Hexaalkylguanidinium trifluoromethanesulfonates - A general synthesis from tetraalkylureas and triflic anhydride, and properties as ionic liquids

Article abstract of DOI:10.1002/ejoc.200700303

More than thirty hexaalkylguanidinium trifluoromethanesulfonates 12 were prepared from N,N-diethyl-N′,N′-dimethylurea, N,N-dibutyl-N′, N′-diethylurea, or tetrabutylurea, triflic anhydride, and a dialkylamine or cyclic sec-amine in two steps. The combination of the urea and triflic anhydride first yields a bis(tetraalkylamidinio)ether bis(triflate) 10, which is then converted into a salt 12 by reaction with the amine component. The reaction sequence can also be carried out as a one-pot procedure. Eighteen of the prepared guanidinium triflates 12 constitute room-temperature ionic liquids, which were characterized for their melting point, glass transition temperature, viscosity, and refractive index. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

Full text of DOI:10.1002/ejoc.200700303

FULL PAPER
DOI: 10.1002/ejoc.200700303
Hexaalkylguanidinium Trifluoromethanesulfonates – A General Synthesis from
Tetraalkylureas and Triflic Anhydride, and Properties as Ionic Liquids
Helene Kunkel[a] and Gerhard Maas*[a]
Keywords: Guanidinium salts / Ionic liquids / Solvent properties / Amines / Urea, tetrasubstituted
More than thirty hexaalkylguanidinium trifluoromethanesul-
fonates 12 were prepared from N,N-diethyl-NЈ,NЈ-dimeth-
ylurea, N,N-dibutyl-NЈ,NЈ-diethylurea, or tetrabutylurea,
triflic anhydride, and a dialkylamine or cyclic sec-amine in
two steps. The combination of the urea and triflic anhydride
amine component. The reaction sequence can also be carried
out as a one-pot procedure. Eighteen of the prepared guani-
dinium triflates 12 constitute room-temperature ionic liquids,
which were characterized for their melting point, glass tran-
sition temperature, viscosity, and refractive index.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
first yields
a bis(tetraalkylamidinio)ether bis(triflate) 10,
which is then converted into a salt 12 by reaction with the
of them have a high thermal stability[9–11] and, due to the
effective dissipation of the positive charge in the cation, a
better chemical stability than some of the other common
classes of ILs.[12] Various uses of hexaalkylguanidinium-
based RTILs as reaction media have been reported re-
cently.[13] Hexaalkylguanidinium iodides and tricyanome-
thanides have been considered as electrolytes in dye-sensi-
tized solar cells.[14] Further applications of guanidinium ILs
have been proposed in the patent literature, for example as
surfactants in the preparation of mesoporous metal ox-
ides,[15] as electrolytes in electrochemical sensors,[16] and as
hydraulic fluids.[17] The ability of hexaalkylguanidinium to
act as a phase-transfer catalyst[18] can also be a useful prop-
erty of a guanidinium-based RTIL.[13a]
The major approaches to hexaalkylguanidinium salts are
summarized in Scheme 1. Probably the shortest pathway
consists of the reaction of chloroformamidinium salts 1a,
obtained by the chlorination of tetraalkylureas or their cy-
clic relatives (such as N,NЈ-dialkylimidazolin-2-ones) with
phosgene, phosphorus oxychloride, or oxalyl chloride, with
a sec-amine[14,19,20] or a dialkyl(trimethylsilyl)amine.[21]
Kantlehner and coworkers were the first to use the phos-
gene route to prepare a number of peralkylated guanidi-
nium salts from various tetraalkylureas (R1–4 = Me, Et, Bu;
R1 = R2 = Et, R3 = R4 = Pr, Bu, allyl).[19] Tetramethyl-
isothiuronium salt 1b (R1–4 = Me, X = CH3SO4) reacts with
dimethylamine to yield hexamethylguanidinium methylsul-
fate 4;[19b] however, the full potential of this method has not
yet been exploited. O-Alkyluronium salts 1c, easily ob-
tained by the O-alkylation of tetraalkylureas, are only par-
tially suited as precursors to guanidinium salts 4 because
O-ethyl-N,NЈ-tetramethyluronium tetrafluoroborate reacts
in the expected manner with dimethylamine and pyrrolid-
ine, but suffers O-dealkylation when exposed to dipropyl-
amine or morpholine.[22]
Introduction
Ionic liquids (ILs), salts with melting points below about
100 °C, are currently attracting much interest in both aca-
demic and industrial laboratories. Some of their unique
properties,[1,2] such as very low vapor pressure, high thermal
stability, a wide electrochemical window, and tunable misci-
bility with other liquid phases, recommend them as alterna-
tives to the traditional organic liquids for several different
purposes. ILs are currently widely evaluated and used as
reaction media in synthesis,[1,3] as electrolytes for electro-
chemical processes and devices,[4] for applications in separa-
tion and analytical techniques,[5] and as engineering liquids
with various industrial applications.[6]
For practical reasons, ILs with melting points around
room temperature or below are preferred for most applica-
tions. These room-temperature ILs (RTILs) typically con-
sist of an organic cation bearing alkyl substituents of vari-
able chain length and an inorganic or organic anion. Al-
though a great number of charge-stabilized organic cations
are known, N,NЈ-dialkylimidazolium, N-alkylpyridinium,
and quaternary ammonium or phosphonium ions are cur-
rently the most common cations in RTILs. Recently, in-
creasing interest in guanidinium-based ILs can be noticed,
some of which are already commercially available.[7] Guani-
dinium salts, where the parent +C(NH2)3 cation is not fully
alkylated, retain Brönsted acidity due to the remaining NH
bond(s) and may be used as task-specific ILs catalyzing spe-
cific transformations.[8] We focus here, however, on hexaalk-
ylguanidinium salts as ILs, including those which contain
an N,NЈ-dialkylimidazoline or a related ring system. Many
[a] Institute for Organic Chemistry I, University of Ulm,
Albert-Einstein-Allee 11, 89081 Ulm, Germany
Fax: +49-731-50-22803
E-mail: gerhard.maas.@uni-ulm.de
3746
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2007, 3746–3757

Hexaalkylguanidinium Trifluoromethanesulfonates
FULL PAPER
Only a few other hexaalkylguanidinium triflates have been
reported in the meantime;[21b,30] in those cases, the triflate
ion was introduced by anion exchange at one or the other
stage of the synthesis.
Scheme 2. Cyclic hexasubstituted guanidinium triflates 7 and 8.
Scheme 1. Synthetic pathways to hexaalkylguanidinium salts.
Instead of the direct reaction between chloroformamid-
inium salts 1a and amines HNR5R6, a two-step procedure
is often chosen which allows a wider variation of alkyl sub-
stituents R5 and R6. To this end, salt 1a or 1b is first com-
bined with a primary amine to yield a pentaalkylguanidine
2 which can be alkylated with a wide range of alkyl ha-
lides.[10,13a,19b,20,23,24] The twofold alkylation of N,N,NЈ,NЈ-
tetraalkylguanidines, on the other hand, is preferentially
used to prepare guanidinium salts 4 with two equal NЈЈ,NЈЈ-
substituents.[25,26]
Results and Discussion
Synthetic Work
The tetraalkylureas 8A–C served as starting materials for
the synthesis of hexasubstituted guanidinium triflates.
Hexaalkylguanidinium salts can also be obtained from
N,N-dialkylphosgeniminium salts 5 (Scheme 1), either by
reaction with a bis(sec-amine)[27] or with 2 equiv. of a sec-
amine;[9] successive treatment of 5 with 1 equiv. each of
R3R4NH and R5R6NH is also possible and enhances the
structural diversity.[9,27]
As described earlier for tetramethylurea,[28] the reaction
Hexaalkylguanidinium salts 4 prepared by one of the of tetrabutylurea (8C) with triflic anhydride occurs in two
above methods in most cases contain a halide or methylsul- steps (Scheme 3). In the first step, the urea is O-sulfonylated
fate anion. In order to fine tune other solvent properties to give the trifloxy salt 9C which can be isolated (as an
such as melting point, viscosity, and miscibility, an anion extremely moisture-sensitive RTIL!) when the reaction is
exchange is usually required to introduce the often- carried out with 1:1 stoichiometry in CH2Cl2 at Յ 0 °C.
encountered RTIL anions such as BF4, PF6, CF3SO3, This salt reacts with an additional equiv. of urea 8C to form
N(SO2CF3)2, N(CN)2, and B(OR)4.
dication ether salt 10C which is also obtained directly from
Some time ago, P. Stang et al.[28] observed that tetraalk- 8C and Tf2O in a 2:1 ratio at room temperature. We specu-
ylureas react with triflic anhydride to give dication ether lated that the triflate anion could also be displaced from 9C
bis(triflates) which can be cleaved with a variety of nucleo- with secondary amines to provide hexaalkylguanidinium
philes. Thus, the reaction of dication ether salt 6 with dieth- salts 12. However, the reaction of 9C with 2 equiv. of dieth-
ylamine generated the low-melting cyclic guanidinium salt 7 ylamine, dibutylamine, or diisopropylamine resulted in the
(Scheme 2), which in retrospect constitutes one of the early formation of N,N-dialkyl-trifluoromethanesulfonamides 11
examples of a guanidinium-based IL. The analogously pre- and urea 8C, indicating that the amine nucleophile had at-
pared N-phenylated guanidinium salt 8, on the other hand, tacked the sulfur rather than the uronium carbon. On the
is a high-melting solid.[29] We have now returned to these other hand, the same amines smoothly reacted with dicat-
isolated observations to develop a general synthesis of hexa- ion ether salt 10C to form the desired hexaalkyl-substituted
alkylguanidinium triflates from tetraalkylureas, and have guanidinium triflates 12C and urea 8C. Analogous results
found that many of these salts are room-temperature ILs. were obtained with ureas 8A and 8B as starting materials.
Eur. J. Org. Chem. 2007, 3746–3757
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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3747

