# Preparation and Antibacterial Activity of Some New 4-(2-Heterylidenehydrazinyl)-7-chloroquinoline Derivatives

Authors: Trong Duc Le; Ngoc Nam Pham; Tien Cong Nguyen
Journal: Journal of Chemistry
 (2018)

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## Abstract

N-(4-Substituted phenyl)acetamides, which were prepared from acetic anhydride andp-substituted anilines, were utilized as precursors for reactions to Vilsmeier-Haack reagent to form 6-substituted-2-chloroquinoline-3-carbaldehydes3a–c. Meanwhile, a similar reagent was applied to 1-[1-(4-substituted phenyl)ethylidene]-2-phenylhydrazines as substrates, which were synthesized from phenylhydrazine hydrochloride andp-substituted acetophenones, and 1,3-diarylpyrazole-4-carbaldehydes3d–f were observed as a result. Reactions between the aldehydes3a–f and 7-chloro-4-hydrazinylquinoline2, obtained from reaction of 4,7-dichloroquinoline1 and hydrazine hydrate, formed six new hydrazone compounds, namely, 4-{2-[(6-substituted-2-chloroquinolin-3-yl)methylidene]hydrazinyl}-7-chloroquinolines4a–c and 4-(2-{[3-(4-substituted phenyl)-1-phenyl-1H-pyrazol-4-yl]methylene}hydrazinyl)-7-chloroquinolines4d–f. The chemical structures of all synthesized compounds were elucidated by the analysis of IR, 1H, 13C-NMR, and HRMS spectral data. Additionally, all of the synthesized hydrazones were evaluated in terms of cytotoxic activity against four strains of bacteria and four strains of fungus at several concentrations of substrates. As a result, three of them,4a–c, possess the good ability as growth inhibitor ofBacillus subtilis andAspergillus niger at the concentration of 25 μg/mL and 50 μg/mL, respectively, while compound4e only shows a cytotoxic activity againstAspergillus niger at the concentration of 25 μg/mL.


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## Body

## 1. Introduction

Quinoline derivatives, which widely occur in nature, especially alkaloids, have become an important skeleton in synthetic chemistry due to their variety of applications in medicinal, bioorganic, and industrial chemistry. Some hydrazone derivatives possessing a quinoline moiety have been well known as having a broad spectrum of biological activities such as antibacterial [1], anticancer [2], antitubercular [3–5], antifungal [6], anti-inflammatory [7], antimalarial [8], and antimicrobial [9, 10]. According to Ferreira et al. [11], hydrazone derivatives, which were prepared from the reaction of 7-chloro-4-hydrazinylquinoline and heteroaromatic aldehydes, showed a good antimycobacterial activity in comparison with some drugs such as ethambutol and rifampicin. Additionally, some hydrazones being born from 2-chloroquinoline-3-carbaldehyde possessed a moderate to good antibacterial activity against both Gram-positive and Gram-negative bacteria [12].Besides, pyrazole derivatives have been of great interest in medicinal chemistry for their role as potent antiparasitic [13], antimicrobial [14], and antitumor agents [15]. (4-Chlorophenyl)-[1-(4-nitrophenyl)-3-phenylpyrazol-4-ylmethylene]amine [13] compound possesses a good activity againstL. infantum with IC50 of 12.4 µM while 5-(3-isobutyl-1-phenyl-1H-pyrazol-4-yl)-2-substituted-1,3,4-oxadiazoles [15] have an anticancer activity against breast and liver cell line with IC50 of around 2–7 µM and 4–13 µM, respectively.In this article, 7-chloro-4-hydrazinylquinoline2 was prepared from the reaction of 4,7-dichloroquinoline1 and hydrazine hydrate and then was utilized as the key intermediate material for the synthesis of some new hydrazones containing 2-chloroquinoline or pyrazole moiety. The new synthesized hydrazones including 4-{2-[(6-substituted-2-chloroquinolin-3-yl)methylidene]hydrazinyl}-7-chloroquinoline4a–c and 4-(2-{[3-(4-substituted phenyl)-1-phenyl-1H-pyrazol-4-yl]methylene}hydrazinyl)-7-chloroquinoline4d–f were evaluated for antimicrobial activities against eight kinds of microorganisms. The chemical structure of the hydrazones was elucidated by IR, NMR, and HRMS spectral analysis and their biological activities were reported for the first time.


