Cellulose-Supported Ionic Liquid Phase Catalyst-Mediated Mannich Reaction

Article abstract of DOI:10.1071/CH18576

Cellulose-supported ionic liquid phase (SILP) catalyst containing a camphor sulfonate anion with a pendant ferrocenyl group was prepared and characterised with different analytical techniques such as Fourier-transform infrared, Fourier-transform Raman, and cross polarization-magic angle spinning (CP-MAS) ¹³C NMR spectroscopy, X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis. The SILP catalyst displayed excellent catalytic activity in the synthesis of β-amino carbonyl compounds by Mannich reaction. Recycling studies revealed that SILP catalyst could be reused six times without significant decrease in catalytic activity.

Full text of DOI:10.1071/CH18576

CSIRO PUBLISHING
Aust. J. Chem.
Full Paper
https://doi.org/10.1071/CH18576
Cellulose-Supported Ionic Liquid Phase Catalyst-Mediated
Mannich Reaction
A
A
A
Sharanabasappa Khanapure, Megha Jagadale, Dolly Kale,
A
A B
,
Shivanand Gajare, and Gajanan Rashinkar
A
Department of Chemistry, Shivaji University, Kolhapur, 416004, India.
Corresponding author. Email: gsr_chem@unishivaji.ac.in
B
Cellulose-supported ionic liquid phase (SILP) catalyst containing a camphor sulfonate anion with a pendant ferrocenyl
group was prepared and characterised with different analytical techniques such as Fourier-transform infrared, Fourier-
transform Raman, and cross polarization–magic angle spinning (CP-MAS) 13C NMR spectroscopy, X-ray diffraction,
scanning electron microscopy, and thermogravimetric analysis. The SILP catalyst displayed excellent catalytic activity in
the synthesis of b-amino carbonyl compounds by Mannich reaction. Recycling studies revealed that SILP catalyst could be
reused six times without significant decrease in catalytic activity.
Manuscript received: 22 November 2018.
Manuscript accepted: 18 March 2019.
Published online: 30 April 2019.
Introduction
highly ordered crystal structure, making it insoluble in water as
well as in common organic solvents.[28] In addition, it is cheap,
non-toxic, insensitive to air and moisture, has a high surface
area and a limited carbon footprint as well as excellent biode-
gradability.[29–34] These versatile properties have stimulated
enormous interest in the use of cellulose as a support in the
synthesis of various heterogeneous catalysts.
The concept of supported ionic liquid phase (SILP) catalysis
involving immobilization of ionic liquids (ILs) over the surface
of porous, high-area support material has attracted enormous
attention in the field of sustainable organic synthesis.[1–6] This
novel class of advanced materials help to circumvent the
drawbacks associated with ILs such as high cost, toxicity, and an
energy-consuming distillation step for their recyclability and
reusability.[7,8] The synergistic combination of the advanta-
geous properties of ILs with those of support material enhances
the performance of SILP catalysts with retention of the prop-
erties of both the species. In addition, processes employing SILP
catalysts can be performed under unusual conditions using
fixed-bed reactor designs.[9,10] Moreover, SILP catalysts offer
unique benefits such as facile separation by filtration and
significant advances in activity as well as selectivity. These
fascinating properties of SILP catalysts have stimulated
researchers to design diversely functionalized SILP catalysts for
various organic transformations. Recent investigations have
revealed that the catalytic performance of SILP catalysts pri-
marily depends on the nature of the support material. In view of
this, a large number of diverse supports such as polymer-based
materials,[11–18] porous silica gels,[19,20] carbon nanotubes,[21]
active carbon cloth,[22] chitosan,[23] and magnetic nano-
particles[24] have been used in the preparation of SILP catalysts.
However, despite considerable progress, there is still scope to
prepare new SILP catalysts, especially employing biorenewable
feedstock-derived supports.
b-Amino carbonyl compounds are privileged scaffolds that
are used as intermediates in the synthesis of pharmaceuticals and
bio-active natural products such as antibiotics, amino alcohols,
peptides, and lactams.[35] In addition, they act as precursors to
optically active amino acids[36] and as building blocks to chiral
molecules.[37] Given their interesting applications, the synthesis
of b-amino carbonyl compounds plays a significant role both in
the drug discovery process and in organic synthesis. The classi-
cal method for the synthesis of b-amino carbonyl compounds
includes the Mannich reaction of aldehydes, ketones, and
amines. A large number of catalytic systems have been used
to increase the efficiency of the Mannich reaction.[38–43] How-
ever, many of the reported methods suffer from drawbacks such
as the use of expensive metal salts as catalysts, prolonged
reaction time, moisture sensitivity of the catalysts, and low
yields. Therefore, there is a need to develop an efficient protocol
using a highly efficient catalyst for the synthesis of b-amino
carbonyl compounds.
