Synthesis and characterization of ammonium-, pyridinium-, and pyrrolidinium-based sulfonamido functionalized ionic liquids

Article abstract of DOI:10.1080/00397911.2011.582597

New homologous ammonium-, pyridinium-, and pyrrolidinium-based sulfonamido functionalized ionic liquids have been synthesized in two steps using monoethanolamine, methanesulfonyl chloride, and tosyl chloride as precursors with ethanol as solvent. Attempts

Full text of DOI:10.1080/00397911.2011.582597

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Synthesis and Characterization
of Ammonium-, Pyridinium-, and
Pyrrolidinium-Based Sulfonamido
Functionalized Ionic Liquids
Shunmugavel Saravanamurugan a , Rasmus Fehrmann a & Anders
Riisager a
a Centre for Catalysis and Sustainable Chemistry, Department of
Chemistry, Technical University of Denmark, Lyngby, Denmark
Accepted author version posted online: 11 Nov 2011.Published
online: 18 Jul 2012.
To cite this article: Shunmugavel Saravanamurugan , Rasmus Fehrmann & Anders Riisager (2012):
Synthesis and Characterization of Ammonium-, Pyridinium-, and Pyrrolidinium-Based Sulfonamido
Functionalized Ionic Liquids, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 42:22, 3383-3394
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Synthetic Communications1, 42: 3383–3394, 2012
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2011.582597
SYNTHESIS AND CHARACTERIZATION OF
AMMONIUM-, PYRIDINIUM-, AND
PYRROLIDINIUM-BASED SULFONAMIDO
FUNCTIONALIZED IONIC LIQUIDS
Shunmugavel Saravanamurugan, Rasmus Fehrmann, and
Anders Riisager
Centre for Catalysis and Sustainable Chemistry, Department of Chemistry,
Technical University of Denmark, Lyngby, Denmark
GRAPHICAL ABSTRACT
Abstract New homologous ammonium-, pyridinium-, and pyrrolidinium-based sulfonamido
functionalized ionic liquids have been synthesized in two steps using monoethanolamine,
methanesulfonyl chloride, and tosyl chloride as precursors with ethanol as solvent. Attempts
to synthesize dual amino functionalized ionic liquid containing both a primary and a second-
ary amine group in the same ionic liquid are also reported. All functionalized ionic liquids
were characterized by 1H and 13C NMR. Melting point and thermal stability of the func-
tionalized ionic liquids were measured by differential scanning calorimetry and thermogra-
vimetric analysis.
Keywords Amine; ionic liquid; methanesulfonyl; sulfonamido; tosyl
INTRODUCTION
New technologies where ionic liquids are used as catalysts, solvents, absor-
bents, electrolytes, and active materials in membranes have rapidly emerged within
the past decade.[1–4] Some of the main advantages of applying ionic liquids in such
applications are their practically nonvolatile nature, relatively high thermal stability,
adjustable physical and chemical properties, recyclability, and good phase separation
with lipophilic reagents.[5–8]
Received March 8, 2011.
Address correspondence to Anders Riisager, Centre for Catalysis and Sustainable Chemistry,
Department of Chemistry, Building 207, Technical University of Denmark, DK 2800 Kgs. Lyngby,
Denmark. E-mail: ar@kemi.dtu.dk
3383

3384
S. SARAVANAMURUGAN, R. FEHRMANN, AND A. RIISAGER
The first ionic liquid, ethanolammonium nitrate (melting point of 52–55 ꢀC),
was discovered in 1888.[9] Later, in 1914 Walden prepared the first room-temperature
ionic liquid.[10] However, the first reported work using an ionic liquid as catalyst and
solvent was published in 1985 for Friedel–Craft reactions with 1-methyl-3-ethylimi-
dazolium chloride and aluminum chloride.[11] Since this pioneer study, the use of
ionic liquids has progressively increased not only in the field of catalysis but also
in other applications. For example, it has been found that classical ionic liquids such
as imidazolium-based ionic liquids (often referred to as first-generation ionic liquids)
have the ability to dissolve crystalline cellulose,[12] to act as absorbents and selec-
tively take up gases (CO2, SO2, C2H4 etc.) by physisorption,[13] and to provide
reusable reaction media for organic transformations.[14,15]
Owing to the lack of chemical functionality in the classical ionic liquids, recent
efforts have aimed at developing new concepts by introduction of functional groups
into the ionic liquids. In this juncture, Davis and coworkers reported in 2002 the
first amine-functionalized imidazolium-based ionic liquids (task specific) for CO2
capture, which can react with CO2 at ambient temperature and pressure.[16] Subse-
quently, sulfonic acid tethered imidazolium-based ionic liquids have also been
reported by the same group and applied for Fischer esterification and pinacol
rearrangement reactions.[17] Here the liquids had excellent catalytic activity and
potential to be recycled at least five times without loss of activity. Since this pioneer
work, several other reports on the synthesis and application of new acid- and base-
functionalized ionic liquids have followed.[18–20]
In this article, we report the synthesis and characterization of a new series of
homologous sulfonamido functionalized ionic liquids containing ammonium, pyridi-
nium, and pyrrolidinium cations. The strategy was to introduce an electron-
withdrawing group, sulfonamido group, in the ionic liquid in proximity to a primary
amine group in order to lower its basicity. Synthesis of bifunctionalized ionic liquids
comprising both a primary and a secondary amine group was also attempted with
the introduced synthetic methodology.
