Synthesis and antibacterial activity of (E)-N′-[4-{2-(4-fluorophenylthio)ethoxy}-3-cyano-5-methoxybenzylidene]-substituted benzohydrazide derivatives

Article abstract of DOI:10.14233/ajchem.2016.19776

Commercially available vanillin was used as the starting material for the preparation of some new (E)-N′-[4-{2-(4-fluorophenylthio)-ethoxy}-3-cyano-5-methoxybenzylidene]-4-substituted benzohydrazide derivatives (8.1 to 8.10) in quantitative yields. The structural confirmations of all the newly synthesized hydrazone derivatives were established on the basis of ¹H NMR, mass and IR data. Hydrazides such as (E)-N′-[4-{2-(4-fluorophenylthio)ethoxy}-3-cyano-5-methoxybenzylidene]-2,5-dichlorobenzohydrazide (8.6), (E)-N′-[4-{2-(4-fluorophenylthio)ethoxy}-3-cyano-5-methoxybenzylidene]-2,5-difluorobenzohydrazide (8.9) showed duplication of NMR signals, this was attributed to the presence of anti and syn periplanar conformers. Antibacterial study against Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa with reference to the standard drug (streptomycin) revealed that compounds bearing R = 4-OH (8.2), 3,4,5-OMe (8.3) and 4-SO₂Me (8.4) substituents has shown the good antibacterial sensitivity.

Full text of DOI:10.14233/ajchem.2016.19776

Asian Journal of Chemistry; Vol. 28, No. 7 (2016), 1584-1588
A
SIAN
J
OURNAL OF HEMISTRY
C
http://dx.doi.org/10.14233/ajchem.2016.19776
Synthesis and Antibacterial Activity of (E)-N'-[4-{2-(4-Fluorophenylthio)ethoxy}-
3-cyano-5-methoxybenzylidene]-substituted benzohydrazide Derivatives
3
4
2
2
LOKAMAHESHWARI DOMMATI1,2,*, B. SATYANARAYANA , P. GAYATRI HELA , B. RAM and G. SRINIVAS
1Department of Chemistry, Jawaharlal Nehru Technological University, Hyderabad-500 072, India
2Green Evolution Laboratories, Wangapally Village-500 085, India
3Macleods Pharmaceuticals Ltd., Bhuvaneshwari Nagar, Andheri, Mumbai-400 059, India
4Siri Lifesciences, Banglore-560 066, India
*Corresponding author: E-mail: lokamaheshwari2015@gmail.com
Received: 14 December 2015;
Accepted: 13 February 2016;
Published online: 31 March 2016;
AJC-17853
Commercially available vanillin was used as the starting material for the preparation of some new (E)-N’-[4-{2-(4-fluorophenylthio)-
ethoxy}-3-cyano-5-methoxybenzylidene]-4-substituted benzohydrazide derivatives (8.1 to 8.10) in quantitative yields. The structural
confirmations of all the newly synthesized hydrazone derivatives were established on the basis of 1H NMR, mass and IR data. Hydrazides
such as (E)-N’-[4-{2-(4-fluorophenylthio)ethoxy}-3-cyano-5-methoxybenzylidene]-2,5-dichlorobenzohydrazide (8.6), (E)-N’-[4-{2-(4-
fluorophenylthio)ethoxy}-3-cyano-5-methoxybenzylidene]-2,5-difluorobenzohydrazide (8.9) showed duplication of NMR signals, this
was attributed to the presence of anti and syn periplanar conformers. Antibacterial study against Staphylococcus aureus, Bacillus subtilis,
Escherichia coli and Pseudomonas aeruginosa with reference to the standard drug (streptomycin) revealed that compounds bearing R = 4-
OH (8.2), 3,4,5-OMe (8.3) and 4-SO2Me (8.4) substituents has shown the good antibacterial sensitivity.
Keywords: Substituted benzohydrazide derivatives, Vanillin.
has become one of the most important areas of antibacterial
research today. In view of the above biological significance of
vanillin and hydrazone chemistry, we report here in the synthesis
and antibacterial activity of new hydrazone derivatives prepared
from commercially available vanillin.
