Synthesis and Characterisation of Substituted 2-benzofuranyl Chalcones

Available online at www.sciencedirect.com

ScienceDirect Materials Today: Proceedings 5 (2018) 16703–16715

www.materialstoday.com/proceedings

SCICON 2016

Synthesis and Characterisation of Substituted 2-benzofuranyl Chalcones a

V.Ushaa, V.Thangarajb,* Department of Chemistry, University College of Engineering Panruti, Panruti, 607106,India b

Department of Chemistry, Anna University ,BIT Campus, Tiruchirappalli,620024,India

Abstract

A series of substituted Stryl 2- benzofuranyl ketones have been synthesized by Crossed Aldol condensation of substituted benzaldehyde and 2- acetyl benzofuran using Ultrasonicator. The synthesized chalcones have been characterized by Physical constant, Mass spectra, IR, 1H NMR and 13C NMR. The spectral data are correlated with Hammett substituent constants and Swain – Lupton parameters. From the regression analysis, the effect of substituent on the group of frequencies has been predicted. The structure activity relationship (SAR) have been studied by screening of anti biological activity over a representative panel at bacterial and fungal strain using disc diffusion(zone of inhibition) method. All these synthesized chalcones exhibited significant activities against all bacterial and fungal strain. © 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Advanced Materials (SCICON ‘16). Keywords: Chalcones; Crossed Aldol condensation; IR; 1H ;13C NMR; Hammett constant; Swain-Lupton parameter; Invitro- petridish Bauer- Kirby method. * Corresponding author. Tel.: +91-978-716-9429; fax: +91-431-240-7 333. E-mail address: [email protected]

2214-7853 © 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Advanced Materials (SCICON ‘16).

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Introduction

The structure activity relationship and quantitative structure property relationships were used for finding the structure of molecule, quantitative and qualitative analysis. Spectral data of organic compounds are useful for prediction of structure, stereo chemical and physicochemical properties [1]. There is considerable information avail in literature concerning the transmission of electronic effects in molecule undergoing isomer equilibration in ground state. For example enol and enones, α, β-unsaturated ketones [2]. The 2E chalcones are α, β-unsaturated ketones possess methylene structural moieties and they belongs to biomolecules [3,4] . The C-C single bond rotation [5] of carbonyl and alkene carbons, they exist as E s-cis and s-trans and Z s-cis and Z s-trans conformers. These structural conformers of chalcones have been confirmed by NMR and IR spectroscopy. the aldol condensation is useful for the formation of carbon-carbon bonds in many kinds of carbonyl compounds [6], due to the importance of the methylene structural unit, which is found in many naturally occurring compounds, antibiotics, and the use of cyclic and acyclic ketones as precursors for the synthesis of 2-benzofuranyl derivatives [7]. Also these spectroscopic data were used for the study of structure parameter correlations in biological active molecules[8], analysis of normal coordination[9], reaction mechanism in transition states [10], qualitative and quantitative analysis [ 11, 12]. Chalcones possess multipronged activities, due to the presence of -CO-CH=CH- moiety and substituents in phenyl rings. The important biological activities of chalcones are antimicrobial [13], anti-viral [14], anti-plasmodial [15], antituberculosis [16], antioxidant [17], and insect antifeedant [18,19]. Now a day’s chemists and scientists have paid much more interest to correlate the spectral data with Hammett substituent constants for studied the effect of substituents of organic molecules [20- 23]. Within the above view there is no report available for ultrasound assisted synthesis and the study of effect of substituent on the spectral data and antimicrobial activities of substituted styryl 2-benzofuranyl ketones in literature in the past. Therefore the authors have taken effort to synthesize the 2-benzofuranyl chalcones, study the Qsar and antimicrobial activities against the zone of mm of inhibition of their bacterial and fungal strains by BauerKirby method. 2. Experimental 2.1. Materials and Methods All the Chemicals involved in the present investigation, have been procured from sigma-Aldrich and E- Merck chemical companies. Melting point of all chalcones has been determined in open glass capillaries on SUNTEX melting point apparatus and is uncorrected. Infrared spectra (KBr, 4000-400 cm-1) have been recorded on AVATAR -300 Fourier transform Spectrophotometer. The NMR spectra Were recorded in Bruker AV 500 NMR spectrometer for 1H and 13C in CDCl3 solvent Using TMS as internal standard. 2.2. Preparation of Chalcones An equimolar quantities (0.01 mmol) of substituted benzaldehydes and 2-acetyl benzofuran and 10 mL of ethanol were taken in a beaker. The reaction mixture was exposed to Ultrasonicator j5120_ 1-5 lit Model, for 10