RESULTS AND DISCUSSION
Initially, we set out to synthesize amine functionalized ammonium-based ionic
liquids in two steps as shown in Schemes 1 and 2. In the first step, monoethanola-
mine was reacted with methanesulfonyl chloride in acetonitrile (Scheme 1). Since
the reaction was highly exothermic, the methanesulfonyl chloride was added drop-
wise at 0 ꢀC. The reaction mixture turned from colorless to yellow, indicative of reac-
tion. To ensure that a free NH group was formed in the intermediate product, a
slight excess of pyridine was added to capture the liberated hydrogen chloride. After
the addition of methanesulfonyl chloride, the reaction temperature was brought to
room temperature and the mixture was stirred overnight. Finally, the targeted pro-
duct, 2-(methylsulfonamido)ethyl methylsulfonate (MSAEMS), was isolated by col-
umn chromatography (46% yield). The identity of the product was confirmed by
NMR analysis in CDCl3 and dimethylsulfoxide (DMSO-d6) solvents, where the
1
NH signal appeared as triplets at 5.35 and 7.35 ppm, respectively, in the H NMR
spectra (in D2O solvent the signal was not visible because of proton exchange).
The isolated MSAEMS was subsequently used as a precursor to make the

SULFONAMIDO FUNCTIONALIZED IONIC LIQUIDS
3385
Scheme 1. Synthesis of IL-Sulfo-1.
Scheme 2. Synthesis of IL-Sulfo-2.

3386
S. SARAVANAMURUGAN, R. FEHRMANN, AND A. RIISAGER
sulfonamido functionalized ammonium-, pyridinium-, and pyrrolidinium-based
ionic liquids in a second step.
In the second step, MSAEMS and triethylamine were allowed to react in
1
ethanol while the reaction progress was monitored by H NMR on aliquots with-
drawn from the reaction mixture by following the disappearance of the O-CH2
signal of MSAEMS at d ¼ 4.35 ppm. The reaction was allowed to react until
the signal was undetectable (typically 24 h). The resulting ionic liquid, N,N,N-
triethyl-2-(methylsulfonamido)ethaneaminium methanesulfonate (IL-Sulfo-1)
was purified by extraction with a mixture of toluene and dichloromethane and
recovered as a colorless viscous liquid. The isolated yield of IL-Sulfo-1 was more
than 95%.
A tosyl group was introduced into the ammonium-based ionic liquid by an
analogous procedure (Scheme 2). In the first reaction step, the isolated yield of the
corresponding product, 2-(4-methylphenylsulfonamido)ethyl-4-methylbenzenesulfo-
nate (MPSAEMBS), was 35% and thus less than with MSAEMS. All aliphatic
and aromatic protons, including the NH proton, were confirmed by 1H NMR analy-
sis. MPSAEMBS was further reacted with triethylamine to get the ionic liquid,
N,N,N-triethyl-2-(methylphenylsulfonamido)ethaneaminium 4-methylbenzenesulfo-
nate (IL-Sulfo-2). Excess reactants were removed by extraction with n-hexane under
reflux, and the product was recovered as a solid. The isolated yield of the ionic liquid
1
(IL-Sulfo-2) was here more than 98% and the identity was confirmed by H and
13C NMR.
