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Concentrated solar radiation promoted unconventional greener approach:solvent-free benign synthesis of functionalized benzimidazoles
Simran Harsh,a Mohamad Yusuf,b Rohit Sharma,c Yogesh Kumar,a,d and Rupesh Kumar*a
Department of Chemical Sciences, I. K. G. Punjab Technical University, Kapurthala, Punjab, India-144603
b.
Department of Chemistry, Punjabi University, Patiala, Punjab, Indiac.
Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research, Mohali,
Punjab, Indiad.
UNAM-National Nanotechnology Research Center, Institute of Materials Science and Nanotechnology,
Department of Chemistry, Bilkent University, 06800 Ankara, Turkey
E-mail: rupesh.manak@gmail.com
a.

Received 07-10-2018

Accepted 08-27-2018

Published on line 09-12-2018

Abstract
Renewable concentrated solar-radiation (CSR) offered a promising en route for the development of practical,
highly efficient, scalable, catalyst free and solvent-free clean process leading to the synthesis of functionalized
benzimidazoles. Developed protocol has a very good substrate scope, involves mild reaction conditions andproducts obtained in good to excellent yields. Method presented the observations in which light alone could
affect the remarkable changes with more than 85% energy saving and 75% less reaction time in listed organic
transformations.

Keywords: Concentrated solar radiation, photocatalysis, solar synthesis, C-N bond formation, benzimidazoles
DOI: https://doi.org/10.24820/ark.5550190.p010.687

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Introduction
Solar light offers an inimitable, inexpensive, non-polluting, plentiful and renewable natural energy.
Development of methods for efficient use of solar radiation has emerged as one of the most recent
challenge.1-5 Almost every class of chemists is trying hard to realize various organic transformations exploiting
natural solar light6-10 but unfortunately, despite of significant efforts, photochemical synthesis still rests in its
early stage and lying far away from its effectual development. Photochemical approach for the synthesis ofheterocycles has been taken up excitedly in the modern-day synthetic organic chemistry.11-15 Synthetic visible
light photochemical methods6-10 are often sustainable and green as these methods represent its superiority in
two ways. First; it replaces highly toxic and expensive metal catalysts and works through the conversion ofreactants into its higher energy states. In this excited state, it can subsequently undergo multiple physical andchemical pathways to furnish target products and offers inherently safer chemistry. Secondly, 16-18 it does notproduce any chemical waste that creates disposal problems. In the given reports we have successfully
procured both of these advantages.
One of the earliest and remarkable assertation was made in 1912 by Giacomo Ciamician. In his visionary
lecture, he promptly anticipated the sunlight as an alternative energy source for the future.19 He also
speculated for a clean, environment friendly and economically viable chemical industry that could replace theconventional processes.
In photochemical protocols, one of the major concerns is the selection of a suitable light source along withthe ability of molecules to absorb the light and cost effectiveness. Solar radiation is clean, renewable, safe,
inexpensive and abundant source of energy that leaves no residue in harmony with the principles of green
chemistry.18 The use of solar radiation is reported only for a few reactions.20-23 The need of the hour is todevelop the methodologies that can effectively harness the solar energy. Concentrated solar radiation (CSR)
has been proved to be very effective in a very few recent reports24-25 because of focused beam and easy
handling that provided higher yield in short duration of time.
Benzimidazoles are one of the most extensively explored and acclaimed motifs for their prominent
presence in huge number of potentially significant molecules26-32 that show various applications inpharmaceuticals, polymers and dyes. Some of the important drugs (Figure 1) are Omeprazole, Esomeprazole,and Lansoprazole which are commonly used in the treatment of gastroesophageal reflux disease33-35
preventing the formation of stomach acid by inhibiting the functioning of H +/K+-ATPase. Due to its broad
spectrum of applications, substantial efforts have been made to develop the competent methods for its
preparation.

Figure 1. Some important benzimidazoles.
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Established methods involve various oxidative reagents to react the o-phenylenediamine with different
aldehydes, carboxylic acids and its derivatives. 36-45 Some of these methods have also reported the use of toxic
and expensive metal catalysts, organic solvents, and long reaction time. In a latest report,46 benzimidazoles
were synthesized using visible light in blue region by taking methanol as a suitable solvent. Blue light in thevisible spectrum, from 400 to 450 nm, known as high-energy visible light and have the potential for a
photochemical-induced retinal injury even in the indirect exposure.47-49 To overcome such problems and makethe processes viable under economic and environmental conditions, there is need to develop the competentphotochemical methods stimulated by visible light wavelengths which are abundant in the solar spectrum.

