Microwave-assisted expeditious approach towards benzimidazole acrylonitrile derivatives exploring a new silica supported SBPTS catalyst

Article abstract of DOI:10.1039/c8nj01436a

The present study reports a simple, highly efficient and green approach for the synthesis of a series of benzimidazole-acrylonitrile derivatives 3(a-l). The synthetic methodology involves a microwave-assisted reaction exploring novel silica-supported SBPTS as a heterogeneous, proficient and reusable catalyst resulting in excellent yields. The reaction transformation presumably occurs via a Knoevenagel condensation. The significant features of the present protocol includes a simple operational procedure, shorter reaction times, mild reaction conditions, economic viability, high yield of products and compatibility with a range of functional groups (electron donating/electron withdrawing).

Full text of DOI:10.1039/c8nj01436a

View Article Online
View Journal
NJC
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: F. Ahmad and M.
Parveen, New J. Chem., 2018, DOI: 10.1039/C8NJ01436A.
This is an Accepted Manuscript, which has been through the
Volume 40 Number
1 January 2016 Pages 1–846
Royal Society of Chemistry peer review process and has been
accepted for publication.
NJC
Accepted Manuscripts are published online shortly after
New Journal of Chemistry
www.rsc.org/njc
A journal for new directions in chemistry
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 1144-0546
PAPER
Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
diarylethene-based metal–organic frameworks
rsc.li/njc

Page 1 of 30
New Journal of Chemistry
Microwave assisted expeditious approach towards benzimidazole acryloDnOitI:r10il.1e03V9ie/wC8ArNticJl0e1O4n3l6inAe
derivatives exploring new silica supported SBPTS catalyst
Faheem Ahmad,a,b,* Mehtab Parveena,*
aDepartment of Chemistry, Aligarh Muslim University, Aligarh, 202002, India
bSchool of Chemical Engineering, Chonbuk National University, Jeonju 54896,, Republic of
Korea
Abstract
The present study reports a simple, highly efficient and green approach for the synthesis of a
series of benzimidazole-acrylonitrile derivatives 3 (a-l). The synthetic methodology involves
a microwave-assisted reaction exploring novel silica-supported SBPTS as a heterogeneous,
proficient and reusable catalyst resulting in excellent yields. The reaction transformation
presumably occurs via Knoevenagel condensation. The significant features of the present
protocol includes simple operational procedure, shorter reaction times, mild reaction
conditions, economic viability, high yield of products and compatibility to a range of
functional groups (electron donating/electron withdrawing).
Keywords: SBPTS catalyst; benzimidazole-acrylonitrile; microwave; Knoevenagel
condensation
Corresponding authors email address:
*mehtab.organic2009@ gmail.com (Prof. M. Parveen)
*mirzafaheem.org@gmail.com (Dr. F. Ahmad)

New Journal of Chemistry
Page 2 of 30
View Article Online
DOI: 10.1039/C8NJ01436A
1.
Introduction
In the last few decades catalysis is prove to be a key for sustainable synthetic chemistry and
turned out to be a major area of research in synthetic organic chemistry satisfying green
chemistry principle.1-5 This clean technology in synthetic chemistry motivates researcher to
improvise the classical methods with suitable alternate catalytic systems for easy chemical
transformations with the minimum generation of chemical wastes and environmental
pollution.6-9 In this regards heterogeneous solid acid catalyst proves to be blessing for organic
chemist because of their exclusive properties such as well-defined structure, bronsted acidity,
high mechanical and thermal stability, higher efficiency, larger surface area, better selectivity,
non-corrosiveness, eco-friendly, and economically feasible nature for both environmental and
commercial point of view.10-12, In recent era of catalyst assisted organic synthesis, silica is the
ubiquitous platform used for designing efficient catalysts due to the favourable chemical and
physical properties of silica surfaces which impart varieties of reactive functional group to its
surface through well-known silane chemistry.13,14 As a result, varieties of silica supported
catalyst with enhanced chemical functionality were reported possessing efficient catalytic
properties.15-19
Nitrogen containing heterocyclic compound becomes the hottest topics in the organic
chemistry research due to its extensive presence in various bioactive natural compounds,
pharmaceuticals and synthetic intermediates.20 Benzimidazoles are ubiquitous scaffold,
constitutes an important part of the vitamin B12 and structurally similar to purine which
helped it to inhibit the bacterial growth.21 Benzimidazole derivatives are currently under
intensive focus due to their wide range of applications in pharmaceuticals, material and
synthetic chemistry. Literature survey revealed that benzimidazole derivatives possess various
biological properties viz., antioxidant, antimicrobial, anti-inflammatory, antiviral, antitumor,
anticancer, anti-helmintic, antihistamine, antihypertensive, antineoplastic, anti-analgesic,

Page 3 of 30
New Journal of Chemistry
antidiabetic, lipase inhibition, and glucosidase inhibitions etc.22-30 Some widely used drugs
View Article Online
DOI: 10.1039/C8NJ01436A
with benzimidazole nucleus such as Rabeprazole, Pimozide, Mebendazole and Telmisartan
are currently in clinical use. Thus, benzimidazole nucleus is considered as an indispensable
anchor for the discovery of new biologically active agents. Apart from being biologically
active, it also established its utility in agrochemicals, luminescent materials, fuel cells, ionic
liquids, organic ligands, dye sensitized solar cells, chemosensors, and in corrosion science.31-
38
Owing to its versatile applicability, functionalization of benzimidazole scaffold with
different functional groups has been attracted significant interest.
In the past few years, much attention has been paid to the acrylonitrile derivatives due to
their predominant application as intermediates for the synthesis of various bioactive
compounds possess wide range of biological properties such as antiproliferative,
antimicrobial, antioxidative, anticholinesterase, antitumor, estrogenic, spasmolytic,
tuberculostatic, and antitrichomonal properties.14,39-47 Till now, the Knoevenagel condensation
is a simple and efficient approach for the derivatives of acrylonitrile.48 This involves the acid
or base-catalyzed condensation of carbonyl compounds with active methylene moieties. In the
pursuit to achieve higher efficiency, numerous catalysts with different reaction conditions
were employed, including Brønsted acid catalysts,49 Lewis acids such as Al2O3,50 SnCl2,51
MgBr2·OEt2,52 ionic liquids viz. [Bpy]Cl·xAlCl3,53 [Bmim]BF4,54 [Bmim]Cl·xAlCl3,53
ethylammonium nitrate55 and silica supported acid catalyst.14,56
Prompted by the promising activities of benzimidazole analogues and acrylonitrile
derivatives, we herein report an easy and proficient microwave-assisted synthesis of
benzimidazole-acrylonitrile derivatives exploring novel silica supported catalyst, silica boron-
p-toluene sulfonate (SBPTS) as a green, efficient and recyclable catalyst for Knoevenagel
condensation. To the best of our knowledge, it is the first report of the catalyst and its use for
the synthesis of benzimidazole-acrylonitrile derivatives.