## 2. Materials and Methods

All chemicals were purchased from Merck or Aldrich and solvents were commercial and were used without any further purification.Melting points were determined with a Gallenkamp digital Melting-point apparatus 5A-6797 and were uncorrected.The IR absorption spectra were scanned on Shimadzu FTIR 8400S spectrum using potassium bromide (KBr) pellets.All the1H, 13C-NMR, HSQC, and HMBC spectra were recorded on a Bruker Advance 500 MHz model spectrometer using DMSO-d6 as solvents and internal standard. Thespin-spincoupling constants (J) are given in Hz. Peak multiplicity is reported ass (singlet),d (doublet),dd (double-doublet),t (triplet),q (quartet),m (multiplet), andbr (broad).Mass spectrometric data were recorded on a micrOTOF-QII Bruker.Thin-layer chromatography (TLC) was performed on silica-gel sheets (silica gel 60 F254, Merck) and visualized in ultraviolet light (254 nm).The synthesis of the hydrazones containing quinoline heterocycles was performed following the steps shown in Scheme1.Scheme 1
Pathway for preparation of 4-(2-heterylidenehydrazinyl)-7-chloroquinoline derivatives.2-Chloroquinoline-3-carbaldehydes
3a–c were prepared according to the literature [16].p-Substituted aniline was added to the solution of acetic anhydride in acetic acid, following by being refluxed in 2 hours. Consequently, cooling to room temperature and pouring into ice water were performed to collectN-(4-substituted phenyl)acetamide derivatives, which then reacted to the mixture of dimethylformamide and phosphoryl chloride (Vilsmeier-Haack reagent) to form 2-chloroquinoline-3-carbaldehyde derivatives3a–c.1,3-Diarylpyrazole-4-carbaldehydes
3d–f were prepared according to the literature [17]. Phenylhydrazine hydrochloride was slowly added to the mixture of 4′-substituted acetophenones and acetic acid in ethanol. The reaction mixture was stirred and then was poured into water to separate the product 1-(1-phenylethylidene)-2-phenylhydrazine, which was treated with Vilsmeier-Haack reagent at 80–90°C in 15 hours to form 1,3-diphenylpyrazole-4-carbaldehyde derivatives3d–f.Preparation of 7-Chloro-4-hydrazinylquinoline
2. 4,7-Dichloroquinoline (10 g, 5 mmol) was dissolved in ethanol (20 mL) in which hydrazine hydrate (35 mL, 50 mmol) was slowly dropped. The reaction mixture was refluxed for 2 hours. Consequently, this mixture was cooled to room temperature and was kept overnight to separate the solid. The yellow precipitates were filtered and recrystallized from ethanol to give compound2. Yield: 80%; mp. 224-225°C (literature [1]: 223–225°C). IR (ν, cm−1): 3255, 3258 (–NH– and –NH2), 3055 (Csp2-H), 2931 (Csp3-H), 1600 (C=C) and 1566 (C=N); 1H-NMR (500 MHz, DMSO−d6) δ (ppm),J (Hz): 8.60 (1H,br, >NH), 8.39 (1H,br, Ar-H), 8.16 (1H,d,J = 9.0, Ar-H), 7.76 (1H,s, Ar-H), 7.39 (1H,dd, J1 = 9.0, J2 = 2.0, Ar-H), 6.87 (1H,br, Ar-H) and 4.45 (2H,br, –NH2); 13C-NMR (125 MHz, DMSO–d6) δ (ppm): 152.8, 151.8, 148.8, 133.2, 127.4, 123.8, 115.9 and 98.8 (S1–S3 from Supplementary materials).Preparation of 4-(2-Heterylidenehydrazinyl)-7-chloroquinoline Compounds
4a–f. Appropriate 2-chloroquinoline-3-carbaldehyde derivatives3a–c or 1,3-diphenylpyrazole-4-carbaldehyde derivatives3d–f (1 mmol) were dissolved in absolute ethanol (10 mL) with a few drops of glacial acetic acid. This mixture was stirred for 10 minutes and then compound2 (0.19 g, 1 mmol) was added in. The reaction mixture was refluxed for 3 hours. At the completion of reaction, the mixture was cooled to room temperature to separate the solid, which was filtered and recrystallized from suitable solvent to give products4a–f, respectively.All the synthesized hydrazones were evaluated to in terms of antimicrobial activities against microorganism. The method for these experiences was based on the literature [18, 19].


