G Model
CRAS2C-4046; No. of Pages 9
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S. Dogra et al. / C. R. Chimie xxx (2015) xxx–xxx
knowledge, such comparison between homogeneous and
heterogeneous PTCs depending upon their cation part has
been made so far.
liquids were purified over a silica gel column using hexane:
EtOAc (96:4) as the eluent. The successful formation of the
products was confirmed by 1H NMR, 13C NMR and FT–IR
spectra.
4. Experimental
4.4. Recycling of the immobilized IL, [SiO2–PTB]ClÀ(4a)
4.1. Materials and apparatus
Residual immobilized IL, 4a, was washed with methy-
lene chloride (2 Â 10 mL) to remove any organic impurity,
dried under vacuum for further use. Recycling was done till
minimum yields up to 88% were obtained (Table 4).
1H NMR (300 MHz), 13C NMR (75 MHz) and 29Si NMR
(57 MHz) spectra were recorded (d/ppm) on a JEOL A1 300F
spectrometer for solutions in CDCl3 with tetramethylsilane
(TMS) as an internal standard. IR spectra were recorded on
Nicolet iS50 FT–IR spectrometer. A focused monomode
microwave oven was used (Plazmatronika RM 2001 PC,
800 W). Elemental analyses were recorded on Flash
2000 Organic Elemental Analyzer CHNS-O. The melting
points were recorded on a Bu¨chi R-535 apparatus. BET
studies were recorded on a Quantachrome Instruments
Nova 2200e surface area and pore size analyzer (all
calculations were done using NovaWin software). TGA
graphs were recorded on a TA SDTQ600 instrument. SEM
imageswererecordedonCarloZEISSEVO 5SEM instrument.
Silica gel (100–200 mesh) was purchased from Merck and
purified with hot piranha solution (3:1, conc. H2SO4: 30%
H2O2) for 1 h, rinsed with water and dried under vacuum at
140 8C. All other chemicals (AR grade) were used without
any further purification.
4.5. Product characterization data
4.5.1. 1-(3’-Triethoxysilylpropyl)-tributylammonium chloride
(IL-ClÀ)
1H NMR (CDCl3):
d 0.73–0.75 (m, 2H, –CH2–Si–), 0.94–
0.99 (m, 9H, 3 Â CH3–(CH2)3–N–), 1.18–1.23 (m, 2H,–N–
CH2–CH2–CH2–Si–), 1.33–1.41 (m, 9H, 3 Â –O–CH2–CH3),
1.60–1.68 (m, 6H, 3 Â CH3–CH2–(CH2)2–N–), 1.69–1.79 (m,
6H, 3 Â CH3–CH2–CH2–CH2–N–), 3.26–3.40 (m, 8H, 4 Â –
CH2–N–), 3.49–3.53 (m, 6H, 3 Â –O–CH2–CH3). 13C NMR
(CDCl3):
d
10.31, 13.65, 18.22, 19.74, 20.14, 24.15, 25.13,
–46.6.
645, 739, 925, 1045, 1100, 1269, 1382,
26.53, 47.19, 52.13, 58.40, 58.95. 29Si NMR (CDCl3):
IR (cmÀ1, neat)
d
n
1459, 1690, 2874, 2959.
4.5.2. N-Hexyl phthalimide (7b)
Yellow oil. Bpt = 110 8C. 1H NMR (CDCl3, 300 MHz):
d
4.2. Preparation of the catalyst
0.87–0.89 (m, 3H,–CH2–CH3), 1.30–1.40 (m, 6H,–(CH2)3–
CH3), 1.65–1.67 (m, 2H,–N–CH2–CH2–), 3.64 (t, 2H,
J = 7.2 Hz,–N–CH2–), 7.68–7.80 (m, 4H, ArH). 13C NMR
The synthesis of 1-(3’-triethoxysilylpropyl)-tributy-
lammonium chloride (IL-ClÀ) was carried out using a
reported method [33] by refluxing tri-N-butylamine and 3-
chloropropyltriethoxysilane (1:1 ratio) under an atmo-
sphere of nitrogen at 90 8C–95 8C for 24 h (Scheme 1).
