Synthesis and antimicrobial activity of benzazolyl azolyl urea derivatives

Article abstract of DOI:10.1016/j.molstruc.2019.126871

A new class of benzazolyl azolyl urea derivatives were prepared by the reaction of methyl benzazoyl carbamates with azolyl amines in the presence of mild base potassium tert-butoxide. The presence of electron withdrawing substituents on the aromatic ring enhanced the activity. Nitro substituted benzothiazolyl thiazolyl urea, benzothiazolyl imidazolyl urea and benzimidazolyl thiazolyl urea exhibited potential antibacterial activity against Bacillus subtilis. The compound benzothiazolyl imidazolyl urea and nitro substituted benzimidazolyl imidazolyl urea showed potential antifungal activity against Aspergillus niger.

Full text of DOI:10.1016/j.molstruc.2019.126871

Journal Pre-proof
Synthesis and antimicrobial activity of benzazolyl azolyl urea derivatives
Kayathi Narendra babu, Ummadi Nagarjuna, Guda Dinneswara Reddy, Adivireddy
Padmaja, Venkatapuram Padmavathi
PII:
S0022-2860(19)30962-7
DOI:
https://doi.org/10.1016/j.molstruc.2019.126871
MOLSTR 126871
Reference:
To appear in: Journal of Molecular Structure
Received Date: 11 December 2018
Revised Date: 26 July 2019
Accepted Date: 30 July 2019
Please cite this article as: K. Narendra babu, U. Nagarjuna, G.D. Reddy, A. Padmaja, V. Padmavathi,
Synthesis and antimicrobial activity of benzazolyl azolyl urea derivatives, Journal of Molecular Structure
(2019), doi: https://doi.org/10.1016/j.molstruc.2019.126871.
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2019 Published by Elsevier B.V.

Synthesis and Antimicrobial Activity of Benzazolyl Azolyl Urea Derivatives
1
1
2
Kayathi Narendra babu ● Ummadi Nagarjuna ● Guda Dinneswara Reddy ●
1
1
Adivireddy Padmaja ● Venkatapuram Padmavathi
1
Department of Chemistry, Sri Venkateswara University, Tirupati, Andhra Pradesh,
India.
Email: vkpuram2001@yahoo.com
2
Department of chemistry and medicinal chemistry, College of science and technology,
Yonci University, Wonju, Gangwon, South korea.
Graphical abstract
Abstract
A new class of benzazolyl azolyl urea derivatives were prepared by the reaction of methyl
benzazoyl carbamates with azolyl amines in the presence of mild base potassium tert-
butoxide. The presence of electron withdrawing substituents on the aromatic ring enhanced
the activity. Nitro substituted benzothiazolyl thiazolyl urea, benzothiazolyl imidazolyl urea
and benzimidazolyl thiazolyl urea exhibited potential antibacterial activity against Bacillus
subtilis. The compound benzothiazolyl imidazolyl urea and nitro substituted benzimidazolyl
imidazolyl urea showed potential antifungal activity against Aspergillus niger.

Keywords: Heterocycles, benzazoles, Cyclocondensation, antimicrobial activity,
MBC/MFC.
INTRODUCTION
Azoles contain N=C-X moiety serve as important building blocks for the development of
various natural products and biologically potential molecules. Many oxazole derivatives such
as Inthomycin C, Oxaprozin, Bengazole A have featured in pharmaceutical arena [1] (Fig. 1).
Sulfathiazole [2] and Tiazofurin are some of the drugs having thiazole unit [3]. Imidazole
ring is present as an integral part of clinically used drugs like Azomycin and Pilocarpine [4].
Molecules with benzoxazole, benzothiazole and benzimidazole moieties are attractive targets
for synthesis, since they often exhibit diverse activities such as antibacterial, antibiotic,
antiparasitic, anti-inflammatory, antistress and anticancer [5]. In fact some of the drugs -
Frentizole [6], Albendazole [7], Calcimycin [8], Febendazole [9], Omeprazole [4],
Bentaluron [10] and Flunoxaprofen [11] possess benzazole moiety. In continuation of our
interest towards the development of a variety of heterocycles linked by different
pharmacophores [12,13,14] the present work - synthesis and antimicrobial activity of
benzazolyl azolyl urea derivatives has been taken up.

HO
HO
H
O
O
N
N
HO
O
HO
O
Fig. 1. Drugs containing Azole and Benzazole moieties.

RESULTS AND DISCUSSION
Chemistry
Benzoxazolyl-2-amine (1) and benzimidazolyl-2-amine (3) were prepared from
2
-aminophenol or o-phenylenediamine on reaction with cyanogen bromide [15].
Benzothiazolyl-2-amine (2) was obtained from aniline and ammonium thiocyanate in the
presence of bromine in acetic acid [16]. The oxazolyl-2-amine (7) and thiazolyl-2-amine (8)
were prepared from phenacyl bromide on treatment with urea and thiourea [17,18].
Imidazolyl-2-amine (9) was obtained by the reaction of phenacyl bromide with guanidine
hydrochloride followed by hydrolysis [19]. Treatment of 1 with methyl chloroformate under
ultrasonication at a frequency of 35 kHz resulted in methyl benzo[d]oxazol-2-ylcarbamate
(4). Similarly methyl benzo[d]thiazol-2-ylcarbamate (5) and methyl 1H-benzo[d]imidazol-2-
ylcarbamate (6) were prepared by the reaction of 2 and 3 with methyl chloroformate [20].
1
The H NMR spectra of 4, 5 and 6 displayed a singlet at δ 3.67, 3.71 and 3.77 ppm due to
methoxy protons and a broad singlet at δ 10.46, 10.52 and 10.56 ppm due to NH. The
compound 6 showed another broad singlet at δ 10.59 ppm due to benzimidazole NH. The
reaction of 4 with 7 in the presence of potassium tert-butoxide in THF under ultrasonication
resulted in 1-(benzo[d]oxazol-2-yl)-3-(4-aryl)oxazol-2-yl)urea (10). Similarly reaction of 4
with 8 and 9 furnished 1-(benzo[d]oxazol-2-yl)-3-(4-aryl)thiazol-2-yl)urea (11) and 1-
1
(
benzo[d]oxazol-2-yl)-3-(4-aryl)-1H-imidazol-2-yl)urea (12). The H NMR spectra of 10a,
1
1a and 12a showed a broad singlet at δ 8.48, 8.38, and 8.87 ppm due to two NH protons.
The compound 12a exhibited another broad singlet at δ 11.41 ppm due to imidazole NH.
Adopting similar methodology 1-(benzo[d]thiazol-2-yl)-3-(4-aryl)oxazol-2-yl)urea (13), 1-
(benzo[d]thiazol-2-yl)-3-(4-aryl)thiazol-2-yl)urea (14) and 1-(benzo[d]thiazol-2-yl)-3-(4-
aryl)-1H-imidazol-2-yl)urea (15) were prepared by the reaction of 5 with 7, 8 and 9,
respectively. The compounds 13a, 14a and 15a displayed a broad singlet at δ 8.78, 8.74 and

8
.41 ppm for two NH protons. The compound 15a also exhibited another broad singlet at δ
1.32 ppm due to imidazole NH. Likewise, the reaction of 6 with 7, 8 and 9 furnished 1-(1H-
1
benzo[d]imidazol-2-yl)-3-(4-aryl)oxazol-2-yl)urea (16), 1-(1H-benzo[d]imidazol-2-yl)-3-(4-
aryl)thiazol-2-yl)urea (17) and 1-(1H-benzo[d]imidazol-2-yl)-3-(4-aryl)-1H-imidazol-2-
1
yl)urea (18). The H NMR spectra of 16a, 17a and 18a showed a broad singlet at δ 8.46, 8.51
and 8.36 ppm due to two NH protons. The compounds 16a and 17a showed another broad
singlet at δ 11.02, 11.44 ppm due to benzimidazole NH while 18a displayed two broad
singlets at δ 11.43, 11.04 ppm due to imidazole NH and benzimidazole NH. The signals of
highly acidic protons in all the compounds disappeared on deuteration. All the compounds
are obtained in fairly good yields irrespective of the heteroatom present in azolyl amines
(7/8/9). However, imidazolyl-2-amines reacted with benzazolyl carbamates (4/5/6) at faster
rate (2.5-3.0 hrs) than oxazolyl-2-amines (4.5-5 hrs) and thiazolyl-2-amines (3.15-4 hrs)
Scheme
Ar
O
X
X
N
(i)
N
NH2
N
OMe
NH2
N
Y
H
1
/2/3
4/5/6
7/8/9
(
ii)
Ar
O
N
X
N
N
N
H
Y
H
1
0ꢀ18
1
0 X = Y = O
Ar ꢀ a) Cl
(
i) ClCO Me / Et N / DCM / ))))
1,4,7 X = O
2
3
1
1
1
1
1
1
1
1
1 X = O; Y = S
2 X =O; Y= NH
3 X = S; Y= O
4 X = Y = S
5 X=S; Y= NH
6 X= NH; Y= O
7 X= NH; Y= S
8 X= Y = NH
(
ii) KOtꢀBu / THF / ))))
2
3
,5,8 X = S
,6,9 X = NH
b) Br
c) NO2