NH2

Catalyst / Solvent
Temperatureref. 36-45

NH2Blue LED (7W)
MeOH, RT, 2href. 46

+
O

H
N
N

X

X = H, OH

CSR, 30 min.
this work

Scheme 1. Synthesis of benzimidazoles.
In the present study we developed the environmentally friendly benign approach for the formation of C-Nbond and synthesized various potential derivatives of functionalized benzimidazoles using concentrated solar
radiation maintaining its reproducibility.

Results and Discussion
To find an optimized protocol, we started this study with the initial reaction between o-phenylenediamine (1.0
equiv.) 1 and benzaldehyde (1.0 equiv.) 2a in MeCN in the presence of air bubbling at room temperature
under Non-concentrated solar radiation (Non-CSR) for 8 h, and only 57% of the desired product 3a (entry 1,
Table 1) was obtained. This reaction was also monitored at 2 h and 4 h interval under the same reaction
conditions, but the product formation was less than 40%. Subsequently we increased the reaction time upto
12 h that improved the reaction yield (entry 2, Table 1). Reaction was observed for another 2h but that did
not improve the yield significantly.
The reaction was also carried out with different solvent systems such as MeOH, EtOH, with and without
the air bubbling for up to 12 h (entries 3-5, Table 1) in Non-CSR and observed, MeCN under aerobic conditions
was the most suitable solvent for this protocol that improved the yield to 72%. Air bubbling showed asignificant improvement in yield of the desired product at room temperature.

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Table 1. Screening of the reaction conditions for the photochemical synthesis of 2-substituted
benzimidazoles[a]ONH2

H Light / Solvent free+

Reaction conditions

NH2
1

2a

H
N
N
3a

Reaction conditions
Entry

Yield(%)[b]Light

Solvent

O2

Time

1

Non-CSR[c]

MeCN

O2

8h

57

2

Non-CSR

MeCN

O2

12 h

72

3

Non-CSR

MeCN

-

12 h

35

4

Non-CSR

MeOH

O2

12 h

60

5

Non-CSR

EtOH

O2

12 h

52

6

Non-CSR

Water

O2

10 h

n.d.

7

MeCN

O2

30 min70

8

CSR (With
coolant)[d]CSR (With coolant)

Solvent-free-

45 min80

9

CSR

Solvent-free-

30 min88[a]Reagents and conditions. OPD 1 (1.0 mmol), aldehyde 2a (1.0 mmol), [b] isolated yield after purification, [c]Non-CSR: Non-concentrated solar radiation (Broad sunlight), [d] Water is used as coolant to dissipate the heatgenerated during the reaction in CSR.
We also explored the reaction in water under similar conditions; however, desired product was not evendetected (entry 6, Table 1). Even after getting the conditions optimized, results left us unsatisfied due tofollowing reasons: (a) long reaction time, (b) diffused and broad sunlight for the organic reactions to carry out,(c) low chances of reproducibility due to weather conditions and, (d) uneven solar intensity throughout theday. These reasons make the procedure impractical and further prompted us to explore the practical andviable protocol. We made a reconnaissance of observations and tried to use concentrated solar radiation (CSR)
for the purpose by using Fresnel lens as the concentrator. This gave us the excellent results. Initially we tried
the reaction in CSR with water as a coolant and MeCN as a solvent (entry 7, table 1). CSR produces photothermal effect and generates high temperature in a very short duration of time. Coolant (water) dissipates theheat and served the purpose very well in the given procedure. The yield obtained was 70%. Further, to extend
our dimensions, we tried the reaction in solvent free medium under similar conditions (entry 8, table 1) which
could provide 80% yield in 45 min. We performed the same reaction in solvent-free medium under CSR
without using any coolant that showed marvellous results. CSR excellently represented its photo-thermal
effect and the reaction accomplished with 88% yield in just 30 minutes (entry 9, table 1).
The reactions were performed during 12.30-3.30pm when the solar radiations are reportedly minimally
inclined with maximum intensity. This CSR protocol could fulfil all the gaps of the previously applied nonPage 4©

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Concentrated Solar Radiation (non-CSR) and proved to be practical, environment friendly and green procedurethat also achieved scalability and reproducibility.