Further, the pretreated silica gel (3.30 g, 55 mmol) and IL-
ClÀ prepared above (2.13 g, 5 mmol) were refluxed in dry
toluene (50 mL) for 24 h under a nitrogen atmosphere. The
resultant product was filtered and washed with a 1:1
mixture of Et2O: DCM to obtain [SiO2–PTB]ClÀ (4a). Anion
exchange using a known procedure [34] was carried out by
(CDCl3, 75 MHz):
d 13.5, 22.1, 26.1, 28.1, 30.9, 37.4, 122.5,
131.8, 133.2, 167.5. IR (cmÀ1, neat)
1615, 1711, 1772, 2931.
n: 1062, 1172, 1396,
4.5.3. 1,5-N,N-Diphthalimide pentane (7d)
See reference number [35a].
4.5.4. N-Geranyl phthalimide (7e)
White solid. Mpt = 57–58 8C. 1H NMR (CDCl3, 300 MHz):
d
1.48 (s, 3H,–CH3), 1.54 (s, 3H, –CH3), 1.74 (s, 3H,–CH3),
immersing [SiO2–PTB]ClÀ in
acetonitrile (9:1) containing 1.1 equiv of NaBF4 at room
temperature for 60 h to give [SiO2–PTB]BF4À(4b).
a
mixture of acetone:
1.91–1.99 (m, 4H,–CH2–CH2–), 4.19 (d, 2H, J = 6.9 Hz,–CH2–
N–), 4.94 (t, 1H, J = 6.9 Hz,–CH = C[Me]2), 5.18 (t, 1H,
J = 6.9 Hz, =CH–CH2–N–), 7.59–7.62 (m, 2H, ArH), 7.73–
7.75 (m, 2H, ArH). 13C NMR (CDCl3, 75 MHz):
d16.34, 17.63,
4.3. General procedure for preparation of N-alkyl
phthalimide (7a–e, 8a, 8b)
25.69, 26.28, 35.73, 39.46, 118.00, 123.07, 123.82, 131.56,
132.36, 133.67, 140.53, 167.93. IR (cmÀ1, neat)
1085, 1171, 1395, 1653, 1711, 1770, 2929.
n: 946,
A mixture of phthalimide (4.8 mmol, 0.70 g), alkyl halide
(6.0 mmol), 4a or 4b (0.3 mmol, 3 mol%) and potassium
carbonate (18.8 mmol, 2.6 g) was heated in a commercial
microwave oven in an open Erlenmeyer flask at 60 8C–65 8C
for the required time (as shown in Table 3) according to a
50:10-s heating: cooling cycle, each at an 80% power level.
The completion of the reaction was monitored using TLC.
After cooling to r.t., the reaction mixture was extracted with
methylene chloride (2 Â 25 mL). Then the extracts were
dried over anhydrous Na2SO4, filtered, and the solvent was
evaporated to dryness to give the crude product. Solids were
purified through recrystallization in absolute EtOH, and
4.5.5. N-Benzyl succnimide (8a)
White solid. M. pt = 78–81 8C. 1H NMR (CDCl3, 300 MHz):
2.65 (s, 4H,–CO–[CH2]2–CO–), 4.61 (s, 2H,–N–CH2–Ar),
d
7.21–7.35 (m, 5H, ArH). 13C NMR (CDCl3, 75 MHz):
d
28.1,
42.3, 127.9, 128.6, 128.8, 135.2, 135.7, 176.8. IR (cmÀ1, neat)
: 1082, 1166, 1399, 1654, 1703, 1774, 2928.
n
4.5.6. N-Hexyl succinimide (8b)
Colourless oil. Bpt = 300 Æ 11 8C. [35b] 1H NMR (CDCl3,
300 MHz):
d
0.74–0.77 (m, 3H,–CH2–CH3), 1.15–1.17
(m, 6H,–(CH2)3–CH3), 1.43–1.45 (m, 2H,–N–CH2–CH2–), 2.59
Please cite this article in press as: Dogra S, et al. Comparative study of chemically immobilized and conventional
homogeneous ionic liquids as phase-transfer catalysts for the N-alkylation of heterocyclic compounds. C. R. Chimie