EXPERIMENTAL
Apparatus and analysis
Melting points were determined in open capillaries on a Mel-Temp apparatus and are
uncorrected. The purity of the compounds was checked by TLC (silica gel H, BDH, ethyl
acetate / hexane, 1:3). The IR spectra were recorded on a Thermo Nicolet IR 200 FT-IR
–
1
1
13
spectrometer as KBr pellets and the wave numbers were given in cm . The H and C NMR
spectra were recorded in DMSO-d on a Bruker-400 spectrometer operating at 400 and 100
6
MHz. All chemical shifts are reported in
δ (ppm) using TMS as an internal standard. The
high-resolution mass spectra were recorded on micromass Q-TOF micromass spectrometer
using electrospray ionization. The microanalyses were performed on a Perkin-Elmer 240C
elemental analyzer. Ultrasonication was performed in a BandelinSonorex RK 102H
ultrasonic bath operating at a frequency of 35 KHz. The progress of the reaction was
monitored by TLC using silica gel plates (silica gel 60 F254 0.25 mm) and components were
visualized by observation under UV light (254 and 365 nm).
General procedure for the synthesis of 1-(benzo[d]oxazol-2-yl)-3-(4-aryl)oxazol-2-yl)urea
(10)/ 1-(benzo[d]oxazol-2-yl)-3-(4-aryl)thiazol-2-yl)urea (11)/ 1-(benzo[d]oxazol-2-yl)-3-(4-
aryl)-1H-imidazol-2-yl)urea (12)/ 1-(benzo[d]thiazol-2-yl)-3-(4-aryl)oxazol-2-yl)urea (13)/
1-(benzo[d]thiazol-2-yl)-3-(4-aryl)thiazol-2-yl)urea (14)/ 1-(benzo[d]thiazol-2-yl)-3-(4-aryl)-
1H-imidazol-2-yl)urea (15)/ 1-(1H-benzo[d]imidazol-2-yl)-3-(4-aryl)oxazol-2-yl)urea (16)/
1-(1H-benzo[d]imidazol-2-yl)-3-(4-aryl)thiazol-2-yl)urea (17)/ 1-(1H-benzo[d]imidazol-2-
yl)-3-(4-aryl)-1H-imidazol-2-yl)urea (18)
A mixture of KOt-Bu (1.1 mmol) in THF (5 ml) was sonicated at room temperature for 3
min. To this, methyl benzazoyl carbamate (4/5/6) (1 mmol) and benzazolyl amine (7/8/9) (1
mmol) were added and sonication was continued (2.5-5 hrs) until amine was consumed. THF
was evaporated under reduced pressure and diluted with water (10 ml). It was extracted with

CH Cl (20 ml) and dried over anhydrous MgSO . The solvent was removed under reduced
2
2
4
pressure and solid obtained was recrystallized from ethanol.
1
-(Benzo[d]oxazol-2-yl)-3-(4-(4-chlorophenyl)oxazol-2-yl)urea (10a)
White crystalline solid 0.2554 g, Yield: (72%), mp (melting point): 143-145 C. H NMR
DMSO-d ) (ppm): δ : 7.28-7.46 (m, C3, C6, 2H, Ar), 7.53-7.55 (m, C4, C5, 2H, Ar), 7.56-
O
1
(
6
1
3
7
.65 (m, C3'', C4'', C5'', C6'', 4H, Ar), 7.72 (s, C5', 1H) 8.48 (bs, 2H, NH) ppm;
C
NMR(DMSO-d ) (ppm): δ : 157.2 (C-2), 147.5 (C-2'), 143.3 (C-4'), 136.1 (C-5'), 164.6
6
(C=O), 114.2, 117.6, 122.3, 125.1, 127.4, 127.9, 128.5, 132.7, 138.0, 142.4 (aromatic
-1
carbons); IR (KBr) cm :
= 1568 (C=N), 1617 (C=C), 1640 (CONH), 3348 (NH); HRMS
(
m/z): 377.7391 [M+Na]; Elemental analysis: (C H ClN O ): Theo. (%): C, 57.56; H,
1
7
11
4
3
3
.13; N, 15.79; experimental (%): C, 57.64; H, 3.06; N, 15.86.
-(Benzo[d]oxazol-2-yl)-3-(4-(4-bromophenyl)oxazol-2-yl)urea (10b)
1
O
1
White crystalline solid 0.2994 g, Yield: (75%); mp (melting point): 138-140 C. H NMR
(
DMSO-d ) (ppm): δ : 7.31-7.42 (m, C3, C6, 2H, Ar), 7.45-7.58 (m, C4, C5, 2H, Ar), 7.59-
6
13
7
.71 (m, C3'', C4'', C5'', C6'', 4H, Ar), 7.71 (s, C5', 1H), 8.42 (bs, 2H, NH);
C
NMR(DMSO-d ) (ppm): δ : 158.4 (C-2), 146.6 (C-2'), 142.9 (C-4'), 138.5 (C-5'), 165.7
6
(C=O), 116.9, 118.5, 122.0, 124.8, 126.7, 127.2, 128.0, 133.3, 137.4, 142.1 (aromatic
-1
carbons); IR (KBr) cm :
= 1559 (C=N), 1614 (C=C), 1645 (CONH), 3342 (NH); HRMS
(
m/z): 422.1946 [M+Na]; Elemental analysis: (C H BrN O ): Theo. (%): C, 51.22; H,
1
7
11
4
3
2
.84; N, 13.92; experimental (%): C, 51.15; H, 2.78; N, 14.03.
-(Benzo[d]oxazol-2-yl)-3-(4-(4-nitrophenyl)oxazol-2-yl)urea (10c)
1
O
1
White crystalline solid 0.2527 g, Yield: (69%); mp (melting point): 167-169 C. H NMR
(
DMSO-d ) (ppm): δ : 7.35-7.51 (m, C3, C6, 2H, Ar), 7.61-7.63 (m, C4, C5, 2H, Ar), 7.83-
6
13
7
.94 (m, C3'', C4'', C5'', C6'', 4H, Ar), 7.75 (s, C5', 1H), 8.61 (bs, 2H, NH);
C

NMR(DMSO-d ) (ppm): δ : 159.3 (C-2), 148.4 (C-2'), 143.2 (C-4'), 136.9 (C-5'), 166.2
6
(C=O), 115.5, 117.2, 122.7, 125.8, 128.0, 128.6, 129.1, 133.8, 138.5, 143.7 (aromatic
-
1
carbons); IR (KBr) cm :
m/z): 389.2956 [M+Na]; Elemental analysis: Theo. (%): C, 55.97; H, 3.00; N, 19.26;
experimental (%): C, 55.89; H, 3.04; N, 19.17.
-(Benzo[d]oxazol-2-yl)-3-(4-(4-chlorophenyl)thiazol-2-yl)urea (11a)
White crystalline solid 0.2521 g, Yield: (68%); mp (melting point) : 155-157 C. H NMR
= 1574 (C=N), 1623 (C=C), 1642 (CONH), 3361 (NH); HRMS
(
1
O
1
(
DMSO-d ) (ppm): δ : 7.36-7.49 (m, C3, C6, 2H, Ar), 7.52-7.74 (m, C4, C5, 2H, Ar), 7.87-
6
13
7
.97 (m, C3'', C4'', C5'', C6'', 4H, Ar), 7.77 (s, C5', 1H), 8.38 (bs, 2H, NH);
C
NMR(DMSO-d ) (ppm): δ : 161.6 (C-2), 150.2 (C-2'), 146.5 (C-4'), 108.6 (C-5'), 165.4
6
(C=O), 118.5, 119.9, 122.7, 125.6, 127.8, 128.4, 129.0, 132.9, 138.6, 142.8 (aromatic
-1
carbons); IR (KBr) cm :
= 1563 (C=N), 1621 (C=C), 1641 (CONH), 3353 (NH); HRMS
(
m/z): 393.8001 [M+Na]; Elemental analysis: (C H ClN O S) Theo. (%): C, 55.98; H,
1
7
11
4
2
3
.05; N, 15.17; experimental (%): C, 55.06; H, 2.99; N, 15.11.
-(Benzo[d]oxazol-2-yl)-3-(4-(4-bromophenyl)thiazol-2-yl)urea (11b)
1
O
1
White crystalline solid 0.2988 g, Yield: (72%); mp (melting point): 164-166 C. H NMR
(
DMSO-d ) (ppm): δ : 7.35-7.41 (m, C3, C6, 2H, Ar), 7.46-7.53 (m, C4, C5, 2H, Ar), 7.64-
6
13
7
.81 (m, C3'', C4'', C5'', C6'', 4H, Ar), 8.01 (s, C5', 1H), 8.52 (bs, 2H, NH);
C
NMR(DMSO-d ) (ppm): δ : 162.9 (C-2), 151.5 (C-2'), 145.9 (C-4'), 110.8 (C-5'), 166.7
6
(C=O), 119.8, 121.8, 122.6, 125.3, 127.6, 127.9, 128.7, 133.7, 138.9, 143.7 (aromatic
-1
carbons); IR (KBr) cm : = 1561 (C=N), 1619 (C=C), 1644 (CONH), 3349 (NH); HRMS
(
m/z): 438.2558 [M+Na]; Elemental analysis: (C H BrN O S) Theo. (%): C, 49.09; H,
17 11 4 2
2
.64; N, 13.58; experimental (%): C, 49.17; H, 2.67; N, 13.49.

