P.N. Muskawar et al. / Applied Catalysis A: General 482 (2014) 214–220
215
and solvents, the esterification reaction in presence of such ILs was
possible only in drastic conditions and at longer durations. Deriva-
tization of these ILs with desired functional groups can enhance the
ability of ILs as better extractants [33], catalysts [34–36] or solvents
and thus functionalized ILs have gained immense attraction among
the researchers.
J = 7.56 Hz), 7.68 (t, J = 7.74 Hz), 8.12 (m, 4H), 9.23 (bs, 2H), 10.00
(s, 2H). 13C NMR (400 MHz, DMSO-d ): ı = 10.58, 21.99, 38.45,
6
48.10, 48.58, 113.64, 113.87, 126.46, 126.62, 130.69, 131.71, 143.36,
−
1
165.02. FT-IR (KBr, ꢀ cm ): 3304, 3188, 3010, 2896, 2048, 1666,
1613, 1508, 1402, 1283, 1230, 1036, 752, 574. TOF MS (EI+) calcd
+
+
for C26H34Cl N O ; 497 [M–Cl] ; found 497 [M–Cl] .
2
6
2
In the present investigation, we focused on the synthesis of a
new series of amide functionalized dicationic benzimidazolium ILs
2
3
.3.2. Synthesis of
,3 -(2,2 -(hexane-1,6-diylbis(azanediyl))bis(2-oxoethane-2,1-
(
DBimILs) and explored their catalytic activity towards the syn-
ꢀ
ꢀ
thesis of alkyl/allyl/aryl ester derivatives. All the prepared ILs have
shown excellent catalytic activity with good yield under solvent
free conditions. Moreover, this is the first report on the separation
diyl))bis(1-propyl-1H-benzo[d]imidazol-3-ium) chloride
DBimIL-3b)
(
m.p. = 147 C, Yield = 83.45%, 1H NMR (400 MHz, DMSO-d ):
◦
6
of Et NHX (X = Cl/Br) salt from the reaction mixture, which is the
3
ı = 0.92 (t, J = 7.40 Hz, 6H), 1.28 (bs, 4H), 1.43 (bs, 4H), 1.95 (m, 4H),
.11 (t, J = 6.80 Hz, 4H), 4.55 (t, J = 7.0 Hz, 4H), 5.38 (s, 4H), 7.68 (d,
J = 8.60 Hz), 7.99 (m, 2H), 8.13 (m, 2H), 9.02 (s, 2H), 9.94 (s, 2H).
key step contributing for the catalyst recovery.
3
2
. Experimental
13
C NMR (400 MHz, DMSO-d ): ı 10.00, 22.03, 25.93, 28.7, 42.69,
6
4
1
1
8.11, 48.49, 113.61, 113.75, 126.53, 126.71, 130.75, 131.6, 143.3,
64.4. FT-IR (KBr, ꢀ cm ): 3383, 3238, 3088, 2960, 2938, 1684,
2
.1. Materials
−
1
568, 1433, 1382, 1259, 1195, 1083, 1033, 769, 613, 567. TOF MS
Benzimidazole, 1-bromopropane, 1,6-hexamethylene diamine
+
+
(EI+) calcd for C30H42Cl N O ; 553 [M–Cl] ; found 553 [M–Cl] .
2 6 2
were obtained from Sigma-Aldrich (India). Sodium hydride (60%),
tetrahydrofuran (specially dried), toluene (specially dried), n-
hexane, ethanediol, ethylene diamine, p-phenylene diamine,
p-toluene sulphonic acid (monohydrate), ethyl acetate, triethyl
amine, diethyl ether, dichloromethane, chloroform, sodium sul-
phate (anhydrous), sodium bicarbonate and all carboxylic acids
were purchased from SD Fine chemicals. Chloroacetyl chloride,
monochloroacetic acid and TLC plate Silica gel GF-254 were pro-
cured from Merck & Co. All the chemicals were used as received
unless it is specified.
