Functionalised ionic liquids: Synthesis of ionic liquids with tethered basic groups and their use in Heck and Knoevenagel reactions

Article abstract of DOI:10.1039/b9nj00729f

A simple and efficient synthesis of a novel series of ionic liquids bearing nucleophilic (Me₂N) and non-nucleophilic base (ⁱPr ₂N) functionalities is described. The non-nucleophilic base functionality resembles the structure of the Huenig's base (N,N-diisopropylethylamine), which has been used widely in organic synthesis. A qualitative measure of the basicity of these ionic liquids is presented by utilising their interaction with universal indicator. The basicity of these ionic liquids was found to be dependent on the amine tether and choice of linker between the two nitrogen centres. The relative base strength of these ionic liquids was also probed by using them as catalysts in the Heck and Knoevenagel reactions. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

Full text of DOI:10.1039/b9nj00729f

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PAPER
www.rsc.org/njc | New Journal of Chemistry
Functionalised ionic liquids: synthesis of ionic liquids with tethered
basic groups and their use in Heck and Knoevenagel reactions
¨
Stewart A. Forsyth, Ute Frohlich, Peter Goodrich, H. Q. Nimal Gunaratne,
Christopher Hardacre,* Angela McKeown and Kenneth R. Seddon*
Received (in Montpellier, France) 2nd December 2009, Accepted 20th January 2010
First published as an Advance Article on the web 12th February 2010
DOI: 10.1039/b9nj00729f
A simple and efficient synthesis of a novel series of ionic liquids bearing nucleophilic (Me2N) and
non-nucleophilic base (iPr2N) functionalities is described. The non-nucleophilic base functionality
resembles the structure of the Hunig’s base (N,N-diisopropylethylamine), which has been used
widely in organic synthesis. A qualitative measure of the basicity of these ionic liquids is
presented by utilising their interaction with universal indicator. The basicity of these ionic liquids
was found to be dependent on the amine tether and choice of linker between the two nitrogen
centres. The relative base strength of these ionic liquids was also probed by using them as
catalysts in the Heck and Knoevenagel reactions.
to a range of cations by Nockemann et al. designed for the
Introduction
solubilisation of metal oxides and hydroxides.14 Basic groups
have also been tethered to ionic liquids. Davis et al. described
the synthesis of an imidazolium tetrafluoroborate with an
amine group in the cation side chain.3 Developed for gas
separation, the amine-tethered ionic liquid is able to capture
carbon dioxide by carbamate formation.4 A range of nitrile
functionalised ionic liquids have been synthesised and charac-
terised and have been utilised in Heck, Suzuki and Stille
coupling reactions as well as shown to be capable of forming
charge transfer complexes.15 Guanidine-based ionic liquids
have also been developed and employed as base catalysts for
the aldol condensation,16 Henry17 and Knoevenagel reactions.18
Furthermore, asymmetric aldol condensations have been
performed with L-proline tagged imidazolium-based ionic
liquids giving >99% ee.19
Recently, there has been considerable interest in using room
temperature ionic liquids as environmentally benign reaction
media. There are numerous examples of all classes of organic
reactions that have been successfully carried out in such
media.1 However, in many of these reactions, the ionic liquids
were just a media to facilitate the reaction. Ionic liquids are
often referred to as designer solvents2 due to the fact that
choice of combination of anion, cation and cation chain length
can be used to obtain specific properties such as viscosity,
solubility or melting point. The concept of functional ionic
liquids extends this idea by covalently tethering a functional
group to the cation or anion which can interact with dissolved
substrates.3
Functionalised ionic liquids (previously referred to as task
specific ionic liquids) have been used in an analogous way
to supported (polymer, silica or other solids) reagents and
catalysts.4 Although the latter have been in use in organic
synthesis for a number of years, and provide a simplified
procedure for isolation of products from a reaction mixture,
mass transport within a solid can often result in decreased
reaction rates. This effect would be much reduced in the case
of a ‘liquid-support’ by using ionic liquid-supported reagents.
This could be achieved where one of the reactants is an integral
part of the ionic liquid.5–8 This methodological approach in
organic synthesis has been the subject of a recent review.9
Functionalisation of ionic liquids with acidic groups has
been reported. The zwitterionic imidazolium compounds
originally developed by Yoshizawa et al. for electrochemical
purposes10 have been converted into the Brønsted-acidic ionic
liquids and have been shown to act as effective solvent
catalysts for the Fischer esterification,11 the esterification of
aliphatic acids with alkenes12 and the oligomerisation of
alkenes.13 More recently, carboxylic acids have been attached
A range of hydrophobic functionalised ionic liquids de-
signed to aid the extraction of mercury(II) and cadmium(II)
from water have been reported by Rogers and co-workers.20
These were prepared by appending urea-, thiourea- or
thioether groups to an imidazolium cation. Park et al. have
also synthesised an imidazolium polyoxyethylene-based crown
ether ionic liquid for the selective extraction of the radioactive
strontium(II) from aqueous solutions.21
Herein, we report the synthesis and utility of a new class of
ionic liquids with a tethered base functionality with tuneable
basicity.22 The ionic liquids prepared and characterised utilise
a non-nucleophilic, sterically-hindered tertiary amine func-
tionality which is linked to a quaternary ammonium molecular
segment by an alkyl chain or by a tether containing ethereal
segments of differing lengths.
Results and discussion
The general synthetic strategy for the preparation of
[iPr2N(CH2)2mim][NTf2],
[iPr2N(CH2)2N112][NTf2]
and
[Me2N(CH2)2N112][NTf2] is simple and versatile (see Scheme 1).
The synthetic strategy makes use of the synthesis of a diamine
QUILL, The Queen’s University of Belfast, Belfast, Northern Ireland,
UK BT9 5AG. E-mail: quill@qub.ac.uk
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Scheme
3
Synthesis of [iPr2N(CH2)2O(CH2)2N112][NTf2] and
[iPr2N(CH2)2(OCH2)2N112][NTf2].
An overview of the synthesised basic ionic liquids and their
physical properties is shown in Table 1. All of the materials
synthesised are liquids at room temperature and show rela-
tively low viscosities. The structurally related compounds
[iPr2N(CH2)2mim][NTf2] and [iPr2N(CH2)2N112][NTf2] show
how the type of cationic centre greatly influences the melting
point. The choice of an Me2N group instead of an iPr2N group
in the case of [R2N(CH2)2N112][NTf2] shows how the structure
of the base tether greatly effects the viscosity. A pronounced
decrease in viscosity is also noted between [iPr2N(CH2)2-
O(CH2)2N112][NTf2] and [iPr2N(CH2)2(OCH2CH2)2N112][NTf2]
when increasing linker length between the cationic centre and
tethered amine. This is uncommon for ionic liquids where
increasing the chain length normally leads to an increase in
viscosity.1,23
Scheme 1 Synthesis of [iPr2N(CH2)2mim][NTf2], [iPr2N(CH2)2N112][NTf2]
and [Me2N(CH2)2N112][NTf2].
intermediate where one amine group is readily quaternised
compared with the other. A vital part of the synthesis of the
base-tethered ionic liquids involves the use of 2-diisopropyl-
aminoethyl chloride reacting with a chosen nucleophilic
reagent, which is facilitated by the neighbouring group partici-
pation from the diisopropylamino moiety. The synthesis of an
ionic liquid with an extended linker is not entirely straight-
forward, because long chain haloalkylamines are not commercially
available. These amines can undergo self-alkylation or hydro-
dehalogenation and are, therefore, very difficult to prepare. The
alternative is to start from a longer chain diamine, and carry out
a monoalkylation utilising a large excess of the diamine.