Incontinuationofourworkrelatedtogreenchemistry,[44,45] we
report herein the preparation of cellulose SILP catalyst containing
acamphorsulfonateanionwithapendantferrocenylgroup,andits
applicationasaheterogeneouscatalystinthesynthesisofb-amino
carbonyl compounds via the Mannich reaction.
Cellulose is the most abundant natural biopolymer obtained
from renewable agro-waste.[25–27] It is composed of long linear
chains of repeating units of b-D-glucose linked via 1,4-glyco-
sidic bonds. It has an unusual structure in which every glucose
monomer is linked with neighbouring units through hydrogen
bonds. As a result, cellulose chains are tightly packed to form a
Results and Discussion
The preparation of cellulose SILP catalyst containing a camphor
sulfonate anion with a pendant ferrocenyl group is outlined in
Journal compilation ꢀ CSIRO 2019
www.publish.csiro.au/journals/ajc

B
S. Khanapure et al.
Scheme 1. Initially, aluminium oxide (2) was finely dispersed on
the surfaceofcellulose (1) toobtainthe Cell–Al2O3 composite (3)
with high degree of adhesion following the literature proce-
dure.[46,47] The formation of stable Al–O–Si bonds through reac-
tion of Al–OH groups of 3 and Si–OEt groups of (3-chloropropyl)
triethoxy silane (4) resulted in the formation of chloropropyl
cellulose (5) with a significant degree of organofunctionalization.
The installation of IL-like units in the cellulose matrix was
achieved by quaternization of 1-N-ferrocenylmethyl benzimid-
azole (6) with 5 to yield a heterogeneous azolium salt given
the acronym [CellFemBenz]Cl (7), which on further treatment
with NH4OH formed [CellFemBenz]OH (8). Finally, the anion
metathesis reaction of 8 with (ꢀ)-10-camphorsulfonic acid
(CSA) (9) resulted in the formation of the desired cellulose-SILP
catalyst containing camphor sulfonate with a pendant ferrocenyl
group, denoted [CellFemBenz]CSA (10).
Fourier-transform (FT) Raman and FT-infrared (FT-IR) spec-
troscopy were used to monitor the progress of reactions involved
in the preparation of [CellFemBenz]CSA (10). The reaction of 3
with 4 was monitored by FT-Raman spectroscopy. The charac-
teristic vibrations at 1293 cmꢁ1 (wagging vibrations of CH2–Cl),
1094 cmꢁ1 (Si–O–C stretching vibrations), and 610 cmꢁ1 (C–Cl
stretching vibrations) indicate the formation of 5. Furthermore,
the FT-IR spectrum of 5 displayed characteristic peaks at
H2O, rt
Cell/
Al2O3
Cell
ϩ
·
AlCl3 6H2O
Cell–Al2O3 composite (3)
OEt
EtO Si
OEt
(2)
Cellulose (1)
Cl
Toluene, 100ЊC
(3-Chloropropyl)triethoxy silane (4)
O
Cell/
Al2O3
Cl
Si
O
OEt
3-Chloropropylcellulose (5)
DMF, 80ЊC
N
Fe
N
1-N-Ferrocenylmethyl benzimidazole (6)
Ϫ
Cell/
Al2O3
O
O
ϩ
Cl
N
N
Si
Fe
OEt
[CellFemBenz]Cl (7)
NH4OH
ϩ
O
O
Ϫ
Cell/
Al2O3
N
N
Fe
Si
OH
OEt
[CellFemBenz]OH (8)
HO3S
O
ϩ
-10-Camphorsulfonic acid (9)
Ϫ
.
Cell/
Al2O3
ϩ
O
O
N
N
Fe
Si
OEt
Ϫ
O3S
O
[CellFemBenz]CSA (10)
Scheme 1. Preparation of [CellFemBenz]CSA (10).

