Syntheses and properties of fluorous quaternary phosphonium salts that bear four ponytails; new candidates for phase transfer catalysts and ionic liquids

Article abstract of DOI:10.1002/adsc.200606138

The fluorous tertiary phosphine [R_f6-(CH₂) ₂]₃P [R_fn = CF₃(CF₂) _n-1] and excess PhCH₂Br, CH₃(CH ₂)₃OSO₂CF_3<

Full text of DOI:10.1002/adsc.200606138

FULL PAPERS
DOI: 10.1002/adsc.200606138
Syntheses and Properties of Fluorous Quaternary Phosphonium
Salts that Bear Four Ponytails; New Candidates for Phase
Transfer Catalysts and Ionic Liquids
Charlotte Emnet,a Kathleen M. Weber,b JosØ A. Vidal,b Crestina S. Consorti,a
Alison M. Stuart,b,* and J. A. Gladysza,*
a
Institut für Organische Chemie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Henkestrasse 42, 91054 Erlangen,
Germany
Fax : (+49)-9131-85-26865; e-mail: gladysz@chemie.uni-erlangen.de
Department ofChemistry, University ofLeicester, Leicester, LE1 7RH, UK
b
Fax : (+44)-116-252-3789; e-mail: Alison.Stuart@le.ac.uk
Received: March 24, 2006; Accepted: June 13, 2006
Abstract: The fluorous tertiary phosphine [Rf6- moderately soluble, room temperature)>ace-
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points between 1108C and 438C, with lower values
favored by less symmetrical cations, Rf6 segments,
and triflate and bromide anions. Solubilities decrease Keywords: fluorous; ionic liquids; phase-transfer cat-
in the solvent sequence CF3C6F5 (all salts at least alysis; phosphines; phosphonium salts
Introduction
nature, allowing each ponytail to be individually con-
trolled. Horvµth, Knochel, and others have reported
Among numerous applications, phosphonium salts complementary methodologies.[12–14] We sought to
have attracted considerable recent attention as phase elaborate these phosphines into phosphonium salts
transfer catalysts[1] and ionic liquids.[2,3] Accordingly, with four ponytails. Some other fluorous phosphoni-
there is much interest in the development ofnew
classes ofphosphonium salts, and structure/property
um salts are known, as detailed in the discussion sec-
tion. However, they have either been reported with-
relationships. For example, over the last decade, a va- out characterization,[15] or feature at least one non-
[4,5]
riety ofnovel phase tags have been developed.
These represent possible vehicles for realizing phos-
fluorous substituent (e.g., C6H5, CH2CH2CN).[13]
In this paper, we describe convenient and easily
phonium salts with unusual characteristics. One scaled syntheses ofa variety ofsymmetrically- and
widely applied phase tag is the fluorous “ponytail”,[6] unsymmetrically-substituted phosphonium salts that
which most commonly has the formula CF3
(CH2)m [abbreviated Rfn(CH2)m].
A
-
bear three to four ponytails. We furthermore define
the liquid ranges ofthese salts and their solubilities in
A
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In previous studies, we have reported a variety of various solvents, quantify their abilities to transport
syntheses ofluf orous aliphatic primary, secondary, anions from aqueous to organic solutions, and demon-
and tertiary phosphines bearing Rfn(CH2)m substitu- strate their viability as phase transfer catalysts. Addi-
G
ents,[7–10] and related aromatic species.[7,11] Many of tional details can be found elsewhere.[16]
the routes to the aliphatic systems are modular in
Adv. Synth. Catal. 2006, 348, 1625 – 1634
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Charlotte Emnet et al.
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Results
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Syntheses of Fluorous Phosphonium Salts
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Two series ofsyntheses were conducted. The ifrst in-
volved the quaternization ofthe known symmetrically
R
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substituted fluorous tertiary phosphine, [Rf6
(CH2)2]3P ly from the alcohol using CBr4 and PPh3.[19] Interest-
A
(1).[7,8a] Two non-fluorous alkylating agents were stud- ingly, H2SO4 and aqueous HBr[20] gave only modest
ied first to provide reference compounds for the ex- conversions, even at temperatures of >1008C in
traction experiments below. As shown in Scheme 1, sealed vessels. As depicted in Scheme 2 (bottom), re-
reactions of 1 with an excess ofbenzyl bromide
(PhCH2Br) or n-butyl triflate [CH3(CH2)3OSO2CF3]
in benzotrifluoride (CF3C6H5) at elevated tempera- substituted phosphonium bromide [R
tures gave the phosphonium salts (PhCH2)
[Rf6- BrÀ (11) in 79% yield.
(CH2)2]3P+ BrÀ (2) and [CH3 (CH2)2]3P+
(CH2)3][Rf6 As shown in Scheme 3 (bottom), the unsymmetri-
action ofthe phosphine 6 and an excess ofR
-
f8
A
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AHCTREUNG
AHCTREUNG
A
G
A
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À
CF3SO3 (3) in 71–65% yields after work-up. These cally substituted phosphine 5 was prepared in 67%
and all new phosphorus-containing molecules below yield by free radical chain addition of the fluorous
were characterized by microanalysis, NMR spectros- primary phosphine R
f8(CH2)2PH2 (12)[10a] to the com-
A
copy (1H, 13C, 31P), and mass spectrometry, as sum- mercial fluorous alkene Rf6CH=CH2. Although 6 is a
marized in the Experimental Section. All NMR fea- known compound,[8a] it was also prepared by an anal-
tures were routine.
ogous reaction of 12 and Rf8CH=CH2 (65%). Both
As shown in Scheme 2 (top), 1 and the fluorous pri- reactions were easily conducted on 5-gram scales.