1
-(Benzo[d]oxazol-2-yl)-3-(4-(4-nitrophenyl)thiazol-2-yl)urea (11c)
O
1
White crystalline solid 0.2708 g, Yield (71%); mp (melting point): 169-171 C. H NMR
(
DMSO-d ) (ppm): δ : 7.40-7.54 (m, C3, C6, 2H, Ar), 7.56-7.74 (m, C4, C5, 2H, Ar), 7.78-
6
13
7
.98 (m, C3'', C4'', C5'', C6'', 4H, Ar), 7.75 (s, C5', 1H), 8.87 (bs, 2H, NH);
C
NMR(DMSO-d ) (ppm): δ : 160.5 (C-2), 149.51 (C-2'), 146.2 (C-4'), 109.3 (C-5'), 167.1
6
(C=O), 118.3, 120.2, 123.0, 125.9, 128.4, 128.8, 131.5, 133.9, 139.1, 143.5 (aromatic
-1
carbons); IR (KBr) cm : = 1582 (C=N), 1625 (C=C), 1651 (CONH), 3372 (NH); HRMS
(
m/z): 404.3567 [M+Na]; Elemental analysis: (C H N O S) Theo. (%): C, 53.60; H, 2.96;
17
11
5
4
N, 18.49; experimental (%): C, 53.54; H, 2.91; N, 18.36.
-(Benzo[d]oxazol-2-yl)-3-(4-(4-chlorophenyl)-1H-imidazol-2-yl)urea (12a)
1
O
1
White solid 0.2405 g, Yield (68%); mp (melting point): 157-159 C. H NMR (DMSO-d )
6
(ppm): δ : 7.37-7.41 (m, C3, C6, 2H, Ar), 7.42-7.49 (m, C4, C5, 2H, Ar), 7.50-7.63 (m, C3'',
C4'', C5'', C6'', 4H, Ar), 7.64 (s, C5', 1H), 8.87 (bs, 2H, NH), 11.41 (bs, 1H, imidazole NH);
1
3
C NMR(DMSO-d ) (ppm): δ : 155.2 (C-2), 148.4 (C-2'), 142.6 (C-4'), 124.7 (C-5'), 168.9
6
(C=O), 117.4, 118.8, 120.7, 122.8, 124.4, 127.6, 128.6, 131.4, 138.1, 141.3 (aromatic
-
1
-1
carbons); IR (KBr) cm :
= 1560 (C=N), 1620 (C=C), 1645 (CONH), 3363 (NH) cm ;
HRMS (m/z): 376.7565 [M+Na]; Elemental analysis: (C H ClN O ) Theo. (%): C, 57.81;
17
12
5
2
H, 3.47; N, 19.93; experimental (%): C, 57.72; H, 3.42; N, 19.80.
-(Benzo[d]oxazol-2-yl)-3-(4-(4-bromophenyl)-1H-imidazol-2-yl)urea (12b)
1
O
1
White solid 0.2628 g, Yield (66%); mp (melting point): 168-170 C. H NMR (DMSO-d )
6
(ppm): δ : 7.25-7.33 (m, C3, C6, 2H, Ar), 7.43-7.49 (m, C4, C5, 2H, Ar), 7.51-7.57 (m, C3'',
C4'', C5'', C6'', 4H, Ar), 7.58-7.62 (m, C5', 1H), 8.91 (bs, 2H, NH), 11.49 (bs, 1H, imidazole
1
3
NH); C NMR(DMSO-d ) (ppm): δ : 153.9 (C-2), 149.1 (C-2'), 140.5 (C-4'), 127.2 (C-5'),
6
1
69.1 (C=O), 116.6, 119.8, 122.4, 124.2, 126.9, 127.7, 128.5, 132.6, 134.8, 140.2 (aromatic
-1
carbons); IR (KBr) cm : = 1558 (C=N), 1618 (C=C), 1648 (CONH), 3360 (NH); HRMS

(
m/z): 421.2091 [M+Na]; Elemental analysis: (C H BrN O ) Theo. (%): C, 51.20; H,
17 12 5 2
3
.00; N, 17.65; experimental (%): C, 51.27; H, 3.04; N, 17.59.
-(Benzo[d]oxazol-2-yl)-3-(4-(4-nitrophenyl)-1H-imidazol-2-yl)urea (12c)
1
O
1
White solid 0.2586 g, Yield (71%); mp (melting point): 180-170 C. H NMR (DMSO-d )
6
(ppm): δ : 7.31-7.49 (m, C3, C6, 2H, Ar), 7.57-7.62 (m, C4, C5, 2H, Ar), 7.67-7.83 (m, C3'',
C4'', C5'', C6'', 4H, Ar), 7.89 (s, C5', 1H), 8.98 (bs, 2H, NH), 11.90 (bs, 1H, imidazole NH);
1
3
C NMR(DMSO-d ) (ppm): δ : 154.5 (C-2), 147.3 (C-2'), 143.8 (C-4'), 129.6 (C-5'), 170.4
6
(C=O), 116.6, 118.2, 123.0, 125.4, 128.0, 129.9, 131.1, 133.8, 135.7, 141.2 (aromatic
-1
carbons); IR (KBr) cm : = 1587 (C=N), 1625 (C=C), 1651 (CONH), 3379 (NH); HRMS
(
m/z): 387.3116 [M+Na]; Elemental analysis: (C H N O ) Theo. (%): C, 56.17; H, 3.27;
17
12
6
4
N, 22.98; experimental (%): C, 56.05; H, 3.32; N, 23.07.
-(Benzo[d]thiazol-2-yl)-3-(4-(4-chlorophenyl)oxazol-2-yl)urea (13a)
1
O
1
White solid 0.2595 g, Yield (70%); mp (melting point): 155-157 C. H NMR (DMSO-d )
6
(ppm): δ : 7.24-7.26 (m, C3, C6, 2H, Ar), 7.35-7.37 (m, C4, C5, 2H, Ar), 7.44-7.59 (m, C3'',
1
3
C4'', C5'', C6'', 4H, Ar), 7.63 (s, C5', 1H), 8.78 (bs, 2H, NH); C NMR(DMSO-d ) (ppm): δ
6
:
173.7 (C-2), 151.5 (C-2'), 142.8 (C-4'), 138.5 (C-5'), 168.0 (C=O), 118.2, 121.5, 123.8,
-1
1
26.3, 127.4, 128.1, 128.9, 129.7, 135.5, 148.6 (aromatic carbons); IR (KBr) cm : = 1563
(C=N), 1622 (C=C), 1648 (CONH), 3356 (NH); HRMS (m/z): 393.8018 [M+Na]; Elemental
analysis: (C H ClN O S) Theo. (%): C, 55.13; H, 2.93; N, 15.19; experimental (%): C,
17
11
4
2
5
5.06; H, 2.99; N, 15.11.
1
-(Benzo[d]thiazol-2-yl)-3-(4-(4-bromophenyl)oxazol-2-yl)urea (13b)
O
1
White solid 0.2990 g, Yield (72%); mp (melting point): 149-151 C. H NMR (DMSO-d )
6
(ppm): δ : 7.27-7.38 (m, C3, C6, 2H, Ar), 7.49-7.53 (m, C4, C5, 2H, Ar), 7.55-7.71 (m, C3'',
1
3
C4'', C5'', C6'', 4H, Ar), 7.72 (s, C5', 1H), 8.69 (bs, 2H, NH); C NMR(DMSO-d ) (ppm): δ
6
:
171.6 (C-2), 152.3 (C-2'), 143.7 (C-4'), 136.3 (C-5'), 167.2 (C=O), 119.8, 122.5, 124.7,