Cellulose-Supported IL Phase Catalyst
C
1341 cmꢁ1 (C–O stretching vibrations), 1175 cmꢁ1 (Si–O
stretching vibrations), 987 cmꢁ1 (C–C aliphatic stretching
vibrations), 891 cmꢁ1 (Si–C stretching vibrations), and
702 cmꢁ1 (C–Cl stretching vibrations) confirming the formation
of 5. The formation of [CellFemBenz]Cl (7) was monitored
by FT-Raman spectroscopy. The peaks at 3145 and 3108 cmꢁ1
(C–H stretching vibrations of cyclopentadienyl (Cp) rings),
1470, 1410, 1335, and 1256 cmꢁ1 (ring stretching modes of
benzimidazolium ring), and 460 cmꢁ1 (Fe–Cp stretching vibra-
tions) reflect successful installation of the IL-like unit in
the cellulose matrix of 5. This was further confirmed by the
FT-IR spectrum of 7, which displayed characteristic peaks at
1634 cmꢁ1 (C=C stretching vibrations of benzimidazolium
ring), 1428 cmꢁ1 (C–N stretching vibrations of benzimidazo-
lium ring), 2898, 1366, 1336, 1317 cmꢁ1 (Cp ring stretching
vibrations), and 471 cmꢁ1 (Cp–Fe stretching vibrations). The
anion metathesis of 7 with NH4OH to form [CellFemBenz]OH
(8) was monitored by FT-Raman spectroscopy. The appearance
of the characteristic stretching band of medium intensity of the
O–H group at 3432 cmꢁ1 revealed the replacement of Clꢁ by
OHꢁ. In addition, the FT-IR spectrum of 8 displayed a charac-
teristic peak at 3349 cmꢁ1 (O–H stretching vibrations) confirm-
ing its formation. The formation of [CellFemBenz]CSA (10)
was monitored by FT-Raman spectroscopy, which displayed
characteristic bands at 1744 cmꢁ1 (C=O stretching), 1092 cmꢁ1
(S–O stretching), and 703 cmꢁ1 (C–S aliphatic stretching). The
formation of 10 was further confirmed from the FT-IR spectrum,
which displayed characteristic peaks at 1746 cmꢁ1 (C=O
stretching vibrations of camphor sulfonate anion), 716 cmꢁ1
(C–S stretching vibrations of camphor sulfonate anion),
1009 cmꢁ1 (S–O stretching vibrations of camphor sulfonate
anion), and 2898 cmꢁ1 (C–H stretching vibrations of CH3
group). Additionally, the cross polarization–magic angle spin-
ning (CP-MAS) 13C NMR spectrum of [CellFemBenz]CSA (10)
displayed peaks at 155 ppm (C1 of benzimidazolium), 145 ppm
(C2 and C7 of benzimidazolium), 110 ppm (C4 and C5 of
benzimidazolium), 107 ppm (C3 and C6 of benzimidazolium),
90 ppm (broad singlet, C1 of cellulose), 83 ppm (singlet,
substituted Cp ring carbon of ferrocene), 75–72 ppm (multiplet,
C2, C3, C4, C5, C6 of cellulose), and 68 ppm (singlet,
non-substituted Cp ring carbon of ferrocene) confirming the
proposed structure of 10.
Energy-dispersive X-ray spectroscopy (EDX) and elemen-
tal analysis were used for quantification of the camphor
sulfonate anion in [CellFemBenz]CSA (10). Elemental analy-
sis revealed the presence of 0.077 mmol of camphor sulfonate
anion gꢁ1 of 10.
The thermal profile of [CellFemBenz]CSA (10) was studied
using thermogravimetric analysis (TGA) in the temperature
range 25–10008C (Fig. 1). The thermogram of 10 displayed an
initial weight loss of 5.6 % below 1008C due to the evaporation
of physically adsorbed water. The second major weight loss of
88.4 % up to 324 8C is ascribed to the combined weight loss of
the pendant ferrocenyl group and other organic scaffolds from
the cellulose matrix. The consequent weight loss of 5.0 % is
attributed to the decomposition of cellulose units through the
formation of volatile compounds. The observations are in good
agreement with the TGA profile of cellulose reported in the
literature.[48,49]
100
80
60
40
20
0
5.67 % (0.2427 mg)
To investigate morphological changes on the surface of the
cellulose support at various stages of preparation of the SILP
catalyst, field emission-scanning electron microscopy (FE-
SEM) was employed. The SEM images of cellulose (1), [Cell-
FemBenz]Cl (7), [CellFemBenz]OH (8), and [CellFemBenz]
CSA (10) are displayed in Fig. 2a–d. The images show no
alteration in the morphology of the cellulose support. The
fibrous morphology of cellulose, with diameters in the range
of several hundred micrometres, was retained even after multi-
step synthesis, revealing the effectiveness of cellulose as a
support in the preparation of the SILP catalyst.