INTRODUCTION
Vanillin (4-hydroxy-3-methoxybenzaldehyde), a compound
isolated from the bean and pod of tropical vanilla orchid is widely
used in the food and beverage industry and is responsible for
the characteristic vanilla flavour. This substance is also relevant
for the synthesis of different agrochemicals, antifoaming and
pharmaceutical products [1]. Some of the biological activities
exhibited by vanillin are antimicrobial activity [2-4], antimu-
tagenic [5,6] and anticarcinogenic actions [7], conversely, it
may also induce oxidative stress in yeast cells [8].
Hydrazide-hydrazones have also attracted a great deal of
interest due to their increased importance in medicinal
chemistry [9,10]. Isoniazid, a hydrazide derivative, is the front-
line drug currently employed in the treatment of tuberculosis
[11]. Hydrazone derivatives of isoniazid and other hydrazides
have been reported to display significant antimicrobial activity
[10-16]. Numerous substituted hydrazone derivatives have also
been synthesized and evaluated for their antitumor activity
and some promising results were reported [17,18].
EXPERIMENTAL
3-Methoxy-4-hydroxy-5-iodo benzaldehyde (2): A
mixture of vanillin (5 g, 32.86 mmol), CaCO3 (3.94 g, 39.43
mmol) in cyclopentylmethyl ether (100 mL) was cooled to
0 °C and added benzyltrimethylammonium dichloroiodate
(12 g, 34.50 mmol) in seven portions. The reaction mixture
was stirred at room temperature for 10 h. The precipitated
solids were filtered and dried under vaccum to afford 5-iodo-
vanillin (2).Yellow solid, m.p.: 183-184 °C,Yield: 8.2 g, 90 %;
IR (KBr, νmax, cm-1): 3297, 3076, 2843, 1740, 1663, 1563,
1493, 1458, 1408, 1363, 1290, 1250, 1210, 1128, 1084, 1035,
94, 900, 845, 815, 727, 665, 643; 1H NMR (400 MHz, CDCl3):
δ 10.04 (s,1 H), 9.73 (s, 1 H), 7.81 (s, 1 H), 7.34 (s, 1 H), 3.98
(s, 3 H); EI-MS: m/z, 278 [M+1].
Since resistance of pathogenic bacteria towards available
antibiotics is rapidly becoming a major worldwide problem,
the design of new compounds to deal with resistant bacteria
4-(2-Hydroxyethoxy)-3-iodo-5-methoxybenzaldehyde
(3): To a stirred solution of compound 2 (5 g, 17.0 mmol) in

Vol. 28, No. 7 (2016)
Synthesis and Antibacterial Activity of Substituted benzohydrazide Derivatives 1585
cyclopentylmethyl ether (50 mL) was added K2CO3 (2.58 g,
18.70 mmol) followed by 1-bromoethanol (18.7 mmol) and
heated to reflux for 4 h. After the completion of the reaction
(monitored by TLC), the reaction mixture was diluted with
water and washed with brine solution, dried on sodium
sulphate, filtered and concentrated to obtain compound 3. Pale
yellow solid; m.p.: 64-65 °C, Yield: 4.93 g, 85 %; IR (KBr,
7.01 (t, J = 8.6 Hz, 2H), 4.43 (t, J = 7.4 Hz, 2H), 3.89 (s, 3H),
3.27 (t, J = 7.4 Hz, 2H); EI-MS: m/z, 332 [M+1].
General experimental procedure for the synthesis
of hydrazones (8.1-8.10): A mixture of compound 6 (0.23
mmol), benzohydrazides 7.1 to 7.10 (0.23 mmol), respectively
was refluxed in ethanol for 1 h. The precipitated solids obtained
were filtered and washed with pet-ether and dried at the pump
to obtain hydrazones 8.1-8.9 in quantitative yields.