New Journal of Chemistry
Page 4 of 30
View Article Online
DOI: 10.1039/C8NJ01436A
2.
Experimental
2.1. Materials and general methods
All the reagents used were purchased from Sigma-Aldrich (India), as ‘synthesis grade’ and
used without further purification. The microwave synthesis was performed in Anton Paar
Monowave 300 microwave synthesizer. Fourier transform-infrared (FT-IR) spectra were
recorded using a Perkin-Elmer (2000 FTIR) Spectrometer by the KBr pellet method in the
wave-number range of 400-4000 cm-1. 1H NMR (400 MHz) and 13C NMR (100 MHz) spectra
were recorded on a Bruker Avance-II instrument in pure deuterated DMSO-d6 solvent. The
chemical shifts (δ) are reported in ppm value relative to the TMS as an internal standard.
Elemental analysis was conducted using a Thermo Scientific (FLASH 2000) CHN Elemental
Analyser. Mass spectra were recorded on a JEOL D-300 mass spectrometer. X-ray
diffractograms (XRD) of the catalyst were recorded in the 2θ range of 20-80ᵒ with a scan rate
of 4ᵒ min-1 on a Shimadzu-6100 X-ray diffractometer with Ni-filtered Cu Ka radiation at a
wavelength of 1.54060 Å. The scanning electron microscope (SEM) analysis was obtained
using a JEOL (JSM-6510) equipped with an energy dispersive X-ray (EDX) spectrometer at
different magnification and transmission electron microscope (TEM) results were recorded
using a JEOL (JEM-2100F) model. TGA/DTA has been carried out with DTG-60H Shimadzu
(simultaneous DTA-TG) apparatus. The purity of all the compounds and progress of the
reaction was checked by thin layer chromatography (TLC) on silica gel G254 (E-Merck)
coated glass plates and exposed to iodine vapours.
2.2. Synthesis of catalyst
2.2.1. Preparation of Silica supported boric acid (SBA)
In a 250 mL round bottom flask, boric acid (3.0 g) was taken with 60 mL water and heated to
60-80 °C. Silica gel (60-120 mesh, 27.0 g) was added slowly with constant stirring and
refluxed for about 5 h. After that water was evaporated under reduced pressure and the

Page 5 of 30
New Journal of Chemistry
View Article Online
residue was stirred at 100 °C for 6-7 h under vacuum to give free flowing whitDeOpI: o10w.10d3e9/rC8oNfJ01436A
silica-boric acid.15
2.2.2.Preparation of SBPTS catalyst
A 500 mL suction flask fitted with a constant pressure dropping funnel containing p-
toluenesulfonyl chloride solution (7.64 g, in 100 mL ethanol) and a gas inlet tube for
conducting HCl gas over an absorbing solution (water). It was charged with SBA (10.0 g) and
p-toluenesulfonyl chloride (PTSC) solution was added drop wise over a period of 60 min at
room temperature, evolution of profuse amounts of HCl occurred instantaneously. After, the
addition was completed, the mixture was stirred under vacuum pressure for 30 min and a
white solid of SBPTS catalyst (14.8 g) were obtained.57
2.3. General procedure for the synthesis of acrylonitrile derivatives
To a mixture of benzimidazole-2- acetonitrile 1 (2.0 mmol) and aromatic aldehydes 2 (a-l)
(2.0 mmol) in absolute ethanol (10 mL), SBPTS catalyst (10 mol%) was added and the
reaction mixture was irradiated with continuous stirring in a microwave synthesis reactor
o
(Anton Paar, Monowave 300) at 70 C for 10-12 min. After completion of the reaction, as
evident by TLC, the reaction mixture was filtered to recover the catalyst and washed with
ethanol. The reaction mixture was then poured into ice water and the resulting precipitate was
filtered to afford crude product and purified by column chromatography with
dichloromethane-hexane to get the pure compound.
2.4. Spectral Characterization
(E)-2-(1H-benzo[d]imidazol-2-yl)-3-(4-(dimethylamino)phenyl)acrylonitrile (3a)58
Anal. calc. for C18H16N4: C, 74.98; H, 5.59; N, 19.43; found: C, 74.75; H, 5.63; N, 19.36. FT-
1
IR (KBr, cm-1): 3340, 3078, 3045, 2980, 2216, 1645, 1625, 1570. H NMR (400 MHz,
DMSO-d6, δ, ppm): 12.16 (s, 1H, -NH), 8.19 (s, 1H, =CH), 7.81 (d, 2H, H-4 and H-7), 7.44-

New Journal of Chemistry
Page 6 of 30
View Article Online
7.52 (m, 2H, H-5 and H-6), 7.72 (d, 2H, H-2′ and H-6′), 6.71 (d, 2H, H-3′ and HD-5OI′:)1,03.10.0399/C(8sN,J01436A
6H, -CH3). 13C NMR (100 MHz, DMSO-d6, δ, ppm): 143.5 (C-2), 137.8 (C-3a and C-7a),
116.9 (C-4 and C-7), 122.6 (C-5 and C-6), 108.7 (C-1″), 153.5 (C-2″), 119.4 (C≡N), 124.7
(C-1′), 130.1 (C-2′ and C-6′), 113.2 (C-3′ and C-5′), 151.6 (C-4′), 43.3 (CH3). MS (ESI) m/z:
288.16 [M] +•.
(E)-2-(1H-benzo[d]imidazol-2-yl)-3-(4-fluorophenyl)acrylonitrile (3b)
Anal. calc. for C16H10FN3: C, 72.99; H, 3.83; N, 15.96; found: C, 72.95; H, 3.79; N, 15.99.
1
FT-IR (KBr, cm-1): 3375, 3082, 3066, 2218, 1642, 1638, 1518, 1118. H NMR (400 MHz,
DMSO-d6, δ, ppm): 12.17 (s, 1H, -NH), 8.05 (s, 1H, =CH), 7.79 (d, 2H, H-4 and H-7), 7.49-
54 (m, 2H, H-5 and H-6), 7.68 (d, 2H, H-2′ and H-6′), 7.19 (d, 2H, H-3′ and H-5′). 13C NMR
(100 MHz, DMSO-d6, δ, ppm): 144.3 (C-2), 139.7 (C-3a and C-7a), 117.2 (C-4 and C-7),
125.1 (C-5 and C-6), 109.9 (C-1″), 155.8 (C-2″), 120.7 (C≡N), 131.8 (C-1′), 130.4 (C-2′ and
C-6′), 115.4 (C-3′ and C-5′), 160.3 (C-4′). MS (ESI) m/z: 263.06 [M]+•.
(E)-2-(1H-benzo[d]imidazol-2-yl)-3-(4-nitrophenyl)acrylonitrile (3c)
Anal. calc. for C16H10N4O2: C, 66.20; H, 3.47; N, 19.30; found: C, 66.17; H, 3.50; N, 19.34.
1
FT-IR (KBr, cm-1): 3394, 3076, 3046, 2221, 1646, 1632, 1535, 1512, 1340. H NMR (400
MHz, DMSO-d6, δ, ppm): 12.06 (s, 1H, -NH), 8.27 (s, 1H, =CH), 7.84 (d, 2H, H-4 and H-7),
7.52-7.60 (m, 2H, H-5 and H-6), 8.03 (d, 2H, H-2′ and H-6′), 8.15 (d, 2H, H-3′ and H-5′). 13C
NMR (100 MHz, DMSO-d6, δ, ppm): 144.2 (C-2), 140.1 (C-3a and C-7a), 117.2 (C-4 and C-
7), 124.8 (C-5 and C-6), 108.9 (C-1″), 154.9 (C-2″), 119.2 (C≡N), 142.7 (C-1′), 129.7 (C-2′
and C-6′), 123.2 (C-3′ and C-5′), 147.8 (C-4′). MS (ESI) m/z: 290.11 [M]+•.
(E)-2-(1H-benzo[d]imidazol-2-yl)-3-(2-hydroxyphenyl)acrylonitrile (3d)
Anal. calc. for C16H11N3O: C, 73.55; H, 4.24; N, 16.08; found: C, 73.51; H, 4.21; N, 16.13.
1
FT-IR (KBr, cm-1): 3416, 3284, 3092, 3034, 2217, 1644, 1628, 1526. H NMR (400 MHz,
DMSO-d6, δ, ppm): 12.12 (s, 1H, -NH), 10.47 (s, 1H, -OH), 8.17 (s, 1H, =CH), 7.82 (d, 2H,