The synthetic strategy for the preparation of [Me2N(CH2)6N112]-
[NTf2] makes use of the insolubility of the mono-quaternised
diamine which precipitates out of the diethyl ether solvent
thereby preventing dialkylation with the haloalkane,
Scheme 2.
The diamines iPr2N(CH2)2O(CH2)2NMe2 and iPr2N(CH2)2-
(OCH2CH2)2NMe2 with five and eight atoms in the chain
connecting the nitrogen centres, respectively, were prepared
as ionic liquid precursors from dimethylaminoethanol with
sodium hydride in a Williamson ether synthesis, Scheme 3.
The diamine iPr2N(CH2)2O(CH2)2NMe2 was prepared in
good yield 89% and high purity (through distillation) after
workup from the reaction between dimethylaminoethanol
and diisopropylaminoethyl chloride hydrochloride. Diamine
iPr2N(CH2)2(OCH2CH2)2NMe2 with a diether functionality
was prepared in a similar manner and also purified by distillation.
Another crucial advantage in using a sterically-hindered amine
tether becomes clear in the subsequent quaternisation reactions.
In the case of both these diamine compounds, the alkylation is
100% selective with only the dimethylamino group reacted due to
the fact that the diisopropylamino group is non-nucleophilic.
Table 2 shows the proton shifts of the methylene groups in
the linker adjacent to the ionic centre (a) and the pendant
amino group (o). The structurally similar compounds
[iPr2N(CH2)2mim][NTf2] and [iPr2N(CH2)2N112][NTf2] show
how the choice of cationic centre greatly influences the
chemical shift of the a-methylene protons, 4.11 and 3.24 ppm,
respectively, as expected from the relative electron densities on
the ammonium and the imidazolium nitrogen centres. Despite
this large change in chemical shift for the a-methylene
protons little change is observed for the corresponding
o-methylene groups adjacent to the diisopropylamino moiety.
i
Similarly, substitution of the Pr2N pendant amino group in
[iPr2N(CH2)2N112][NTf2] with an Me2N resulted in an increase
in chemical shift of the corresponding o methylene protons
from 2.86 to 3.56 ppm due to the increased inductive effect.
Increasing the linker chain length from two to six carbons in
the case of [Me2N(CH2)6N112][NTf2] resulted in a signifi-
cant decrease in o chemical shift from 3.56 to 2.26 ppm. In
contrast, little change in chemical shift was observed for a and
o methylene protons with both the ethereal linker type ionic
liquids [iPr2N(CH2)2O(CH2)2N112][NTf2] and [iPr2N(CH2)2-
(OCH2CH2)2N112][NTf2], however, in both these ionic liquids
the o methylene protons were found to overlap with the
corresponding methylene protons in the linker.
The non-nucleophilicity of the Hunig’s base (iPr2N) unit
was demonstrated by the inability to form complexes with
transition metal ions such as cobalt(II) and copper(II), as seen
by lack of visual colouration. In contrast, the Me2N unit
formed a coloured complex with copper(II), demonstrating
the nucleophilic nature of this amino moiety.
Scheme 2 Synthesis of [Me2N(CH2)6N112][NTf2].
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Table 1 Viscosity and density data at 25 1C and melting point as a function of the type of base-tethered ionic liquid
Ionic liquid
Melting point/1C
Viscosity/cP
Density/g cmꢁ3
[iPr2N(CH2)2mim][NTf2]
33a
ꢁ73
23
ꢁ59
ꢁ77
ꢁ82
417
540
129b
475
389
195
1.354
1.300
1.320b
1.319
1.277
1.247
[iPr2N(CH2)2N112][NTf2]
[Me2N(CH2)2N112][NTf2]
[Me2N(CH2)6N112][NTf2]
[iPr2N(CH2)2O(CH2)2N112][NTf2]
[iPr2N(CH2)2(OCH2CH2)2N112][NTf2]
a
b
Supercooled with a freezing point of ꢁ10 1C. Measured at 35 1C.
showing that the basicity of the ionic liquids studied follows
the trend:
Table 2 Effect of ionic liquid cation structure on the methylene
proton shift for the a and o species
[iPr2N(CH2)2(OCH2CH2)2N112][NTf2] > [iPr2N(CH2)2-
O(CH2)2N112][NTf2] E [Me2N(CH2)6N112][NTf2] >
[iPr2N(CH2)2N112][NTf2] E [iPr2N(CH2)2mim][NTf2]
As well as the basicity of an ionic liquid increasing with the
number of atoms separating the two nitrogen atoms, changing
the separator from an alkyl chain to one containing ether
linkages also increases the basicity of the ionic liquid. In this
case, it is thought that the ether groups stabilise the proto-
nated tethered amine base via an intramolecular hydrogen
bonded complex as shown in Scheme 4.
Ionic liquid
do/ppm
da/ppm
[iPr2N(CH2)2mim][NTf2]
2.78
2.86
3.56
2.26
2.62
2.64
4.11
3.24
3.56
3.37
[iPr2N(CH2)2N112][NTf2]
[Me2N(CH2)2N112][NTf2]
[Me2N(CH2)6N112][NTf2]
[iPr2N(CH2)2O(CH2)2N112][NTf2]
[iPr2N(CH2)2(OCH2CH2)2N112][NTf2]
3.39–3.53a
3.49–3.53a
a
Overlap with the methylene protons in the linker.
The variation in basicity of the ionic liquids for reactions
was examined using the Heck and Knoevenagel reactions,
Scheme 5. The Heck reaction between 2-methylprop-2-en-
1-ol and 4-tert-butyliodobenzene was examined at 95 1C using
The relative base strength of these ionic liquids was
measured using universal indicator.24 It should be noted that
universal indicator is a mixture of acids and bases and that the
ionic liquid competes with the proton with these compounds.
Therefore, the changes are relative and cannot be related to
pKa values. Whilst the change in alkyl chain length in a series
of imidazolium, ammonium, pyrrolidinium and pyridinium
ionic liquids had little effect on the change in polarity,25
a
significant change in the response to the indicator was found
for the ionic liquids reported herein. Fig. 1 shows the electronic
absorption spectra of the universal indicator as a function of
the base-tethered ionic liquid structure. The electronic absorp-
tion spectra give an indication of how the base strength of the
pendant amino group varies with chain length and the type of
chain, alkyl or ethereal, employed. In the spectra, two absorp-
tion bands are observed; one at 400–460 nm corresponding to
the protonated state of indicator dye and one at 620–640 nm
corresponding to the free base form of the dye.26 No signifi-
cant change in the electronic absorption spectra is observed
between the equivalent ammonium and imidazolium ionic
liquids studied, i.e. [iPr2N(CH2)2N112][NTf2] (Fig. 1b) and
[iPr2N(CH2)2mim][NTf2] (Fig. 1c), with both ionic liquids
showing similar spectra to that found for [C4mim][NTf2], see
Fig. 1a. However, in general, with increasing chain length the
proportion of the longer wavelength band increases showing
increasing proton transfer from the dye to the ionic liquid,
Fig. 1d–1f. This can be explained by the fact that when the
tethered amine is protonated, electronic repulsion between two
positive centres within the cation decreases with increasing
chain length leading to a stabilisation of the dication. Further-
more, a solvatochromic shift in the longer wavelength band27
is also observed associated with the type of ionic liquid
Fig. 1 UV/vis spectra of the universal indicator in (a) [C4mim][NTf2],
(b) [iPr2N(CH2)2N112][NTf2], (c) [iPr2N(CH2)2mim][NTf2], (d) [Me2N(CH2)6-
N
112][NTf2], (e) [iPr2N(CH2)2O(CH2)2N112][NTf2] and (f) [iPr2N(CH2)2-
(OCH2CH2)2N112][NTf2].