88.41 % (3.781 mg)
5.037 % (0.2154 mg)
0
200
400
600
800
1000
Evidence for the retention of the microcrystalline nature of
cellulose (1) in [CellFemBenz]CSA (10) was investigated by
X-ray diffraction (XRD) analysis. The characteristic diffraction
peaks in the diffractogram indexed to the microcrystalline
Temperature [ЊC]
Fig. 1. Thermogravimetric analysis (TGA) curve for [CellFemBenz]CSA
(10).
(a)
(b)
(c)
(d)
20 kV ϫ 10000 1 µm
09 25 SEI
20 kV ϫ 10000 1 µm
10 25 SEI
20 kV ϫ 5000 5 µm
09 26 SEI
20 kV ϫ 10000 1 µm
09 26 SEI
Fig. 2. SEM images of (a) cellulose (1); (b) [CellFemBenz]Cl (7); (c) [CellFemBenz]OH (8); and (d) [CellFemBenz]
CSA (10).

D
S. Khanapure et al.
nature of 1 (Fig. 3). The characteristic peaks at 2y values of
15.068 and 22.488 being assigned to the reflections (1 0 1), (0 0 2)
by virtue of transverse arrangement of the crystallites in 1. A
pronounced peak at a 2y value of 34.258 correlates to the (0 4 0)
reflection, which is attributed to the longitudinal structure of the
polymer. Thus, XRD analysis revealed preservation of the
microcrystalline structure of 1 in 10 even after multistep
functionalization.[50]
Our next task was to investigate the catalytic potential of
[CellFemBenz]CSA (10) in the Mannich reaction. In order to
optimize reaction parameters, the reaction between acetophe-
none (11a), benzaldehyde (12a), and aniline (13a) was chosen as
a model reaction. Initially, the effect of various solvents on the
model reaction was studied, and results are summarised in
Table 1. Ethanol was found to be the most effective solvent,
providing the highest yield of 1,3-diphenyl-3-(phenylamino)
propan-1-one (Table 1, entry 4). In contrast, solvent-free con-
ditions as well as solvents such as H2O, MeOH, CH2Cl2,
CH3CN, THF, DMF, toluene, and CHCl3 resulted in compara-
tively lower yields (Table 1, entries 1–3, 5–10).
Next, the effect of catalytic loading was investigated. The
model reaction was tested by varying the amount of 10 in
ethanol at ambient temperature and the results are summarised
in Table 2. In the absence of catalyst, reaction did not proceed
even after a prolonged reaction time of 24 h (Table 2, entry 1),
whereas in the presence of 10, a significant improvement in the
yield of corresponding product 14a was observed. It was found
that 0.05 g of 10 was sufficient to efficiently drive the model
reaction to afford the desired product in excellent yield (92 %)
within 5 h (Table 2, entry 6). Further, we noted that amounts less
than 0.05 g gave lower yields (Table 2, entries 1–5), whereas
increasing the catalyst quantity beyond this value did not lead to
any significant improvement in the yield (Table 2, entries 7–9).
The next parameter investigated was the reaction temperature
(Table 2). The model reaction performed in ethanol with 0.05 g of
10 at room temperature gave the best result (Table 2, entry 6). No
improvement in the yield of product was observed when the
reaction temperature was increased (Table 2, entries 10–13).
Thus, 0.05 g of catalyst, ethanol as solvent, and room temperature
were selected as optimum reaction conditions for further studies.