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minutes (Scheme 1). The obtained solid product was filtered and crystallized with ethanol. Scheme 1. Synthesis of substituted styryl 2-benzofuranyl ketones.

CHO

Few drops of 2% NaOH solution

Table 1. The physical constants and spectral data of synthesized 2-benzofuranyl chalcones . Entry

X

M. F.

M.W.

Yield(%)

m.p.(ºC)

Mass(m/z)

1

H

C17H12O2

248

95

114-115

248[M+]

C17H11BrO2

327

90

123-124

2 3 4 5 6 7 8 9 10

3Br 4Br 2Cl 3Cl 4Cl 4-F 4OH 4CH3 4NO2

C17H11BrO2

327

90

123-124

C17H11ClO2

282

93

101-102

C17H11ClO2

282

91

116-117

327[M+], 329[M2+] 327[M+], 329[M2+] 282[M+], 284[M2+] 282[M+], 284[M2+] 282[M+],

C17H11ClO2

282

94

119-120

C17H11FO2

266

90

103-104

C17H12O3

264

91

121-122

264[M+]

C18H14O2

262

95

117-118

262[M+]

C17H11NO4

293

90

132-133

293[M+]

284[M2+] 266[M+], 268[M2+]

3. Resultsf and discussion In the present study the spectral linearity of synthesized chalcones has been studied by evaluating the substituent effect on C=Os-cis,

C=Os-trans,

CHop, CHip, CH=CHop and C=Cop

(cm–1). The proton chemical shift (,

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ppm) of vinyl Hα and Hβ and carbon chemical shift of CO, vinyl Cα and Cβ have been correlated with Hammett substituent constants F and R parameters using single and multi-linear regression analysis. 3.1. IR spectral study The recorded infrared C=Os-cis, C=Os-trans, CHop, CHip, CH=CHop and C=Cop stretching frequencies (cm–1) of the synthesized 2-benzofuranyl chalcones have been presented in Table 2. The carbonyl group gave two type of frequencies such as C=Os-cis, C=Os-trans and the respective conformers are shown in Fig. 1.

Fig.1 The s-cis and s-trans conformers of 2-benzofuranyl Chalcones

Entry

Table 2. The infrared stretches (ν, cm-1)of 2-benzofuranyl chalcones.

