21

SYNTHESIS OF CHALCONES AND DERIVATIVES

VENOTHINI APPU

UNIVERSITI TEKNOLOGI MALAYSIA

24

SYNTHESIS OF CHALCONES AND DERIVATIVES

VENOTHINI APPU

A project report submitted in partial fulfilment of the

requirements for the award of the degree of

Master of Science (Chemistry)

Faculty of Science

Universiti Teknologi Malaysia

APRIL 2010

iii

“To my beloved dad, mum, brother and Vishnu.....”

iv

ACKNOWLEDGEMENTS

First of all, I would like to convey my utmost gratefulness and appreciation

to my supervisor, P.M. Dr. Farediah Ahmad, for her generosity, support,

encouragement, guidance and patience towards the success of completion of my

research project work. Furthermore, I would like to express my heartfelt gratitude to

the postgraduate students of organic chemistry laboratory namely Athirah, Tarmizi,

Nuzul Hakimi, Nadya, Leila, Syafina and Saidaah for their willingness to share

useful knowledge and discussion about the topic and always there to give me a hand

whenever needed.

My greatest thankfulness to the staffs of Nuclear Magnetic Resonance

(NMR) namely, Encik Azmi and Pn Mek Zum for their cooperation and allowing me

to get access to the NMR facility.

Grateful acknowledgements are to Prof. Dr. Hasnah M. Sirat and Dr.

Shajarahtunnur Jamil for their advices and ideas.

Lastly, I also appreciate my friends especially Leelavathy Pulakrishnan,

Mina Neshati and others for their assistance during my project even though they

were busy with their own one. I hope that my project report will be a good guidance

and reference for upcoming students to do their research regarding on this topic.

Finally, thank you to those being with me during this project and who I

never mention their name before. Thank you.

v

ABSTRACT

In the present study, we undertook the total synthesis of several chalcones

and derivatives namely chalcone, 2’-hydroxychalcone, 2’,4-dihydroxychalcone, 2’-

hydroxy -3,4-dimethoxychalcone, 1,3-diphenylprop-2-en-1-ol, 2,3-dibromochalcone,

1-(1,3-diphenylallylidene)-1-phenylhidrazine, 3-hydroxy-2-phenyl-4-chromen-4-one

and 2-phenylchromen-4-one. These target compounds were synthesized via Claisen-

Schmidt condensation of the respective ketones and benzaldehydes under basic

condition to give the corresponding chalcone, 2’-hydroxychalcone, and 2’-hydroxy -

3,4-dimethoxychalcone. At the same time, 2’,4-dihydroxychalcone was synthesized

by Boron-trifluoride etherate method. 2’-Hydroxychalcone was converted to flavone

by treatment with iodine in dimethylsulfoxide and to 3-hydroxy-2-phenyl-4-

chromen-4-one by treating with hydrogen peroxide and NaOH. 1,3-Diphenylprop-2-

en-1-ol was synthesized from chalcone through reduction process using NaBH4

while 1-(1,3-diphenylallylidene)-1-phenylhidrazine was prepared from chalcone and

phenylhydrazine in ethanol. Structures were confirmed spectroscopically by IR,

NMR (1H and 13C), DEPT and GC-MS. The antibacterial and toxicity activities of

the synthesized compounds were evaluated by disc diffusion method and brine

shrimps lethality test, respectively. All the synthesized compounds were inactive

towards the tested bacteria. Chalcone and 2’-hydroxychalcone were found to be the

most toxic compounds against brine shrimp (Artemia salina) both with LD50 1.7

ppm.

vi

ABSTRAK

Dalam kajian ini, kalkon dan beberapa terbitannya iaitu kalkon, 2’-

hidroksikalkon, 2’,4-dihidroksikalkon, 2’-hidroksi -3,4-dimetoksikalkon, 1,3-

difenilprop-2-en-1-ol, 2,3-dibromokalkon, 1-(1,3-difenilalliliden)-1-fenil-hidrazin, 2-

fenilkromen-4-on dan 3-hidroksi-2-fenil-4-kromen-4-on telah disintesis. Sebatian

kalkon yang disintesis melalui tindak balas kondensasi Claisen-Schmidt adalah

kalkon, 2’-hidroksikalkon, dan 2’-hidroksi-3,4-dimetoksikalkon. Manakala 2’,4-

dihidroksikalkon dihasilkan melalui kaedah Boron-trifluorid etherat. 2’-

Hidroksikalkon telah diubah secara kimia kepada 2-fenilkromen-4-on melalui

tindakbalas dengan iodin dalam dimetilsulfoksida. Manakala, 3-hidroksi-2-fenil-4-