By adopting the mentioned procedure, 1-(2-(methylsulfonamido)ethyl)pyridi-
nium methanesulfonate (IL-Sulfo-1a), 1-methyl-1-(2-(methylsulfonamido)ethyl)-
pyrrolidinium methanesulfonate (IL-Sulfo-1b), N,N-diethyl-2-hydroxy-N-(2-
(methylsulfonamido)ethyl)ethaneaminium methanesulfonate (IL-Sulfo-1c), 1-(2-(4-
methylphenylsulfonamido)ethyl)pyridinium 4-methylbenzenesulfonate (IL-Sulfo-
2a), and 1-methyl-1-(2-(methylphenylsulfonamido)ethyl)pyrrolidinium methylbenze-
neesulfonate (IL-Sulfo-2b) ionic liquids were also synthesized. Also here, the identity
of the ionic liquids was confirmed by 1H and 13C NMR analysis and the yields were
more than 95%. Additionally, high purity of the synthesized sulfonamido ionic
1
liquids was also confirmed by H NMR analysis. Hence, by comparing the integral
area of the methyl singlets from the ionic liquid and unidentified peaks, all the ionic
liquids were found to posses extraneous peaks corresponding to less than 3% of the
area of the methyl singlets. The structures of all the synthesized sulfonamido functio-
nalized ionic liquids are depicted in Fig. 1.
Attempts were made to synthesize a dual amino functionalized ionic liquid. The
synthetic strategy was to introduce both a primary amine group and a substituted sec-
ondary amine group, a sulfonamide group, in the same ionic liquid. The
bifunctionalized ionic liquid was synthesized in three steps following the strategy out-
lined in Scheme 3. As a source for the primary amine group, 3-(diethylamino)propy-
lamine (DEAPA) was chosen. To facilitate reaction only with the tertiary amine of
DEAPA, the primary amine group was initially protected as a carbamate. This was
done as the first step by reacting DEAPA with an equimolar amount of the protecting
reagent, di-tert-butyl dicarbonate (t-BOC) by dropwise addition of the reagent to the
amine at room temperature (caution: exothermic reaction). The identity of the
resulting amine protected compound, tert-butyl-(3-(diethylamino)propyl)carbamate,

SULFONAMIDO FUNCTIONALIZED IONIC LIQUIDS
3387
Figure 1. Structure of sulfonamido functionalized ionic liquids.
was confirmed by both 1H and 13C NMR. In a second reaction step, the carbamate-
protected compound was further reacted with an equimolar amount of MSAEMS to
get the sulfonamido functionalized ionic liquid, 3-((tert-butoxycarbonyl)amino)-N0,
N0-diethyl-N00-(2-(methylsulfonamido)ethyl) propaneammonium methanesulfonate.
The presence of the sulfonamide group in the product was also here confirmed by
NMR analysis. Finally, in a third reaction step the carbamate protection group
was removed by adding a few drops of hydrochloric acid to a methanolic solution
of the protected amine ionic liquid. In the final product, the presence of both a
1
primary and a secondary amine group was confirmed using H NMR analysis by
the disappearance of the signals from the t-BOC group (in D2O) and appearance
of the NH and NH2 signals (in DMSO-d6), respectively.
The thermal stability of the synthesized sulfonamide ionic liquids was deter-
mined by thermal gravimetric (TG) analysis (TGA=DSC 1 apparatus, Mettler
Toledo). The ionic liquid (4 to 16 mg) was placed in a sample holder and heated
from 40 to 600 ꢀC (10 ꢀC=min) under a nitrogen atmosphere. The measured ther-
mographs (Fig. 2) revealed that all of the new functionalized ionic liquids
remained stable up to at least 250 ꢀC. Melting points of the ionic liquids were
determined on 4 to 10 mg samples by differential scanning calorimetry using a
TA-2620-DSC equipped with cryostat cooling (2 to 10 ꢀC=min heating and cool-
ing rates).

3388
S. SARAVANAMURUGAN, R. FEHRMANN, AND A. RIISAGER
Scheme 3. Synthesis of IL-Sulfo-3.