[17]
mary alkyl triflate R
G
were next Since 12 is conveniently synthesized by an Arbuzov/
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reacted. Fluorous alkylating agents are often much reduction sequence starting with R
f8(CH2)2I,[10a] the
less reactive than non-fluorous analogues,[5] and somewhat hazardous direct reaction ofPH
and
3
[8a]
somewhat higher temperatures were required than Rf8CH=CH2
with n-butyl triflate. Work-up gave the symmetrically
is avoided.
substituted
phosphonium
[R
f6(CH2)2]4P+
G
À
CF3SO3 (4) in 83% yield.
Phase Properties of Phosphonium Salts
In the second series ofsyntheses, a afmily ofphos-
phonium salts with all possible combinations ofR
-
All ofthe phosphonium salts were obtained as analyt-
f6
A
N
A
N
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scribed below – was employed as one starting materi- marized in Scheme 2, values for the salts with four po-
al. As shown in Scheme 2 (middle), reactions with ex- nytails ranged from 1108C to 438C. The melting
cesses ofthe lfuorous alkyl iodides R
8) in DMF at 1158C gave the phosphonium iodides mide and when Rf8 segments were replaced by short-
[Rf8(CH2)2][Rf6 (CH2)2]2 er Rf6 segments. It is well established that ionic liq-
(CH2)2]3P+ IÀ (7) and [Rf8
[Rf6
(CH2)2]2P+ IÀ (8) in 77–60% yields. Analogous uids with more symmetrical cations exhibit higher
reactions with the symmetrically substituted tertiary melting points than those with less symmetrical cat-
phosphine [R (CH2)2]3[Rf6- ions. Accordingly, the symmetrically substituted phos-
f8(CH2)2]3P (6)[8a] gave [Rf8
N
A
G
A
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A
N
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Scheme 1. Syntheses ofphosphonium salts with three fluorous substituents.
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Adv. Synth. Catal. 2006, 348, 1625 – 1634

Fluorous Quaternary Phosphonium Salts that Bear Four Ponytails
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Scheme 2. Syntheses of phosphonium salts with four fluorous substituents.
Scheme 3. Additional syntheses.
Adv. Synth. Catal. 2006, 348, 1625 – 1634
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Charlotte Emnet et al.
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Table 1. Solubility profiles of selected phosphonium salts.[a]
Solvent
Phosphonium salts[b–d]
4
7
10
11
CF3C6F11
CF3C6F5
CF3C6H5
sparingly soluble[b]
soluble[c]
sparingly soluble[b]
soluble[c]
insoluble[b]
insoluble[b]
soluble[c]
soluble[c]
very soluble[b,c]
very soluble[b,c]
moderately soluble[b]
very soluble[c]
insoluble[b]
moderately soluble[b]
soluble[c]
very soluble[b,c]
insoluble[b]
insoluble[b]
very soluble[c]
insoluble[b,c]
soluble[b]
soluble[c]
soluble[c]
CH3C6H5
acetone
insoluble[b,c]
insoluble[b,c]
insoluble[b,c]
insoluble[b]
very soluble[b,c]
sparingly soluble[b]
soluble[c]
very soluble[c]
moderately soluble[b]
soluble[c]
moderately soluble[c]
insoluble[b,c]
THF
moderately soluble[b]
soluble[c]
sparingly soluble[b]
moderately soluble[c]
insoluble[b,c]
Et2O
CH2Cl2
hexane
insoluble[b,c]
insoluble[b,c]
insoluble[b,c]
insoluble[b,c]
insoluble[b,c]
insoluble[b,c]
insoluble[b,c]
insoluble[b,c]
insoluble[b,c]
insoluble[b,c]
insoluble[b,c]
[a]
Based upon mass per unit volume and per descriptors in common chemistry handbooks.
218C.
[b]
[c]
[d]
Elevated temperature (4–108C below the boiling point ofthe solvent).
Data for 9: CF3C6F5, soluble,[b] very soluble.[c]
phonium salts 4, 10, and 11 show the higher melting the Experimental Section. The data are summarized
points. in Table 2. In the case of 4,>96% ofthe salt was
As summarized in Table 1, the solubilities of 4, 7, found in the fluorous phase employed, perfluoro(1,3-
10, and 11 were assayed in representative solvents at dimethylcyclohexane) [1,3-(CF3)2C6F10]. The triply
room and elevated temperatures. Solutions could be ponytailed phosphonium salt 2 was not very soluble
obtained with the fluorous solvent perfluoro(methyl- in this solvent. Hence, measurements were conducted
cyclohexane) (CF3C6F11) at elevated temperatures. in perfluorooctyl bromide [CF3(CF2)7Br]. It also ex-
G
The hybrid (ambiphilic)[21] solvent CF3C6H5 behaved hibited a significant fluorophilicity, with>93% ofthe
similarly. Interestingly, perfluorotoluene (CF3C6F5) – salt in the fluorous phase.
a non-fluorous or “organic” compound[21] – was the
best overall solvent, always giving solutions at room
temperature. In most cases, acetone and THF afford- Picrate Extraction Studies
ed solutions either at room or elevated temperatures.