kromen-4-on dihasilkan melalui tindakbalas antara hidrogen peroksida dan NaOH

dengan 2’-hidroksikalkon. 1,3-Difenilprop-2-en-1-ol telah disintesis daripada kalkon

melalui kaedah penurunan menggunakan NaBH4 manakala 1-(1,3-difenilalliliden)-1-

fenilhidrazin dihasilkan melalui tindakbalas antara kalkon dan fenil hidrazin dalam

etanol. Struktur semua sebatian dikenalpasti secara spektroskopi menggunakan IR,

RMN (1H dan 13C), DEPT dan KGSJ. Aktiviti antibakteria dan ketoksikan bagi

semua kalkon dan terbitannya telah dijalankan dengan kaedah pembauran cakera

serta ketoksikan ke atas anak udang. Semua sebatian yang disintesis didapati tidak

aktif terhadap semua bakteria yang diuji. Kalkon dan 2’-hidroksikalkon merupakan

sebatian yang paling toksik terhadap anak udang (Artemia salina) dengan nilai LD50

1.7 ppm.

vii

TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION OF THE STATUS OF

THESIS

SUPERVISOR’S DECLARATION

TITLE PAGE i

DECLARATION OF ORIGINALITY AND

EXCLUSIVENESS ii

DEDICATION iii

ACKNOWLEDGEMENTS iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES xii

LIST OF SCHEMES xiii

LIST OF FIGURES xv

LIST OF ABBREVATIONS xvi

LIST OF APPENDICES xviii

viii

1 INTRODUCTION 1

1.1 Background of Study 1

1.2 Classification of Flavonoids 2

1.3 Chalcones as Drugs 4

1.4 Problem Statement 4

1.5 Objectives of Study 5

1.6 Scope of Study 5

1.7 Significance of Study 5

2 LITERATURE REVIEW 6

2.1 Biosynthesis of Chalcones 6

2.2 Naturally Occurring Chalcones 7

2.3 Synthetic Chalcones 12

2.3.1 The Claisen-Schmidt Reaction 12

2.3.2 The Allan-Robinson Condensation 13

2.3.3 Synthesis of Chalcones

via Suzuki Coupling Reaction 13

2.3.4 Synthesis of Chalcone by using BF3-Et2O 14

2.3.5 Synthesis of Chalcones via Microwave

Irradiation 15

2.3.6 The Von-Konstanecki Method 16

2.3.7 Ganguly’s Synthesis of Flavone 17

2.3.8 Friedel-Crafts Acylation 18

3 RESULTS AND DISCUSSION 20

3.1 Synthesis of Chalcones and Derivatives 20

3.1.1 Synthesis of Chalcones (6) 20

3.1.2 Synthesis of 2’-Hydroxy-

ix

chalcone (31) 23

3.1.3 Synthesis of 2’-Hydroxy

3,4-dimethoxychalcone (63) 24

3.1.4 Synthesis of 2’,4-Dihydroxy-

chalcone (65) 25

3.1.5 Synthesis of 2,3-Dibromo-

1,3-diphenylpropan-1-one (66) 28

3.1.6 Synthesis of 1,3-Diphenylprop

-2-en-1-ol (67) 30

3.1.7 Synthesis of 1-(1,3-Diphenyl-

allylidene)-1-phenylhydrazine (68) 32

3.1.8 Synthesis of 2-Phenylchromen

-4-one (2) 33

3.1.9 Synthesis of 3-Hydroxy-2

-phenyl-4-chromen-4-one (1) 35

3.2 Antimicrobial Screening 37

3.2.1 Disc Diffusion Susceptibility 37

3.2.2 Antimicrobial Study on

Synthesized Compounds 37

3.3 Toxicity Screening 39

