HFPO trimer-based alkyl triflate, a novel building block for fluorous chemistry. Preparation, reactions and 19F gCOSY analysis

Article abstract of DOI:10.1135/cccc20081799

Triflate 4, CF₃(CF₂)₂O-CF(CF ₃)CF₂O-CF(CF₃)CH₂-OTf (R _FOCH₂OTf), of the HFPO trimer-based alcohol 3 (R _FOCH₂OH) is a novel highly fluorinated building block for fluorous chemistry. In analogy to similar polyfluorinated triflates with methylene spacer, its reactivity is limited to strong and soft nucleophiles. Whereas reactions with cyanide anion, phenolate anion, enolate of diethyl malonate or lithium salt of benzaldehyde bis(phenylsulfanyl)acetal were unsuccessful, the corresponding imidazole 5, iodide 6 or azide 7 were prepared in good yields. Reaction of imidazole 5 with (perfluorohexyl)methyl triflate (9) afforded highly fluorinated non-crystalline imidazolium salt 8, TfO ^-R_FOCH₂-(C₃H₃N ₂)⁺-CH₂C₆F₁₃-n, which could be employed as fluorous ionic liquid or intermediate for fluorous carbenes. Complete assignment of complex ¹⁹F NMR spectra of all compounds employed was accomplished using ¹⁹F gCOSY NMR method.

Full text of DOI:10.1135/cccc20081799

HFPO Trimer-Based Alkyl Triflate
1799
HFPO TRIMER-BASED ALKYL TRIFLATE, A NOVEL BUILDING BLOCK
FOR FLUOROUS CHEMISTRY. PREPARATION, REACTIONS AND
19F gCOSY ANALYSIS
a3
Ondřej KYSILKAa1, Markéta RYBÁČKOVÁa2, Martin SKALICKÝ
,
b
c
a4,
Magdalena KVÍČALOVÁ , Josef CVAČKA and Jaroslav KVÍČALA
*
a
Department of Organic Chemistry, Institute of Chemical Technology, Prague,
Technická 5, 166 28 Prague 6, Czech Republic; e-mail: kysilkao@vscht.cz,
1
2
3
4
rybackom@vscht.cz, skalicka@vscht.cz, kvicalaj@vscht.cz
b
Institute of Inorganic Chemistry, Academy of Sciences of the Czech Republic, v.v.i.,
Husinec-Řež 1001, 250 68 Řež, Czech Republic; e-mail: magda@iic.cas.cz
c Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i.,
Flemingovo nám. 2, 166 10 Prague 6, Czech Republic; e-mail: cvacka@uochb.cas.cz
Received July 15, 2008
Accepted August 11, 2008
Publish ed on lin e Decem ber 15, 2008
Dedicated to Professor Oldřich Paleta on the occasion of his 70th birthday.
Triflate 4, CF3(CF2)2O–CF(CF3)CF2O–CF(CF3)CH2–OTf (RFOCH2OTf), of th e HFPO trim er-
based alcoh ol 3 (RFOCH2OH) is a n ovel h igh ly fluorin ated buildin g block for fluorous ch em -
istry. In an alogy to sim ilar polyfluorin ated triflates with m eth ylen e spacer, its reactivity is
lim ited to stron g an d soft n ucleoph iles. Wh ereas reaction s with cyan ide an ion , ph en olate
an ion , en olate of dieth yl m alon ate or lith ium salt of ben zaldeh yde bis(ph en ylsulfan yl)acetal
were un successful, th e correspon din g im idazole 5, iodide 6 or azide 7 were prepared in good
yields. Reaction of im idazole 5 with (perfluoroh exyl)m eth yl triflate (9) afforded h igh ly fluo-
rin ated n on -crystallin e im idazolium salt 8, TfO–RFOCH2–(C3H3N2)+–CH2C6F13-n, wh ich could
be em ployed as fluorous ion ic liquid or in term ediate for fluorous carben es. Com plete as-
sign m en t of com plex 19F NMR spectra of all com poun ds em ployed was accom plish ed usin g
19F gCOSY NMR m eth od.
Keyw ord s: Fluorous ligan ds; Polyeth ers; Polyfluorin ated com poun ds; HFPO trim er; Triflates;
Buildin g blocks; 19F COSY spectroscopy; Im idazolium salts.
Oligom ers an d telom ers of h exafluoropropen e-1,2-oxide (HFPO) are h igh ly
useful in term ediates for in dustrial ch em istry of polym ers an d in ert liquids1.
Among them, HFPO trimer 1, CF3(CF2)2O–CF(CF3)CF2O–CF(CF3)COF (RFOCOF)
is probably th e best com prom ise between th e feasibility of preparation in
a pure form an d sufficien t fluoroph ilicity. Its m ost useful tran sform ation is
Collect. Czech. Chem. Commun. 2008, Vol. 73, No. 12, pp. 1799–1813
© 2008 Institute of Organic Chemistry and Biochemistry
doi:10.1135/cccc20081799