H. Kunkel, G. Maas
FULL PAPER
10A with (S)-(1-phenylethyl)amine furnished the chiral salt
12Ah. The separation of guanidinium salts 12 from the ac-
companying products, urea 8 and sec-amine hydrotriflate,
was possible by extractive workup; the urea can be reco-
vered from the product mixture by extraction into pentane
and vacuum distillation, and treatment of the salt mixture
with aqueous NaOH removes selectively the ammonium
salt, while guanidinium salts 12 are stable to aqueous base
under these conditions.
Scheme 3. Reaction of uronium salts 9C and 10C with sec-amines.
Having established the reaction pathway, we synthesized
a number of hexasubstituted guanidinium triflates 12 as
shown in Scheme 4. Dication salts 10A–C were prepared in
one step from ureas 8A–C and were isolated. They were
combined with a broad range of sec-amines to provide the
guanidinium triflates 12 listed in Table 1, generally in fair
to good yields. As can be seen, not only dialkylamines, with
linear and branched chains, but also cyclic amines (pyrrol-
idine) and benzylamines can be introduced. The reaction of Scheme 4. Synthesis of guanidinium triflates 12.
–
Table 1. Hexaalkylguanidinium triflates [(NR1 )(NR2 )(NR3R4)C+ CF3SO3 ] prepared and their physical data.
2
2
20[c]
Entry Salt
R1
R2
R3
R4
Tm/Tg
[°C][a]
Tdec
nD
Miscibility with[d]
CH2Cl2/EtOH H2O Et2O/C6H14
[°C][b]
1
2
3
4
5
6
7
8
12Aa
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Bu
Bu
Bu
Bu
Bu
Bu
Bu
Bu
Bu
Bu
Bu
Bu
Bu
Bu
Bu
Bu
Bu
Bu
Bu
Bu
Et
Pr
Et
Pr
240/–
210/–
–/–65
–/–66
–/–51
61/–78
–/–45
45/–42
12/–38
88/–30
–/–40
–/–32
74/–17
–/–66
–/–55
33/–58
–/–69
–/–56
–/–43
21/–60
–/–38
–/–38
–/–32
79/–26
52/–20
58/–56
64/–51
89/–
461
457
452
446
432
458
392
389
457
407
397
391/452
401/510
409
375
435
430
442
392
448
396
396
385
381/511
412
438
433
431
427
439
394
445
379/408
410
–
–
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
–
–
–
+
–
–
+
–
–
–
–
+
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
12Ab
12Ac
12Ad
12Ae
12Af
12Ag
12Ah
12Ai
12Aj
12Ak
12Al
12Am
12An
12Ba
12Bb
12Bc
12Bd
12Be
12Bf
12Bg
12Bh
12Bi
Bu
Hex
R[e]
Bu
Cy
Me
Bu
Hex
R[e]
Me
Me
R[f]
1.460
1.461
1.466
–
1.475
–
1.470
–
1.501
1.495
–
1.458
1.465
1.465
1.464
1.461
1.475
1.472
1.495
1.496
1.493
–
9
–(CH2)4–
Me
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
Bn
Bn
Bn
Bn
R[g]
Et
Et
Bu
Bn
R[g]
Et
Pr
Pr
Hex
Me
Hex
Bu
Cy
Me
–(CH2)4–
Me
Bn
Bn
Bn
Bn
R[g]
Et
Et
Bu
12Bj
Et
Et
Bn
12Bk
12Ca
12Cb
12Cc
12Cd
12Ce
12Cf
12Cg
12Ch
12Cf
R[g]
Et
–
–
–
–
Bu
Bu
Bu
Bu
Bu
Bu
Bu
Bu
Bu
Pr
Pr
Bu
Hex
Me
Me
Bu
Hex
Bu
Cy
49/–
–
–/–59
76/–37
–/–59
87/–32
81/–
1.463
–
1.472
–
–(CH2)4–
Et
Bn
R[g]
R[g]
–
[a] Tm = melting point, Tg = glass transition temperature. [b] Tdec = decomposition temperature under N2 atmosphere. [c] Refractive
index at 20 °C. [d] Visually observed miscibility (solubility in the case of solids) at room temp.; + miscible, – immiscible, C6H14
cyclohexane. [e] R = 2-ethylhexyl. [f] R = (S)-(–)-phenylethyl. [g] R = 2-methoxyethyl.
=
3748
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Eur. J. Org. Chem. 2007, 3746–3757

Hexaalkylguanidinium Trifluoromethanesulfonates
FULL PAPER
The preparation of salts 12 could be simplified further 1535–1544 cm–1 which in some cases was accompanied
by carrying out the two-step transformation as a one-pot by another strong band at wavenumbers higher by 10–
procedure, without the isolation of dication ether salts 10 20 cm–1.
(as we show for 12Ac in the Experimental Section). As ILs
are often placed in the context of green chemistry,[31] their
production should also be carried out under environmen-
tally benign conditions. Therefore, we checked whether
Ionic Liquid Properties
CH2Cl2 can be replaced by non-chlorinated solvents. We
Table 1 provides information on phase transitions, ther-
found that for the one-pot synthesis of 12Ac from urea 8A, mal stability, refractive indices, and miscibility in common
CH2Cl2 can be replaced by cyclohexane as the reaction me- solvents of the newly prepared guanidinium salts 12. It can
dium, and it can also be eliminated from the workup pro- be seen that, with the exception of 12Aa and 12Ab, all of
cedure. However, we had to accept that the yield dropped them can be classified as ILs (melting points below 100 °C),
from 56% to 45%.
and that the majority of these salts are room-temperature
All guanidinium triflates prepared were fully charac- ILs. A rule of thumb is confirmed, namely that a more un-
1
terized by their H and 13C NMR spectroscopic data. In symmetrical substitution in the guanidinium cation tends
agreement with earlier observations,[9,32] the hexaalkylguan- to lower the melting point. For example, the melting point
idinium salts showed restricted rotation around the C+– decreases in the sequence 12Cc (hexabutylguanidinium),
NR2 partial double bonds, giving rise to the magnetic non- 12Cb (tetrabutyl-dipropylguanidinium), 12Ca (tetrabutyl-
equivalence of the chemically equivalent nuclei in the two diethylguanidinium),
12Cd
(tetrabutyl-dihexylguanid-
alkyl chains of a symmetrically substituted NR2 group. For inium). On the other hand, benzyl and 2-methoxyethyl sub-
example, the following δ (13C) values were observed for stituents tend to increase the melting point of the salt. The
12Ac: 40.4/40.6 (NCH3), 43.4/43.9 (NCH2, ethyl), and 48.9/ triflate counterion also has an influence; as Table 2 shows,
49.6 (NCH2, butyl). In addition, for guanidinium salts con- the melting point of the triflate salts is significantly lower
–
taining an asymmetrical NR1R2 group, E/Z isomerism than that of the halide or PF6 salts with the same guanid-
around the iminium partial double bond can give rise to inium cation, while the triflate and tetrafluoroborate salts
two diastereomers which in some cases were clearly recog- share the RTIL property.
nized in the spectra (e.g., 12Af–h, 12Ak, 12Bg, 12Bh) while
DSC measurements revealed that most guanidinium tri-
in some other cases extensive signal overlap prevented a flates 12 also show a glass transition. As with other hexa-
clear conclusion. Furthermore, the benzylic protons of all alkylguanidinium salts,[9] the glass temperature of the salts
PhCH2-substituted guanidinium salts were observed to be bearing simple alkyl groups is typically in the range from
diastereotopic at about 30 °C. This phenomenon was ob- –50 to –78 °C. The presence of cyclohexyl and especially of
served and studied before and has been attributed to a chi- phenyl rings brings this phase transition in the range of –20
ral non-planar (propeller-like) structure of hexalkylguanid- to –45 °C.
inium ions.[32] In the meantime, this has been confirmed
Thermogravimetric analyses indicated the high thermal
even for the hexamethylguanidinium cation, the simplest of stability of hexaalkylguanidinium triflates 12. A typical
the hexaalkylguanidinium cations, in several solid-state TGA curve is shown in Figure 1. The decomposition tem-
structures[33] and in DFT calculations of the gas-phase peratures Tdec (defined here as the temperature of fastest
structure.[33a]
mass loss at a heating rate of 10 °C/min) range from 380 °C
In the IR spectra, all guanidinium salts showed, besides to 460 °C, and complete decomposition in one step takes
the typical bands associated with the triflate anion (around place in almost all cases.
1265, 1150, and 1031 cm–1), strong absorption bands char-
Most of the salts 12 in Table 1 are hydrophobic. Only the
acterizing the guanidinium (CN3+) moiety. In series 12A, salts with the smallest alkyl groups (12Aa, 12Ab, 12Af and
two such absorptions were found at 1575–1588 cm–1 and 12Ai) were found to be water soluble. Interestingly, 12Ac
1542–1558 cm–1; in the two series 12B and 12C, only one, (containing NMe2,NEt2, and NBu2) is water insoluble, but
somewhat broadened, absorption was observed in the range the replacement of one CH2 unit by O in the butyl chains
Table 2. Influence of the anion on the melting point of hexaalkylguanidinium salts.
Entry Cation
M.p. [°C] or physical state at 20 °C for salt with the given anion
Br[b]
Other anion
[a]
[b]
[b]
CF3SO3
BF4
PF6
1
2
3
4
5
6
7
(NMe2)(NEt2)(NBu2)C+
liquid
liquid
33
64
89
12
liquid
liquid
liquid
–
–
66–67
88–89
–
–
70–71
–
–
–
–
(NEt2)(NEt2)(NBu2)C+
(NEt2)(NPr2)(NBu2)C+
(NPr2)(NBu2)(NBu2)C+
(NBu2)(NBu2)(NBu2)C+
(NMe2)(NBu2)(Pyr)C+[d]
(NEt2)(NBu2)(NMeHex)C+
Cl: 55–58[c]
Cl: 55–56[c] Ph4B: 203[c]
Cl: 85[c]
–
–
–
Cl: 147[c]
liquid
–
104–106
–
76–77
–
–
I: highly viscous oil[e]
[a] This work. [b] Ref.[26b]. [c] Ref.[19b]. [d] Pyr = pyrrolidin-1-yl. [e] W. Kantlehner et al., unpublished results.
Eur. J. Org. Chem. 2007, 3746–3757
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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3749

H. Kunkel, G. Maas
FULL PAPER
the range measured at 20 °C for 1,3-dialkylimidazolium tri-
flates bearing short alkyl substituents.[36] The viscosities of
salts 12 increase roughly with the length of the alkyl chains
in the cation, although the last three entries in Table 3 devi-
ate somewhat from this trend. The influence of the triflate
anion on the viscosity cannot be illustrated, since data for
hexaalkylguanidinium ILs with the same cation but dif-
ferent anions are not available. For [(NHex)4(NMe)2C]-
NTf2, viscosities of 346 mPas (25 °C) and 124 mPas (60 °C)
have been reported.[9] The viscosities of 1-methyl-3-butyl-
imidazolium Ils decrease in the anion sequence I Ͼ PF6 Ͼ
BF4 ϾϾ OTf Ͼ NTf2.[35,37] Although it is likely that in
these ILs the viscosity is more strongly affected by the cat-
ion-anion interactions (because of the acidity of the C2–H
bond) compared to salts 12, it is obvious that the triflate
anion contributes to a decrease in viscosity.
Figure 1. TGA curve for salt 12Bc.
is sufficient to make 12An water soluble. It should be noted
that even the salts called “hydrophobic” contain traces of
water and are hygroscopic to some extent. For example, the
water content of a dried sample of 12Ac increased from
420 ppm to 1310 ppm when kept in contact with air for
15 h.
The refractive index data given in Table 1 characterize
the ILs as obtained from the synthesis described in the Ex-
perimental Section. Because of the difficulty in rigorously
purifying these ILs, the values may be somewhat affected by
remaining impurities, including the residual water content.
Nevertheless, it can be stated that the refractive indices are
distinctly higher than in some of the commercially available
imidazolium-based ILs (e.g. [C4mim]X shows refractive in-
dices of 1.433 when X = OTf, 1.451 when X = NTf2, and
1.410 when X = BF4).[34]
Figure 2. Viscosity of some salts 12 as a function of temperature.
Viscosity data for some RTILs 12 are presented in
Table 3 and Figure 2. Again, it should be kept in mind that
these ILs contain traces of water, and as shown for other
ILs, the presence of water can affect the viscosity signifi-
The dependence of the viscosities of the ILs in Table 3
cantly.[35,36] As could be expected, these liquids are rather on shear rate and time was also studied. In each case, the
viscous; on the other hand, they are less viscous at room viscosity remained constant with shear rates increasing
temperature than glycerol (934 mPas at 20 °C), with the ex- from 10 s–1 to 150 s–1. Furthermore, the viscosity was inde-
ception of 12Be. Since viscous reaction media are in general pendent of time for measurements carried out with shear
not welcome, the considerable decrease of viscosity ob- rates that were kept constant (10 s–1 and 100 s–1). In other
served in the often-used temperature range of 60–80 °C is words, no thixotropic or rheopectic behavior was observed.
certainly a bonus. The viscosities at 60 °C (Table 3) are in Both results are typical for Newtonian fluids.
Table 3. Dynamic viscosity of hexaalkylguanidinium triflates at different temperatures.[a]
Entry
Salt
Viscosity η [mPa s]
at 23Ϯ0.01 °C
at 60Ϯ0.01 °C
1
2
3
4
5
6
7
8
[(NMe2)(NEt2)(NBu2)C]OTf (12Ac)
[(NEt2)(NEt2)(NBu2)C]OTf (12Ba)
[(NEt2)(NBu2)(NMeBu)C]OTf (12Bd)
[(NMe2)(NEt2)(NHex2)C]OTf (12Ad)
[(NEt2)(NPr2)(NBu2)C]OTf (12Bb)
[(NEt2)(NBu2)(NHex2)C]OTf (12Bc)
[(NBu2)(NBu2)(NMeBu)C]OTf (12Ce)
[(NEt2)(NBu2)(NCyMe)C]OTf (12Be)
263
332
382
406
516
665
815
5647
44
45
55
53
67
88
85
244
[a] Data were measured on samples which had a water content in the range of 400–700 ppm (12Bd: 970 ppm; 12Be: 1070 ppm) according
to coulometric Karl-Fischer titration.
3750
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© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2007, 3746–3757