-1
1
25.3, 126.1, 126.9, 127.6, 128.1, 132.2, 144.8 (aromatic carbons); IR (KBr) cm : = 1557
(
C=N), 1619 (C=C), 1654 (CONH), 3351 (NH); HRMS (m/z) HRMS (m/z): 438.2555
M+Na]; Elemental analysis: (C H BrN O S) Theo. (%): C, 49.25; H, 2.74; N, 13.58;
[
17
11
4
2
experimental (%): C, 49.17; H, 2.67; N, 13.49.
-(Benzo[d]thiazol-2-yl)-3-(4-(4-nitrophenyl)oxazol-2-yl)urea (13c)
1
O
1
Pale yellow solid 0.2860 g, Yield (75%); mp (melting point) :156-158 C. H NMR (DMSO-
d6) (ppm): δ : 7.33-7.39 (m, C3, C6, 2H, Ar), 7.41-7.51 (m, C4, C5, 2H, Ar), 7.83-7.92 (m,
1
3
C3'', C4'', C5'', C6'', 4H, Ar), 7.81 (s, C5', 1H), 8.92 (bs, 2H, NH); C NMR(DMSO-d )
6
(ppm): δ : 174.9 (C-2), 153.2 (C-2'), 141.1 (C-4'), 138.7 (C-5'), 166.6 (C=O), 118.7, 122.0,
-
1
1
23.6, 124.3, 125.7, 126.8, 128.1, 129.8, 137.2, 146.3 (aromatic carbons); IR (KBr) cm :
1579 (C=N), 1627 (C=C), 1652 (CONH), 3381 (NH); HRMS (m/z): 404.3550 [M+Na];
Elemental analysis: (C H N O S) Theo. (%): C, 53.48; H, 2.94; N, 18.47; experimental
=
17
11
5
4
(%): C, 53.54; H, 2.91; N, 18.36.
1
-(Benzo[d]thiazol-2-yl)-3-(4-(4-chlorophenyl)thiazol-2-yl)urea (14a)
O
1
White solid 0.2669 g, Yield (69%); C H ClN OS ; mp (melting point) : 167-169 C. H
1
7
11
4
2
NMR (DMSO-d ) (ppm): δ : 7.44-7.49 (m, C3, C6, 2H, Ar), 7.51-7.63 (m, C4, C5, 2H, Ar),
6
13
7
.64-7.73 (m, C3'', C4'', C5'', C6'', 4H, Ar), 7.98 (s, C5', 1H), 8.74 (bs, 2H, NH);
C
NMR(DMSO-d ) (ppm): δ : 174.6 (C-2), 167.2 (C-2'), 148.3 (C-4'), 108.4 (C-5'), 168.6
6
(C=O), 118.6, 120.5, 122.4, 123.6, 124.9, 126.2, 127.5, 128.1, 133.8, 138.4 (aromatic
-1
carbons); IR (KBr) cm : = 1569 (C=N), 1624 (C=C), 1646 (CONH), 3362 (NH); HRMS
(
m/z): 409.8625 [M+Na]; Elemental analysis: (C H N O S) Theo. (%): C, 52.86; H, 2.94;
1
7
11
5
4
N, 14.41; experimental (%): C, 53.54; H, 2.87; N, 14.48.

1
-(Benzo[d]thiazol-2-yl)-3-(4-(4-bromophenyl)thiazol-2-yl)urea (14b)
O
1
White solid 0.2976 g, Yield (69%); mp (melting point) : 173-175 C. H NMR (DMSO-d )
6
(ppm): δ : 7.48-7.56 (m, C3, C6, 2H, Ar), 7.57-7.69 (m, C4, C5, 2H, Ar), 7.72-7.94 (m, C3'',
1
3
C4'', C5'', C6'', 4H, Ar), 8.01 (s, C5', 1H), 8.68 (bs, 2H, NH); C NMR(DMSO-d ) (ppm): δ
6
:
176.8 (C-2), 166.6 (C-2'), 149.6 (C-4'), 109.1 (C-5'), 167.9 (C=O), 119.1, 120.8, 121.7,
-1
1
23.8, 125.3, 126.7, 128.8, 128.1, 132.4, 136.2 (aromatic carbons); IR (KBr) cm : = 1561
(C=N), 1621 (C=C), 1653 (CONH), 3359 (NH); HRMS (m/z): 454.3167 [M+Na]; Elemental
analysis: (C H BrN OS ) Theo. (%): C, 47.39; H, 2.52; N, 13.07; experimental (%): C,
1
7
11
4
2
4
7.34; H, 2.57; N, 12.99.
-(Benzo[d]thiazol-2-yl)-3-(4-(4-nitrophenyl)thiazol-2-yl)urea (14c)
1
O
1
Pale yellow solid 0.2702 g, Yield (68%); mp (melting point) : 189-191 C. H NMR
(
DMSO-d ) (ppm): δ : 7.51-7.54 (m, C3, C6, 2H, Ar), 7.70-7.73 (m, C4, C5, 2H, Ar), 7.92-
6
13
8
.08 (m, C3'', C4'', C5'', C6'', 4H, Ar), 7.86 (s, C5', 1H), 8.85 (bs, 2H, NH);
C
NMR(DMSO-d ) (ppm): δ : 173.4 (C-2), 168.7 (C-2'), 147.7 (C-4'), 109.5 (C-5'), 169.1
6
(C=O), 120.3, 121.5, 123.8, 125.2, 127.4, 129.7, 130.6, 131.7, 133.8, 138.7 (aromatic
-1
carbons); IR (KBr) cm : = 1582 (C=N), 1629 (C=C), 1650 (CONH), 3382 (NH); HRMS
(
m/z): 420.4176 [M+Na]; Elemental analysis: (C H N O S ) Theo. (%): C, 51.44; H, 2.74;
1
7
11
5
3 2
N, 17.70; experimental (%): C, 51.38; H, 2.79; N, 17.62.
-(Benzo[d]thiazol-2-yl)-3-(4-(4-chlorophenyl)-1H-imidazol-2-yl)urea (15a)
1
O
1
Pale yellow solid 0.2404 g, Yield (65%); mp (melting point) : 180-182 C. H NMR
(
DMSO-d ) (ppm): δ : 7.39-7.43 (m, C3, C6, 2H, Ar), 7.46-7.55 (m, C4, C5, 2H, Ar), 7.57-
6
7
.86 (m, C3'', C4'', C5'', C6'', 4H, Ar), 7.98 (s, C5', 1H), 8.41 (bs, 2H, NH), 11.32 (bs, 1H,
13
imidazole NH); C NMR(DMSO-d ) (ppm): δ : 176.7 (C-2), 154.1 (C-2'), 142.6 (C-4'),
6
1
20.3 (C-5'), 167.5 (C=O), 122.2, 125.3, 126.9, 128.4, 130.9, 132.1, 133.7, 134.6, 138.9,

-1
1
42.8 (aromatic carbons); IR (KBr) cm :
= 1566 (C=N), 1627 (C=C), 1641 (CONH),
3
349 (NH); HRMS (m/z): 392.8177 [M+Na]; Elemental analysis: (C H ClN OS) Theo.
1
7
12
5
(%): C, 55.15; H, 3.33; N, 18.81; experimental (%): C, 55.21; H, 3.27; N, 18.94.
1
-(Benzo[d]thiazol-2-yl)-3-(4-(4-bromophenyl)-1H-imidazol-2-yl)urea (15b)
O
1
Pale yellow solid 0.2982 g, Yield (72%); mp (melting point) : 174-176 C. H NMR
(
DMSO-d ) (ppm): δ : 7.36-7.52 (m, C3, C6, 2H, Ar), 7.62-7.68 (m, C4, C5, 2H, Ar), 7.71-
6
7
.90 (m, C3'', C4'', C5'', C6'', 4H, Ar), 7.91 (s, C5', 1H), 8.48 (bs, 2H, NH), 11.42 (bs, 1H,
13
imidazole NH); C NMR(DMSO-d ) (ppm): δ : 176.4 (C-2), 153.7 (C-2'), 140.4 (C-4'),
6
1
1
3
21.7 (C-5'), 166.3 (C=O), 119.8, 121.9, 123.9, 125.7, 127.8, 128.2, 129.9, 133.8, 139.3,
-1
40.7 (aromatic carbons); IR (KBr) cm :
= 1569 (C=N), 1626 (C=C), 1635 (CONH),
352 (NH); HRMS (m/z): 437.2717 [M+Na]; Elemental analysis: (C H BrN OS) Theo.
1
7
12
5
(%): C, 49.20; H, 2.97; N, 17.03; experimental (%): C, 49.29; H, 2.92; N, 16.91.
1
-(Benzo[d]thiazol-2-yl)-3-(4-(4-nitrophenyl)-1H-imidazol-2-yl)urea (15c)
O
1
Pale yellow solid 0.2586 g, Yield (68%); mp (melting point) : 196-198 C. H NMR
DMSO-d ) (ppm): δ : 7.39-7.46 (m, C3, C6, 2H, Ar), 7.48-7.53 (m, C4, C5, 2H, Ar), 7.54-
(
6
7
.84 (m, C3'', C4'', C5'', C6'', 4H, Ar), 7.98 (s, C5', 1H), 8.80 (bs, 2H, NH), 11.87 (bs, 1H,
13
imidazole NH); C NMR(DMSO-d ) (ppm): δ : 177.9 (C-2), 155.5 (C-2'), 139.2 (C-4'),
6
1
1
3
20.4 (C-5'), 168.0 (C=O), 121.4, 123.4, 125.6, 127.2, 129.9, 130.4, 132.0, 134.1, 140.5,
-1
44.2 (aromatic carbons); IR (KBr) cm :
= 1578 (C=N), 1634 (C=C), 1642 (CONH),
368 (NH); HRMS (m/z): 403.9729 [M+Na]; Elemental analysis: (C H N O S) Theo.
1
7
12
6
3
(%): C, 53.61; H, 3.21; N, 22.15; experimental (%): C, 53.68; H, 3.18; N, 22.09.
1
-(1H-Benzo[d]imidazol-2-yl)-3-(4-(4-chlorophenyl)oxazol-2-yl)urea (16a)
O
1
White solid 0.2476 g, Yield (70%); mp (melting point) : 161-163 C. H NMR (DMSO-d )
6
(ppm): δ : 7.29-7.41 (m, C3, C6, 2H, Ar), 7.49-7.51 (m, C4, C5, 2H, Ar), 7.56-7.66 (m, C3'',
C4'', C5'', C6'', 4H, Ar), 7.79 (s, C5', 1H), 8.46 (bs, 2H, NH), 11.02 (bs, 1H, imidazole NH);