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the imidazolium ring in [iPr2N(CH2)2mim][NTf2] is much
more acidic than the protons of the methyl or methylene
groups on the ammonium centre. Therefore, as the rest of
the structure is invariant the basicity of the [iPr2N(CH2)2mim]-
[NTf2] ionic liquid is expected to be weaker than that found
for [iPr2N(CH2)2N112][NTf2]. While none of the ionic
liquids tested were more active than free Hunig’s base in
[C4mim][NTf2], both [iPr2N(CH2)2O(CH2)2N112][NTf2] and
[iPr2N(CH2)2(OCH2CH2)2N112][NTf2] did show comparable
reactivity and, importantly, the base-tethered ionic liquid
allowed facile recycle of the base by solvent extraction.29 In
comparison, the workup of the reaction mixture when using the
free Hunig’s base dissolved in [C4mim][NTf2] by extraction or
distillation leads to significant loss of the amine and loss of activity.
A more detailed study of the base catalysed Knoevenagel con-
densation reaction using [iPr2N(CH2)2mim][NTf2], [iPr2N(CH2)2O-
(CH2)2N112][NTf2] and [iPr2N(CH2)2(OCH2CH2)2N112][NTf2]
shows that the relative activities shown for the reaction between
benzaldehyde and ethyl cyanoethanoate are found for a wide
range of substrates.29
Scheme 4 Stabilisation of the tethered protonated tethered amine via
the formation of
a intramolecular hydrogen bonded complex
[iPr2N(CH2)2O(CH2)2N112][NTf2].
palladium(II) ethanoate as the catalyst using [iPr2N(CH2)2mim]-
[NTf2] and [iPr2N(CH2)2O(CH2)2N112][NTf2]. The conversion
to 3-(4-tert-butylphenyl)-2-methylpropanal (b-Lilials) was B32%
after 10 h using [iPr2N(CH2)2mim][NTf2] as the reaction
medium compared with 84% in [iPr2N(CH2)2O(CH2)2N112]-
[NTf2]. These results match the relative basicity of the ionic
liquids using universal indicator. A direct comparison of the
Heck reaction using the free Hunig’s base under solventless
conditions, maintaining the same substrate to base ratio as
used for the ionic liquid systems, showed a conversion of
39% demonstrating the greater catalytic activity of the
functionalised ionic liquids.28 The selectivity between 3-(4-
tert-butylphenyl)-2-methylpropanal and 2-(4-tert-butylphenyl)-
3-methylpropanal (a-Lilials) was found to be >95% with
respect to b-Lilials and was invariant with the basicity of the
ionic liquid-base used.
Conclusions
A versatile synthesis for a series of base-tethered ionic liquids
has been reported which can be used as effective catalysts
for the Heck and the Knoevenagel reactions. By changing
the structure of the cation and length/type of spacer between
the pendant amino group and the cation centre, the basicity
may be varied systematically. Both increasing the spacer
length as well as incorporating ether linkages into the spacer
resulted in higher basicity. This was due to a stabilisation of
the protonated amine via decreased coulombic repulsion and
the formation of intramolecular hydrogen bonded complexes.
Similarly the Knoevenagel reaction was carried out in the
base-tethered ionic liquids and compared with free Hunig’s
base dissolved in [C4mim][NTf2] obtaining near quantitative
yields (Table 3). Interestingly, although [iPr2N(CH2)2mim][NTf2],
[iPr2N(CH2)2N112][NTf2] and [Me2N(CH2)2N112][NTf2] were
too weakly basic to deprotonate the dye present in the
universal indicator, the basicity was sufficient to catalyse the
Knoevenagel reaction, albeit slowly. Again the rate of reaction
was found to follow the basicity of the ionic liquid with
Experimental
All reagents and solvents (ex Aldrich) were used as received
except for 1-methylimidazole which was distilled from calcium
hydride prior to use. 1H- and 13C-NMR spectra were measured
using a Bruker Avance AVX 300 at ambient temperature or a
Bruker Avance DRX 500 spectrometer at 27 1C. All samples
were run with tetramethylsilane added as an internal standard.
The phase transition temperatures were determined by DSC
measurements with a Perkin-Elmer Pyris 1 DSC equipped with
a liquid nitrogen cryostatic cooler. The heating and cooling
rates were both 10 1C minꢁ1 and the melting point and glass
[iPr2N(CH2)2mim][NTf2]
o
o
[iPr2N(CH2)2N112][NTf2]
o
o
[Me2N(CH2)2N112][NTf2]
[Me2N(CH2)6N112][NTf2]
[iPr2N(CH2)2O(CH2)2N112][NTf2] o [iPr2N(CH2)2(OCH2CH2)2-
N
112][NTf2]. Importantly, although the universal indicator
shows the general trends, the Knoevenagel reaction is a more
sensitive probe of the basicity and shows that [iPr2N(CH2)2mim]-
[NTf2] is less basic than [iPr2N(CH2)2N112][NTf2], for example.
This may be understood as the proton at the C(2) position on
Table 3 Comparison of the conversion for the Knoevenagel reaction
between benzaldehyde and ethyl cyanoacetate at room temperature
under homogeneous reaction conditions as a function of the ionic
liquid catalyst used at 10 mol% with respect to carbonyl compound
Ionic liquid catalyst
Time
% Conversion
[C4mim][NTf2]/Hunig’s base
[iPr2N(CH2)2mim][NTf2]
20 min
24 h
100
12
50
63
87
82
91
[iPr2N(CH2)2N112][NTf2]
[Me2N(CH2)2N112][NTf2]
60 min
60 min
60 min
20 min
20 min
[Me2N(CH2)6N112][NTf2]
[iPr2N(CH2)2O(CH2)2N112][NTf2]
[iPr2N(CH2)2(OCH2)2N112][NTf2]
Scheme 5 Homogeneous Heck coupling and Knoevenagel conden-
sations carried out in the base-tethered ionic liquids.
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transitions are defined as peak maxima. Calibration of the
DSC was carried out with iridium samples. Mass spectro-
metry was carried out on a Micromass Autopsec X Series
spectrometer. Microanalyses were carried out by A.S.E.P.
(The Queen’s University of Belfast) on a Perkin Elmer
Series II CHNS/O Analyzer 2400. The densities were measured
using an Anton Paar DMA density meter and the visco-
sities measured using a Brookfield DV-II+ cone and plate
viscometer. GC analysis was conducted on an Agilent 1320
using a RTX-5 (5% diphenyl–95% dimethyl polysiloxane)
column.
1-(2-Diisopropylaminoethyl)-3-methylimidazolium bis{(trifluoro-
methyl)sulfonyl}amide ([iPr2N(CH2)2mim][NTf2]). 1-(2-Diiso-
propylaminoethyl)-3-methylimidazolium chloride (7.58 g,
30.84 mmol) was dissolved in dichloromethane (50 cm3)
and a solution of lithium bis{(trifluoromethyl)sulfonyl}amide
(9.71 g, 33.92 mmol) in water (10 cm3) was added. The organic
phase was washed with water (6 ꢂ 15 cm3) and the solvent was
removed in vacuo at 40 1C. The ionic liquid was then dried
overnight at 65 1C under high vacuum to obtain a colourless
liquid (14.19 g, 29.0 mmol, 94% yield).
Mp (DSC): 33 1C (supercooled, glass transition at ꢁ61 1C).