Figure 2: Schematic representation of experimental CSR Photochemical setup. a(aAll the experiments were conducted under similar conditions at Kapurthala, Punjab, India 30° 19′ 51.71″ N,
75° 29′ 24.97″ E/30.33103N, 75.490268E)
With the optimized conditions in hand, we further evaluated and explored (Table 2) the generality of themethod and extended the protocol to other examples. We first studied the reaction of different substituted
benzaldehydes. It is worth mentioning here that the various substituents (both electron rich and electron
defficient) present on the phenyl ring presented corresponding benzimidazoles in good to excellent yields in avery short duration of time. Chloro substituted benzaldehydes provided corresponding products; 3b in very
good yield (75%) and 3c in 78% yield with lesser reaction time required. Another electron withdrawing
substituted benzaldehydes gave 3d in 70% yield and 3e in 62% yield. Electron donating substituted
benzaldehydes furnished desired products 3f, 3g & 3h in very good yields (77-82%). Further, the study was
also extended to some heterocyclic carboxaldehydes and the corresponding products 3j-3k were well isolated
in very good (81%) to excellent (90%) yield. 3l could be isolated in 42% yield only. Similarly, cinnamaldehyde
could make it through to furnish the desired products 3i under the optimized reaction conditions with a yieldof 55% only. In the latter case, the reaction was further extended to another 15 minutes under CSR; however,it also could not make any significant affect upon the product formation and its yield.

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Table 2. Photochemical extended scope of the optimized conditions in the synthesis of 2-substituted
benzimidazoles a,b
CHO
H
N

NH2
+
NH2

R

N

R

Cl

H
N

H
N

N

N

(3a, 88%)(3b, 75%)

H
N

H
N

H
N
Cl
N

(3c, 78%)
H
N

Br
N

(3d, 70%)(3e, 62%)
CH3

H
N(3f, 77%)

H
N

H
N

N

(3g, 78%)
H
N
N(3j, 81%)

b

CH3
N

OCH3

N

a

NO2

N

N

(3h, 82%)
S

H
N(3i, 55%)
N

H
N

N

N

(3k, 90%)(3l, 42%)O

Reaction conditions: o-phenylenediamine (1mmol), aldehyde (1mmol), in solvent-less system for 30 minutes.
Isolated yields are given in parenthesis.

Energy calculations
The energy requirements from external power supply for the synthesis of 2-substituted benzimidazoles using
the visible blue light and CSR are calculated. The energy consumed for the synthesis of 2-substituted
benzimidazoles is the total energy consumed (kJ) per unit weight of the total amount of the reactants used (g).
The reaction time to synthesise 2-substituted benzimidazoles was 120 min for visible blue light method and 30
min for the CSR. The amount of energy required to synthesize the 2-substituted benzimidazoles per gram is17.325 kJ/g and 132.3 kJ/g for CSR and visible light method respectively. Thus, CSR protocol proved to beenergy efficient with more than 85% energy saving and 75% reduction in time.
Energy consumed in visible light (Blue LED 7W). Total Energy consumed from the external power source inthis process = Energy consumed by blue LED in 2h (120 min.) + Energy consumed by Magnetic stirrer for 120
min.
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Total energy consumed from external power source by the 7W LED in 120 min. process = Power input in LED ×
Time required for completion of the reaction.
= 7 (J/s) × 120 × 60s = 50400 J = 50.4 kJ
Voltage input in magnetic stirrer (Model 2L Remi, India) = 220 V.
Current measured using a digital multi-meter = 35 mA = 35 × 10-3 A.
Power input in magnetic stirrer = Voltage input × Current measured = 220 (V) × 35 × 10 -3 (A) = 7.7 W (J/s).
Total energy consumed by the stirrer over 120 min. process = Power input in magnetic stirrer × Time requiredfor completion of the reaction.
= 7.7 (J/s) × 120 × 60s = 55440 J = 55.440 kJ
Total Energy consumed in the process = 50.4 (kJ) + 55.44 (kJ) = 105.84 kJ
Quantity of material processed = Quantity of (o-phenylenediamine + benzaldehyde) in g. = 0.4 + 0.4 = 0.8 g.
The amount of energy consumed from external power source to process material per gram = Net energy
consumed during Stirring/Quantity of reactants).
= 105.84(kJ)/0.8(g) = 132.3 kJ/g
Energy consumed in concentrated solar radiation (CSR). This work: Total Energy consumed from external
power supply in the process = Energy consumed by Magnetic stirrer in 30 min.
Energy consumed by the stirrer in 30 min. process = Power input in magnetic stirrer × Time required forcompletion of the reaction.
= 7.7 (J/s) × 30 min. × 60s = 13860 J = 13.860 kJ
Quantity of material processed = Quantity of (o-phenylenediamine + benzaldehyde) in g. = 0.4 + 0.4 = 0.8 g.
The amount of energy consumed during the process per gram = Net energy consumed during Stirring/Quantityof material processed).
= 13.860(kJ)/0.8(g) = 17.325 kJ/g
Energy saving. The amount of energy saved during the process = Net energy consumed from the external
power supply for processing of material using blue LED method for 2 h – Energy consumed from external
power supply for processing of material using CSR = (132.3–17.325) kJ/g = 114.97 kJ/g
Energy saved during the process (%) = (the amount of energy saved during the process/Net energy supplied
for processing of material using conventional method) × 100= (114.97/132.3) × 100 = 86.90%