## 3. Result and Discussion

7-Chlorohydrazinylquinoline2 was prepared from the reaction of 4,7-dichloroquinoline1 and hydrazine hydrate. Its 1H-NMR spectrum (S2 from Supplementary materials) showed twobroad singlet signals of hydrazine group (–NHNH2) at δH 8.6 and 4.5. Additionally, there were adoubletsignal at δH 8.16 withspin-spin coupling of 9.0 Hz attributed toH5 and adouble-doublet signal at 7.39 attributed toH6. Meanwhile,H8 gave asingletsignal at δH 7.76. Two signals appearing at δH 8.39 and 6.87 were attributed toH2 andH3, respectively. Theoretically,H2 andH3 usually appear asdoublet signals due to havingspin-spin coupling together. However, in our case, the ring system may lead to them becoming hydroxylic protons, and, so, thebroad signals were obtained.Compound2 was utilized as a precursor for preparation of six new hydrazones according to Scheme 1. The reaction of 4,7-dichloroquinoline1 with hydrazine hydrate formed 7-chlorohydrazinylquinoline2, which was treated by 2-chloroquinoline-3-carbaldehyde derivatives3a–c to form 4-{2-[(6-substituted-2-chloroquinolin-3-yl)methylidene]hydrazinyl}-7-chloroquinoline compounds4a–c. Meanwhile, 4-(2-{[3-(4-substituted phenyl)-1-phenyl-1H-pyrazol-4-yl]methylene}hydrazinyl)-7-chloroquinoline compounds4d–f were produced by the reaction of compound2 and 1,3-diphenylpyrazole-4-carbaldehyde derivatives3d–f.The reaction of2 and some heteroaromatic3a–f occurred easily and may be observed clearly by both changing color of reaction solution and the appearance of precipitates in the progress of reaction.In IR spectra, the specific vibration of amino group (–NH2, double peak) at 3255–3258 cm−1 disappeared while the sharpness peak of N–H bonds still appeared around 3200 cm−1; the stretching bands of the C=N bonds were recognized at 1555–1582 cm−1. These data are similar to those of the 7-chloro-4-quinolinylhydrazone compounds described in literature [3].The physical properties and IR spectral data of the4a–f compounds were presented in Table 1.Table 1
The physical properties and IR spectral data of the4a–fcompounds.
Comp.
Structure
X or Y
Solvent recrystallized
Mp. (°C)
Yield (%)
ν (cm−1)
C–H
NH
C=CC=N
4a
H
DMF : H2O
236
83
3055
3179
16151566
4b
CH3
DMF : H2O
239
83
28953055
3179
16151566
4c
OEt
EtOH
239
81
29783040
3232
16201582
4d
H
Dioxane : H2O
236
84
3063
3256
16511582
4e
Cl
DMF : H2O
233
85
3063
3241
16131575
4f
NO2
Ac : H2O
236
83
3060
3215
16201555
More information can be found in Supplementary Materials.The structures of the hydrazones were further confirmed by the HRMS data. Molecular ion peaks in the mass spectra of the products were in conformity with desired molecular formulas of them (see Tables2 and 3).Table 2
1H, 13C-NMR, and HR-MS spectral data of compounds 4a–c.
Number
X = H (4a)
X = CH3 (4b)
X = OC2H5 (4c)
δ
H (ppm) J (Hz)
δ
C (ppm)
δ
H (ppm) J (Hz)
δ
C (ppm)
δ
H (ppm) J (Hz)
δ
C (ppm)
2
8.68 (d)J = 4.5
152.5
8.67 (d)J = 5.0
152.0
8.67 (d)J = 4.5
157.3
3
7.62 (d)J = 5.0
102.9
7.60 (d)J = 5.5
101.8
7.58 (d)J = 4.5
101.8
4
-
149.2
-
149.2
-
150.0
5
8.42 (d)J = 9.0
124.2
8.42 (d)J = 9.0
123.8
8.40 (d)J = 9.0
123.8
6
7.67 (dd)J1 = 8.5; J2 = 1.5
124.3
7.66 (dd)J1 = 9.0; J2 = 2.0
125.3
7.65 (d)J = 8.5
124.2
7
-
133.4
-
133.9
-
133.7
8
7.96 (br)
128.1
7.96 (d)J = 2.5
127.4
7.95 (br)
127.8
9
-
147.3
-
145.5
-
145.9
10
-
116.1
-
115.6
-
115.3
11
11.70 (s)
-
11.67 (s)
-
11.67 (s)
-
13
8.85 (s)
138.5
8.83 (s)
138.1
8.80 (s)
139.0
14
-
125.8
-
126.5
-
125.3
15