1
3
C NMR(DMSO-d ) (ppm): δ : 147.2 (C-2), 153.6 (C-2'), 140.9 (C-4'), 136.8 (C-5'), 168.5
6
-1
(
C=O), 118.4, 123.5, 124.8, 126.6 127.1, 128.9, 133.3 (aromatic carbons); IR (KBr) cm :
-1
=
1563 (C=N), 1624 (C=C), 1640 (CONH), 3354 (NH) cm ; HRMS (m/z): 376.7559
[
M+Na]; Elemental analysis: (C H ClN O ) Theo. (%): C, 57.80; H, 3.46; N, 19.91;
17 12 5 2
experimental (%): C, 57.72; H, 3.42; N, 19.80.
-(1H-Benzo[d]imidazol-2-yl)-3-(4-(4-bromophenyl)oxazol-2-yl)urea (16b)
1
O
1
White solid 0.2748 g, Yield (69%); mp (melting point) : 157-159 C. H NMR (DMSO-d )
6
(ppm): δ : 7.34-7.43 (m, C3, C6, 2H, Ar), 7.46-7.54 (m, C4, C5, 2H, Ar), 7.56-7.83 (m, C3'',
C4'', C5'', C6'', 4H, Ar), 7.85 (s, C5', 1H), 8.43 ( bs, 2H, NH), 11.33 (bs, 1H, benzimidazole
1
3
NH); C NMR(DMSO-d ) (ppm): δ : 149.6 (C-2), 152.7 (C-2'), 141.6 (C-4'), 135.5 (C-5'),
6
1
66.3 (C=O), 119.9, 122.9, 125.2, 126.9, 127.9, 130.3, 133.8 (aromatic carbons); IR (KBr)
-
1
-1
cm :
= 1560 (C=N), 1618 (C=C), 1648 (CONH), 3349 (NH) cm ; HRMS (m/z):
4
1
21.2090 [M+Na]; Elemental analysis: (C H BrN O ) Theo. (%): C, 51.35; H, 3.09; N,
17
12
5
2
7.67; experimental (%): C, 51.27; H, 3.04; N, 17.59.
-(1H-Benzo[d]imidazol-2-yl)-3-(4-(4-nitrophenyl)oxazol-2-yl)urea (16c)
1
O
1
White solid 0.2659 g, Yield (73%); mp (melting point) : 178-180 C. H NMR (DMSO-d )
6
(ppm): δ : 7.38-7.54 (m, C3, C6, 2H, Ar), 7.63-7.70 (m, C4, C5, 2H, Ar), 7.73-7.91 (m, C3'',
C4'', C5'', C6'', 4H, Ar), 7.92 (s, C5', 1H), 8.82 ( bs, 2H, NH), 11.35 (bs, 1H, benzimidazole
1
3
NH); C NMR(DMSO-d ) (ppm): δ : 148.3 (C-2), 154.5 (C-2'), 144.0 (C-4'), 137.9 (C-5'),
6
1
69.8 (C=O), 120.2, 122.3, 125.5, 126.9, 128.4, 131.1, 134.6 (aromatic carbons); IR (KBr)
-
1
cm :
= 1589 (C=N), 1632 (C=C), 1647 (CONH), 3376 (NH); HRMS (m/z): 387.3117
[
M+Na]; Elemental analysis: (C H N O ) Theo. (%): C, 56.12; H, 3.38; N, 22.98;
17
12
6
4
experimental (%): C, 56.05; H, 3.32; N, 23.07.

1
-(1H-Benzo[d]imidazol-2-yl)-3-(4-(4-chlorophenyl)thiazol-2-yl)urea (17a)
O
1
White solid 0.2588g, Yield (70%); mp (melting point): 186-188 C. H NMR (DMSO-d )
6
(ppm): δ : 7.34-7.54 (m, C3, C6, 2H, Ar), 7.62-7.67 (m, C4, C5, 2H, Ar), 7.77-7.83 (m, C3'',
C4'', C5'', C6'', 4H, Ar), 7.85 (s, C5', 1H), 8.51 ( bs, 2H, NH), 11.44 (bs, 1H, benzimidazole
1
3
NH); C NMR(DMSO-d ) (ppm): δ : 147.7 (C-2), 158.3 (C-2'), 152.7 (C-4'), 109.8 (C-5'),
6
1
69.8 (C=O), 118.7, 123.8, 126.4, 128.9, 129.6, 131.5, 135.8 (aromatic carbons); IR (KBr)
-
1
cm :
= 1562 (C=N), 1626 (C=C), 1645 (CONH), 3343 (NH); HRMS (m/z): 392.8160
[
M+Na]; Elemental analysis: (C H ClN OS) Theo. (%): C, 55.29; H, 3.31; N, 19.05;
1
7
12
5
experimental (%): C, 55.21; H, 3.27; N, 18.94.
-(1H-Benzo[d]imidazol-2-yl)-3-(4-(4-bromophenyl)thiazol-2-yl)urea (17b)
1
O
1
White solid 0.2982 g, Yield (72%); mp (melting point) : 181-183 C. H NMR (DMSO-d )
6
(ppm): δ : 7.40-7.57 (m, C3, C6, 2H, Ar), 7.61-7.68 (m, C4, C5, 2H, Ar), 7.71-7.92 (m, C3'',
C4'', C5'', C6'', 4H, Ar), 7.94 (s, C5', 1H), 8.68 ( bs, 2H, NH), 11.49 (bs, 1H, benzimidazole
1
3
NH); C NMR(DMSO-d ) (ppm): δ : 147.2 (C-2), 156.8 (C-2'), 149.8 (C-4'), 110.7 (C-5'),
6
1
67.9 (C=O), 119.3, 123.2, 125.6, 127.4,128.8, 132.2, 136.0 (aromatic carbons); IR (KBr)
-
1
cm :
= 1557 (C=N), 1623 (C=C), 1642 (CONH), 3347 (NH); HRMS (m/z): 437.2716
[
M+Na]; Elemental analysis: (C H BrN OS) Theo. (%): C, 49.21; H, 2.88; N, 17.00;
17
12
5
experimental (%): C, 49.29; H, 2.92; N, 16.91.
-(1H-Benzo[d]imidazol-2-yl)-3-(4-(4-nitrophenyl)thiazol-2-yl)urea (17c)
1
O
1
White solid 0.2586 g, Yield (68%); mp (melting point) : 205-207 C. H NMR (DMSO-d )
6
(ppm): δ : 7.45-7.56 (m, C3, C6, 2H, Ar), 7.59-7.67 (m, C4, C5, 2H, Ar), 7.80-8.02 (m, C3'',
C4'', C5'', C6'', 4H, Ar), 7.79 (s, C5', 1H), 8.94 ( bs, 2H, NH), 11.67 (bs, 1H, benzimidazole
1
3
NH); C NMR(DMSO-d ) (ppm): δ : 148.8 (C-2), 157.1 (C-2'), 150.6 (C-4'), 109.5 (C-5'),
6
1
69.1 (C=O), 120.2, 121.6, 123.6, 125.9, 128.0, 129.5, 134.1 (aromatic carbons); IR (KBr)
-
1
cm :
= 1590 (C=N), 1635 (C=C), 1649 (CONH), 3378 (NH); HRMS (m/z): 403.3728

