Synthesis and Antimicrobial Activity of Azetidin-2-One Fused 2-Chloro-3-Formyl Quinoline Derivatives

Introduction

Substituted quinolines are very simply, efficiently and conveniently synthesized in less time and high yield with less amount of raw material under mild condition with the help of Vilsmeier-Haack reagent (DMF+POCl₃) and substituted acetanilide. Quinoline has been posssess a wide spectrum of biological activities.Now a days quinoline derivatives are used for a convenient starting material of various further substituted quinoline.

Formylation of heterocyclic compounds¹, may be achieved by heating heterocyclic compound with Vilsmeier reagent i.e (DMF+POCl₃) phosphorous oxychloride and dimethyl formamide, the intermediate is hydrolysed in the presence of mild base give 2-(ortho)-substituted heterocyclic compound². This reaction is known as Vilsmeier-Haack reaction. The treatment of infectious diseases still remains an important and challenging problem. The search of novel antimicrobial agents is a field of current and growing interest. Many compounds have been synthesized with this aim; their clinical use has been limited by their relatively high risk of toxicity, bacterial resistance and/or pharmacokinetic deficiencies^3-4. According to the literature, pyrazoloquinoline and triazolo-thiadiazole quinoline derivatives are reported to possess various biological activities such as antibacterial⁵, antifungal⁶ anti-inflammatory⁷. As a part of our continuing interest, we have investigated for the first time cyclic azetidin-2-one fused 2-chloro-3-formyl quinoline derivatives with an aryl hydrazine group.

Methods and Materials

All chemicals were used of analytical grade from Chemdyes Corporation (Chemco) limited. All melting points were taken in open capillaries tube and are an correct. The progress of all reaction of the synthesized compound was monitored by TLC i.e (Thin layer chromatography). TLC was run using silica gel PF_{254, 366} as an adsorbent and ethyl acetate – n-hexane in different ratio as eluent. Spot were visualized using solid fumes, by keeping of TLC plate in iodine chamber.

Reaction

 

 

 

Experimental Procedure for

IR spectra were recorded on a FT-IR (Bruker) spectrophotometer, ¹HNMR Bruker Avance II 400 MHz instrument using DMSO as solvent and TMS as internal reference (Chemical shift in δ, ppm). The following abbreviations were used to indicate the position of functional groups in term of stretching and bending (FT-IR), peak multiplicity s-singlet, d-doublet, t-triplet, q-quartet, m-multiplet, dd-doublet of doublet (¹HNMR).

Step I  Preparation of ortho substituted acetanilide^{8, 9}

Aniline (5 ml) is dissolved in hydrochloric acid (4.6 ml concentrated hydrochloric acid and 12.5ml water) in a beaker. To the clear solution are added acetic anhydride (6.5 ml).The mixture is stirred until acetic anhydride has completely reacted. The mixture are immediately poured in to a solution of sodium acetate (8.3 gm) in water (25 ml).The solution is stirred and cooled in ice. The separated acetanilide is filtered. It is recrystallized from boiling water (100-125 ml) to which ethyl alcohol has been added (Table 1).

Step II  Preparation of 2-chloro-3-formyl-quinoline CFQ ^{8, 9}

To a solution of acetanilide (N-phenylacetamide) (5 mmoles) in dry DMF (15 mmoles) at 0-5^oC POcl₃ (60 mmoles) was added dropwise

with stirring and the mixture was then stirred at 80 – 100^oC for time ranging between 4-16 hr. The mixture was poured on to crush ice, stirred for 5 minutes and the resulting solid filtered, washed well with water and dried. The compounds were recrystallized from ethyl acetate. Phosphoryl chloride (commonly called phosphorus oxychloride) is a colorless liquid with the formula POCl₃. It hydrolyses in moist air to phosphoric acid to release choking fumes of hydrogen chloride. It is manufactured industrially on a large scale from phosphorus trichloride and oxygen or phosphorus pentoxide. It is mainly used to make phospha (Table 1).

Step III Preparation of 2-chloro-8-methoxy-3-(2, 4-dinitro/4-nitro phenylhydrazono) methyl) quinoline (4b2-4g2 and 4 b3-4 g3)

To a DMF solution of 2-chloro-8-methoxyquinoline-3-carbaldehyde 6 mmoles were added aryl hydrazine (phenyl hydrazine 11 mmoles) and refluxed for three hours, and then left to cool to room temperature or the solvent was removed and the separated solid was poured in to the water. The precipitated product was filtered, washed well with water and dried (Table 1).