ν
max, cm-1): 3314, 3074, 2971, 2842, 1689, 1568, 1516, 1458,
1385, 1272, 1235, 1140, 1071, 1034, 998, 899, 853, 787, 738,
665; 1H NMR (400 MHz, CDCl3): δ 9.84 (s,1 H), 7.86 (d, J =
1.6 Hz, 1H), 7.43 (d, J = 2.0 Hz, 1H), 4.28 (t, J = 4.4 Hz, 2H),
3.91 (t, J = 4.4 Hz, 2H), 3.90 (s, 3H), 2.70 (brs, 1H); EI-MS:
m/z, 278 [M+1].
(E)-N’-[4-{2-(4-Fluorophenylthio)ethoxy}-3-cyano-5-
methoxybenzylidene]benzohydrazide (8.1): Off white solid;
Yield: 86 %; m.p.: 111-112 °C; IR (KBr, νmax, cm-1): 3276,
3224, 3066, 2963, 2844, 2233, 1653, 1599, 1557, 1485, 1419,
1381, 1296, 1220, 1164, 1070, 1001, 962, 895, 865, 823,
1
2-(4-Formyl-2-iodo-6-methoxyphenoxy)ethyl methane-
sulfonate (4): To a solution of compound 3 (4 g, 12.42 mmol)
in cyclopentyl methyl ether (20 mL) was added triethyl amine
(2 mL, 14.90 mmol) followed by methane sulphonyl chloride
(1 mL, 13.04 mmol) and stirred at room temperature for 2 h.
After completion of the reaction (checked byTLC), the reaction
mixture was diluted with water and washed with brine solution,
dried on sodium sulphate, filtered and concentrated to obtain
compound 4. Pale yellow viscous liquid; Yield: 4.5 g, 90 %;
IR (KBr, νmax, cm-1): 3074, 2969, 2878, 1738, 1686, 1562,
1455, 1387, 1339, 1271, 1222, 1168, 1139, 1108, 1040, 977,
923, 893, 862, 786, 730, 659; 1H NMR (400 MHz, CDCl3): δ
9.84 (s, 1H), 7.86 (d, J = 1.6 Hz, 1H), 7.43 (d, J = 2.0 Hz,
1H), 4.62-4.60 (m, 2H), 4.40-4.38 (m, 2H), 3.93 (s, 3H), 3.13
(s, 3H); EI-MS: m/z, 401 [M+1].
744, 697, 660, 626; H NMR (400 MHz, DMSO-d6) δ 12.0
(s, 1H), 8.42 (s, 1H), 7.92 (d, J = 7.2 Hz, 2H), 7.70 (s, 1H),
7.62 (d, J = 6.8 Hz, 2H), 7.60 (d, J = 7.2 Hz, 2H), 7.45 (t,
J = 8.0 Hz, 2H), 7.20 (d, J = 8.4 Hz, 2H), 4.32 (t, J = 6.8 Hz,
2H), 3.88 (s, 3H), 3.30 (t, J = 6.8 Hz, 2H); ESI-MS: m/z, 450
(M+1).
(E)-N’-[4-{2-(4-Fluorophenylthio)ethoxy}-3-cyano-5-
methoxybenzylidene]-4-hydroxybenzohydrazide (8.2):
White solid;Yield: 80 %; m.p.: 99-100 °C; IR (KBr, νmax, cm-1):
3320, 3081, 2945, 2803, 2238, 1641, 1602, 1566, 1481, 1451,
1376, 1323, 1270, 1228, 1170, 1150, 1109, 1073, 995, 939,
891, 841, 756, 624; 1H NMR (400 MHz, DMSO-d6) δ 11.80
(s, 1H), 10.15 (s, 1H), 8.39 (s, 1H), 7.80 (d, J = 8.4 Hz, 2H),
7.66 (s, 1H), 7.59 (s, 1H), 7.45 (dd, J = 5.2, 8.4 Hz, 2H), 7.20
(t, J = 9.2 Hz, 2H), 6.86 (d, J = 8.4 Hz, 2H), 4.31 (t, J = 6.8
Hz, 2H), 3.88 (s, 3H), 3.30 (t, J = 6.8 Hz, 2H); ESI-MS: m/z,
464.0 (M-1).