[
M+Na]; Elemental analysis: (C H N O S) Theo. (%): C, 53.59; H, 3.15; N, 21.98;
17 12 6 3
experimental (%): C, 53.68; H, 3.19; N, 22.09.
-(1H-Benzo[d]imidazol-2-yl)-3-(4-(4-chlorophenyl)-1H-imidazol-2-yl)urea (18a)
1
O
1
Pale yellow solid 0.2434 g, Yield (69%); mp (melting point) : 211-213 C. H NMR
DMSO-d ) (ppm): δ : 7.37-7.49 (m, C3, C6, 2H, Ar), 7.56-7.62 (m, C4, C5, 2H, Ar), 7.64-
(
6
7
.80 (m, C3'', C4'', C5'', C6'', 4H, Ar), 7.83 (s, C5', 1H), 8.36 ( bs, 2H, NH), 11.04 (bs, 1H,
1
3
benzimidazole NH), 11.43 (bs, 1H imidazole NH); C NMR(DMSO-d ) (ppm): δ : 148.1
6
(C-2), 150.3 (C-2'), 142.2 (C-4'), 118.4 (C-5'), 168.6 (C=O), 122.5, 124.5, 126.0, 127.6,
-1
1
28.8, 131.9, 135.2 (aromatic carbons); IR (KBr) cm : = 1565 (C=N), 1629 (C=C), 1648
(
CONH), 3352 (NH); HRMS (m/z): 375.7727 [M+Na]; Elemental analysis: (C H ClN O)
17 13 6
Theo. (%): C, 57.80; H, 3.66; N, 23.98; experimental (%): C, 57.88; H, 3.71; N, 23.82.
-(1H-Benzo[d]imidazol-2-yl)-3-(4-(4-bromophenyl)-1H-imidazol-2-yl)urea (18b)
1
O
1
Pale yellow solid 0.2740 g, Yield (69%); mp (melting points) : 198-200 C. H NMR
DMSO-d ) (ppm): δ : 7.38-7.48 (m, C3, C6, 2H, Ar), 7.51-7.66 (m, C4, C5, 2H, Ar), 7.73-
(
6
7
.92 (m, C3'', C4'', C5'', C6'', 4H, Ar), 7.96 (s, C5', 1H),8.61 ( bs, 2H, NH), 11.24 (bs, 1H,
1
3
benzimidazole NH), 11.49 (bs, 1H, imidazole NH); C NMR(DMSO-d ) (ppm): δ : 149.0
6
(C-2), 152.6 (C-2'), 143.5 (C-4'), 119.6 (C-5'), 169.3 (C=O), 119.1, 121.2, 124.7, 125.62,
-1
1
27.5, 129.0, 133.7 (aromatic carbons); IR (KBr) cm : = 1562 (C=N), 1625 (C=C), 1651
(
CONH), 3348 (NH); HRMS (m/z): 420.2251 [M+Na]; Elemental analysis: (C H BrN O)
17 13 6
Theo. (%): C, 51.47; H, 3.24; N, 21.23; experimental (%): C, 51.40; H, 3.30; N, 21.16.
1
-(1H-Benzo[d]imidazol-2-yl)-3-(4-(4-nitrophenyl)-1H-imidazol-2-yl)urea (18c)
O
1
Pale yellow solid 0.2579 g, Yield (71%); mp (melting Point) : 224-226 C. H NMR
(
DMSO-d ) (ppm): δ : 7.46-7.62 (m, C3, C6, 2H, Ar), 7.72-7.83 (m, C4, C5, 2H, Ar), 7.92-
6
8
.05 (m, C3'', C4'', C5'', C6'', 4H, Ar), 7.86 (s, C5', 1H), 8.83 (bs, 2H, NH), 11.62 (bs, 1H,

1
3
benzimidazole NH), 11.74 (bs, 1H, imidazole NH); C NMR(DMSO-d ) (ppm): δ : 149.5
6
(C-2), 151.2 (C-2'), 141.8 (C-4'), 119.0 (C-5'), 167.8 (C=O), 118.2, 122.8, 124.6, 126.5,
-1
1
28.4, 129.6, 133.2 (aromatic carbons); IR (KBr) cm : = 1586 (C=N), 1633 (C=C), 1654
(
CONH), 3376 (NH); HRMS (m/z): 386.3278 [M+Na]; Elemental analysis: (C H N O )
17 13 7 3
Theo. (%): C, 56.28; H, 3.58; N, 27.08; experimental (%): C, 56.20; H, 3.61; N, 26.99.
ANTIMICROBIAL STUDIES
The compounds 10a-c – 18a-c were screened for antimicrobial activity at three different
concentrations 50, 75 and 100 ꢁg/mL.
Antimicrobial testing
The compounds 10a-c – 18a-c were dissolved in DMSO at different concentrations 50, 75
and 100 ꢁg/well. Bacterial strains Staphylococcus aureus, Bacillus subtilis, Pseudomonas
aeruginosa, Klebsiella pneumonia and fungi Aspergillus niger and Pencillium chrysogenum
were obtained from Department of Biotechnology, Sri Venkateswara University, Tirupati,
India.
Antibacterial and antifungal assays
The in vitro antimicrobial studies were carried out by agar well diffusion method against test
organisms [21]. Nutrient broth (NB) plates were swabbed with 24 h old broth culture (100
ꢁ
L) of test bacteria. Using the sterile cork borer, wells (6 mm) were made into each Petri
plate. The compounds were dissolved in DMSO of 5 mg/mL and from this 2.5, 5, 10 and 20
L (50, 75 and 100 ꢁg/mL) were added into the wells by using sterile pipettes.
ꢁ
Simultaneously the standard antibiotics, Chloramphenicol for antibacterial activity and
Ketoconazole for antifungal activity (as positive control) were tested against the pathogens.
The samples were dissolved in DMSO which showed no zone of inhibition acts as negative
o
o
control. The plates were incubated at 37 C for 24 h for bacteria and at 28 C for 48 h for
fungi. After appropriate incubation, the diameter of zone of inhibition of each well was

measured. Duplicates were maintained and the average values were calculated for eventual
antimicrobial activity. Broth dilution test was used to determine Minimum Inhibitory
Concentration (MIC) of the above mentioned samples [22]. Freshly prepared nutrient broth
was used as diluents. The 24 h old culture of the test bacteria S. aureus, B. subtilis, P.
aeruginosa and K. pneumoniae and the test fungi A. niger & P. chrysogenum were diluted
1
00 folds in nutrient broth (100 ꢁL bacterial cultures in 10 mL NB). The stock solution of the
synthesized compounds was prepared in DMSO by dissolving 5 mg of the compound in 1 mL
of DMSO. Increasing concentrations of the test samples (1.25, 2.5, 5, 10, 20, 40 ꢁL of stock
solution contains 6.25, 12.5, 25, 50, 100, 200 ꢁg of the compounds) were added to the test
o
tubes containing the bacterial and fungal cultures. All the tubes were incubated at 37 C for 24
o
h for bacteria and at 28 C for 48 h for fungi. The tubes were examined for visible turbidity
and using NB as control. Control without test samples and with solvent was assayed
simultaneously. The lowest concentration that inhibited visible growth of the tested
organisms was recorded as MIC. To determine the Minimum Bactericidal Concentration
(MBC) [23] and Minimum Fungicidal Concentration (MFC) [24] for each set of test tubes in
the MIC determination, a loopful of broth was collected from those tubes which did not show
any growth and inoculated on sterile nutrient broth (for bacteria) and PDA (for fungi) by
o
streaking. Plates inoculated with bacteria and fungi were incubated at 37 C for 24 h and at
o
2
8 C for 48 h, respectively. After incubation, the lowest concentration was noted as MBC
(for bacteria) or MFC (for fungi) at which no visible growth was observed.
Antibacterial activity
The compounds 10-18 were screened for antibacterial activity at three different
concentrations 50, 75, 100 µg/well and the results are presented in Table 1 Fig 2. All the
compounds showed higher antibacterial activity towards Gram-positive bacteria than on
Gram-negative bacteria. It was observed that thiazole in combination with benzothiazole (14)
displayed excellent antibacterial activity particularly against Bacillus subtilis. It was followed

by the compounds having imidazole - benzothiazole (15) and thiazole - benzimidazole units
17). On the other hand, compounds having imidazole - benzimidazole units (18) showed
moderate activity. Further it was observed that the compounds with oxazole - benzoxazole
10) and their combination with thiazole / benzothiazole (11, 13) or imidazole /
(
(
benzimidazole (12, 16) displayed least activity. Amongst 10-13 and 16 the compound 12
exhibited higher activity. The structure activity relationship revealed that with increasing
electronegativity of the substituents on the aromatic ring the activity increased. In fact the
compounds having nitro substituent showed greater activity than those with chloro and bromo
substituents in the respective series. Amongst halogen substituted compounds those having
chloro substituent showed higher activity. Further it was noticed that the compounds 14c, 15c
and 17c displayed activity greater than the standard drug chloramphenicol on Bacillus subtilis
at all tested concentrations.

Table 1. The in vitro antibacterial activity of compounds 10a-18c.
Diameter of zone of inhibition (mm)
Gram-positive bacteria
S. aureus B. subtilis
Gram-negative bacteria
P. aeruginosa K.pneumoniae
Compd.
No.
50
75 75
100
50
100
50
75
100
50
75
100
µg/well µg/well µg/well µg/well µg/well
µg/well
µg/well
µg/well
µg/well
µg/well
µg/well
µg/well
1
0a
0b
0c
-
-
-
-
8±1.3
7±1.6
9±1.3
-
-
9±1.2
-
10±1.1
9±1.3
-
-
-
7±1.2
6±1.0
10±1.2
9±1.8
7±1.6
12±1.1
-
-
9±1.4
8±1.3
1
-
-
-
-
1
-
8±1.4
-
8±1.1
11±1.6
16±1.1
14±1.3
20±2.1
13±1.8
18±1.5
17±1.1
22±1.7
-
8±1.3
7±1.4
-
-
9±1.2
11±1.6
10±1.2
15±1.3
11±1.4
13±1.1
12±1.4
18±1.1
11a
10±1.1 13±1.7 14±1.1
8±1.2 11±1.6 11±1.5
-
-
8±1.2
-
11b
1
1c
11±1.1 14±1.5 16±1.1 18±1.9
9±1.4
10±1.2
13±1.5
1
2a
13±1.5 15±1.9 17±1.6 19±1.4 21±1.7 24±1.8
9±1.1 11±1.4 13±1.6 16±1.3 17±1.1 19±1.5
19±1.6 22±1.4 25±1.2 28±2.0 30±2.1 33±1.4
12±1.1 13±1.4 15±1.2 17±1.6 18±1.4 21±1.7
10±1.2 12±1.5 13±1.3 16±1.2 14±1.5 19±1.6
14±1.1 17±1.4 18±1.3 20±2.1 22±1.9 23±1.4
23±1.4 26±2.1 28±1.6 30±2.4 32±2.2 35±1.6
12±1.4
10±1.3
17±1.4
8±1.1
-
14±1.1
16±1.3
17±1.2
12±1.1
24±1.2
14±1.6
11±1.5
16±1.4
28±1.4
20±1.4
16±1.6
27±1.9
16±1.3
14±1.6
19±1.3
32±2.1
22±1.8
19±1.7
30±1.6
17±1.5
16±1.4
20±1.7
34±1.9
12b
11±1.6 13±1.4
1
2c
20±1.6
10±1.3
7±1.2
22±1.3
11±1.4
10±1.3
15±1.6
26±1.6
1
3a
13b
1
3c
12±1.2
20±1.5
13±1.1
23±1.3
1
4a