Page 7 of 30
New Journal of Chemistry
H-4 and H-7), 7.55-7.60 (m, 2H, H-5 and H-6), 6.72 (d, 1H, H-3′), 7.16 (dd, 1HD,OHI: -104.1′)0,3V9i6e/wC.98ArN6ticJl0e1O4n3l6inAe
(dd, 1H, H-5′), 7.72 (d, 1H, H-6′). 13C NMR (100 MHz, DMSO-d6, δ, ppm): 142.6 (C-2),
139.4 (C-3a and C-7a), 117.2 (C-4 and C-7), 126.4 (C-5 and C-6), 109.2 (C-1″), 154.5 (C-2″),
118.4 (C≡N), 116.2 (C-1′), 158.3 (C-2′), 117.6 (C-3′), 132.3 (C-4′), 121.2 (C-5′), 128.7 (C-6′).
MS (ESI) m/z: 261.13 [M]+•.
(E)-2-(1H-benzo[d]imidazol-2-yl)-3-(4-hydroxy-3-methoxyphenyl)acrylonitrile (3e)
Anal. calc. for C17H13N3O2: C, 70.09; H, 4.50; N, 14.42; found: C, 72.84; H, 4.20; N, 13.63.
1
FT-IR (KBr, cm-1): 3426, 3288, 3076, 3027, 2983, 2225, 1648, 1630, 1522. H NMR (400
MHz, DMSO-d6, δ, ppm): 12.19 (s, 1H, -NH), 10.71 (s, 1H, -OH), 8.15 (s, 1H, =CH), 7.95 (d,
2H, H-4 and H-7), 7.60-7.65 (m, 2H, H-5 and H-6), 7.22 (s, 1H, H-2′), 6.99 (d, 1H, H-5′),
13
7.34 (d, 1H, H-6′), 3.94 (s, 3H, -OCH3). C NMR (100 MHz, DMSO-d6, δ, ppm): 142.9 (C-
2), 139.8 (C-3a and C-7a), 115.6 (C-4 and C-7), 124.3 (C-5 and C-6), 107.8 (C-1″), 155.1 (C-
2″), 119.2 (C≡N), 129.4 (C-1′), 111.7 (C-2′), 149.6 (C-3′), 147.5 (C-4′), 117.3 (C-5′), 122.9
(C-6′), 56.8 (-OCH3). MS (ESI) m/z: 291.15 [M]+•.
(E)-2-(1H-benzo[d]imidazol-2-yl)-3-(3,4-dimethoxyphenyl)acrylonitrile (3f)
Anal. calc. for C18H15N3O2: C, 70.81; H, 4.95; N, 13.76; found: C, 73.47; H, 4.78; N, 13.04.
1
FT-IR (KBr, cm-1): 3442, 3086, 3038, 2978, 2219, 1643, 16028, 1542. H NMR (400 MHz,
DMSO-d6, δ, ppm): 12.09 (s, 1H, -NH), 8.21 (s, 1H, =CH), 7.89 (d, 2H, H-4 and H-7), 7.55-
7.60 (m, 2H, H-5 and H-6), 7.81 (s, 1H, H-2′), 6.94 (d, 1H, H-5′), 7.71 (d, 1H, H-6′), 3.89 (s,
13
6H, -OCH3). C NMR (100 MHz, DMSO-d6, δ, ppm): 144.3 (C-2), 140.1 (C-3a and C-7a),
117.4 (C-4 and C-7), 124.6 (C-5 and C-6), 106.8 (C-1″), 153.5 (C-2″), 119.9 (C≡N), 127.7
(C-1′), 115.5 (C-2′), 151.9 (C-3′), 149.8 (C-4′), 111.4 (C-5′), 121.8 (C-6′), 55.8 (2 × -OCH3).
MS (ESI) m/z: 305.17 [M]+•.
(E)-2-(1H-benzo[d]imidazol-2-yl)-3-(1H-indol-3-yl)acrylonitrile (3g)

New Journal of Chemistry
Page 8 of 30
View Article Online
Anal. calc. for C18H12N4: C, 76.04; H, 4.25; N, 19.71; found: C, 74.35; H, 4.54; N, 20.35. FT-
DOI: 10.1039/C8NJ01436A
1
IR (KBr, cm-1): 3477, 3452, 3075, 3029, 2220, 1656, 1627, 1549. H NMR (400 MHz,
DMSO-d6, δ, ppm): 12.22 (s, 1H, N1-H), 12.84 (s, 1H, N1′-H), 8.10 (s, 1H, =CH), 7.71 (d,
2H, H-4 and H-7), 7.41-7.59 (m, 2H, H-5 and H-6), 7.96 (s, 1H, H-2′), 7.82 (d, 1H, H-4′),
7.25-7.31 (m, 2H, H-5′ and H-6′), 7.05 (d, 1H, H-7′). 13C NMR (100 MHz, DMSO-d6, δ,
ppm): 143.3 (C-2), 137.3 (C-3a and C-7a), 115.2 (C-4 and C-7), 122.9 (C-5 and C-6), 112.5
(C-1″), 148.7 (C-2″), 118.2 (C≡N), 128.6 (C-2′), 110.3 (C-3′), 127.2 (C-3′a), 118.0 (C-4′),
119.8 (C-5′), 121.1 (C-6′), 109.3 (C-7′), 135.8 (C-7′a). MS (ESI) m/z: 284.14 [M]+•.
(E)-2-(1H-benzo[d]imidazol-2-yl)-3-(5-hydroxy-1H-indol-3-yl)acrylonitrile (3h)
Anal. calc. for C18H12N4O: C, 71.99; H, 4.03; N, 18.66; found: C, 69.43; H, 4.51; N, 19.54.
1
FT-IR (KBr, cm-1): 3488, 3465, 3315, 3082, 3065, 2212, 1645, 1624, 1520. H NMR (400
MHz, DMSO-d6, δ, ppm): 12.27 (s, 1H, N1-H), 12.69 (s, 1H, N1′-H), 10.19 (s, 1H, -OH),
7.99 (s, 1H, =CH), 7.69 (d, 2H, H-4 and H-7), 7.42-7.49 (m, 2H, H-5 and H-6), 7.89 (s, 1H,
H-2′), 6.87 (s, 1H, H-4′), 6.58 (d, 1H, H-6′), 6.97 (d, 1H, H-7′). 13C NMR (100 MHz, DMSO-
d6, δ, ppm): 141.9 (C-2), 137.9 (C-3a and C-7a), 116.2 (C-4 and C-7), 124.2 (C-5 and C-6),
113.7 (C-1″), 154.5 (C-2″), 118.5 (C≡N), 129.6 (C-2′), 111.6 (C-3′), 127.7 (C-3′a), 103.6 (C-
4′), 152.4 (C-5′), 112.7 (C-6′), 112.1 (C-7′), 130.7 (C-7′a). MS (ESI) m/z: 300.15 [M+]+•.
(E)-2-(1H-benzo[d]imidazol-2-yl)-3-(5-methyl-1H-indol-3-yl)acrylonitrile (3i)
Anal. calc. for C19H14N4: C, 76.49; H, 4.73; N, 18.78; found: C, 78.74; H, 4.55; N, 17.67. FT-
IR (KBr, cm-1): 3456, 3418, 3071, 3027, 2975, 2219, 1655, 1639, 1543. 1H NMR (400 MHz,
DMSO-d6, δ, ppm): 12.32 (s, 1H, N1-H), 12.74 (s, 1H, N1′-H), 8.04 (s, 1H, =CH), 7.78 (d,
2H, H-4 and H-7), 7.52-7.60 (m, 2H, H-5 and H-6), 7.91 (s, 1H, H-2′), 7.39 (s, 1H, H-4′), 7.13
(d, 1H, H-6′), 7.01 (d, 1H, H-7′), 2.35 (s, 3H, -CH3). 13C NMR (100 MHz, DMSO-d6, δ,
ppm): 142.9 (C-2), 137.6 (C-3a and C-7a), 116.3 (C-4 and C-7), 123.3 (C-5 and C-6), 112.5
(C-1″), 150.7 (C-2″), 118.2 (C≡N), 128.5 (C-2′), 110.3 (C-3′), 126.0 (C-3′a), 121.6 (C-4′),

