A.A. Chaugule et al. / Journal of Molecular Liquids 208 (2015) 314–321
315
shows high thermal stability and catalytic activity [23–25]. From the
above analysis, we believe that synthesis of tri-cationic ILs from glycerol
would be an eco-friendly procedure.
2.3. Typical procedure for synthesis of tri-cationic RTILs
2.3.1. Typical procedure for synthesis of trimesylate precursors
a
In the present study, we report synthesis and application of tri-
cationic room temperature ionic liquid (RTILs) in organic reaction. It is
reported that glycerol is a non-toxic, biodegradable liquid and can im-
part different advantages when combined with ILs. These advantages
make it ideal for use as a solvent and/or catalyst in organic synthesis.
Herein, we introduced imidazolium based tri-cationic RTILs functional-
ized with glycerol chain. Further, three different types of tri-cationic
RTILs using metathesis by changing the ion chemistry were synthesized.
We expected such ILs to have excellent physicochemical properties than
parent glycerol [26,27]. Furthermore, catalytical activities of these new
tri-cationic RTILs in probe of acid catalyzed reaction to 2-azidoalcohol
synthesis from epoxide were also investigated.
Scheme 1 illustrates the procedure for synthesis of trimesylate pre-
cursors. Initially, 1.0 mmol of glycerol and 3.5 mmol of trimethylamine
were added in a round bottom flask with excess of dichloromethane.
Then, the reaction mixture was cooled to 0 °C in ice bath, and subse-
quently stirred to have proper mixing. To this solution, 3.5 mmol of
methane sulfonyl chloride was added in a dropwise manner within a
period of 10 to 15 min. This reaction mixture was further subjected con-
tinuous stirring at room temperature for 12 h. Meanwhile, the comple-
tion of the reaction was monitored by TLC using (30% ethyl acetate:
hexane). After the completion of reaction, the reaction mixture was ex-
tracted with water and dichloromethane. The organic layer was washed
with water three times, dried over sodium sulfate and concentrated by
rotary evaporator. Resultant pre-precursor product appeared orange in
color which was kept at room temperature for 24 h to obtain afforded
2
. Experimental section
solid as trimesylate precursor (yield 89%).
1
H NMR (400 MHz, DMSO-d ):∂ 3.25 (s, 9H), 4.45 (d, 4H), 5.15 (m,
6
−
1
−1 −1
2
.1. Material
1H). FT-IR (500–4000 cm ): 768 cm
S = O), 2866, 2985 cm (C–H). C NMR (125 MHz): 14, 15, 45, 53.
HR-MS m/z [M-OMs] : 138.19. Calcd (%): C 22.08, H 4.32, O 44.12,
(S–O), 1113, 1380 cm
−
1
13
(
+
3
-methyl imidazole (99% pure), methane sulfonyl chloride (99%
pure), trimethyl amine (99% pure), glycerol (99% pure), potassium bro-
S 29.47; Found: C 21.07, H 4.31, O 44.12, S 29.46.
mide (99% pure), bis(trifluoromethanesulfonyl)imide lithium salt
(
(
99.95%), potassium hexafluorophosphate (99% pure), sodium sulfate
99%) and all substrates used for azidoalcohol synthesis from epoxide
2.3.2. Synthesis of glycerol-tri (3-methylimidazolium) trimesylate
[GLY(mim) ][OMs]
3
3
reaction were purchased form Sigma Aldrich, USA with (99%) purity
and were used as received. TLC analysis was performed on silica-gel
In this typical procedure, trimesylate precursor (1.0 mmol) and
3-methylimidazolium (3.0 mmol) was refluxed in acetonitrile at
75 °C for 28 h. After completion of the reaction, obtained mixture
was cooled down at room temperature and excess solvents were re-
moved by using a rotary evaporator. The remaining mixture was
washed three times with ethyl acetate to remove un-reacted starting
material. And, the afforded product resulted in formation of glycerol-
tri(3-methylimidazolium) trimesylate IL. (yield 91.25%)
(
SIL G/UV 254) plates to monitor the reaction.
2
.2. Characterization and measurements
The products were characterized by comparison of their spectro-
1
13
1
scopic data ( H NMR, C NMR and FT-IR analysis) with physical proper-
ties to those reported in the literature. NMR spectra were recorded in
[GLY(mim) ][OMs] Thick liquid: H NMR (400 MHz, DMSO-d ):∂
3
3,
6
2.41 (m, 3 × 3H), 3.47 (s, 3 × 3H), 3.66 (m, 5H), 9.24 (s, 3 × 1H),
−
1
−1
−1
DMSO-d
6
on 400 MHz spectrometers using TMS as an internal standard.
7.59–7.67 (m, 3 × 2H); FT-IR (500–4000 cm ): 1198, 1210 cm
−
1
−1
The FTIR spectra of samples were obtained by pelletizing the dried sam-
ples with potassium bromide (KBr) and recorded using Varian 2000
(S = O), 1398, 1465 cm (C = C), 1623 cm (C = N), 3095 cm
(Ar–H), 2912 cm 1, 2870 cm−1 (C–H). C NMR (125 MHz): 33.26,
−
13
+
(
4
Scimitar series) spectrophotometer. A spectrum was recorded from
39.4, 45.44, 48.5, 118, 120.34, 125.96, 136.90. HR-MS m/z [M-OMs] :
−
1
−1
000 to 500 cm
maintaining a resolution of 4 cm
with 32 scans
382.18. Analysis: C21H41N O S , Calcd (%): C 40.83, H 6.69, N 13.60, O
6
9 3
in transmittance mode. Mass spectra for samples were obtained using
Waters Micromass ZQ LC/MS 2000 (Scimitar series) spectrophotometer.
Thermogravimetric analysis (TGA, model SETARAM-92-16-18) was
used to check the thermal stability of samples. The heating of samples
were carried out at room temperature to 600 °C, with a heating rate of
23.31, S 15.56; Found: C 40.80, H 6.66, N 13.61, O 22.98, S 15.6.
2.3.3. Synthesis of glycerol-tri (3-methylimidazolium)
3
2 3
bis(trifluoromethanesufonyl)imide [GLY(mim) ][NTf ]
In round bottom flask, as aforementioned procedure the prepared
glycerol-tri (3-methylimidazolium)trimesylate (0.17 mol) and
bis(trifluoromethanesulfonyl)imide lithium salt (0.52 mol) reacted in
acetone at room temperature for 28 h. Then, the reaction mixture was
filtered and washed three times with acetone for complete removal of
salts formed during reaction. The [GLY(mim) ][NTf ] was afforded by
1
0 °C/min under a continuous purge of nitrogen (50 mL/min), and
spectra were collected using Q600 Software (TA Instruments). Differen-
tial scanning calorimetry (DSC) data were obtained in sealed aluminum
pan with cooling and heating rate of 10 °C/min on Mettler DSC822,
under the continuous purge of nitrogen (50 mL/min). Viscosity
measurements were performed using a Brook-field model DV-II+
programmable viscometer connected with temperature controlled
heating bath. All yields refer to isolated products.
3
2 3
evaporating the acetone under vacuum. (yield 91.96%).
1
[GLY(mim) ][NTf ] , Thick liquid: H NMR (400 MHz, DMSO-d ):∂
3
2 3
6
3.65 (s, 3 × 3H), 3.80 (m, 5H), 8.78 (s, 3 × 1H), 7.8 (m, 3 × 2H). FT-IR
Scheme 1. Synthesis of glycerol-tri (3-methylimidazolium) trimesylatetricationic RTILs.