1
4b
20±1.6 21±1.5 24±1.3 27±1.6 28±1.4 33±1.6
28±1.2 31±2.2 33±1.4 36±1.4 40±2.3 43±2.1
23±1.5 26±1.4 28±1.6 30±1.9 32±1.5 36±1.8
18±1.3 22±1.2 21±1.6 23±1.4 29±1.6 31±2.0
28±1.9 30±1.4 32±1.4 35±1.5 36±2.1 40±2.5
17±1.1
24±1.6
18±1.4
15±1.1
22±1.6
19±1.9
26±1.9
20±1.2
16±1.4
24±2.2
21±1.6
29±1.7
23±1.4
19±1.5
25±1.9
23±1.4
33±1.8
26±1.1
21±1.4
31±1.4
29±1.2
36±2.1
30±1.8
26±1.6
34±1.8
30±1.8
39±1.4
31±1.7
28±1.2
37±1.6
1
4c
5a
5b
5c
1
1
1
1
6a
6b
6c
7a
7b
7c
8a
8b
8c
-
-
-
7±1.1 8±1.4 10±1.6 11±1.5 14±1.3
7±1.2 9±1.1 11±1.4
9±1.4 12±1.2 12±1.4 14±1.2 16±1.1
-
7±1.3
-
9±1.6
8±1.4
-
8±1.6
-
10±1.2
-
1
-
-
-
-
1
9±1.4
18±1.5
14±1.5
21±1.4
13±1.1
10±1.4
19±1.3
25±1.7
12±1.7
20±1.6
15±1.2
24±1.9
15±1.8
12±1.6
21±1.5
27±2.2
14±1.5
22±1.8
18±1.4
27±1.7
16±1.4
13±1.7
23±1.6
30±2.6
11±1.3
26±1.7
22±1.8
30±1.5
18±1.7
15±1.4
27±1.8
38±1.4
14±1.4
29±2.0
26±2.0
33±1.4
23±1.4
17±1.9
28±1.9
40±2.1
16±1.7
32±1.9
28±1.8
36±1.6
24±1.2
19±1.3
33±2.1
42±2.5
1
20±1.5 22±1.9 26±1.4 28±1.8 32±1.7 34±1.4
15±1.4 19±1.1 21±1.4 26±1.5 25±1.7 29±1.4
25±1.2 28±1.4 30±1.5 33±1.7 36±1.3 39±2.5
14±1.4 17±1.1 20±1.3 21±1.4 23±1.5 25±1.6
12±1.2 16±1.1 17±2.4 19±2.3 21±1.5 22±1.9
22±1.4 23±1.6 27±2.4 30±2.0 31±1.6 36±1.4
1
1
1
1
1
Chloram- 30±2.5 33±1.7 35±2.4 32±2.5 34±2.6 38±1.7
phenicol
Control
DMSO)
-
-
-
-
-
-
-
-
-
-
-
-
(
(-) No activity. (±) Standard deviation

Figure 2. The in vitro antibacterial activity of compounds 10-18.
Antifungal activity
All the compounds are also evaluated for antifungal activity at 50, 75, 100 µg/well
concentrations and the results are presented in Table 2 Fig 3. All the compounds displayed
higher activity towards Aspergillus niger than on Penicillium chrysogenum. The compounds
having imidazole-benzimidazole (18) and imidazole-benzothiazole units (15) displayed
excellent antifungal activity on Aspergillus niger. It was also observed that those with
thiazole-benzimidazole units (17) showed moderate activity. The presence of electron
withdrawing substituents on the aromatic ring increased the activity. The compounds 15c and
1
8c displayed antifungal activity greater than the standard drug Ketoconazole against
Aspergillus niger at all tested concentrations.

Table 2. The in vitro antifungal activity of compounds 10a-18c.
Diameter of zone of inhibition (mm)
Compd.
No.
A. niger
P. chrysogenum
5
0 µg/well 75 µg/well 100 µg/well 50 µg/well 75 µg/well 100 µg/well
1
0a
0b
-
10±1.6
±1.3
11±1.8
10±1.6
14±1.7
12±1.5
11±1.6
18±1.8
-
-
9±1.4
±1.7
1
-
9
-
-
8
1
0c
9±1.4
10±1.6
7±1.2
12±1.7
13±1.8
11±1.4
8±1.1
-
10±1.5
10±1.9
7±1.4
15±1.7
11±1.9
9±2.0
1
1a
1b
-
-
1
7±1.6
1
1c
14±1.2
8±1.1
17±1.4
1
2a
2b
9
±1.4
-
10±1.8
7±2.0
12±1.5
9±1.4
7±2.1
-
9±1.8
-
11±1.2
8±2.0
1
1
2c
13±1.4
12±1.6
-
15±1.8
12±1.4
-
17±1.5
14±1.8
9±1.4
11±1.7
7±1.1
-
14±1.2
11±1.4
-
16±1.5
10±1.7
1
3a
3b
1
8±1.3
1
3c
19±1.4
18±1.8
14±1.4
27±1.6
24±1.4
21±1.3
32±2.4
16±1.4
12±1.2
19±1.4
22±1.3
18±1.1
29±1.4
26±1.8
21±1.5
34±2.5
31±1.6
-
22±2.4
20±1.7
16±1.5
29±1.7
26±1.8
22±1.5
36±1.8
19±1.8
14±1.1
21±1.2
24±2.0
21±1.8
31±2.5
28±1.2
23±1.4
35±2.7
33±2.4
-
25±2.2
24±1.5
18±1.8
32±2.5
29±1.6
25±1.8
37±1.4
23±1.7
17±1.4
26±1.5
28±2.2
23±1.7
34±2.1
31±1.4
26±1.2
39±1.8
36±2.6
-
14±1.6
13±1.2
9±1.1
23±1.8
22±1.3
14±1.4
26±1.2
12±1.4
8±1.5
16±1.7
19±1.8
15±1.4
24±1.8
22±1.9
17±1.1
28±1.7
35±2.5
-
16±1.3
15±1.4
11±14
25±1.4
24±1.7
19±1.7
29±1.3
14±1.7
10±1.6
18±1.5
20±1.4
17±1.8
26±1.7
24±1.6
19±1.7
30±1.5
36±1.9
-
19±1.5
18±1.3
14±1.7
28±1.5
26±1.2
22±1.7
31±1.9
17±1.5
14±1.9
20±1.6
23±1.7
21±1.6
29±1.9
27±1.4
24±1.5
34±1.2
38±1.7
-
1
4a
4b
1
1
4c
5a
5b
5c
6a
6b
6c
7a
7b
7c
8a
8b
8c
1
1
1
1
1
1
1
1
1
1
1
1
Ketoconazole
Control(DMSO)
(-) No activity. (±) Standard deviation

Figure 3. The in vitro antifungal activity of compounds 10-18.
The compounds which showed higher antimicrobial activity were further assayed for
minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and
minimum fungicidal concentration (MFC) and the results are presented in Table 3. MIC is the
lowest concentration of an antimicrobial that will inhibit the visible growth of
microorganism. The MBC/MFC is the lowest concentration of antibiotic required to kill a
particular bacterium/fungi. The MBC/MFC involves an additional set of steps performed
when once MIC is determined. The antimicrobials are usually regarded as
bactericidal/fungicidal if the MBC/MFC is not greater than four times the MIC [25]. The
compounds benzothiazolyl-4-(4-nitrophenyl) thiazolyl urea (14c), benzothiazolyl-4-(4-
nitrophenyl) imidazolyl urea (15c) and benzimidazolyl-4-(4-nitrophenyl) thiazolyl urea (17c)
displayed low MIC values against Bacillus subtilis and the MBC is 2 x MIC. The compounds
1
5c and benzimidazolyl-4-(4-nitrophenyl) imidazolyl urea (18c) exhibited low MIC values
against Aspergillus niger and MFC is 2 x MIC.