Page 9 of 30
New Journal of Chemistry
View Article Online
130.4 (C-5′), 120.8 (C-6′), 108.9 (C-7′), 134.8 (C-7′a), 24.9 (-CH3). MS (ESI) DmOI/:z1:0.1209398/C.18N6J01436A
[M]+•.
(E)-2-(1H-benzo[d]imidazol-2-yl)-3-(4-oxo-4H-chromen-3-yl)acrylonitrile (3j)
Anal. calc. for C19H11N3O2: C, 72.84; H, 3.54; N, 13.41; found: C, 70.47; H, 3.89; N, 14.36.
1
FT-IR (KBr, cm-1): 3456, 3089, 3028, 2223, 1673, 1655, 1595, 1526. H NMR (400 MHz,
DMSO-d6, δ, ppm): 12.16 (s, 1H, NH), 7.83 (s, 1H, =CH), 7.93 (d, 2H, H-4 and H-7), 7.53-
7.59 (m, 2H, H-5 and H-6), 7.26 (s, 1H, H-2′), 8.05 (d, 1H, H-5′), 7.39 (dd, 2H, H-6′ and H-
7′), 7.60 (d, 1H, H-8′). 13C NMR (100 MHz, DMSO-d6, δ, ppm): 144.4 (C-2), 137.7 (C-3a and
C-7a), 114.9 (C-4 and C-7), 122.6 (C-5) 123.7 (C-6), 113.3 (C-1″), 145.0 (C-2″), 119.6
(C≡N), 149.3 (C-2′), 121.1 (C-3′), 191.8 (C-4′), 128.2 (C-4′a), 129.5 (C-5′), 127.6 (C-6′),
135.8 (C-7′), 117.0 (C-8′), 154.8 (C-8′a). MS (ESI) m/z: 313.17 [M]+•.
(E)-2-(1H-benzo[d]imidazol-2-yl)-3-(6-methyl-4-oxo-4H-chromen-3-yl) acrylonitrile (3k)
Anal. calc. for C20H13N3O2: C, 73.38; H, 4.00; N, 12.84; found: C, 75.14; H, 3.78; N, 12.33.
1
FT-IR (KBr, cm-1): 3445, 3088, 3029, 2986, 2218, 1672, 1642, 1590, 1518. H NMR (400
MHz, DMSO-d6, δ, ppm): 12.09 (s, 1H, NH), 8.05 (s, 1H, =CH), 7.78 (d, 2H, H-4 and H-7),
7.60-7.67 (m, 2H, H-5 and H-6), 7.38 (s, 1H, H-2′), 7.85 (s, 1H, H-5′), 7.54 (d, 2H, H-7′ and
H-8′), 2.41 (s, 3H, -CH3). 13C NMR (100 MHz, DMSO-d6, δ, ppm): 143.4 (C-2), 138.5 (C-3a
and C-7a), 116.6 (C-4 and C-7), 124.9 (C-5 and C-6), 110.8 (C-1″), 145.1 (C-2″), 119.4
(C≡N), 149.8 (C-2′), 121.2 (C-3′), 191.5 (C-4′), 127.5 (C-4′a), 124.9 (C-5′), 135.1 (C-6′),
141.7 (C-7′), 131.1 (C-8′), 156.2 (C-8′a), 24.3 (-CH3). MS (ESI) m/z: 327.15 [M]+•.
(E)-2-(1H-benzo[d]imidazol-2-yl)-3-(6-fluoro-4-oxo-4H-chromen-3-yl)acrylonitrile (3l)
Anal. calc. for C19H10FN3O2: C, 68.88; H, 3.04; N, 12.68; found: C, 70.74; H, 2.98; N, 12.18.
1
FT-IR (KBr, cm-1): 3478, 3084, 3022, 2216, 1674, 1654, 1596, 1516. H NMR (400 MHz,
DMSO-d6, δ, ppm): 12.02 (s, 1H, NH), 8.14 (s, 1H, =CH), 7.89 (d, 2H, H-4 and H-7), 7.58-
7.65 (m, 2H, H-5 and H-6), 7.46 (s, 1H, H-2′), 7.81 (s, 1H, H-5′), 7.35 (d, 1H, H-7′), 7.18 (d,