No solubility was observed in hexane, CH3C6H5, One ofthe essential roles ofa classical phase transef r
Et2O, or CH2Cl2 under any conditions. All in all, solu- catalyst is to transfer the inorganic reagent from the
bilities decreased with increasing ponytail length, and aqueous phase into the organic phase, thus enabling
upon going from triflate to iodide to bromide. The the organic substrate to react with the transferred
former trend has been observed with many other anion and form the product in the organic phase reac-
[8a]
series offluorous compounds.
tion. Before examining applications of the fluorous
Selected fluorous/CH3C6H5 and fluorous/CH2Cl2 phosphonium salts in model phase transfer reactions,
partition coefficients were measured as described in selected salts were evaluated in potassium picrate ex-
traction experiments[22] in order to define their abili-
ties to transfer picrate from an aqueous phase into a
partially fluorinated phase (CF3C6H5) and a perfluori-
nated phase (CF3C6F5). As noted above, these are
best viewed as hybrid (ambiphilic) and organic (non-
fluorous) solvents, respectively.[21]
When either CF3C6H5 or CF3C6F5 was stirred with
an aqueous solution ofpotassium picrate, the aqueous
layer remained bright yellow due to the picrate anion
(lmax =356 nm) and the organic layer remained color-
less. Upon addition ofthe phosphonium salt, most of
the picrate color was transferred into the organic
phase. The efficiency of this extraction process was as-
sayed by measuring the decrease ofthe picrate con-
Table 2. Partition coefficients of selected phosphonium
salts.[a]
Salt Solvent system
Partition coefficient
(%)
Log
P
[b]
[b]
4
4
1,3-(CF3)2C6F10
CH3C6H5
1,3-(CF3)2C6F10
CH2Cl2
/
96.3/3.7
96.2/3.8
1.42
1.40
/
2
2
CF
CF3
C
96.5/3.5
93.9/6.1
1.44
1.18
[a]
[b]
218C.
Perfluoro(1,3-dimethylcyclohexane).
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Fluorous Quaternary Phosphonium Salts that Bear Four Ponytails
FULL PAPERS
centration in the aqueous phase using UV-visible
spectroscopy. The results are summarized in Table 3.
Table 3. Picrate extractions ofselected phosphonium salts. [a]
Figure 1. Phase transfer catalysis of a substitution reaction
by phosphonium salt 9.
Phosphonium salt
R4P+
Picrate extracted
[%]
CF3C6H5 CF3C6F5
XÀ
the fluorous alkyl iodide Rf8(CH2)3I (13) was overlay-
A
2
3
4
9
10
11
N
U
G
BrÀ
71.8
97.2
-
88.4
94.0
86.2
48.9
ered with an aqueous NaCl solution (ca. 1:10 13/
NaCl). This educt has one more methylene group
than the alkylating agent used in Scheme 2. The phos-
phonium salt 9 (10 mol%) was added. The sample
was stirred at 1008C in a sealed vial. After 2 h, a
1H NMR spectrum showed a ca. 50:50 mixture ofthe
À
G
N
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A
CF3SO3 65.8
G
(CH2)2]P+
IÀ
27.5
25.0
37.0
U
IÀ
E
BrÀ
[a]
fluorous alkyl chloride Rf8(CH2)3Cl (14) and 13. The
G
NaCl solution was replaced with a fresh charge, and
1
the cycle repeated twice (5.5 and 6 h). A H NMR
spectrum showed a>95:<5 14:13 ratio, with only a
All of the fluorous phosphonium salts performed trace of 13 detectable. No reaction occurred in the ab-
much better in the water/CF3C6F5 biphase than in the sence of 9. Hence, 9 can function as a catalyst for
water/CF3C6H5 biphase because oftheir higher solu-
bilities in CF3C6F5 at room temperature. Excellent
picrate extraction levels (97–86%) were obtained for
all ofthe salts, except ofr the phosphonium bromide
11 (49%), presumably due to its lower solubility in
CF3C6F5. The order ofpicrate extraction eifciency in
phase transfer from aqueous to organic phases.
Discussion
The reactions in Scheme 1 and Scheme 2 nicely estab-
CF3C6F5 was (PhCH2)
(CH2)2]3À[Rf6
(CH2)2]P+
CF3SO3 (4)>[Rf8
(CH2)2]4P+
C
G
R
N
E
IÀ
(9)>[Rf6
N
IÀ
G
iodide and triflate anions all readily undergo ex- the alkylation reactions. Any combination ofR
change in this system. (CH2)m and Rfn’
-
N
(CH2)mꢀ substituents with m ꢀ fn2
The four ponytailed phosphonium salts 9–11 give should be possible. The salts exhibit excellent thermal
much lower picrate extraction efficiencies in CF3C6H5 and air stabilities, and their yields can likely be fur-
(37–25%) than the phosphonium salts 2–4 (85–66%). ther optimized. From the data in Table 2, it can be as-
This is probably due to the much lower solubilities of sumed that partition coefficients will be very biased
9–11 in CF3C6H5. The results with 10 and 11 show towards fluorous phases, even when only three pony-
that bromide undergoes more efficient anion ex- tails are present.
change than iodide, despite the lower solubility ofthe
phosphonium bromide 11.