CONCLUSION
A homologous series of new sulfonamido functionalized ionic liquids with
ammonium, pyridinium, and pyrrolidinium cations have been synthesized and char-
acterized by NMR, differential scanning calorimetry (DSC), and TG analyses. The
synthetic strategy also enabled synthesis of an ionic liquid comprising both a primary
and a secondary amine group. TGA results revealed that all of the ionic liquids were
thermally stable below 250 ꢀC.
MATERIALS
Monoethanolamine (>99%, Fluka), pyridine (>99.8%, Fluka), acetonitrile
(>99.9%, Sigma-Aldrich), methanesulfonyl chloride (>98%, Fluka), ethyl acetate

SULFONAMIDO FUNCTIONALIZED IONIC LIQUIDS
3389
Figure 2. TGA thermographs of sulfonamido functionalized ionic liquids.
(>99.7%, Sigma-Aldrich), dichloromethane (>99.8%, Sigma-Aldrich), toluene
(>99.9%, Sigma-Aldrich), toluene-4-sulfonyl chloride (>97%, Fluka), triethylamine
(99.9%, Sigma-Aldrich), 1-methylpyrrolidine (>99%, Fluka), 2-diethylaminoethanol
(>99%, Fluka), n-hexane (>96.5%, Sigma-Aldrich), and 3-(diethylamino)propyl-
amine (>99 þ %, Aldrich) were used as received.
EXPERIMENTAL
Synthesis of N,N,N-Triethyl-2-(methylsulfonamido)ethaneaminium
Methanesulfonate (IL-Sulfo-1)
Step 1. Monoethanolamine (3.0 g, 49.1 mmol), pyridine (7.91 g, 100 mmol),
and acetonitrile (65 ml) were mixed in a 250-ml, round-bottomed flask. Methanesul-
fonyl chloride (11.25 g, 98.2 mmol) was added dropwise to the reaction mixture at
0 ꢀC. After the addition, the solution was brought to room temperature and allowed
to stir overnight. Finally, the solvent was removed under reduced pressure, and the
major product, 2-(methylsulfonamido)ethyl methylsulfonate (MSAEMS), was iso-
lated by column chromatography using ethyl acetate=dichloromethane eluent.
Yield ¼ 46%.
1H NMR (300 MHz, D2O) d ¼ 3.02 (s, 3H; H3C-S-N), 3.18 (s, 3H; H3C-S-O),
3.4–3.48 (t, 2H; CH2-N), 4.3-4.4 (t, 2H; CH2-O); 1H NMR (300 MHz, CDCl3)
d ¼ 3.0 (s, 3H; H3C-S-N), 3.1 (s, 3H; H3C-S-O), 3.4–3.5 (q, 2H; CH2-N), 4.3–4.4
1
(t, 2H; CH2-O), 5.3–5.42 (t, 1H; NH); H NMR (300 MHz, DMSO-d6) d ¼ 2.90 (s,
3H; H3C-S-N), 3.18 (s, 3H; H3C-S-O), 3.2–3.3 (q, 2H; CH2-N), 4.15–4.22 (t, 2H;
CH2-O), 7.3–7.4 (t, 1H; NH); 13C NMR (75.5 MHz, D2O) d ¼ 36.8 (H3C-S-N),
39.7 (H2C-N), 41.9 (H3C-S-O), 70.3 (H2C-O); 13C NMR (75.5 MHz, CDCl3)
d ¼ 37.7 (H3C-S-N), 40.9 (H2C-N), 42.5 (H3C-S-O), 69.2 (H2C-O); 13C NMR
(75.5 MHz, DMSO-d6) d ¼ 37.4 (H3C-S-N), 42.2 (H2C-N), 49.9 (H3C-S-O), 69.95
(H2C-O).

3390
S. SARAVANAMURUGAN, R. FEHRMANN, AND A. RIISAGER
Step 2. MSAEMS (2.5 g, 11.5 mmol), triethylamine (3.2 g, 31.6 mmol), and
50 ml of ethanol were placed in a 100-ml, round-bottomed flask and refluxed at
110 ꢀC. The solution was then cooled to room temperature, and the solvent removed
under reduced pressure to get the ionic liquid, IL-Sulfo-1. The ionic liquid was
purified by extraction with toluene–dichloromethane mixture and recovered as a
colorless viscous liquid after removal of the solvent. Yield ¼ 95%. Mp < ꢁ50 ꢀC.