4-[2-(4-Fluorophenylthio)ethoxy]-3-iodo-5-methoxy-
benzaldehyde (5): To a solution of compound 4 (2 g, 10 mmol)
in DMF (15 mL), cooled to 5 °C was added sodium methoxide
(0.65 g, 12 mmol) followed by a pre-mixed solution of p-fluoro-
thiophenol (1.28 g, 10 mmol) in DMF (5 mL) for 30 min and
stirred at room temperature for 5 h. The reaction mixture was
quenched with water and extracted with cyclopentyl methyl
ether. The organic layer was washed with water (20 mL), brine
solution and dried over sodium sulphate, filtered and concen-
trated to obtain compound 5. Yellow solid;Yield 1.72 g, 80 %;
m.p.: 92-94 °C; IR (KBr, νmax, cm-1): 3073, 2985, 2848, 1724,
1696, 1582, 1485, 1460, 1414, 1386, 1271, 1220, 1137, 1090,
(E)-N’-[4-{2-(4-Fluorophenylthio)ethoxy}-3-cyano-5-
methoxybenzylidene]-3,4,5-trimethoxybenzohydrazide
(8.3): Brown solid; Yield: 85 %; m.p.: 122-123 °C; IR (KBr,
ν
max, cm-1): 3314, 3079, 2943, 2841, 2235, 1669, 1580, 1545,
1492, 1416, 1373, 1324, 1293, 1221, 1179, 1123, 1081, 999,
957, 869, 831, 745, 697, 663; 1H NMR (400 MHz, DMSO-d6)
δ 11.88 (s, 1H), 7.68 (s, 1H), 7.62 (s, 1H), 7.45 (t, J = 8.0 Hz,
2H), 7.23 (s, 2H), 7.19 (d, J = 8.0 Hz, 2H), 4.32 (t, J = 6.0 Hz,
2H), 3.88 (s, 3H), 3.86 (s, 3H), 3.73 (s, 3H), 3.31 (t, J = 6.0
Hz, 2H); ESI-MS: m/z, 540.0 (M+1).
1
1038, 977, 853, 823, 742, 664, 619; H NMR (400 MHz,
(E)-N’-[4-{2-(4-Fluorophenylthio)ethoxy}-3-cyano-5-
methoxybenzylidene}-4-(methylsulfonyl)benzohydrazide
(8.4): Pale yellow solid; Yield: 80 %; m.p.: 106-108 °C; IR
(KBr, νmax, cm-1): 3275, 3068, 2974, 2232, 1661, 1612, 1578,
1543, 1483, 1456, 1416, 1382, 1288, 123, 1148, 1083, 1006,
CDCl3): δ 9.82 (s, 1H), 7.84 (d, J = 1.2 Hz, 1H), 7.38 (d, J =
2.0 Hz, 1H), 7.42 (t, J = 9.2 Hz, 2H), 7.01 (t, J = 8.4 Hz, 2H),
4.21 (t, J = 7.6 Hz, 2H), 3.85 (s, 3H), 3.31 (t, J = 7.6 Hz, 2H);
EI-MS: m/z, 432 [M+1].
1
2-[2-(4-Fluorophenylthio)ethoxy]-5-formyl-3-methoxy-
benzonitrile (6): To a solution of compound 5 (1.5 g, 3.48
mmol) in dimethyl formamide (10 mL) was added cuprous
cyanide (0.38 g, 4.18 mmol) and heated to 130-135 °C for
3 h. The reaction mixture was cooled to room temperature
and diluted with diethyl ether (50 mL) followed by water (100
mL). The organic layer was washed with water (2 × 25 mL)
followed by brine solution, dried over Na2SO4, filtered and
concentrated to afford compound 5 as pale yellow solid.Yield
94 %; m.p.: 148-150 °C; IR (KBr, νmax, cm-1): 3069, 2954,
2842, 2232, 1731, 1697, 1579, 1486, 1428, 1387, 1332, 1296,
1224, 1142, 1076, 1042, 1011, 966, 924, 870, 811, 751, 699,
631; 1H NMR (400 MHz, CDCl3): δ 9.88 (s, 1H), 7.63 (d, J =
1.2 Hz, 1H), 7.59 (d, J = 2.0 Hz, 1H), 7.42 (t, J = 9.2 Hz, 2H),
959, 895, 858, 828, 779, 746, 707, 651, 623; H NMR (400
MHz, DMSO-d6) δ 12.24 (s, 1H), 8.42 (s, 1H), 8.15 (d, J =
8.4 Hz, 2H), 8.10 (d, J = 8.4 Hz, 2H), 7.70 (s, 1H), 7.66 (s,
1H), 7.45 (t, J = 8.8 Hz, 3H), 7.20 (t, J = 9.2 Hz, 2H), 4.32 (t,
J = 6.8 Hz, 2H), 3.88 (s, 3H), 3.30 (t, J = 6.8 Hz, 2H); ESI-
MS: m/z, 526.0 (M+1).