Horvµth has recently described similar sequences
starting with phenyl-substituted fluorous phosphines
ofthe of rmulae Ph
2/8).[13b] As shown in Scheme 4, reactions with Rfn’-
(CH2)3I (n’=6, 8) were effected in the absence of sol-
A
G
Phase Transfer Catalysis
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vent at 1408C. Consistent with the preparative goals
A demonstration ofthe viability ofthe preceding
ofthis work, the resulting phosphonium salts were
phosphonium salts as phase transfer catalysts was dearylated and converted to fluorous tertiary phos-
sought. As shown in Figure 1, a CF3C6F5 solution of phines. Other properties were not investigated.
Adv. Synth. Catal. 2006, 348, 1625 – 1634
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Charlotte Emnet et al.
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Scheme 4. Syntheses and reactions ofphenyl-substituted fluorous phosphonium salts.
The melting point data in Schemes 1 and 2 indicate
that this class ofphosphonium salts has particular
promise for the development of room temperature
ionic liquids. Although it was not a primary objective
ofthis study to minimize melting points, one salt ( 3,
Scheme 1) did not solidify at room temperature. Fur-
thermore, by combining the less symmetric cations, as
found in 7 and 8, with more polarizable anions, such
-
as CF3SO3 , there seem to be excellent prospects for
additional room temperature liquids.
Since fluorous ionic liquids might show specific
types ofinteractions with solutes, they constitute ex-
cellent candidates for what have been termed task-
specific ionic liquids (TSILs).[23] A variety ofionic liq-
uids are known with short Rfn segments (n<6). How-
ever, far fewer are known that contain longer Rfn seg-
ments (n ꢀ 6).[24] A representative series featuring
fluorous cations (15) is depicted in Figure 2.[24a] An
ionic liquid with a fluorous anion (16, Figure 2) has
been used as a solvent for the homogeneous hydrosi-
lylation ofalkenes catalyzed by a lfuorous version of
Wilkinsonꢁs catalyst.[24b]
To our knowledge, there has only been one previ-
ous report of a fluorous phase transfer catalyst, the
chiral quaternary ammonium salt 17 (Figure 2).[25]
This CH2Cl2-, CHCl3-, and Et2O-soluble species has
been applied in enantioselective alkylations ofactivat-
ed esters in aqueous/organic biphase systems. Due to
its highly fluorous nature, it can be efficiently recycled
by extraction with the fluorous solvent FC-72. The
perfluoroalkylated 4,13-diaza-18-crown-6 ether 18
(Figure 2) has also been developed recently as a re-
coverable phase transfer catalyst that promotes ali-
phatic and aromatic nucleophilic substitutions with
iodide and fluoride anions, respectively.[26] It can be
recycled six times by fluorous solid phase extraction
without any loss in activity.
Figure 2. Other fluorous ionic liquids or phase transfer cata-
lysts.
solids, and all have high fluorous phase affinities.
They efficiently extract picrate ions from aqueous to
suitable organic solvents, and their viability as phase
transfer catalysts has been demonstrated. Future re-
ports will detail extensions to fluorous arylphosphoni-
Conclusions
This study has established efficient routes to a variety um salts,[27] and additional applications in synthesis
ofsymmetrically and unsymmetrically substituted
quarternary fluorous phosphonium salts with three
and four ponytails. Many of these are low melting
and catalysis.[28]
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Fluorous Quaternary Phosphonium Salts that Bear Four Ponytails
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4
CF3), À114.25 (t, JFF =13.9 Hz, 6F, CF2CH2), À121.50 (m,
6F, CF2), À122.56 (m, 12F, 2 ” CF2), À125.91 (m, 6F, CF2);
MS (positive FAB, 3-NBA): m/z=1164 ([MÀBr]+, 100%);
MS (negative FAB, 3-NBA): m/z=79/81 (BrÀ, 100%).