1H-NMR (300 MHz, d-trichloromethane): d/ppm = 0.88 (d,
J = 6.6 Hz, 12H, iPr-CH3); 2.78 (t, J = 5.6 Hz, 2H, N-CH2);
2.98 (q, J = 6.7 Hz, 2H, iPr-CH); 3.92 (s, 3H, N+-CH3); 4.11
(t, J = 5.6 Hz, 2H, N+-CH2); 7.29 (t, J = 1.8 Hz, 1H), 7.37
(t, J = 1.7 Hz, 1H) (4-H and 5-H); 8.62 (s, 1H, 2-H).
13C-NMR (75 MHz, d-trichloromethane): d/ppm = 20.52
(iPr-CH3); 36.20 (N-CH3); 44.98, 47.86, 49.83 (NCH2 and
NCH); 118.89 (q, JCF = 320 Hz, CF3), 122.95, 123.35 (C4
and C5); 136.32 (C2). Elemental analysis % calc. (% found): C
34.28 (34.37), H 4.93 (4.75), N 11.42 (11.17). MS FAB+ m/z
(% rel. intensity): 128 [iPr2NEt]+ (100), 210 [iPr2N(CH2)2mim]+
(68), 700 [(iPr2N(CH2)2mim)2NTf2]+ (o1). Viscosity at 25 1C:
Synthesis of the ionic liquids
1-Butyl-3-methylimidazolium bromide. 1-Methylimidazole
(20.50 g, 0.25 mol) and 1-bromobutane (41.10 g, 0.3 mol)
were heated under reflux for 24 h. The reaction mixture was
washed with cold dry propanone (3 ꢂ 50 cm3) and the solvent
was removed in vacuo at 50 1C and further dried overnight
at 65 1C under high vacuum yielding a white solid (50.37 g,
0.23 mmol, 93% yield).
1H-NMR (300 MHz, d3-ethanenitrile): d/ppm = 0.89 (t, J =
7.3 Hz, 3H, Bu-CH3); 1.28 (sextet, J = 7.5 Hz, 2H, CH2); 1.80
(p, J = 7.4 Hz, 2H, CH2); 3.91 (s, 3H, N+-CH3); 4.20 (q, J =
7.2 Hz, 2H, N-CH2); 7.45 (t, J = 1.8 Hz, 1H), 7.53 (t, J =
1.7 Hz, 1H) (4-H and 5-H); 9.38 (s, 1H, 2-H).
417 cP. Density at 25 1C: 1.354 g cmꢁ3
.
1-(2-Diisopropylaminoethyl)dimethylethylammonium chloride.
Dimethylethylamine (3.51 g, 48.0 mmol) and 2-diisopropyl-
aminoethyl chloride hydrochloride (10.06 g, 50.3 mmol)
were dissolved in ethanenitrile (50 cm3) and sodium carbonate
(14.0 g, 132.1 mmol) was added. After heating under reflux for
24 h the mixture was filtered through Celite. The solvent was
removed in vacuo at 50 1C and the residue was washed with
diethyl ether (50 cm3) and recrystallised from ethanenitrile
(10 cm3). After drying overnight under high vacuum at 60 1C a
white solid was obtained (11.16 g, 46.9 mmol, 98% yield).
1H-NMR (300 MHz, d3-ethanenitrile): d/ppm = 0.97 (d, J =
1-Butyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}-
amide ([C4mim][NTf2]). 1-Butyl-3-methylimidazolium bromide
(50.37 g, 0.23 mol) was dissolved in dichloromethane (100 cm3)
and a solution of lithium bis{(trifluoromethyl)sulfonyl}amide
(73.12 g, 0.253 mol) in water (100 cm3) was added. The organic
phase was washed with water (6 ꢂ 100 cm3) and the organic
solvent was removed in vacuo at 40 1C. The ionic liquid was
then dried overnight at 65 1C under high vacuum to obtain as
a colourless liquid (92.50 g, 0.22 mol, 96% yield).
1H-NMR (300 MHz, d3-ethanenitrile): d/ppm = 0.90 (t, J =
7.3 Hz, 3H, Bu-CH3); 1.29 (sextet, J = 7.5 Hz, 2H, CH2); 1.77
(p, J = 7.3 Hz, 2H, CH2); 3.84 (s, 3H, N+-CH3); 4.11 (q, J =
7.2 Hz, 2H, N-CH2); 7.35 (t, J = 1.8 Hz, 1H), 7.39 (t, J =
1.7 Hz, 1H) (4-H and 5-H); 8.44 (s, 1H, 2-H).
i
7.1 Hz, 12H, Pr-CH3); 1.37 (t, J = 7.2 Hz, 3H, Et-CH3); 2.87
(t, J = 6.9 Hz, 2H, N-CH2); 3.03 (q, J = 7.1 Hz, 2H, iPr-CH);
3.14 (s, 6H, N+-CH3); 3.26 (t, J = 6.7 Hz, 2H, N+-CH2); 3.39
(q, J = 7.1 Hz, 2H, CH2-Me).
1-(2-Diisopropylaminoethyl)dimethylethylammonium bis{(tri-
fluoromethyl)sulfonyl}amide ([iPr2N(CH2)2N112][NTf2]). 1-(2-
Diisopropylaminoethyl)dimethylethylammonium chloride (7.68 g,
32.3 mmol) was dissolved in dichloromethane (50 cm3) and
1-(2-Diisopropylaminoethyl)-3-methylimidazolium chloride.
1-Methylimidazole (3.99 g, 48.6 mmol) and 2-diisopropyl-
aminoethyl chloride hydrochloride (10.21 g, 51.0 mmol) were
dissolved in ethanenitrile (50 cm3) and sodium carbonate
(14.00 g, 132.1 mmol) was added. After heating under reflux
for 24 h the mixture was filtered through Celite. The solvent
was removed in vacuo at 50 1C and the residue was washed
with diethyl ether (30 cm3) and recrystallised from ethane-
nitrile (10 cm3). After drying under high vacuum a white solid
was obtained (11.62 g, 47.3 mmol, 97% yield).
a
solution of lithium bis{(trifluoromethyl)sulfonyl}amide
(9.71 g, 33.9 mmol) in water (10 cm3) was added. The organic
phase was washed with water (6 ꢂ 15 cm3) and the solvent was
removed in vacuo at 40 1C. The ionic liquid was then dried
overnight at 65 1C under high vacuum to obtain a colourless
liquid (14.66 g, 30.4 mmol, 94% yield).
Mp (DSC): ꢁ73 1C. 1H-NMR (300 MHz, d-trichloro-
i
methane): d/ppm = 0.99 (d, J = 7.2 Hz, 12H, Pr-CH3);
1.38 (t, J = 7.3 Hz, 3H, Et-CH3); 2.86 (t, J = 7.0 Hz, 2H,
1H-NMR (300 MHz, d3-ethanenitrile): d/ppm = 0.89
i
(d, J = 6.6 Hz, 12H, Pr-CH3); 2.81 (t, J = 5.6 Hz, 2H,
i
N-CH2); 3.01 (q, J = 7.1 Hz, 2H, Pr-CH); 3.11 (s, 6H, N+-
i
N-CH2); 3.02 (q, J = 6.6 Hz, 2H, Pr-CH); 3.91 (s, 3H,
CH3); 3.24 (t, J = 6.5 Hz, 2H, N+-CH2); 3.39 (q, J = 7.2 Hz,
2H, CH2-Me). 13C-NMR (75 MHz, d-trichloromethane):
d/ppm = 20.52 (iPr-CH3); 36.20 (N-CH3); 44.98, 47.86,
49.83 (NCH2 and NCH); 119.88 (q, JCF = 320 Hz, CF3),
N+-CH3); 4.16 (t, J = 5.7 Hz, 2H, N+-CH2); 7.45 (t, J =
1.8 Hz, 1H), 7.53 (t, J = 1.7 Hz, 1H) (4-H and 5-H); 9.38
(s, 1H, 2-H).