(E)-N’-[4-{2-(4-Fluorophenylthio)ethoxy}-3-cyano-5-
methoxybenzylidene]-3-nitrobenzohydrazide (8.5): Yellow
1
solid; Yield: 86 %; m.p.: 78-80 °C; H NMR (400 MHz,
DMSO-d6) δ 12.33 (s, 1H), 8.75 (s, 1H), 8.47 (s, 1H), 8.44 (s,
1H), 8.38 (d, J = 7.2 Hz, 1H), 7.85 (t, J = 8.0 Hz, 1H), 7.71 (s,
1H), 7.66 (s, 1H), 7.46 (t, J = 8.8 Hz, 2H), 7.20 (t, J = 7.6 Hz,
2H), 4.33 (t, J = 6.8 Hz, 2H), 3.89 (s, 3H), 3.30 (t, J = 6.8 Hz,
2H); ESI-MS: m/z, 493.0 (M-1).

1586 Dommati et al.
Asian J. Chem.
(E)-N’-[4-{2-(4-Fluorophenylthio)ethoxy}-3-cyano-5-
methoxybenzylidene]-2,5-dichlorobenzohydrazide (8.6):
White solid;Yield: 84 %; m.p.: 78-80 °C; IR (KBr, νmax, cm-1):
3176, 2996, 2851, 2234, 1742, 1653, 1567, 1426, 1419, 1373,
1292, 1223, 1164, 1072, 1002, 967, 924, 877, 825, 785, 745,
bacteria (Escherichia coli, MTCC 2692 and Pseudomonas
aeruginosa, MTCC 2453) using disc diffusion sensitivity test
[19,20]. Mueller-Hinton agar media were sterilized (15 min
at 121 °C) and poured into the plates to a uniform depth of 5
mm and allow it to solidify. The microbial suspension (1.2 ×
108 CFU/mL) (0.5 McFarland Nephelometery Standards) was
streaked over the surface of media using a sterile cotton swab
(15 min at 180 °C) to ensure confluent growth of the organisms.
The tested compounds 8.1-8.10 were dissolved in DMSO at
200 µg mL-1 concentration. The discs measuring 6.25 mm in
diameter (Whatman no. 1 filter paper) were impregnated with
prepared solution of compounds (8.1-8.10) by 1 mL of the
chemical solution which was added to each bottle contained
12 discs and placed on Muller-Hinton agar media previously
inoculated with bacterial suspension. The inhibition zones as
a criterion for anti-microbial activity were measured in milli-
meter at the end of an incubation period of 24 h at 37 °C. The
results of these evaluations are given in Table-1. Streptomycin
was chosen as a standard drug at a concentration of 10 µg mL-1.
1
697, 661, 625; H NMR (400 MHz, DMSO-d6) δ 12.31 (*
12.15, s, 1H), 8.22 (* 8.0, s, 1H), 7.73 (* 7.70, s, 1H), 7.64-
7.55 (m, 3H), 7.47-7.40 (m, 2H), 7.34 (* 7.27, s, 1H), 7.22-
7.15 (m, 2H), 4.32 (* 4.25, t, J = 6.8 Hz, 2H), 3.88 (* 3.66, s,
3H), 3.33 (* 3.25, t, J = 6.8 Hz, 2H); ESI-MS: m/z, 518.0
(M-1).
