150 g,
0.14 mmol), reagent-grade hexanes (10 ml) and absolute
EtOH (10 ml), purged with H2 (2–3 min) and fitted with a
thick-walled balloon filled with H2. The mixture was
stirred 24 h at room temperature and filtered through
Celite (5 cm plug). The volatiles were removed by rotary
evaporation and oil pump vacuum to give 14 as a
colorless oil (1.12 g, 2.08 mmol, 90%). Calculated for
C17H11F17: C, 37.93; H, 2.06. Found: C,. 37.81; H,
3
1.42%. NMR (ZZ): 1H 3.10 (dt, JHF = 18 Hz,
3JHH = 7 Hz, 2CH2CF2), 5.79 (dt, 3JHH = 11 Hz,
3
3JHH = 7 Hz,
2=
CHCH2), 6.83 (d, JHH = 11 Hz,
ArCH
2JCF = 22 Hz, CH2CF2), 118.6 (t, 3JCF = 4 Hz,
128.8, 135.2, 137.5 [3s, C6H4(CH )2].
=
), 7.24 (s, C6H4); 13C{1H} (partial) 30.8 (t,
CHCH2),
=
=
1
1,3,5-C6H3(CH=CHCH2Rf8)3 (13). The reaction/workup
given for 9 was repeated with 5 (0.190 g, 1.17 mmol), 7
(3.19 g, 3.81 mmol), K2CO3 (0.281 g, 4.694 mmol),
reagent-grade 1,4-dioxane (40 ml) and H2O (0.5 ml).
This gave 13 as a colorless oil that solidified upon
standing (1.33 g, 0.915 mmol, 78%, 94:6 ZZZ/EZZ), m.p.
36°C. Calculated for C39H15F51: C, 32.25; H, 1.04.
2.00%. NMR: H 1.93–2.21 (m, CH2CH2CF2), 2.73 (t,
3JHH = 7 Hz, ArCH2), 7.20–7.37 (m, C6H5); 13C (partial)
22.1 (br s), 30.6 (t, 2JCF = 22 Hz), 35.3 (s), 126.6, 128.6,
F
128.8, 140.9 (4s, C6H5); 19 80.1 (t, 3JFF = 12 Hz, CF3),
112.4 (br s, CF2), 119.8 (br s, 3CF2), 122.3 (br s,
CF2), 122.8 (br s, CF2), 125.3 (br s, CF2).
1
Found: C, 32.48; H, 1.13%. NMR (ZZZ): H 3.03 (dt,
1,2-C6H4(CH2CH2CH2Rf8)2 (15). The reaction given for
14 was repeated with 10 (1.23 g, 1.23 mmol), 10% Pd/C
(0.150 g, 0.14 mmol), reagent-grade hexanes (15 ml) and
absolute EtOH (15 ml) (18 h under H2). This gave 15 as a
white solid (1.11 g, 1.12 mmol, 91%), which was further
purified by rinsing through a silica gel plug (5 cm) with
hexanes (100 ml). Calculated for C28H16F34: C, 33.68; H,
3JHH = 7 Hz, 3JHF = 18 Hz, 3CH2CF2), 5.81 (dt,
3
3JHH = 11 Hz, JHH = 7 Hz,
3
=
CHCH2), 6.82 (d,
3JHH = 11 Hz, 3ArCH
(partial) 30.6 (t, JCF = 23.2 Hz, CH2CF2), 119.4 (t,
=
), 6.99 (s, C6H3); 13C{1H}
2
3JCF = 5 Hz,
C6H3(CH )3).
=CHCH2), 127.7, 135.1, 136.9 (3s,
=
1
1.61. Found: C, 33.43; H, 1.51%. NMR: H 1.91 (m,
1,2-C6H4(CH=CHCH2Rf6)2 (19). The reaction/workup
given for 9 was repeated with 1,2-C6H4(CHO)2 (0.910 g,
6.79 mmol), 6 (9.960 g, 13.53 mmol), K2CO3 (0.811 g,
13.53 mmol), reagent-grade 1,4-dioxane (40 ml) and
H2O (0.5 ml). This gave 19 as a colorless oil (4.423 g,
5.57 mmol, 82%; 89:11 ZZ/EZ). Calculated for
C24H12F26: C, 36.29; H, 1.52. Found: C, 36.57; H,
2CH2CH2CF2), 2.16 (m, 2CH2CF2), 2.72 (t, 3JHH = 8 Hz,
2ArCH2), 7.17–7.23 (m, C6H4); 13C{1H} (partial) 22.3
2
(br s), 31.1 (t, JCF = 22 Hz, CH2CF2), 32.3 (s), 127.3,
3
129.8, 139.0 (3s, C6H4); 19F 80.1 (t, JFF = 12 Hz,
2CF3), 112.2 (br s, 2CF2), 119.3 (br s, 6CF2), 119.8
(br s, 2CF2), 120.2 (br s, 2CF2), 123.3 (br s, 2CF2).