New Journal of Chemistry
Page 10 of 30
1H, H-8′). 13C NMR (100 MHz, DMSO-d6, δ, ppm): 142.3 (C-2), 139.4 (C-3a and C-7a),
View Article Online
DOI: 10.1039/C8NJ01436A
116.0 (C-4 and C-7), 125.4 (C-5 and C-6), 111.9 (C-1″), 147.2 (C-2″), 118.9 (C≡N), 150.8
(C-2′), 120.6 (C-3′), 190.8 (C-4′), 128.8 (C-4′a), 109.7 (C-5′), 160.4 (C-6′), 123.7 (C-7′),
122.3 (C-8′), 153.0 (C-8′a). MS (ESI) m/z: 331.12 [M]+•.
3.
Results and discussion
3.1. Characterization of the catalyst
The SBPTS catalyst was synthesized as outlined in the Scheme 1, and characterized by
different spectroscopic and microscopic techniques including FT-IR, XRD, SEM-EDX and
TEM analysis. The FT-IR spectrum of the catalyst is depicted in Fig. 1 and was recorded
using the KBr disk technique. The FT-IR spectrum displays a stretching band of SiO-H at
3426 cm-1 while the stretching band of BO-H appears at 3221 cm-1. The peaks at 3046 and
2926 cm-1 is attributed to the stretching vibration of C-H of phenyl-ring and methyl group,
respectively. The bending vibration of C=C bond of phenyl-ring was observed at 1403 cm-1.
The peak at 2260 cm-1 was assigned to the B-OH combination and the peak at 1164 cm-1 was
attributed to the bending vibration of B-OH.59 The Si-O-Si symmetric and asymmetric
stretching vibration band were appeared at 1096 and 813 cm-1, respectively. The peaks at 926
and 641 cm-1 for the stretching and bending vibration of the borosiloxane linkage (Si-O-B),
respectively, and the peak at 569 and 1637 cm-1 are related to the formation of B-O-B and B-
O bands, respectively.57 The symmetric and asymmetric modes of O=S=O11 lies at 1020-1090
and 1120-1210 cm-1 and shows overlap with the Si-O-Si and B-OH bands. As evident from
FT-IR spectrum, both B-O and B-O-B bonds are present in SBPTS catalyst, thus proposed the
complex nature for boron atoms exists in this catalyst57 (Fig. 2).
Formation of the catalytic system (SBPTS) was further established by powder XRD
analysis recorded at the 2θ = 20-80o range (Fig. 3). The XRD of the catalyst showed

Page 11 of 30
New Journal of Chemistry
characteristic broad peak of silica in the range of 2θ = 20o-25o displaying amorphous nature of
View Article Online
DOI: 10.1039/C8NJ01436A
silica with two significant peak at 23.8o and 27.5o revealing the presence of Si-O and B-O
bonds in the crystalline structure of the SBPTS, respectively.57
Scheme 1 Pathway for the synthesis of SBPTS catalyst.
Fig. 1 FT-IR spectrum of the catalyst SBPTS

New Journal of Chemistry
Page 12 of 30
View Article Online
DOI: 10.1039/C8NJ01436A
Fig. 2 The proposed structure for the SBPTS catalyst.
400
300
200
100
20
30
40
50
60
70
80
2 (degree)
Fig. 3 Powder XRD pattern of the SBPTS catalyst

Page 13 of 30
New Journal of Chemistry
View Article Online
For the study of surface morphology of the catalyst, SEM and TEM microDgOraI: p10h.10o39f/Cth8NeJ01436A
catalyst were employed. The SEM micrograph (Fig. 4) showed the successful adsorption of
H3BO3-PTSC molecules on the surface of silica gel and were of uneven size and shape, and
well dispersed. The TEM micrograph (Fig. 5a) of the catalytic system further displayed
uniform distribution of agglomerated H3BO3-PTSC molecules as black dots on the surface of
silica, approving the formation of the expected catalytic system. The TEM analysis showed
the size of the molecules in the range of 2.5-5.0 nm. The histogram of the particle size
distributions (Fig. 5b) of the SBPTS catalyst further confirmed the size of the particle. The
histogram was proposed according to the results obtained from the TEM image. The EDX
analysis (ESI†, Fig S2) of the catalyst showed the presence of Si, B, C, S and O elements,
thus, suggesting the formation of the SBPTS catalytic system.
The thermal stability of the catalyst was assessed by TGA/DTA analysis (Fig. 6). The
o
TGA analysis revealed that the catalyst showed thermal stability up to 253 C. However, the
first weight loss at ~95 oC was attributed to loss of physically adsorbed water molecules in the
silica gel framework. The TGA was further supported by DTA analysis. The DTA curve
o
displayed two prominent endothermic peak at 104 and 242 C. The first peak is attributed to
the endothermic reaction which help in the removal of water molecules, while the second
peak may be due to the loss of SO2 group.53 Thus, the thermal study ensure that the SBPTS is
suitable for the use as catalyst in organic transformations.

New Journal of Chemistry
Page 14 of 30
View Article Online
DOI: 10.1039/C8NJ01436A
Fig. 4 SEM micrograph of the SBPTS catalyst
(a)
(b)
Fig. 5 (a) TEM image of the SBPTS catalyst; (b) Histogram representing the size distribution
of the SBPTS catalyst.

Page 15 of 30
New Journal of Chemistry
View Article Online
DOI: 10.1039/C8NJ01436A
Fig. 6 TGA/DTA curve of the SBPTS catalyst
3.2. Optimization of reaction condition
In the present study, a library of benzimidazole-acrylonitrile derivatives, 3(a-l) have been
synthesized via microwave assisted knoevenagel condensation reaction involving
benzimidazole-2-acetonitrile, 1 and different aromatic aldehydes, 2(a-l) in presence of SBPTS
catalyst (Scheme 2).
Scheme 2 Synthetic route for the synthesis of benzimidazole-acrylonitrile derivatives 3(a-l)

New Journal of Chemistry
Page 16 of 30
View Article Online
For our initial investigation, the reaction of benzimidazole-2-acetonitrile (1, 2mmol and
DOI: 10.1039/C8NJ01436A
p-(N,N-dimethylamino)benzaldehyde, (2a, 2mmol) was chosen as a model reaction to
optimize the reaction conditions for the present protocol including amount of catalyst,
reaction temperature, solvent effect and investigating efficiency of different catalyst to
establish the best possible reaction conditions for the synthesis of benzimidazole acrylonitrile
derivatives. The reaction was first carried out in ethanol in the absence and presence of
several catalyst at 70 oC. The reaction did not proceed even after prolonged reaction time (24
h) and no desired product was formed in the absence of catalyst (Table 1, entry 1), thus
signifying the need of catalyst. Thus, we focused on the search for a suitable heterogeneous
catalyst, such as SiO2-Cl, SiO2/HClO4, SiO2/NH4OAc, SiO2/NaHSO4, SiO2/H3BO3 and
o
SBPTS that can catalyse this reaction in ethanol at 70 C with better efficiency. Our analysis
revealed that, amongst all the screened catalyst, the catalytic activity was found in the order of
SBPTS > SiO2/H3BO3 > SiO2-Cl > SiO2/HClO4 > SiO2/NaHSO4 > SiO2/NH4OAc (Table1,
entries 2-6) in terms of product yield and reaction time. In order to establish the superiority of
our catalyst, we have compared this with three other catalyst previously reported for synthesis
of acrylonitrile derivatives viz. SiO2-Cl,14 SiO2/piperidine60 and Silica Bonded N-
(Propylcarbamoyl) sulfamic acid (SBPCSA),56 and we found the catalytic activity in the order
of SBPTS > SBPCSA > SiO2-Cl > SiO2/piperidine (Table1, entries 6-9). Thus, SBPTS is the
catalyst of choice for the present protocol. In addition, we examined the influence of different
organic solvents such as MeOH, CH2Cl2, CH3COOH, DMF and THF on the model reaction in
presence of SBPTS catalyst (Table 1, entry 8-12). When the reaction was carried out in
CH2Cl2, DMF and THF, moderate yield of the product (55-64%) was obtained after extended
reaction time. However, in presence of MeOH and CH3COOH, the yield of the reaction is
quite improved (73-78%), with dip in reaction time. However, with respect to the solvent
system, the best results were achieved with ethanol (Table 1, entry 7). In order to make the