Hexaalkylguanidinium Trifluoromethanesulfonates
FULL PAPER
= 118.26 ppm], and 19F spectra were referenced to C6F6 in CDCl3
[δ (C6F6) = –162.9 ppm]. IR spectra were recorded with a Bruker
Vector 22 FTIR spectrometer. Mass spectra were recorded with a
Finnigan MAT SSQ-7000 spectrometer (CI = 100 eV). Microanaly-
ses were carried out with an Elementar vario MICRO cube instru-
ment.
Conclusion and Outlook
We have reported here that a wide range of hexaalkylgua-
nidinium triflates 12, most of which are room-temperature
ILs, can be prepared from tetraalkylureas, triflic anhydride
and dialkylamines in two steps. We have also shown that
isolation of the first-step products, dication ether triflates
10, is not necessary, so that the synthesis can be carried out
as an operationally simple one-pot process. This procedure
is a chloride-free alternative to the preparation from chloro-
formamidinium chlorides 1a or N,N-dialkylphosgenimin-
ium chlorides 5 followed by anion exchange with the ob-
tained hexaalkylguanidinium chlorides to get the triflate
salts. Moreover, it is possible to replace CH2Cl2 by non-
chlorinated solvents as the reaction medium and for
workup. Thus, the preparation of guanidinium triflates 12
can be conducted in a completely chlorine-free manner; as
ILs are often put in the context of green chemistry, this
might be an additional benefit of our method.
O-Trifluoromethylsulfonyl-N,N,NЈ,NЈ-tetrabutyluronium
Triflate
(9C): To solution of triflic anhydride (0.85 g, 0.50 mL,
a
3.00 mmol) in CHCl3 (6 mL), cooled to 0 °C and kept under argon,
was added N,N,NЈ,NЈ-tetrabutylurea (0.85 g, 0.97 mL, 3.00 mmol)
in CHCl3 (6 mL). Evaporation of the solvent at 0.001 mbar left a
yellow oil, which was not purified further due to its extreme moist-
ure sensitivity. 1H NMR (400 MHz, CDCl3): δ = 0.94 (t, 6 H,
CH2CH3), 1.33–1.39 (m, 4 H, CH2CH3), 1.68–1.74 (m, 4 H,
CH2CH2CH3), 3.56–3.59 (m, 4 H, NCH2) ppm. 13C NMR
(100 MHz, CDCl3): δ = 13.3 (CH3), 19.7, 29.1 [(CH2)2CH3], 52.5
(NCH2), 152.2 (CN2) ppm. 19F NMR (376 MHz, CDCl3): δ =
–67.5 (covalent OTf), –74.7 (anionic OTf) ppm.
Reaction of 9C with Et2NH: A solution of 9C in CHCl3 (12 mL)
was cooled to 0 °C, and diethylamine (0.44 g, 0.62 mL, 6.00 mmol)
It has been reported that hexaalkylguanidinium triflates was added. After the addition was completed, the crystallization of
diethylammonium triflate started. The mixture was allowed to
stand in a refrigerator at 4 °C for 3 d, and then the solid was re-
moved by filtration (0.31 g, 46% yield). The residual oil consisted
of N,N,NЈ,NЈ-tetrabutylurea (8C), residual ammonium salt and
N,N-diethyl-trifluoromethanesulfonamide (11). Fractional distil-
lation in a kugelrohr apparatus furnished 11 (80 °C/0.092 mbar,
colorless liquid, 0.34 g, 55% yield) and N,N,NЈ,NЈ-tetrabutylurea
(200 °C/0.092 mbar, yellowish oil, 0.63 g, 74% yield).
are converted efficiently into the corresponding tris(penta-
fluoroethyl)trifluorophosphate salts when treated with the
acid H[(C2F5)3PF3]·5H2O.[21b] The combination of this
anion-exchange reaction with our synthesis of guanidinium
triflates 12 would also render chloride-free the synthesis of
hexaalkylguanidinium salts with [(C2F5)3PF3]– and similar
low-nucleophilicity anions.
The hexaalkylguanidinium triflates reported here can be
expected to find several applications as ILs, based in par-
ticular on the low nucleophilicity and hydrolytic stability of
the triflate anion, the better chemical stability of the cations
as compared to the usual 1,3-dialkylimidazolium-based
ILs[9] and the high thermal stability of these salts. As reac-
tion media, the low nucleophilicity recommends them for
processes in which short-lived electron-deficient intermedi-
ates (e.g. carbocations and onium ions) are involved.[38]
Spectroscopic and Analytical Data for 11: 1H NMR (400 MHz,
CDCl3): δ = 1.26 (t, J = 7.2 Hz, 6 H, CH2CH3), 3.45 (broadened
q, 4 H, CH2CH3) ppm. 13C NMR (100 MHz, CDCl3): δ = 13.9
1
(CH3), 42.7 (NCH2), 120.0 (q, JC,F = 323.4 Hz, CF3) ppm. 19F
NMR (376 MHz, CDCl ): δ = –72.8 ppm. IR (NaCl): ν = 1386
˜
3
(vs) (RSO2N), 1226 (vs), 1184 (vs), 1132 (vs) (RSO2N), 1020 (s),
951 (s) cm–1. MS (CI): m/z (%)
= 206 (100) [M +
H]+.
C5H10F3NO2S (205.50): calcd. C 29.27, H 4.91, N 6.83; found C
29.28, H 4.96, N 7.20.
Furthermore, the ability of the triflate anion to act as a Bis(N,N-diethyl-NЈ,NЈ-dimethylamidinio) Ether Bis(trifluorometh-
anesulfonate) (10A). Typical Procedure: In a 100 mL Schlenk vessel
purged with argon was placed triflic anhydride (2.82 g, 1.65 mL,
10.0 mmol) and dry CH2Cl2 (15 mL). The solution was cooled to
0 °C and N,N-diethyl-NЈ,NЈ-dimethylurea (8A, 2.88 g, 20 mmol) in
CH2Cl2 (10 mL) was added dropwise. After the addition was com-
plete, the reaction mixture was kept at 0 °C for 1 h with magnetic
stirring, brought to room temp., and finally heated at reflux for
12 h. After cooling to room temp., the colorless precipitate was
isolated by filtration and dried (0.001 mbar/8 h) to yield 3.81 g
(67% yield) of 10A, m.p. 170–176 °C. 1H NMR (400 MHz,
weak hydrogen-bond acceptor and the absence of a hydro-
gen-bond donor moiety in the cation (as opposed to 1,3-
dialkylimidazolium cations) are features which they have in
common with the IL, 1-butyl-1-methylpyrrolidinium trifl-
ate, for example. It has been suggested that these features
contribute to the fact that SN2 reactions using mono-, di-,
and tributylamine as nucleophiles, occur significantly faster
in the last-mentioned IL than in [bmim]OTf or in acetoni-
trile and CH2Cl2 solutions.[39] These are only two out of
several more possible applications for ILs consisting of CD3CN): δ = 1.32 (t, 12 H, CH2CH3), 3.15 (s, 12 H, NCH3), 3.57
(q, 8 H, CH2CH3) ppm. 13C NMR (100 MHz, CD3CN): δ = 12.6
hexaalkylguanidinium triflate salts.
(CH2CH3), 42.1 (NCH3), 46.0 (NCH2), 156.9 (CN3) ppm. 19F
NMR (376 MHz, CD CN): δ = –75.6 ppm. IR (KBr): ν = 1687
˜
3
(s), 1666 (s), 1459 (m), 1266 (vs), 1155 (s), 1033 (s), 638 (s) cm–1.
C16H32F6N4O7S2 (570.57): calcd. C 33.68, H 5.65, N 9.82; found
C 33.67, H 5.85, N 9.82.
Experimental Section
General Remarks: Rigorously dried organic solvents were used. All
amines were dried with KOH pellets and in most cases distilled.
NMR spectra were recorded using a Bruker DRX 400 spectrometer
Bis(N,N-dibutyl-NЈ,NЈ-diethylamidinio) Ether Bis(trifluoromethane-
sulfonate) (10B): Prepared according to the typical procedure from
N,N-dibutyl-NЈ,NЈ-diethylurea (8B, 4.56 g, 20 mmol) and triflic an-
hydride (2.82 g, 1.65 mL, 10.0 mmol). Yield: 6.35 g (86%), m.p. 76–
86 °C. 1H NMR (400 MHz, CDCl3): δ = 0.98 [t, 12 H, (CH2)3CH3],
1.38–1.45 (m, 20 H, CH2CH2CH3, NCH2CH3), 1.74–1.78 (m, 8 H,
(1H: 400.13 MHz, 13C: 100.61 MHz, 19F: 376.46 MHz). H NMR
1
spectra were referenced to the proton signal of the solvent [δ
(CDCl3) = 7.26 ppm, δ (CD3CN) = 1.94 ppm], 13C spectra were
referenced to the solvent signal [δ (CDCl3) = 77.0 ppm, δ (CD3CN)
Eur. J. Org. Chem. 2007, 3746–3757
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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3751