Step IV Preparation of 3-chloro–4-(2-chloro–8-methoxyquinolin–3-yl) – 1- (2, 4-dinitro/4-nitro phenylamino)–azetidin–2-one (AZT b2-AZTg2 and AZT b3-AZT g3)

The compound 2-chloro-8-methoxy-3-((2, 4-dinitro/4-nitro phenylhydrazono) methyl) quinoline step-III b1 (0.01 mol) was dissolved in DMF (40ml) and triethylamine (0.02 mol) was added to it. Chloroacetyl chloride (0.02 mol) was added dropwise a period of 30 minutes. The reaction mixture was refluxed for 5 hr, and filtered to separate the solid formed. The filtrate was poured on to crushed ice, the product was filtered and recrystallized from ethylacetate (Table 1).

Characterization data of the synthesized compound^10-11

Acetanilide

FT-IR cm^-1 3295 (N-H), 1664 (CO), 1584 (C=C), ¹HNMR (400 MHz, DMSO), δ; 8.72 (s, 1H, NH), 2.1 (s, 3H, CH₃), 7.2 (d, 1H, Ar-H).

2-Chloro-3-formyl quinoline (CFQ)

FT-IR cm^-1 2896.53 (C – H Str,Ar) 1684.39 (C=O Str) 1574.14 (C=N Str) 1455.03 (C = C Str) 1367.35 (C – N Str,Ar) 749.25 (C – Cl Bending) ¹HNMR (400 MHz, DMSO), δ; 10.5 (s, 1H, CHO), 8.8 (s, 1H, H-4), 8.1 (m, 1H, H-6), 7.7 (m, 1H, H-7)

3-chloro–4-(2-chloro–8/7/6-methoxyquinolin–3-yl)-1-(2, 4-dinitro phenylamino) – azetidin –  2 –one (AZT b2, AZT c2, AZT d2)

FT-IR cm^-1 2998.1(C-H Ar), 3449.10 (N-H Str), 1682.51 (C=O Str), 1139.46 C – N (Str Ar), 758.25 (C – Cl Bending). ¹HNMR (400 MHz, DMSO), δ; 12.10 (s, NH) 9.21 (s, 1H, CHO) 7.98 (s, 1H, C4-H) 7.67 (m,CH-5) 3.83 (s, CH₃).

3-chloro–4-(2-chloro–8/7/6-methoxyquinolin–3-yl)-1-(4-nitro phenylamino) – azetidin – 2 – one (AZT b3, AZT c3, AZT d3)

FT-IR cm^-1 3262.86 (N– H Str, Ar) 1696.94 (C=O Str) 1566.45 (C=N Str) 1592.64 (N-H bending in amide) 1052.68 (CH₃O Str). ¹HNMR (400 MHz, DMSO), δ; 7.82 – 8.01 (m, Ar-H) 10.37 (s, 1H, CH heteroaromatic proton) 8.43 (s, 1H, H-4) 7.79 (d, C=O) 4.1 (d, 1H CH-Cl ) 3.35 (s, 3H, OCH₃ ) 7.32 (d, 1H, H-5).

3-chloro-4-(2,8/7/6-dichloroquinolin-3-yl)-1-(2, 4-dinitro phenylamino) azetidin-2-one (AZT e2, AZT f2, AZT g2)

FT-IR cm^-1 3487.00 (C – H Str, Ar)  3306.34 (N-H Str) 1748.36 (C=O Str) 1519.21 (C = N Str) 1335.03 (C – N Str, Ar) 1060.31 (CH₃O, Str) 794.11 (C – Cl, Str) 722.06 (C – Cl Bending). ¹HNMR (400 MHz, DMSO), δ; 7.31 – 8.17 (m,Ar-H) 10.16 (s, 1H, CH Heteroaromatic proton) 8.78 (s, 1H, H-4) 8.34 (m, 1H, H-8) 7.28 (C=O group d, 1H) 3.17 (m, CH-N aromatic)

3-chloro-4-(2, 8/7/6-dichloroquinolin-3-yl)-1-(4-nitro phenylamino) azetidin-2-one (AZT e3, AZT f3, AZT g3)

FT-IR cm^-1 3362.55 (C – H Str, Ar) 1681.83 (C=O Str) 1531.60 (C = N Str) 1418.67 (C – N Str, Ar) 776.88 (C – Cl, Bending).¹HNMR (400 MHz, DMSO), δ; 7.40 – 8.01 (m,Ar-H)  10.24 (s, 1H, CH Heteroaromatic proton) 8.03 (s, 1H, H-4) 7.50 (m, 1H, H-7) 6.58 (C=O, d, 1H).