Experimental Section
General Remarks
Reactions were conducted under a nitrogen or argon atmos-
phere unless noted. Chemicals were treated as follows:
Et2O and CH3C6H5, distilled from Na/benzophenone; DMF,
distilled from CaH2; hexanes and CH2Cl2, simple distilla-
tion; CF3C6H5 (Fluorochem or ABCR, 99%), distilled, or
distilled from P2O5, and freeze/pump/thaw degassed (3 ”);
CF3C6F11 (ABCR, 90%) and 1,3-(CF3)2C6F10 (Fluorochem,
À
A
G
G
(CH2)2]3P+ CF3SO3 (3)
The compounds CH3(CH2)3OSO2CF3 (0.60 g, 2.9 mmol), 1
G
(0.50 g, 0.47 mmol) and CF3C6H5 (5 mL) were combined in
a procedure analogous to that for 2 and stirred at 458C f or
48 h. An identical work-up gave 3 as a viscous oil; yield:
0.39 g (0.31 mmol, 65%); anal. calcd. for C29H21F42O3PS: C
27.24, H 1.66; found: C 27.36, H 1.52; 1H NMR (acetone-
d6): d=3.20 (m, 6H, CF2CH2CH2P), 2.99–2.84 (m, 8H,
CF2CH2, CH2CH2CH2P), 1.86 (m, 2H, CH2CH2P), 1.58 (m,
2H, CH3CH2), 0.98 (t, 3JHH =7.7 Hz, 3H, CH3); 13C{1H}
80+ %), distilled from CaH2; CF3(CF2)7Br (Fluorochem,
T
98%), simple distillation; CF3C6F5 (ABCR or Apollo,
98%), simple distillation; AIBN (Merck,>98%), Rf6CH=
CH2 (Lancaster, 99%), Rf8CH=CH2 (Apollo, 97%), Rf6-
A
G
A
R
ACHTREUNG
3
Acros, 98%), used as received. The potassium picrate was
prepared by the literature procedure using potassium car-
bonate as the base.[29] Other chemicals or materials were
used as received from common commercial sources.
NMR (acetone-d6): d=23.4 (d, JCP =19 Hz, CH3CH2), 23.3
(t,
CF2CH2),
22.9
(d,
JCP =5 Hz,
1
CH3CH2CH2), 17.6 (d, JCP =46 Hz, CH2CH2CH2P), 12.5 (s,
CH3), 10.6 (d, JCP =52 Hz, CF2CH2CH2P); 31P NMR (ace-
tone-d6): d=40.0 (s); 19F{1H NMR} (acetone-d6): d=
E
NMR spectra were recorded on Bruker Avance 300 MHz
or Jeol GX 400 MHz spectrometers at 27.08C in CDCl3,
acetone-d6, CF3C6F11 or CF3C6F5 and referenced as follows:
1H, residual internal CHCl3 (d=7.24 ppm) or acetone-d5
(d=2.05 ppm); 13C, internal CDCl3 (d=77.0 ppm) or ace-
tone-d6 (d=29.92 ppm); 31P, external H3PO4 (d=0.00 ppm);
19F, external CFCl3 (d=0.00 ppm). The highly coupled 13C
signals ofthe lfuorinated carbons are not listed below. Mass
spectra were recorded on a Micromass Zabspec instrument.
DSC and TGA data were recorded with a Mettler-Toledo
DSC821 apparatus and treated by standard methods.[30] Ele-
mental analyses were conducted on a Carlo Erba EA1110
instrument or were performed by the elemental analysis
service at the University ofNorth London.
À77.92 (s, 3F, CF3SO3), À80.81 (m, 9F, CF3), À114.23 (t,
4JFF =14.4 Hz, 6F, CF2CH2), À121.50 (m, 6F, CF2), À122.53
(m, 12F, 2 ” CF2), À125.86 (m, 6F, CF2); MS (positive FAB,
3-NBA): m/z=1129 ([MÀOSO2CF3]+, 100%); MS (nega-
tive FAB, 3-NBA): m/z=149 (CF3SO3À, 100%).
G
The compounds Rf6
(CH2)2OSO2CF3 (1.83 g, 3.69 mmol),[17]
1 (0.40 g, 0.37 mmol), and CF3C6H5 (3 mL) were combined
in a procedure analogous to that for 2 and stirred at 808C
for 37 h. The solvent was removed by rotary evaporation,
U
and the excess Rf6(CH2)2OSO2CF3 by Kugelrohr distillation
G
under reduced pressure. The oily solid was triturated with
CH3C6H5 and CH2Cl2. The residue was dried by oil pump
vacuum to give 4 as a white solid; yield: 0.48 g (0.31 mmol,
83%); mp 82–848C (capillary); anal. calcd. for
C33H16F55O3PS: C 25.27, H 1.03, P 1.97, S 2.04; found: C
A
G
R
A Schlenk flask was charged with [Rf6(CH2)2]3P (1; 1.01 g,
N
0.94 mmol),[7] PhCH2Br (0.96 g, 5.65 mmol), and CF3C6H5
(10 mL), and then freeze/pump/thaw/degassed. The sample
was stirred at 1108C for 24 h and cooled. The solvent was
removed by rotary evaporation. The viscous oil was triturat-
ed with hexane and CH3C6H5. The salt was dried under oil
pump vacuum and washed with Et2O. The Et2O was deca-
nted and the residue was dried by oil pump vacuum to give
2 as a white solid; yield: 0.82 g (0.66 mmol, 71%); mp 74–
808C (capillary); anal. calcd. for C31H19BrF39P: C 29.94, H
1.54, P 2.49, Br 6.43; found: C 29.46, H 1.45, P 2.10, Br 6.17;
1H NMR (acetone-d6): d=7.95 (m, 2H, PhH), 7.71 (m, 3H,
1
25.28, H 1.04, P 2.47, S 2.05; H NMR (acetone-d6): d=3.37
(m, 8H, CH2P), 3.11 (m, 8H, CF2CH2); 13C{1H} NMR (ace-
1
tone-d6): d=23.5 (t, 2JCF =23 Hz, CF2CH2), 10.8 (d, JCP
=
52 Hz, CH2P); 31P NMR (acetone-d6): d=42.4 (s); 19F{1H}
NMR (acetone-d6): d=À78.22 (s, 3F, OSO2CF3), À80.84 (m,
4
12F, CF3), À114.11 (t, JFF =13.3 Hz, 8F, CF2CH2), À121.51
(m, 8F, CF2), À122.59 (m, 16F, 2 ” CF2), À125.88 (m, 8F,
CF2);
MS
(positive
FAB,
3-NBA):
m/z=1419
([MÀOSO2CF3]+, 100%); MS (negative FAB, 3-NBA): m/
z=149 (CF3SO3À, 100%).