1 2 3 4 5 6 7

X

COs-cis

COs-

CHop

CHip 983.2 8 976.9 8 969.3 5 985.8 2 978.0 6 950.9 5 980.1 6 982.2 9

trans

H 3Br 4Br 2Cl 3Cl 4Cl 4-F

9

4OH 4CH

10

4NO

8

1

IR

3

2

CH=CHo

13

C=Cop

H NMR Hα Hβ

CO

C NMR Cα Cβ

516.9 6 543.1 2 549.2 3 508.5 7 541.9 8 592.6 9 541.8 8 599.3 4

7.35 7 7.76 5 7.76 5 7.29 9 7.30 1 7.28 2 7.29 9 7.32 4

7.84 5 7.83 8 7.83 8 7.53 2 7.41 6 7.72 1 7.33 6 7.42 6

179.0 1 179.3 9 179.6 5 189.1 8 179.5 6 179.3 0 179.5 4 179.0 8

123.4 6 123.6 4 123.6 8 126.4 5 123.3 7 123.4 1 123.3 6 123.4 7

139.3 7 136.7 4 136.8 7 136.4 5 139.4 6 136.4 7 136.8 2 136.3 9

p

1649.8 5 1655.3 8

1597.3 0 1600.9 0

1652.8

1608.2

1651.3 2 1651.6 2 1653.6 0 1653.2 8 1655.5 3

1594.7 1 1601.3 8 1610.4 6 1601.3 4 1602.7 5

1069.0 6 1086.6 1 1078.3 6 1065.1 1 1064.9 4 1074.4 2 1063.7 6 1067.6 5

1654.2 8

1601.4 0

1066.8 8

980.8 3

792.22

541.8 1

7.38 0

7.83 8

179.8 4

123.0 6

145.6 8

1654.5 1

1603.8 3

1070.4 4

978.5 0

742.44

581.2 3

7.29 9

7.66 8

183.3 9

123.3 7

136.0 9

792.85 782.46 765.29 796.95 774.13 740.58 724.34 764.83

These data are correlated with Hammett substituent constant F and R and Swain-Lupton’s parameters [24].

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Table3. Results of statistical analysis of IR spectral frequencies(cm-1) of 2-benzofurayl chalcones with Hammett σ, σ+, σI, σRconstants, F and R parameters. Frequency

Constant

r

νCOs-cis(cm-1)

Σ

0.801

1653.28 0.107

2.08 10

σ+

0.821

1653.36 1.102

2.01 10

σI

0.882

1652.57 1.900

2.02 10

σR

0.871

1652.95 1.701

2.05 10

F

0.831

1652.36 2.355

1.98 10

R

0.903

1652.54 2.547

1.96

Σ

0.839

1601.26 1.769

4.60 10

σ+

0.809

1601.64 0.829

4.62 10

σI

0.902

1599.84 4.702

4.49

σR

0.802

1601.07 0.605

4.64 10

F

0.921

1599.88 4.397

4.50

R

0.803

1601.42 0.561

4.64 10

Σ

0.832

1068.75 6.733

7.15 10

σ+

0.824

1069.54 3.455

7.32 10

σI

0.815

1068.75 4.435

7.47 10

σR

0.920

1071.68 9.965

7.26 10

F

0.803

1069.53 0.898

7.55 10

R

0.922

1071.35 6.105

7.36

Σ

0.919

978.41

5.917 10.81 9

σ+

0.914

977.61

1.914 10.97 9

σI

0.924

981.25 10.504 10.68 9

σR

0.806

976.81

3.354 10.99 10

F

0.815

979.88

6.935 10.88 10

R

0.811

976.34

4.464 10.95 10

Σ

0.825

771.19

νCOs-trans (cm-1)

νCHip (cm-1)

νCHop (cm-1)

I

ρ

-

s

n

8

8

8

9

27.41 10

Correlated derivatives H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 4-Br, 2-Cl, 3-Cl, 4-Cl, 4F, 4-OH, 4-CH3 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 3-Cl, 4-F, 4-OH, 4CH3, 4-NO2 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br, 3-Cl, 4-F, 4OH, 4-CH3, 4-NO2 H, 3-Br, 2-Cl, 3-Cl, 4-Cl, 4F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 4-Br, 2-Cl, 3-Cl, 4-Cl, 4F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 4-Br, 2-Cl, 3-Cl, 4-Cl, 4F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4F, 4-OH, 4-CH3, 4-NO2 H, 3-Br,4-Br, 2-Cl, 3-Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4-

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νCH=CHop (cm-1)

19.592

Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4σ 0.803 768.02 -1.623 28.91 10 Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 4-Br, 3-Cl, 4-Cl, 4-F, 422.41 8 σI 0.906 792.49 OH, 4-CH3, 4-NO2 67.581 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4σR 0.902 773.78 32.491 27.41 9 Cl, 4-F, 4-OH, 4-CH3 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4F 0.825 771.13 27.41 10 19.591 Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 2-Cl, 3-Cl, 4-Cl, 4R 0.803 768.02 -1.623 28.29 10 F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4-1 νC=Cop (cm ) Σ 0.800 551.89 0.361 34.33 10 Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4σ+ 0.903 553.79 32.71 9 19.333 Cl, 4-F, 4-OH, 4-CH3 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4σI 0.826 538.91 35.789 33.08 10 Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4σR 0.807 549.67 34.23 10 12.515 Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4F 0.827 538.20 35.963 32.92 10 Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4R 0.822 545.09 33.41 10 28.321 Cl, 4-F, 4-OH, 4-CH3, 4-NO2 r=correlation coefficient; I= intercept; ρ=slope; s=standard deviation; n=number of correlated derivatives +

The results of poor correlation are due to the conjugation between the substituent and the vinyl group in chalcones as shown inFig.2.