Conclusions
This protocol presents an expedient, energy efficient, sustainable, atom economical, and eco-friendly
unprecedented method for the synthesis of functionalized benzimidazoles. A wide range of aldehydes werestudied to this new synthetic methodology to afford functionalized benzimidazoles with good efficiencies
under very benevolent reaction conditions. In addition, solar radiation, no extra reagents and operational
simplicity prove it as a novel and innovative striking mode of the present-day organic synthesis. This method is
also proved to be remarkable energy saving with tremendously lower reaction time.

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Experimental Section
General. Oxygen- and moisture-sensitive reactions were carried out under nitrogen atmosphere. Solventswere purified and dried by standard methods prior to use. All commercially available reagents and solvents(purchased from Aldrich, Merck, Spectrochem, Acros) were used without further purification unless otherwise
noted. Analytical thin layer chromatography (TLC) was conducted on Merck Kieselgel 60 F254. Column
chromatography was performed on silica gel (100-200 mesh). Melting points were determined in capillarytubes using a Mel-Temp apparatus and are not corrected. Infrared spectra were obtained as films on KBr salt
plates except where otherwise specified, using a Perkin Elmer FT-IR spectrometer. 1H NMR spectra wereobtained with CDCl3 at 500 MHz, using Bruker spectrometers (residual chloroform referenced to 7.26 ppm) or
DMSO- d6 (residual DMSO referenced to 2.50 ppm and residual water in DMSO- d6 appearing at 3.34 ppm).
Chemical shift values are expressed as parts per million downfield from TMS and J values are in hertz. Splitting
patterns are indicated as s: singlet, d: doublet, t: triplet, m: multiplet, dd: double doublet, ddd: doublet of adoublet of a doublet, and br: broad peak. 13C NMR spectra were recorded with CDCl3 at 75 MHz, using Bruker
spectrometers (residual chloroform referenced to 77.0 ppm) or DMSO- d6 (residual DMSO referenced to 39.5
ppm). HRMS were recorded on Bruker high resolution spectrometer (BrukermicrOTOF QII).
General procedure for synthesis of compound 2-aryl-1H-benzimidazoles 3. In a typical experiment, a mixtureof aromatic aldehyde 2 (1mmol) and o-phenylenediamine (1) (1 mmol) was taken in a test tube. The reaction