After the optimization of reaction conditions, the generality
of the protocol was investigated by reacting structurally diverse
aldehydes, amines, and acetophenones. The results summarised
in Table 3 indicate that the electronic effect of substituents on
the reactants has a significant impact on the yield of products. It
is seen that electron-donating groups on ketones resulted in
better yields (Table 3, entries 11b, c) as compared with electron-
withdrawing groups (Table 3, entry 11e). Further, the electron-
donating group-substituted amines afforded the corresponding
products in better yields than electron-withdrawing group-
substituted amines (Table 3, entries 11j and 11i). Moreover,
the reaction was found to be sensitive to steric hindrance as well
as electronic effect of the substituents. Orthosubstituted reac-
tants produced moderate yields of corresponding product owing
to the steric effect (Table 3, entries 11d, 13g, and 13k).
(0 0 2)
[CellFemBenz]CSA (10)
Cellulose (1)
(1 0 1)
(0 4 0)
10
20
30
40
50
60
A plausible mechanism for the [CellFemBenz]CSA (10)
catalyzed Mannich reaction is depicted in Scheme 2 and is
based on the report by Ishikawa et al.[51] The presence of the
bulky camphor sulfonate anion and cylindrical ferrocenyl
2q [deg.]
Fig. 3. XRD of cellulose (1) and [CellFemBenz]CSA (10).
Table 1. Optimization of solvent in [CellFemBenz]CSA (10)-catalyzed Mannich reactionA
O
O
Ph
NH2
CHO
[CellFemBenz]CSA (10)
CH3
NHPh
ϩ
ϩ
Solvent
11a
12a
13a
14a
Entry
Solvents
YieldB [%]
1
Solvent-free
H2O
67
74
2
3
MeOH
EtOH
81
4
92
5
CH2Cl2
CH3CN
THF
62
6
72
7
48
8
DMF
51
9
Toluene
CHCl3
Trace
57
10
AReaction conditions: acetophenone (1 mmol), benzaldehyde (1 mmol), aniline (1 mmol), [CellFem-
Benz]CSA (0.05 g), solvent (5 mL), rt, 5 h.
BIsolated yields after chromatography.

Cellulose-Supported IL Phase Catalyst
E
group[52–57] on the cation in 10 results in weaker coulombic
interactions between cation and anion. This keeps the cation and
anion as far as away from each other. Further, as the solvent used
for this reaction is ethanol, which is polar, it is capable of
solvating the hydrophobic camphor sulfonate anion, which is
already at a distance from the cation owing to its bulky nature.
This frees the [CellFemBenz] cation. This facilitates favourable
H-bonding interaction between the proton of C2 of the benzi-
midazolium cation in 10 and the carbonyl group of the aldehyde
(III). This assists the nucleophilic attack of the amine II on the
activated aldehyde III to form the iminium cation IV. Further,
the enol V formed via tautomerization of ketone I reacts with IV,
furnishing the desired product VI. The proposed mechanism
is supported by the fact that when [CellFemBenz]Cl (7) and
[CellFemBenz]OH (8) were used as catalysts, the model reac-
tion did not proceed to a synthetically useful degree as the yield
of corresponding product was 52 and 61 % respectively, indi-
cating the role of the camphor sulfonate anion is important.
To confirm the heterogeneity of [CellFemBenz]CSA (10), a
hot filtration test was carried out for the model reaction. After
50 % conversion (by gas chromatography), the reaction mixture
was split into two parts by simple filtration, and both reaction
mixtures were stirred for an additional 3 h. The mixture contain-
ing 10 proceeded to completion whereas the other portion
without 10 did not show any increase in the yield of product
beyond 50 % (14a). This indicates that almost all IL-like units
containing the camphor sulfonate anion are significantly embed-
ded in the crystalline framework of the cellulose support,
thereby making the catalyst leaching-resistant for good regen-
eration and reusability.
It is noteworthy that the FT-Raman spectra of both fresh and
reused [CellFemBenz]CSA (10) revealed the same functional
groups even after six successive cycles. Further, EDX analysis
of reused catalyst indicated no significant difference in compo-
sition in comparison with the fresh catalyst. Moreover, the SEM
images of both fresh and reused catalysts (Fig. 5a, b) indicates
that the morphology of the catalyst is preserved after six
successive runs. The results reveal that 10 is stable and does
not undergo physical or chemical changes during recycling and
after multiple reuse.