Fig . 2.

The resonance-conjugative structure.

Some of the single parameter correlations were failing for the infrared frequencies. When seeking these frequencies with multi-parameter correlation-Swain-Lupton’s parameters [24], they produced satisfactory correlation coefficients. The generated multi-parameter correlation equations are given in (2-13). νCOs-cis(cm-1) = 1652.33(±1.500) +1.793(±0.320)σI + 1.517(±0.390)σR

...(2)

(R= 0.927, n = 10, P > 90%) νCOs-cis(cm-1) = 1652.03(±1.379) + 1.853(±0.298)F +2.158(±0.285)R

...(3)

(R = 0.914, n = 10, P > 90%) νCOs-trans(cm-1) = 1600.02(±3.360) +4.779(±0.718)σI + 1.909(±0.874)σR (R= 0.926, n = 10, P > 90%)

...(4)

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νCOs-trans(cm-1) = 1602.94(±3.265) + 4.487(±0.707)F +0.378(±0.067)R

16709

...(5)

(R = 0.925, n = 10, P > 90%) νCHip(cm-1) = 1069.90(±5.351) +5.167(±1.167)σI + 10.479(±01.392)σR

...(6)

(R= 0.932, n = 10, P > 90%) νCHip(cm-1) = 1067.55(±5.326) + 2.421(±1.115)F +6.613(±1.100)R

...(7)

(R = 0.924, n = 10, P > 90%) νCHop(cm-1) = 980.55(±7.971) -10.817(±1.705)σI-4.475(±0.207)σR

...(8)

(R= 0.925, n = 10, P > 90%) νCHop(cm-1) = 978.94(±7.809) -7.832(±1.691)F -6.101(±1.614)R

...(9)

(R = 0.921, n = 10, P > 90%) νCH=CHop(cm-1) = 796.52(±16.298) -65.788(±14.348)σI+25.693(±4.237)σR

...(10)

(R= 0.963, n = 10, P > 95%) νCH=CHop(cm-1) = 799.98(±13.443) -77.271(±29.100)F -10.681(±2.271)R ...(11) (R = 0.975, n = 10, P > 95%) νC=Cop(cm-1) = 537.51(±24.745) +35.169(±5.213)σI+8.873(±0.412)σR

...(12)

(R= 0.927, n = 10, P > 90%) νC=Cop(cm-1) = 534.84(±23.538) +30.938(±5.071)F +21.813(±4.865)R

...(13)

(R = 0.932, n = 10, P > 90%) 3.2. 1H NMR spectral study The 1H NMR spectra of the styryl ketone derivatives under the investigation have been recorded in deuteron chloroform solution employing tetramethylsilane (TMS) as internal standard. The signals of the vinyl Hα and Hβ protons have been assigned and are presented in Table 2. The assigned vinyl Hα and Hβ protons have been correlated and the results of statistical analysis [25-30]are presented in Table 4. In single parameter correlations, some of the regression gave poor correlations. So, the author think that, it is worthwhile to seek multiple correlations involving either I and R constant (or) Swain-Luptons [24]F and R parameters. The correlation equation for vinyl proton chemical shifts (, ppm) are given in eqns. (15-18). δHα(ppm)= 7.786(±0.121) + 0.013(±0.002)σI + 0.079(±0.003)σR

...(15)

(R= 0.910, n = 10, P > 90%) δHα(ppm)= 7.388(±0.117) + 0.040(±0.002)F +0.023(±0.002)R

...(16)

(R = 0.908, n = 10, P > 90%) δHβ(ppm)= 7.876(±0.094) + 0.354(±0.002)σI + 0.694(±0.024)σR

...(17)