1800
Kysilka et al.:
decarboxylation leadin g to trifluorovin yl eth er2, th e in dustrial m on om er.
Furth erm ore, th e term in al acyl fluoride group can be easily tran sform ed to
th e correspon din g esters. However, th ey are m uch less stable th an esters of
n on -fluorin ated carboxylic acids3 an d th is severely lim its th e scope of th eir
application s in ch em istry.
Polyfluorin ated alcoh ols with n on -fluorin ated spacer of various len gth s
offer h igh variability in fun ction alization . Hen ce, several laboratories in -
depen den tly reported th e reduction of HFPO trim er 1 or th e ester 2 pre-
4
pared from it to th e correspon din g alcoh ol 3 . Its furth er reaction s in clude
th e tran sform ation to polym erizable m eth acrylates4a, addition to fluoro-
alken es4b, or eth erification 4c
.
Am on g oth er possible tran sform ation s of polyfluorin ated alcoh ols,
acylation to th e esters of sulfon ic acids belon gs to on e of th e m ost gen eral
approach es to polyfluoroalkylation reaction s. Th us, polyfluorin ated alco-
h ols with a n on -fluorin ated th ree carbon ch ain h ave been tran sform ed to
th e correspon din g tosylates an d used for th e preparation of polyfluorin ated
am in es5. We successfully em ployed triflate of polyfluorin ated alcoh ol with
a two carbon n on -fluorin ated spacer for th e preparation of bis(polyfluoro-
alkylated) cyclopen tadien es6 an d acetylen es7, wh ile th e correspon din g io-
dides were n ot sufficien tly reactive. Fluoroalcoh ols with a on e-carbon (i.e.
m eth ylen e) spacer are rath er acidic an d h en ce th ey h ave to be tran sform ed
to th e correspon din g triflates to allow n ucleoph ilic substitution 8. Th ese
triflates react with alkoxides to form eth ers8a,8b, with in organ ic iodides to
th e correspon din g iodides8c, or with tertiary am in es to polyfluorin ated
am m on ium salts8d. In th e case of th e reaction with alkoxides, un expected
attack on th e sulfur atom of th e triflic m oiety was observed in som e cases8e.
In th e search for n ovel fluorous ion ic liquids we decided to syn th esize
triflate of th e alcoh ol derived from th e HFPO trim er an d to perform a sh ort
study regardin g th e scope an d lim itation s of its reactivity.
HFPO trim er con tain s two stereogen ic cen tres an d, con sequen tly, con sists
of equim olar m ixture of diastereom ers. Th is, togeth er with th e presen ce of
4
two CF2 groups bearin g two an isoch ron ic fluorin e atom s an d large JF-F cou-
plin g con stan t values, results in h igh ly com plex 19F NMR spectra wh ich
were n ot yet fully resolved. Sim ilarly in com plete is th e an alysis of HFPO
derivatives. Recen tly, advan ces in NMR in strum en tation m ade 19F COSY
4
feasible, wh ich was used for con firm ation of th e well kn own fact th at JF-F
3
couplin g con stan ts are gen erally larger th an th e JF-F on es9. We h en ce de-
cided to em ploy 19F gCOSY NMR for th e full assign m en t of th e NMR sign als
of th e com poun ds syn th esized in cludin g separate diastereom er description
wh erever possible.
Collect. Czech. Chem. Commun. 2008, Vol. 73, No. 12, pp. 1799–1813

HFPO Trimer-Based Alkyl Triflate
1801
EXPERIMENTAL
Tem perature data were un corrected. NMR spectra were recorded with a Varian MercuryPlus
spectrom eter, 1H NMR spectra at 299.97 MHz an d 13C NMR spectra at 75.43 MHz usin g re-
sidual deuterated solven t sign als as th e in tern al stan dards, 19F NMR spectra at 282.22 MHz
usin g CCl3F as th e in tern al stan dard. Ch em ical sh ifts (δ) are given in ppm , couplin g con -
stan ts(J) in Hz. Diastereom ers are distin guish ed with upper case letters (A, B), an isoch ron ic
sign als (stron gly coupled AB system s) of n on -equivalen t fluorin e atom s in CF2 groups are
m arked with lower case letters (a, b). In som e cases, 19F gCOSY experim en ts were perform ed
to allow full assign m en t of sign als. FTIR spectra were determ in ed on an FTIR Nicolet 6700
in strum en t in NaCl tablets. Mass spectra (ESI, APCI) were m easured with a LCQ Fleet
(Fin n igan ) in strum en t, HRMS spectra (ESI, APCI, FAB) with a LTQ Orbitrap XL (Th erm o
Fish er Scien tific) or ZAB-EQ (VG An alytical) in strum en ts.
All reaction s were perform ed in dry in ert atm osph ere in an oven -dried apparatuses. Per-
fluoro(2,5-dim eth yl-3,6-dioxan on an oyl) fluoride (HFPO trim er 1, CF3(CF2)2O–CF(CF3)CF2O–
CF(CF3)COF), 2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroh eptan -1-ol (1H,1H-perfluoroh eptan -1-ol,
n-C6F13CH2OH) an d trifluorom eth an esulfon ic an h ydride (triflic an h ydride) were purch ased
from Apollo Scien tific, im idazole from Fluka. Aceton e an d aceton itrile were distilled over
P2O5, dich lorom eth an e an d DMF over CaH2, an d toluen e over Na. 1,2-Dibrom o-1,1,2,2-tetra-
fluoroeth an e (BrCF2CF2Br) was distilled an d dried over m olecular sieves. 2,4,4,5,7,7,8,8,9,9,9-
Un decafluoro-2,5-bis(trifluorom eth yl)-3,6-dioxan on an -1-ol (3, CF3(CF2)2O–CF(CF3)CF2O–
CF(CF3)CH2OH) was prepared from HFPO trim er 1 via th e correspon din g m eth yl ester 2
accordin g to ref.4a, 2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroh eptyl trifluorom eth an esulfon ate (9,
n-C6F13CH2–OTf) from th e correspon din g fluoroalcoh ol an d trifluorom eth an esulfon ic an -
h ydride accordin g to ref.8a
Perfluoro(2,5-dim eth yl-3,6-dioxan on an oyl) Fluoride (HFPO Trim er 1)4a
19F NMR (282 MHz, THF-d8): 26.6 s, 1 F (F1A or F1B); 26.7 s, 1 F (F1A or F1B); –78.8 dm ,
2
2
1 F, JF-F = 145 (F4aA); –79.4 dm , 1 F, JF-F = 145 (F4aB); –80.7 m , 2 × 3 F (F6A an d F6B);
2
2
–81.8 dm , 2 × 1 F, JF-F = 145 (F7aA an d F7aB); –82.2 dm , 2 × 1 F, JF-F = 145 (F7bA an d
F7bB); –82.2 t, 3 F, JF-F = 7 (F9A or F9B); –82.3 t, 3 F, JF-F = 7 (F9A or F9B); –82.8 m , 2 ×
3 F (F3A an d F3B); –85.5 dm , 1 F, JF-F = 145 (F4bB); –86.1 dm , 1 F, JF-F = 145 (F4bA);
–130.2 s, 2 × 2 F (F8A an d F8B); –131.2 dm , 1 F, JF-F = 21 (F2B); –131.3 dm , 1 F, JF-F = 21
4
4
2
2
4
4
4
(F2A); –145.4 t, 2 × 1 F, JF-F = 22 (F5A an d F5B).
Collect. Czech. Chem. Commun. 2008, Vol. 73, No. 12, pp. 1799–1813