Table 3. MIC, MBC and MFC of compounds 14c, 15c, 17c and 18c
Minimum inhibitory concentration
Compound
MIC (MBC/MFC)
µg/well
S. aureus B. subtilis P. aeruginosa K.pneumoniae
A. niger
P.chrysogenum
1
1
4c
5c
25(100)
25(100)
6.25(12.5)
6.25(12.5)
12.5(200)
12.5(50)
12.5(50)
50(100)
12.5(50)
100(>200)
100(>200)
6.25(12.5)
1
7c
8c
50(200)
6.25(12.5)
12.5(50)
12.5(50)
50(100)
50(100)
12.5(50)
100(>200)
50(200)
1
100(>200)
100(>200)
6.25(12.5)
Chloramphenicol
Ketoconazole
6.25
—
6.25
—
6.25
—
12.5
—
—
—
6.25
12.5
(-) No activity.
CONCLUSION
A new class of benzazolyl azolyl urea derivatives were prepared from methyl benzazolyl
carbamates and azolyl amines in the presence of potassium tert-butoxide and tested for
antimicrobial activity. The presence of electron withdrawing chloro, bromo and nitro
substituents on the aromatic ring enhanced the activity. The activity increased with increasing
electronegativity of the substituents. Nitro substituted benzothiazolyl thiazolyl urea (14c),
benzothiazolyl imidazolyl urea (15c) and benzimidazolyl thiazolyl urea (17c) showed greater
antibacterial activity against Bacillus subtilis. The compounds 15C and nitro substituted
benzimidazolyl imidazolyl urea (18c) displayed greater antifungal activity against Aspergillus
niger.
ACKNOWLEDGEMENTS
The authors are grateful to CSIR (Council of Scientific and Industrial Research), New Delhi
for financial assistance under major research project.

REFERENCES
1
2
3
4
5
. EK. Ibrahim, S. Mustafa, E. Sahin, Y. Iamail, Preparation of novel pyrrol-2-one
derivatives via an effective synthesis of new oxazole scaffold, Tetrahedron 73 (2017)
1
795-1802.
. HY. Seong, HJ. Eun, J. Seulki, C. Soobin, K. Youngjoo, C. Sangwon, Photodegradation
of tetracycline and sulfathiazole individually and in mixtures, Accepted Manuscript, Food
and Chemical Toxicology (2018).
. P. Mirjana, K. Vesna, T. Ljilja, S. Milo, SS. Spai, J. Dimitar, A. Lidija, B. Gordana,
P. Velimir, Synthesis and in vitro antitumour activity of tiazofurin analogues with
nitrogen functionalities at the C-20 position, Eur J Med Chem 111 (2016) 114-125.
. L. Yurttas, M. Duran, S. Demirayak, H. Karaca Gencer, Y. Tunal, Synthesis and initial
biological evaluation of substituted 1-phenylamino-2-thio-4,5-dimethyl-1H-imidazole
derivatives, Bioorg. Med. Chem. Lett 23 (2013) 6764–6768.
. SP. Vikas, NB. Bhushan, DG. Vinod, RP. Kiran, SP. Vikas, GU. Prashant, NH. Sekhar,
G. Patrick, B. Ondrej, S. Ondrej, J. Jana, D. Rafael, K. Kamil, A. Laura, K. Terry,
Synthesis and antimicrobial activity of novel 2-substituted benzimidazole, benzoxazole
and benzothiazole derivatives, ArabianJournal of Chemistry 9 (2016) 1125–1130.
. H. Lukas, G. Patrick, B. Ondrej, S. Ondrej, J. Jana, D. Rafael, K. Kamil, A. Laura, K.S
Terry, GM. Frank, Z. Dominykas, RR. Rona, M. Kamil, Synthesis and evaluation of
frentizole based indolyl thiourea analogues as MAO/ABAD inhibitors for Alzheimer’s
disease treatment Bioorganic & Medicinal Chemistry 25 (2017) 1143–1152.
. WL. Stephanie, B. Samina, LM. David, HP. Mohammad, Potent Inhibition of Tubulin
Polymerisation and Proliferation of Paclitaxel-resistant 1A9PTX22 Human Ovarian
Cancer Cells by Albendazole, Anticancer research 29 (2009) 3791-3796.
6
7
8
. G. Igor, RP. Antonio, K. Tatyana, B. Petr, L. Marie, Calcium Ionophore, Calcimycin,

Kills Leishmania Promastigotes by Activating Parasite Nitric Oxide Synthase BioMed
Research International, Volume (2017), Article ID 1309485.
9
. G. Ping, VD. Chi, W. Julie, Unexpected Antitumorigenic Effect of Fenbendazole when
Combined with Supplementary Vitamins J Am Assoc Lab Anim Sci. 47(6) (2008)
3
7–40.
1
0. H .Wei, Y. Guang-Fu, Microwave-assisted, one-pot syntheses and fungicidal activity
of polyfluorinated 2-benzylthiobenzothiazoles,Bioorg. Med. Chem 14 (2006) 8280–
8
285.
1
1. C. Sacchi, F. Magni, A. Toia, F. Cazzaniga, G. Galli, F. Berti, flunoxaprofen, a new
non-steroidal anti-inflammatory drug, does not interfere with prostaglandin synthesis in
rat gastric mucosa, Pharmacological Research,Vol. 21 (1989) No. 2, 177
1
2. DV. Sowmya, GL. Teja, A. Padmaja, VK. Prasad, V. Padmavathi, Green approach for
the synthesis of thiophenyl pyrazoles and isoxazoles by adopting 1,3-dipolar
cycloaddition methodology and their antimicrobial activity, Eur J Med Chem 143
(2018) 891-898.
1
3. K. Divya, G. Sraya, A. Padmaja, V. Padmavthi, Synthesis and antimicrobial activity of
bis-heterocyclic sulfamoyl acetamides, Res. Chem. Immediates, 4 (2015) 7,
4
413–4426.
14. SS. Basha, K. Divya, A. Padmaja, V. Padmavthi, Synthesis and antimicrobial activity
of thiazolyl pyrazoles and isoxazoles, Res. Chem. Immediates December
4
1 (2015) 12, 10067–10083
1
5. V. Pilyugin, YA. Sapozhnikov, C. Davydov, G. Chikisheve, T. Vorobeva, E.
Klimakova, G. Kiseleva, S. Kuznetosova, R. Davletov, N. Sapozhnikov, R. Yamadilov,
Synthesis of bis(arylcarbonylamino-1H-benzimidazol-5-yl) ethers Russ J Gen Chem,
7
6 (2006) 8, 1327–1330.
16. A. Gupta, S. Rawat, Synthesis and Cyclization of Benzothiazole: Review, J Cur Pharm

Res 3 (2010) 1, 13-23
17. M. Gary, P. Noonan Allan, Dishington, J Pink, AD.Campbell, Studies on
the coupling of substituted 2- amino-1,3-oxazoles with chloro-heterocycles
Tetrahedron Letters 53 (2012) 24, 3038-3043
18. M. Kidwai, B. Dave, KR. Bhushan, Alumina-Supported Synthesis of Aminoazoles
Using Microwaves Chem. Papers 54 (2000) 4, 231-234
.
19. TL. Little, SE. Webber, A Simple and Practical Synthesis of 2-Aminoimidazoles
J Org Chem, 59 (1994) 24, 7299–7305.
20. M.Sustra, BS. Kenneth, Practical Synthesis of N-Alkyl-N-
alkyloxycarbonylaminomethyl prodrug Derivaties of Acetoaminophene, Theophylline,
and 6-Mercaptopurine Synthetic Communications, 36:353
21. KT. Chung, WR. Thomasson, CD. Wu-Yuan, Growth inhibition of selected food-borne
bacteria, particularly Listeria monocytogenes, by plant extracts. J. Appl. Bacteriol.
6
9 (1990) 4, 498-503.
2
2. D. Janovska, K. Kubikova, L. Kokoska, Screening for Antimicrobial Activity of Some
Medicinal Plants Species of Traditional Chinese Medicine J. of Food Sci. Vol.
2
1 (2003) 3, 107–110.
2
3. National Committee for Clinical Laboratory Standards, Methods for Dilution
Antimicrobial Susceptibility Tests for Bacteria that Grow Aerobically (2006)
Approved Standard, CLSI document M7-A7, 7th ed., Wayne, Pennsylvania, USA
2
4. National Committee for Clinical Laboratory Standards , Reference Method for Broth
Dilution Antifungal Susceptibility Testing of yeasts (2002). proposed standard,
NCCLS Document M27-A2, 2nd ed., Wayne, Pennsylvania, USA.
25. GL. French, Bactericidal agents in the treatment of MRSA infections--the potential role
of daptomycin.J Antimicrobe Chemother 58 (2006) 6,1107-1117.

Highlights
•
•
•
•
Benzazolyl azolyl urea derivatives were prepared by the reaction of azolyl carbamates with
azolyl amines in the presence of mild base.
The presence of electron withdrawing substituents on the aromatic ring enhanced
antimicrobial activity.
14c, 15c and 17c showed greater antibacterial activity on B.subtilis and than standard drug
Chloramphenicol.
15c and 18c showed excellent antifungal activity on A.niger than standard drug
Ketoconazole.