1H NMR (300 MHz, D2O) d ¼ 1.1–1.2 (t, 9H; 3CH3), 2.65 (s, 3H; H3C-S-N),
2.98 (s, 3H; H3C-S-O), 3.18–3.3 (m, 8H; 3(CH2)-N and H2C-N), 3.4–3.5 (t, 2H;
H2C-N); 13C NMR (75.5 MHz, D2O) d ¼ 6.83 (CH3), 36.0 (H2C-N), 38.7 (H3C-S-
N), 39.1 (H3C-S-O), 53.4 [3(CH2)-N], 55.3 (H2C-N).
Synthesis of N,N,N-Triethyl-2-(methylphenylsulfonamido)-
ethaneaminium 4-Methylbenzenesulfonate (IL-Sulfo-2)
Step 1. Monoethanolamine (5.0 g, 81.9 mmol), pyridine (12.97 g, 164 mmol),
and acetonitrile (65 ml) were mixed in a 250-ml, round-bottomed flask. Toluene-4-
-sulfonyl chloride (31.2 g, 163.8 mmol) was dissolved in acetonitrile (20 ml) and added
dropwise to the solution at 0 ꢀC. Afterward, the solution was brought to room
temperature and allowed to stir overnight at room temperature. The solvent was
then removed under reduced pressure, and the major product, 2(4-methyl-
phenylsulfonamido)ethyl-4-methylbenzenesulfonate (MPSAEMBS), was isolated by
column chromatography using ethylacetate=dichloromethane eluent. Yield ¼ 35%.
1H NMR (300MHz, DMSO-d6) d ¼ 2.35 (s, 3H; H3C-Ar-S-N), 2.4 (s, 3H;
H3C-Ar-S-O), 2.9–3.0 (q, 2H, H2C-N), 3.9–4.0 (t, 2H, H2C-O), 7.3–7.4 (d, 2H; Ar-CH),
7.4–7.5 (d, 2H; Ar-CH), 7.6–7.65 (d, 2H; CH), 7.7–7.8 (d, 2H; CH), 7.9–7.95 (t, 1H;
NH); 13C NMR (75.5 MHz, DMSO-d6) d ¼ 21.6 (H3C-Ar-S-N), 21.7 (H3C-Ar-S-O),
42.1 (H2C-N), 69.8 (H2C-O), 127.2 (Ar-CH), 128.3 (Ar-CH), 130.3 (Ar-CH), 130.8
(Ar-CH), 132.7 (C-S-N), 138 (Ar-C-CH3), 143.5 (Ar-C-CH3), 145.7 (C-S-O).
Step 2. MPSAEMBS (0.51 g, 1.38 mmol), triethylamine (0.75 g, 7.4 mmol),
and 5.0 g of ethanol were placed in a 15-ml Ace pressure tube and refluxed at
100 ꢀC for 24 h. The solution was then cooled to room temperature, and the solvent
removed under reduced pressure to get the ionic liquid, IL-Sulfo-2. Unconverted
reactants were removed by extraction with n-hexane under reflux, and the product
recovered as a white solid. Yield ¼ 98%. Mp ¼ 133 ꢀC.
1H NMR (300 MHz, DMSO-d6) d ¼ 1.1–1.2 (t, 9H; 3CH3), 2.28 (s, 3H; H3C-
Ar-S-N), 2.4 (s, 3H, H3C-Ar-S-O), 3.05–3.17 (q, 2H, H2C-N), 3.2–3.25 [(m, 8H;
4(H2C)-N)], 7.1 (d, 2H; Ar-CH), 7.2–7.3 (q, 4H; Ar-CH), 7.7 (d, 2H; Ar-CH),
8.0–8.1 (t, 1H; NH); 13C NMR (75.5 MHz, DMSO-d6) d ¼ 7.73 (3CH3), 21.49
(H3C-Ar-S-N), 21.68 (H3C-Ar-S-O), 36.48 (H2C-N), 53.1 [3(CH2)-N], 55.5
(H2C-N), 126.2 (Ar-CH), 127.3 (Ar-CH), 128.8 (Ar-CH), 130.5 (Ar-CH), 137.6
(Ar-C-S-N), 138.5 (Ar-CH), 143.8 (Ar-CH), 146.2 (Ar-C-S-O).