1802
Kysilka et al.:
Meth yl Perfluoro(2,5-dim eth yl-3,6-dioxan on an oate) (2)4a
1H NMR (300 MHz, aceton e-d6): 4.13 s, 3 H (CH3). 19F NMR (282 MHz, aceton e-d6):
2
2
–78.6 dm , 1 F, JF-F = 145 (F3aA); –79.2 dm , 1 F, JF-F = 145 (F3aB); –79.8 m , 2 × 3 F (F5A
2
4
an d F5B); –80.9 dm , 2 × 1 F, JF-F = 145 (F6aA an d F6aB); –81.1 t, 3 F, JF-F = 7 (F8A or F8B);
–81.2 t, 3 F, JF-F = 7 (F8A or F8B); –81.3 dm , 2 × 1 F, JF-F = 145 (F6bA an d F6bB); –82.2 m ,
4
2
2
3 F (F2A or F2B); –82.2 m , 3 F (F2A or F2B); –84.4 dm , 1 F, JF-F = 145 (F3bB); –85.0 dm , 1 F,
2JF-F = 145 (F3bA); –129.3 s, 2 F (F7A or F7B); –129.3 s, 2 F (F7A or F7B); –131.1 dm , 1 F,
4JF-F = 23 (F1B); –131.1 dm , 1 F, JF-F = 23 (F1A); –144.8 t, 1 F, JF-F = 23 (F4B); –144.9 t, 1 F,
4
4
4JF-F = 23 (F4A).
2,4,4,5,7,7,8,8,9,9,9-Un decafluoro-2,5-bis(trifluorom eth yl)-3,6-dioxan on an -1-ol (3)4a
1H NMR (300 MHz, aceton e-d6): 4.26 m , 2 H (CH2); 5.36 bs, 1 H (OH). 19F NMR (282 MHz,
2
2
aceton e-d6): –78.6 dm , 1 F, JF-F = 145 (F3aA); –78.7 dm , 1 F, JF-F = 145 (F3aB); –79.9 m , 2 ×
2
2
3 F (F5A an d F5B); –80.8 dm , 2 × 1 F, JF-F = 145 (F6aA an d F6aB); –81.1 dm , 1 F, JF-F = 145
(F3bB); –81.2 t, 3 F, JF-F = 7 (F8A or F8B); –81.2 t, 3 F, JF-F = 7 (F8A or F8B); –81.3 dm , 1 F,
2JF-F = 145 (F3bA); –81.4 dm , 2 × 1 F, JF-F = 145 (F6bA an d F6bB); –82.0 m , 3 F (F2A or
4
4
2
F2B); –82.1 m , 3 F (F2A or F2B); –129.4 s, 2 F (F7A or F7B); –129.4 s, 2 F (F7A or F7B);
4
4
4
4
–134.4 dq, 1 F, JF-F = 24 (d), JF-F
=
4
3JH-F = 12 (q) (F1B); –134.6 dq, 1 F, JF-F = 24 (d), JF-F
=
3JH-F = 12 (q) (F1A); 144.8 t, 1 F, JF-F = 21 (F4B); –144.9 t, 1 F, JF-F = 21 (F4A).
4
2,4,4,5,7,7,8,8,9,9,9-Un decafluoro-2,5-bis(trifluorom eth yl)-3,6-dioxan on yl
Trifluorom eth an esulfon ate (4)
To an ice-cooled solution of fluoroalcoh ol 3 (15.26 g, 31.66 m m ol) an d pyridin e (3.70 m l,
45.9 m m ol) in absolute CH2Cl2 (50 m l), trifluorom eth an esulfon ic an h ydride (7.63 m l,
45.4 m m ol) was added dropwise wh ile stirrin g vigorously. Th e m ixture was stirred at 0 °C
Collect. Czech. Chem. Commun. 2008, Vol. 73, No. 12, pp. 1799–1813