3.3.1 Toxicity Test of The

Synthesized Compounds 39

4 METHODOLOGY 42

4.1 General Procedure 42

4.2 Instrumentation 42

4.3 Solvents and Chemicals 43

4.4 Synthesis of Chalcones 44

x

4.4.1 Chalcone (6) 44

4.4.2 2’-Hydroxychalcone (31) 44

4.4.3 2’-Hydroxy-3,4-dimethoxychalcone (63) 45

4.4.4 2’,4-Dihydroxychalcone (65) 46

4.5 Synthesis of Chalcone Derivatives 47

4.5.1 2,3-Dibromochalcone (66) 47

4.5.2 1,3-Diphenylprop-2-en-1-ol (67) 47

4.5.3 1-(1,3-Diphenylallylidene)-1-phenylhydrazine (68) 48

4.5.4 2-Phenylchromen-4-one (2) 48

4.5.5 3-Hydroxy-2-phenyl-4-chromen-4-one (1) 49

4.6 Antimicrobial Assay 50

4.6.1 Apparatus and Microorganism 50

4.6.2 Preparation of NutrientAgar and Broth 50

4.6.3 Culturing Microbe 50

4.6.4 Preparation of Agar Plate 51

4.6.5 Disc Diffusion Method 51

4.7 Brine Shrimp Lethality Assay 52

4.7.1 Mini Aquarium Preparation 52

4.7.2 Sample Preparation 52

4.7.3 Brine Shrimp Preparationfor Toxicity Test 52

4.7.4 Brine Shrimp Calculation 53

5 CONCLUSION 55

5.1 Conclusions 55

xi

5.2 Recommendations 56

REFERENCES 57

APPENDICES 64

xii

LIST OF TABLES

TABLE NO. TITLE PAGE

3.1 Antibacterial screening for synthesized compounds 38

3.2 The toxicity value of median effective dose (LD50)

for each of synthesized compound 40

4.1 Data of the number of dead brine shrimp larvae

(Artemia salina leach) 54

xiii

LIST OF SCHEMES

SCHEME TITLE PAGENO.

2.1 The Biosynthetic Pathway of Chalcones 7

2.2 The Claisen-Schmidt Reaction 12

2.3 The Allan-Robinson Condensation 13

2.4 Synthesis of Chalcone via SuzukiCoupling Reaction 14

2.5 Synthesis of O-acylated and N-acylatedChalcone using BF3-Et2O 15

2.6 Chalcone synthesis via microwaveIrradiation 16

2.7 The Von-Konstanecki Method 17

2.8 Ganguly’s synthesis of flavone 18

2.9 Friedel-Crafts acylation producing chalcone 19

3.1 Mechanism for Claisen-Schmidt condensationof acetophenone (62) and benzaldehyde (30) 22

3.2 Chemical equation for formation of 1-(2’-hydroxy-phenyl)-3-phenylpropenone or 2’-hydroxychalcone (31) 23

3.3 Synthesis of 2’-hydroxy -3,4-dimethoxychalcone (63) 24

3.4 Synthesis of 2’,4-dihydroxychalcone (65) 26

3.5 The mechanism of chalcone synthesis in BF3-Et2O (65) 26

3.6 The reaction for the formation of compound (66) 28

3.7 The mechanism for the formation of compound (66) 30

3.8 The mechanism for reduction of chalcone (67) 31

xiv

3.9 The mechanism for the formation of (1,3-diphenyl-allylidene) -1-phenylhydrazine (68) 32

3.10 The mechanism for the formation offlavone (2) by using iodine in DMSO 34

3.11 The mechanism for the formation of compound (1) 36

xv

LIST OF FIGURES

FIGURES TITLE PAGENO.