Synthesis of 1-(2-(Methylsulfonamido)ethyl)pyridinium
Methanesulfonate (IL-Sulfo-1a)
MSAEMS (1.0 g, 4.6 mmol), pyridine (1.82 g, 23.0 mmol), and 5.0 g of ethanol
were placed in a 15-ml Ace pressure tube and refluxed at 100 ꢀC for 24 h. The

SULFONAMIDO FUNCTIONALIZED IONIC LIQUIDS
3391
solution was then cooled to room temperature, and the solvent removed under
reduced pressure to get the ionic liquid, IL-Sulfo-1a. Unconverted reactants were
removed by extraction with n-hexane and toluene–dichloromethane mixture, and
the product recovered as a pale yellow solid. Yield ¼ 97%. Mp ¼ 83 ꢀC.
1H NMR (300 MHz, D2O) d ¼ 2.8 (s, 3H; H3C-S-N), 2.9 (s, 3H; H3C-S-O),
3.5–3.6 (t, 2H; H2C-N), 4.5–4.6 (t, 2H; H2C-N-Ar), 8.0 (t, 2H, Ar-CH-N), 8.5 (t,
1H, Ar-CH), 8.8 (d, 2H, Ar-CH); 13C NMR (75.5 MHz, D2O) d ¼ 38.7 (H3C-S-
N), 39.2 (H3C-S-O), 43.1 (H2C-N), 61.6 (H2C-N-Ar), 128.4 (Ar-CH), 145.1 (Ar-CH-
N), 146.4 (Ar-CH).
Synthesis of 1-Methyl-1-(2-(methylsulfonamido)ethyl)pyrrolidinium
Methanesulfonate (IL-Sulfo-1b)
MSAEMS (0.5 g, 2.3 mmol), 1-methylpyrrolidine (1.0 g, 11.74 mmol), and 5.0 g
of ethanol were placed in a 15-ml Ace pressure tube and refluxed at 100 ꢀC for 24 h.
The solution was then cooled to room temperature, and the solvent removed under
reduced pressure to get the ionic liquid, IL-Sulfo-1b. Unconverted reactants were
removed by extraction with n-hexane and toluene–dichloromethane mixture and
recovered as a colorless viscous liquid. Yield ¼ 99%. Mp < ꢁ50 ꢀC.
1H NMR (300 MHz, D2O) d ¼ 2.02–2.12 (t, 4H; 2CH2), 2.63 (s, 3H; H3C-S-N),
2.99 (s, 3H; H3C-S-O), 3.0 (s, 3H;CH3), 3.4–3.6 (m, 8H; CH2-N-CH2,N-CH2-CH2-
N); 13C NMR (75.5 MHz, D2O) d ¼ 21.33 (2H2C), 37.85 (H2C-N), 39.05 (H3C-S-
N), 39.14 (H3C-S-O), 48.34 (H3C-N), 62.92 (H2C-N), 65.48 (2H2C-N).
Synthesis of N,N-Diethyl-2-hydroxy-N-(2-(methylsulfonamido)-
ethyl)ethaneaminium Methanesulfonate (IL-Sulfo-1c)
MSAEMS (0.5 g, 2.3 mmol), 2-diethylaminoethanol (1.34 g, 11.4 mmol), and
5.0 g of ethanol were placed in a 15-ml Ace pressure tube and refluxed at 100 ꢀC
for 24 h. The solution was then cooled to room temperature, and the solvent
removed under reduced pressure to get the ionic liquid (IL-Sulfo-1c). Unconverted
reactants were removed by extraction with n-hexane and toluene–dichloromethane
mixture, and the product recovered as a colorless viscous liquid. Yield ¼ 99%. Mp
< ꢁ50 ꢀC.
1H NMR (300 MHz, D2O) d ¼ 1.1–1.22 (t, 6H; 2CH3), 2.62 (s, 3H; H3C-S-N),
2.97 (s, 3H; H3C-S-O), 3.25–3.45 [m, 10H; -CH2-N-(CH2)2-CH2,-CH2-N], 3.85 (t,
2H;CH2-OH); 13C NMR (75.5 MHz, D2O) d ¼ 7.19 (2H3C), 36.20 (H2C-N), 39.03
(H3C-S-NH), 39.28 (H3C-S-O), 49.27 (H2C-N), 55.07 [2(H2C)-N], 56.84 (H2C-N),
59.04 (H2C-OH).