-
127.1
-
127.1
-
127.5
17
-
137.8
-
137.5
-
138.1
18
8.23 (d)J = 8.5
127.6
7.89 (d)J = 8.5
127.3
7.87 (d)J = 9.5
128.4
19
7.72 (t)J = 8.0
131.9
7.70 (dd)J1 = 8.5; J2 = 1.5
133.6
7.46 (dd)J1 = 9.0; J2 = 2.5
130.0
20
7.86 (t)J = 7.5
148.8
-
146.6
-
145.6
20a
-
-
2.54 (s)
21.2
4.21 (q)J = 7.0
63.7
20b
-
-
-
-
1.44 (t)J = 7.0
14.5
21
7.99 (d)J = 8.5
129.2
7.99 (s)
127.8
7.61 (s)
129.1
22
-
148.3
-
147.4
-
142.8
23
9.15 (s)
134.6
9.02 (s)
134.3
9.01 (s)
134.7
MS
367.0518 [M + H]+ (C19H13Cl2N4 + H, 367.0512)
381.0674 [M + H]+ (C20H15Cl2N4 + H, 381.0668)
411.0775 [M + H]+ (C21H17Cl2N4O + H, 411.0774)
More information can be found in Supplementary Materials.Table 3
1H, 13C-NMR, and HR-MS spectral data of compounds 4d–f.
Number
Y = H (4d)
Y = Cl (4e)
Y = NO2 (4f)
δ
H (ppm) J (Hz)
δ
C (ppm)
δ
H (ppm) J (Hz)
δ
C (ppm)
δ
H (ppm) J (Hz)
δ
C (ppm)
2
8.56 (d)J = 5.0
152.0
8.48 (br)
152.3
8.49 (br)
152.7
3
7.51–7.58 (m)
101.2
7.31 (br)
101.8
7.28 (br)
102.2
4
-
149.2
-
149.2
-
147.2
5
8.33 (d)J = 9.0
123.9
8.36 (d)J = 9.0
123.0
8.34 (d)J = 9.0
123.4
6
7.51–7.58 (m)
124.8
7.60 (br)
125.1
7.58 (br)
124.8
7
-
131.6
-
131.2
-
131.2
8
7.90 (s)
128.6
7.84 (br)
128.0
7.84 (br)
128.6
9
-
147.0
-
146.5
-
146.6
10
-
115.4
-
115.0
-
115.0
11
11.11 (s)
-
11.33 (br)
-
11.26 (br)
-
13
8.51 (s)
136.4
8.54 (s)
139.0
8.57 (s)
138.9
14
-
117.5
-
117.5
-
117.8
15
9.11 (s)
127.7
9.14 (s)
128.7
9.17 (s)
127.4
18
-
151.3
-
150.0
-
148.8
19
-
133.8
-
133.9
-
133.6
20, 24
7.79 (d)J = 8.0
128.5
7.64 (d)J = 8.5
128.7
8.14 (d)J = 8.5
123.9
21, 23
7.51–7.58 (m)
129.7
7.85 (d)J = 8.5
129.6
8.42 (d)J = 8.5
129.7
22
7.37–7.41 (m)
132.4
-
133.4
-
132.8
25
-
139.1
-
139.7
-
139.0
26, 30
8.03 (d)J = 7.5
118.7
8.03 (d)J = 8.5
118.8
8.05 (d)J = 8.5
118.9
27, 29
7.51–7.58 (m)
128.8
7.57 (d)J = 8.5
130.2
7.60 (d)J = 8.5
129.5
28
7.37–7.41 (m)
127.2
7.41 (t)J = 8.5
127.1
7.44 (t)J = 8.5
127.4
MS
424.1347 [M + H]+ (C25H18ClN5 + H, 424.1323)
458.0946 [M+H]+ (C25H17Cl2N5 + H, 458.0934)
469.1179 [M + H]+ (C25H17ClN6O2 + H, 469.1174)
More information can be found in Supplementary Materials.Both the1H-NMR (500 MHz, DMSO-d6) and 13C-NMR (125 MHz, DMSO-d6) spectra of these compounds showed all of the signals matching with the expected structures. The 1H-NMR spectra of each of the compounds4a–f showed thesinglet signals at δH 8.51–8.83 and 11.11–11.70, which were attributed to –CH=N– (H13) and –NH– (H11), respectively. Furthermore, each of the 13C spectra presented a signal around 136−139 ppm, which made cross peak with the signal ofH13 in the HSQC spectra and so it was attributed to −CH=N− (C13). Besides,singlet signal of the methyl group in molecule of4b appeared at 2.54 ppm; the signals of the ethyl group in4c were assigned asquartet at 4.21 ppm (2H,J= 7.0 Hz) andtriplet at 1.44 ppm (3H,J = 7.0 Hz). Thesinglet at δH 9.01–9.15 in the 1H-NMR spectra of compounds4a–c was assigned to proton in the 23th position (H23) while thesinglet at δH 9.11–9.17 in the 1H-NMR spectra of compounds4d–f was assigned to proton of the pyrazole ring (H15). A complete assignment of 1H and 13C NMR spectra of the hydrazones was based on analysis of NMR and 2D spectra (the HMBC correlations of4b and4e compounds were shown in the structures at Tables 2 and 3) and is presented in Tables 2 and 3.The configuration of –CH=N– bonds of hydrazone compounds was identified by their NOESY spectral analysis. The supposal configuration of compound4d wasZ due to the correlation betweenH2 andH22/28, which