Microwave Assisted Synthesis Of Novel 2-Pyrazolines From Furan Based Chalcones and Study their Antimicrobial Actvity

Introduction

The Pyrazolines are important heterocyclic compounds containing two adjacent nitrogen atom in five membered heterocyclic ring with one endocyclic double bond on 1,2 position.  It has been found that various Pyrazoline derivative reported various potential biological activities such asantimicrobial, antioxidant, anticancer, antitumor, antitubercular, antidepressant,activities.Pyrazolines containing different heteroaromatic substituenthave showeda broad spectrum of biological activities and thus highly useful for preparation of new pharmacophore agents having improvedbiological activity. Pyrazoline and heterocyclic moiety such as Furan, Thiophene, Pyridine, quinoline, indole possess important and domineering bioactivities, which condense them useful biomolecules in drug research.

Medicinal Chemist have carried out considerable research for synthesis of novel antimicrobial agents carrying pyrazoline and heterocyclic moiety. Bio steric replacement approach was used for designing the compounds. The bio steric replacement of benzene with heteroaromatic ring resulted different microbial agents having the same biological activity.Heteroaromatic ring such as Furan, Thiophene, pyridine, quinoline, indole used as ring equivalents to benzene in drug research. Various researchers have synthesized and evaluated the pyrazoline derivativescarrying Pyrazoline and heterocyclic moiety.

Many heterocyclic chalcone derivatives were synthesized for biological studies [1-4]. Different 1,3,5-trisubstitutedpyrazoline derivativeswereshowedsensible antibacterial and antifungal activity [5]. It was found that different nitrofuryl pyrazoline derivatives were found to possess antibacterial activity[6]. Some of nitrofuryl containing pyrazolines are used in preserving fish sausages but due to toxicity, nitrofuryl pyrazolines derivatives, has been discouraged[7].To reduce toxicity arylfurans introduce in place of Nitrofuran [8].It was foundFuran derivatives are known to be associated with multiple biological activities [9–11]. Keeping these observations for preparation of  novel N-bridged heterocyclic compounds [12-15], different substituted Furan Pyrazoline hybrid compounds carryingfuran and Pyrazoline in single molecule were synthesized and studied their antimicrobial activity.

 Materials and methods

Chemicals required for preparation are of analytical grade and purchased from Merck Private limited, Mumbai. The melting point were uncorrected and determined by open capillaries,using Thiels tube. TLC paper (Merck grade) were used to monitor the progress of reaction.FTIR spectra obtained from IR Spectrometer by using KBr pelletstechniques. The IR   frequencies are expressed in cm⁻¹.The 1HNMR spectra of the compounds were obtained from 500 MHz spectrophotometer using Tetramethyl silane as an internal standard and DMSO as a solvent.

Synthetic Method for preparation of chalcone derivarives from 2-Acetyl Furan :

A mixture of 2-Acetyl Furan (0.01mol) and appropriate aldehydes (0.01mol) was dissolved in minimum quantity of alcohol. Heat the reaction mixture at about 60⁰C and then add 40 % NaOH slowly with constant stirring about 45 minutes.Keep the mixture overnight and then pour in to ice cold water and if necessarythen acidify with dil. HCl,the solid chalcone obtained. Filter it and recrystallized by ethyl alcohol. Determine its Melting point.TLC used to check the purity of each synthesized using n-Hexane and Ethyl acetate (6:4) as a solvent system.

Microwave assisted synthesis of 3(furan-2-yl)-5-Phynyl-2-Pyrazoline derivatives(Fig.1)

A mixture of Chalcone (0.01mol) and Hydrazine hydrate (0.02 mol) in ethanol(20 ml) was irradiated under Microwave oven at 600 watt 2-4 minutes. Cool the mixture and pour in crushed ice, the solid obtained. Determine its Melting Point.TLC used to check the purity of each synthesized using n-Hexane and Ethyl acetate (6:4) as a solvent system.

Figure 1: Scheme for synthesis of 3(furan-2-yl)-5-Phynyl-2-Pyrazolines Click here to View figure

Detection Method

All synthesized pyrazolines (2i-2p) were detected by their Physical data and Spectral analysis as shown below.