H. Kunkel, G. Maas
FULL PAPER
CH2CH2CH2CH3), 3.55 (t, 8 H, NCH2 ethyl), 3.64 (q, 8 H, NCH2 (m, 8 H, NCH2CH2CH3, NCH2CH3) ppm. 13C NMR (100 MHz,
butyl) ppm. 13C NMR (100 MHz, CDCl3): δ = 12.8 [(CH2)3CH3],
13.5 (NCH2CH3), 19.9 (CH2CH2CH3), 29.1 (NCH2CH2), 46.2,
CDCl3): δ = 11.0, 11.2 (CH2CH2CH3), 12.6, 13.0 (CH2CH3), 20.7,
21.0 (CH2CH2CH3), 40.3, 40.5 (NCH3), 43.4, 44.1 (NCH2CH3),
51.5 (NCH2CH3, NCH2CH2), 156.0 (CN3) ppm. 19F NMR 51.0, 51.6 (NCH2CH2CH3), 120.9 (q, 1JC,F = 320.9 Hz, CF3), 163.4
(376 MHz, CDCl ): δ = –74.6 ppm. IR (KBr): ν = 1666 (s), 1635 (CN3) ppm. MS (CI): m/z (%)
=
228 (100) [cation]+.
˜
3
(s), 1476 (m), 1431 (m), 1261 (vs), 1224 (s), 1152 (s), 1032 (s), 638
(s) cm–1. C28H56F6N4O7S2 (738.89): calcd. C 45.51, H 7.64, N 7.58;
found C 45.17, H 7.76, N 7.16.
C14H30F3N3O3S (377.47): calcd. C 44.55, H 8.01, N 11.13; found
C 44.24, H 7.97, N 11.05.
N,N-Dibutyl-NЈ,NЈ-diethyl-NЈЈ,NЈЈ-dimethylguanidinium Trifluoro-
methanesulfonate (12Ac): Prepared from 10A (1.78 g, 3.12 mmol) in
CH2Cl2 (20 mL) and dibutylamine (0.81 g, 1.06 mL, 6.24 mmol);
5 h at reflux temp. Yellowish oil (0.86 g, 68% yield). 1H NMR
(400 MHz, CDCl3): δ = 0.92 [t, 6 H, CH2(CH2)2CH3], 1.18–1.72
(several m, 14 H, NCH2CH3, CH2CH2CH2CH3), 3.004 and 3.010
(2 s, 3 H each, NCH3), 3.17–3.32 (2 m, 8 H, NCH2) ppm. 13C
NMR (100 MHz, CDCl3): δ = 12.7, 13.0, 13.6, 13.7 [(CH2)nCH3],
19.8, 20.1, 29.4, 29.6 [CH2(CH2)2CH3], 40.4, 40.6 (NCH3), 43.3,
43.9 (NCH2CH3), 48.9, 49.6 (NCH2 butyl), 163.5 (CN3) ppm. MS
(CI): m/z (%) = 256 (100) [cation]+. C16H34F3N3O3S (405.52):
calcd. C 47.39, H 8.45, N 10.36; found C 47.31, H 8.46, N 10.30.
Bis(tetrabutylamidinio) Ether Bis(trifluoromethanesulfonate) (10C):
Prepared from N,N,NЈ,NЈ-tetrabutylurea (8C, 14.20 g, 16.10 mL,
50.0 mmol) and triflic anhydride (7.05 g, 4.12 mL, 25.0 mmol) ac-
cording to the typical procedure. As the product did not crystallize
directly from the reaction solution, the solvent was evaporated,
pentane (20 mL) was added to the residue, and the mixture was
stirred for 30 min. A microcrystalline solid formed, which was al-
lowed to deposit and was isolated by decantation of the liquid
phase. This purification procedure was repeated three times. The
product was finally isolated by filtration and dried (0.001 mbar/
8 h), giving a yellowish solid (17.8 g, 84% yield), m.p. 47–55 °C. 1H
NMR (400 MHz, CDCl3): δ = 0.99 (t, 24 H, CH2CH3), 1.38–1.47
(m, 16 H, CH2CH3), 1.70–1.78 (m, 16 H, NCH2CH2), 3.56 (broad
t, 16 H, NCH2) ppm. 13C NMR (100 MHz, CDCl3): δ = 13.6
(CH3), 19.9 (CH2CH3), 29.5 (NCH2CH2), 51.6 (NCH2), 156.0
(CN3) ppm. 19F NMR (376 MHz, CDCl3): δ = –74.6 ppm. IR
N,N-Diethyl-NЈ,NЈ-dihexyl-NЈЈ,NЈЈ-dimethylguanidinium Trifluoro-
methanesulfonate (12Ad): Prepared from 10A (3.42 g, 6.00 mmol)
in CH2Cl2 (40 mL) and dihexylamine (2.22 g, 2.80 mL, 12.0 mmol);
25 h at reflux temp. Colorless oil (1.55 g, 57% yield). 1H NMR
(400 MHz, CDCl3): δ = 0.88 [t, 6 H, (CH2)5CH3], 1.18–1.70 [several
m, 22 H, CH2(CH2)4CH3, NCH2CH3], 3.00 and 3.01 (2 s, 3 H each,
NCH3), 3.14–3.35 (2 m, 8 H, NCH2) ppm. 13C NMR (100 MHz,
CDCl3): δ = 12.7, 13.0, 13.9 (CH2CH3), 22.4, 22.5, 26.3, 26.5, 27.4,
27.6, 31.2, 31.3 [(CH2)4CH3], 40.4, 40.6 (NCH3), 43.4, 44.0 (NCH2
ethyl), 49.3, 49.9 (NCH2 hexyl), 163.5 (CN3) ppm. MS (CI): m/z
(%) = 312 (100) [cation]+. C20H42F3N3O3S (461.29): calcd. C 52.04,
H 9.17, N 9.10; found C 51.53, H 9.02, N 9.11.
(KBr): ν = 1659 (s), 1632 (s), 1466 (m), 1423 (m), 1259 (vs), 1154
˜
(s), 1031 (s), 638 (s) cm–1. C36H72F6N4O7S2 (851.10): calcd. C
50.80, H 8.53, N 6.58; found C 50.54, H 8.57, N 6.57.
N,N,NЈ,NЈ,NЈЈ,NЈЈ-Hexaalkylguanidinium Trifluoromethanesulfon-
ates 12. General Procedure: A suspension of a bis(amidinio)ether
bis(trifluoromethanesulfonate) 10 (ca. 1.5–5 mmol) in dry CH2Cl2
(20–25 mL) was prepared and cooled to 0 °C. A solution of a sec-
amine (2–2.05 equiv. relative to 10) in CH2Cl2 (ca. 5 mL) was
added. After 30 min at 0 °C, the mixture was brought to room
temp., stirred for 1 h and finally heated at reflux for 1–72 h. After
cooling to room temp., the solution was concentrated, and n-pen-
tane (10 mL) was added in order to extract the formed urea 8,
which was recovered from the pentane phase by vacuum distil-
lation. The second liquid (oily) phase was dissolved in CH2Cl2
(15 mL) and extracted with 0.1  NaOH (20 mL), and the organic
phase was then dried with Na2SO4. After removal of the solvent,
salt 12 was obtained. To remove the remaining traces of volatiles
the salt was kept at 0.001 mbar/20 °C for 5 h.
N,N-Diethyl-NЈ,NЈ-bis(2-ethylhexyl)-NЈЈ,NЈЈ-dimethylguanidinium
Trifluoromethanesulfonate (12Ae): Prepared from 10A (0.86 g,
1.50 mmol) in CH2Cl2 (20 mL) and bis(2-ethylhexyl)amine (0.72 g,
0.91 mL, 3.00 mmol); 44 h at reflux temp. Colorless oil (0.21 g,
1
27% yield). H NMR (400 MHz, CDCl3): δ = 0.78–0.90 (m, 12 H,
CH2CH3), 1.15–1.53 [several m, 24 H, NCH2CH3, (CH2)3-
CHCH2CH3], 2.75–3.34 (m, 14 H, NCH2, NCH3) ppm. 13C NMR
(100 MHz, CDCl3): δ = 9.7, 10.08, 10.10, 11.0, 11.20, 11.22, 12.4,
12.70, 12.74, 12.8, 12.9, 13.79, 13.84, 13.9 (C-CH3), 22.7, 22.8, 23.0,
23.77, 23.82, 23.84, 24.1, 24.2, 28.0, 28.2, 28.88, 28.94, 29.06, 29.11,
30.3, 31.0, 31.1, 31.2, 37.0, 37.06, 37.14, 37.3, 37.4, 37.5, 40.18,
40.23, 40.5, 40.6 (NCH3), 43.5, 43.6, 43.9, 44.0 (NCH2), 52.7,
N,N,NЈ,NЈ-Tetraethyl-NЈЈ,NЈЈ-dimethylguanidinium Trifluorometh-
anesulfonate (12Aa): Prepared from 10A (2.00 g, 3.51 mmol) in
CH2Cl2 (20 mL) and diethylamine (0.51 g, 0.72 mL, 7.02 mmol) in
CH2Cl2 (5 mL); 1 h at reflux. Yellowish solid (0.55 g, 45% yield),
m.p. 240 °C. 1H NMR (400 MHz, CDCl3): δ = 1.17–1.23 (m, 12
H, CH2CH3), 2.98 (s, 6 H, CH3), 3.15–3.19 (m, 2 H, CH2CH3),
3.25–3.30 (m, 6 H, CH2CH3) ppm. 13C NMR (100 MHz, CDCl3):
δ = 12.7, 13.0 (CH2CH3), 40.3 (NCH3), 43.3, 43.8 (NCH2), 163.4
(CN3) ppm. 19F NMR (376 MHz, CDCl3): δ = –74.6 ppm. IR
1
53.85, 53.91, 54.0 (NCH2CH), 120.8 (q, JC,F = 320.9 Hz, CF3),
163.9 (CN3) ppm. MS (CI): m/z (%) = 368 (100) [cation]+.
C24H50F3N3O3S (517.73): calcd. C 55.68, H 9.73, N 8.12; found C
55.34, H 9.38, N 8.30.
N-Butyl-NЈ,NЈ-diethyl-N,NЈЈ,NЈЈ-trimethylguanidinium Trifluoro-
methanesulfonate (12Af): Prepared from 10A (1.16 g, 2.03 mmol)
in CH2Cl2 (20 mL) and N-butyl-N-methylamine (0.38 g, 0.51 mL,
4.30 mmol); 9 h at reflux temp. White solid (0.34 g, 46% yield),
(KBr): ν = 2981 (m), 2942 (m), 1580 (s), 1553 (s), 1463 (m), 1423
˜
(m), 1271 (vs), 1222 (m), 1147 (s), 1031 (s) cm–1. MS (CI): m/z (%)
= 200 (100) [cation]+. C12H26F3N3O3S (349.41): calcd. C 41.25, H
7.50, N 12.03; found C 41.07, H 7.49, N 11.99.
1
m.p. 61 °C. H NMR (400 MHz, CDCl3): δ = 0.87 (t, 3 H, butyl-
CH3), 1.12–1.25 (m, 8 H, NCH2CH3, CH2CH2CH3), 1.47–1.60 (m,
2 H, NCH2CH2), 2.94–3.01 (several s, 9 H, NCH3), 3.07–3.23 (m,
N,N-Diethyl-NЈ,NЈ-dimethyl-NЈЈ,NЈЈ-dipropylguanidinium Trifluoro- 6 H, NCH2) ppm. 13C NMR (100 MHz, CDCl3): δ = 12.7
methanesulfonate (12Ab): Prepared from 10A (1.14 g, 2.00 mmol)
(CH2CH3), 13.4 (butyl-CH3), 19.7, 19.8 (NCH2CH2CH2), 29.1,
in CH2Cl2 (20 mL) and dipropylamine (0.40 g, 0.60 mL, 29.3 (NCH2CH2), 37.76, 37.82, 39.9, 40.2, 43.37, 43.45, 43.94
1
4.20 mmol); 11 h at reflux temp. White solid (0.55 g, 75% yield),
(NCH3, NCH2CH3), 52.2, 52.6 (NCH2 butyl), 120.8 (q, JC,F =
1
m.p. 211 °C. H NMR (400 MHz, CDCl3): δ = 0.89–0.94 (m, 6 H, 320.9 Hz, CF3), 163.2 (CN3) ppm. MS (CI): m/z (%) = 214 (100)
CH2CH2CH3), 1.16–1.23 (m, 6 H, CH2CH3), 1.50–1.83 (m, 4 H,
CH2CH2CH3), 2.990 and 2.994 (2 s, 3 H each, NCH3), 3.02–3.34
[cation]+. C13H28F3N3O3S (363.44): calcd. C 42.96, H 7.77, N
11.56; found C 42.41, H 7.70, N 11.49.
3752
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© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2007, 3746–3757