3
1.66%. NMR (ZZ): 1H 2.94 (dt, JHF = 18 Hz,
1,3-C6H4(CH2CH2CH2Rf8)2 (16). The reaction/workup
given for 15 was repeated with 11 (1.00 g, 1.00 mmol),
3JHH = 7 Hz, 2CH2CF2), 5.83 (dt, 3JHH = 11 Hz,
Copyright 2000 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2000; 13: 596–603

602
C. ROCABOY ET AL.
10% Pd/C (0.050 g, 0.05 mmol), reagent-grade CH2Cl2
(5 ml) and absolute EtOH (5 ml) (8 h under H2). This
gave 16 as a white solid (0.799 g, 0.800 mmol, 80%),
m.p. 68°C. Calculated for C28H16F34: C, 33.68; H, 1.61.
white solid (1.14 g, 0.951 mmol, 98%), m.p. 77–78°C.
Calculated for C32H16F42: C, 32.07; H, 1.34. Found: C,
1
32.35; H, 1.50% NMR (in 50:50 CDCl3–CF3C6F5). H
2.00 (m, 2CH2CH2CF2), 2.24 (m, 2CH2CF2), 2.81 (t,
3JHH = 8 Hz, 2ArCH2), 7.17–7.23 (m, C6H4); 13C{1H}
(partial) 22.1 (br s), 31.1 (t, 2JCF = 22 Hz, CH2CF2), 32.2
(s), 127.0, 129.0, 129.7 (3s, C6H4).
1
Found: C, 33.97; H, 1.83%. NMR: H 1.95–2.20 (m,
3
2CH2CH2CF2), 2.71 (t, JHH = 8 Hz, ArCH2), 7.04
(apparent t, 3H), 7.26 (m, 1H); 13C{1H} (partial) 22.0
2
(s), 30.4 (t, JCF = 22 Hz, CH2CF2), 35.1 (s), 126.6,
128.6, 129.0, 141.1 (4s, C6H4).
Partition coef®cients.4,6c. The following is representa-
tive. A 10 ml vial was charged with 15 (0.0240 g,
0.0240 mmol), CF3C6F11 (2.000 ml) and toluene
(2.000 ml), equipped with a Mininert valve, vigorously
shaken (2 min) and immersed (cap-level) in a 35°C oil-
bath. After 12 h, the bath was removed. After 12–24 h, a
0.400 ml aliquot of each layer was added to 2.000 ml of a
standard 0.0273 M solution of hexadecane in hexane. GC
analysis (average of 7–8 injections) showed that
0.00412 mmol of 15 was in the CF3C6F11 aliquot and
0.000398 mmol in the toluene aliquot (91.2:8.8; a 2.000/
0.400 scale factor gives a total mass recovery of 0.0222 g,
93%).
1,4-C6H4(CH2CH2CH2Rf8)2 (17). The reaction/workup
given for 15 was repeated with 12 (0.951 g, 0.956 mmol),
10% Pd/C (0.150 g, 0.141 mmol), reagent-grade
CF3C6H5 (10 ml) and absolute EtOH (10 ml) (18 h under
H2). This gave 17 as a white solid (0.918 g, 0.919 mmol,
96%), m.p. 84–85°C. Calculated for C28H16F34: C,
1
33.68; H, 1.61. Found: C, 34.03; H, 1.42%. NMR: H
3
1.92–2.14 (m, 2CH2CH2CF2), 2.72 (t, JHH = 8 Hz,
ArCH2), 7.14 (s, C6H4); 13C{1H} (partial) 22.1 (s), 30.5
2
(t, JCF = 22 Hz, CH2CF2), 34.8 (s), 128.9, 139.1 (2s,
C6H4).
1,3,5-C6H3(CH2CH2CH2Rf8)3 (18). The reaction given
for 14 was repeated with 13 (0.736 g, 0.506 mmol), 10%
Pd/C (0.150 g, 0.140 mmol), reagent-grade EtOH (10 ml)
and CF3C6H5 (10 ml) (12 h under H2). The mixture was
filtered through Celite (5 cm plug) that was further rinsed
with CF3C6H5 (3 Â 25 ml). The volatiles were removed
from the filtrate by rotary evaporation and oil pump
vacuum to give 18 as star clusters of white crystals
(0.677 g, 0.464 mmol, 92%), m.p. 60–61°C. Calculated
for C39H21F51: C, 32.11; H, 1.45. Found: C, 32.69; H,
Acknowledgements
We thank the US Department of Energy, the National
Science Foundation and the Deutsche Forschungsge-
meinschaft (DFG) for support of this research.
REFERENCES
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1.84%. NMR: H 1.91–2.10 (m, 3CH2CH2CF2), 2.69 (t,
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NMR: H 1.93 (m, 2CH2CH2CF2), 2.15 (m, 2CH2CF2),
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2.73 (t, JHH = 8 Hz, 2ArCH2), 7.17–7.24 (m, C6H4);
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J. Phys. Org. Chem. 2000; 13: 596–603