The syntheses of catalysts 3c, 3d and 3e were carried out accord-
ing to literature [37]. The 3b (1 equivalent) was dissolved in distilled
water and aqueous solution of NaBF (2.1 equivalent) or NaPF (2.1
4
6
equivalent) or CF SO Li were added drop wise with constant stir-
3
3
ring for 15 min at room temperature. The reaction mixture was
allowed to stir for 5 h, after which the white solid 3c, 3d and 3f
precipitated out were collected by filtration and washed several
times with ethyl acetate over filter paper, finally dried in oven at
◦
6
0 C for 10 h.
ꢀ
ꢀ
2.2. Characterization techniques
2.3.3. 3,3 -(2,2 -(hexane-1,6-diylbis(azanediyl))bis(2-oxoethane-
2,1-diyl))bis(1-propyl-1H-benzo[d]imidazol-3-ium) tetrafluoro
All melting points and boiling points have been determined by
open capillary method and are uncorrected. NMR spectra were
borate (DBimIL-3c)
m.p. = 190 C, Yield = 89. 23%, 1H NMR (400 MHz, DMSO-d6):
ı = 0.93 (t, J = 7.14 Hz, 6H), 1.28 (bs, 4H), 1.43 (bs, 4H), 1.96 (m, 4H),
3.14 (t, J = 6.14 Hz, 4H), 4.55 (t, J = 6.93 Hz, 4H), 5.38 (s, 4H), 7.69 (t,
J = 8.60 Hz, 4H), 7.90 (q, 2H), 8.13 (t, 2H), 8.52 (t, J = 5.03 Hz, 2H),
9.75 (s, 2H). 13C NMR (400 MHz, DMSO-d6): ı 10.60, 22.04, 26.0,
28.85, 48.15, 48.43, 113.53, 113.78, 126.57, 126.75, 130.75, 131.67,
◦
recorded in DMSO-d , CDCl3 on a Bruker spectrometer operating
6
at 400 MHz and chemical shifts are given in ppm downfield from
TMS (ı = 0.00). FT-IR spectra were obtained from IR Affinity-1 Shi-
madzu FT-IR spectrophotometer using KBr pellets. Mass spectra of
all catalysts were recorded on a JEOL GC MATE II HRMS (EI) and
ESI–MS spectrometer and molecular weight of ester derivatives
were determined using Perkin Elmer GC model-Clarus 680 (EI). TGA
was recorded on TGA Q5000 V3.13 Build 261.
−
1
143.3, 164.36. FT-IR (KBr, ꢀ cm ): 3415, 3271, 3086, 2937, 1664,
1560, 1404, 1338, 1242, 779, 588. 19F NMR (400 MHz, DMSO-d6):
ı = 148.23.
2
.3. Synthesis and characterization of catalysts
ꢀ
ꢀ
2
2
.3.4. 3,3 -(2,2 -(hexane-1,6-diylbis(azanediyl))bis(2-oxoethane-
,1-diyl))bis(1-propyl-1H-benzo[d]imidazol-3-ium) hexafluoro
All the chloroacetyl of ethylene diamine, hexamethylene
phosphate (DBimIL-3d)
diamine, p-phenylene diamine and ethanediol as well as propyl
benzimidazole (see Supporting information, Schemes S1 and S2)
and the spectral data are matching with literature.
m.p. = 176 C, Yield = 98.12%, 1H NMR (400 MHz, DMSO-d ):
◦
6
ı = 0.93 (t, J = 7.35 Hz, 6H), 1.28 (bs, 4H), 1.44 (d, 4H), 1.97 (m,
H), 3.14 (q, J = 6.52 Hz, 4H), 4.54 (t, J = 6.97 Hz, 4H), 5.26 (s, 4H),
.70 (q, J = 8.60 Hz), 7.91 (q, 2H), 8.13 (t, 2H), 8.51 (s, 2H), 9.75 (s,
H). C NMR (400 MHz, DMSO-d ): ı 10.60, 22.04, 26.0, 28.84,
4
7
2
3
1
ꢀ
2
.3.1. Synthesis of 3,3 -((ethane-1,2-diylbis(azanediyl))bis(2-
13
6
oxoethane-2,1-diyl))bis(1-propyl-1H-benzo[d]imidazol-3-ium)
chloride (DBimIL-3a)
The synthesis of ionic liquids 3a, 3b and 3f was carried
out based on the literature procedure with minor modifications
8.95, 48.15, 48.44, 113.54, 113.77, 126.57, 126.75, 130.76, 131.68,
43.32, 164.37. 19F NMR (400 MHz, DMSO-d ): ı = −69.19, −71.07.
6
31
P NMR (400 MHz, DMSO-d ): ı = −157.36, −152.98, −148.59,
6
−
144.20, −139.81, −135.41, −131.03.
(Scheme 1.) [20]. 1-Propylbenzimidazole (2.1 equivalents) and rel-
evant chloroacetamide (2a/2b) or chloroacetate (2d) (1 equivalent)
was charged with toluene in a 100 mL round bottom flask and
the reaction mixture was stirred at 90 C for 48 h. The white vis-
ꢀ
ꢀ
2.3.5. 3,3 -(2,2 -(hexane-1,6-diylbis(azanediyl))bis(2-oxoethane-
2,1-diyl))bis(1-propyl-1H-benzo[d]imidazol-3-ium) trifluoro
methane sulphonate (DBimIL-3e)
◦
cous solid precipitate was washed repeatedly with ethyl acetate
and diethyl ether to remove unreacted residues and finally dried
◦
1
m.p. = 110 C, Yield = 95.87%, H NMR (400 MHz, DMSO-d ):
6
◦
in vacuum at 60 C for 2 h, to get pure white solid. Yield = 79.43%,
ı = 0.93 (t, J = 7.22 Hz, 6H), 1.29 (bs, 4H), 1.44 (bs, 4H), 1.94 (m, 4H),
3.13 (d, J = 5.88 Hz, 4H), 4.54 (t, J = 6.80 Hz, 4H), 5.27 (s, 4H), 7.69 (q,
J = 8.60 Hz, 4H), 7.91 (t, 2H), 8.12 (d, 2H), 8.51 (s, 2H), 9.76 (s, 2H).
◦
m.p. = 155 C.
1
H NMR (400 MHz, DMSO-d ): ı = 0.92 (t, J = 7.35 Hz, 6H), 1.94
6
13
(m, 4H,), 3.23 (s, 4H), 4.54 (t, J = 7.02 Hz, 4H), 5.44 (s, 4H), 7.59 (t,
C NMR (400 MHz, DMSO-d ): ı 10.58, 22.04, 26.0, 28.83, 38.95,
6