Hexaalkylguanidinium Trifluoromethanesulfonates
FULL PAPER
N-Cyclohexyl-NЈ,NЈ-diethyl-N,NЈЈ,NЈЈ-trimethylguanidinium Tri-
163.1 (CN3) ppm. MS (CI): m/z (%) = 262 (100) [cation]+.
fluoromethanesulfonate (12Ag): Prepared from 10A (1.17 g, C17H28F3N3O3S (411.48): calcd. C 49.62, H 6.86, N 10.21; found
2.05 mmol) in CH2Cl2 (20 mL) and N-cyclohexyl-N-methylamine C 49.45, H 6.93, N 10.11.
(0.52 g, 0.60 mL, 4.50 mmol); 12 h at reflux temp. Yellowish oil
N-Benzyl-N-butyl-NЈ,NЈ-diethyl-NЈЈ,NЈЈ-dimethylguanidinium Tri-
fluoromethanesulfonate (12Al): Prepared from 10A (1.71 g,
3.00 mmol) in CH2Cl2 (25 mL) and N-benzyl-N-butylamine
(0.99 g, 1.09 mL, 6.10 mmol); 22 h at reflux temp. Yellow oil
(0.74 g, 57% yield). 1H NMR (400 MHz, CDCl3): δ = 0.89–0.92
(m, 3 H, butyl-CH3), 1.13–1.91 (several m, 10 H, 2 NCH2CH3,
NCH2CH2CH2CH3), 2.88–3.33 [4 s and several m, 12 H, NCH2-
CH2CH2CH3, N(CH3)2, 2 NCH2CH3], 4.20–4.39 (m, 2 H,
NCH2Ph), 7.19–7.23 (m, 2 H, Ar-H), 7.33–7.38 (m, 3 H, Ar-H)
ppm. 13C NMR (100 MHz, CDCl3): δ = 12.4, 12.8, 12.9, 13.3
(NCH2 CH3 , butyl-CH3 ), 19.5, 19.7, 28.9, 29.4 (NCH2 -
CH2CH2CH3), 39.7, 40.0, 40.1, 40.3 (NCH3), 43.1, 43.2, 43.4, 43.9
(NCH2CH3), 48.7, 49.8 (NCH2 butyl), 53.1, 53.6 (NCH2Ph), 120.7
(0.56 g, 70% yield). 1H NMR (400 MHz, CDCl3): δ = 0.95–1.87
(m, 16 H, NCH2CH3, CH2 cy), 2.72–2.90 (10 H, NCH3, CH cy),
2.99–3.21 (m, 4 H, NCH2CH3) ppm; all multiplets were unstruc-
tured, indicating dynamic processes. MS (CI): m/z (%) = 240 (100)
[cation]+. C15H30F3N3O3S (389.48): calcd. C 46.26, H 7.76, N
10.79; found C 46.11, H 7.53, N 10.75.
N,N-Diethyl-NЈ,NЈЈ,NЈЈ-trimethyl-NЈ-[(S)-1-phenylethyl]guanidin-
ium Trifluoromethanesulfonate (12Ah): Prepared from 10A (1.14 g,
2.00 mmol) in CH2Cl2 (15 mL) and (S)-(–)-N-methyl-N-(1-phenyl-
ethyl)amine (0.55 g, 4.10 mmol); 20 h at reflux temp. Yellowish so-
lid (0.19 g, 24% yield). 1H NMR (400 MHz, CDCl3): δ = 0.89–1.26
(m, 6 H, CH2CH3), 1.60 (d, 3 H, CHCH3), 2.28–3.38 (several m
and s, 13 H, NCH3, NCH2CH3), 4.67 (m, 1 H, NCH), 7.18–7.39
(m, 5 H, Ar-H) ppm. 13C NMR (100 MHz, CDCl3): δ = 12.3, 12.7,
1
(q, JC,F = 320.9 Hz, CF3), 128.27, 128.32, 128.7, 128.9, 129.1,
133.8, 133.9 (Ar-C), 162.78, 162.86 (CN3) ppm. MS (CI): m/z (%)
= 290 (100) [cation]+. C19H32F3N3O3S (439.54): calcd. C 51.92, H
7.34, N 9.56; found C 51.41, H 7.34, N 9.81.
12.9, 15.2, 15.6 (CH2CH3, CHCH3), 32.6, 40.3, 40.6, 42.1, 43.2,
1
43.7, 44.1 (NCH3, NCH2CH3), 59.9 (NCH), 120.9 (q, JC,F
=
321.0 Hz, CF3), 125.5, 126.5, 128.9, 129.0, 129.2, 138.2 (Ar-C),
163.6 (CN3) ppm. MS (CI): m/z (%) = 262 (100) [cation]+. [α]2D0
=
N,N-Dibenzyl-NЈ,NЈ-diethyl-NЈЈ,NЈЈ-dimethylguanidinium Tri-
fluoromethanesulfonate (12Am): Prepared from 10A (1.71 g,
3.00 mmol) in CH2Cl2 (25 mL) and dibenzylamine (1.20 g,
1.18 mL, 6.10 mmol); 24 h at reflux temp. White solid (0.76 g, 53%
yield), m.p. 74 °C. 1H NMR (400 MHz, CDCl3): δ = 1.21 and 1.25
(2 t, 6 H, NCH2CH3), 3.03 (s, 3 H, NCH3), 3.10 (s, 3 H, NCH3),
3.17–3.57 (4 m, 4 H, NCH2CH3), 3.97–4.00 (m, 2 H, CH2Ph), 4.23–
4.32 (m, 2 H, CH2Ph), 7.18–7.26 (m, 4 H, Ar-H), 7.41–7.46 (m,
6 H, Ar-H) ppm. 13C NMR (100 MHz, CDCl3): δ = 12.5, 13.1
(NCH2CH3), 40.3, 40.7 (NCH3), 43.5, 43.6 (NCH2CH3), 53.3, 54.1
28.7 (c = 7.7, EtOH). C17H28F3N3O3S (411.48): calcd. C 49.62, H
6.86, N 10.21; found C 49.44, H 6.80, N 10.28.
N,N-Diethyl-NЈ,NЈ-dimethyl-NЈЈ,NЈЈ-tetramethyleneguanidinium
Trifluoromethanesulfonate (12Ai): Prepared from 10A (1.37 g,
2.40 mmol) in CH2Cl2 (20 mL) and pyrrolidine (0.36 g, 0.42 mL,
5.05 mmol); 6 h at reflux temp. Yellowish oil (0.26 g, 31% yield).
1H NMR (400 MHz, CDCl3): δ = 1.19 (t, 6 H, NCH2CH3), 2.01
(m, 4 H, CH2CH2), 2.97 (s, 6 H, NCH3), 3.24 (q, 4 H, NCH2CH3),
3.41 (br. s, 2 H, NCH2 ring), 3.48 (br. s, 2 H, NCH2 ring) ppm.
13C NMR (100 MHz, CDCl3): δ = 13.0 (NCH2CH3), 24.8, 25.2
(CH2CH2), 40.3 (NCH3), 43.5 (NCH2), 49.6, 49.7 (NCH2), 160.0
1
(NCH2Ph), 120.9 (q, JC,F = 320.6 Hz, CF3), 128.7, 128.8, 129.1,
129.2, 129.4, 133.8, 133.9 (Ar-C), 163.0 (CN3) ppm. MS (CI): m/z
(%) = 324 (100) [cation]+. C22H30F3N3O3S (473.55): calcd. C 55.80,
H 6.39, N 8.87; found C 55.77, H 6.38, N 8.73.
( CN3 ) ppm. MS (CI): m /z ( % ) = 1 9 8 ( 1 0 0 ) [ c at i o n]+
.
C11H24F3N3O3S (347.40): calcd. C 41.49, H 6.96, N 12.10; found
C 41.74, H 7.20, N 12.24.
N,N-Dimethyl-NЈ,NЈ-diethyl-NЈЈ,NЈЈ-bis(2-methoxyethyl)guan-
idinium Trifluoromethanesulfonate (12An): Prepared from 10A
(1.71 g, 3.00 mmol) in CH2Cl2 (25 mL) and bis(2-methoxyethyl)
amine (0.81 g, 0.90 mL, 6.10 mmol); 22 h at reflux temp. Yellow oil
N-Benzyl-NЈ,NЈ-diethyl-N,NЈЈ,NЈЈ-trimethylguanidinium Trifluoro-
methanesulfonate (12Aj): Prepared from 10A (2.09 g, 3.60 mmol)
in CH2Cl2 (40 mL) and N-benzyl-N-methylamine (0.89 g, 0.95 mL,
7.32 mmol); 12 h at reflux temp. White solid (0.57 g, 39% yield),
1
(0.74 g, 60% yield). H NMR (400 MHz, CDCl3): δ = 1.16/1.18 (2
1
t, 6 H, NCH2CH3), 2.92/3.00 (2 s, 3 H each, OCH3), 3.30
[s, 6 H N(CH3)2], 3.15–3.70 (several m, 12 H, NCH2CH3,
NCH2CH2OCH3) ppm. 13C NMR (100 MHz, CDCl3): δ = 12.1,
12.7 (NCH2CH3), 39.7, 40.3 (NCH3), 43.2, 43.8 (NCH2CH3), 48.8,
49.9 (NCH2CH2OCH3), 58.7 (NCH2CH2OCH3), 68.6, 68.8
(NCH2CH2OCH3), 164.6 (CN3) ppm. 19F NMR (376 MHz,
m.p. 88 °C. H NMR (400 MHz, CDCl3): δ = 1.19 (broadened t, 6
H, NCH2CH3), 2.78–3.45 (several m and s, 13 H, 3 NCH3, 2
NCH2), 4.12–4.24 (m, 1 H, NCH2Ph), 4.40–4.49 (m, 1 H,
NCH2Ph), 7.21–7.23 (m, 2 H, Ar-H), 7.26–7.38 (m, 3 H, Ar-H)
ppm. 13C NMR (100 MHz, CDCl3): δ = 12.7, 12.9 (NCH2CH3),
38.0, 38.3, 39.8, 40.5, 40.7 (NCH3), 43.1, 43.4, 43.6, 44.3
1
CDCl ): δ = –74.6 ppm. IR (KBr): ν = 2979 (m), 2938 (m), 2898
˜
3
(NCH2CH3), 56.4, 56.8 (NCH2Ph), 120.9 (q, JC,F = 320.7 Hz,
(m), 2831 (m), 1584 (s), 1547 (s), 1460 (m), 1422 (m), 1270 (vs),
1223 (m), 1151 (s), 1118 (s), 1031 (s) cm–1. MS (CI): m/z (%) = 260
(100) [cation]+. C14H30F3N3O5S (409.47): calcd. C 41.07, H 7.38,
N 10.26; found C 40.81, H 7.30, N 10.51.
CF3), 128.5, 128.6, 128.7, 128.8, 128.9, 129.1, 129.3, 133.9 (Ar-C),
163.1 (CN3) ppm. MS (CI): m/z (%) = 248 (100) [cation]+.
C16H26F3N3O3S (397.46): calcd. C 48.35, H 6.59, N 10.57; found
C 48.77, H 6.72, N 10.61.
N-Benzyl-N,NЈ,NЈ-triethyl-NЈЈ,NЈЈ-dimethylguanidinium Trifluoro-
methanesulfonate (12Ak): Prepared from 10A (1.71 g, 3.00 mmol)
N,N-Dibutyl-NЈ,NЈ,NЈЈ,NЈЈ-tetraethylguanidinium Trifluoro-
methanesulfonate (12Ba): Prepared from 10B (1.48 g, 2.00 mmol) in
in CH2Cl2 (25 mL) and N-benzyl-N-ethylamine (0.82 g, 0.91 mL, CH2Cl2 (20 mL) and diethylamine (0.30 g, 0.42 mL, 4.10 mmol);
6.10 mmol); 72 h at reflux temp. Orange oil (0.86 g, 70% yield). 1H
17 h at reflux temp. Yellow oil (0.26 g, 30 % yield). 1H NMR
NMR (400 MHz, CDCl3): δ = 1.13–1.28 (m, 9 H, NCH2CH3),
(400 MHz, CDCl3): δ = 0.97 (t, 6 H, CH2CH2CH3), 1.19–1.73 (sev-
2.85/2.91/3.01/3.08 [4 s, 6 H, N(CH3)2], ca. 3.0–3.36 (m, 6 H, 3 eral m, 20 H, CH2CH2CH3, NCH2CH3), 3.03–3.43 (several m, 12
NCH2CH3), 4.26–4.34 (m, 2 H, NCH2Ph), 7.19–7.23 (m, 2 H, Ar- H, NCH2) ppm. 13C NMR (100 MHz, CDCl3): δ = 12.8, 12.9, 13.6
H), 7.33–7.38 (m, 3 H, Ar-H) ppm. 13C NMR (100 MHz, CDCl3):
(CH2CH2CH3), 20.0, 29.5 (CH2CH2CH3), 43.9 (NCH2 ethyl), 49.5
δ = 12.5, 12.7, 13.1, 13.3 (NCH2CH3), 39.9, 40.2, 40.6, 43.4, 44.1, (NCH2 butyl), 163.8 (CN3) ppm. MS (CI): m/z (%) = 284 (100)
44.2, 45.1 (NCH3, NCH2CH3), 52.7, 53.2 (NCH2Ph), 120.9 (q,
[cation]+. C18H38F3N3O3S (433.57): calcd. C 49.86, H 8.83, N 9.69;
1JC,F = 321.0 Hz, CF3), 128.4, 128.9, 129.1, 129.2, 129.3 (Ar-C), found C 49.80, H 8.90, N 9.67.
Eur. J. Org. Chem. 2007, 3746–3757
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3753