HFPO Trimer-Based Alkyl Triflate
1803
for 2 h an d th en at room tem perature overn igh t. Solid pyridin ium trifluorom eth an e-
sulfon ate was filtered off an d th e m ixture was wash ed with cold water (3 × 40 m l). Th e or-
gan ic ph ase was dried with an h ydrous MgSO4 an d th e solven t was evaporated to give
a yellow oil, wh ich on fraction ation yielded 13.66 g (70.2%) of fluorotriflate 4 (colorless
liquid, b.p. 80–82 °C/2.5 kPa). 1H NMR (300 MHz, aceton e-d6): 5.57 m , 2 H (CH2). 19F NMR
2
(282 MHz, aceton e-d6): –74.5 s, 3 F (F1); 79.3 dm , 1 F, JF-F = 145 (F4aA); –79.5 dm , 1 F,
2
2JF-F = 145 (F4aB); –79.7 m , 2 × 3 F (F6A an d F6B); –80.5 dm , 1 F, JF-F = 145 (F4bB);
2
2
–80.7 dm , 2 × 1 F, JF-F = 145 (F7aA an d F7aB); –80.8 dm , 1 F, JF-F = 145 (F4bA); –81.2 t,
4
4
2
3 F, JF-F = 7 (F9A or F9B); –81.2 t, 3 F, JF-F = 7 (F9A or F9B); –81.4 dm , 2 × 1 F, JF-F = 145
5
5
(F7bA an d F7bB); –81.8 d, 3 F, JF-F = 6 (F3A or F3B); –81.9 d, 3 F, JF-4F = 6 (F3A or F3B);
4
–129.3 s, 2 F (F8A or F8B); –129.3 s, 2 F (F8A or F8B); –135.5 dq, 1 F, JF-F = 23 (_), JF-F
=
3JH-F = 12 (q) (F2B); –135.6 dq, 1 F, JF-F = 23 (_), JF-F
=
3JH-F = 12 (q) (F2A); –144.4 t, 1 F,
4
4
4JF-F = 21 (F5B); –144.6 t, 1 F, JF-F = 21 (F5A). 13C NMR (75 MHz, aceton e-d6): 69.0 d, 1 C,
4
2JC-F = 30 (CH2); 100–126 m , 8C (CF, CF2 an d CF3 groups); 118.6 q, 1 C, JC-F = 318
1
(CF3SO2O). MS (ESI), m/z (%): 545 [M – CF3]+, 55; 351 [M – CF(CF3)CH2OSO2CF3]+, 50; 285
[M – CF2OCF(CF3)CH2OSO2CF3]+, 100. HRMS (FAB), m/z: calculated for C10H2F20NaO5S [M +
Na]+ 636.91958, foun d 636.91882. IR: 1437 m , 1234 s, 1202 s, 1144 s, 609 m (C–S).
1-[2,4,4,5,7,7,8,8,9,9,9-Un decafluoro-2,5-bis(trifluorom eth yl)-3,6-dioxan on yl]im idazole (5)
A flask was charged with im idazole (1.50 g, 23.5 m m ol), fluoroalkyl triflate 4 (6.70 g, 10.9 m m ol)
an d aceton itrile (40 m l). Th e m ixture was refluxed for 8 h an d th en stirred at room tem pera-
ture overn igh t. Aceton itrile was evaporated, th e residue was dissolved in dieth yl eth er (100 m l)
an d wash ed with cold water (3 × 50 m l). Th e organ ic layer was dried with an h ydrous MgSO4
an d th e solven t was evaporated givin g a brown oil. To rem ove traces of colored im purities,
th e crude product was dissolved in dieth yl eth er an d stirred with ch arcoal overn igh t. Filtra-
tion an d evaporation gave fluorin ated im idazole 5 (5.80 g, 31.8%, colorless viscous oil).
1H NMR (300 MHz, aceton e-d6): 5.21 m , 2 H (H4); 7.00 m , 1 H (H2); 7.21 m , 1 H (H3);
2
7.68 s, 1 H (H1). 19F NMR (282 MHz, aceton e-d6): –77.9 dm , 1 F, JF-F = 145 (F3aA); –78.2 dm ,
2
2
1 F, JF-F = 145 (F3aB); –79.5 m , 2 × 3 F (F5A an d F5B); –80.4 dm , 1 F, JF-F = 145 (F6aA an d
2
4
F6aB); –80.6 dm , 1 F, JF-F = 145 (F3bB); –81.0 t, 3 F, JF-F = 6 (F8A or F8B); –81.0 t, 3 F,
4JF-F = 6 (F8A or F8B); –81.0 dm , 1 F, JF-F = 145 (F3bA); –81.3 dm , 2 × 1 F, JF-F = 145 (F6bA
an d F6bB); –81.6 d, 3 F, JF-F = 12 (F2A or F2B); –81.8 d, 3 F, JF-F = 12 (F2A or F2B);
2
2
5
5
4
4
–129.1 s, 2 F (F7A or F7B); –129.2 s, 2 F (F7A or F7B); –134.7 dq, 1 F, JF-F = 20 (d), JF-F
=
3JH-F = 12 (q) (F1B); –134.8 dq, 1 F, JF-F = 20 (d), JF-F
=
3JH-F = 12 (q) (F1A); –144.2 t, 1 F,
4
4
4JF-F = 20 (F4B); –144.6 dt, 1 F, JF-F = 20 (t), JF-F = 9 (d) (F4A). 13C NMR (75 MHz, ace-
4
3
ton e-d6): 47.1 d, 1 C, JC-F = 21 (CH42); 100–126 m , 8 C (CF, CF2 an d CF3 groups); 121.3 s,
2
1 C (CH2); 128.2 s, 1 C (CH3); 138.8 s, 1 C (CH1). MS (ESI), m/z (%): 533 [M + H]+, 100.
HRMS (ESI), m/z: calculated for C12H6F17N2O2 [M + H]+ 533.01523, foun d 533.01497.
IR: 3124 w, 3005 w, 2968 w, 1695 w (C=N); 1507 w (C=C); 1239 s, 1198 s, 1157 s.
Collect. Czech. Chem. Commun. 2008, Vol. 73, No. 12, pp. 1799–1813