Table 1: Physical data of synthesized compounds

S. No.	Code	Molecular formula	Molecular Weight (gm)	Melting point	Percentage yield	Rf value (Ethylacetate: n-hexane)
1.	CFQ	C10H6NOCl	191.616	144-146oC	79	0.67
2.	AZT b2	C19H13Cl2N5O6	478.690	264-267oC	74	0.76
3.	AZT b3	C19H14Cl2N4O4	434.231	210-214oC	55	0.65
4.	AZT c2	C19H13Cl2N5O6	478.690	228-235oC	68	0.69
5.	AZT c3	C19H14Cl2N4O4	434.231	186-189oC	61	0.89
6.	AZT d2	C19H13Cl2N5O6	478.690	219-225oC	81	0.58
7.	AZT d3	C19H14Cl2N4O4	434.231	164-167oC	74	0.68
8	AZT e2	C18H10Cl3N5O5	482.321	211-214oC	80	0.89
9	AZT e3	C18H11Cl3N4O3	436.542	189-192oC	89	0.75
10	AZT f2	C18H10Cl3N5O5	482.321	196-198oC	84	0.72
11	AZT f3	C18H11Cl3N4O3	436.542	167-169oC	64	0.61
12	AZT g2	C18H10Cl3N5O5	482.321	187-192oC	56	0.97
13	AZT g3	C18H11Cl3N4O3	436.542	156-162oC	92	0.79

 

Antimicrobial activity^12-18

The compounds AZT b2 – AZT g3 were tested for their antibacterial activity and antifungal activity by filter paper disc method using nutrient broth medium (contained g/L: beef extract 30gm; Casein hydrolysate 17.5 gm; soluble starch 1.5gm; pH 7.4). The Gram-positive and Gram-negative bacteria utilized in this study consisted of Staphylococcus aureus, Escherichia coli and fungi Candida albicans. In the filter paper disc method, sterile paper discs (05mm) impregnated with compound dissolved in DMF (Dimethyl formamide) at concentration 200µg/mL were used. Then, the paper disc impregnated with the solution of the compound tested was placed on the surface of the media inoculated with the microorganism. The plates were incubated at 37^oC for sufficient period of time. After incubation were noted and the results are given in Table 2.

 

Table 2: Antimicrobial activities of Compounds AZT b2-AZT g3 (Diameter of the zone of inhibition in mm)

Compound	Antibacterial activity		Antifungal activity
	Staphylococcus aureus (MTCC96)	Escherichia coli (MTCC722)	Candida albicans (MTCC183)
AZT b2	11	9	10
AZT b3	14	13	8
AZT c2	13	14	11
AZT c3	15	13	9
AZT d2	11	8	9
AZT d3	14	14	12
AZT e2	13	13	10
AZT e3	15	12	9
AZT f2	11	6	7
AZT f3	14	13	11
AZT g2	13	14	8
AZT g3	15	12	10
Standard	18	18	13
*Control	0	0	0

* The solvent (control) is Dimethy formamide

1. Staphylococcus aureus reference compound Amikacin

2. Escherichia coli reference compound Amikacin

3. Candida albicans reference compound Ketoconazole

Results and Discussion

All the synthesized compounds were confirmed by their spectral data (Table 1) and the screened for anti-bacterial against Staphylococcus aureus, Escherichia coli and ant-fungal activity against Candida albicans, compounds (AZT b2-AZT g2) showed moderate to good antibacterial and antfungal activity (Table 2) when compared to that of reference Amikacin and Ketoconazole respectively. The structures of all compounds were confirmed by FT-IR and ¹H NMR spectra (2.3 sections). The FT-IR spectra of the azetidine fused 2-chloro-3-formyl quinoline derivatives AZT b2 –AZT g2 showed absorption bands at about 1748-1708 cm^-1 characteristic for C=O stretching vibration, 1528-1519 cm^-1  for C=N Stretching  associated  with quinoline 2927 cm^-1  for C-H aromatic stretching, 759 cm^-1 absorption for C-Cl stretching, absorption band at 3306.34 cm^-1 for N-N=C vibration provided confirmatory evidence for ring closure. Further support was obtained from the ¹HNMR spectra, resonance assigned 10.6 δ (s, 1H, CHO), 8.5 δ (s,1H, H-4), 2.6 δ (s, 3H, CH₃) for 6-methyl/7-methyl/8-methyl (2.8 δ, s,3H), 4.0 δ (s, 3H, OCH₃) for 6-methoxy/7-methoxy/8-methoxy, 10.7 (s, 1H, CHO), 8.5 (s, 1H, H-4), 7.7 (m, 1H, H-5), 7.5 (s, 1H, H-8), 7.2( m, 1H, H-6), 10.8 (s, 1H, CHO), 8.6 (s, 1H, H-4), 8.1 (m, 1H, H-8), 7.7 (m, 1H, H-7), 7.6 (s, 1H, H-5) for the confirmation of the compounds. Having obtained chloro and formyl group substituted quinolines the possible transformations of these functionalities could afford the new quinolines (AZT b2-AZT g2), which are equally important synthon for the synthesis of fused quinoline systems.

Acknowledgements

The authors are grateful to the LNCP, Bhopal for providing the necessary facilities to carry out this research work, and also thankful to the SAIF Lab, Panjab university, Chandigarh for recording the spectral data of the compounds.

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