H. Kunkel, G. Maas
FULL PAPER
N,N-Dibutyl-NЈ,NЈ-diethyl-NЈЈ,NЈЈ-dipropylguanidinium Trifluoro-
methanesulfonate (12Bb): Prepared from 10B (1.48 g, 2.00 mmol) in
CH2Cl2 (20 mL) and dipropylamine (0.43 g, 0.56 mL, 4.20 mmol);
24 h at reflux temp. A yellowish oil was obtained which solidified
over two weeks. Yield: 0.21 g (23% yield); m.p. 33 °C. 1H NMR
3.00 mmol) in CH2Cl2 (25 mL) and pyrrolidine (0.43 g, 0.50 mL,
6.10 mmol); 20 h at reflux temp. Yellowish oil (0.42 g, 32% yield).
1H NMR (400 MHz, CDCl3): δ = 1.16 (t, 6 H, CH3), 1.18 (t, 6 H,
CH3 ), 1.28 (m, 4 H, CH2 CH2 CH2 CH3 ), 1.50 (m, 4 H,
CH2CH2CH2CH3), 2.03 (m, 4 H, CH2CH2CH2 ring), 3.11 (t, 4 H,
(400 MHz, CDCl3): δ = 0.90 [2 t, 12 H, (CH2)2CH3], 1.16–1.23 [2 NCH2 butyl), 3.23 (br. q, 4 H, NCH2CH3), 3.40 (m, 4 H, NCH2
m, 14 H, NCH2CH3, NCH2(CH2)2], 1.46–1.79 (2 m, 4 H,
ring) ppm. 13C NMR (100 MHz, CDCl3): δ = 12.8, 13.6 (CH3),
NCH2CH2CH3), 2.91–3.39 (m, 12 H, NCH2) ppm. 13C NMR 19.9, 24.8, 24.9, 29.3 (CH2), 43.7 (NCH2 ethyl), 49.3, 49.7, 50.1
1
(100 MHz, CDCl3): δ = 11.1, 12.6, 12.7, 13.4, 13.5 (CH3), 19.9, (NCH2 butyl, ring), 120.7 (q, JC,F = 320.8 Hz, CF3), 160.0 (CN3).
20.7, 20.8, 29.3, 29.4 [NCH2CH2, NCH2(CH2)2], 43.8, 49.3, 49.4, MS (CI): m/z (%) = 282 (100) [cation]+. C18H36F3N3O3S (431.56):
1
51.3 (NCH2), 120.9 (q, JC,F = 321.1 Hz, CF3), 163.8 (CN3) ppm.
calcd. C 50.10, H 8.41, N 9.74; found C 50.10, H 8.30, N 9.74.
19F NMR (376 MHz, CDCl ): δ = –74.6 ppm. IR (NaCl): ν = 2965
˜
3
N-Benzyl-NЈ,NЈ-dibutyl-NЈЈ,NЈЈ-diethyl-N-methylguanidinium Tri-
fluoromethanesulfonate (12Bg): Prepared from 10B (2.22 g,
3.00 mmol) in CH2Cl2 (25 mL) and N-benzyl-N-methylamine
(0.74 g, 0.79 mL, 6.10 mmol); 72 h at reflux temp. Yellow oil
(1.09 g, 75% yield). 1H NMR (400 MHz, CDCl3): δ = 0.88–0.96
(several t, 6 H, 2 CH2CH3), 1.17–1.67 (several m, 14 H, 2 CH2CH3,
2 CH2(CH2)2CH3), 2.77/2.79 (2 s, 3 H together, NCH3), 2.91–3.64
(m, 8 H, NCH2), 4.29–4.41 (m, 2 H, CH2Ph), 7.18–7.20 (m, 2 H,
Ar-H), 7.35–7.38 (m, 3 H, Ar-H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 12.74, 12.79, 13.49, 13.53, 13.57 (CH2CH3), 19.75,
19.89, 19.99, 20.09, 29.49, 29.52 [CH2(CH2)2CH3], 38.2, 38.3
(NCH3), 42.8, 43.7, 43.8, 44.1 (NCH2 ethyl), 48.5, 49.3, 49.4, 49.6
(s), 2937 (s), 2876 (m), 1539 (s), 1461 (m), 1440 (m), 1270 (vs), 1222
(m), 1146 (s), 1031 (s) cm–1. MS (CI): m/z (%) = 312 (100)
[cation]+. C20H42F3N3O3S (461.63): calcd. C 52.04, H 9.17, N 9.10;
found C 51.67, H 9.05, N 9.17.
N,N-Dibutyl-NЈ,NЈ-diethyl-NЈЈ,NЈЈ-dihexylguanidinium Trifluoro-
methanesulfonate (12Bc): Prepared from 10B (1.48 g, 2.00 mmol) in
CH2Cl2 (20 mL) and dihexylamine (0.78 g, 0.98 mL, 4.20 mmol);
17 h at reflux temp. Yellowish oil (0.61 g, 56% yield). 1H NMR
(400 MHz, CDCl3): δ = 0.82 (s, 6 H, CH3), 0.88 (s, 3 H, CH3), 0.89
(s, 3 H, CH3), 1.14 (s, 6 H, CH3 ethyl), ca. 1.20–1.70 [m, 24 H,
CH2(CH2)4CH3, NCH2CH3 and CH2(CH2)2CH3], 3.00–3.38 (sev-
eral m, 12 H, NCH2) ppm. 13C NMR (100 MHz, CDCl3): δ =
12.61, 12.64, 13.38, 13.41, 13.7 (CH3), 19.82, 19.85, 22.3, 22.9,
26.28, 26.33, 27.26, 27.29, 29.24, 29.41, 31.04, 31.08 [(CH2)nCH3,
n = 2,4], 43.71, 43.74 (NCH2 ethyl), 49.25, 49.35, 49.49, 49.53
(NCH2 butyl, hexyl), 120.9 (q, 1JC,F = 320.9 Hz, CF3), 163.7 (CN3)
ppm. MS (CI): m/z (%) = 396 (100) [cation]+, 544 (3) [M]+.
C26H54F3N3O3S (545.79): calcd. C 57.22, H 9.97, N 7.70; found C
56.99, H 9.85, N 7.68.
1
(NCH2 butyl), 56.6, 56.8 (NCH2Ph), 120.9 (q, JC,F = 320.9 Hz,
CF3), 122.5, 128.6, 128.7, 128.9, 129.2, 129.3, 133.6, 133.8 (Ar-C),
163.3, 163.5 (CN3) ppm. MS (CI): m/z (%) = 332 (100) [cation]+.
C22H38F3N3O3S (481.62): calcd. C 54.86, H 7.95, N 8.72; found C
54.12, H 7.78, N 8.65.
N-Benzyl-NЈ,NЈ-dibutyl-N,NЈЈ,NЈЈ-triethylguanidinium Trifluoro-
methanesulfonate (12Bh): Prepared from 10B (2.22 g, 3.00 mmol)
in CH2Cl2 (25 mL) and N-benzyl-N-ethylamine (0.82 g, 0.91 mL,
1
6.10 mmol); 72 h at reflux temp. Yellow oil (0.95 g, 64% yield). H
N,N,NЈ-Tributyl-NЈЈ,NЈЈ-diethyl-NЈ-methylguanidinium Trifluoro-
methanesulfonate (12Bd): Prepared from 10B (1.48 g, 2.00 mmol)
in CH2Cl2 (20 mL) and N-butyl-N-methylamine (0.36 g, 0.48 mL,
4.10 mmol); 10 h at reflux temp. Colorless oil (0.61 g, 68% yield).
1H NMR (400 MHz, CDCl3): δ = 0.82–0.88 (overlapping triplets,
9 H, 3 CH2CH3), 1.09–1.61 [m, 18 H, 2 CH3, (CH2)2CH3], 2.89 (s, 3
H, NCH3), 2.90–3.31 (m, 10 H, NCH2) ppm. 13C NMR (100 MHz,
CDCl3): δ = 12.4, 12.5, 12.6, 12.8, 13.29, 13.32, 13.4, 19.6, 19.69,
19.73, 19.76, 19.81 (CH3), 29.0, 29.1, 29.2, 29.3, 29.5 [(CH2)2CH3],
37.9, 38.1 (NCH3), 43.2, 43.6, 43.7, 43.8 (NCH2 ethyl), 48.8, 49.2,
NMR (400 MHz, CDCl3): δ = 0.88–0.99 (several t, 6 H, CH3 bu-
tyl), 1.17–1.64 [m, 17 H, NCH2CH3, CH2(CH2)2CH3], 2.80–3.49
(m, 10 H, 5 NCH2), 4.25–4.42 (2 overlapping AB spin systems, 2
H, NCH2Ph), 7.17–7.18 (m, 2 H, Ar-H), 7.36–7.40 (m, 3 H, Ar-H)
ppm. 13C NMR (100 MHz, CDCl3): δ = 12.69, 12.72, 12.86, 12.91,
13.54, 13.58, 13.61 (CH3), 19.37, 19.7, 20.0, 20.1, 29.3, 29.4, 29.5,
29.6 [CH2(CH2)2CH3], 43.3, 43.91, 43.98, 44.2, 44.6, 44.7 (NCH2
ethyl), 49.0, 49.4, 49.5, 49.6, 53.1 (NCH2 butyl, NCH2Ph), 122.5,
124.8, 128.3, 128.4, 129.0, 129.1, 129.3, 129.4, 133.8 (Ar-C), 163.5
( CN3 ) ppm. MS (CI): m / z ( % ) = 3 4 6 ( 1 00 ) [ c at i o n]+
.
1
49.3, 49.4, 52.48, 52.51 (NCH2 butyl), 120.7 (q, JC,F = 321.0 Hz,
C23H40F3N3O3S (495.64): calcd. C 55.73, H 8.13, N 8.48; found C
55.35, H 8.15, N 8.44.
CF3), 163.53, 163.54 (CN3) ppm. MS (CI): m/z (%) = 298 (100)
[cation]+. C19H40F3N3O3S (447.60): calcd. C 50.98, H 9.01, N 9.39;
found C 50.51, H 8.98, N 9.42.
N-Benzyl-N-butyl-NЈ,NЈ-diethyl-NЈЈ,NЈЈ-dibutylguanidinium Tri-
fluoromethanesulfonate (12Bi): Prepared from 10B (2.21 g,
3.00 mmol) in CH2Cl2 (25 mL) and N-benzyl-N-butylamine
(0.99 g, 1.09 mL, 6.10 mmol); 22 h at reflux temp. Yellow oil
(0.74 g, 57% yield). 1H NMR (400 MHz, CDCl3): δ = 0.94–1.01
(several t, 9 H, butyl-CH3), 1.24–1.84 (several m, 18 H, 2
NCH2CH3, 3 NCH2CH2CH2CH3), 2.94–3.56 (several m, 10 H,
NCH2), 4.31–4.42 (m, 2 H, NCH2Ph), 7.19–7.22 (m, 2 H, Ar-H),
7.40–7.44 (m, 3 H, Ar-H) ppm. 13C NMR (100 MHz, CDCl3): δ =
12.7, 12.8, 12.9, 13.5, 13.55, 13.57, 13.6 (NCH2 CH3 ,
NCH2CH2CH2CH3), 19.9, 20.0, 20.1 (NCH2CH2CH2CH3), 29.2,
29.27, 29.29, 29.3, 29.7 (NCH2CH2CH2CH3), 43.4, 43.8, 44.0, 44.1
(NCH2 ethyl), 49.1, 49.3, 49.44, 49.46, 49.50, 49.6, 53.68, 53.71
(NCH2 butyl, NCH2Ph), 128.3, 128.4, 129.1, 129.2, 129.3, 133.7
(Ar-C), 163.5 (CN3) ppm. MS (CI): m/z (%) = 374 (100) [cation]+.
C25H44F3N3O3S (523.70): calcd. C 57.34, H 8.47, N 8.02; found C
57.19, H 8.32, N 8.36.
N,N-Dibutyl-NЈ-cyclohexyl-NЈЈ,NЈЈ-diethyl-NЈ-methylguanidinium
Trifluoromethanesulfonate (12Be): Prepared from 10B (1.51 g,
2.05 mmol) in CH2Cl2 (20 mL) and N-cyclohexyl-N-methylamine
(0.46 g, 0.54 mL, 4.10 mmol); 12 h at reflux temp. Yellowish oil
1
(0.62 g, 62% yield). H NMR (400 MHz, CDCl3): δ = 0.91/0.92 [2
t, 3 H each, N(CH2)2CH3], 1.18–1.93 (several m, 24 H, NCH2CH3,
9 CH2), 2.86 (s, 3 H, NCH3), 3.01–3.32 (m, 9 H, 4 NCH2, NCH)
ppm. 13C NMR (100 MHz, CDCl3): δ = 12.6, 12.7, 12.8, 13.49,
13.55 [(CH2)nCH3], 19.9, 20.0, 24.79, 24.82, 25.6, 25.7, 25.8, 29.2,
29.26, 29.28, 29.31, 29.37, 29.40, 31.57, 31.63, 33.5, 33.6 [CH2CH3,
CH2 cy, (CH2)nCH3], 43.1, 43.6, 43.9, 44.1, 48.8, 49.2, 49.5, 49.6
1
(NCH2, NCH3), 61.7, 61.8 (NCH), 120.9 (q, JC,F = 321.2 Hz,
CF3), 164.2, 164.3 (CN3) ppm. MS (CI): m/z (%) = 324 (100)
[cation]+. C21H42F3N3O3S (473.64): calcd. C 53.25, H 8.94, N 8.87;
found C 53.48, H 8.92, N 8.93.
N,N-Dibutyl-NЈ,NЈ-diethyl-NЈЈ,NЈЈ-tetramethyleneguanidinium Tri-
fluoromethanesulfonate (12Bf): Prepared from 10B (2.22 g,
N,N-Dibenzyl-NЈ,NЈ-dibutyl-NЈЈ,NЈЈ-diethylguanidinium Trifluoro-
methanesulfonate (12Bj): Prepared from 10B (2.22 g, 3.00 mmol) in
3754
www.eurjoc.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2007, 3746–3757