PhH), 5.13 (d, 2JHP =15.8 Hz, 2H, PhCH2), 3.60 (m, 6H,
CH2CH2P), 3.19 (m, 6H, CF2CH2); H
{31P} NMR (acetone-
1
d6): d=7.80 (m, 2H, PhH), 7.48 (m, 3H, PhH), 5.13 (s, 2H,
PhCH2), 3.60 (m, 6H, CH2CH2P), 3.19 (m, 6H, CF2CH2);
A
(CH2)2]
U
G
13C{1H} NMR (acetone-d6): d=130.8, 130.7, 129.8 (3 d,
2
J
CP =6, 3, 4 Hz, p/m/o-Ph), 129.5 (d, JCP =9 Hz, i-Ph), 27.2
A round-bottom flask was fitted with an N2 inlet and a con-
denser and charged with R
f8(CH2)2PH2 (12;[10a] 2.925 g,
6.095 mmol), Rf6CH=CH2 (7.632 g, 22.05 mmol), AIBN
(d, 1JCP =44 Hz, PhCH2), 25.0 (t, 2JCF =22 Hz, CF2CH2),
12.5 (d, 1JCP =51 Hz, CH2CH2P); 31P NMR (acetone-d6):
d=36.9 (s); 19F{1H} NMR (acetone-d6): d=À80.85 (m, 9F,
AHCTREUNG
(0.120 g, 0.731 mmol), and CH3C6H5 (7.0 mL). The solution
Adv. Synth. Catal. 2006, 348, 1625 – 1634
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.asc.wiley-vch.de
1631

Charlotte Emnet et al.
FULL PAPERS
was stirred at 908C for 36 h. A 31P NMR spectrum ofan ali-
quot showed that 12 was consumed, but that some inter-
mediate secondary phosphine remained. The sample was
cooled and the solvent removed by oil pump vacuum. An-
other charge ofR f6CH=CH2 (4.219 g, 12.19 mmol) and
AIBN (0.120 g, 0.731 mmol) was added. The mixture was
stirred at 908C for 48 h. The sample was cooled and the vol-
atiles removed by oil pump vacuum. The yellow-brown oil
was filtered through SiO2 (13 g; Ø 3.3 cm) with CF3C6H5
(300 mL). The solvent was removed by oil pump vacuum
and the light yellow oil distilled (Kugelrohr) to give 5 as a
colorless oil; yield: 4.766 g (4.066 mmol, 67%); bp 2208C/
0.06 torr; anal. calcd. for C26H12F43P: C 26.64, H 1.03;
8H, CH2P), 2.81 (m, 8H, CF2CH2); 13C{1H} NMR
(CF3C6F5
+
CDCl3 capillary): d=24.2 (t, 2JCF =24 Hz,
1
CF2CH2), 12.8 (d, JCP =54 Hz, CH2P); 31P NMR (CF3C6F5
+ CDCl3 capillary): d=40.4 (s); MS (positive FAB, 3-
NBA): m/z=1519 ([MÀI]+, 100%).
A
(CH2)2]2
G
N
DMF (1.5 mL), Rf8(CH2)2I (0.1797 g, 0.3131 mmol), and 5
E
(0.1223 g, 0.1044 mmol) were combined in a procedure anal-
ogous to that for 7. An identical work-up gave 8 as a yellow
solid; yield: 0.1411 g (0.0808 mmol, 77%); mp 648C (capil-
lary), 588C (DSC, Te); TGA: onset ofa 93% mass loss
203.58C; anal. calcd. for C36H16F60IP: C 24.76, H 0.92;
1
found: C 26.28, H 1.12; H NMR (CF3C6F11 + CDCl3 capil-
lary): d=2.13 (m, 6H, CH2P), 1.66 (m, 6H, CF2CH2);
13C{1H} 27.6 (dt, 2JCP =20 Hz, 2JCF =22 Hz, CF2CH2), 16.5
1
1
(d, JCP =17 Hz, CH2P); 31P NMR (CF3C6F11 + CDCl3 ca-
found: C 24.84, H 1.05; H NMR (CF3C6F5 + CDCl3 capil-
lary): d=3.48 (m, 8H, CH2P), 2.86 (m, 8H, CF2CH2);
13C{1H} NMR (CF3C6F5 + CDCl3 capillary): d=24.2 (t,
2JCF =24 Hz, CF2CH2), 12.9 (d, 1JCP =51 Hz, CH2P);
31P NMR (CF3C6F5 + CDCl3 capillary): d=40.5 (s); MS
(positive FAB, 3-NBA):=1619 ([MÀI]+, 100%).
pillary): d=À25.1 (s); MS (positive FAB, 3-NBA: m/z=
1189 ([M+H+O]+, 100%), 1172 ([M]+, 74%), 1153
([MÀF]+, 21%).