(R= 0.980, n = 10, P > 95%) δHβ(ppm)= 7.873(±0.094) + 0.382(±0.101)F +0.924(±0.024)R (R = 0.984, n = 10, P > 95%)

...(18)

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Table 4.Results of statistical analysis of vinyl Hα and Hβ protons of 2-benzofurayl chalcones with Hammett σ, σ+, σI, σRconstants, F and R parameters. Frequency

Constant

R

I

ρ

s

n

Correlated derivatives

δHα(ppm)

Σ

0.817

7.357

0.058

0.16

10

σ+

0.831

7.363

0.039

0.16

10

σI

0.802

7.374

0.018

0.16

10

σR

0.801

7.382

0.081

0.16

10

F

0.807

7.384

0.045

0.16

10

R

0.805

7.374

0.035

0.16

10

Σ

0.811

7.613

0.067

0.21

10

σ+

0.817

7.617

0.070

0.21

10

σI

0.904

7.770

0.401

0.18

8

σR

0.916

7.753

0.719

0.15

9

F

0.905

7.813

0.480

0.17

10

R

0.906

7.741

0.504

0.16

19

H, 3-Br, 4-Br, 2-Cl, 3Cl, 4-Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br,2-Cl, 3Cl, 4-Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br,2-Cl, 3Cl, 4-Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br,2-Cl, 3Cl, 4-Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br,2-Cl, 3Cl, 4-Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br,2-Cl, 3Cl, 4-Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br,2-Cl, 3Cl, 4-Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br,2-Cl, 3Cl, 4-Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br,3-Cl, 4Cl, 4-F, 4-OH, 4-CH3 H, 3-Br, 4-Br,2-Cl, 3Cl, 4-Cl, 4-F, 4-OH, 4-CH3 H, 3-Br, 4-Br,2-Cl, 3Cl, 4-Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br,2-Cl, 3Cl, 4-Cl, 4-F, 4-OH, 4-CH3, 4-NO2

δHβ(ppm)

r=correlation coefficient; I= intercept; ρ=slope; s=standard deviation; n=number of correlated derivatives

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3.3. 13 C NMR spectra Table 5. Results of statistical analysis of vinyl CO, C and Cof 2-benzofuranyl chalcones with Hammett σ, σ+, σI, σRconstants, F and R parameters. Frequency δC=O(ppm)

Constants Σ σ+ σI σR F R

δCα(ppm)

Σ σ+ σI σR F R

δCβ(ppm)

Σ σ+ σI σR F R

R 0.83 1 0.84 7 0.83 3 0.81 2 0.82 2 0.82 3 0.80 7 0.90 2 0.90 2 0.81 4 0.81 0 0.80 0 0.83 7 0.82 6 0.90 7 0.82 0 0.90 7 0.81 8

I 180.3 9 180.6 1 179.1 5 181.3 1 179.7 1 181.6 9 123.6 9 123.6 7 123.3 8 123.5 9 123.5 7 123.7 3 138.7 3 138.3 1 141.7 4 138.7 8 141.5 3 138.7 0