Hexaalkylguanidinium Trifluoromethanesulfonates
FULL PAPER
CH2Cl2 (20 mL) and dibenzylamine (1.20 g, 1.18 mL, 6.10 mmol);
72 h at 80 °C in a closed Schlenk tube. White solid (0.50 g, 30%
yield), m.p. 79 °C. 1H NMR (400 MHz, CDCl3): δ = 0.97, 1.00,
1.29, 1.35 (4 t, 3 H each, CH3), ca. 1.15–1.87 [m, 8 H, CH2(CH2)2-
CH3], 3.04–3.56 (several m, 8 H, 4 NCH2), 4.01–4.25 (2 overlapping
AB spin systems, 4 H, NCH2Ph), 4.23 (d, J = 14.0 Hz, 2 H,
crystalline solid (0.52 g, 48 % yield), m.p. 89 °C. 1H NMR
(400 MHz, CDCl3): δ = 0.95 (t, 18 H, CH3), 1.27–1.43 (m, 18 H,
CH2CH2CH2CH3) 1.66–1.78 (m, 6 H, CH2CH2CH2CH3), 3.01–
3.09 (m, 6 H, NCH2), 3.25–3.32 (m, 6 H, NCH2) ppm. 13C NMR
(100 MHz, CDCl3): δ = 13.6 (CH3), 20.0 (CH2CH3), 29.5
(CH2CH2CH3), 49.5 (NCH2), 164.1 (CN3) ppm. MS (CI): m/z (%)
= 396 (100) [cation]+. C26H54F3N3O3S (545.79): calcd. C 57.22, H
9.97, N 7.70; found C 57.15, H 9.96, N 7.75.
NCH2Ph), 7.16 (d, 4 H, Ar-H), 7.44–7.48 (m, 6 H, Ar-H) ppm. 13
C
NMR (100 MHz, CDCl3): δ = 12.7, 13.0, 13.65, 13.68 (CH3), 20.0,
20.2, 29.3, 29.8 [CH2(CH2)2CH3], 43.7, 44.3 (NCH2 ethyl), 49.2,
49.7 (NCH2 butyl), 53.7, 53.8 (NCH2Ph), 128.6, 128.7, 129.3,
129.4, 129.5, 129.6, 133.5, 133.6 (Ar-C), 163.3 (CN3) ppm. MS
(CI): m/z (%) = 408 (100) [cation]+. C28H42F3N3O3S (557.71):
calcd. C 60.30, H 7.59, N 7.53; found C 60.19, H 7.45, N 7.63.
N,N,NЈ,NЈ-Tetrabutyl-NЈЈ,NЈЈ-dihexylguanidinium Trifluoro-
methanesulfonate (12Cd): Prepared from 10C (1.28 g, 1.50 mmol)
in CH2Cl2 (20 mL) and dihexylamine (0.56 g, 0.70 mL, 3.00 mmol);
21 h at reflux temp. Colorless solid (0.32 g, 35% yield), m.p. 50 °C.
1H NMR (400 MHz, CDCl3): δ = 0.88 (t, 6 H, CH3 hexyl), 0.95 (t,
12 H, CH3 butyl), 1.28–1.71 [several m, 32 H, CH2(CH2)nCH3, n
= 2,4], 3.02–3.29 (2 m, 12 H, NCH2) ppm. 13C NMR (100 MHz,
CDCl3): δ = 13.62, 13.64, 13.8 (CH3), 20.0, 22.5, 26.5, 27.5, 29.5,
31.3 [CH2(CH2)nCH3, n = 2,4], 49.49, 49.51, 49.7 (NCH2), 164.1
N,N-Dibutyl-NЈ,NЈ-diethyl-NЈЈ,NЈЈ-bis(2-methoxyethyl)guanidinium
Trifluoromethanesulfonate (12Bk): Prepared from 10B (2.21 g,
3.00 mmol) in CH2Cl2 (25 mL) and bis(2-methoxyethyl)amine
(0.81 g, 0.90 mL, 6.10 mmol); 22 h at reflux temp. Yellow solid
( CN3 ) ppm. MS (CI): m / z ( % ) = 4 5 2 ( 1 00 ) [ c at i o n]+
.
1
(1.02 g, 69% yield), m.p. 57 °C. H NMR (400 MHz, CDCl3): δ =
C30H62F3N3O3S (601.89): calcd. C 59.86, H 10.38, N 6.98; found
C 59.76, H 10.16, N 6.96.
0.91/0.93 (2 t, 3 H each, CH3 butyl), 1.13–1.20 (2 t, 6 H,
NCH2CH3), 1.29–1.63 (several m, 8 H, NCH2CH2CH2CH3), 2.91–
3.74 (several m, 22 H, NCH2 CH3 , NCH2 CH2 CH2 CH3 ,
NCH2CH2OCH3) ppm. 13C NMR (100 MHz, CDCl3): δ = 11.9,
12.2, 13.5, 13.7 (NCH2CH3, NCH2CH2CH2CH3), 19.9, 20.0, 28.6,
29.3 (NCH2CH2CH2CH3), 43.3, 43.4 (NCH2 ethyl), 48.9, 49.0,
4 9 . 3 , 4 9 . 4 ( N C H 2 bu t y l , N C H 2 C H2 O ) , 5 8 . 6 1 , 5 8 . 6 3
(NCH2CH2OCH3), 68.2, 68.4 (NCH2CH2OCH3), 165.2 (CN3)
N,N,NЈ,NЈ,NЈЈ-Pentabutyl-NЈЈ-methylguanidinium Trifluoro-
methanesulfonate (12Ce): Prepared from 10C (1.14 g, 1.30 mmol)
in CH2Cl2 (20 mL) and N-butyl-N-methylamine (0.23 g, 0.30 mL,
1
2.60 mmol); 7 h at reflux temp. Yellow oil (0.33 g, 51% yield). H
NMR (400 MHz, CDCl3): δ = 0.90–0.94 (t, 15 H, CH3 hexyl) 1.22–
1.81 (m, 20 H, CH2CH2CH2CH3), 2.96 (s, 3 H, NCH3), 2.99–3.31
(m, 10 H, NCH2) ppm. 13C NMR (100 MHz, CDCl3): δ = 13.53,
15.56 (CH2CH3), 19.8, 19.9, 20.0 (CH2CH2CH3), 29.3, 29.4, 29.5,
29.7 (CH2CH2CH3), 38.2 (NCH3), 48.9, 49.4, 49.5, 49.6, 52.8
(NCH2), 164.0 (CN3) ppm. MS (CI): m/z (%) = 354 (100)
[cation]+. C23H48F3N3O3S (503.71): calcd. C 54.84, H 9.61, N 8.34;
found C 54.97, H 9.52, N 8.21.
ppm. 19F NMR (376 MHz, CDCl ): δ = –74.6 ppm. IR (KBr): ν
˜
3
= 2962 (m), 2936 (m), 2876 (m), 1544 (s), 1461 (m), 1435 (m), 1271
(vs), 1222 (m), 1150 (s), 1118 (s), 1031 (s) cm–1. MS (CI): m/z (%)
= 344 (100) [cation]+. C20H42F3N3O5S (493.62): calcd. C 48.66, H
8.58, N 8.51; found C 48.33, H 8.50, N 8.52.
N,N,NЈ,NЈ-Tetrabutyl-NЈЈ,NЈЈ-diethylguanidinium Trifluoro-
methanesulfonate (12Ca): Prepared from 10C (2.55 g, 3.00 mmol)
in CH2Cl2 (15 mL) and diethylamine (0.44 g, 0.62 mL, 6.00 mmol);
2 h at reflux temp. An oil was obtained, which solidified over 1 d,
yielding a white solid (0.68 g, 46% yield), m.p. 58 °C. 1H NMR
(400 MHz, CDCl3): δ = 0.93–0.97 (2 t, 12 H, CH3 butyl), 1.24 (t,
6 H, NCH2CH3), 1.31–1.46 (m, 12 H) and 1.64–1.78 (m, 4 H,
CH2CH2CH2CH3), 3.02–3.11 (m, 4 H, NCH2CH3), 3.15–3.44 (m,
8 H, NCH2 butyl) ppm. 13C NMR (100 MHz, CDCl3): δ = 12.8,
13.60, 13.63 (CH3), 20.04, 20.07 (CH2CH2CH2CH3), 29.48, 29.53
(CH2CH2CH2CH3), 43.9 (NCH2 ethyl), 49.4, 49.5 (NCH2 butyl),
163.9 (CN3) ppm. 19F NMR (376 MHz, CDCl3): δ = –74.5 ppm.
N,N,NЈ,NЈ-Tetrabutyl-NЈЈ-cyclohexyl-NЈЈ-methylguanidinium Tri-
fluoromethanesulfonate (12Cf): Prepared from 10C (1.17 g,
2.00 mmol) in CH2Cl2 (20 mL) and N-cyclohexyl-N-methylamine
(0.52 g, 0.60 mL, 4.50 mmol); 12 h at reflux temp. White solid
1
(0.48 g, 46% yield), m.p. 76 °C. H NMR (400 MHz, CDCl3): δ =
0.93–0.97 (overlapping triplets, 12 H, CH2CH3), 1.30–1.71 (m, 16
H, CH2CH2CH2CH3), 1.71–1.99 (m, 10 H, CH2 cy) 2.91 (s, 3 H,
NCH3), 2.99–3.34 (m, 9 H, NCH2, NCH) ppm. 13C NMR
( 1 0 0 M H z , C D C l 3 ) : δ = 1 3 . 0 ( C H 2 C H 3 ) , 1 9 . 9 , 2 0 . 1
(CH2CH2CH2CH3), 24.9, 25.8, 29.36, 29.38, 29.5, 29.51, 31.6 (CH2
cy, CH2CH2CH2CH3), 33.8 (NCH3), 48.9, 49.4, 49.6, 49.7 (NCH2),
61.9 (NCH), 164.5 (CN3) ppm. MS (CI): m/z (%) = 380 (100)
[cation]+. C25H50F3N3O3S (529.35): calcd. C 56.68, H 9.51, N 7.93;
found C 56.39, H 9.42, N 8.05.
IR (KBr): ν = 2962 (s), 2936 (s), 2876 (s), 1539 (vs), 1460 (m), 1270
˜
(vs), 1223 (m), 1150 (s), 1032 (s) cm–1. MS (CI): m/z (%) = 340
(100) [cation]+. C22H46F3N3O3S (489.32): calcd. C 53.96, H 9.47,
N 8.58; found C 53.93, H 9.46, N 8.40.
N,N,NЈ,NЈ-Tetrabutyl-NЈЈ,NЈЈ-tetramethyleneguanidinium Tri-
fluoromethanesulfonate (12Cg): Prepared from 10C (2.55 g,
3.00 mmol) in CH2Cl2 (25 mL) and pyrrolidine (0.43 g, 0.50 mL,
6.1 mmol); 20 h at reflux temp. Yellowish oil (0.66 g, 45% yield).
1H NMR (400 MHz, CDCl3): δ = 0.92 (t, 12 H, CH3), 1.24–1.34
(m, 8 H, CH2CH3), 1.45–1.55 (m, 8 H, CH2CH2CH3), 2.05 (broad
signal, 4 H, 3-H2-, 4-H2 ring), 3.11–3.15 (m, 8 H, NCH2 butyl),
3.41 (broad signal, 4 H, NCH2 ring) ppm. 13C NMR (100 MHz,
CDCl3): δ = 13.6 (CH3), 19.9 (CH2CH3), 24.8 (NCH2CH2 ring),
29.4 (CH2CH2CH3), 49.4, 50.9 (NCH2), 120.9 (q, 1JC,F = 320.9 Hz,
CF3), 160.2 (CN3) ppm. MS (CI): m/z (%) = 338 (100) [cation]+.
C22H44F3N3O3S (487.66): calcd. C 54.18, H 9.09, N 8.62; found C
54.64, H 9.10, N 8.72.
N,N,NЈ,NЈ-Tetrabutyl-NЈЈ,NЈЈ-dipropylguanidinium Trifluoro-
methanesulfonate (12Cb): Prepared from 10C (1.70 g, 2.00 mmol)
in CH2Cl2 (20 mL) and di-n-propylamine (0.41 g, 0.56 mL,
4.10 mmol); 3 h at reflux temp. White solid (0.48 g, 46% yield),
1
m.p. 64 °C. H NMR (400 MHz, CDCl3): δ = 0.89–0.98 (m, 18 H,
CH3), 1.25–1.35 (m, 14 H) and 1.68–1.86 [m, 6 H, CH2(CH2)nCH3,
n = 1,2], 2.97–3.25 (m, 6 H, NCH2), 3.25–3.34 (m, 6 H, NCH2)
ppm. 13C NMR (100 MHz, CDCl3): δ = 11.2, 13.6, 13.7 (CH3),
20.4, 20.8 (CH2CH3), 29.4, 29.6 (CH2CH2CH2CH3), 49.4, 49.5,
51.4 (NCH2), 164.2 (CN3) ppm. MS (CI): m/z (%) = 368 (100)
[cation]+. C24H50F3N3O3S (517.73): calcd. C 55.68, H 9.73, N 8.12;
found C 56.02, H 9.89, N 8.23.
N,N,NЈ,NЈ,NЈЈ,NЈЈ-Hexabutylguanidinium Trifluoromethanesulfon-
ate (12Cc): Prepared from 10C (1.69 g, 2.00 mmol) in CH2Cl2
(20 mL) and dibutylamine (0.51 g, 0.67 mL, 4.00 mmol). Colorless
N-Benzyl-NЈ,NЈ,NЈЈ,NЈЈ-tetrabutyl-N-ethylguanidinium Trifluoro-
methanesulfonate (12Ch): Prepared from 10C (1.70 g, 2.00 mmol)
in CH2Cl2 (25 mL) and N-benzyl-N-ethylamine (0.55 g, 0.61 mL,
Eur. J. Org. Chem. 2007, 3746–3757
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3755