was shown in its NOESY spectrum. Meanwhile, the NOESY spectrum of compound4e presented a cross peak of correlation ofH13 andH8, which confirmed theEconfiguration of this compound. There was a remark that the carbon signal of –CH=N– group inZ configuration appears at the higher magnetic field than inE configuration [20]. In our case, the same observation was collected with the carbon signal of –CH=N– group of compound4d appearing at δC 136.4 whereas the others were collected at  δC 139.0. Furthermore, the 13C-NMR spectrum of compound4f showed the signal of –CH=N– group at δC 138.9, and, thus, its configuration was supposed to beE. These data were presented in Table 3.All synthesized compounds were tested for antibacterial and antifungal activities. Four kinds of bacteria includingEscherichia coli (ATCC 25922),Pseudomonas aeruginosa(ATCC 25923),Bacillus subtilis (ATCC 11774), andStaphylococcus aureus(ATCC 11632) and four fungus involvingAspergillus niger (439),Fusarium oxysporum(M42),Candida albicans(ATCC 7754), andSaccharomyces cerevisiae(SH 20) were utilized for these experiments. The results were presented in Table 4.Table 4
Antimicrobial activity of hydrazones4a–f.
Samp.
Minimum inhibitory concentration (MIC:μg/mL)
Bacterial strains
Fungal strains
EC
PA
BS
SA
AN
FO
SC
CA
4a
(−)
(−)
25
(−)
50
(−)
(−)
(−)
4b
(−)
(−)
25
(−)
50
(−)
(−)
(−)
4c
(−)
(−)
25
(−)
50
(−)
(−)
(−)
4d
(−)
(−)
(−)
(−)
(−)
(−)
(−)
(−)
4e
(−)
(−)
(−)
(−)
(−)
(−)
(−)
(−)
4f
(−)
(−)
(−)
(−)
25
(−)
(−)
(−)
(−) means negative; EC, PA, BS, and SA stand forEscherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Staphylococcus aureus; AN, FO, SC, and CA stand for Aspergillus niger, Fusarium oxysporum, Saccharomyces cerevisiae, and Candida albicans.As the data has shown, the series of 7-chloro-4-[2-(2-chloroquinolin-3-yl-methylene)hydrazinyl]quinoline compounds4a–c possess antibacterial and antifungal activities againstBacillus subtilisat the concentration of 25 μg/mL andAspergillus niger at the concentration of 50 μg/mL, respectively.Meanwhile, in the other series, there was only 7-chloro-4-(2-((3-(4-nitrophenyl)-1-phenyl-1H-pyrazol-4-yl)methylene)hydrazinyl)quinoline4f showing the antifungal activity againstAspergillus niger at the concentration of 25 μg/mL.


## 4. Conclusion

By a simple and convenient method, 7-chloro-4-hydrazinylquinoline2 and six aldehydes including 2-chloro-6-substituted quinoline-3-carbaldehydes3a–c and 1,3-diarylpyrazole-4-carbaldehydes3d–f were prepared. The reaction of hydrazine2 with the heteroaromatic aldehydes3a–f formed six new 4-(2-heterylidenehydrazinyl)-7-chloroquinoline compounds4a–f. Their chemical structures were elucidated by the analysis of IR, NMR, and HRMS spectral data. It was found that the configuration of hydrazones wasE except(Z)-4-{2-[(1,3-diphenyl-1-phenyl-1H-pyrazol-4-yl)methylene]hydrazinyl}-7-chloroquinoline compound4d. All of them were tested for the antimicrobial activities against eight kinds of bacteria and fungus. The results showed that the hydrazones containing 2-chloroquinoline moiety4a–c possess good activities in growth inhibition ofBacillus subtilis andAspergillus niger at the concentration of 25 and 50 μg/mL, respectively. In general, the hydrazones containing 1,3-diarylpyrazole moieties4d–f had been inactive but compound4f exhibited high biological activity againstAspergillus nigerat the concentration of 25 μg/mL.



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