(E)-N’-[4-{2-(4-Fluorophenylthio)ethoxy}-3-cyano-5-
methoxybenzylidene]-3,5-dichlorobenzohydrazide (8.7):
White solid;Yield: 82 %; m.p.: 78-80 °C; IR (KBr, νmax, cm-1):
3326, 3081, 2965, 2851, 2904, 2232, 2087, 1676, 1603, 1553,
1487, 1459, 1418, 1368, 1301, 1249, 1184, 1117, 1080, 997,
1
935, 865, 808, 744, 697, 662, 621; H NMR (400 MHz,
DMSO-d6) δ 12.16 (s, 1H), 8.38 (s, 1H), 7.93 (d, J = 1.2 Hz,
2H), 7.90 (s, 1H), 7.68 (s, 1H), 7.65 (s, 1H), 7.45 (dd, J = 4.8,
8.4 Hz, 2H), 7.20 (t, J = 8.4 Hz, 2H), 4.32 (t, J = 6.0 Hz, 2H),
3.88 (s, 3H), 3.30 (t, J = 6.0 Hz, 2H); ESI-MS: m/z, 516.0
(M+1).
TABLE-1
ANTIBACTERIAL ACTIVITY OF INTERMEDIATES
AND COMPOUNDS 8.1- 8.10
(E)-N’-[4-{2-(4-Fluorophenylthio)ethoxy}-3-cyano-5-
methoxybenzylidene]-4-chlorobenzohydrazide (8.8): Pale
Zone of inhibition (mm)
Gram negative bacteria
Gram positive bacteria
yellow solid; Yield: 84 %; m.p.: 131-132 °C; IR (KBr, νmax
,
cm-1): 3223, 3069, 2955, 2888, 2843, 2237, 1653, 1597, 1551,
1484, 1417, 1377, 1298, 1220, 1168, 1068, 1004, 959, 894,
837, 754, 670, 625; 1H NMR (400 MHz, DMSO-d6) δ 12.09
(s, 1H), 8.41 (s, 1H), 7.95 (d, J = 8.0 Hz, 2H), 7.68 (s, 1H),
7.62 (d, J = 8.4 Hz, 3H), 7.45 (t, J = 8.0 Hz, 2H), 7.20 (t, J =
8.0 Hz, 2H), 4.32 (t, J = 6.0 Hz, 2H), 3.88 (s, 3H), 3.31 (t, J =
6.0 Hz, 2H); ESI-MS: m/z, 484.0 (M+1).
Compd. No.
6
13
11
10
–
11
21
20
18
7
11
21
19
18
–
8.1
8.2
8.3
8.4
1
8
6
5
–
(E)-N’-[4-{2-(4-Fluorophenylthio)ethoxy}-3-cyano-5-
methoxybenzylidene]-2,5-difluorobenzohydrazide (8.9):
White solid; Yield: 86 %; m.p.: 88-89 °C; 3262, 3071, 2947,
2231, 1653, 1581, 1549, 1485, 1417, 1369, 1286, 1225, 1188,
1159, 1069, 1003, 962, 903, 853, 819, 782, 752, 699, 662,
625; 1H NMR (400 MHz, DMSO-d6) δ 12.28 (* 12.10, s, 1H),
8.28 (* 8.02, s, 1H), 7.69 (* 7.64, s, 1H), 7.54 (* 7.44, s, 1H),
7.45-7.41 (m, 4H), 7.37 (* 7.33, s, 1H), 7.20 (t, J = 9.2 Hz,
2H), 4.32 (* 4.26, t, J = 6.4 Hz, 2H), 3.88 (* 3.69, s, 3H), 3.30
(* 3.26, t, J = 6.4 Hz, 2H); ESI-MS: m/z, 486.0 (M+1).