3(Furan-2-yl)-5-(4-Chloro phenyl)-2-Pyrazoline (2i)

Molecular Formula C₁₃H₁₁N₂OCl, Molecular weight 246.5, % Yield =85, M.P. = 135⁰C FT-IR (KBrdisc): 3331 (Pyrazoline N-H); 3080 (Aromatic C–H), 1640 (C=N), 1250 (C–N), 1620 (C=C), 750 (C–Cl), 1HNMR: 3.29 (dd,1H,CH2(Pyraz)), 5.17 (dd,1H, CHPyraz), 6.44(d,1H, CH_furyl) _,  7.45-8.00 (dd,4H, Ar-H), 10,2(s,1H,N-H)

3(Furan-2-yl)-5-(4-Bromo phenyl)-2-Pyrazoline (2k)

Molecular FormulaC₁₃H₁₁N₂OBr, Molecular weight 291g, % Yield =90 , M.P. = 170⁰C FT-IR (KBrdisc):3320 (Pyrazoline N-H), 1593(ring C=N),1564(ring C=C), 1483(ring N-N), 1126(C-N), 1063(C-O-C), 803(C-Br),¹H-NMR: 3.28 (dd,1H,CH2(Pyraz)), 5.16 (dd,1H, CHPyraz), 6.43(d,1H, CH_furyl) _,  7.40-8.00 (dd,4H, Ar-H), 10.3(s,1H,N-H)

3(Furan-2-yl)-5-(4-Fluoro phenyl)-2-Pyrazoline (2l)

Molecular FormulaC₁₃H₁₁N₂OF, Molecular weight 229, % Yield =80, M.P. = 200⁰C FT-IR (KBrdisc): 3307 (Pyrazoline N-H),) 1590(ring C=N),1563(ring C=C), 1480(ring N-N), 1122(C-N), 1065(C-O-C), 1110(C-F),¹H-NMR: 3.23 (dd,1H,CH2(Pyraz)), 5.15 (dd,1H, CHPyraz), 6.37(d,1H, CH_furyl) _,  7.45-8.00 (dd,4H, Ar-H), 10,2(s,1H,N-H)

3(Furan-2-yl)-5-(4-methoxy phenyl)-2-Pyrazoline (2m)

Molecular Formula C₁₄H₁₄O₂N₂, Molecular weight 242, % Yield =140, M.P. = 140⁰C FT-IR (KBrdisc): 3315 (Pyrazoline N-H), 1595(ring C=N),1566(ring C=C), 1487(ring N-N), 1125(C-N), 1067(C-O-C), 1158(C-O),¹H-NMR:3.46 (dd,1H,CH2(Pyraz)), 3.67(s,3H, OCH₃) 5.17 (dd,1H , CHPyraz), 6.24(d,1H, CH_furyl) _,  7.50-8.00 (dd,4H, Ar-H), 10,2(s,1H,N-H),

3(Furan-2-yl)-5-(4-ethoxy phenyl)-2-Pyrazoline (2n)

Molecular Formula C₁₅H₁₆O₂N₂, Molecular weight 256, % Yield =78, M.P. = 160⁰C FT-IR (KBrdisc): 3315 (Pyrazoline N-H), 1595(ring C=N),1566(ring C=C), 1487(ring N-N), 1125(C-N), 1067(C-O-C), 1158(C-O) ¹H-NMR: 3.25 (dd,1H,CH₂(Pyraz)), 3.65(s,3H, OCH₃) 5.17 (dd,1H, CH Pyraz), 6.40(d,1H, CH_furyl)  7.56-8.00 (dd,4H, Ar-H), 10,2(s,1H,N-H),

3(Furan-2-yl)-5-(4-Nitro phenyl)-2-Pyrazoline (2o)

Molecular Formula C13H11N3O3, Molecular weight 257, % Yield =90, M.P. = 240⁰C, FT-IR (KBr disc): 3315 (Pyrazoline N-H), 1595(ring C=N),1566(ring C=C), 1487(ring N-N), 1125(C-N), 1067(C-O-C), 1158(C-O),1H-NMR 2.74 (dd, 1H,CH), 3.30(dd, 1H, CH), 3.75 (s, 3H, OCH₃), 4.80 (t, 1H, CH Ar), 6.85 (d, 1H, CH furyl), 7.05 (m, 7H, Ar), 10.5 (s, 1H, N-H).

3(Furan-2-yl)-5-(4-methyl phenyl)-2-Pyrazoline (2p)

Molecular Formula C₁₄H₁₄N₂O, Molecular weight 226, % Yield =79, M.P. = 210⁰C FT-IR (KBr disc): 3312 (Pyrazoline N-H), 1594(ring C=N), 1543(ring C=C), 1480(ring N-N), 1122(C-N), 1065(C-O-C), 1150(C-O),¹H-NMR: 3.40 (dd,1H, CH2 (Pyraz)), 3.80(s,3H, OCH₃) 5.18 (dd,1H, CH Pyraz), 6.53 (d,1H, CH _furyl) _,  7.83 (dd,4H, Ar-H), 10.3(s, 1H, N-H).