To demonstrate the merits of the present protocol, we
compared the efficiency of [CellFemBenz]CSA (10) with some
of the reported catalysts used in the synthesis of 1,3-diphenyl-
3-(phenylamino)propan-1-one (14a) by Mannich reaction
between acetophenone (11a), benzaldehyde (12a), and aniline
(13a). The results are summarised in Table 4. It is evident that 10
is superior to many of the reported catalysts with respect to
either loading, temperature, time, or yield of the product.
Conclusion
Cellulose SILP catalyst containing a camphor sulfonate anion
with a pendant ferrocenyl group was prepared and its catalytic
efficiency evaluated in the synthesis of b-amino carbonyl
compounds via Mannich reactions of aldehydes, amines, and
acetophenones. The present strategy offers several key features
such as low catalyst loading, remarkable catalytic performance,
ability to work at ambient temperature, flexibility in the syn-
thesis, clean reaction profile, easy work-up procedure, and facile
recyclability and reusability of catalyst. Studies aimed at
extending the scope of the cellulose SILP catalyst containing a
camphor sulfonate anion for other organic transformations are
currently under way in our laboratory.
The recyclability and reusability of [CellFemBenz]CSA (10)
were investigated for the model reaction under the optimized
reaction conditions. On completion of the reaction, the catalyst
was filtered, washed with copious amount of ethanol to remove
any adhering reactants, and dried at 608C under vacuum for 1 h.
The recovered catalyst was reusedfor six subsequentrunswithout
noticeable drop in product yield and catalytic activity (Fig. 4).
Experimental
General Remarks
All the starting reagents, solvents, and cellulose were of stan-
dard analytical grade, purchased from local suppliers, and used
Table 2. Optimization of catalyst loading in [CellFemBenz]CSA (10)-promoted Mannich reactionA
O
O
Ph
NH2
CHO
[CellFemBenz]CSA (10)
CH3
NHPh
ϩ
ϩ
Ethanol, rt
11a
12a
13a
14a
Entry
Catalyst [g]
Temperature [8C]
Time [h]
YieldB [%]
1
No catalyst
0.01
rt
rt
24.0
7.5
7.0
6.5
5.5
5.0
5.0
4.5
4.0
4.5
4.0
3.5
3.5
None
56
69
76
83
92
93
94
94
93
93
94
94
2
3
0.02
rt
4
0.03
rt
5
0.04
rt
6
0.05
rt
7
0.06
rt
8
0.07
rt
9
0.08
rt
10
11
12
13
0.05
40
50
60
80
0.05
0.05
0.05
AReaction conditions: acetophenone (1 mmol), benzaldehyde (1 mmol), aniline (1 mmol), ethanol (5 mL), rt.
BIsolated yields after chromatography.

F
S. Khanapure et al.

Cellulose-Supported IL Phase Catalyst
G

H
S. Khanapure et al.
without further purification. (ꢀ)-10-Camphorsulfonic acid was
purchased from Sigma–Aldrich Co. and was used as received.
All reactions were carried out under air in dried glassware.
Infrared spectra were measured with a PerkinElmer One FT-IR
spectrophotometer. The samples were examined as ,5 % w/w
KBr discs. Raman spectroscopy was carried out using a Bruker
FT-Raman MultiRAM spectrometer. The elemental composi-
tion of materials was analysed by EDS attached to a field-
emission scanning electron microscope (Hitachi S 4800). 1H and
13C NMR spectra were recorded on a Bruker AC (300 MHz for
1H NMR and 75 MHz for 13C NMR) spectrometer using CDCl3
as solvent and tetramethylsilane (TMS) as internal standard.
Chemical shifts, d, are expressed in parts per million (ppm) and
coupling constants are expressed in hertz (Hz). The CP-MAS
13C NMR spectrum was recorded with a Jeol-ECX400 type FT-
NMR spectrometer under prescribed operating conditions. Mass
spectra were recorded on a Shimadzu QP2010 GCMS. The
materials were analysed by SEM using a Jeol JSM with 5 and
20 kV accelerating voltage. Melting points were determined
on a MEL-TEMP capillary melting point apparatus and are
uncorrected. 1-N-Ferrocenylmethyl benzimidazole was syn-
thesised following the literature procedure.[58]
Preparation of Cell–Al2O3 Composite (3)
A mixture of microcrystalline cellulose (1) (15 g) and alumin-
ium chloride hexahydrate (2) (15 g) in water (200 mL) was
stirred for 12 h. Then, the mixture was filtered, and the residue
was exposed to ammonia. It was then washed with water and
dried under vacuum at room temperature to get the Cell–Al2O3
composite (3). By calcining 2 (0.300 g) at 6008C for 8 h, the
amount of aluminium was determined and the residue, weighed
as Al2O3, was found to be 3.28 wt-%, corresponding to
0.69 mmol aluminium gꢁ1 of 3.