A
N
A
(CH2)2]3
E
A
The phosphine 12 (2.499 g, 5.206 mmol), Rf8CH=CH2
(8.402 g, 18.83 mmol), AIBN (0.103 g, 0.625 mmol), and
CH3C6H5 (6.0 mL) were combined in a procedure analogous
to that for 5 (908C, 48 h; second charge ofR f8CH=CH2
(4.645 g, 10.41 mmol) and AIBN (0.103 g, 0.625 mmol);
1008C, 24 h). The sample was cooled and the volatiles re-
moved by oil pump vacuum. The pale yellow solid was fil-
DMF (1.5 mL), Rf6(CH2)2I (0.2073 g, 0.4374 mmol), and 6
A
(0.3000 g, 0.2187 mmol) were combined in a procedure anal-
ogous to that for 7. An identical work-up gave 9 as a light
brown solid; yield: 0.2498 g (0.1353 mmol, 62%); mp 758C
(capillary), 708C (DSC, Te); TGA: onset ofa 89% mass
loss 197.38C; anal. calcd. for C38H16F64IP: C 24.72, H 0.87;
1
tered through SiO2 (26 g;
Ø 3.5 cm) with CF3C6H5
found: C 24.99, H 0.90; H NMR (CF3C6F5 + CDCl3 capil-
(300 mL). The solvent was removed by oil pump vacuum
and the solid recrystallized from CF3C6H5 (14 mL). This
gave 6 as a white solid; yield: 4.653 g (3.391 mmol, 65%);
mp 518C (capillary), 508C (DSC, Te); anal. calcd. for
C30H12F51P: C 26.26, H 0.88; found: C 25.89, H 0.97.
1H NMR (CF3C6F11 + CDCl3 capillary): d=2.11 (m, 6H,
lary): d=3.51 (m, 8H, CH2P), 2.87 (m, 8H, CF2CH2);
13C{1H} NMR (CF3C6F5 + CDCl3 capillary): d=24.4 (t,
2JCF =22 Hz, CF2CH2), 13.0 (d, 1JCP =53 Hz, CH2P);
31P NMR (CF3C6F5 + CDCl3 capillary): d=40.5 (s); MS
(positive FAB, 3-NBA): m/z=1719 ([MÀI]+, 100%).
CH2P), 1.61 (m, 6H, CF2CH2); 13C{1H} NMR (CF3C6F11
+
CDCl3 capillary): d=28.1 (dt, 2JCP =20 Hz, 2JCF =23 Hz,
A
U
1
CF2CH2), 17.0 (d, JCP =17 Hz, CH2P); 31P NMR (CF3C6F11
+ CDCl3 capillary): d=À25.1 (s); MS (positive FAB, 3-
NBA): m/z=1389 ([M+H+O]+, 100% vs. peaks with m/
z<1450), 1373 ([M+H]+, 80%), 1354 ([M+HÀF]+, 20%).
DMF (1.5 mL), Rf8(CH2)2I (0.4184 g, 0.7289 mmol), and 6
G
(0.5000 g, 0.3644 mmol) were combined in a procedure anal-
ogous to that for 7. An identical work-up gave 10 as a light
brown solid; yield: 0.5681 g (0.2919 mmol, 80%); mp 1108C
(capillary), 1108C (DSC, Te); TGA: onset ofa 92% mass
loss 209.88C; anal. calcd. for C40H16F68IP: C 24.68, H 0.83;
[Rf8
(CH2)2]
U
E
1
found: C 24.73, H, 0.80; H NMR (CF3C6F5 + CDCl3 capil-
lary): d=3.46 (m, 8H, CH2P), 2.86 (m, 8H, CF2CH2);
13C{1H} NMR (CF3C6F5 + CDCl3 capillary): d=24.2 (t,
2JCF =24 Hz, CF2CH2), 12.8 (d, 1JCP =52 Hz, CH2P);
31P NMR (CF3C6F5 + CDCl3 capillary): d=40.4 (s); MS
(positive FAB, 3-NBA): m/z=1818 ([MÀHÀI]+, 100%).
