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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
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
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
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.