Page 17 of 30
New Journal of Chemistry
View Article Online
protocol more efficient, we introduced the microwave irradiation, which enhanced the
DOI: 10.1039/C8NJ01436A
reaction yield (98%) within short reaction time (10 min) in presence of SBPTS catalyst and
ethanol at 70 oC (Table 1, entry 13).
Table 1. Effect of different reaction media on the model reactiona
Entry
Solvent
Condition
Time (h)b
Yield (%)c
1
2
EtOH
EtOH
70 oC, No catalyst
70 oC, SiO2/NH4OAc
70 oC, SiO2/HClO4
70 oC, SiO2/NaHSO4
70 oC, SiO2/H3BO3
70 oC, SBPTS
24
--
5.5
59
67
62
75
90
80
85
78
78
64
73
59
55
98
3
EtOH
4
4
EtOH
5
5
EtOH
3
6
EtOH
45 min
7
EtOH
70 oC, SiO2-Cl
1.5
8
EtOH
70 oC, SBPCSA
70 oC, SiO2/piperidine
70 oC, SBPTS
70 min
9
EtOH
2
10
11
12
13
14
15
MeOH
CH2Cl2
CH3COOH
DMF
2
70 oC, SBPTS
70 oC, SBPTS
70 oC, SBPTS
70 oC, SBPTS
5
4
8
THF
10
EtOH
70 oC, SBPTS, MW
10 min
a
Reaction conditions: Benzimidazole-2-acetonitrile (1, 2 mmol) and p-(N,N-dimethylamino)
benzaldehyde (2a, 2 mmol), different solvent (10 mL), different catalyst (10 mol%), 70 oC.
b Reaction progress monitored by TLC. c Isolated yield of products.
In order to achieve the optimum concentration of the catalyst, the model reaction was
o
examined at different concentration (2-12 mol%) of the SBPTS catalyst at 70 C in ethanol
under MW irradiation. When we carried out the reaction with 2-8 mol% of catalyst, the
reaction took prolonged time with only 33-87% yield. On the other hand, when we used 10

New Journal of Chemistry
Page 18 of 30
View Article Online
mol% of the catalyst the reaction proceeded very effectively, with excellent yields (98%)
DOI: 10.1039/C8NJ01436A
within 10 min. Further increase of the catalyst amount does not affect the yield of the product.
Thus, the above results signifies that 10 mol% of SBPTS catalyst is optimum dose for the
present protocol in terms of efficient yield and reaction time.
Table 2 Effect of catalyst loading on the model reactiona
Entry
Catalyst (mol%)
Time (min)b
Yield (%)c
1
2
3
4
5
6
2
4
50
35
28
22
10
10
33
52
74
87
98
98
6
8
10
12
a
Reaction conditions: Benzimidazole-2-acetonitrile (1, 2 mmol) and p-(N,N-dimethylamino)
benzaldehyde (2a, 2 mmol), EtOH (10 mL), SBPTS catalyst (2-12 mol%), Temp. (70 oC), MW.
b Reaction progress monitored by TLC. c Isolated yield of products.
The reaction was further studied at different temperatures in order to find out the
optimum reaction temperature for the synthesis of 3a in ethanol with SBPTS catalyst under
microwave irradiation (Table 3). It was observed that increase in temperature from 25 to 70
oC, has a prominent effect on the model reaction in terms of yield and reaction time (Table 3,
entry 2-5). However, no further enhancement in the yield was noticed when the reaction
o
temperature was raised from 70 to 80 C (Table 3, entry 6). Thus, it was concluded that the
best reaction condition for the synthesis of 3a is to carried out the reaction in ethanol at 70 oC
coupled with 10 mol% of the SBPTS catalyst under microwave irradiation.

Page 19 of 30
New Journal of Chemistry
Table 3. Effect of temperature on the model reactiona
View Article Online
DOI: 10.1039/C8NJ01436A
Entry
Temperature (oC)
Time (min)b
Yield (%)c
1
2
3
4
5
6
25
40
50
60
70
80
90
40
25
20
10
10
65
72
78
87
98
98
a
Reaction conditions: Benzimidazole-2-acetonitrile (1, 2 mmol) and p-(N,N-dimethylamino)
benzaldehyde (2a, 2 mmol), EtOH (10 mL), SBPTS catalyst (10 mol%), Temp. (25-80 oC), MW.
b Reaction progress monitored by TLC. c Isolated yield of products.
A variety of substrates were submitted to the optimized reaction condition in order to
investigate the substrate scope of SBPTS catalysed system. As presented in Table 4, variety of
functional groups substituted at the aromatic ring of the aldehyde substrate, including electron
withdrawing and electron donating groups reacted with benzimidazole-2-acetonitrile to afford
the corresponding benzimidazole-acrylonitrile derivatives 3(a-l) in excellent yields. In the
present study, a comparative study has also been carried out between the conventional thermal
heating and microwave heating. It is evident that the microwave-assisted synthesis was more
efficient in terms of product yield and reaction time (Table 4). In general, all the reaction
proceeded efficiently with microwave-assisted synthesis at 70 oC with 10 mol% of the SBPTS
catalyst in the presence of ethanol. The reactions are clean and no side products were detected.
Therefore, we can say that the present protocol has general applicability and accommodates a
variety of substitution patterns.

New Journal of Chemistry
Page 20 of 30
View Article Online
DOI: 10.1039/C8NJ01436A
Table 4 Synthesis of benzimidazole acrylonitrile derivatives 3(a-l)
Conventional
methoda
Microwave
irradiationb
S.No.
3a
Product
Time
(min)
Yield
(%)
Time
(min)
Yield
(%)
45
90
10
98
50
45
50
88
89
86
10
10
12
97
98
96
3b
3c
3d
50
45
45
85
90
88
12
10
10
94
98
97
3e
3f
3g

Page 21 of 30
New Journal of Chemistry
View Article Online
DOI: 10.1039/C8NJ01436A
55
85
87
89
12
12
10
96
94
97
3h
3i
55
50
3j
50
45
86
90
12
10
95
98
3k
3l
a
Reaction conditions: Benzimidazole-2-acetonitrile (1, 2 mmol) and differently substituted aldehydes
(2a-l) (2 mmol), EtOH (10 mL), SBPTS catalyst (10 mol%), Temp. (70 oC).
b
Reaction conditions: Benzimidazole-2-acetonitrile (1, 2 mmol) and differently substituted aldehydes
(2a-l) (2 mmol), EtOH (10 mL), SBPTS catalyst (10 mol%), Temp. (70 oC), MW.
3.3. Recyclability of the catalyst
The recyclability is a significant property of catalyst, so as to satisfy the green chemistry
principles and to manage the process cost. In order to explore the extent of recyclability of our
catalyst system, the model reaction has been conducted under optimized condition for six