3.1 Disc arrangement inside a petri dish 51

xvi

LIST OF ABBREVIATIONS

br - broad13C - carbon-13

C6H12 - Hexane

CaCO3 - calcium carbonate

CC - Column Chromatography

CHCl3 - Chloroform

CH2Cl2 - dichloromethane

d - doublet

dd - doublet of doublets

DEPT - distortionless enhancement of polarization transfer

DMSO - dimethylsulfoxide

EtOAc - Ethyl Acetate

EtOH - Ethanol

FTIR - Fourier Transform Infrared Spectrometer

GCMS - Gas Chromatography- Mass Spectrometer1H - proton

HCl - hydrochloric acid

H2O2 - hydrogen peroxide

IR - Infrared

J - coupling constant

KOH - potassium hydroxide

m - multiplet

MgSO4 - magnesium sulphate

MS - Mass spectrum

MeOH - Methanol

m/z - mass-to-charge ratio

xvii

m.p - melting point

NaCl - sodium chloride

NaBH4 - sodium borohydride

NaOH - sodium hydroxide

NaOAc - sodium acetate

Na2SO4 - sodium sulphate

NMR - Nuclear Magnetic Resonance

PE - petroleum ether

ppm - part per million

Rf - Retention factor

rt - room temperature

s - singlet

t - triplet

TBATB - tetrabutylammonium tribromide

THF - tetrahydrofuran

TLC - Thin Layer Chromatography

UV - Ultraviolet

δ - chemical shift

λ - lambda

xviii

LIST OF APPENDICES

APPENDIX TITLE PAGE

1 IR spectrum for Chalcone (6) 65

2 1H NMR spectrum of Chalcone (6) 66

3 13C and DEPT spectrum of chalcones (6) 67

4 GCMS of chalcones (6) 68

5 IR spectrum of 2’hydroxychalcone (31) 69

6 1H NMR spectrum of 2’-hydroxychalcone (31) 70

6a 1H NMR expand spectrum of 2’-hydroxy-chalcone (31) 71

7 13C and DEPT spectrum of 2’-hydroxy-chalcone (31) 72

8 GCMS of 2’-hydroxychalcone (31) 73

9 IR spectrum for 3,4-dimethoxy-2’-hydroxy-chalcone (63) 74

10 1H NMR spectrum for 3,4-dimethoxy-2’-hydroxychalcone (63) 75

11 13 C and DEPT spectrum of 3,4-dimethoxy-2’-hydroxychalcone (63) 76

12 IR spectrum of 2’,4-dihydroxychalcone (65) 77

13 1H NMR spectrum of 2’,4-dihydroxychalcone (65) 78

xix

13a 1H NMR expand spectrum of 2’,4-dihydroxychalcone (65) 79

14 13C and DEPT spectrum of 2’,4-dihydroxy—chalcone (65) 80

15 IR spectrum of 2,3-dibromochalcone (66) 81

16 1H NMR spectrum for 2,3-dibromochalcone (66) 82

17 13C and DEPT spectrum of 2,3-dibromo-chalcone (66) 83

18 IR spectrum of 1,3-diphenyl-prop-2-en-1-ol (67) 84

19 1H NMR spectrum of 1,3-diphenyl-prop-2-en-1-ol (67) 85

20 IR spectrum for 1-(1,3-diphenyl-allylidene)-1-phenyl-hydrazine (68) 86

21 1H NMR spectrum for 1-(1,3-diphenyl-allylidene)-1-phenyl-hydrazine (68) 87

22 13C and DEPT spectrum of 1-(1,3-diphenyl-allylidene)-1-phenyl-hydrazine (68) 88

23 IR spectrum of flavone (2) 89

24 1H NMR spectrum for flavone (2) 90

25 13C and DEPT spectrum for flavone (2) 91

26 GCMS of flavone (2) 92

27 IR spectrum of 3-hydroxy-2-phenyl-4-chromen-4-one (1) 93

28 1H NMR spectrum for 3-hydroxy-2-phenyl-4-chromen-4-one (1) 94

xx

29 13C and DEPT spectrum of 3-hydroxy-2-phenyl-4-chromen-4-one (1) 95

30 GCMS of 3-hydroxy-2-phenyl-4-chromen-4-one (1) 96

1

CHAPTER 1

INTRODUCTION

1.1 Background of Study

Organic synthesis is one of a special branch in chemical synthesis and is

concerned with the construction of organic compounds by reactions. It is believed

to be one of the most vital in organic chemistry because the organic molecules used

to contain higher level of complexity compared to pure inorganic compounds.

Organic synthesis specifically becomes centre of attraction for many scientists

because the ability to produce beneficial products artificially for human goods. So

far, organic synthesis plays a very important role in many sectors such as

pharmaceuticals, agricultural and others.

On the other hand, development in chemical instruments becomes one of the

factors for many researches undergone their research more effectively. Advanced

technology able to produce instruments with higher accuracy with less time needed

to produce high quality products such as NMR, HPLC and others. The inventions

of such scientific instruments promote the organic synthesis sector to widen up the

study of interest. The development of science and technology offers assistance in

many fields especially in medical field. This development introduced the

importance of naturally occurring compounds in plants and researches have been

done significantly to synthesize these natural compounds artificially. In this case, it

can be concluded that organic synthesis is as highly developed, versatile and

interdisciplinary branch of complex molecules and new materials with unexpected

properties.