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Kysilka et al.:
1,1,1,2,4,4,5,7,7,8,8,9,9,9-Tetradecafluoro-2-(iodom eth yl)-
5-(trifluorom eth yl)-3,6-dioxan on an e (6)
A flask was ch arged with aceton e (20 m l), an h ydrous NaI (12.42 g, 82.86 m m ol) an d triflate
4 (3.32 g, 5.40 m m ol). Th e m ixture was refluxed for 1 h an d th en stirred at room tem pera-
ture overn igh t. Th e solven t was evaporated, th e residue was dissolved in dieth yl eth er (50 m l)
an d rapidly wash ed with cold water (50 m l). Th e organ ic ph ase was dried with an h ydrous
Na2SO4 an d th e solven t was evaporated to afford a yellow oil. Distillation gave iodide 6
(2.43 g, 76.0%, b.p. 80–82 °C/2.5 kPa, colorless h igh ly volatile oil). 1H NMR (300 MHz,
2
aceton e-d6): 4.05 m , 2 H (CH2). 19F NMR (282 MHz, aceton e-d6): –77.5 dm , 1 F, JF-F = 145
2
(F3aA); –78.0 dm , 1 F, JF-F = 145 (F3aB); –79.4 m , 3 F (F5A or F5B); –79.5 m , 3 F (F5A or
2
2
F5B); –80.4 dm , 2 × 1 F, JF-F = 140 (F6aA an d F6aB); –80.6 dm , 1 F, JF-F = 145 (F3bB);
2
–80.9 dm , 1 F, JF-F = 145 (F3bA); –81.0 m , 6 F (F2A, F2B, F8A an d F8B); –81.3 dm , 2 × 1 F,
2JF-F = 145 (F6b A an d F6b B); –122.5 dq, 1 F, JF-F
=
3JH-F = 21 (q), JF-F = 9 (d) (F1B);
4
4
4
4
–122.9 dq, 1 F, JF-F
=
3JH-F = 21 (q), JF-F = 9 (d) (F1A); –129.1 s, 2 F (F7A or F7B); –129.3 s,
2 F (F7A or F7B); –144.4 tm , 1 F, JF-F = 20 (F4B); –144.7 tm , 1 F, JF-F = 20 (F4A). 13C NMR
4
4
2
(75 MHz, aceton e-d6): 69.2 d, 1 C, JC-F = 30 (CH2); 100–126 m , 8 C (CF, CF2 an d CF3
groups). HRMS (EI), m/z: calculated for C9H2F17IO2 [M]+ 591.88280, foun d 591.88187.
IR: 1306 m , 1239 s, 1202 s, 1157 s.
2,4,4,5,7,7,8,8,9,9,9-Un decafluoro-2,5-bis(trifluorom eth yl)-3,6-dioxan on ylazide (7)
A flask was filled with fluoroalkyl triflate 4 (0.45 g, 0.74 m m ol), NaN3 (0.12 g, 1.85 m m ol)
an d DMF (6 m l). Th e obtain ed two-ph ase (fluorous an d DMF) m ixture was h eated wh ile stir-
rin g to 50 °C for two days. DMF was rem oved by extraction of th e reaction m ixture with
water. Organ ic ph ase was diluted with dieth yl eth er (50 m l), wash ed again with water (3 ×
40 m l), dried with an h ydrous Na2SO4 an d th e solven t was evaporated to give th e target
azide 7 (0.189 g, 50.5%, colorless oil). 1H NMR (300 MHz, aceton e-d6): 4.41 m , 2 H (CH2).
2
2
19F NMR (282 MHz, aceton e-d6): –79.8 dm , 1 F, JF-F = 145 (F3aA); –80.0 dm , 1 F, JF-F = 145
2
(F3aB); –80.5 m , 2 × 3 F (F5A an d F5B); –81.5 dm , 1 F, JF-F = 145 (F3bB); –81.6 dm , 2 × 1 F,
2JF-F = 145 (F6aA an d F6aB); –81.9 dm , 1 F, JF-F = 145 (F3bA); –82.0 m , 2 × 3 F (F8A an d
F8B); –82.3 dm , 2 × 1 F, JF-F = 145 (F6bA an d F6bB); –83.0 d, 1 F, JF-F = 6 (F2A or F2B);
2
2
5
5
–83.1 d, 1 F, JF-F = 6 (F2A or F2B); –130.2 s, 2 F (F7A or F7B); –130.3 s, 2 F (F7A or F7B);
4
4
4
4
–133.2 dq, 1 F, JF-F = 23 (d), JF-F
= =
3JH-F = 13 (q) (F1B); –133.3 dq, 1 F, JF-F = 23 (d), JF-F
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HFPO Trimer-Based Alkyl Triflate
1805
4
4
3JH-F = 13 (q) (F1A); –145.6 tm , 1 F, JF-F = 22 (F4B); –145.7 tm , 1 F, JF-F = 21 (F4A).
13C NMR (75 MHz, aceton e-d6): 80.8 d, 1 C, JC-F = 27 (CH2); 100–126 m , 8 C (CF, CF2 an d
2
CF3 groups). MS (APCI), m/z (%): 480 [M – N2 + H]+, 8; 479 [M – N2]+, 100. HRMS (EI), m/z:
calculated for C9H2F17N3O2 [M]+ 506.98755, foun d 506.98842. IR: 2117 m (N=N); 1238 s,
1201 s, 1159 m .
1-(2,2,3,3,4,4,5,5,6,6,7,7,7-Tridecafluoroh eptyl)-3-[2,4,4,5,7,7,8,8,9,9,9-un decafluoro-
2,5-bis(trifluorom eth yl)-3,6-dioxan on yl]im idazolium Trifluorom eth an esulfon ate (8)
A flask was ch arged with fluoralkylated im idazole 5 (3.99 g, 7.49 m m ol), fluoroalkyl triflate
9 (3.61 g, 7.49 m m ol) an d 10 m l of toluen e. Th e reaction m ixture was h eated to 120 °C for
8 days wh ile stirrin g. From th e resultin g two-ph ase m ixture, toluen e was evaporated an d th e
residual solven ts were rem oved by h eatin g to 100 °C/1 Pa for two days, givin g th e target
fluorous im idazolium triflate 8 (6.71 g, 88.2%, h igh ly viscous yellow oil). 1H NMR (300 MHz,
3
aceton e-d6): 5.76 t, JH-F = 16.4, 2 H (H5); 5.81 m , 2 H (H4); 8.21 m , 1 H (H2); 8.26 m , 1 H
2
(H3); 9.84 s, 1 H (H1). 19F NMR (282 MHz, aceton e-d6): –77.8 dm , 1 F, JF-F = 150 (F3aA);
2
4
–78.0 dm , 1 F, JF-F = 150 (F3aB); –78.2 s, 2 × 3 F (F15A an d F15B); –79.5 q, 3 F, JF-F
=
=
5JF-F = 9 (F5A or F5B); –79.6 q, 3 F, JF-F
140 (F6aA an d F6aB); –80.6 m , 2 × 3 F (F14A an d F14B); –81.0 t, 3 F, JF-F = 7 (F8A or F8B);
–81.1 dm , 1 F, JF-F = 150 (F3bB); –81.1 t, 3 F, JF-F = 7 (F8A or F8B); –81.3 d, 1 F, JF-F = 11
(F2A or F2B); –81.3 dm , 1 F, JF-F = 150 (F3bA); –81.4 dm , 2 × 1 F, JF-F = 140 (F6bA an d
=
5JF-F = 9 (F5A or F5B); –80.4 dm , 2 × 1 F, JF-F
4
2
4
2
4
5
2
2
5
F6bB); –81.5 d, 1 F, JF-F = 11 (F2A or F2B); –116.8 m , 2 × 2 F (F9A an d F9B); –121.5 m , 2 ×
2 F (F11A an d F11B); –122.2 m , 2 × 2 F (F10A an d F10B); –122.2 m , 2 × 2 F (F12A an d
F12B); –125.7 m , 2 × 2 F (F13A an d F13B); –129.1 s, 2 F (F7A or F7B); –129.3 s, 2 F (F7A or
4
4
F7B); –134.6 dq, 1 F, JF-F
=
3JH-F = 22 (q), JF-F = 15 (d) (F1B); –135.2 dq, 1 F ,4JF-F
=
3JH-F
=
22 (q), JF-F = 15 (d) (F1A); –144.0 tm , 2 × 1 F, JF-F = 21 (F4A an d F4B). 13C NMR (75 MHz,
4
4
aceton e-d6): 48.8 t, 1 C, JC-F = 23 (CH52); 49.6 d, 1 C, JC-F = 20 (CH42); 100–126 m , 14 C
2
2
(CF, CF2 an d CF3 groups); 120.5 q, 1 C, JC-F = 317 (CF153); 125.7 s, 1 C (CH2); 125.8 s, 1 C
1
(CH3); 141.0 s, 1 C (CH1). MS (ESI), m/z (%): 865 [M – TfO–]+, 100; 149 [TfO]–, 100.
RESULTS AND DISCUSSION
Preparation of HFPO Trimer-Based Triflate 4
Esterification of HFPO trim er 1 (RFOCOF, 78% yield) followed by reduction
of th e ester 2 (RFOCOOMe, 75% yield) afforded polyfluorin ated alcoh ol 3
(RFOCH2OH) accordin g to th e publish ed data4a.
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1806
Kysilka et al.:
Syn th esis of th e correspon din g triflate 4 was accom plish ed accordin g to
th e m eth odology em ployed for th e preparation of triflates of fluorin ated
alcoh ols with m eth ylen e spacer8a, i.e. by slowly addin g triflic an h ydride to
th e ice-cooled solution of fluoro alcoh ol 3 an d pyridin e in an h ydrous di-
ch lorom eth an e. Purification of th e m ixture after stan dard aqueous work-up
by fraction al vacuum distillation afforded th e target fluoroalkyl triflate as
a colorless, sligh tly viscous liquid in 70% yield (Sch em e 1). Th e triflate is re-
m arkably stable an d does n ot decom pose on stan din g in water.
SCHEME 1
Reactions of HFPO Trimer-Based Triflate 4
Th e reactivity of polyfluoroalkylated triflates strikin gly depen ds on th e
len gth of th e n on -fluorin ated spacer between th e perfluoroalkyl group an d
th e triflate un it. Th us, trim eth ylen e spacer leads to reactan t with stan dard
triflate reactivity an d eth ylen e spacer lim its th e reactivity of th e correspon d-
in g triflate on ly to a m in or exten t, allowin g th us fun ction alization with
m ost n ucleoph ilic reagen ts6a. In con trast to th is, polyfluoroalkylated
triflates with m eth ylen e spacer exh ibit h igh ly lim ited reactivity8. Moreover,
th e substitution on th e carbon atom can be accom pan ied by th e attack of
th e n ucleoph ile on th e sulfur atom of th e triflate m oiety8e. To obtain th e
in form ation h ow bran ch in g at th e β-carbon an d th e ch an ge of th e per-
fluoroalkyl ch ain for th e perfluoropolyeth er on e will in fluen ce th e beh av-
iour of th e triflate, we perform ed a series of reaction s of triflate 4 with
various n ucleoph ilic reagen ts.
We in deed foun d th at th e reactivity is lower com pared to oth er triflates
an d lim ited to th e m ost reactive n ucleoph iles. Th us, n o reaction of triflate
4 was observed with KCN in MeCN at 70 °C or with sodium en olate of di-
eth yl m alon ate in THF at 80 °C. Perform in g th e reaction of KCN in DMF or
DMPU at 120 °C lead to th e form ation of a com plex m ixture of products,
in wh ich in dividual com pon en ts could n ot be iden tified. Sim ilar n egative
results afforded th e reaction of triflate 4 with lith ium salt of ben zaldeh yde
Collect. Czech. Chem. Commun. 2008, Vol. 73, No. 12, pp. 1799–1813