mixture was stirred on magnetic stirrer in concentrated solar radiation (CSR) for 20-30 minutes and monitored
by TLC. On completion of the reaction, the reaction mixture was cooled to room temperature. The 2-aryl-1Hbenzimidazoles 3 were isolated by using column chromatography over Silica gel using hexane-EtOAc as eluent
as and when required.
2-Phenyl-1H-benzo[d]imidazole (3a). Yield 88%; light brown solid; mp 293-294 °C; 1H NMR (500 MHz, DMSOd6) δ 13.01 (br s, 1H), 8.19 (d, J 9.0 Hz, 2H), 7.69 (d, J 7.5 Hz, 1H), 7.53 (m, 4H), 7.18 (m, 2H); 13C NMR (DMSOd6, 75Hz): δ 112.1, 118.8, 122.9, 123.7, 126.8, 128.7, 129.1, 131.0, 135.2, 144.9, 151.4. MS m/z 195 (M+1);
Anal. Calc. for C13H10N2: C, 80.39; H, 5.19; N, 14.42; found: C, 80.43; H, 5.22; N, 14.33.
2-(2-Chlorophenyl)-1H-benzo[d]imidazole (3b). Yield 75%; Off white solid; mp 230-232 oC 1H NMR (500 MHz,DMSO-d6) δ 12.79 (br s, 1H), 7.91 (dd, 1H), 7.66 (dd, J 8Hz, 1H), 7.50-7.56 (m, 1H), 7.26-7.23 (m, 5H) ppm; 13C
NMR (DMSO-d6, 75Hz): δ 149.5, 132.5, 132.1, 131.7, 130.8, 130.4, 127.9, 122.1, 118.9, 111.8, 111.5 ppm; MS
m/z 229 (M+1); Anal. Calc. for C13H9ClN2: C, 68.28; H, 3.97; N, 12.25; found: C, 68.27; H, 3.99; N, 12.21.
2-(4-Chlorophenyl)-1H-benzo[d]imidazole (3c). Yield 78%; pale yellow solid; 1H NMR (500 MHz, DMSO-d6) δ
12.96 (br s, 1H), 8.20 (d, J 8.5 Hz, 2H), 7.68 (d, J 7.5 Hz, 1H), 7.61 (d, J 9.5 Hz, 2H), 7.53 (m, 1H), 7.23 (m, 2H);
13
C NMR (DMSO-d6, 75Hz): δ 111.7, 118.6, 121.5, 123.0. 128.5, 128.7, 129.1, 134.8, 135.2, 143.2, 150.2. MS
m/z 229 (M+1); Anal. Calc. for C13H9ClN2: C, 68.28; H, 3.97; N, 12.25; found: C, 68.30; H, 3.98; N, 12.20.
2-(4-Bromophenyl)-1H-benzo[d]imidazole (3d). Yield 70%; pale yellow solid; mp 254-255 °C; 1H NMR (500
MHz, DMSO-d6) δ 13.05 (br s, 1H), 8.12 (m, 2H), 7.78 (d, J 8.0 Hz, 2H), 7.67 (s, 1H), 7.55 (s, 1H), 7.21 (s, 2H); 13C
NMR (DMSO-d6, 75Hz): δ 111.8, 188.8, 122.3, 123.6, 123.8, 128.5, 129.0, 129.9, 135.2, 143.5, 150.1. MS m/z
273 (M+1); Anal. Calc. for C13H9BrN2: C, 57.17; H, 3.32; N, 10.26; found: C, 57.19; H, 3.35; N, 10.22.
2-(4-Nitrophenyl)-1H-benzo[d]imidazole (3e). Yield 62%; pale yellow solid; 1H NMR (500 MHz, DMSO-d6) δ
13.22 (br s, 1H), 8.38 (m, 4H), 7.67 (s, 2H), 7.27 (s, 2H); 13C NMR (DMSO-d6, 75Hz): δ 115.1, 122.8, 124.5, 124.6,
127.8, 127.9, 134.5, 136.2, 147.7, 149.3, 150.1. MS m/z 240 (M+1); Anal. Calc. for C13H9N3O2: C, 65.27; H, 3.79;
N, 17.56; found: C, 65.35; H, 3.83; N, 17.55.