ꢀc
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122.95, 123.35 (C4 and C5); 136.32 (C2). Elemental analysis %
calc. (% found): C 34.92 (34.94), H 6.07 (6.06), N 8.73 (8.76).
MS FAB+ m/z (% rel. intensity): 128 [iPr2NEt]+ (100), 201
(m, 2H, N+-CH2CH2); 2.12 (s, 6H, N-CH3); 2.16 (t, J =
7.3 Hz, 2H, N-CH2); 3.27 (s, 6H, N+-CH3); 3.39–3.52 (m, 2H,
N+-CH2CH3), 3.61 (q, J = 7.2 Hz, 2H, N+-CH2CH2).
[iPr2N(CH2)2N112
]
+ (19), 682 [(iPr2N(CH2)2N112)2NTf2]+ (o1).
Viscosity at 25 1C: 540 cP. Density at 25 1C: 1.300 g cmꢁ3
.
1-(6-Dimethylaminohexyl)dimethylethylammonium bis{(tri-
fluoromethyl)sulfonyl}amide ([Me2N(CH2)6N112][NTf2]). 1-(6-
Dimethylaminohexyl)dimethylethylammonium iodide (4.67 g,
12.2 mmol) was dissolved in dichloromethane (50 cm3) and a
solution of lithium bis{(trifluoromethyl)sulfonyl}amide (3.85 g,
13.4 mmol) in water (10 cm3) was added. The organic phase
was washed with water (5 ꢂ 10 cm3), dried with sodium sulfate
(2 g) and the solvent was removed in vacuo at 40 1C. The ionic
liquid was then dried overnight at 65 1C under high vacuum to
obtain a pale yellow liquid (5.28 g, 11.0 mmol, 90% yield).
Mp (DSC): ꢁ59 1C. 1H-NMR (300 MHz, d-trichloromethane):
d/ppm = 1.27–1.55 (m, 9H, g,d,e-CH2 and N+-CH2CH3);
1.62–1.80 (m, 2H, N+-CH2CH2); 2.22 (s, 6H, N-CH3); 2.26
(t, J = 7.3 Hz, 2H, N-CH2); 3.02 (s, 6H, N+-CH3); 3.15–3.26
(m, 2H, N+-CH2CH3), 3.37 (q, J = 7.3 Hz, 2H, N+-CH2CH2).
13C-NMR (75 MHz, d-trichloromethane): d/ppm = 8.22
(Et-CH3); 22.61, 26.00, 26.83, 27.33 (b,g,d,e-CH2); 45.49
(N-CH3); 50.46 (N-CH2); 59.41 (N+-CH3); 60.03 (N+-CH2CH3);
64.15 (N+-CH2CH2); 119.93 (q, JCF = 321 Hz, CF3). Elemental
analysis % calc. (% found): C 34.92 (32.35), H 6.07 (5.54), N
1-(2-Dimethylaminoethyl)dimethylethylammonium chloride.
2-(Dimethylaminoethyl) chloride hydrochloride (14.4 g,
0.1 mol) and dimethylethylamine (24.9 g, 0.3 mol) were
dissolved in ethanenitrile (100 cm3) and sodium carbonate
(21.6 g, 0.20 mol) was added. After heating under reflux for
24 h the mixture was filtered through Celite. The solvent was
removed in vacuo at 50 1C and the residue was washed with
diethyl ether (70 cm3) and recrystallised from ethane-
nitrile (10 cm3). After drying overnight at 60 1C under
high vacuum, a white solid was obtained (16.96 g, 94.0 mmol,
94% yield).
1H-NMR (300 MHz, d3-ethanenitrile): d/ppm = 1.32
(m, 3H, CH2-CH3); 2.26 (s, 6H, N-CH3); 2.67 (m, 2H,
CH2-CH3); 3.18 (s, 6H, N+-CH3); 3.55 (m, 4H, N+-CH2CH2N).
1-(2-Dimethylaminoethyl)dimethylethylammonium bis{(tri-
fluoromethyl)sulfonyl}amide ([Me2N(CH2)2N112][NTf2]). 1-(2-
Dimethylaminoethyl)dimethylethylammonium chloride (6.50 g,
36.0 mmol) was dissolved in dichloromethane (50 cm3) and a
solution of lithium bis{(trifluoromethyl)sulfonyl}amide (11.26 g,
39.3 mmol) in water (40 cm3) was added. The organic phase
was washed with water (6 ꢂ 15 cm3) and the solvent was
removed in vacuo at 40 1C. The ionic liquid was then dried
overnight at 65 1C under high vacuum to obtain a colourless
liquid (14.39 g, 33.9 mmol, 94% yield).
Mp (DSC): 23 1C. 1H-NMR (300 MHz, d-trichloro-
methane): d/ppm = 1.34 (m, 3H, CH2-CH3); 2.26 (s, 6H,
N-CH3); 2.69 (m, 2H, CH2-CH3); 3.20 (s, 6H, N+-CH3); 3.56
(m, 4H, N+-CH2CH2N). 13C-NMR (75 MHz, d-trichloro-
methane): d/ppm = 8.23 (Et-CH3); 45.62 (N-CH3); 51.46
(N-CH2); 53.21 (N+-CH3); 60.89 (N+-CH2CH3); 61.76
(N+-CH2CH2); 119.93 (q, JCF = 321 Hz, CF3). Elemental
analysis % calc. (% found): C 28.24 (28.65), H 4.94 (4.81),
8.73 (8.07). MS ES+ m/z (% rel. intensity): 128 [Me2N(CH2)6]+
+
(37), 201 [Me2N(CH2)6N112]
(100). MS ESꢁ m/z (% rel.
intensity): 147 [NTfꢁ] (9), 280 [NTf2ꢁ] (100). Viscosity at
25 1C: 475 cP. Density at 25 1C: 1.319 g cmꢁ3
.
(5-Diisopropylamino-3-oxapentyl)dimethylamine. Into a solu-
tion of 2-dimethylaminoethanol (19.61 g, 220 mmol) in dry
tetrahydrofuran (100 cm3) at 0 1C was added sodium hydride
(60% dispersion in mineral oil, 10.0 g, 250 mmol) under a
dinitrogen atmosphere. After stirring for 10 min at 0 1C 2-diiso-
propylaminoethyl chloride hydrochloride (20.0 g, 100 mmol) was
added slowly. The reaction mixture was heated under reflux for
4 h and then quenched by dropwise addition of water (20 cm3) at
0 1C. After evaporation of tetrahydrofuran in vacuo at 50 1C, the
reaction mixture was diluted with water (30 cm3) and extracted
with dichloromethane (3 ꢂ 50 cm3). The combined organic
extracts were dried with sodium sulfate (5 g) and the solvent
was removed in vacuo at 40 1C. The crude product was purified
by Kugelrohr distillation; 19.19 g (89 mmol, 89% yield) of a
colourless liquid were obtained.
N
9.88 (9.37). MS FAB+ m/z (% rel. intensity): 72
+
[Me2N(CH2)2]+ (29), 145 [Me2N(CH2)2N112
]
(100). ꢁMS ESꢁ
m/z (% rel. intensity): 147 [NTfꢁ] (11), 280 [NTf2 ] (100).
Viscosity at 35 1C: 129 cP. Density at 35 1C: 1.320 g cmꢁ3
.