Synthesis of 1-(2-(4-Methylphenylsulfonamido)ethyl)pyridinium
4-Methylbenzenesulfonate (IL-Sulfo-2a)
MPSAEMBS (0.51 g, 1.38 mmol), pyridine (0.54 g, 6.8 mmol), and 5.0 g of
ethanol were placed in a 15-ml Ace pressure tube and refluxed at 100 ꢀC for 24 h.
The solution was then cooled to room temperature, and the solvent removed under
reduced pressure to get the ionic liquid, IL-Sulfo-2a. Unconverted reactants were

3392
S. SARAVANAMURUGAN, R. FEHRMANN, AND A. RIISAGER
removed by extracting with n-hexane under reflux, and the product recovered as a
solid. Yield ¼ 90%. Mp ¼ 180 ꢀC.
1H NMR (300 MHz, DMSO-d6) d ¼ 2.27 (s, 3H; H3C-Ar-S-N), 2.4 (s, 3H;
H3C-Ar-S-O), 3.3–3.4 (q, 2H, H2C-N), 4.6–4.7 (t, 2H, H2C-N-Ar), 7.1 (d, 2H;
Ar-CH), 7.4 (d, 2H; Ar-CH), 7.45 (d, 2H; Ar-CH), 7.5 (d, 2H; Ar-CH), 7.92 (t,
1H; NH), 8.2 (t, 2H; Ar-CH), 8.6 (t, 1H; Ar-CH), 9.0 (d, 2H; Ar-CH-N); 13C
NMR (75.5 MHz, DMSO-d6) d ¼ 21.49 (H3C-Ar-S-N), 21.50 (H3C-Ar-S-O), 42.35
(H2C-N-S), 60.15 (H2C-N-Ar), 126.2 (Ar-CH), 127.12 (Ar-CH), 128.56 (Ar-CH),
128.83 (Ar-CH), 130.5 (Ar-CH), 137.2 (Ar-C-S), 138.2 (Ar-CH), 144.0 (Ar-CH),
145.97 (Ar-CH-N), 146.0 (Ar-C-S), 146.2 (Ar-CH), 146.3 (Ar-CH).
Synthesis of 1-Methyl-1-(2-(methylphenylsulfonamido)ethyl)-
pyrrolidinium 4-Methylbenzenesulfonate (IL-Sulfo-2b)
MPSAEMBS (0.31 g, 0.84 mmol), 1-methylpyrrolidine (0.36 g, 4.2 mmol), and
5.0 g of ethanol were placed in a 15-ml Ace pressure tube and refluxed at 100 ꢀC
for 24 h. The solution was then cooled to room temperature, and the solvent
removed under reduced pressure to get IL-Sulfo-3b. Unconverted reactants were
removed by extracting with n-hexane under reflux, and the product recovered as a
solid. Yield ¼ 92%. Mp ¼ 129 ꢀC.
1H NMR (300 MHz, D2O) d ¼ 1.9–2.1 (t, 4H; 2CH2), 2.2 (s, 3H; H3C-Ar-S-N),
2.24 (s, 3H; H3C-Ar-S-O), 2.95 (s, 3H; H3C-N), 3.18–3.21 (t, 2H; H2C-N), 3.22–3.34
[m, 6H; CH2-N-(CH2)-CH2], 7.2 (d, 2H; Ar-CH), 7.3 (d, 2H; Ar-CH), 7.5 (d, 2H;
Ar-CH), 7.6 (d, 2H; Ar-CH); 13C NMR (75.5 MHz, DMSO-d6) d ¼ 21.36
(H3C-Ar-S-N), 21.46 (2H2C), 21.66 (H3C-Ar-S-O), 38.16 (H2C-N), 48.08 (H3C-N),
62.56 (H2C-N), 64.74 [2(H2C)-N], 126.17 (Ar-CH), 127.36 (Ar-CH), 128.88 (Ar-CH),
130.51 (Ar-CH), 137.38 (Ar-C-S-N), 138.62 (Ar-CH), 143.82 (Ar-CH), 146.03 (Ar-C-
S-O).