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2-(p-Tolyl)-1H-benzo[d]imidazole (3f). Yield 77%; white solid; mp 275-276 °C; 1H NMR (500 MHz, DMSO-d6) δ
12.85 (br s, 1H), 8.06 (d, J 7.5 Hz, 2H), 7.63 (s, 1H), 7.52 (s, 1H), 7.33 (m, 2H), 7.19 (s, 2H), 2.37 (s, 3H); 13C NMR(DMSO-d6, 75Hz): δ 21.1, 111.3, 118.7, 121.5, 122.4, 126.6, 127.4, 129.5, 135.1, 139.8, 143.8, 151.1. MS m/z
209 (M+1); Anal. Calc. for C14H12N2: C, 80.74; H, 5.81; N, 13.45; found: C, 80.80; H, 5.83; N, 13.44.
2-(m-Tolyl)-1H-benzo[d]imidazole (3g). Yield 78%; white solid; mp 232-233 °C; 1H NMR (500 MHz, DMSO-d6) δ
12.88 (br s, 1H), 8.03 (s, 1H), 7.97 (d, J 7.5 Hz, 1H), 7.55 (m, 3H), 7.31 (d, J 7.0 Hz, 1H), 7.18 (m, 2H), 2.40 (s,3H); 13C NMR (DMSO-d6, 75Hz): δ 21.5, 111.7, 119.3, 122.2, 122.8, 124.0, 127.5, 129.3, 130.2, 130.8, 135.5,
138.6, 144.2, 151.9. MS m/z 209 (M+1); Anal. Calc. for C14H12N2: C, 80.74; H, 5.81; N, 13.45; found: C, 80.76; H,
5.88; N, 13.41.
2-(4-Methoxyphenyl)-1H-benzo[d]imidazole (3h). Yield 82%; pale yellow solid; 1H NMR (500 MHz, DMSO-d6) δ
12.87 (br s, 1H), 8.10 (d, J 7.5 Hz, 2H), 7.53 (s, 2H), 7.12 (m, 4H), 3.86 (s, 3H); 13C NMR (DMSO-d6, 75Hz): δ 55.5,
111.9, 114.1, 114.8, 121.1, 122.4, 128.5, 151.8, 164.9. MS m/z 225 (M+1); Anal. Calc. for C14H12N2O: C, 74.98;
H, 5.39; N, 12.49; found: C, 75.02; H, 5.44; N, 12.47.
(E)-2-Styryl-1H-benzo[d]imidazole (3i). Yield 55%; pale yellow solid; 1H NMR (500 MHz, DMSO-d6) δ 12.99 (brs, 1H), 7.75 (m, 2H), 7.36 (m, 6H), 7.18 (m, 2H), 7.05 (d, J 7.5 Hz, 1H); 13C NMR (DMSO-d6, 75Hz): δ 111.7,
121.3, 122.1, 127.3, 128.3, 128.7, 133.4, 37.5, 152.9. MS m/z 221 (M+1); Anal. Calc. for C15H12N2: C, 81.79; H,
5.49; N, 12.72; found: C, 81.85; H, 5.51; N, 12.64.
2-(Thiophen-2-yl)-1H-benzo[d]imidazole (3j). Yield 81%; pale yellow solid; mp 342-344 °C; 1H NMR (500 MHz,DMSO-d6) δ 12.99 (br s, 1H), 7.83 (d, J 4.0 Hz, 1H), 7.71 (d, J 5.5 Hz, 1H), 7.60 (s, 1H), 7.51 (s, 1H), 7.22 (m, 3H);
13
C NMR (DMSO-d6, 75Hz): δ 111.3, 118.9, 121.2, 122.9, 127.6, 128.7, 129.6, 134.0, 135.1, 143.3, 147.7. MS
m/z 201 (M+1); Anal. Calc. for C11H8N2S: C, 65.97; H, 4.03; N, 13.99; found: C, 65.99; H, 4.10; N, 13.91.
2-(Pyridin-2-yl)-1H-benzo[d]imidazole (3k). Yield 90%; pale yellow solid; 1H NMR (500 MHz, DMSO-d6) δ 13.10(br s, 1H), 8.73 (m, 1H), 8.05 (d, J 7.5 Hz, 1H), 7.79 (m, 3H), 7.73 (m, 1H), 7.20 (m, 2H); 13C NMR (DMSO-d6,
75Hz): δ 112.0, 119.5, 122.7, 123.4, 135.1, 137.6, 144.3, 148.6, 151.1. MS m/z 196 (M+1); Anal. Calc. for
C12H9N3: C, 73.83; H, 4.65; N, 21.52; found: C, 73.88; H, 4.67; N, 21.50.
2-(Furan-2-yl)-1H-benzo[d]imidazole (3l). Yield 42%; pale yellow solid; 1H NMR (500 MHz, DMSO-d6) δ 12.88(br s, 1H), 7.87 (m, 2H), 7.51 (m, 2H), 7.05 (d, J 3.5 Hz, 1H), 6.08 (m, 2H); 13C NMR (DMSO-d6, 75Hz): δ 110.1,
111.0, 113.2, 121.7, 137.3, 137.9, 151.1, 155.9. MS m/z 185 (M+1); Anal. Calc. for C11H8N2O: C, 71.73; H, 4.38;
N, 15.21; found: C, 71.74; H, 4.44; N, 15.15.

Acknowledgments
The support and research facilities provided by I. K. Gujral Punjab Technical University (PTU), Kapurthala arehighly acknowledged.

Supplementary Material
Copies of 1H and 13C NMR spectra of representative compounds are available in the supplementary material
file.

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