1H-NMR (300 MHz, d-trichloromethane): d/ppm = 1.00
i
(d, J = 6.6 Hz, 12H, Pr-CH3); 2.27 (s, 6H, NCH3); 2.49
1-(6-Dimethylaminohexyl)dimethylethylammonium iodide.
N,N,N0,N0-Tetramethyl-1,6-hexanediamine (17.89 g, 103.8 mmol)
was dissolved in diethyl ether (400 cm3) and iodoethane (16.19 g,
103.8 mmol) was added dropwise. The solution was stirred in
the dark at room temperature for two days, during which the
formation of a white precipitate was observed. The precipitate
was collected by filtration, washed with diethyl ether (50 cm3)
and dried under high vacuum. It then was suspended in
trichloromethane (200 cm3) and filtered again to remove traces
of the dialkylated side product. The filtrate contained only
monoalkylated product. After drying under high vacuum at
60 1C, an off-white powder was obtained (8.94 g, 27.2 mmol,
26% yield).
(t, J = 5.8 Hz, 2H, NCH2); 2.62 (t, J = 7.6 Hz, 2H, NCH2);
i
2.98 (t, J = 6.5 Hz, 2H, Pr-CH); 3.39 (t, J = 8.0 Hz, 2H,
OCH2); 3.54 (t, J = 5.8 Hz, 2H, OCH2). 13C-NMR (75 MHz,
d-trichloromethane): d/ppm = 20.81 (iPr-CH3); 44.79 (NCH2);
46.1 (NCH3); 49.54 (NCH2); 50.06 (Me2NCH2); 69.28, 72.88
(OCH2). MS EI+ m/z (% rel. intensity): 149 [iPr2NCH2CH2O-
CH2CH2NH2 + H2O] (100); 188 [iPr2NCH2CH2OCH2CH] (53);
215 [M+ ꢁ H] (52).
(5-Diisopropylamino-3-oxapentyl)dimethylethylammonium
bromide.
(5-Diisopropylamino-3-oxapentyl)dimethylamine
(14.85 g, 68.6 mmol) was heated under reflux with bromo-
ethane (18.35 g, 0.172 mol) in ethanenitrile (20 cm3) for 30 h.
After evaporation of the solvent and excess bromoethane
1H-NMR (300 MHz, d-trichloromethane): d/ppm
=
1.20–1.46 (m, 9H, g,d,e-CH2 and N+-CH2CH3); 1.59–1.75
ꢀc
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in vacuo at 60 1C, the product was recrystallised from ethane-
nitrile (10 cm3). After filtration and drying under high vacuum
a pale yellow powder was obtained (19.87 g, 61.1 mmol, 89%
yield).
1H-NMR (300 MHz, d4-methanol): d/ppm = 1.04 (d, J =
6.6 Hz, 12H, iPr-CH3); 1.38 (t, J = 7.2 Hz, 3H, Et-CH3); 2.67
(t, J = 6.7 Hz, 2H, N-CH2); 3.04 (p, J = 6.6 Hz, 2H, iPr-CH);
3.15 (s, 6H, N+-CH3); 3.42–3.61 (m, 6H, O-CH2 and N+-CH2)
3.83–3.93 (m, 2H, O-CH2).
(t, J = 2.6 Hz, 2H, OCH2); 3.64 (t, J = 4.8 Hz, 2H, OCH2);
3.66–3.68 (m, 4H, OCH2CH2O)
Ethyl(8-diisopropylamino-3,6-dioxaoctyl)dimethylammonium
bromide. (8-Diisopropylamino-3,6-dioxaoctyl)dimethylamine
(10.0 g, 40 mmol) was heated under reflux with bromoethane
(10.8 g, 0.1 mol) in ethanenitrile (20 cm3) for 30 h. After
evaporation of the solvent and excess bromoethane in vacuo
at 60 1C, the product was recrystallised from ethanenitrile
(10 cm3). After drying under high vacuum at 60 1C overnight a
yellow powder was obtained (12.31 g, 33.5 mmol, 84% yield).
1H-NMR (300 MHz, d4-methanol): d/ppm = 1.04 (d, J =
(5-Diisopropylamino-3-oxapentyl)dimethylethylammonium bis-
{(trifluoromethyl)sulfonyl}amide ([iPr2N(CH2)2O(CH2)2N112][NTf2]).
Lithium bis{(trifluoromethyl)sulfonyl}amide (7.3 g, 25.5 mmol)
in water (10 cm3) was added to a solution of (5-diisopropyl-
amino-3-oxapentyl)dimethylethylammonium bromide (7.55 g,
23.3 mmol) in dichloromethane (100 cm3). After extraction of
the organic phase with water (5 ꢂ 20 cm3), dichloromethane
was removed in vacuo at 40 1C. The product was further
purified by filtration through charcoal as a solution in ethane-
nitrile (30 cm3). After removal of the solvent and drying
overnight in high vacuum at 60 1C, the product was obtained
as a pale yellow liquid (11.35 g, 21.6 mmol, 93% yield).
Mp (DSC): ꢁ77 1C. 1H-NMR (300 MHz, d-trichloro-
i
6.6 Hz, 12H, Pr-CH3); 1.38 (t, J = 7.2 Hz, 3H, Et-CH3);
2.67 (t, J = 6.7 Hz, 2H, N-CH2); 3.04 (p, J = 6.6 Hz, 2H,
iPr-CH); 3.15 (s, 6H, N+-CH3); 3.42–3.61 (m, 6H, O-CH2
and N+-CH2); 3.83–3.93 (s, 4H, OCH2CH2O).
Ethyl(8-diisopropylamino-3,6-dioxaoctyl)dimethylammonium
bis{(trifluoromethyl)sulfonyl}imide ([iPr2N(CH2)2(OCH2CH2)2N112]-
[NTf2]). Lithium bis{(trifluoromethyl)sulfonyl}amide (6.42 g,
22.4 mmol) in water (10 cm3) was added to a solution of
ethyl(8-diisopropylamino-3,6-dioxaoctyl)dimethylammonium
bromide (7.55 g, 21.3 mmol) in dichloromethane (100 cm3).
After extraction of the organic phase with water (5 ꢂ 20 cm3),
dichloromethane was removed in vacuo at 40 1C. The product
was further purified by filtration through charcoal as a solution
in ethanenitrile (30 cm3). After removal of the solvent in vacuo
and drying in high vacuum at 60 1C overnight, the product was
obtained as a pale yellow liquid (11.85 g, 19.8 mmol, 93% yield).