A
4 mL vial was charged with Rf6
(CH2)2I (0.4247 g,
0.8959 mmol), (0.3500 g, 0.2986 mmol), and DMF
5
(1.5 mL), and tightly sealed. The sample was vigorously stir-
red at 1158C for 48 h and cooled. The upper colorless DMF
layer was separated from the lower dark brown fluorous
layer. The latter was dried under oil pump vacuum and tri-
turated with Et2O. The Et2O was decanted and the residue
dried by oil pump vacuum to give 7 as a yellow solid; yield:
0.2947 g (0.1791 mmol, 60%); mp 508C (capillary), 438C
(DSC, Te); TGA: onset ofa 93% mass loss 196.5 8C; anal.
calcd. for C34H16F56IP: C 24.81, H 0.98; found: C 24.91, H
1.11; 1H NMR (CF3C6F5 + CDCl3 capillary): d=3.45 (m,
A
N
DMF (1.5 mL), Rf8(CH2)2Br (0.2776 g, 0.5268 mmol), and 6
E
(0.1807 g, 0.1317 mmol) were combined in a procedure anal-
ogous to that for 7. An identical work-up gave 11 as a beige
1632
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ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2006, 348, 1625 – 1634

Fluorous Quaternary Phosphonium Salts that Bear Four Ponytails
FULL PAPERS
solid; yield: 0.1981 g (0.1043 mmol, 79%); mp 918C (capil-
lary), 918C (DSC, Te); TGA: onset ofa 91% mass loss
209.58C; anal. calcd. for C40H16BrF68P: C 25.30, H 0.85;
from each phase (2 mL). The solvent was removed and the
residue dried under oil pump vacuum (0.01 mm Hg) and
then weighed.
1
found: C 25.29, H 0.89; H NMR (CF3C6F5 + CDCl3 capil-
lary): d=3.54 (m, 8H, CH2P), 2.94 (m, 8H, CF2CH2);
13C{1H} NMR (CF3C6F5 + CDCl3 capillary): d=24.1 (t,
2JCF =23 Hz, CF2CH2), 12.5 (d, 1JCP =51 Hz, CH2P);
31P NMR (CF3C6F5 + CDCl3 capillary): d=40.3 (s); MS
(positive FAB, 3-NBA): m/z=1819 ([MÀBr]+, 100%).
Potassium Picrate Extractions (Table 3)
Equal volumes ofa CF 3C6H5 or CF3C6F5 solution ofthe
phosphonium salt (10 mL, 0.1 mM; ifnecessary, the samples
were warmed to dissolve the salt) and aqueous potassium
picrate (0.1 mM) were introduced into a stoppered flask and
stirred for 0.5 h at 21Æ18C. The sample was allowed to
stand for 2 h at the same temperature to allow complete
phase separation. The absorbance ofthe picrate in the aque-
ous phase was measured at 356 nm with a Shimadzu UV-
visible spectrophotometer. The percentage ofpicrate ex-
tracted into the non-aqueous phase was calculated by:
Rf8
(CH2)2Br[31]
A
A flask was charged with Rf8(CH2)2OH (4.01 g, 8.61 mmol),
R
PPh3 (2.46 g, 9.41 mmol), and CH2Cl2 (30 mL), and cooled
in an ice bath. A solution ofCBr (3.12 g, 9.41 mmol) in
4
CH2Cl2 (5 mL) was added with stirring. The mixture was al-
lowed to warm to room temperature. After 14 h, the solvent
was removed by rotary evaporation, and pentane (40 mL)
was added. The mixture was filtered (removing PPh3/OPPh3
and starting alcohol), and the filtrate was concentrated by
rotary evaporation. Chromatography (short SiO2 column,
% Extraction=100 (Absbefore À Absafter)/Absbefore
where Absbefore is the absorbance ofa similarly diluted
sample ofthe unextracted potassium picrate solution and
Absafter is the absorbance ofthe potassium picrate solution
after extraction. Three independent extractions were per-
formed for each combination of potassium picrate and iono-
phore, and the results were averaged.
hexanes) gave Rf8(CH2)2Br as a colorless oil; yield: 3.98 g
T
(7.55 mmol, 87%); anal. calcd for C10H4BrF17: C 22.79, H
1
0.77; found: C 22.86, H 0.94; H NMR (CDCl3): d=3.39 (t,
3JHH =8 Hz, 2H, CH2Br), 2.67–2.49 (m, 2H, CF2CH2);
2
13C{1H} (CDCl3): d=35.0 (t, JCF =22 Hz, CF2CH2), 20.1 (t,
3JCF =6 Hz, CH2Br).
Acknowledgements
Phase Transfer Catalysis[31]
We thank the Deutsche Forschungsgemeinschaft (DFG, GL
300/3–3; J. A. G.), the Humboldt Foundation (fellowship to
C. S. C.), the Royal Society (A. M. S.) and Avecia (K. M. W.)
for financial support.
A 4 mL vial was charged with Rf8
(CH2)3I (13;[32] 0.1274 g,
A
0.2167 mmol), 9 (0.0400 g, 0.0217 mmol), CF3C6F5 (0.5 mL)
and aqueous NaCl (0.5 mL, 5M, 2.5 mmol), tightly sealed,
and vigorously stirred at 1008C. After 2 h, the mixture was
1
cooled. A H NMR spectrum ofan aliquot from the organic
phase (CDCl3) showed a ca. 50:50 ratio ofR f8(CH2)3Cl (14)
A
References
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The aqueous phase was similarly renewed and the sample
vigorously stirred at 1008C for 6 h and cooled (NMR,>
95:<5 14/13).
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1634
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Adv. Synth. Catal. 2006, 348, 1625 – 1634