H. Kunkel, G. Maas
FULL PAPER
4.10 mmol); 48 h at reflux temp. Yellowish solid (0.49 g, 44% yield),
periments were performed using two different Perkin–Elmer DSC
m.p. 87 °C. 1H NMR (400 MHz, CDCl3): δ = 0.94–0.99 (several t, 6 7 systems. For measurements below room temperature down to
H, CH3 butyl), 1.25–1.77 [several m, 19 H, NCH2CH3, CH2(CH2)2-
CH3], 2.80–3.43 (several m, 10 H, 5 NCH2), 4.28/4.43 (AB system,
–140 °C, an instrument with helium cooling was used. For the tem-
perature range between –70 and +120 °C, one with nitrogen cooling
J = 14.0 Hz, 2 H, NCH2Ph), 7.17–7.20 (m, 2 H, Ar-H), 7.38–7.40 was used. The heating and cooling rates for both were 10 °Cmin–1.
(m, 3 H, Ar-H) ppm. 13C NMR (100 MHz, CDCl3): δ = 12.8,
13.62, 13.65, 13.67 (butyl-CH3, CH2CH3), 19.9, 20.01, 20.05, 20.17, defined as peak maxima. Temperature calibration was performed
29.4, 29.5, 29.8 (NCH2CH2CH2CH3), 44.6 (NCH2 ethyl), 49.0, on a sample of indium. The thermal stability of the salts was deter-
Glass transition temperatures (Tg) and melting points (Tm) were
49.5, 49.6, 53.1 (NCH2 butyl, NCH2Ph), 128.5, 129.1, 129.3, 133.7 mined by thermogravimetric analysis using a Mettler–Toledo TGA/
(Ar-C), 163.7 (CN3) ppm. MS (CI): m/z (%) = 402 (100) [cation]+.
C27H48F3N3O3S (551.75): calcd. C 58.77, H 8.77, N 7.62; found C
58.64, H 8.72, N 7.49.
SDTA 851 instrument. In each experiment, the sample was heated
under a N2 atmosphere, and the temperature was linearly increased
in steps of 10 °Cmin–1 from 30 °C to 800 °C.
N,N,NЈ,NЈ-Tetrabutyl-NЈЈ,NЈЈ-bis(2-methoxyethyl)guanidinium Tri-
fluoromethanesulfonate (12Ci): Prepared from 10C (2.55 g,
3.00 mmol) in CH2Cl2 (25 mL) and bis(2-methoxyethyl)amine
(0.81 g, 0.90 mL, 6.10 mmol); 48 h at reflux temp. Yellowish solid
(1.12 g, 68% yield), m.p. 80 °C. 1H NMR (400 MHz, CDCl3): δ
= 0.91–0.93 (2 t, 12 H, butyl-CH3), 1.26–1.67 (several m, 16 H,
NCH2CH2CH2CH3), 2.89–3.70 (16 H NCH2CH2CH2CH3,
NCH2CH2OCH3), 3.27 (s, 6 H, OCH3) ppm. 13C NMR (100 MHz,
CDCl3): δ = 13.5, 13.6 (NCH2CH2CH2CH3), 19.89, 19.93, 28.7,
Refractive Index Data: Refractive indices were determined using an
Abbé refractometer Type G. The instrument was calibrated by mea-
suring the refractive index of some common organic solvents. Each
sample was dried at 50 °C/0.001 mbar for 3 h. All measurements
were performed at 20Ϯ1 °C.
Viscosity: The viscosity of RTILs was measured with a Haake Mars
II modular advanced rheometer system (Thermo Electron Corpo-
ration). All measurements were performed at 23Ϯ0.01 °C on sam-
ples that had been dried at 70 °C/15–30 mbar for 4–5 h. For each
analysis, a 2–3 mL sample was used, and the tests were carried
out with a 60 mm titanium plate. The analyses were performed in
controlled rate (CR) mode with a shear rate of 10 s–1 and 100 s–1,
but also in CR mode with a starting shear rate of 10 s–1 up to a
shear rate of 150 s–1. In accordance with these results, the zero
shear viscosity was fixed. The temperature-dependent experiments
were performed with a constant shear rate of 10 s–1 in the tempera-
ture range 20–60 °C.
29.3 (NCH2CH2CH2CH3), 48.9, 49.1 (NCH2, NCH2CH2O), 58.6
1
(NCH2CH2OCH3), 68.0 (NCH2CH2OCH3), 120.9 (q, JC,F
=
320.9 Hz, CF3), 165.3 (CN3) ppm. 19F NMR (376 MHz, CDCl3):
δ = –74.6 ppm. IR (KBr): ν = 2961 (s), 2933 (s), 2875 (s), 1539 (s),
˜
1459 (m), 1436 (m), 1263 (vs), 1224 (m), 1150 (s), 1118 (s), 1031
(s) cm–1. MS (CI): m/z (%) = 400 (100) [cation]+. C24H50F3N3O5S
(549.73): calcd. C 52.44, H 9.17, N 7.64; found C 52.95, H 9.14, N
7.65.
One-Pot Synthesis of 12Ac: In a 50 mL Schlenk vessel purged with
argon was placed triflic anhydride (1.41 g, 0.82 mL, 5.0 mmol) and
dry CH2Cl2 (15 mL). The solution was cooled to 0 °C, and N,N-
diethyl-NЈ,NЈ-dimethylurea (8A, 1.44 g, 10 mmol) in CH2Cl2
(10 mL) was added dropwise. After the addition was complete, the
reaction mixture was kept at 0 °C for 30 min with magnetic stirring,
brought to room temp. and finally heated at reflux for 12 h. After
cooling to room temp., a solution of a dibutylamine (1.29 g,
1.70 mL, 10.0 mmol) in CH2Cl2 (10 mL) was added. After the ad-
dition was complete, the mixture was heated at reflux for 5 h. After
cooling to room temp. the solution was concentrated, and pentane
(10 mL) was added. A second liquid (oily) phase formed, which
was separated, dissolved in CH2Cl2 (10 mL), and extracted with
0.1  NaOH, and the organic phase was dried with Na2SO4. After
evaporation of the solvent, a yellow oil was obtained, which was
kept at 0.001 mbar for 5 h to eliminate the remaining traces of vola-
tiles. Yield: 1.13 g (56%).
Acknowledgments
This work was supported financially by the Bundesministerium für
Forschung und Technologie (BMBF). We thank Prof. Dr. Willi
Kantlehner (Hochschule Aalen and Universität Stuttgart) for the
tetraalkylureas used in this study. We also thank Elvira Kal-
tenecker-Zeisberger (Institut für Anorganische Chemie II, Uni-
versität Ulm) for the DSC/TGA measurements.
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a yellow oil, which was kept at 0.001 mbar for 5 h to remove the
remaining traces of volatiles; yield: 0.91 g (45%).
Thermal Analysis: The thermal behavior of the salts was charac-
terized by differential scanning calorimetry (DSC). The DSC ex-
3756
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© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2007, 3746–3757

Hexaalkylguanidinium Trifluoromethanesulfonates
FULL PAPER
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Received: April 4, 2007
Published Online: June 18, 2007
Eur. J. Org. Chem. 2007, 3746–3757
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
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