Mp (DSC): ꢁ82 1C. 1H-NMR (300 MHz, d-trichloromethane):
i
methane): d/ppm = 0.99 (d, J = 6.6 Hz, 12H, Pr-CH3);
1.38 (t, J = 7.4 Hz, 3H, Et-CH3); 2.62 (t, J = 6.5 Hz, 2H,
i
N-CH2); 3.01 (p, J = 6.6 Hz, 2H, Pr-CH); 3.09 (s, 6H, N+-
CH3); 3.39–3.53 (m, 6H, O-CH2 and N+CH2); 3.79–3.88
(m, 2H, O-CH2). 13C-NMR (75 MHz, d-trichloromethane):
d/ppm = 8.33 (Et-CH3); 20.68 (iPr-CH3); 44.65 (iPr-CH);
49.47 (N+-CH3); 51.28 (N-CH2); 62.78, 63.26 (N+-CH2);
64.56, 72.41 (O-CH2); 119.92 (q, JCF = 321 Hz, CF3). Elemental
analysis % calc. (% found): C 36.56 (35.81), H 6.33 (6.18), N
i
d/ppm = 1.04 (d, J = 6.6 Hz, 12H, Pr-CH3); 1.38 (t, J =
7.5 Hz, 3H, Et-CH3); 2.64 (t, J = 7.5 Hz, 2H, N-CH2); 3.01
i
8.00 (8.10). MS ES+ m/z (% rel. intensity): 172 [iPr2N(CH2)2-
(p, J = 6.6 Hz, 2H, Pr-CH); 3.13 (s, 6H, N+-CH3); 3.43
+
O(CH2)2]+ (37), 245 [iPr2N(CH2)2O(CH2)2N112
]
(100). MS
ꢁ
(t, 2H, J = 7.0 Hz, N-CH2-CH2); 3.49–3.53 (m, 4H, O-CH2
and N+-CH2); 3.60 (t, 2H, J = 7.0 Hz, N+-CH2CH2), 3.91
(s, 4H, O-CH2-CH2-O). 13C-NMR (75 MHz, d-trichloro-
methane): d/ppm = 7.44 (Et-CH3); 19.67 (iPr-CH3); 44.15
(N-CH2) 49.30 (iPr-CH); 49.30 (N+-CH3); 50.43 (N-CH2);
ESꢁ m/z (% rel. intensity): 147 NTfꢁ (9), 280 NTf2 (100).
Viscosity at 25 1C: 389 cP. Density at 25 1C: 1.277 g cmꢁ3
.
(8-Diisopropylamino-3,6-dioxaoctyl)dimethylamine. Into
a
60.93, 62.33 (N+-CH2); 64.56, 72.41 (O-CH2); 119.92 (q, JCF
=
solution of 2-[2-(dimethylamino)ethoxy]ethanol (42.60 g,
0.4 mol) in dry tetrahydrofuran (300 cm3) at 0 1C was slowly
added sodium hydride (60% dispersion in mineral oil, 20.0 g,
0.5 mol) and the mixture was stirred for one hour. 2-Diiso-
propylaminoethyl chloride hydrochloride (60.0 g, 0.36 mol)
was slowly added. The reaction mixture was heated under
reflux for 24 h and then quenched by dropwise addition of
water (40 cm3) at 0 1C. After evaporation of tetrahydrofuran
in vacuo at 50 1C, the reaction mixture was diluted with water
(30 cm3) and extracted with dichloromethane (3 ꢂ 50 cm3).
The combined organic extracts were dried with sodium sulfate
(5 g) and the solvent was removed in vacuo at 40 1C. The crude
product was purified by Kugelrohr distillation at 140 1C at
0.01 bar; (52.08 g, 0.2 mol, 50% yield) of a colourless liquid
was obtained.
321 Hz, CF3). Elemental analysis % calc. (% found):
C 37.74 (37.95), H 6.45 (6.25), N 7.43 (7.38). MS ES+ m/z
(% rel. intensity): 172 [M ꢁ NEtMe2]+ (37), 245 [iPr2N(CH2)2-
(OCH2)2N112
]
+ (100). MS ESꢁ m/z (% rel. intensity): 147 NTfꢁ
ꢁ
(9), 280 NTf2 (100). Viscosity at 25 1C: 195 cP. Density at
25 1C: 1.247 g cmꢁ3
.
Procedure used to probe the ionic liquid basicity using universal
indicator
An ethanolic solution (0.040 g) of universal indicator (Merck-
BDH) was dissolved in ionic liquid (1 cm3) and the alcohol
solvent removed in vacuo. The electronic absorption spectrum
of the pure ionic liquid was subtracted as a background in the
measurement of each ionic liquid/indicator solution. It should
be noted that the presence of water can have a significant effect
on the spectra observed, as shown by MacFarlane et al. and
therefore careful drying of the ionic liquid/indicator solution
must be performed.30
1H-NMR (300 MHz, d-trichloromethane): d/ppm = 0.99
i
(d, J = 6.7 Hz, 12H, Pr-CH3); 2.26 (s, 6H, NCH3); 2.82
(t, J = 2.6 Hz, 2H, (CH3)2NCH2); 2.88 (h, J = 6.7 Hz,
i
2H, Pr-CH); 3.01 (t, J = 2.7 Hz, 2H, Pr2NCH2); 3.61
i
ꢀc
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Typical procedure for the Heck reaction catalysed by Hu
¨
nig’s
S. Kobayashi, J. Organomet. Chem., 2004, 689, 3806; I. Fenger and
C. Le Drian, Tetrahedron Lett., 1998, 39, 4287.
5 M. Vaultier and S. Gmouh, World Pat., WO2004/029 004, 2004;
S. Anjaiah, S. Chandrasekhar and R. Gree, Tetrahedron Lett.,
2004, 45, 569; J. Fraga-Dubreuil and J. P. Bazureau, Tetrahedron,
2003, 59, 6121.
6 J. Fraga-Dubreuil and J. P. Bazureau, Tetrahedron Lett., 2001, 42,
6097; E. D. Bates, R. D. Mayton, I. Ntai and J. H. Davis Jr.,
J. Am. Chem. Soc., 2002, 124, 926.
7 C. P. Mehnert, R. A. Cook, N. C. Dispenziere and M. Afeworki,
J. Am. Chem. Soc., 2002, 124, 12932; W. Miao and T. H. Chan,
Org. Lett., 2003, 5, 5003; S. Anjaiah, S. Chandrasekhar and
R. Gree, Tetrahedron Lett., 2004, 45, 569; A. E. Visser,
R. P. Swatloski, W. M. Reichert, J. H. Davis Jr., R. D. Rogers,
R. Mayton, S. Sheff and A. Wierzbicki, Chem. Commun.,
2001, 135.
base
To a suspension of Pd(O2CMe)2 (0.011 g, 0.05 mmol) in 4-tert-
butyliodobenzene (1.241 g, 5 mmol) were added 2-methyl-
prop-2-en-1-ol (0.367 g, 5.1 mmol) and Hunig’s base (0.37 cm3,
10 mmol) in a Schlenk tube. The sealed reaction vessel was
heated at 95 1C for 10 h with stirring. The cooled reaction
mixture was concentrated in vacuo at 60 1C and extracted with
cyclohexane (2 ꢂ 5 cm3) to remove products. Evaporation of
the solvent from combined cyclohexane extracts yielded the
products. The extracted product was analysed by GC.
Typical procedure for the Heck reaction catalysed by ionic
liquids
8 Q. Yao and Y. Zhang, Angew. Chem., Int. Ed., 2003, 42, 3395;
N. Audic, H. Clavier, M. Mauduit and J.-C. Guillemin, J. Am.
Chem. Soc., 2003, 125, 9248.
4-tert-Butyliodobenzene (1.241 g, 5 mmol) and 2-methylprop-
2-en-1-ol (0.367 g, 5.1 mmol) and Pd(O2CMe)2 (0.011 g,
0.05 mmol) were added to the base-tethered ionic liquid
(B3.7 cm3, 10 mmol) in a Schlenk tube. The sealed reaction
vessel was heated at 95 1C for 10 h with stirring. The cooled
reaction mixture was extracted with cyclohexane (4 ꢂ 5 cm3)
to remove products from the ionic liquid. Evaporation of
the solvent from combined cyclohexane extracts yielded the
products. The extracted product was analysed by GC.
9 W. Miao and T. H. Chan, Acc. Chem. Res., 2006, 39, 897.
10 M. Yoshizawa, M. Hirao, K. Ito-Akita and H. Ohno, J. Mater.
Chem., 2001, 11, 1057.
11 A. C. Cole, J. L. Jensen, I. Ntai, K. L. Tran, K. J. Weaver,
D. C. Forbes and J. H. Davis, J. Am. Chem. Soc., 2002, 124,
5962.