2

Flavonoids with 1,3-diarylpropane skeleton can be classified as an

outstanding class of naturally occurring compounds (Avila et al., 2008). Chalcones

or 1,3-diphenyl-2-propen-1-one derivatives are open chain unsaturated carbonyl

system in which two aromatic rings are joined by three carbons of having α, β-

unsaturated system (Avila et al., 2008). Chalcones can be considered as the

precursors of flavonoids and isoflavonoids (Tomar et al., 2007) and are secondary

metabolites of terrestrial plants that exhibit various biological activities (Narender

and Reddy, 2007).

1.2 Classification of Flavonoids

The flavonoids are members of a class of natural compounds that recently

has been the subject of considerable scientific and therapeutic interest. The

flavonoids are ubiquitous to green plant cells and therefore, could be expected to

participate in the photosynthetic process (Havstee, 2002). Flavonoids are

compounds found in fruits, vegetables and certain beverages (tea, coffee, beer, wine

and fruit drinks) that have diverse beneficial biochemical and antioxidant effects.

Their dietary intake is quiet high compared to other dietary antioxidants like

vitamin C and E.

Flavonoids are polyphenolic compounds and are categorized according to

chemical structure such as flavonol (1), flavone (2), flavanone (3), isoflavone (4),

catechin (5), anthocyanidin and chalcone (6) (Geissman, 1969). The flavonoids

have aroused considerable interest recently because of their potential beneficial

effects on human health.

3

O

OOH

O

O

O

O

(1) (2) (3)

O

O

O

OH

HO

OH

OHOH

O

(4) (5) (6)

These groups usually share a common chalcone (6) precursor which is the

basic skeleton, and therefore are biogenetically and structurally related. Flavonoids

cannot be produced via human body cells and thus to be taken mainly through the

daily diet (Joule, 1972). Flavonoids similar as chalcones composed of C15 of two

aromatic rings linked through three carbon bridge with a carbonyl function located

at one end of the bridge. Flavone (2) is the skeleton of a large class of flavonoids

(Geissman, 1969). The interest in biological properties of the flavonoids has

resulted intense synthetic efforts towards the synthesis of various flavonoids

(Havstee, 2002). Some of the methods which used to synthesize flavonoids are

Baker-Venkataraman, Von-Konstanecki, Allan-Robinson and others.

1.3 Chalcones as Drugs

Chalcones are popular intermediates for synthesizing various heterocyclic

compounds (Rajendra Prasad et al., 2008). The compounds with the backbone of

chalcones have been reported to possess various biological activities such as

antimicrobial, anti-inflammatory, analgesic, antiplatelet, antiulcerative,

antimalarial, anticancer, antiviral, antileishmanial, antioxidant, antitubercular,

antihyperglycemic, immunomodulatory, inhibition of chemical mediators release,

inhibition of leukotriene B4, inhibition of tyrosinases and inhibition of aldose

4

reductase activities (Rajendra Prasad et al., 2008). The presence of a reactive α,β-

unsaturated keto function in chalcones is found to be responsible for their biological

activities (Rajendra Prasad et al., 2008).

1.4 Problem Statement

There are varieties of methods available for preparation of chalcones. The

Claisen-Schmidt condensation and borontrifluoride-etherate methods were chosen

to produce chalcones using substituted aldehydes and substituted ketones. Due to

the reversible nature of Claisen-Schmidt reaction, the reactants were taken in excess

of stoichiometric proportion in order to increase the α,β-unsaturated product (Dhar

and Lal, 1958). Antimicrobial activity and toxicity test were examined to the

synthesized compound to observe the pharmacologically effects of the synthetic

compounds.

1.5 Objectives of Study

The objectives of the study are:-

i. To synthesize and characterized the chalcones and derivatives.

ii. To modify the functional groups of the selected chalcones.

iii. To screen the antimicrobial and toxicity activities of the

chalcone and derivatives

1.6 Scope of Study

The respective chalcones are synthesized by Claisen-Schmidt condensation

and BF3-Et2O catalyzed reaction. The crude products are purified by

chromatographic methods and recystallization techniques. The pure compounds are

characterized spectroscopically by NMR (1H and 13C), IR, MS and UV techniques.

5

The characterized compounds are subjected to simple chemical reactions (addition,

reduction and cyclisation) to form derivatives. The pure chalcones and derivatives

are screened for antimicrobial activity by disc diffusion method and toxicity test

using brine shrimp larvae (Artemia salina).

1.7 Significance of Study

This study will produce characterized chalcones and their derivatives. In

addition, the biological activity performed on the chalcones and derivatives will

give compounds with antibacterial and toxicity activities.