Ρ 3.180

s 3.42

n 10

3.178

3.17

10

4.791

3.39

10

2.145

3.58

10

3.000

3.52

10

3.000

3.51

10

0.221

1.09

10

0.588

1.05

8

0.957

1.07

8

0.738

1.09

10

0.420

1.09

10

0.011

1.10

10

3.446

3.06

10

1.605

3.19

10

9.384

2.14

9

3.234

3.21

10

8.821

2.33

9

2.216

3.25

10

Correlated derivatives H, 3-Br, 4-Br,2-Cl, 3-Cl, 4-Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br,2-Cl, 3-Cl, 4-Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br,2-Cl, 3-Cl, 4-Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br,2-Cl, 3-Cl, 4-Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br,2-Cl, 3-Cl, 4-Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br,2-Cl, 3-Cl, 4-Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br,2-Cl, 3-Cl, 4-Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 4-Br,2-Cl, 3-Cl, 4-Cl, 4-F, 4OH, 4-NO2 H, 4-Br,2-Cl, 3-Cl, 4-Cl, 4-F, 4-OH, 4-NO2 H, 3-Br, 4-Br,2-Cl, 3-Cl, 4-Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br,2-Cl, 3-Cl, 4-Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br,2-Cl, 3-Cl, 4-Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br,2-Cl, 3-Cl, 4-Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br,2-Cl, 3-Cl, 4-Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4-Cl, 4-F, 4-OH, 4-NO2 H, 3-Br, 4-Br,2-Cl, 3-Cl, 4-Cl, 4-F, 4-OH, 4-CH3, 4-NO2 H, 3-Br, 4-Br,2-Cl, 3-Cl, 4-Cl, 4-F, 4-OH, 4-NO2 H, 3-Br, 4-Br, 2-Cl, 3-Cl, 4-Cl, 4-F, 4-OH, 4-CH3, 4-NO2

r= correlation coefficient; I= intercept; ρ = slope; s=standard deviation; n=number of correlated derivatives (R = 0.971, n = 10, P > 95%)

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In the present study, the chemical shifts (ppm) of C=O and vinyl carbons have been assigned and are presented in Table 2. Attempts have been made to correlate these chemical shift (, ppm) with Hammett substituent constants, field and resonance parameters, with the help of single and multiple-regression analysis to study the reactivity through the effect of substituent. The chemical shift (, ppm) observed for the CO, C and C have been correlated with Hammett constants and the results of statistical analysis [25-30]are presented in Table 5. In single parameter correlations, some of the regression gave poor correlations. So, the author think that, it is worthwhile to seek multiple correlations involving either I and R constant (or) Swain-Luptons[24] F and R parameters. The correlation equation for CO, C and Ccarbon chemical shift (, ppm) are given in eqns. (19-24). δCO(ppm)= 179.59(2.509) + 4.976(±0.532)σI + 2.659(±0.652)σR

...(19)

(R= 0.937, n = 10, P > 90%) δCO(ppm)= 180.361(±0.244) + 3.887(±0.521)F +3.820(±0.504)R

...(20)

(R = 0.936, n = 10, P > 90%) δCα(ppm)= 123.28(±0.798) + 0.912(±0.172)σI + 0.644(±0.027)σR

...(21)

(R= 0.925, n = 10, P > 90%) δCα(ppm)= 123.58(±0.795) + 0.441(±0.172)F +0.104(±0.001)R

...(22)

(R = 0.910, n = 10, P > 90%) δCβ(ppm)= 142.09(±1.571) – 9.654(±3.359)σI + 2.230(±0.408)σR

...(23)

(R= 0.977, n =10, P > 95%) δCβ(ppm)= 141.59(±1.690) -8.740(±3.661)F +0.383(±0.034)R

...(24)

4. Antimicrobial activities Chalcones possess a wide range of biological activities. These multipronged activities present in different chalcones are examined against respective microbes-bacteria’s and fungi. 4.1.Antibacterial activity Antibacterial sensitivity assay was performed using Kirby-Bauer disc diffusion technique [31]. In each Petri plate about0.5mlof the test bacterial sample was spread uniformly over the Solidified Mueller Hinton agar using sterile glass spreader. Then the discs with5mm diameter made up of Whatmann No.1filterpaper, impregnated with the solution of the compound were placed on the medium using sterile forceps. The plates were incubated or 24 hours at 37°C by keeping the plates upside down to prevent the collection of water droplets over the medium. After 24hours, the plates were visually examined and the diameter values of the zone of inhibition were measured. Triplicate results were recorded by repeating the same procedure. The antibacterial activities of all the synthesized chalcones have been studied against three gram positive pathogenic strains such as M.luteus, B. substilis, S. aureusand three gram negative strains E. coli and P.