12 D. C. Forbes and K. J. Weaver, J. Mol. Catal. A: Chem., 2004, 214,
129.
13 Y. L. Gu, F. Shi and Y. Q. Deng, Catal. Commun., 2003, 4,
597.
14 P. Nockemann, B. Thijs, S. Pittois, J. Thoen, C. Glorieux, K. van
Hecke, L. van Meervelt, B. Kirchner and K. Binnemans, J. Phys.
Chem. B, 2006, 110, 20978; P. Nockemann, B. Thijs, T. N. Parac-
Vogt, K. van Hecke, L. van Meervelt, B. Tinant, I. Hartenbach,
T. Schleid, V. T. Ngan, M. T. Nguyen and K. Binnemans, Inorg.
Chem., 2008, 47, 9987.
15 For example, D. B. Zhao, Z. F. Fei, T. J. Geldbach, R. Scopelliti
and P. J. Dyson, J. Am. Chem. Soc., 2004, 126, 15876; C. Chiappe,
D. Pieraccini, Z. B. Zhao, Z. F. Fei and P. J. Dyson, Adv. Synth.
Catal., 2006, 348, 68; Z. F. Fei, Z. B. Zhao, D. Pieraccini,
W. H. Ang, T. J. Geldbach, R. Scopelliti, C. Chiappe and
P. J. Dyson, Organometallics, 2007, 26, 1588; C. Hardacre,
J. D. Holbrey, C. L. Mullan, M. Nieuwenhuyzen,
W. M. Reichert, K. R. Seddon and S. J. Teat, New J. Chem.,
2008, 32, 1953; C. Hardacre, J. D. Holbrey, C. L. Mullan,
M. Nieuwenhuyzen, T. G. A. Youngs, D. T. Bowron and
S. J. Teat, Phys. Chem. Chem. Phys., 2010, 12, 1842–1853.
16 A. Zhu, T. Jiang, D. Wang, B. Han, L. Liu, J. Huang, J. Zhang
and D. Sun, Green Chem., 2005, 7, 514.
Typical procedure for the Knoevenagel reaction
Benzaldehyde (0.424 g, 4 mmol) and ethyl cyanoethanoate
(0.464 g, 4.1 mmol) were added to the base-tethered ionic
liquid (0.15 cm3, 0.4 mmol) into a sealed Schlenk tube and
stirred at room temperature. The products were extracted into
cyclohexene (4 ꢂ 4 cm3) and evaporation of the solvent from
combined cyclohexene extracts yielded the products. The
extracted product was analysed by GC.
Acknowledgements
The authors wish to thank the EPSRC through the manu-
facturing molecule initiative (MMI) and a portfolio partnership,
QUILL and DELNI (AMcK) for funding this project.
17 T. Jiang, H. Gao, B. Han, G. Zhao, Y. Chang, W. Wu, L. Gao and
G. Yang, Tetrahedron Lett., 2004, 45, 2699.
18 X. Xin, X. Guo, H. Duan, Y. Lin and H. Sun, Catal. Commun.,
2007, 8, 115.
19 M. Lombardo, S. Easwar, F. Pasi and C. Trombinia, Adv. Synth.
Catal., 2009, 351, 276.
References
20 A. E. Visser, R. P. Swatlowski, S. T. Griffin, D. H. Hartman and
R. D. Rogers, Sep. Sci. Technol., 2001, 36, 785; A. E.
Visser, R. P. Swatlowski, S. T. Griffin, R. Mayton, S. Sheff,
A. Wierzbicki and R. D. Rogers, Environ. Sci. Technol., 2002,
36, 2523.
1 T. Welton, Chem. Rev., 1999, 99, 2071; N. V. Plechkova and
K. R. Seddon, Chem. Soc. Rev., 2008, 37, 123; J. B. Harper and
M. N. Kobrak, Mini-Rev. Org. Chem., 2006, 3, 253;
V. I. Parvulescu and C. Hardacre, Chem. Rev., 2007, 107, 2615;
P. Wasserscheid and T. Welton, Ionic Liquids in Synthesis,
Wiley-VCH, Weinheim, 2007.
21 S. H. Park, D. Demberelnyamba, S. Ho Jang and M. Woo Byun,
Chem. Lett., 2006, 35, 1024.
2 M. Freemantle, Chem. Eng. News, 1998, 76(13), 32.
22 M. J. Earle, K. R. Seddon, S. Forsyth, U. Frohlich, N. Gunaratne
and S. Katdare, World Pat., WO2006/072 7752006.
23 H. Tokuda, K. Hayamizu, K. Ishii, M. A. B. H. Susan and
M. Watanabe, J. Phys. Chem. B, 2005, 109, 6103; L. C. Branco,
J. N. Rosa, J. J. M. Ramos and C. A. M. Afonso, Chem.–Eur. J.,
2002, 8, 3671; K. R. Seddon, A. Stark and M. J. Torres, ACS
Symp. Ser., 2002, 819, 34.
24 I. M. Kolthoff, Acid-Base Indicators, Macmillan, New York, 1937,
p. 315.
25 For reviews on the solvatochromic effect in ionic liquids, see
C. F. Poole, J. Chromatogr., A, 2004, 1037, 49; C. Reichardt,
Green Chem., 2005, 7, 339.
3 J. H. Davis, Jr., Chem. Lett., 2004, 33, 1072; E. D. Bates,
R. D. Mayton, I. Ntai and J. H. Davis, J. Am. Chem. Soc., 2002,
124, 926.
4 P. Lozano, T. De Diego, T. Sauer, M. Vaultier, S. Gmouh and
J. L. Iborra, J. Supercrit. Fluids, 2007, 40, 93; C. Brochwitz,
A. Feldhoff, U. Kunz, M. Vaultier and A. Kirschning, Lett. Org.
Chem., 2006, 3, 442; R. S. Timofte and S. Woodward, Tetrahedron
Lett., 2004, 45, 39; B. Altava, M. Burguete, E. Garcıa-Verdugo,
S. V. Luis and M. J. Vicent, Tetrahedron Lett., 2001, 42, 8459;
S. Rodrigues, F. Silveira, J. H. Z. dos Santos and M. L. Ferreira,
J. Mol. Catal. A: Chem., 2004, 216, 19; H. Yoshida, C. Murata and
T. Hattori, J. Catal., 2000, 194, 364; R. M. Magdalene,
E. G. Leelamani and N. M. Nanje Gowda, J. Mol. Catal. A:
Chem., 2004, 223, 17; R. Akiyama, T. Sagae, M. Sugiura and
26 R. Santillan, N. Farfan, D. Castillo, A. Gutierrez and H. Hopfl,
Chem.–Eur. J., 1998, 4, 1904.
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This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010
730 | New J. Chem., 2010, 34, 723–731

View Article Online
27 Solvatochromic shift is a change of spectral band position in the
absorption of a molecule to a longer wavelength owing to a change
in environmental conditions such as solvent polarity.
29 C. Paun, J. Barklie, P. Goodrich, H. Q. N. Gunaratne,
A. McKeown, V. I. Parvulescu and C. Hardacre, J. Mol. Catal.
A: Chem., 2007, 269, 64.
28 S. A. Forsyth, H. Q. N. Gunaratne, C. Hardacre, A. McKeown, D. W.
Rooney and K. R. Seddon, J. Mol. Catal. A: Chem., 2005, 231, 61.
30 D. R. MacFarlane, J. M. Pringle, K. M. Johansson, S. A. Forsyth
and M. Forsyth, Chem. Commun., 2006, 1905.
ꢀc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010
New J. Chem., 2010, 34, 723–731 | 731