(E)-N’-[4-{2-(4-Fluorophenylthio)ethoxy}-3-cyano-5-
methoxybenzylidene]-4-methoxybenzohydrazide (8.10):
8.5
–
–
5
–
8.6
–
4
–
1
5
4
–
–
8.7
8.8
4
4
10
15
14
24
16
15
25
8.9
8
8
15
8.10
aStreptomycin
aConcentration: 10 µg mL–1
RESULTS AND DISCUSSION
The hydrazone derivatives 8.1 to 8.10 were prepared in
six steps from commercially available vanillin as starting
material (Scheme-I). Iodination of vanillin was carried out at
room temperature in presence of benzyltrimethylammonium
perchloroiodate and CaCO3 to afford 5-iodo vanillin in 90 %
yield. This method is superior over the recently reported
literature method [21].Alkylation of 5-iodovanillin in presence
of 1-bromoethanol gave 4-(2-hydroxyethoxy)-3-iodo-5-
methoxybenzaldehyde 3 in 85 % yield. Reaction of alcohol 3
with methanesulphonyl chloride followed by alkylation with
p-fluorothiophenol in presence of sodium methoxide gave
4-(2-(4-fluorophenylthio)ethoxy)-3-iodo-5-methoxybenzal-
dehyde 5 in 80 % yield. Reaction of iodide 5 with cuprous
cyanide in DMF at 130-135 °C resulted in 2-(2-(4-fluoro-
phenylthio)ethoxy)-5-formyl-3-methoxybenzonitrile 6 in 94 %
White solid; Yield: 80 %; m.p.: 117-118 °C; IR (KBr, νmax
,
cm-1): 2232 (–C≡N str),1740 (C=O str), 1645 (CONH), 1604
(C=N str), 1576 (NH bending), 1486, 146, 1415, 1371, 1295,
1253, 1225, 1176, 1114, 1074, 1030, 995, 950, 903, 833, 756,
1
707, 622; H NMR (400 MHz, DMSO-d6) δ 11.90 (s, 1H),
8.41 (s, 1H), 7.92 (d, J = 8.0 Hz, 2H), 7.67 (s, 1H), 7.60 (s,
1H), 7.45 (t, J = 8.0 Hz, 2H), 7.20 (t, J = 8.0 Hz, 2H), 7.07 (d,
J = 8.0 Hz, 2H), 4.30 (t, J = 6.0 Hz, 2H), 3.88 (s, 3H), 3.84 (s,
3H), 3.30 (t, J = 6.0 Hz, 2H); ESI-MS: m/z, 484.0 (M+1).
Antibacterial bioassay: The in vitro antibacterial activity
of the newly synthesized compounds (8.1 to 8.10) were screened
for the antibacterial activity against several pathogenic
representative Gram-positive bacteria (Staphylococcus aureus,
MTCC 902 and Bacillus subtilis, MTCC 441); Gram-negative

Vol. 28, No. 7 (2016)
Synthesis and Antibacterial Activity of Substituted benzohydrazide Derivatives 1587
OH
OMs
O
OH
OH
O
MeO
I
MeO
MeO
I
MeO
I
a
b
c
d
CHO
CHO
CHO
CHO
4
O
3
2
1
NH2
N
H
S
R
S
O
O
7.1 - 7.9
MeO
I
MeO
CN
d
F
e
F
f
CHO
CHO
5
6
S
O
MeO
CN
F
8.1. R = H
8.2. R = OH
8.3. R = 3,4,5-OMe
8.4. R = SO2Me
8.5. R = 3-NO2
8.6. R = 2,5-Cl
8.7. R = 3,5-Cl
8.8. R = 4-Cl
N
HN
O
8.9. R = 2,5-F
8.10. R = 4-OMe
R
Reaction conditions: a) Benzyltrimethylammonium dichloroiodate, CaCO3, cyclopentylmethyl ether, room temperature, 10 h; b) 1-bromoethanol,
K2CO3, cyclopentylmethyl ether, reflux, 4 h; c) methanesulphonyl chloride, triethyl amine, cyclopentyl methyl ether, room temperature, 2 h; d) p-
fluorothiophenol, NaOMe, DMF, room temperature, 5 h; e) CuI, DMF, 130-135 °C, 3 h; f) Benzohydrazides 7.1-7.10, ethanol, reflux, 1 h
Scheme-I: Synthesis of hydrazone derivatives 8.1 to 8.10
yield [22,23]. Condensation of aldehyde 6 with substituted
benzohydrazides 7.1-7.10 resulted in the formation of (E)-
N’-[4-{2-(4-fluorophenylthio)-ethoxy}-3-cyano-5-methoxy-
benzylidene]benzohydrazide derivatives 8.1 to 8.10. The
structural confirmations of all the newly synthesized hydrazone
It is noteworthy to mention that hydrazones such as 8.6
(R = 2,5-dichloro) and 8.9 (R = 2,5-difluoro) showed duplication
of NMR signals [24-27] and is attributed to the presence of
mixture of anti- and syn-periplanar conformers. The possibility
of conformers arises from the increase in rotational barrier
due to the decoplanarization of the aromatic ring and carbonyl
group (induced by ortho substituent) and electron withdrawing
nature of aromatic ring [26]. Ratio of signal integration of
1
derivatives were confirmed by H NMR, mass and IR data.