Synthesis of Dual-Amino Functionalized Ionic Liquid, 3-Amino-N,N-
diethyl-N-(2-(Methylsulfonamido)ethyl)propaneammonium
Methanesulfonate (IL-Sulfo-3)
Step 1: Protection of amino group. Di-tert-butyl dicarbonate (8.38 g,
38.4 mmol) was added drop wise to neat 3-(diethylamino)propylamine (DEAPA)
(5.0 g, 38.4 mmol) at room temperature (caution: exothermic reaction). The reaction
mixture was allowed to stir overnight. The major by-product, tert-butanol, was then
removed at reduced pressure to give tert-butyl(3-(diethylamino)propyl)carbamate.
Yield ¼ 98%.
1H NMR (300 MHz, CDCl3) d ¼ 0.5–1.0 (t, 6H; CH3), 1.35 (s, 9H; 3(CH3)-O),
1.2–2.0 (p, 2H; CH2), 2.3–2.4 [m, 6H; 3(CH2)-N], 3.15 (q, 2H; H2C-N); 13C NMR
(75.5 MHz, CDCl3) d ¼ 11.89 (CH3), 26.8 (CH2), 28.6 (3CH3), 61.6 (H2C-N), 40.3
=
(H2C-N), 46.9 (H2C-N), 51.8 (H2C-N), 78.7 (C-O) 156.3 (C O).
Step 2: Addition of sulfonamido group. MSAEMS (1.0 g, 4.6 mmol) and
tert-butyl(3-(diethylamino)propyl)carbamate (1.27 g, 5.5 mmol) and 50 ml of ethanol
were placed in a 100-ml round-bottomed flask and refluxed at 110 ꢀC for 48 h. The
solution was then cooled to room temperature, and the solvent removed under

SULFONAMIDO FUNCTIONALIZED IONIC LIQUIDS
3393
reduced pressure to get the ionic liquid, 3-((tert-butoxycarbonyl)amino)-N,N-
diethyl-N-(2-(methylsulfonamido)ethyl)propaneammonium methanesulfonate. The
ionic liquid was purified by extraction with toluene–dichloromethane mixture and
recovered as a brownish yellow viscous liquid. Yield ¼ 90%.
1H NMR (300 MHz, D2O) d ¼ 1.05–1.20 (t, 6H; 2CH3), 1.22–1.3 (s, 9H; 3CH3),
1.7–1.81 (m, 2H; CH2), 2.61 (s, 3H; H3C-S-N), 2.9 (s, 3H, H3C-S-O), 3.0–3.1 (t, 2H;
H2C-N), 3.1–3.2 (m, 2H, H2C-N), 3.2–3.35 [m, 6H, 3(CH2)-N], 3.37–3.41 (t, 2H,
CH2); 13C NMR (75.5 MHz, D2O) d ¼ 6.90 (2H3C-N), 22.01 (CH2), 27.92
[3(H3C)-O], 36.11 (H2C-N), 36.81 (H2C-N), 38.78 (H3C-S-N), 39.14 (H3C-S-O),
=
54.16 [2(H2C)-N], 55.5 (H2C-N), 55.7 (H2C-N), 81.2 (C-O), 158 (C O).
Step 3: Deprotection of amino group. The amino-protected ionic liquid
was dissolved in methanol. A few drops of hydrochloric acid (27%) were added to
the methanolic solution at room temperature, and the mixture was then allowed
to stir overnight. The unconverted, protected ionic liquid was extracted with dichlor-
omethane and obtained as a brownish yellow viscous liquid after removal of the
volatile solvent under reduced pressure. Yield ¼ 91%. Mp < ꢁ50 ꢀC.
1H NMR (300 MHz, D2O) d ¼ 1.1–1.12 (t, 6H; CH3), 1.9–2.1 (m, 2H; CH2),
2.62 (s, 3H; H3C-S-N), 2.8–3.0 (t, 2H; H2C-N), 3.0 (s, 3H, H3C-S-O), 3.2–3.38
[m, 8H; 4(CH2)-N], 3.4–3.45 (t, 2H, CH2-N); 13C NMR (75.5 MHz, D2O) d ¼ 7.06
(2CH3), 20 (CH2), 36.15 (H2C-N), 36.47 (H2C-N), 38.81 (H3C-S-N), 39.19
(H3C-S-O), 54.45 [(CH2)2-N], 54.46 (H2C-N), 56.15 (H2C-N).
ACKNOWLEDGMENT
This work was financially supported by the Danish Strategic Research Agency,
Dong Energy A=S, and Vattenfall A=S.
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