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aerogenosa. k.pneumoniae The disc diffusion technique was followed using the Kirby–Bauer method, at a concentration of 250 mg/mL with Ampicillin taken as the standard drug. The measured zone of inhibitions are shown in Table 6. Chalcones1, 2, 3, 4, 8 and 9 are active against B. substilis strain. Compounds 1 and 4-10 are shown good antibacterial activity against M. luteus. Ketones 1-5, 7 and 9 are shown antibacterial activity against S. auresstrins. The Benzfuryl chalcones 1-5 and 7-10 are active against E. coli strain. The styryl benzofurayl ketones 1, 2, 4, 6, 7, 9 and 10 shows good antibacterial activity against P. aerogenosa strain. The compounds 1-7, 9 and 10 showed good antibacterial avtivity against K. Pneumoniae. 4.2.Antifungal Activities Table 6. The antibacterial activity of mm of zone of inhibition of bacterial strains of substituted styryl 2Zone of Inhibition (mm) No.

S.NO.

Compound

benzofuranyl ketones.

Gram positive Bacteria B.sub M.luteus S.aureus tilis

Gram negative Bacteria E.coli

P.aeruginosa

k.pneumoniae

1

1

6

6

7

7

6

6

2

2

-

-

6

6

6

7

3

3

6

-

8

8

-

6

4

4

7

8

8

7

7

7

5

5

-

7

6

7

-

6

6

6

7

7

-

-

7

7

7

7

-

6

6

6

6

6

8

8

6

7

-

6

-

-

9

9

7

8

7

6

6

8

10

10

-

6

-

6

6

7

Standar

Ampicilli

d

n

8

8

9

7

8

8

Control

DMSO

-

-

-

-

-

-

Antifungal sensitivity assay was performed using Kirby-Bauer[31] disc diffusion technique. PDA medium was prepared and sterilized as above .It was poured(ear

bearing heating condition) in the Petri-plate which

was already filled with 1ml of the fungal species. The plate was rotated clockwise and counter clock-wise for uniform spreading of the species. The discs were impregnated with the test solution. The test solution was prepared by dissolving 15mg of the chalcone in1ml of DMSO solvent.

The medium was allowed to solidify

and keptfor24hours.Then the plates were visually examined and the diameter values of zone of inhibition were measured.Triplicate results were recorded by repeating the same procedure.

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Analysis of the zone of inhibition is given in Table 7. It reveals that all chalcones have shown good antifungal activities against the A. niger fungal strain except the compounds 1, 4 and 8. The compounds have good zone of inhibitions against P. scup fungal strains except, 2, 4, and 5.A good antifungal activity was observed the chalcones against T. viride. fungal strains except 3-5 and 8.

Table 7. Antifungal activities of substituted styryl 2-benzofuranyl ketones Entry

Substituent

Zone of inhibition (mm) A.niger

5.

M.species

T.viride

1

H

-

6

6

2

3-Br

6

-

6

3

4-Br

6

6

-

4

2-Cl

-

-

-

5

3-Cl

6

-

-

6

4-Cl

6

6

6

7

4-F

6

6

6

8

4-OH

-

6

-

9

4-CH3

6

6

7

10

3-NO2

6

6

6

Standard

Miconazole

9

7

9

Control

DMSO

-

-

-

CONCLUSIONS

A series of 2-benzofuranyl chalcones have been synthesized by Ultrasound irradiation method. The synthesized chalcones have been characterized by their physical constants, melting point and spectral data. The assigned spectral data are correlated with Hammett substituent constants and Swain-Lupton’s constants using single and multi-regression analysis. From the results of statistical analysis the effect of substituents on the group frequencies are predicted. The antimicrobial activities of these chalcones have been measured and almost all compounds shows good antibacterial and antifungal activities against their strains. 6. REFERENCES [1] Ranganathan K., Arulkumaran R., Kamalakkannan D., Vanangamudi G., Thirunarayanan G., IUP J. Chem. 4(2) (2011) 60-69. [2] Wang Y. H., Zou J. W., Zhang B., Lu Y. X., Jin H. X., Yu Q. S., J Mol Struct (Theochem) 755(31) (2005) 1-2. [3] Thirunarayanan G., Vanangamudi G., Subramanian M., Umadevi U., Sakthinathan, S. P., Sundararajan R., Elixir Org. Chem. 39(2011) 4643-4653. [4] Yankep E., Fomumand Z. T, Dangne E., Phytochem. 46 (1997) 59. [5] Mulliken R. S., J. Chem. Phys. 7 (1939) 121-131.

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