The molecular weight of all the synthesized intermediates and
the final compounds is in agreement with the desired molecular
formula and also, the IR spectral data has confirmed the
presence of the expected functional groups. Furthermore, the
1H NMR spectral data is in accordance with the desired
structure. For example, 1H NMR determination of (E)-N’-(4-
(2-(4-fluorophenylthio)ethoxy)-3-cyano-5-methoxybenzyli-
dene)-3,4,5-trimethoxybenzohydrazide (8.3) is described here,
the protons resonating at 11.88 ppm, 8.44 ppm corresponds
to –CONH, –CH=N- groups and the protons resonating at 7.68,
7.62 and 7.23 ppm is assigned for the benzonitrile ring and
3,45-trimethoxy phenyl ring. The para-fluorothiophenol ring
protons resonated at 7.45 and 7.19 ppm as doublets, the methylene
protons resonated 4.32 and 3.31 ppm as triplets and the methoxy-
lated protons resonated at 3.88, 3.86 and 3.73 ppm, thus confir-
ming the structure of the hydrazone compound 8.3.
1
duplicate peaks of certain proton in H NMR spectra of N-
acylhydrazones gives the information about the fraction of
each conformer in the mixture of hydrazones.
Antibacterial activity: From Table-1, as it can be put forth
from the data, the hydrazone compounds bearing R = 4-OH (8.2),
3,4,5-OMe (8.3) and 4-SO2Me (8.4) substituents has shown the
good antibacterial sensitivity, compounds (8.9) and (8.10) with
substituents 2,5-difluoro and 4-OMe, respectively exhibited the
moderate while the remaining compounds in the series showed
either nil activity or weak activity. The good activity can be
ascribed to the presence of groups 4-OH, 4-SO2Me and 3,4,5-
OMe which are directly attached to the phenyl ring of the
hydrazone moiety.All the other compounds were found to weak
to moderate activities against the tested organisms.

1588 Dommati et al.
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(2012).
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Chem. Pharm. Bull. (Tokyo), 60, 1046 (2012).
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Conclusion
In conclusion, we have prepared some new hydrazone
derivatives 8.1 to 8.10 from vanillin as the starting material in
seven steps with good yields. The synthesized hydrazones (at
200 µg mL-1) were further screened against Gram-positive
bacteria (Staphylococcus aureus, MTCC 902 and Bacillus
subtilis, MTCC 441); Gram-negative bacteria (Escherichia
coli, MTCC 2692 and Pseudomonas aeruginosa, MTCC 2453)
using disc diffusion sensitivity. The antibacterial activity data
revealed that, the hydrazone compounds bearing R = 4-OH
(8.2), 3,4,5-OMe (8.3) and 4-SO2Me (8.4) substituents has
shown the good antibacterial sensitivity, compounds (8.9) and
(8.10) with substituents 2,5-difluoro and 4-OMe, respectively
exhibited the moderate while the remaining compounds in the
series showed either no activity or weak activity.
21. Ch. Krishna Prasad and P.V.S Machi Raju, J. Applicable Chem., 3,
1460 (2014).
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