HFPO Trimer-Based Alkyl Triflate
1807
bis(ph en ylsulfan yl)acetal. Reaction of triflate 4 with sodium ph en olate in
an alogy to ref.8a afforded on ly polyfluorin ated alcoh ol 3, probably as a re-
sult of th ioph ilic attack of th e ph en oxide8e.
On th e oth er h an d, reaction of triflate 4 with im idazole, a good n ucleo-
ph ile, in refluxin g aceton itrile afforded th e correspon din g fluoroalkylated
im idazole 5 in a m oderate yield, wh ere part of th e product was lost in
th e course of purification procedure. Fin kelstein reaction of triflate 4 with
sodium iodide in aceton e led to a good yield of fluorin ated iodide 6 as
th e perspective in term ediate for radical reaction s. Fin ally, substitution of
triflate 4 with an oth er excellen t n ucleoph ile, sodium azide, in DMF at 50 °C
yielded azide 7 as th e precursor of th e correspon din g fluorin ated am in es
(Sch em e 2).
SCHEME 2
Preparation of Fluorous Imidazolium Salt 8
Appropriately 1,3-disubstituted im idazolium salts belon g to th e m ost com -
m on ion ic liquids used. Several types of fluorous ion ic liquids h as been
syn th esized11a, based on fluorin ated h eterocyclic cation s11b, am m on ium
salts11c or fluorin ated an ion s11c–11g. Mon o(polyfluoroalkylated) im idazol-
ium salts are kn own an d h ave been studied as solven ts for m etal ion extrac-
tion 12a, solven ts for CO2 12b,12c, surfactan ts12d, or solven ts for Diels–Alder
Collect. Czech. Chem. Commun. 2008, Vol. 73, No. 12, pp. 1799–1813