New Journal of Chemistry
Page 22 of 30
View Article Online
consecutive times. After the completion of first fresh runs, the catalyst was removed by
DOI: 10.1039/C8NJ01436A
o
simple filtration, washed thoroughly with ethanol and dried in vacuum oven for 2h at 100 C.
The recovered catalyst was then reused for five more subsequent cycles under the same
optimized condition and found to retain its catalytic activity and showed minimal decrease in
the yield (Fig. 7), thus, proving the catalyst's reusability with high catalytic performances. To
ascertain the variation in morphological features of the recovered catalyst, SEM-EDX
analysis was performed. It was found that there was no significant changes noticed in the
composition and morphology of the recovered catalyst (ESI†, Fig S3-S5). These results
demonstrate that our catalytic system is stable and could be recycled without a significant loss
in yield.
3.4. Reaction Mechanism
The probable mechanistic pathway for the SPBTS catalysed synthesis of benzimidazole-
acrylonitrile derivatives has been presented in Scheme 3. The reaction is initiated with the
protonation of carbonyl group by SBPTS catalyst, which generates the active electrophilic site
in intermediate (I). Further, the conjugate base of the catalyst generates the nucleophilic site
(II) by removing the proton from the active methylene carbon of benzimidazole-2-acetonirile,
which facilitates the formation of C-C bond to yield intermediate (III). The subsequent
elimination of water molecule from intermediate (III) promoted by the SBPTS catalyst
eventually leads to the formation of target benzimidazole acrylonitrile derivative with the
regeneration of the catalyst SBPTS.
3.5. Chemistry
The structural elucidation of all the synthesized compounds 3(a-l) has been established on the
basis of FT-IR, 1H NMR, 13C NMR and mass spectral studies and found to be in good support
with the expected structure. The FT-IR spectrum of all the synthesized compounds shows

Page 23 of 30
New Journal of Chemistry
View Article Online
absence of aldehydic carbonyl group, which confirmed the reaction at the target carbonyl
DOI: 10.1039/C8NJ01436A
moiety of the substrates. Moreover, all the compounds displayed a characteristic peak for
C≡N, =C-H and C=C groups, resonating at around 2216-2225 cm-1, 3076-3092 cm-1 and
1642-1656 cm-1, respectively, which signifies the formation of a acrylonitrile derivatives. In
1H NMR spectral analysis, each synthesized compound displayed a sharp singlet resonating at
around δ 7.83-8.27, attributed to the olefinic proton, this prominent downfield shift displayed
by the olefinic proton of acrylonitrile is probably due to its acidic nature imposed by adjacent
cyano group (ESI†). In the 13C NMR spectral study, the absorption band resonating at around
δ 118.2-120.7 has been assigned to the -C≡N group of acrylonitrile derivatives. Furthermore,
the peaks appeared at δ 106.8-113.3 and 145.1-155.8 corresponded to C-1″ and C-2″ of
olefinic carbons (ESI†).
RECYCLABILITY
Time (min)
Yield (%)
98
97
95
92
90
88
100
80
60
40
20
0
14
12
12
5
10
10
10
1
2
3
4
6
NO. OF CYCLES
Fig. 7 Recyclability of the catalyst

New Journal of Chemistry
Page 24 of 30
View Article Online
DOI: 10.1039/C8NJ01436A
Scheme 3 Plausible mechanistic catalytic cycle for the synthesis of target benzimidazole-
acrylonitrile derivatives 3(a-l)
4.
Conclusion
In conclusion, we have established a facile and environmentally benign method for the
synthesis of a series of highly functionalized benzimidazole-acrylonitrile derivatives 3 (a-l) in
excellent yields (94-98%) by employing novel recyclable SBPTS catalyst in ethanol under
microwave irradiation. The noteworthy features of this protocol are mild reaction conditions,
shorter reaction time, operational simplicity, cleaner reaction profile, high purity, enhanced
reaction rates and easy workup procedure. We believe that this synthetic approach provides a

Page 25 of 30
New Journal of Chemistry
View Article Online
better scope for the synthesis of acrylonitrile analogues and will be more practical alternative
DOI: 10.1039/C8NJ01436A
to the other existing methods.
Conflict of Interest
The authors declare no competing financial interest.
Acknowledgement
F. Ahmad thanks the Chairman, Department of Chemistry, AMU, Aligarh, for providing the
necessary research facilities. USIF, AMU, Aligarh and SAIF, Panjab University, Chandigarh,
are acknowledged for characterization.

New Journal of Chemistry
Page 26 of 30
View Article Online
DOI: 10.1039/C8NJ01436A
Reference
[1] R. Ballini, Eco-Friendly Synthesis of Fine Chemicals, Royal Society of Chemistry,
2009.
[2] M. Parveen, F. Ahmad, A. M. Malla, S. Azaz, M. R. Silva and P. S. P. Silva, RSC Adv.,
2015, 5, 52330-52346.
[3] F. Sabate, J. Navas, M. J. Sabater and A. Corma, C. R. Chim., 2018, 21, 164-173
[4] M. Parveen, S. Azaz, A. M. Malla, F. Ahmad, M. Ahmad and M. Gupta, RSC Adv.,
2016, 6, 148-162.
[5] G. Villaverde, A. Corma, M. Iglesias and F. Sanchez, ACS Catal., 2012, 2, 399-406.
[6] A. M. Malla, M. Parveen, F. Ahmad, S. Azaz and M. Alam, RSC Adv., 2015, 5, 19552-
19569.
[7] R. A. Sheldon, Green Chem., 2005, 7, 267-278.
[8] M. Parveen, S. Azaz, A. M. Malla, F. Ahmad, P. S. P. Silva and M. R. Silva, New J.
Chem., 2015, 39, 469-481.
[9] J. D. Vidal, M. J. Climent, A. Corma, D. P. Concepcion and S. Iborra, Chem. Sus.
Chem., 2017, 10, 119-128.
[10] S. Moradi, M. A. Zolfigol, M. Zarei, D. A. Alonso, A. Khoshnood and A. Tajally, Appl.
Organometal. Chem., 2018, 32, 4043.
[11] M. Parveen, F. Ahmad, A. M. Malla, M. Alam and D. U. Lee, Catal. Lett., 2014, 144,
2091-2106.
[12] M. Kour, M. Bhardwaj, H. Sharma, S. Paul and J. H. Clark, New J. Chem., 2017, 41,
5521-5532.
[13] L. Wang, W. Zhao and W. Tan, Nano Res., 2008, 1, 99-115.
[14] M. Parveen, A. M. Malla, M. Alam, M. Ahmad and S. Rafiq, New J. Chem., 2014, 38,
1655-1667.
[15] M. Parveen, F. Ahmad, A. M. Malla and S. Azaz, New J. Chem., 2015, 39, 2028-2041.
[16] M. A. Zolfigol, M. Kiafar, M. Yarie, A. Taherpour and M. S. Rad, RSC Adv., 2016, 6,
50100-50111.