Preparation of Chloropropyl Cellulose (5)
A mixture of 3 (10.0 g) and (3-chloropropyl)triethoxysilane (4)
(9.6 mL, 40.0 mmol) in toluene (10 mL) was refluxed in an oil
bath for 24 h. The reaction mixture was cooled, filtered, and the
product was washed with toluene (3 ꢂ 5 mL) and dried under
.
Ϫ
Cell/
Al2O3
ϩ
O
O
N
Si
N
Fe
O3S
O
OEt
H
O
(10)
[CellFemBenz]CSA
Cell/
Al2O3
H
CH2
ϩ
O
O
.
N
N
Fe
Si
Ϫ
I
OEt
O3S
O
H
R3
[CellFemBenz]CSA (10)
R2
R1
..
O
NH2
H
II
III
H
N
R1
R2
OH2
ϩ
O
H
H2O
CH2
ϩ
H
N
R3
V
R1
IV
R2
R1
O
R2
NH
VI
Scheme 2.

Cellulose-Supported IL Phase Catalyst
I
vacuum at room temperature for 8 h to afford chloropropyl
cellulose (5). FT-IR nmax (KBr, thin film)/cmꢁ1 3345, 2906,
1635, 1426, 1341, 1175, 1171, 987, 891, 702, 579. Raman nmax
(KBr)/cmꢁ1 2898, 1481, 1375, 1293, 1117, 1094, 898, 610, 519,
381. Elemental analysis found (%): C 73.00, O 23.07, Al 1.84, Cl
2.09 %. Loading: 0.59 mmol functional group gꢁ1 of 5.
dried under vacuum at 508C for 24 h to produce 7. FT-IR nmax
(KBr, thin film)/cmꢁ1 2898, 1634, 1428, 1366, 1336, 1317,
1163, 471. Raman nmax/cmꢁ1 3145, 3108, 1637, 1578, 1470,
1410, 1335, 1256, 1157, 775, 710, 645, 521, 460. Anal. found: C
39.68, N 1.59, H 5.90 %. Loading: 0.56 mmol benzimidazolium
units gꢁ1 of 7.
Preparation of [CellFemBenz]Cl (7)
Preparation of [CellFemBenz]OH (8)
A mixture of 5 (7.0 g) and 1-N-ferrocenylmethyl benzimidazole
(6) (4.3 g, 10 mmol) in DMF (25 mL) was heated at 808C in an
oil bath for 72 h. The solid was filtered, washed with DMF
(3 ꢂ 50 mL), MeOH (3 ꢂ 50 mL), and CH2Cl2 (3 ꢂ 50 mL), and
A mixture of 7 (5.0 g) and an aqueous solution of NH3 (30 mL)
was stirred for 48 h at room temperature. Afterwards, the solid
was filtered and washed with MeOH (3 ꢂ 20 mL), MeOH/H2O
(1 : 1) (3 ꢂ 20 mL), H2O (3 ꢂ 20 mL), and MeOH (3 ꢂ 20 mL),
and then dried under vacuum at 508C for 48 h to get [Cell-
FemBenz]OH (8). The quantification of hydroxyl groups in 8
was carried out by volumetric titration [59,60] and was found to be
0.23 mmol gꢁ1 of 8. FT-IR nmax (KBr, thin film)/cmꢁ1 3349,
2905, 1634, 1432, 1360, 1317, 1162, 1105, 1027, 605. Raman
nmax (KBr)/cmꢁ1 3432, 3110, 1744, 1640, 1578, 1472, 1410,
1335, 1260, 1160, 776, 710, 703, 521, 460. Anal. found: C 61.29,
N 0.90, Al 1.19, Si 0.24, Fe 0.27 %. Loading: 0.23 mmol OH
groups gꢁ1 of 8.