1808
Kysilka et al.:
reaction s12e. Th ese ion ic liquids are in gen eral in sufficien tly fluorin ated to
exert ch aracteristic fluorous properties such as n egligible m iscibility with
organ ic solven ts. Bis(polyfluoroalkylated) im idazolium salts h ave been also
prepared, but th ey are crystallin e solids an d h en ce can n ot be em ployed as
room -tem perature ion ic liquids (RTILs)13. In con trast to lon g-ch ain per-
fluoroalkylated com poun ds wh ich are in gen eral crystallin e, perfluorin ated
polyeth ers based on HFPO oligom ers or telom ers are liquids. Th is led us to
th e assum ption th at im idazolium salts bearin g triflate 4 derived ch ain
sh ould n ot be crystallin e. Th is was con firm ed wh en we reacted fluoro-
im idazole 5 with (perfluoroalkyl)m eth yl triflate 9 an d in deed obtain ed
un sym m etrically polyfluoroalkylated im idazolium salt 8 as h igh ly viscous
liquid, th e first kn own exam ple of h igh ly fluorous im dazole-based RTIL
(Sch em e 3).
SCHEME 3
Analysis of HFPO Trimer-Derived Compounds with 19F gCOSY NMR
In HFPO trim er or its derivatives, th e CF2 group of th e perfluoropropoxy
fragm en t an d CF groups h ave ch aracteristic easily distin guish able sign als
(Fig. 1).
On th e oth er h an d, rem ain in g sign als, i.e. CF3 an d CF2O groups, overlap
in th e region from –75 to –85 ppm , m akin g especially th e assign m en t of
h igh ly coupled an isoch ron ic CF2O groups in 1D 19F NMR spectra im pos-
sible. Hen ce, all previously attem pted assign m en ts are eith er gen eral an d
in com plete, or erron eous an d gen erally om it th e fact th at th e com poun ds
con sist of th e m ixtures of two diastereom ers. Th is can be well docum en ted
on th e publish ed NMR assigm en ts4 of fluoroalcoh ol 3. We th erefore per-
form ed a series of 19F gCOSY experim en ts, wh ich allowed n early com plete
assign m en t of all fluorin e sign als in HFPO trim er-derived com poun ds we
worked with , viz. acyl fluoride 1, ester 2, alcoh ol 3, triflate 4, im idazole 5,
iodide 6, azide 7 an d im idazolium salt 8. As th e in dividual sign al pattern s
are sim ilar for all com poun ds, th e assign m en t will be sh owed in detail on ly
for th e m ost com plex case, im idazolium salt 8.
Collect. Czech. Chem. Commun. 2008, Vol. 73, No. 12, pp. 1799–1813