Page 27 of 30
New Journal of Chemistry
[17] A. R. M. Zarea, M. A. Zolfigol, E. Noroozizadeh, R. S. Moratab and M. Zarei, J. VMiewoAlr.ticle Online
DOI: 10.1039/C8NJ01436A
Catal. A: Chem., 2016, 420, 246-253.
[18 ] M. Kaur, S. Sharma and P. M. S. Bedi, Chin. J. Catal., 2015, 36, 520-549.
[19] M. A. Zolfigol, R. A. Nasrabadi and S. Baghery, Appl. Organomet. Chem., 2016, 30,
273-281.
[20] (a) F. Ahmad, M. J. Alam, M. Alam, S. Azaz, M. Parveen, S. Park and S. Ahmad, J.
Mol. Struc., 2018, 1151, 327-342; (b) M. Parveen, A. M. Malla, M. Alam, F. Ahmad, P.
S. P. Silva and M. R. Silva, Nat. Prod. Res., 2014, 28, 646-652; (c) S. Kumar, M.
Ceruso, T. Tuccinardi, C. T. Supuran and P. K. Sharma, Bioorg. Med. Chem., 2016, 24,
2907-2913.
[21] P. Jeyakkumar, L. Zhang, S. R. Avula and C. H. Zhou, Eur. J. Med. Chem., 2016, 122,
205-215.
[22] M. Özil, C. Parlak and N. Baltas, Bioorg. Chem., 2018, 76, 468-477.
[23] N.S. El-Gohary, M. I. Shaaban, Eur. J. Med. Chem., 2017, 137, 439-449.
[24] M. Azam, A. A. Khan, S. I. Al-Resayes, M. S. Islam, A. K. Saxena, S. Dwivedi, J.
Musarrat, A. T. Kruszynska and R. Kruszynski, Spectrochim. Acta A Mol. Biomol.
Spectrosc., 2015, 142, 286-291.
[25] E. Mentes, F. Yılmaz, M. Emirik, S. Ülker and B. Kahveci, Bioorg. Chem., 2018, 76,
478-486.
[26] A. Jain, R. Sharma and S. C. Chaturvedi, Med. Chem. Res., 2013, 22, 4622-4632.
[27] S. Lingala, R. Nerella and K. R. S. S. Rao, Int. J. Pharm. Sci. Rev. Res., 2011, 10, 100-
105.
[28] C. K. Achar, K. M. Hosamani and H. R. Seetharamareddy, Eur. J. Med. Chem., 2010,
45, 2048-2054.
[29] Y. Bansal and O. Silakari, Bioorg. Med. Chem., 2012, 20, 6208-6236.
[30] T. Pan, X. He, B. Chen, H. Chen, G. Geng, H. Luo, H. Zhang and C. Bai, Eur. J. Med.
Chem., 2015, 95, 500-513.
[31] Y. T. Wang, L. R Lü and G. M. Tang, J. Mol. Struc., 2018, 1156, 156-163.

New Journal of Chemistry
Page 28 of 30
View Article Online
[32] J. Wang, J. Liao, L. Yang, S. Zhang, X. Huang and J. Ji, J. Membr. Sci., 2012, 415-416,
DOI: 10.1039/C8NJ01436A
644-653.
[33] A. Singh and H. Chopra, Tetrahedron: Asymmetry, 2016, 27, 448-453.
[34] K. M. Borys, M. D. Korzynski and Z. Ochal, Beilstein J. Org. Chem., 2012, 8, 259-265.
[35] S. Pal, W. S. Hwang, I. J. Lin, C. S. Lee, J. Mol. Catal. A Chem., 2007, 269, 197-203.
[36] N. Singh and D. O. Jang, Org. Lett., 2007, 9, 1991-1994.
[37] Y. Ooyama and K. Yoshida, New J. Chem., 2005, 29, 1204-1212.
[38] S. Song, J. Kim, J. Shim, J. Kim, B. H. Lee, Y. Jin, I. Kim, K. Lee and H. Suh, Sol.
Energy Mater. Sol. Cells, 2012, 98, 323-330.
[39] A. Carta, M. Palomba, G. Boatto, B. Busonera, M. Murreddu and R. Loddo, II
Farmaco, 2004, 59, 637-644.
[40] M. Hranjec, G. Pavlovic, M. Marjanovic, M. Kralj and G. K. Zamola, Eur. J. Med.
Chem., 2010, 45, 2405-2417.
[41] F. Saczewski, A. Stencel, A. M. Bienczak, K. A. Langowska, M. Michaelis, W. Werel,
R. Halasa, P. Reszka and P. Bednarski, Eur. J. Med. Chem., 2008, 43, 1847-1857.
[42] P. Sanna, A. Carta and M. E. R. Nikookar, Eur. J. Med. Chem., 2000, 35, 535-543.
[43] V. S. Parmar, A. Kumar, A. K. Prasad, S. K. Singh, N. Kumar, S. Mukherjee, H. G. Raj,
S. Goel, W. Errington and M. S. Puard, Bioorg. Med. Chem., 1999, 7, 1425-1436.
[44] S. Naruto, H. Mizuta, T. Yoshida, H. Uno, K. Kawashima, T. Kadokawa and H.
Nishimura, Chem. Pharm. Bull., 1983, 31, 3022-3032.
[45] J. Grundy, Chem. Rev., 1957, 57, 281-415.
[46] P. Sanna, A. Carta, L. Gherardini and M. E. R. Nikookar, II Farmaco, 2002, 57, 79-87.
[47] E. A. Glazer and L. R. Chappel, J. Med. Chem., 1982, 25, 766-769.
[48] G. Thirupathi, M. Venkatanarayana, P. K. Dubey and Y. B. Kumari, Der Pharma
Chem., 2012, 4, 1897-1901; M. Tarleton, J. Gilbert, J. A. Sakoff and A. McCluskey,
Eur. J. Med. Chem., 2012, 57, 65-73.
[49] B. Karmakar, A. Nayak and J. Banerji, Tetrahedron Lett., 2012, 53, 5004-5007.
[50] F. T. Boullet and A. Foucaud, Tetrahedron Lett., 1982, 23, 4927-4928.

Page 29 of 30
New Journal of Chemistry
View Article Online
[51] J. S. Yadav, P. P. Rao, D. Sreenu, R. S. Rao, V. N. Kumar, K. Nagaiah and A. R.
DOI: 10.1039/C8NJ01436A
Prasad, Tetrahedron Lett., 2005, 46, 7249-7253.
[52] D. W. Morrison, D. C. Forbesa and J. H. Davis, Tetrahedron Lett., 2001, 42, 6053-6055.
[53] J. R. Harjani, S. J. Nara and M. M. Salunkhe, Tetrahedron Lett., 2002, 43, 1127-1130.
[54] D. Tahmassebi, L. J. A. Wilson and J. M. Kieser, Synth. Commun., 2009, 39, 2605-
2613.
[55] S.A.R. Mulla, A. Sudalai, M.Y. Pathan, S.A. Siddique, S.M. Inamdar, S.S. Chavan, R.S.
Reddy, RSC Adv., 2012, 2, 3525-3529.
[56] M. Parveen, S. Azaz, F. Ahmad, A. M. Malla and M. Alam, Catal. Lett., 2016, 146,
1687-1705.
[57] A. K. Nezhad, H. Foroughi, M. M. Doroodmand and F. Panahi, J. Mater. Chem., 2011,
21, 12842-12851.
[58] E. Horak, R. Vianello, M. Hranjec, S. Krištafor, G. K. Zamola and I. M. Steinberg,
Spectrochim. Acta A Mol. Biomol. Spectrosc., 2017, 178, 225-233.
[59] V. Kumar, U. Sharma, P. K. Verma, N. Kumar and B. Singh, Chem. Pharm. Bull., 2011,
59, 639-645.
[60] C. Mukhopadhyay and S. Ray, Catal. Commun., 2011, 12, 1496-1502.