Results

As per standard procedure the agar medium and peptone water was prepared. Test solution was prepared in DMSO. Cup Plate Method using Muller-Hinton agar medium was employed to study the preliminary Antibacterial activity of compound(2i-2p) against Staphylococcus aureus, Streptococcus faecalis, E. coli, P. fluorescenes screened by Cup plate method using Muller-Hinton agar medium.  OFLOXACIN (10mg) was employed as a reference standard drug to compare antibacterial activity of synthesized comounds. The pH of all the test solutions and control was kept at 2-3 by using Conc. HCl.

Antifungal activity of compound (2i-2p) against Trichophyton rubrum and Candida albicans screened by Cup plate method using PDA (Potato-Dextrose-Agar) medium. As per standard procedure nutrient broth, subculture, base layer medium and PDA medium was prepared. Test solution was prepared in DMSO.  OFLOXACIN (10mg) was employed as a reference standard drug to compare antifungal activity of synthesized comounds. The pH of all the test solutions and control was kept 2-3 by using Conc. HCl.

 In the petri dishes, the test solution of compound, control and reference standards were added separately and subsequently incubated at 37⁰C for 24 hours for antibacterial activity and kept aside at room temperature for 48 hr for antifungal activity. Zone of inhibition produced by each compound was measured in mm and the results are presented in Table 1 for antibacterial activity and Table 2 for antifungal activity.

Table 1: Antibacterial Activity of 2-Pyrazoline (2i-2p)

Sr. No.	Compound	Zone of inhibition in mm
		S. aureus	S. faecalis	E. coli	P. fluorescenes
1	2i	20	16	23	18
2	2k	Resistance	Resistance	Resistance	Resistance
3	2l	14	Resistance	18	Resistance
4	2m	20	13	Resistance	14
5	2n	18	12	Resistance	13
6	2o	Resistance	Resistance	Resistance	Resistance
7	2p	Resistance	Resistance	Resistance	Resistance
8	Control DMSO	—	—	—	—
9	Reference OFlOXACIN	20	10	10	12

 

Table 2: Antifungal Activity of 2-Pyrazoline (2i-2p).

Sr. No.	Compound	Zone of inhibition in mm
		Trichophyton rubrum	Candida albicans
1	2i	20	14
2	2k	Resistance	12
3	2l	Resistance	12
4	2m	Resistance	13
5	2n	Resistance	12
6	2o	Resistance	Resistance
7	2p	Resistance	Resistance
8	Control DMSO	10 mm	8
9	Reference OFlOXACIN	14 mm	—

 

Discussion

The compound (2i-2p) synthesized were screened for their antibacterial (Table 1) and antifungal activity (Table 2). Table 1 showed 2i was found to be resistance against highly sensitive against Staphylococcus aureus, highly sensitive against Streptococcus faecalis, resistance against E. coli and highly sensitive against Pseudomonas fluorescens. Compound 2k was found to be highly sensitive against Staphylococcus aureus, Streptococcus faecalis, Pseudomonas fluorescens and resistance against E. coli. Compound 2l was found to be resistance against Staphylococcus aureus, Streptococcus faecalis and highly sensitive against E. coli and Pseudomonas fluorescens. Compound 2m was found to be highly sensitive against Staphylococcus aureus, E. coli and resistance against Streptococcus faecalis, Pseudomonas fluorescens. Compound 2n was found to be resistance against Staphylococcus aureus, E. coliand highly sensitive against Streptococcus faecalis, Pseudomonas fluorescens. Compound 2o was found to be resistance against Staphylococcus aureus, Streptococcus faecalisand highly sensitive against E.coli , Pseudomonas fluorescens. Compound 2p was found to be highly sensitive against Staphylococcus aureus and moderately sensitive against Pseudomonas fluorescens, resistance against Streptococcus faecalis, E. coli.

 Acknowledgement

The authors are grateful to the Principal, Shri Shivaji Science & Arts College, Amravati, Maharashtra, India for providing FTIR. The authors are grateful to The Director, SAIF, Punjab University, Chandigarh, India for providing ¹HNMR spectra. The authors are also grateful to Dr. S.R. Gulhane, Director, Samruddhi Microbiology Diagnostic lab., Amravati for providing Antimicrobial analysis data.

Conflict of Interest

There is no conflict of interest.

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