HFPO Trimer-Based Alkyl Triflate
1809
We started th e assign m en t with th e description of th e perfluoroh exyl
fragm en t of th e (perfluoroh exyl)m eth yl group. Apart of CF3 group sign al,
all rem ain in g CF2 groups display sign als in a n arrow area between –115 an d
–130 ppm an d are well resolved with th e exception of two overlappin g sig-
n als at –122.2 ppm . It is well kn own an d docum en ted th at in perfluor-
4
in ated com poun ds th e JF-F couplin g con stan t (~10 Hz) is ch aracteristically
3
larger th an th e JF-F on e (<3 Hz)9. In an alogy to ref.9, two sets of in teraction s
can be h en ce distin guish ed, th e first am on g th e even an d th e secon d
am on g th e odd fluorin ated carbon atom s. Th e slice of gCOSY spectrum at
4
–122.2 ppm reveals th e JF-F couplin g with th e C14F3 group an d allows th us
to assign it un equivocally am on g oth er CF3 groups of th e perfluoro-
polyeth er ch ain . No oth er couplin g can be recogn ized at th is slice an d
h en ce th e sign al at –122.2 ppm of double in tegral in ten sity h as to be
assign ed to both C12F2 an d C10F2 groups. Correspon din gly, th e slice at
–121.5 ppm sh ows th e couplin g with sign als at –116.8 an d –125.7 ppm .
As th e m ost upfield CF2 group sign al at –125.7 is kn own to belon g to
CF3CF2 m oiety (i.e., to C13F2 group sign al), th e form er h as to be assign ed
to th e C9F2 group sign al (Fig. 2).
Th e assign m en t of sign als of th e perfluoropolyeth er m oiety started from
easily assesible upfield sign als (see Fig. 1) of both CF groups an d CF2 group
of th e perfluoropropoxy un it, wh ich was already perform ed earlier on oth er
HFPO trim er derivatives4. Th us, th e triplet at –144.0 ppm was assign ed to
th e C4F group as th e sign al com m on for both diastereom ers. Closer in spec-
tion of gCOSY spectrum at th e area aroun d –135 ppm revealed th at two
sign als of C1F groups of th e two diastereoisom ers could be distin guish ed,
viz. at –134.6 or –135.2 ppm . A slice of gCOSY spectrum at about –129 ppm
did n ot sh ow an y couplin g of th e C7F2 group an d h en ce th e two sign als
at th is area can n ot be assign ed as doublet of on e CF2 group, but as two
sin glets of two diastereoisom ers (–129.1 or –129.3 ppm ).
Slices at sh ifts of both CF sign als, as well as th e slice at th e sh ift of th e
3
CF2 group of th e perfluoropropoxy group did n ot reveal an y JF-F couplin g
in excellen t agreem en t with observation m ade for perfluoroalkylated sys-
4
tem s9. On th e oth er h an d, sign ifican t values of JF-F couplin g con stan t in
th e slices at th e sh ifts of th e CF groups allowed to iden tify h igh ly coupled
sign als of CF2O groups. Th us, th e slice at –144 ppm revealed th e sign al of
th e C6F2 group as two an isoch ron ic F sign als with stron g gem in al couplin g
exceedin g 140 com m on for both diastereom ers at –80.4 an d –81.3 ppm .
Sim ilarly, th e slices at –134.6 or –135.4 ppm revealed for both diastereo-
m ers two distin guish ed sets of an isoch ron ic F sign als with large gem in al
couplin g an d rem arkably differen t sh ifts (–78.0 an d –81.1 ppm , an d –77.8
Collect. Czech. Chem. Commun. 2008, Vol. 73, No. 12, pp. 1799–1813

1810
Kysilka et al.:
an d –81.3 ppm , respectively). Fin al assign m en t of th e th ree differen t
CF3 groups relied on couplin g. Th us, th e less coupled sign als at –81.3 or
4
–81.5 ppm were assign ed to th e two diastereom eric C2F3 groups (n o JF-F
couplin g con stan t possible), wh ereas two triplets at –81.0 or –81.1 ppm to
FIG. 1
Upfield part of th e 19F NMR spectrum of im idazolium salt 8
FIG. 2
Assign m en t of th e sign als of perfluoroh exyl group of im idazolium salt 8
Collect. Czech. Chem. Commun. 2008, Vol. 73, No. 12, pp. 1799–1813

HFPO Trimer-Based Alkyl Triflate
1811
th e two diastereom eric C8F3 groups (ch aracteristic sign als of th e perfluoro-
propyl group). Fin ally, th e rem ain in g two sign als at –79.5 or –79.6 ppm
with m ore com plex couplin g pattern s were attributed to th e two diastereo-
m eric C5F3 groups (Fig. 3).
FIG. 3
Assign m en t of th e sign als of perfluoropolyeth er group of im idazolium salt 8
CONCLUSIONS
We developed a n ew h igh ly fluorin ated buildin g block based on HFPO
trim er, wh ich exerts low crystallin ity. Alth ough its reactivity is lower com -
pared to th e an alogous perfluoroalkylated buildin g blocks, it can be substi-
tuted with efficien t n ucleoph iles as im idazole, azide or iodide. In con trast
to kn own bis(polyfluoroalkylated) im idazolium salts, im idazolium salt
based on th is buildin g block is n ot crystallin e. For th e first tim e, full 19F
NMR assign m en ts of HPFO trim er-based com poun ds in cludin g th e distin c-
Collect. Czech. Chem. Commun. 2008, Vol. 73, No. 12, pp. 1799–1813

1812
Kysilka et al.:
tion between in dividual diastereom ers were accom plish ed usin g 19F gCOSY
NMR spectroscopy.
W e thank the Czech Science Foundation (Grant No. 203/06/1511) and the Ministry of
Education, Youth and Sports of the Czech Republic (Research Centre LC 06070, Research Project
No. 6046137301) for financial support.
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