100
92 %
92 %
91 %
89 %
89 %
90
80
70
60
50
40
30
20
10
84 %
Preparation of [CellFemBenz]CSA (10)
[CellFemBenz]OH (3.0 g) was stirred in (ꢀ)-CSA (9) (0.05 M,
50 mL) at room temperature for 48 h. Afterwards, the mixture
was filtered and the residue was washed with CH2Cl2
(3 ꢂ 20 mL) and H2O (3 ꢂ 20 mL), and dried under vacuum
for 48 h to afford [CellFemBenz]CSA complex (10). FT-IR nmax
(KBr, thin film)/cmꢁ1 3373, 2898, 2829, 2115, 1746, 1645,
1
2
3
4
5
6
No. of cycles
Fig. 4. Recyclability study of [CellFemBenz]CSA (10) in the synthesis of
1,3-diphenyl-3-(phenylamino)propan-1-one (14a).
(a)
(b)
20 kV
09 26 SEI
20 kV
09 25 SEI
ϫ 10000
ϫ 5000
1 µm
5 µm
Fig. 5. FE-SEM images of (a) fresh [CellFemBenz]CSA (10); and (b) reused [CellFemBenz]CSA (10).
Table 4. Comparative studies of [CellFemBenz]CSA (10) in the synthesis of 14a
Entry
Catalyst
Amount of catalyst
Temperature [8C]
Time [h]
Yield [%]
Ref.
1
2
3
4
5
6
7
8
CFPIL-1
0.032 g
0.080 g
rt
308C
658C
rt
5
24
10
18
3.45
11
4
70
75
83
76
90
95
88
92
[38]
[39]
PS-SO3H
Yttria–zirconia-based Lewis acid
H3PW12O40
10 mol-%
0.691 g
[40]
[41]
Carbon-based solid acid
BiCl3
0.10 g
rt
[42]
5 mol-%
5 mol-%
1.63 mol-%
rt
[43]
(ꢀ)-10-Camphorsulfonic acid
[CellFemBen]CSA/EtOH
rt
[61]
rt
5
Present work

J
S. Khanapure et al.
1434, 1009, 716. Raman nmax (KBr)/cmꢁ1 3110, 2890, 1745,
1619, 1577, 1480, 1410, 1256, 1092, 779, 703, 645, 521, 465.
Anal found: C 37.81, H 5.63, N 0.23, S 0.58. Loading:
0.077 mmol of camphor sulfonate anion gꢁ1 of 10.
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S. V. Luis, M. Pawlak, Chem. – Eur. J. 2011, 17, 1894. doi:10.1002/
CHEM.201001873
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J.REACTFUNCTPOLYM.2010.11.001
General Procedure for the Synthesis of b-Amino Carbonyl
Compounds
A mixture of aldehyde (1 mmol), aniline (1 mmol), acet-
ophenone (1 mmol), and [CellFemBenz]CSA (10) (0.05 g) was
stirred in ethanol (5 mL) at ambient temperature for the
appropriate time indicated in Table 3. On completion of the
reaction as monitored by TLC, the reaction mixture was fil-
tered to recover the insoluble catalyst. The reaction mixture
was then evaporated at room temperature (rt). The resulting
crude product was washed with ethanol and purified by column
chromatography over silica gel using 10 % ethyl acetate
and 90 % light petroleum as an eluent to yield pure b-amino
carbonyl compounds.
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Supplementary Material
Spectral data of synthesised b-amino carbonyl compounds are
available on the Journal’s website.
Conflicts of Interest
125, 85. doi:10.1016/J.CARBPOL.2015.02.054
[29] A. Mohammadinezhad, M. A. Nasseri, M. Salimi, RSC Adv. 2014, 4,
39870. doi:10.1039/C4RA06450J
The authors declare no conflicts of interest.
[30] A. Shaabani, Z. Hezarkhani, S. Shaabani, RSC Adv. 2014, 4, 64419.
doi:10.1039/C4RA11101J
[31] D. Baruah, U. P. Saikia, P. Pahari, D. K. Dutta, D. Konwar, RSC Adv.
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B007776N
Acknowledgements
We gratefully acknowledge the Indian Institute of Sciences (IISc), Banga-
lore, and Sophisticated Analytical Instrumental Facility, Indian Institute of
Technology, Madras (IITM), for providing spectral facilities. This research
did not receive any specific funding.
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